modification of a formula student race car engine, for addition of a continuously variable...

Modification of a Formula Student race car engine, for addition of a Continuously Variable Transmission

L. Marquenie

AES 2008.135

Master Traineeship

Coach: Dr. Ir. P.C.J.N. Rosielle Supervisor: Prof.dr.ir. M. Steinbuch

Institute: Technical University of Eindhoven Department of Mechanical Engineering Section Automotive Engineering Science

Period: Summer 2008

Traineeship Loek Marquenie University Racing Eindhoven

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Preface

During the spring of 2007 I got acquainted with University Racing Eindhoven (URE) for the first time, at the TU/e Fast event. This day they demonstrated their race car among other sports cars, and although I already heard of them, I now got a first glimpse of the team in action. Being quite impressed by the performance of the little car, especially the acceleration, I imagined myself being part of the team, and experience what it takes to have a race car built and competing with it. About one year later it was time to start with my Master traineeship, and although I was offered a handfull of projects, my decision was already made; Go to URE and ask for a 3-month traineeship assignment.

From there on an exciting period in my engineering career began, as I was witness of the final assembly of the URE04 and 3 spectacular races throughout Europe. The project that Ive been assigned to, together with Bas Verhappen, a graduating student at Fontys Automotive Engineering, was aimed at next years race car, the URE05. Nevertheless we both were involved in helping the team with the competition as well, and kept our motivation high because of this. We managed to deliver a design for part of the URE05s drivetrain (which will contain a CVT), and hope that the cars performance will benefit from our work.

During the project, I was coached by Nick Rosielle, head of the Constructions and Mechanisms Group at the TU/e. I want to thank him for his straightforward coaching and the extensive knowledge he was able to provide to us about the subject. Furthermore I want to thank Bas Verhappen for his cooperation and helpfullness, all URE members for the teamwork and fun, and last but not least, my family and friends for supporting me during this period.


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Summary

This report describes a study on the structural integration of a CVT into the driveline of the URE05 race car. The focus of the assignment is on how the CVT is to be connected to the engine and to design all the necessary engine modifications. The traineeship assignment is performed as part of the CVT project that is defined by University Racing Eindhoven. With this project the team wants to make the transition of a standard stepped gear transmission to a Continuously Varable Transmission. Several pre-studies have pointed out the increased performance a CVT can offer to a race car and therefore URE have decided to choose for this transmission concept. On the structural level of the CVT integration, there are many aspects to be concerned with, for instance keeping the added weight to a minimum. The assigment was started with an examination on all components, followed by a comparison between several drivetrain concepts. After carefull consideration a final concept has been chosen, which met all requirements. This concept consists of a transversal placement of the engine, with the CVT directly bolted onto the engine output. By placing the CVT upright, relative good packaging was achieved. The concept is further elaborated in detail, and if initial testing of the CVT shows good results, the design will be taken into production. Furthermore a new lower gearbox housing has been designed, which is specifically adapted to the use of the CVT and a dry sump lubrication system. Consequently, drivetrain centre of gravity and mass are significantly lowered by this measure.


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Contents

Preface....2

Summary........3

Contents.....4

1 Introduction.....6

1.1 About University Racing Eindhoven.......6

1.2 Project assignment (in brief)....6

1.3 Assignment description.........................7

1.4 Method of approach and project planning.........7

2 Analysis..................8

2.1 Race car overview.....8

2.2 The engine and drivetrain........9

2.3 Continuously Variable Transmission....11

3 Concept design....12

3.1 Introduction.......12

3.2 Requirements...12

3.3 Designing directions....12

3.4 Materials....12

3.5 Production methods........13

3.6 Layout options..13

3.7 Concept choice....15

3.8 Lowering the engine....18

4 Detailed design...............19

4.1 Introduction...........................19

4.2 Connection of the CVT to the engine..............19

4.3 CVT mounting...........................21

4.4 Transmission components.........22

4.5 Clutch actuation........................23

4.6 The design in 2D................24

4.7 Lubrication system...25

4.8 Lower gearbox housing......26

4.9 The design in 3D..28

5 Conclusions......29

5.1 Conclusions......29

5.2 Recommendations..........29

Bibliography.......30


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APPENDIX A - Specifications sheet URE05....................................................................................3

APPENDIX B - Layout options (top view).........................................................................................5

APPENDIX C - Pictures of final drive types......................................................................................8

APPENDIX D.1 - Concept D packaging visualization (side, top and rear view)..................................9

APPENDIX D.2 - Concept J packaging visualization (side, top and rear view).................................10

APPENDIX E - DIN5480 Calculation of Engine-CVT connector sleeve (dutch).............................11 APPENDIX F - Clutch actuation design in 3D...............................................................................13

APPENDIX G.1 - Engine Lubrication : standard wet sump scheme..................................................14

APPENDIX G.2 - Engine Lubrication : standard wet sump technical drawing...................................15


APPENDIX G.4 - Engine Lubrication : Modified dry sump scheme...................................................17

APPENDIX H - Various views of the lower gearbox housing design..............................................18


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Chapter 1

Introduction

In this chapter an overview will be given of the racing team and the project.

1.1 About University Racing Eindhoven

Founded in September 2003, University Racing Eindhoven is a group of enthusiastic students from the Technical university of Eindhoven. Each year they participate in the Formula Student Competition, in which student teams from all over the world design, build and race with a single-seater race car. The team is gaining more and more experience and their highest ranking so far is a respectable 9th place, obtained at the Ferrari test circuit in Fiorino, Italy.

1.2 Project assignment (in brief)

Modification of a Suzuki GSX-R600 K2 engine and a SECVT, in order to enable them to be fitted together. The engine / CVT combination will be used in the URE05 Formula Student race car.

Main requirements - All necessary engine functions must be preserved. Examples are lubrication systems,

mounting supports, etc. - Investigate how the engine-cvt combination can be placed in the race car, regarding a low

centre of gravity, direction of rotation of components, and other important criteria.

Fig. 1.2. The GSX-R600 K2 engine (left) and the SECVT (right).

Fig. 1.1. University Racing Eindhoven and the URE04 at Silverstone, England.


