Got
Gas...
Propellant gases are those gases used in air shifting systems to propel
or actuate the air cylinder that has the job of pushing or pulling
the shift lever to engage the next gear. The three most common of
these gases are Carbon Dioxide, Nitrogen, and Air. Each has advantages
and disadvantages.
Carbon
Dioxide...
Let's talk about carbon dioxide first as it is, in our opinion, the
worst possible choice for a propellant. It has the advantages of being
easy to get and it is inexpensive. For these reasons it seems to be
a popular choice even with its drawbacks. The biggest problem with
Co2 is the temperature of the gas drops so dramatically, upon expansion,
it freezes everything associated with it. This causes tremendous amounts
of condensation to form causing solenoid valves and other components
to ice up hindering flow and movement. The ice eventually turns to
water and further hinders the performance of the system and shortens
the life of the components. Co2 has a further disadvantage of having
the lowest coefficient of flow of the three gases we are discussing
here. It is this coefficient of flow that determines how fast or how
slow the air cylinder will fill during the shifting process. This
is a key factor in how long it is going to take to perform the shift.
Remember, the longer it takes to make the shift the less time your
putting power to the ground. Which in turn means the slower you go.
Nitrogen...
For those who wish to stay on the cutting edge and are willing to
spare no inconvenience or expense in maintaining any advantage, no
matter how small, Nitrogen is the propellant of choice. Nitrogen has
some distinct advantages. Advantage one is it is dry. It is so dry
in fact it will pull any moisture out of the system that may be hiding
there. Advantage two is it has the highest coefficient of flow of
the three gases. High flow equals faster shifts and faster shifts
mean lower E.T.'s and higher MPH.
High Pressure
Considerations...
With Co2 or Nitrogen there are some special considerations. A bottle
will have to purchased and once filled you'll need a regulator to
go with it to get the pressures down to a useable level. A filling
station will need to be located to have the bottle refilled occasionally
and there is some expense involved. An advantage of the high pressure
gases is one can equip his or her bike with an onboard high pressure
setup that will not require refilling except occasionally. This high-pressure
setup will however require the installation of an onboard pressure
regulator to limit the pressure to the shifter to 120 to 150 psi depending
on your system. Of course you don't have to have an onboard high-pressure
system. The regulator can be located on the bulk bottle and you can
refill your onboard reservoir to the usual 120 to 150 psi between
rounds.
Air...
Good old air. It is plentiful, it is easy to get and it is free. What
more could one want. Surprisingly, air also has a better coefficient
of flow than Carbon Dioxide though not quite as good as Nitrogen.
Again, better flow means faster shifts. All of the above make it the
perfect choice. It does have the disadvantage of holding some moisture
but if you drain your system completely at the end of each race day
this should not create any problems and any detrimental effects to
the components will be minimized. One other inconvenience is the need
to refill the on board reservoir after each round of competition.
Portable, battery powered, recharchable inflators that will pump up
to 200 psi can be purchased for a reasonable amount. All things considered,
this is our number one choice of propellants.
Storage...
Regardless of which propellant gas is used a storage reservoir is
needed. The most common is an air bottle. There two types of air bottles
available. One is D.O.T. approved and stamped as such and the other
is not. A D.O.T. bottle will be required when running a Co2 or Nitrogen
high pressure setup as it is approved for the high pressures. Most,
but not all, racing sanctions require a D.O.T. bottle regardless of
the propellant being used. Check the rules. The alternatives are to
fab and air bottle or air tank or to store the propellant in the frame
or, more commonly, the swingarm. This "in the frame" alternative
usually gets around the D.O.T. requirement.
That's
it...
Hope it helps you go a little quicker and a little faster.
Ride
Safe...Race Safe
