Design Project: Pneumatic Car Jack - Ideas & Info

[dhcoplin21]

I have been assigned a design project to design a pneumatic car jack by filling a cylinder with air. Any one have any ideas of how to go about finding a cylinder. Also was wanting a little basic info. on how these things work. Thanks!

 

[Danger]

You could start with any surplus store. I don't know where you are or what things are like there. Here, we have a chain called Princess Auto that has all kinds of stuff like that.
The air (actually vacuum) cylinders that I have at home are from kits designed to open a passenger door from the driver's side with a dash control. I think that the primary target market was taxis. Maybe you can call a few cab companies and see if they use them. If so, they'll probably be able to direct you to their suppliers.

 

[FredGarvin]

Check out Bimba cylinders. They are a good source. In this application, you need to be very cognizant of shaft strength. A cylinder with any appreciable stroke will most likely buckle with a car on it. Sizing the stroke vs. load is going to be the tough part.

 

[Danger]

Yeah... I never thought of this being a direct lift from the cylinder, and I sure wouldn't recommend it. There should be some sort of scissors mechanism or something in between, with a ratchet so it won't collapse if there's an air loss.
By the way, dh, does this have to be a cylinder? I ask because there is a very nice suspension bag system available for cars. The bags replace the springs (and maybe the shocks too; I'm not sure). I think that they've been used on semis for a long time, but they're now on the market for street-rodders. They show up on 'Horsepower' and 'Muscle Car' a lot on Spike TV. When I get home, I'll look up their website (can't remember the address right now) and see if there's a supplier index. Something like that has the advantages of a cylinder, without the disadvantages.

edit: Okay, I'm home now. Here's the link, but you have to register to read the performance directory. Once in it, go to 'Suspensions' and click on 'Air Bag Suspensions'.

 

[wolram]

Festo have a wide range of pneumatics, they are online, and provide
calculations for product usage , but i think lifting a car will need a big
bore cylinder, or high pressure on a small bore cylinder ,that is mechanically unsafe, without As Danger has said some intermediate mechanism.

 

[LURCH]

If you look at a store that supplies parts for customizing autos, they might have pneumatic cylinders used for suspension in low-riders. Also, I believe most public transit busses have air-shocks that allow them to "kneel" to make it easier for passengers to get in and out. These devices are (obviously) caoable of lifting the vehicles in which they are used.

By the way, dh, does this have to be a cylinder? I ask because there is a very nice suspension bag system available for cars.

Here in the 'States, there was once a gadget one could buy that replaced the car-jack with a bag of air. The bag was connected by a hose to the exhaust pipe of the auto, and running the engine inflated the bag. It looked like a pretty nice system, as this provided a jack from which the car could not fall off.

Here's a similar device;
http://rv4x4.en.alibaba.com/product/50116775/50530745/Exhaust_Jacks/Exhaust_Jack.html

 

[Danger]

Hmmm... my net went out last night, and apparently the link that I posted went with it. Here it is again:
http://www.truckstv.com/PerformanceDirectorysignin.php"

Lurch... I haven't checked on this, but I believe that Hurst makes such bags as an adjunct to the Jaws of Life, for straightening out bent vehicles and such like.

 

[traveller65]

Jack it

It just so happens that I am looking to buy such a thing. Commercially available car lifts that use gaseous media seem to go two different ways: The "balloon" type of which the air springs of some cars and trucks are a variant (another is the infamous "air jack" that uses exhaust gases), and a combined pneumatic / hydraulic variant where a converter turns air pressure into oil pressure first. Once in Croatia I have seen a purely air / air car jack used by a tire service shop, it looked a bit like an anti-tank mine. I have been unable to find the manufacturer on the Internet. The air pressure supplied by an ordinary compressor is relatively low, so jacks that use this pressure have to be fairly large. How big is the piston/cylinder assembly you are supposed to use?

 

[ray b]

indy cars use built in air jacks
they plug in a air line and up comes the car