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1.3 Assignment description

With the design of the car of 2009, the URE team wants to focus on the key research areas of the Eindhoven University of Technology. One of them is the Continuous Variable Transmission (CVT). Already two studies have been done on the benefits of the application of a CVT, showing that applying one can benefit in faster lap times. New simulations agree with the previously stated conclusions of those studies. The 2008 team management has therefore decided to replace the conventional stepped gear transmission of next years race car with a CVT. The implementation of a CVT into the race cars driveline involves a lot of work on several areas, for instance component and coordinated control, as well as the structural realization. Regarding the last, the outline of this project is focused on studying the various possibilities of replacing the existing gearbox by a preselected CVT. Apart from simply integrating the CVT into the driveline, special attention must as well go to optimizing the total powertrain layout, as far as weight and centre of gravity are concerned. In concrete this means that the lowest parts of the engine are to be examined for possible redesign. The crankshaft for example is preferably placed as low as possible to the ground, as this is one of the heaviest components in the race car. In previous years the engines wet sump oil pan has already been replaced by a more flat dry sump pan. However, with an engine redesign in mind, placing the engines CoG even lower to the ground can possibly be realized to even fuller extent.

1.4 Method of approach and project planning

The project has been assigned to two persons, due to the great number of tasks that needed to be performed. Bas Verhappen, a graduating student from Fontys Highschool ( Department of Automotive Engineering) and me, the author of this document, have accepted the assignment with great motivation. The project has been divided into a couple of phases, the first one being an orientation period where we were getting to know the team and the assignment subject. After that a concept phase was gone through. This included brainstorm sessions, making use of sketches and considering different options, regarding their pros and cons. After selecting the most appropiate concept, a design freeze was introduced. This concept has been further elaborated, using 2D and 3D modeling. During the writing of this report Bas is busy with finalizing the engine-cvt design so that it can be taken into production.


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Chapter 2

Analysis

In this chapter the reader is presented a brief explanation of the main objects that are dealt with in this report, namely the race car, the engine and the CVT.

2.1 Racecar overview

The URE team of 2008 has decided to take the design of next years car to a completely new level. While in previous years the chassis consisted of a box of aluminum honeycomb panels, they now want to make the transition to a carbonfibre monocoque chassis, as well as carbonfibre rims. Meanwhile, the rear part of the car will be designed as a tubular space frame. Furthermore the standard 6-speed gearbox of the engine will be replaced by a Continuous Variable Transmission system. More extensive design specifications can be found in appendix A.

Fig. 2.1. 3D model of the URE05 race car


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2.2 The engine and drivetrain

The new race car will keep the engine that has already been used in the previous three years, namely a Suzuki GSX-R600 motorcycle engine. The main reasons for this are the high level of perfomance, and the considerable amount of knowledge that has been gathered about this engine in the past years. Also, a test rig has been adapted specifically for this engine. Several upgrading modifications have been applied, which include camshaft tuning, crankshaft balancing, an optimized intake design, and replacement of the wet sump system by a dry sump type.

The GSX-R600 is a 4-cylinder inline internal combustion engine, with 4 valves per cyclinder. Designed as a high-rev engine, its standard power-to-weight ratio has a value of approximately 1,34 kW/kg. Due to the mandatory air intake restrictor of 20mm this has decreased to about 1,0 kW/kg. The engine placement in the motorcycle, as well as in the URE race cars is transversal.

The transmission part of the engine is fairly straightforward, as it is commonly seen on sports bikes. With a primary reduction between the crankshaft and the wet-plate clutch, the high engine speeds are lowered to more acceptable values for clutch and gearbox. Since there is just a single wheel to be driven on motorcycles, the transmission is not equipped with a differential. Consequently, most Formula Student race cars have a separate differential unit installed. The total drivetrain layout of the URE04 is shown in figure 2.3. More specifications can be found in appendix A.

Fig. 2.3 Schematic presentation of the URE04 drivetrain

1. Exhaustside 2. Cylinders 3. Crankshaft 4. Primary reduction 5. Torsion dampener 6. Clutch 7. Gearbox (6-speed) 8. Chain + sprockets 9. Differential 10. Driveshafts 11. Wheels

1

11

2 3 4

10

5

6

7

8

9

Fig. 2.2. Picture of the GSX-R600 K2 engine


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Lower engine block functions

Since the main modifications to the engine will focus primarily on the lower section where power is generated and transmitted, the functions of this part will be summed up. Functions of parts like the cylinder head, valvetrain etc will be left out. Also this summary is focused on the modified dry-sump engine.

Function Performed by

1 Generating rotational power Crankshaft

2 Supporting torque reaction forces Bearings and housing

3 Supporting engine reaction forces Engine mounting supports

4 Crankshaft speed reduction 1st Reduction between crankshaft and clutch

5 Crankshaft torque multiplication 1st Reduction between crankshaft and clutch

6 Disconnecting crankshaft from drivetrain Clutch + actuation mechanism

7 Reduce torque peaks within drivetrain Torsion dampener in clutch

8 Provide variable reduction ratio's Gearpairs 1 to 6 + actuation mechanism

9 Lubrication and parts cooling Oil distribution circuit, incl. galleries and jets

10 Oil pressure Oil pressure pump + lining

11 Oil pressure regulation Oil pressure relief valve

12 Oil temperature regulation Oil/water heat exchanger

13 Oil filtering Oil filter

14 Oil accumulation within engine Drysump pan

15 Oil scavenging Scavenging pump + lines

16 Oil accumulation outside engine Swirlpot

Table. 2.1. Summary of the lower engine block functions


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2.3 Continuous Variable Transmission

Since its not preferable to design a complete CVT from scratch, an investigation [5] has been performed on various CVTs available on the market. From a number of candidates the best option has been carefully selected, which is the SECVT, also from Suzuki. This CVT is applied in their Burgman 650 motorscooter. Figure 2.4 shows a picture of the CVT, and an overview of its internal parts is given in figure 2.5. The SECVT (which stands for Suzuki Electronically-controlled Continuously Variable Transmission) is a lightweight dry CVT, with a so called hybrid belt. The fact that the belt operates in a non-oiled environment, gives it a larger coefficient of friction with the pullies, thereby greatly reducing the required clamping force. This in turn makes it possible to create a more lightweight housing structure. Also, the need for a hydraulic actuation system and pump is avoided. Instead, the pullies are actuated by an electric motor. The CVT system is cooled by a pulley driven fan, which forces air along the internal parts. Again, specifications can be found in appendix A.

