Glass and graphite piston sets

Discussion on Stirling or "hot air" engines (all types)
Cartech
Posts: 99
Joined: Mon Oct 30, 2006 11:26 pm
Location: Northern Nevada

Glass and graphite piston sets

Post by Cartech » Thu Nov 02, 2006 8:22 pm

I'm sure it's been posted here before but here is a link for production cylinder sets of glass and graphite. http://www.airpot.com/ look under the specs tab. They have many sizes and the smaller ones run under 20.00 USD per set. Sure easier than making your own! I'm not posting this as advertizing, just to let others know they can be bought. I ordered some today :)

theropod
Posts: 19
Joined: Thu Mar 08, 2007 7:57 pm
Location: N.C. Arkansas

Re: Glass and graphite piston sets

Post by theropod » Fri Mar 09, 2007 7:10 am

[quote="Cartech"]I'm sure it's been posted here before but here is a link for production cylinder sets of glass and graphite. http://www.airpot.com/ look under the specs tab. They have many sizes and the smaller ones run under 20.00 USD per set. Sure easier than making your own! I'm not posting this as advertizing, just to let others know they can be bought. I ordered some today :)[/quote]

Hi,

Can you please provide us with an update of how this parts combo worked out? I am considering ordering the .945" id set myself and would like to know your results good bad or otherwise.

Thanks,

Roger
7 years off-grid and loving it!

Cartech
Posts: 99
Joined: Mon Oct 30, 2006 11:26 pm
Location: Northern Nevada

Work great!

Post by Cartech » Fri Mar 09, 2007 9:08 pm

I bought two of the K240 (I think it had a "K" in it) sets. I used one set on my second engine that you can see here http://nevadasteve.tripod.com/whatsstev ... s/id1.html It worked very well. I even dropped one of the pistons and distorted it a little, I sanded it back to shape with 400 grit sand paper then cleaned it with alcohol. I was going to use my back up set for the final build of this engine but the repaired piston worked so well and didn't leak air so I used it. You will have to make your own connecting rod mount and that is probably the hardest part. Airpot has connecting rods if you surf their site but I'm not sure which ones you can get from them if any. I orded mine 1.60" long BTW. Good luck.

theropod
Posts: 19
Joined: Thu Mar 08, 2007 7:57 pm
Location: N.C. Arkansas

Graphite N Glass

Post by theropod » Sat Mar 10, 2007 6:27 am

Steve,

I'm working on the walking beam design and havin' all kinds of problems with the power piston running smooth enough. These parts from Airpot seem to be just what the doctor ordered.

I am concerned about the connecting rod attachment. Can that graphite piston take any type of adhesive or is it a machining operation?

Thanks again,
Roger
7 years off-grid and loving it!

Cartech
Posts: 99
Joined: Mon Oct 30, 2006 11:26 pm
Location: Northern Nevada

Post by Cartech » Sat Mar 10, 2007 8:35 pm

Roger,

You will get a piston with a hole in it like you see on the specs page at Airpot. I attached a piece of thin sheet metal bent like a letter "U" and drilled a hole for a wrist pin. (piano wire from hardware store) I soldered a nut on the bottom of the "U" and used a screw through the piston hole to secure it. Don't over tighten and use a "lock tight" product to keep it secure. Try to keep the fit of the wrist pin close or it will "knock" considerably. I invested in a set of very small drill bits and I have a good bit gauge to help select the right size. A drill press also helps alot. I tried a "ball" socket type pivot and it worked well and was quiet but it allowed the piston to spin and find "tight" spots. The problem was trying to keep the home made ball socket "true" in the center of the piston as it spins around. I use a R/C car wheel bearing for the other end of the connecting rod. Alignment of my connecting rod is critical. A more basic connecting rod wouldn't have these problems. Having some of those little alcohol pads from a first aid kid handy is great for cleaning the piston and cylinder after you have been working with it. Airpot has a wonderful product for a Stirling piston but it is a little hard to work with unless you have a delicate touch.

theropod
Posts: 19
Joined: Thu Mar 08, 2007 7:57 pm
Location: N.C. Arkansas

Piston Hole

Post by theropod » Mon Mar 12, 2007 7:23 am

OK,

So the piston comes predrilled with a center hole? My current piston, a loser for sure, has a very short length of 1/8" brazing rod thru the center hooked to a VCR bearing/hub, and then to the rod then to crank via another VCR bearing/hub. This arrangement doesn't bind side to side during travel of the power piston, but neither is it as smooth as need be during that travel nor do I feel It makes a good seal.

What if the power piston/cyl were sealed as are the displace and the power cylinder air was pumped from both in from the front of and from the backside of the power piston. One power cylnder end feed the cool side and one the hot side of the displacer. Would that work?

