Hi Temp Bellows

[mastrovetraio]

Sorry for my poor english, I' Italian. Well, I have finded some silicone bellows, can withstand a continuus working themperature of 300° C. I need some advice of how to make an Alfa Stirling with them. I have some rough idea, but prior to spend precious time (and money too) ....... The dimensions of the big one are 13 cm external diameter, 8.7 internal. Minimum height is 6 cm and the maximum is 22 cm (nomal extension, not full)
The two little bellows are 8 cm external diameter, 5 cm internal. Minimum height is 4 cm, maximum is 15 cm.

[burnit0017]

Greetings, notice the large water cooling jacket. I look forward toward your results.

[Bumpkin]

Hi mastrovetraio. I wouldn't expect much power or speed, but those could sure make a bright demonstration engine. I made a model {not an Alpha} from a car shock-absorber bellows, and some observations: You don't need a wrist-pin joint, but if the bellows extends very far, the top will flop around unless it's supported laterally. A swing-arm of some kind would probably work, but I just used a short enough bellows stroke that it remained (somewhat) stable. You can cut numerous short bellows from one long one if you want. You can make a plug of some sort to fill the bottomed-out dead space. The problem with an Alpha is you have moving parts on the hot side. 300 C is still a relatively low-temp engine - allowing for a bit of safety margin it would only be about a 1.6/1 ratio (absolute) above ambient temperature, so the displacement ratio should be less than that. Most working engines of that temp ratio would be a Gamma design, but I'm sure an Alpha could be made to work with the right displacement ratio. Remember to account for dead-space when figuring displacement ratio. By the way, I've never done an Alpha of any sort, so my advice might not be worth what I'm charging for it.
Good luck on your project.
Bumpkin

[Bumpkin]

I just saw the picture in your introduction post. Beautiful glass work. To my mind, artistic expression is one of the Stirling engine's strong points. Magic and beauty. A lot of potential there.
Bumpkin

[vamoose]

Those are nice looking bellows mastrovetraio,

Where did you get them?
I am interested in obtaining some high temp silicone bellows like this.
Even bigger ones would be nice eg. 200+ mm would suit my current project...
Could you tell us where you obtained yours from?

Thanks
vamoose

[mastrovetraio]

@ Vamoose I bought them in Italy, where I live. http://www.barbierigomma.it/Catalogo/Pr ... fault.aspx I've searched for "alimentary rubber bellows" why I was wondering that alimentary silicon can whitstand temperature. And I was right. But the bigger diameter I find is 13 cm.
Bumpkin Thank You. You have confirmed all my thoughts. Here is a poor sketch of my idea, the height of the refractory i exsagerated, it will depend from some experiment under pressure that I will do for understand the maxximum possible extention/pressure. I've not designed the regenerator, but it's obvious it will stay between the two bellows. I think that this opposite configuration will reach a good efficiency, BUT at the cost of a very complicated transmission assembly (dented pulleys, dented rubber chain ecc.) What do you think ??

[Bumpkin]

Hi mastrovetraio. The linkage could be quite simple; a normal crank with three throws, the center driving one end and the other two far enough outboard that the rods bypass outside the bellows to drive the other end. There may be good reasons to do it another way though. There are a few opposed Alphas on this page: https://www.nmri.go.jp/eng/khirata/stir ... /home.html
Bumpkin