During the writing of this report, the SECVT is extensively examined on a wide range of aspects. These include the constructional and electrical design. Also a test rig and measuring instrumentation are being prepared for conducting experiments on performance and control. As a result of these examinations, it already appeared that another belt had to be chosen. This is because the standard belt will not able to withstand the engine output torque. Fortunately, a relatively new and stronger dry belt has just been introduced on the market, by ContiTech (figure 2.6) This belt will therefore be acquired and installed.

Fig. 2.4. The donor SECVT

Fig. 2.5. Cross-sected 3D model of the SECVT internals

Fig. 2.6. The ContiTech Hybrid Ring


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Chapter 3

Concept design

3.1 Introduction

After having looked at the main driveline components that will be implemented in the new race cars driveline, an extensive investigation has been performed on how to connect all the different parts to each other and how to place them in the car. In abstract, the power from the crankshaft has to be transferred to the wheel driveshafts, with a CVT in between. However, on a constructive level there are many different solutions to realize this, and each option has its own specific advantages and drawbacks. Therefore its necessary to get an overview of the requirements and other things to keep in mind when heading for a solution. This will be presented in the first paragraphs of this chapter. After that, alternatives are being proposed and compared to each other. From that examination a definitive concept will be chosen, which will be further elaborated in detail.

3.2 Requirements

- The design needs to be feasible and reliable. - All necessary engine and CVT functions, like lubrication, need to be maintained. - The CVT as well as the engine need to be demountable in a short period of time, for repair or

inspection. - Speeds and torques that are applied to the CVT need to be within the required range. - Direction of rotation needs to be correct.

3.3 Designing directions

- A compact layout of the driveline, with a low weight and centre of gravity is preferrable. - Possibilty of redesign of engine housing with respect to lowering the engine CoG. - Existing driveline components should preferably be reused. This can be either engine or CVT

parts from Suzuki, or custom designed race parts from previous years that have proven to perform well.

- Reverse engineering can be applied to complex parts like new designed housing for example. - Exotic transmission solutions are to be avoided. - The use of standardized parts, like bearings and seals, is favorable, instead of designing them

on specification.

3.4 Materials

The main two materials that are to be used are steel and aluminium. Highly stressed components, such as shafts, gears etc. will be made of high strength steel, for example 17CrNiMo6. Housing parts can be made of aluminium, whether it be a casting type or one suitable for milling or turning.


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3.5 Production methods

Although University Racing Eindhoven has some pretty well skilled craftsmen in its team and a small intern production facility at hand, these recources will only be used for making simple parts and assembling the car. Most parts will be manufactured at a professional facility that is present at the TU/e campus, namely the GTD (which stands for collective technical services).

At the GTD facility parts can be made by a variety of production methods, including milling, turning, welding, and electric discharge machining (EDM). Furthermore they have measuring equipment as well as a machine that can make 3D scans of objects.

For parts that are to be cast, i.e. aluminium housing parts, an external specialist is consulted and willing to cooperate in producing prototype casting parts.

3.6 Layout options

It is essential to check how much casting parts of the engine will have to be modified or even redesigned when choosing for a particular driveline layout. And to what extent they need to be changed; are modifications just minor or very intrusive into the existing design of the engine. Since the GSX-R600 is a high performance engine with very accurately balanced parts and optimized lightweight housing, altering the construction too much can endanger the reliability considerably.

Lets consider two opposite concepts, one being a solution where the complete gearbox part of the engine is being replaced by the CVT internals, surrounded by custom designed housing. The other a far more simple solution where the SECVT just is bolted on the engines output shaft. In the first solution the variator forms an integral part of the engine, where every single aspect can be optimized regarding packaging, weight and CoG. With the second solution, one is restricted to the shape of the existing housing parts and it will very likely result in a construction which takes up more space and weighs more. However, the second solution offers much more reliability, and also feasibility, because all phases (design, manufacturing, assembly, testing etc.) will have to be carried out by a limited number of people and within one year. Ofcourse, many solutions can be thought of, that are somewhere in between these two extremes. After numerous of brainstorms it became evident that some sort of compromise had to be made between optimality and reliability.

To begin with, a number of options are summed up below, with which can be varied.

- Engine placement transversal or longitudinal - Transversal: Engine exhaust side forward or backward - Longitudinal: Engine exhaust side left or right. - Transmission (CVT, clutch etc.) at original intake side or moved to exhaust side. - Transmission between engine and driverseat or between engine and driveshaft. - CVT components incorporated in engine housing or original CVT unit attached to engine.

Components that can be used to realize drivetrain layout concepts:

- Gears (spur, planetary, bevel gears, etc.) - Shafts, bearings. - Standard connection methods, such as bolted connections, splines, welding, etc. - Seals, static or dynamic (rotary seals, o-rings, liquid gasket, etc) - Gear chains, oiled when internal and greased if external. - Housing and mounting constructions

With these directions in mind, several concepts have been proposed. These can be seen in appendix B.


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The next step is to examine how much housing parts of the engine need modification or even redesign to realize a particular concept. Modifications include drilling mounting holes or cutting away certain pieces for example, while redesign means that it is required to replace a given housing section with a completely new part. Apart from that it may be possible to redesign the lowest sections of the engine housing, with the aim to lower the engine CoG. This will be examined seperately and is discussed in paragraph 3.8. Table 3.1 shows the absolutely necessary changes to the engine for each concept. Section denomination is explained below and shown in the accompanying pictures.

