FSAE Damper DynamometerOperating Instructions

Adjust the Maximum Displacement1) Open the door to the cam area.2) Each hole in the cam flywheel adds 0.5 in. (12.7 mm) radius from the center of the flywheel.

Determine your total desired damper displacement and divide that number by two. That is the hole that the connecting rod should be placed. For example, if you want a 5 in (127 mm) total displacement on the damper, place the connecting rod in the 2.5 in (63.5 mm) hole. Torque the 1/4-20 screw to 9.0 ft-lb (12.2 N-m). The damper dynamometer is capable of producing from 1 inch (25.4 mm) to a maximum of 7 inches (177.8 mm) of displacement.

3) Rotate the cam to bottom dead center if necessary.

Mount the Damper1) Open the door to the mast and place the body of the damper in the upper clevis. This will keep

the damper body fixed throughout the run and the temperature reading more stable.2) Slide the pin through the upper eyelet of the damper and slide the hairpin cotter into place to

keep the pin secure.

3) Loosen the 8 bolts that hold the crossbar to the masts and adjust the height of the mast so that the damper can be mounted to the bottom clevis at near full extension. It is important to not have the damper at its maximum length. As the dynamometer rotates, it will constantly hit the physical bottom of the damper and cause damage to the damper or the dyno.

4) Once the mast is at the desired height, torque the qty. (8) 3/8-16 screws that hold the mast to 33 ft-lb. (44.7 N-m).

5) Slightly compress the damper and slide the lower pin into place to secure the damper. It may be necessary to shim the damper with washers so that it won’t slide side to side in the clevis.

Mount the Linear Potentiometer1) Attach the fixed end of the L-pot to the top clevis pin and secure it with a hairpin cotter.2) Connect the plug of the L-pot to the dynamometer.3) Attach the sliding end of the L-pot to the lower clevis and torque the 10-32 screw to 31.7 in-lb.

(3.58 N-m).

Verify the Damper Setup1) Slowly rotate the cam rotor one complete revolution by hand and verify that the damper under

test does not bottom out at top dead center or at bottom dead center. If it does, adjust the mast height or the cam displacement so that no damage occurs during the run.

2) Similarly make sure that the linear potentiometer doesn’t bottom out at either extreme as well.3) The dynamometer is capable of generating thousands of pounds of force and damage will occur

to the L-pot or the damper if it is not installed properly.

Adjust the Temperature Sensor1) Adjust the temperature sensor so that it is approximately 2 inches (50.8 mm) from the body of

the damper.2) The small lens should be pointed at the center of the damper body for the most accurate

measurement.3) Close the doors to the cam area and the shock area in preparation for the run.

Setting up the User InterfaceIn order to control the damper’s shaft speed, the program will need to know what radius the connecting rod is in. Additionally, the program will need to know the maximum displacement that the L-Pot will measure (this should be more than it will travel during the run to avoid damaging it). Write these numbers down so that you can enter them into the program prior to running.

Open the FSAE Damper Dynamometer Control program.

If you are more comfortable working in US Standard units rather than SI units, click Setup -> Display Units and select your preferred units. Note that all internal storage of parameters and calculations are done in SI units and this will only affect the display to the user.

Enter your car parameters (or load them from a file using Car-> Open Profile)

Adjust your front and rear decision points so that the optimal curve (in gold on the chart) can be calculated and plotted. As you change parameters you can immediately see the effect on the chart of changing that parameter (if any).

Select the radial button to choose using the front decision points, or the rear depending on which damper is being tested. Other than the knee speed, the decision points will make no difference to how the damper is tested so if you just want a force vs. velocity curve of the damper, ignore this section.

If you wish to save the parameters into a car file, choose Car -> Save As… to save them. It may be beneficial to create files for each track that your vehicle runs on so you can quickly recall these parameters.

The car file is a text file and can be edited outside the program. All of the parameters in the car file are in SI units because all internal calculations are done using them. Below is a sample car file.

