Wednesday, March 23, 2016

Crescent Rose Fix #2 Pneumatic System Fixes

One of the major problems that Crescent Rose has is that charging air into its pneumatic system requires an electrical outlet port which isn't found very often in conventions. This wouldn't be much of a problem itself if Crescent Rose could also hold the air that it was charged with for a long time. Sadly it can't hold the air it is charged with for very long and so Crescent Rose wasn't able to move as often as I would have liked at Otakon 2015.

There were two potential solutions that I came up with on the spot.
  1. Use a small hand pump.
  2. Power the pneumatic system using CO2 instead of HPA (High Pressurized Air).

Considering that Crescent Rose requires about 60 psi to go through one piston extension and retraction, a small hand pump might just be good enough to fill the pneumatic system on Crescent Rose without an electrical outlet. Depending how long it takes to fill the system, this might be the best option in terms of portability, speed of refill, and money. I will have to buy a small air pump and run some tests to see if this is the best option.

The other option is to feed CO2 through the system with CO2 cartridges. These things:

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How it works is that in order to release the air, you have to pierce the top in order to get the gas to expel. There are many industrial uses for these cartridges from food uses to biking to bb and paint guns.  The plan was to buy some of these cartridges and buy a CO2 bike inflator to fill up Crescent Rose just like how Myrtenaster uses an inflator to shoot dust.

However, CO2 is really, really cold as a gas. Depending on the amount of pressure in the system, you can get temperatures as low as -40 degrees Celsius. The solenoid that I am using can not handle gasses that low of a temperature. With the solenoid priced at about $60 each, it's something I didn't want to risk.

But not all was lost, I found out that you can get the same cartridges in N2, nitrogen gas. HPA is actually made up of mostly N2 and this gas should be a perfect replacement for the CO2 if all goes well. It's harder to find and a bit more expensive but depending on the speed of refill this might be it. I will have to run some tests with this too.

My shopping list:
  •  1.8gram N2 cartridges from Leland gas technologies (P/N: 42222N21700)
  • Nashbar Mini Pump from Nashbar (P/N: BN-MINP) 
  •  Schrader valve: Campbell Hausfield 1/8" NPT Tank valve from HomeDepot (P/N: MP322900AV) x2 
  • 18gram N2 cartridge from Leland gas technologies
  • Leland gas Regulator
After the parts came in, I got to testing. The small hand pump took far too much effort and time to inflate the system to the needed pressure so that will not be the primary way to pressurize the system.

Next was to try the bike inflator with the N2 cartridges. Alas, the small cartridges leaked out way too quickly when pierced with the bike inflator for any substantial filling.

So that leaves the last option which was 18g N2 cartridges and the Leland Regulator.

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Regulator with KQ2H07-34S attached.

Since the amount of pressure in an 18g N2 cartridge is high, to the point where it can create Crescent Rose into a ticking time bomb, there needs to be a way to bleed out extra pressure if it gets too high. Since Crescent Rose takes 60psi to extend and retract once, the limit should be around that. In order to do that, a pressure relief valve is needed. I used a Norgren relief valve (PN:16-004-007)

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The pressure relief valve was adjusted for bleeding out air at 75 psi. In addition to the relief valve, there must be a way to bleed out air from the system manually. It can be done with a brass ball lever valve, a schrader valve, or a presta valve.

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Below is a lever valve.
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I used a schrader valve. This one is Campbell Hausfield 1/8" NPT Tank valve from HomeDepot (P/N: MP322900AV).

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So in order to attach these components to what is there already, a brass cross fitting is needed.

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To attach tubing to it all, a push fitting is used (PN:KQ2H07-34S).

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All the fittings were wrapped with teflon tape and attached like so.

The Leland regulator was then attached to Crescent Rose via velcro, hotglue, and zipties. Tubing was then run from the above setup to the regulator.

Now to test the whole thing.

Works well.

Future possible improvements:
-Change material of the claw
-Replace the 3-wire Vex motor with a 2-wire Vex motor.
- Fix the leaks
-Find a better air source.

Quality of life changes here.

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