Requires

modification

Requires

redesign

A - a, b, c , d, e

B - a, b, c , d, e

C - a, b, c , d, e

D c -

E - a, b, c , d, e

F - -

G b, c, d a, e

H b, c, d a

I b, c, d a, e

J - -

After carefull examination of the engine / CVT construction and specifications the following design constraints have been imposed:

- The CVT primary pulley cannot be directly connected to the crankshaft, due to limited speed range. - The CVT primary pulleys centreline cannot be placed coincident to the clutchshafts centreline,

when placed at the gearbox side. This would cause the pulley to interfere with the crankshaft. - The clutch cannot be placed at the exhaust side of the engine, this would require a total engine

redesign and is therefore not recommendable. - When the engine is placed transversal, the CVT cannot be located next to it, due to limited width

space within the rear frame

These constraints render the following concepts infeasible: A, B, C, E, G. Concept F has good packaging, but is regarded as an impractical solution, due to the long chain final drive. This chain will also end up very near the left rear wheel, which will cause problems with the

e

a b

c

d

Fig. 3.1. and 3.2 Denomination of the engine housing parts

a = oil pan b = lower gearbox housing c = upper gearbox housing d = cylinder block e = clutch cover housing section line

Table. 3.1. Modification and redesign


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length of the driveshafts. (both driveshaft lengths are preferably equal to each other, or close to equal.)

Furthermore, concept H might look good at first hand, but has a bevel gear that is located at a point in the driveline, where angular speeds are still high. So this solution is also discarded.

Concept I will very likely result in a construction that takes up too much space in longitudinal direction (> 1m) , because engine, CVT and differential are all placed one behind another. In addition to that, the output shaft of the CVT will have to be relocated to the other side of the CVT.

This leaves concept D and J as possible candidates, so one transversal and one longitudinal solution.

Reliability and feasibilty

Since there is no actual testing proof of the performance increase the CVT will provide, it is not recommendable to fully integrate the CVT into the engine (though be it in a dry compartment). It will require many parts to be redesigned, which endangers reliability and feasibility, if designed in haste. Afterall, the car needs to be finished and tested within less then a year. It will also pose a major setback if the performance results are not as good as expected, considering the great amount of time, cost and effort that have to be put in a full-integration solution.

Regarding this, it has been decided to go for a bolt-on concept. Although weight and CoG are not optimal this way, it is nonetheless assumed that overall perfomance increase will not be affected too much because of that. To make up for increased weight, redundant material on the CVT housing and its internals will be removed, and lowering of the engine will further enhance the solutions characteristics. If it turns out that the CVT gives a substantial improvement to the cars performance, a further study can be conducted on a full integration. In this respect, the application of the CVT must be carried out in small steps, by which it will evolve into an optimal design.

3.7 Concept choice

From the investigation above, concept D and J have proven to be feasible solutions, which meet all requirements. The main two differences between these are the placement of the engine in the car, and the final drive. Concept D can make use of the already existent chain reduction, while concept J needs a bevel or hypoid gearpair to get the power to the rear wheels. Such a final drive is usually combined with the differential, as is the case with most rear wheel driven cars. In appendix C pictures are shown for both final drive types. It must also be noted that both concepts make use of an offset gearpair between the clutch and the CVT, to prevent the primary pulley from interfering with the crankshaft housing. This in turn gives the practical opportunity to use the existent gearbox for this function. 5 of the 6 gearpairs can be taken out as well as the original actuation mechanism, and with only slight modifications the necessary gearpair is realized. This solution further enhances the overall reliability of the drivetrain.

Both options have been abstractly modelled in 3D, using Unigraphics NX5, in order to visualize the spatial arrangment of all major components. In figures 3.3 and 3.4 these models are shown. Position and size of the driverseat, rearframe and driveshafts have been taken over from last years car, but their final design for the URE05 is still to be determined. It will nevertheless give a good indication of the packaging of all components.


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The shape of the CVT allows for a compact configuration, if the CVT is placed upright next to the gearbox. In appendix D top, back and side views of concept D and J are shown as well.

Fig. 3.3. 3D ISO visualization of concept D

Fig. 3.4. 3D ISO visualization of concept J


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In table 3.2 an overview is presented with important criteria, and how the two concepts differ from each other, regarding these criteria. It turns out that on most aspects concept D is the better solution, therefore we have chosen this concept to be the one that will be further worked out in detail.

Concept D J Comment

Packaging o o Both concepts have more or less equal powertrain packaging

Weight + - Bevel gear final drive type is usually more heavy than a chain type final drive

CoG o o Both concepts have more or less equal powertrain CoG

Cost + - Bevel gear final drive type is usually more expensive than a chain type final drive

Ratio adjustment + - Chain drive allows for easy replacement of sprockets, bevel gear does not. CVT servicability + - Concept D has better CVT access for demounting

Experience + - No URE experience with bevel gear final drive or ICE longitudinal placement so far

Final drive wear - + Chain drives show more wear than an oiled bevel gear final drive

Exhaust cooling - + Concept J has exhaust system located at right side, better airflow for cooling

Total +'s 5 2

To get an idea of how the actual construction of concept D will look like, a mock-up has been made. This mock-up is depicted in figure 3.5 below.

Fig. 3.5. Mock-up of the selected solution

Table 3.2. Comparison between concept D and J


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3.8 Lowering the engine

Although in previous years engine changes have been introduced in order to lower the engine location in the race car (wet sump dry sump, purple line in fig. 3.6), it appeared that even more progress can be accomplished, due to the application of a CVT. Since the gear selection mechanism is not needed anymore and it is originally located in the bottom of the engine, an empty compartment is created. This gives the opportunity to design a new lower gearbox housing, with the remaining lower engine components placed as low to the ground as possible. From figure 3.6 it can be immedeately seen that the clutch gear (yellow cirlce) is one of the lowest components that absolutely needs to be retained. Futhermore, the oil gallery (green dot) beneath the crankshaft is a vital part of the engine, that is preferably maintained at its original position. No other parts need to be present beneath these two parts, and consequently a substantial section of the lower gearbox housing (which is located under the blue line) can be removed. It is chosen to define the clutch compartment as the new underside of the engine, since it has a fairly large flat surface at the bottom (red line). Using this configuration, the original clutch housing cover will still fit and can therefore be left intact. Another advantage of choosing this surface is that it is located at an angle (+/- 15) with respect to last years dry sump oil pan (purple line) and will cause a rotated placement of the engine in forward direction. This again lowers the engine CoG with respect to the ground. Figure 3.7 shows the intended lower gearbox housing design.

