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joker
09-29-2008, 11:45 AM
I made a simple pop-up using a bicycle pump and it works great. I used heavy duty springs as limiters and to make it reset. After reading the PVC cylinder thread it got me to thinking that maybe using the pump for a cylinder isn't such a great idea.

Where can I find a reasonably priced cylinder to replace my bicycle pump? Would it be cheaper to use a 4-bar setup as oppossed to a longer stroke cylinder?

dna1990
09-29-2008, 03:56 PM
I got all mine from ebay. but monsterguts and evilusions also carry some.

Stroke up to about 10" are fairly cheap if you have some patience on ebay. However, depending on the weight of the load, a linkage of some kind may still be warranted to move it without risky bending the rod. The thicker the rod or longer the stroke, up goes the price.

True, bicycle pumps and door closers are riskier. Less on exploding like PVC (assuming pressure is reasonably low) but more on the often homemade connections. Then you have a 'whip'. Always anchor your feed lines in case something breaks lose. Always have a master cutoff valve, etc.

The bicycle pump has the most risk on shooting off past the end. The 'stop' on the upstroke is usually a thin piece of metal. You should always build in stop limits to the motion anyway.

Fetch
09-29-2008, 04:55 PM
Surplus catalogs can be a good source. Surplus Center is one I keep a regular eye on.