// RIT shock dyno car parameter file// All parameters are in SI units// Set the following line to False to have your parameters displayed in US Standard units// in the FSAE Shock Dyno application.True// Car Parameters235, 46.74, 6.85, 7.12, 26.27, 0.909, 35.03, 0.909, 91.84, 91.84// Front decision parameters25.4, 3, 1.25, 1, 1.5, 0.65, 1// Rear decision parameters25.4, 2.5, 1.13, 1, 1.5, 0.7, 1

If for some reason, you close out the program and forget to save your parameters, re-open it. Your last settings will be remembered and you can save them.

Connect to the dynamometer with a USB cable. Then choose Setup -> Comm Port and pick the serial port of the dynamometer. If no serial ports are shown, make sure that the drivers for the Arduino Due are installed and the USB cable is connected to the dyno. Each time you hover your mouse over the Comm Port menu, the program will refresh the list of serial ports so that you can pick the proper port once it is available.

Important: Make sure that there is a good approximation or a known knee speed in the knee speed decision boxes. The dynamometer will step through several speeds using the knee speed value. It selects 0.50, 0.75, 1.00, 1.25, 1.50, 1.75, 2.00, 5.00, and 10.00 times the knee speed as its set points. If the set point exceeds the maximum linear speed based on the motor’s maximum rotational speed the dyno will skip that point.

Running the DynamometerOnce you are ready to run, click the big green run button. The following submenu is displayed.

Verify that you have checked all the items on the left and place a check in each box. Enter your maximum measurement range of the L-pot into the text box on the bottom and choose which cam position (and maximum displacement) you have used.

Press Ok. If the program is satisfied with the values entered, the dyno will zero the load cell and make one slow revolution to verify that the L-pot doesn’t bottom out during the run. If it is satisfied, it will then proceed to characterize the damper using the knee speed set points above.

As the dyno runs, actual data will be plotted on the chart overlaying the gold target line. This way, you will know the performance of your damper compared with the target and you can make adjustments between runs. The current temperature of the damper will be displayed below the chart as well.

The dynamometer runs for 30 seconds at each set point to allow the shock to reach thermal equilibrium.

Once the program finishes running (or you stop the run) you can save the data collected during the run. Name the file so that you know which shock was tested and what track it was for. The data is saved in a comma separated value file (.csv) so that you can open it in Excel, MATLAB, or any other analysis software you wish to use.

Below is a sample of the data file generated by a run.

Date/Time, Linear Velocity (mm/s), Bump Force (N), Rebound Force (N), Shock Temperature (°C)05/11/16 18:50:20, 12.7, 85.6287905866164, -85.6287905866164, 40.0405/11/16 18:50:21, 12.7, 85.6287905866164, -85.6287905866164, 39.9905/11/16 18:50:22, 12.7, 85.6287905866164, -85.6287905866164, 39.7505/11/16 18:50:23, 12.7, 85.6287905866164, -85.6287905866164, 39.9305/11/16 18:50:24, 12.7, 85.6287905866164, -85.6287905866164, 39.8805/11/16 18:50:25, 12.7, 85.6287905866164, -85.6287905866164, 39.8805/11/16 18:50:26, 12.7, 85.6287905866164, -85.6287905866164, 39.8505/11/16 18:50:27, 12.7, 85.6287905866164, -85.6287905866164, 39.8305/11/16 18:50:28, 12.7, 85.6287905866164, -85.6287905866164, 39.8

As can be seen, data is collected every second and a header line is at the top for labeling the columns. Each successive run after the first, the run menu will remember the cam displacement and L-pot measurement range so that you can make adjustments and not need to remember the values. If you close the program and restart it, these values will be lost.

We hope you enjoy using the damper dynamometer as much as we enjoyed designing and building it.

Sal Fava, Mechanical Engineering (Stand and mast)

Chris Batorski, Mechanical Engineering (Moving Parts)

Aung Toe, Electrical Engineering (microcontroller interface design and coding)

Jim Holmes, Electrical Engineering (high voltage and safety circuits and User Interface)

Andy Dodd, Industrial Engineering (crossbar and safety enclosure design, technical resource)