Fig. 3.6. Side view of the GSX engine.

Blue = Gearbox section line

Yellow = Clutch gear

Green = Oil distribution gallery

Red = Underside of clutch compartment

Purple = Lowest surface of URE04 engine

Fig. 3.7. Intended lower engine housing


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Chapter 4

Detailed design

4.1 Introduction

Now that a drivetrain layout and configuration have been chosen, the next phase can be started with. In this detailed design phase, connection methods are determined and parts are given a shape that is very close to ready-for-production. Reverse engineering and estimations will be used to dimension new parts, so extensive calculations and FEM-analysis will only marginally alter the design. During the designing process, the directions and requirements formulated in chapter 3 have still been complied with.

4.2 Connection of the CVT to the engine

At first, the connection for transmitting power of the engine to the CVT will be examined, as well as how the CVT will be suspended in the car. In figure 4.1 the original input shaft of the CVT (left) and the output shaft of the engine (right) are depicted. One way or another, these shafts have to be connected to each other, thereby restricting relative motion between the two. Furthermore, correct sealing and shaft centering must be guaranteed. Several connection methods have been summed up, which can be made use of:

- spline (radial or axial) - key slot - welding - bolted flange connection - interference fit

- conical pressure fit - polygon connection - clips - loctite

Of course a combination of these methods can be applied. However, it is chosen to go for a demountable, stiff and play-free connection.

Fig. 4.1. 2D cross-section of the CVT input shaft (left) and the engine output shaft (right)


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As can be seen in figure 4.1. the engine output shaft protrudes quite far out of its housing. In order to place the CVT as close to the engine as possible (which is preferable), it is inevitable that the engine output shaft needs to be cut off for a certain amount. The CVT input on the contrary, is fairly small, so it leaves little room for modification. These two facts have lead to the decision to only modify the engine output shaft and make use of the spline and M12 fine thread that is already present on the CVT input. The CVT input spline will be measured and copied onto the engine shaft, presumably by EDM. A splined connector sleeve can then be slid over the two shafts, so torque can be transmitted. (see figure 4.3).

To fasten the CVT shaft axially to the engine, a bolt is used. This bolt can be put under a high pretension of approximately 45.2 kN (8.8 quality), or 66.3 kN (10.9). As well as shortening the engine output shaft, the 13mm hole that is already present, has to be drilled through to let the bolt fit. When the CVT needs to be disconnected from the engine, the clutch cover as well as the clutch have to be demounted, so the bolt cap is accessible for unscrewing.

Finally, to make sure that both shafts are correctly aligned, a center sleeve is added, which is placed on both housing hubs. Due to this sleeve a new rotary seal had to be chosen, a standardized 62x36x7mm was found to fit good. Two o-rings have been added as well, to make sure that the engine is completely sealed.

A preliminary calculation is done on the spline connection. This calculation is based upon DIN5480 and shows that at a input torque of 180Nm (allowable peak torque on belt) all safety factors are still well above 2. See appendix E for this calculation. Further calculations and FEM-analysis will be done on all parts, to ensure sufficient strength and stiffness.

Fig. 4.2. CVT input

Fig. 4.3. 2D cross-section of the engine - CVT connection

red = Spline connector blue = pretension bolt green = centersleeve purple = rotary seal / o-rings.


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4.3 CVT mounting

During a race, several forces are exerted on the the CVT which must all be supported by the CVT mounts. These forces can be divided into two major catagories, namely g-forces caused by gravity and accelerations, and reaction forces / torques from the engine and the final drive.

Although a final design is still to be worked out, a simple layout has been proposed, which is already shown in figure 3.3. The idea is to use a plate A (see figure 4.4.) which connects the CVT output hub to the differential and the engine. As can be seen in figure 4.5. the reaction forces of the chain (red), which tend to pull the CVT secondary side backwards, are supported by plate A. This results in a very short force loop for the chain forces, which are considerably high.

Plate B is added to support the differential on both sides.

Furthermore, the construction at C is used to fix the upper part of the CVT to the engine, in order to restrict rotational and transversal movement.

Fig. 4.5. Chain reaction forces supported by plate A

Fig. 4.4. Schematic model of the CVT suspension frame

A

B

C

A


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4.4 Transmission components

The gear reduction that must be present between the clutch and the CVT is easily realized by making use of the gears that are part of the engine gearbox. After an examination on reduction selection (see [5]) it became clear that the original 5th gear has the most appropiate ratio. When using this gear pair, speeds and torques that are transmitted to the CVT will stay beneath the allowable limits. Of course, other gearpairs can be applied as well, if necessary. Furthermore, designing a custom gearpair with optimized ratio is also an option. But for now, the 5th gearpair is taken to be incorporated in the design. It has a ratio of 1.208 (input speed over output speed). While normally one of the gears must be able to run freely on its shaft, both gears have to be fixed to their respective shaft now. Axial movement must also be restricted. In case of the 5th gearpair, the outgoing gear is fixed to the output shaft by means of splines, but it can still move in axial direction. Clips and bushes are the most easy way to fully fixate this gear onto its shaft. The ingoing gear needs some more attention however, it originally has a splined bush in its hub, that enables it to freewheel on the shaft when not selected. The dogteeth of the adjacent 4th gear are used to lock this gear to the shaft (ingoing gear 4 is rotationally fixed to the shaft with splines). Therefore this gear will be needed as well, it can be milled so that only a part with dogteeth and splines is left. Again, clips and bushes are added to make sure the ingoing gear is fully fixed.

