UCONN FSAE
Pneumatic Shifting and Clutching
and integration
Overview of Pneumatics specific to
our application
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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
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Shifting goes hand in hand with many systems
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ECU
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Driver
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Frame
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Engine
Lets go into detail...
Pros and cons over other methods
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VS Mechanical: Pros:
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Faster shifts
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Easier to operate for inexperienced drivers
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Easier to fit (more mounting options)
Cons:
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More complex
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Heavier
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More expensive
Pros, cons, continued
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VS All electric: Pros:
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Lower current draw (10 watts)
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Common in our application
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Less expensive?
Cons
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More parts
RAPTO-R
Supply: CO2 v. HPA
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CO2
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Small, Light tanks
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Cheap ($15 for 20oz tank)
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Risk of freezing, liquid CO2 getting into lines,
and pressure flux
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Risk of venting (if left in the sun)
HPA
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No risk of risk of freezing, liquids or pressure flux
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Fill level is easy to know (explain)
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Slightly larger (radius), slightly heavier
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More expensive (20 to 120 more (explain))
On HPA
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A 48ci, 3000psi HPA tank is good for over
3000 shifts
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assuming ideal gas, and no heat transfer
and using P1*V1=P2*V2
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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
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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)
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Primary goal: create something with enough
intelligence to open the valve and hold it until a
new gear has been successfully engaged
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receive a signal to indicate successful
completion of a shift
Secondary goals:
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Over-rev protection
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Auto up-shifting
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Automated clutching
About clutching
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The clutch only needs to be used on
downshifts
Automating the clutch means you only need
two pedals
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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
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3 port, 2 position valves
Valve must have sufficient flow to energize and
vent the cylinder quickly
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Most solenoid valve have +1million cycle life
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Less than 10w power draw is typical
Cylinder
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Bore size and stroke length need to be
considered
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Both affect the cylinder's footprint
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Bore size directly affects the cylinder's power
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Stroke length is determined by how long the
lever is coming off the shift rod
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Which is better, short stroke high force, long
stroke low force, somewhere in between?
Cylinder, another consideration
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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
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The cylinder has to be long enough to move
the shift lever as if it were still on the bike
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Rubber bushings on the mounting points for
the cylinder reduce this risk while allowing a
long enough cylinder to be used
Redundancy
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Micro Switches: A common point of failure
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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
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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)
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How important do I consider shifting?
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Mechanical, pneumatic, both?
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Well, it depends
Is it worth it?
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It's all a matter of gearing
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.