Miniature spring air brake chamber?

[nf6x]

I'm brainstorming a possible truck modification in which it'd be handy to have a pneumatic actuator that works just like an air brake spring canister, but is smaller and has lower actuation forces. The actuator would need around 1"-2" of travel, push out the actuation rod under spring pressure, and pull in the actuation rod by air pressure. I think that a normal spring air brake canister would both be too large and apply too much force, as I've read that the spring force is up in the thousand(s) of pounds.

It seems to me that there's probably something like that out there which is intended for vehicular use on thongs like wreckers, but so far I haven't figure out how to search for it online. My favorite industrial supplier (McMaster-Carr) carries air cylinders with spring return, but the spring acts in the wrong direction. I could use a plain air cylinder with an external spring, but a spring-loaded diaphragm actuator made for truck use (i.e., actuating things like locking pins) would be ideal.

Do any of y'all know A) if such things already exist, and B) how I would search for them?

The modification that I'm contemplating is adding air actuators to the pins that secure the bottom ends of the boom shipper braces on my M936A1 wrecker. One of the things that I've found to be inconvenient when operating without "Soldier B" is that it's a hassle to get those locking pins in or out. I need to operate the crane controls to line up the holes and to take load off the pins before pulling them out. The driver side pin is a little hard to reach from up on the bed, and the passenger side pin is even harder to reach because the box over the winch controls gets in the way. So, I envision adding actuators to them which push the pins into place under spring pressure (to be fail-safe when driving), and pull them out under air pressure.

 

[303rdGLCM NM]

Not owing or being around a wrecker, is it something that could be done with a bungee cord. I used to use the black rubber cords on the farm to help with unhooking implements form the 3 point hitch by myself.

 

[nf6x]

Bungee cords might help. Thanks for the suggestion.

 

[doghead]

http://www.mpja.com/Air-Cylinder-Bimba-Single-Action-Spring-Loaded-USED/productinfo/8849%20HD/

 

[nf6x]

The link didn't work on my phone. I'll try it on my laptop after lunch.

Which way does the spring go? The Bimba cylinders that McMaster carries all have the springs going the wrong way.

 

[Derrickl112]

I like the idea! I usually leave the support bars attached on the lower end, and unpin them from the boom. It's a lot easier to reattach them by yourself.

 

[doghead]

Spring out, air retract

 

[doghead]

That is how I do it as well, Derrick

 

[nf6x]

I have been I unpinning at the bottom so they stow out of the way on the boom When I reattach them, I find it easier to pull the T pins to let them telescope, pin the bottoms, then adjust the boom until the T pin holes line up. Working by myself, it is easier to line up the T pin holes than the bottom pins.

 

[doghead]

I usually work alone too.

I find I can install one top, then swing just a touch and install the other one. Might take 2 or 3 tries average.

I have no rear winch(m819), so my legs lay pretty low and out of the way(toward the rear).

 

[nf6x]

Ok, the link works on my laptop. That particular cylinder is too small, but just knowing that Bimba also makes them with spring-extend and air-retract is helpful. Thanks!

 

[Junkyard Wars Crusher]

An industrial pneumatic cylinder is the device you describing. As doghead suggests, Bimba Mfg. is one possible supplier. Others are Parker Hannifin, SMC, Festo, Norgren, PHD, Fabco-Air, . . . .

These are common devices in all kinds of industrial equipment and factory automation systems. There are thousands of bore and stroke combinations. The stroke is how far the rod moves in or out. You dictate the force by multiplying the bore of the cylinder (area) x the air pressure.

Most are double-acting. That means they use air pressure to extend and air pressure to retract usually controlled by a valve. There are also single acting, which is air pressure to extend, and an internal spring retracts when the air pressure is removed. The least common, ( but what you are requesting) is called Reverse Single Acting - An internal spring extends the rod in the default position, and when air pressure is applied, the rod retracts.


Edit: I sure need to type faster, looks like you were able to open the Bimba link and discover the Reverse single acting.

 

[jw4x4]

You may be able to expand by searching for air actuators.

 

[nf6x]

Air actuators was one of the things I tried before posting. I was mostly getting ones that were configured to actuate valves.

 

[Hoefler]

Check out BIMBA air cylinders. They have a decent online site. I think they have both styles of spring type pneumatic cylinders.
Also check out REID tool.
Pete