Fig. 4.6. 2D cross-section of the gear reduction design

5th gear, in

Dogteeth body

Input shaft

Output shaft

Clips, bushes

5th gear, out


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4.5 Clutch actuation

Although the original clutch will be used in the new engine design, the placement of the CVT next to the gearbox will result in significantly less available space for the clutch actuator. This actuator normally consists of a clutch handle, a steel wire, a ball bearing spindle and 2 pushpins inside the gearbox primary shaft. When the wire is pulled, by means of the handle, a rotating motion of the spindle bearing is converted into a translational movement, which in turn causes the pins to push the clutch plate package open. It is this spindle bearing that cannot be fitted between the CVT and engine anymore, so a substitution must be found. Several options can be thought of, for instance the push-type of actuation can be transformed into a pull-type one, commonly seen on Yamaha motorbikes. This will require a redesign of the clutch cover housing and clutch pressure drum. Other, less drastic, possibilities, are a flat lever design to push the pin, or hydraulic actuation. In general, the main goal is to design a system which takes up no more than 30mm of axial space between the CVT housing and the engine gearbox. A complete description of that is not dealt with in this report, but nevertheless a brief solution is proposed, namely a hydraulic version. Advantages of hydraulics are the compactness, reliability and low complexity of the parts to be manufactured. In figures 4.7 and 4.8 an example is given of a hydraulic actuation, applied on a Formula Student race car of 2008. Next to that, a cross section is given of a simple design layout, applicable on the current engine / cvt design. 3D views can be found in appendix F.

Fig. 4.7. Picture of hydraulic actuation handle on steering wheel

Fig. 4.8. Picture of hydraulic actuation cylinder, mounted onto engine

Fig. 4.9. 2D cross-section of hydraulic actuation cylinder design proposal.


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4.6 The design in 2D

In this paragraph the reader is presented an overview of the design, using a 2D cross-section of the engine and the CVT. In this figure the complete transmission, from crankshaft gear to CVT output can be seen. Especially components that are new have been depicted in detail. Other components that will not be modified, such as the clutch, are shown with less accuracy. Furthermore a legend is added, in order to indicate the various component groups.

Housing

Gearbox shafts

CVT internals

Gears

Bearings

Sealing

Clips / bushes

Bolts / nut

Spline connector

Center sleeve

Clutch

Clutch actuation

Clutch actuation piston

Fig. 4.10. 2D Cross-section of the engine / CVT design


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4.7 Lubrication system

Since a large part of the lubrication system is situated in the lower gearbox housing, it is essential to make sure that every function of it is maintained when designing a new housing. In appendix G a comprehensive overview is shown of the standard engine lubrication system, as well as the modified dry sump system of 2008. The main differences of the dry sump system, in comparison to the wet symp, are coloured in blue. Furthermore, the dashed outline indicates the different parts and oil lines that are present at (or in) the URE04 lower gearbox housing. After a couple of modifications, the dry sump system of the URE04 race car has proven to work well, and therefore this system will largely be copied into the new gearbox housing design, as far as components are concerned. However, some components, like the oil filter / cooler assembly, will have to be replaced to another location. Several options have been looked at. It turned out that this assembly could best be placed at the crankcase de-aeration unit, which will not be used in the car. This location can be seen in figure 3.5 Oil lining will also be reconfigured, with the aim to have as few oil tubes outside the engine as possible. Also, oil lining length will be kept to a minimum. A part of the oil lining is integrated into the standard lower gearbox housing, these features on the new housing will be maintained as much as possible, or even further optimized. With the new lower gearbox housing design in mind, the scavenge pump can also be relocated into the interior of the engine; there is more space available due to the removal of the gear selection mechanism. All these measures together have lead to a simple and compact oil lubrication system. This assembly is depicted in figure 4.11.

Filter

Cooler

To swirlpot

From swirlpot

Pressure pump

Oil pressure regulator

Water inlet

Pump drive gear

Water outlet

Cover

Scavenging pump

To main gallery

Dry sump Scavenging pipes

To filter / cooler

Fig. 4.11. 3D model of the lubrication system components that will be located in the lower engine block.


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4.8 Lower gearbox housing

One of the most extensive parts that are to be designed is the new lower gearbox housing. Although the underside of the original housing will be left out, the remainder of the part will still have a complex shape with many details.

The following features will be incorporated into the design:

a. Packing surface for fitting of upper gearbox housing b. Packing surface for fitting of clutch cover c. Bearing hubs d. Main oil gallery and other distribution lines e. Hub for oil pump assembly f. (Threaded) Holes for bolts, dowel pins and oil tube connectors g. Reinforcement ribs h. Surfaces for guiding oil to scavenge pipes. i. Mounting supports for engine suspension

Production method

A subject of long debate has been wether the housing is going to be manufactured by casting or milling. Both methods have their advantages and drawbacks:

Casting Milling

Freedom of form design + -

Aluminium alloy strength - +

Wall thickness accuracy - +

Risk of production imperfections - +

Cost o o

As can be seen milling is regarded as a more safe production method, especially when it comes to single piece production. On the contrary, the fact that milling has far less freedom in design form implies that the housing will probably consist of several pieces, which will have to be bolted together for instance. Furthermore URE is eager to have more experience with product casting, as it can be applied to a whole range of other racing parts (uprights for example). Once a good connection has been established with a prototype casting specialist (including sponsorship), URE has gained a very valuable resource. Several casting specialist have been addressed already and one of them has accepted to produce the first products for URE. Concerning this, the new housing will be designed as a casting part. Of course another milling version can be designed as well, but that is out of the scope of this report.

2D measurement and modeling

The first step in the design was to measure the hole patterns of the 2 packing surfaces, as well as the location and diameter of the bearing hubs. These data have been imported into a 2D graphical application, and together with an overlay of high quality pictures the surfaces have been drawn in digital format.

Table 4.1. Comparison between casting and milling production method

Fig. 4.12. A view of the packing surface, halfway through the 2D design stage.


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3D modeling

The next step was to import the 2D data into a 3D modeler. In this program the packing surfaces could be extruded into bodies with volume. From this point on the rest of the housing has been designed, making use of reverse engineering of the original housing shape. Wall thickness has been kept in the range of 4 to 5.5 mm, however near bearing hubs more material thickness was allowed. The end result is shown in figure 4.13. In appendix H more views are depicted.

Special attention has gone to making sure that most of the oil will flow towards the gear reduction compartment. The clutch compartment has been semi-closed of by housing walls, and oil that does end up there, will be carried off by the large clutch gear (see figure 4.14.).

Although in figure 4.13 the final product is shown, an intermediate 3D model will have to be made, before it can be cast. This model will have extra material on it, primarily for letting the liquid aluminium flow into the mold (supply tubes), and as surplus material that will be removed when finishing the product in a CNC-machine.

