1. Pneumatic Shifting and Clutching and integration
UCONN FSAE
Pneumatic Shifting and Clutching and integration

2. 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

3. Integration with related systems
Shifting goes hand in hand with many systems
ECU
Driver
Frame
Engine
Lets go into detail...
Driver: Shifting is one of the key components the driver uses to control the car. We have to consider where and how the controls are going to be mounted along with what EXACTLY we want them to do. Do we just want the system to shift up and down, or do we want it to do extra stuff like auto-upshift and stall protection. Do we have a hand clutch or seperate pedal? Do we let the shift system clutch for us or do we let the driver do it.
Frame: This falls under the idea of “design the frame last”, but all of the shift bits need a place to go. If it is done as an after thought we end up with what happened last year. This is double important when it comes to a mechanical system. We need to consider where cylinders, pedals and switches mount in the case of a pneumatic electric system. In the case of a mechanical system we need to look at where levers go and how the transmit their force
ECU: We have a lot of flexibility here. System integration can range anywhere from complete (the shift logic controller and the ECU work in tandem) to completely none existent, where the shift set-up is completely dumb and the ECU is controlled purely on inputs directly from the driver

4. 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
Easier to operate: Your hands are always on the wheel and you dont have to worry about throttle inputs outside of “want to go faster push pedal harder”

5. Pros, cons, continued VS All electric: Pros: Cons
Lower current draw (10 watts)
Common in our application
Less expensive?
Cons
More parts

6. RAPTO-R

7. Supply: CO2 v. HPA CO2 HPA 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))
It's worth pointing out that the only difference between HPA and CO2 when it comes to design is tanks size and orientation. A C02 a co2 tank needs to be kept somewhat upright so that liquid co2 is not drawn into the system

8. 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)
P1*V1=P2*V2

9. Regulator and piping
Palmer Pursuit custom paintball produces low pressure regulators for $ 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
I put such a large emphasis on paintball regulators because they are fairly inexpensive, come in a small package and are very durable while at the same time being very high performance

10. 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
Primary: that signal could possibly be off the gear position indicator
Secondary: over rev: the controller should prevent downshifting if it puts the engine past red line
There has been a slight setback with this system. The pin-out for the FPGA is not something that is hand solderable. Right now we (Matt, Joe, and I) are looking into a means to convert the surface mount of the FPGA into a through hole mount.
Planning to have a meeting discussing the issue due to the importance of this controller to so many aspects of the car.

11. 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
The GSX comes with a slipper clutch. Does that clutch pack slip enough to ignore rev matching?
The ECU supports flat shifting, that is it can cut or retard spark automatticly when a clutch signal is received so that the gears are able to engage.
However flat shift mode is only activated when the car is being run at WOT. This is something that needs to be considered no matter what shifting system is used.
Given that we are most likely going to use Speed-density tuning methods the throttle position makes no difference (the number off of the TPS SENSOR) make no difference to the ECU's fuel map

12. 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

13. 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?
The only consideration I have come up with on short vs long stroke are:
A cylinder that has a short stroke is going to be generating more force on its mounting points, on the other hand the shorter lever arm can allow the cylinder to return to battery faster. More research is needed
Naturally overall size is a consideration

14. 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
Cylinder has to be long enough...: By which I mean it has to to reach the travel stops (or in this case fully move the dog rings).

15. 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
Micro switches are what are used to send signals to the controller. The are mounted to the steering wheel and are the most critical component of “flappy paddle shifters”
The two issue with line and connections are leakage and blow outs.
Running higher pressure is more likely to cause blow out. Running higher pressures lets you save weight and space when sizing the cylinder. How high strung do we want to make the system?
James told me about connectors that are used for transporting hydrogen. Anything bad ass enough to be used for hydrogen should be plenty adequate for this
Combating leakage is simply a matter of getting the system assembled early and bubble testing it. Slight leakage after the valves is acceptable

16. 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.
Calculation: Figure out cylinder size, line pressures, vlave size, tank size(s)
Finalize part choices: Brands, cost and advertised durability.
Testing: Ideally I would like to do testing on the car itself, but because we dont plan to have the car finished until some time in march, bench testing is going to have to suffice for the beginning.

17. 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.
How important: As an AutoXer the first thing I was taught to do was “put the car in second gear and worry about where you are going”. In most cars this is very easy to do thanks to wide power bands and favorable gearing
In our case things are a bit more difficult thanks to a narrow power band and short gearing that we will be using. Thus, shifting is important enough to justify the serious thought given here.