Pneumatic Shifting and Clutching and integration

UCONN FSAE

Overview of Pneumatics specific to our application

The use of pneumatics in this application is tried and trued

Provides the fastest means of shifting the car when paired up with the ECU

Solves the issue of having to get the input from the driver back to the engine

Overall cost can be anywhere from $200 to over $400

Integration with related systems

Shifting goes hand in hand with many systems ECU Driver Frame Engine

Lets go into detail...

Pros and cons over other methods

VS Mechanical: Pros: Faster shifts Easier to operate for inexperienced drivers Easier to fit (more mounting options)

Cons: More complex Heavier More expensive

Pros, cons, continued

VS All electric: Pros: Lower current draw (10 watts) Common in our application Less expensive?

Cons More parts

RAPTO-R

Supply: CO2 v. HPA CO2

Small, Light tanks Cheap ($15 for 20oz tank) Risk of freezing, liquid CO2 getting into lines,

and pressure flux Risk of venting (if left in the sun)

HPA No risk of risk of freezing, liquids or pressure

flux Fill level is easy to know (explain) Slightly larger (radius), slightly heavier More expensive (20 to 120 more (explain))

On HPA

A 48ci, 3000psi HPA tank is good for over 3000 shifts

assuming ideal gas, and no heat transfer and using P1*V1=P2*V2

Given an operating pressure of 100psi and a 3/4in bore cylinder with 1in stroke

A 3000psi, 48ci, steel tank weighs 2.8 pounds and measures 9 7/8 inches high with reg ($40)

A 4500psi, 48ci Guerrilla Air fiber tank weighs 1.8 pounds empty and measures 3.7w X 8h ($164)

Regulator and piping

Palmer Pursuit custom paintball produces low pressure regulators for $50-110 depending on the reg. The only paintball company I know of that does so.

Most of their regulators output in 1/8in, solenoid valves are common in that size, so are pneumatic cylinders

Controller (RAPTO-R)

Primary goal: create something with enough intelligence to open the valve and hold it until a new gear has been successfully engaged

receive a signal to indicate successful completion of a shift

Secondary goals: Over-rev protection Auto up-shifting Automated clutching

About clutching The clutch only needs to be used on

downshifts Automating the clutch means you only need

two pedals However it creates the issue of not having

revs matched on down shifts Possible solution: “Preselect gearbox.” Set the

controller so that it will only down shift after it has received a signal from both the clutch and the shift button

This requires either a third pedal, a hand clutch or separate clutch button

Valves

3 port, 2 position valves Valve must have sufficient flow to energize

and vent the cylinder quickly Most solenoid valve have +1million cycle life Less than 10w power draw is typical

Cylinder

Bore size and stroke length need to be considered

Both affect the cylinder's footprint Bore size directly affects the cylinder's power Stroke length is determined by how long the

lever is coming off the shift rod Which is better, short stroke high force, long

stroke low force, somewhere in between?

Cylinder, another consideration

To long of a stroke (for a given shift arm) can mean the cylinder uses the shift linkage to bottom out, possible resulting in breakage

The cylinder has to be long enough to move the shift lever as if it were still on the bike

Rubber bushings on the mounting points for the cylinder reduce this risk while allowing a long enough cylinder to be used

Redundancy

Micro Switches: A common point of failure Solution: Include a pair of push buttons

mounted on the dash that completely bypass the controller and energize the valves directly

Lines and Connections: No redundancy thorough testing and high quality parts

should be adequate

Time line

Within 3 weeks: Complete all required calculations and measurements

Before Winter break: Finalize part choices, look for discounts/sponsors. Possibly order parts.

Back from break: Order parts Mid February or earlier: Begin testing, bench

or otherwise.

Final thoughts (finally)

How important do I consider shifting? It's all a matter of gearing

Mechanical, pneumatic, both? Well, it depends

Is it worth it? My opinion: Yes, letting the driver keep there

hands on the wheel at all times make up for the 2 or 3 pounds of extra weight

Lets take a step back and look at what we are actually doing.