Clutch compartment

Fig. 4.14. Any excess of oil in the clutch compartment will be transported to the main compartment by the clutch gear

Fig. 4.13. A full 3D view of the new lower gearbox housing. In the front part the main oil gallery can be seen, behind that are the gear reduction compartment (right) and the clutch compartment (left).


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4.9 The design in 3D

As a final result, the total assembly is presented, using 3D images.

Fig. 4.15.

View at the back of the lower gearbox housing. The gearbox housing is made semi-transparent, in order to show the location of the oil pump assembly.

As can be seen, the pipes for transferring oil to and from the swirlpot protrude through the gearbox housing.

The blue disc represents the part of the CVT housing, to which the engine is coupled.

Fig. 4.16. In this figure a section-view through the gear reduction is shown.


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Chapter 5

Conclusions

In this chapter the project is concluded; first an overall conclusion is given in paragraph 5.1 and secondly recommendations are presented in paragraph 5.2.

5.1 Conclusions

The aim of this project was to examine how the new SECVT could best be fitted into the driveline of the URE05 race car and what modifications were needed to the engine to accomplish that. Many aspects were involved in this problem, like driveline centre of gravity, weight, reliability and conservation of all necessary functions. After having looked at several options, which include CVT integration into the engine as well as longitudinal placement of the engine, the transversal bolt-on concept (D) was considered the best choice. Some properties of this concept are:

+ Reliable construction for testing and racing. + Feasible design and manufacturing within a few months. + Good and quick access to CVT for disassembly, maintenance or inspection.

- Higher weight and CoG, in comparison to a full integrated solution, more spacious as well.

To counter the fairly high weight and low compactness of the selected solution, a new lower gearbox housing has been designed that is more adapted to the use of a CVT. Redundant transmission components are left out and a more flat underside is applied, which enables the engine to be placed as low to the ground as possible. This new lower gearbox housing is designed as a casting part.

The design is currently further elaborated. Components are worked out to the last detail, with the help of calculations and FEM analysis. After that technical drawings will be made, so the design can be realized.

5.2 Recommendations

Regarding the project the following aspects are advised to carry out:

- Perform a complete cost-analysis on the chosen concept. - Perform a risk-analysis; identify possible weak spots in the total design. What worst-case

scenarios are there during operation for instance? Have things been overlooked? - The 3D housing design needs a thorough investigation on correct dimensioning, wall thickness,

castability, oil circuit diameters, etc. - Once corrected, the 3D housing design can be modelled again, starting with a new file. This will

improve the program structure of the 3D model considerably, as well as file size. The main advantages are: (1) better manageability in large 3D assemblies and (2) a more understandable model structure, for people who have not been involved yet, but who need to work with it in later stages of the project.

- The existing lower gearbox housing can be used as well, for testing of the CVT on the test rig. It is strongly recommended to perform initial performance and durability tests using this setup, before actually giving green light to the production of the new designed casting part. Therefore, shaft connection components and the mounting construction should have production priority.

- If the CVT drivetrain shows good results and adds to a more competitive race car, the whole concept can be taken to a higher level. This involves a complete new powertrain, with lower fuel consumption, lower weight and better adjustment of all components to each other.


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Bibliography

[1] Fundamentals of machine elements

o Bernard J. Hamrock Bo jacobson Steven R. Schmid Publisher: The McGraw-Hill Companies, Inc. / 1999 ISBN 0-256-19069-0

[2] Roloff / Matek, Machineonderdelen ( + Tabellenboek)

o Wilhelm Matek Publisher / date: Acedemic Service, Schoonhoven / 2000 ISBN 90-395-1422-4

[3] Suzuki AN650 Service Manual

o Suzuki Motor Corporation 2002 Nr. 99500-36110-01E

[4] Suzuki GSX-R600 Service Manual

o Suzuki Motor Corporation 2000 Nr. 99500-35081-01E

[5] Design of a high performance drivetrain for the URE05

o H.M.A. Smetsers Masters thesis Publisher / date: Not published yet

[6] Haalbaarheid van een CVT in een Formula Studentauto

o M.H.L.M. v.d. Tillaart date: april 2004

[7] Implementation of a Suzuki CVT in a in a Formula Student race car

o B.B.F.M. Kuijpers Bachelor end project date: October 2008

Modification of a Formula Student race car engine, for addition of a Continuously Variable Transmission

APPENDIX

L. Marquenie

AES 2008.135

Master Traineeship

Coach: Dr. Ir. P.C.J.N. Rosielle Supervisor: Prof.dr.ir. M. Steinbuch

Institute: Technical University of Eindhoven Department of Mechanical Engineering Section Automotive Engineering Science

Period: Summer 2008


2

Contents

APPENDIX A - Specifications sheet URE05....................................................................................3

APPENDIX B - Layout options (top view).........................................................................................5

APPENDIX C - Pictures of final drive types......................................................................................8

APPENDIX D.1 - Concept D packaging visualization (side, top and rear view)..................................9 APPENDIX D.2 - Concept J packaging visualization (side, top and rear view).................................10

APPENDIX E - DIN5480 Calculation of Engine-CVT connector sleeve (dutch).............................11

APPENDIX F - Clutch actuation design in 3D...............................................................................13

APPENDIX G.1 - Engine Lubrication : standard wet sump scheme..................................................14



APPENDIX G.4 - Engine Lubrication : Modified dry sump scheme...................................................17

APPENDIX H - Various views of the lower gearbox housing design..............................................18


3

APPENDIX A - Specifications sheet URE05

Vehicle specifications Vehicle type Formula Student single-seater race car Vehicle design weight 200 kg Chassis front Multishell Carbonfibre monocoque Chassis rear Steel tubular spaceframe Overall dimensions [L x W x H] 2820 x 1334 x 975 mm Trackwidth 1125 mm Wheelbase 1600 mm Suspension Full multilink system Rims Custom 13" carbon fibre rims Tyre type Custom Hoosier or Goodyear Rdyn 250 mm