Now, my flywheel is a harddrive with 5" platten. I jb welded a VCR pin to that, and is my crank throw, again to which VCR hub/bearings make the connecting rod joint. I balanced it for the crank pin and rods, but it needs more weight somewhere to offset the displace/rod/walikng beam arm on that side. I don't feel my flywheel is heavy enough. Would a 7.25" circular saw blade serve as a good flywheel? Since I'm looking at a complete rebuild any advice there?

Thanks again for your replies and this wonderful forum.
7 years off-grid and loving it!

Cartech
Posts: 99
Joined: Mon Oct 30, 2006 11:26 pm
Location: Northern Nevada

Post by Cartech » Tue Mar 13, 2007 10:38 pm

A power piston with each side connected to hot and cold respectively will work and there are some out there in production units I believe. To make one home built can be done but it's no doubt more difficult. I have thought about some designs that would work that way but I have not attempted to build one.

As far as a saw blade for a flywheel goes, I don't see why it wouldn't work? If you read the thread on "flywheels" you will find some good info there too. It's better to have more mass in the outter ring of the flywheel than having a heavyer disk. I've been usings disks myself and found "golf" weights added to the outter rim area work well to increase mass.

theropod
Posts: 19
Joined: Thu Mar 08, 2007 7:57 pm
Location: N.C. Arkansas

Aipot Sample Arrived

Post by theropod » Wed Mar 14, 2007 5:33 am

Cartech,

First of all thanks for the help, very informative!

I asked and got a sample from Airpot, a 2.75" long by .75" diameter snubber. This has a ball joint on each end of a 2 7/8 long rod. My goodness is it ever smooooooth! I stripped off the rubber sleeve, took off the valve, and did a few experiements. With the vent end completely blocked the piston will not travel, but unblocked the slide action is so accurate it's kinda scary. I will order one of these in dimensions closer to the specs for the walking beam design, and this power piston/clyinder problem will vanish.

I have read every single message here, so far. The thread about flywheels is indeed packed with good info. As I have limited access to tooling I'm seeking a solution to keeping the centering and roundness true, and the skillsaw blade seems to have these qualities and be within .25" of the spec diameter. I am concered with the weight of such, but maybe one of the thinner "finish" blades might be ok.

Again, thanks for the help!

Roger
7 years off-grid and loving it!

Cartech
Posts: 99
Joined: Mon Oct 30, 2006 11:26 pm
Location: Northern Nevada

Post by Cartech » Wed Mar 14, 2007 9:11 pm

Okay, just keep your fingers clear when it's running! Maybe you can use it to cut firewood? LOL, j/k

Jazz
Posts: 1
Joined: Fri Dec 28, 2012 1:16 am

Re: Glass and graphite piston sets

Post by Jazz » Fri Dec 28, 2012 1:25 am

Cartech, (or anyone else that has purchased an airpot piston/cylinder set)

You had said that you were able to get your hands on a piston/cylinder set for about 20 USD. My Canadian distributer quoted me 61 dollars or an .627" ID! Which distributor did you use? or were you able to place an order directly to Airpot?

Thanks for any help

Jasper

Ian S C
Posts: 2137
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Glass and graphite piston sets

Post by Ian S C » Fri Dec 28, 2012 2:07 am

There is/ was a site on google offering a free sample available, at least to people in USA, that may include Canada, they just ask you to specify the size needed. Ian S C

dasf444
Posts: 5
Joined: Thu Jan 17, 2013 5:38 am

Re: Glass and graphite piston sets

Post by dasf444 » Thu Jan 17, 2013 6:36 am

woo you solved my problem dude your link is too much helpful for me because i want air bearing cylinders..i was tired now to go again and again in the market for the search this cylinder..can you tell me how can i buy this cylinder and in which place??

theropod2
Posts: 147
Joined: Tue Aug 16, 2011 5:05 am

Re: Glass and graphite piston sets

Post by theropod2 » Thu Jan 17, 2013 6:01 pm


Junkie
Posts: 123
Joined: Mon Mar 08, 2010 1:32 am
Location: England
Contact:

Re: Glass and graphite piston sets

Post by Junkie » Fri Jan 18, 2013 12:38 pm

When I last used one of those airpots, I just stuck a piece of tape over the hole in the piston. Worked well, the ball joint
that's supplied with the piston is superb, no need to fashion any other arrangement.
http://www.scraptopower.co.uk My web site, Stirling engines and AE stuff.

itsme_Bernie
Posts: 9
Joined: Fri Jan 11, 2013 11:05 am
Location: Northern NJ

Re: Glass and graphite piston sets

Post by itsme_Bernie » Sat Jan 19, 2013 7:26 pm

Hey Jazz

Directly from Airpot is around 50% cheaper in my memory. I got the free sample, and purchased a few each of 2K95's and 2K160's without the piston rod. I'm not necessarily suggesting this, but that us what I did.

The pistons come with a hole right in the center.


Bernie

Post Reply