Cheap stainless-steel bellows (2006-07-20)
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Here's a good source of great-quality stainless steel flexible bellows which would be suitable for a vacuum system.
Go and have a look at http://stores.ebay.co.uk/RM-Catalysts under "Exhaust flexi couplings" and you'll see a couple of these things for sale (at extremely low prices!).
They're for the exhaust system underneath cars to make flexible joints between exhaust elements. It's all made from stainless steel and cost about £4.50 (not bad, eh?). There are layers of the wire mesh on the inside and outside with the bellows in between them.
First, you have to cut off the two retaining rings on either end of the joint. Then, use a cutting disc on a Dremel tool to cut the wire mesh through around the ends of the joint. The mesh is spot-welded to the ends of the bellows inside - don't try to grind off the welds as I did, but leave a little end of wire coming out from the weld. Grab it with a pair of pliers and twist it off - this breaks the weld clean without distorting the underlying bellows too much. You should have something that looks like this.
The outer layer of wire mesh can now be slid off and kept as an ornament! Following a similar procedure for the inner piece of mesh, you end up with
And that baby in the middle is a 2" dia, 4" long, hydraulically-formed stainless-steel bellows!! There's quite a bit of movement in it too. Good enough for a flexible mirror mount or a micropositioner! The ends of the bellows are a bit messy and out-of-round so they'd have to be broached or something to round them out. You'd also have to weld/braze on some flanges to it to make connection, but it would be worth it.
Here's the best part - check out KJ Lesker (www.lesker.com) and you'll see they have an identical set of bellows (WITHOUT any flanges!). Guess what they cost? £56! And this one cost £4.50! Go figure....
Question: Why should a pair of bellows from Lesker cost £56 while the same thing costs £4.50 when it's disguised as an exhaust joint?!?
These bellows may be a bit large for most applications but luckily there is another source of cheap flexible bellows. Head over to http://www.bes.ltd.uk and look under Natural Gas -> Hoses -> Armoured and Convoluted. They have short (90cm) lengths of stainless-steel corrugated hose which looks exactly the same as vacuum bellows! I know - there's a piece on the gas meter outside the house, and it looks identical to that 20cm NW16 hose I bought a few weeks ago for £40.