Performance Acceleration 0-100 km/h 3.5 s. Top speed adjustable 120 - 150 km/h


4

Engine specifications Type 4-cil. 16V DOHC Displacement 599 cc Inlet restriction diameter 20mm Bore x stroke 67 mm x 42.5 mm Compression ratio 12.2:1 Max. power output 65 kW @ 12.000 rpm Max. torque 62 Nm @ 8.000 rpm Max. rpm 13.500 Min. rpm 3.000 Lubrication system Student designed dry sump system Injection Student designed Motec M-400 Clutch 9 plate wet clutch, pushpin actuation

Gearbox transmission ratios Primary reduction 1.927 (79:41) 1st 2.785 (39:14) 2nd 2.000 (32:16) 3rd 1.600 (32:20) 4th 1.363 (30:22) 5th 1.208 (29:24) 6th 1.086 (25:23) Ratio coverage 2.56 Gear teeth type Straight, involute

Final drive Type Chain reduction Ratio 3.82 (42:11) Differential Limited slip

SECVT specifications Type Dry hybrid belt variator Actuation Servo electronic with 1:90.8 gear stage RLOW 1.8 ROD 0.465 Ratio Coverage 3.87 Centreline distance 148.5 mm Weight 25 kg Est. weight after optimization 20 kg

Max input speed (standard) 7000 rpm Max input torque (standard) 74 Nm Max input torque (Contitech belt) 130 Nm Max torque peak (Contitech belt) 180 Nm @ Rmid


5

APPENDIX B - Layout options (top view)

F = Forward B = Backward

Concept D Spur gear pair between clutch and CVT for creating distance between CVT and crankshaft.

Concept A CVT directly on clutch output, intermediate gear (red) within primary reduction for direction reversal and extra offset between primary pulley and crankshaft

Concept B Engine reversed, Transmission relocated to exhaust side of engine. Intermediate gear within primary reduction for direction reversal and extra offset between primary pulley and crankshaft. Planetary gear for reversal of direction.

Concept C Engine reversed, Transmission relocated to exhaust side. Gear chain between clutch and CVT for creating distance between CVT and crankshaft.


6

F = Forward B = Backward R = Right L = Left

Concept F Engine reversed, CVT between seat and engine, gear chain between clutch and CVT for creating distance. Long chain for transferring power to wheels

Concept G Engine reversed, CVT connected directly onto clutch and located next to crankshaft.

Concept H Engine placed longitudinal, bevel gear between clutch and CVT for 90 degree turn of shaft rotation.

Concept E Engine reversed, CVT directly on clutch output. Transmission relocated to exhaust side of engine


7

F = Forward B = Backward R = Right L = Left

Concept I Engine placed longitudinal, CVT located next to crankshaft, bevel gear incorporated in differential

Concept J Engine placed longitudinal, spur gear pair between clutch and CVT for offset. Long shaft over transmission to combined bevel gear / differential.


8

APPENDIX C - Pictures of final drive types

Bevel gear final drive

Chain reduction final drive


9

APPENDIX D.1 - Concept D packaging visualization (side, top and rear view)


10

APPENDIX D.2 - Concept J packaging visualization (side, top and rear view)


11

APPENDIX E - DIN5480 Calculation of Engine-CVT connector sleeve (dutch)

Splines Engine_CVT connector Statische berekening piekbel.

DIN 5480 As Naaf keuze aflezen benaderd berekend Splinegegevens

z (-) 24 24 aantal tanden m (mm) 1 modulus alpha (gr) 30 drukhoek b 10 dragende splinebreedte

x*m (mm) 0,1 0,1 profielverschuiving (as)

h_aP (-) 0,45 0,45 kophoogtefactor h_fP (-) 0,55 0,55 voethoogtefactor d (mm) 24 24 steekcirkel (=m*z) d_a (mm) 25,1 23,3 kopcirkel d_f (mm) 23,1 25,3 voetcirkel d_b (mm) 20,7846 20,8 basiscirkel (=d*cos(alpha))

sp_kop (mm) 0,1 kopspeling (=d_f2-d_a1 of d_a2-d_f1) h (mm) 0,68 dragende tandhoogte (=(m-sp_kop)/cos(alpha))

s_voet (mm) 2,0944

Asgegevens

d_gat (mm) 13 asgat I_p (mm^4) 29768,1 polair opp.traagheidsmoment (=pi/32*(d^4-d_gat^4)) c (mm) 12,55 maximale vezelafstand (=d_a/2) W_w (mm^3) 2371,96 weerstand tegen torsie (=I_p/c)

Belasting

T_w (Nm) 180 torsiemoment t.h.v. spline (piekbelasting) k (-) 0,75 verrekening percentage van tanden in ingrijping (zie [DUB]) F_t (kN) 0,83 omtrekskracht per ingrijping (=2*T_w/d/z/k)

Materiaal

R_e (N/mm^2) 785 rekgrens materiaal

k_2 (-) 0,58 verrekening toelaatbare materiaalspanning voor torsie tau_w_toel (N/mm^2) 455 toelaatbare torsiespanning (=R_e*K_2)

v_v (-) 3 verrekening type belasting (zie tab. 12-1b [Roloff / Matek]) p_toel (N/mm^2) 262 toelaatbare vlaktedruk (=R_e/v_v)


12

Berekende torsiespanning

tau_w0 (N/mm^2) 75,8867 nominale torsiespanning (=T_w/W_w) S_w (-) 5,99973 veiligheidsfactor (=tau_w_toel/tau_w0)

Berekende voetspanning

sigma_voet (N/mm^2) 56,9932 nominale voetspanning (=6*T_w*m/d/z/k/b/s_voet^2) S_s (-) 6,88679 veiligheidsfactor

Berekende vlaktedruk

p_0 (N/mm^2) 123 nominale vlaktedruk (=F_N/h/b) S_p (-) 2,14 veiligheidsfactor (p_toel/p_0)


13

APPENDIX F - Clutch actuation design in 3D


14

APPENDIX G.1 - Engine Lubrication : standard wet sump scheme


15

APPENDIX G.2 - Engine Lubrication : standard wet sump technical drawing


16

APPENDIX G.3 - Lubrication system : standard wet sump technical drawing


17

APPENDIX G.4 - Engine Lubrication : Modified dry sump scheme


18

APPENDIX H - Various views of the lower gearbox housing design


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modification of a formula student race car engine, for addition of a continuously variable...

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