Search found 113 matches

by derwood
Sun May 14, 2017 8:05 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Pressurizing a free piston stirling with a spring or rubber bands?
Replies: 8
Views: 3342

Re: Pressurizing a free piston stirling with a spring or rubber bands?

You would need to use a fairly long spring in order to keep a constant even tension. I considered this a couple of years ago but never tried it. I think it would work
by derwood
Sun May 14, 2017 6:41 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Pressurizing a free piston stirling with a spring or rubber bands?
Replies: 8
Views: 3342

Re: Pressurizing a free piston stirling with a spring or rubber bands?

You could possibly pressurize the engine internally and use a spring to simulate external pressure.
by derwood
Mon Apr 17, 2017 1:56 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Power producing low delta T state of the art?
Replies: 11
Views: 6855

Re: Power producing low delta T state of the art?

Must be a top secret company. no link for the public to see.
by derwood
Mon Jan 23, 2017 9:45 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Multiple tube Thermal Acoustic engine
Replies: 11
Views: 3742

Re: Multiple tube Thermal Acoustic engine

I noticed an error in my last post. It should read 1500 strokes per/min.
by derwood
Mon Jan 23, 2017 1:15 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Multiple tube Thermal Acoustic engine
Replies: 11
Views: 3742

Re: Multiple tube Thermal Acoustic engine

Ive made some changes to the engine. It seems that the heating is so much more efficient that I have been able to greatly increase compression. approx. 1 : .75 , lowering compression does not increase stroke length. Currently Piston 3.35inch diameter, stroke 4inches, 3500 strokes per/min free piston...
by derwood
Sun Jan 22, 2017 6:57 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Multiple tube Thermal Acoustic engine
Replies: 11
Views: 3742

Re: Multiple tube Thermal Acoustic engine

What inspired the multitube design? I thought your tube within a tube design to be very clever. Is there elements here? I have a flame licker that doesn't run well, thinking of converting it to a thermo acoustic. Is there literature on the tube ratios and such? The tube within a tube design ran wel...
by derwood
Sat Jan 21, 2017 5:07 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Multiple tube Thermal Acoustic engine
Replies: 11
Views: 3742

Re: Multiple tube Thermal Acoustic engine

Clever. Does the heat need to be concentrated at one end of the tubes? I wonder if a wood fire could be applied along the tube heat exchanger. What watt output does it have? How long can it run? (Gives clues how well it dumps heat.) I wonder how much better it would run with cooling fins (with belt...
by derwood
Sat Jan 21, 2017 10:44 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Multiple tube Thermal Acoustic engine
Replies: 11
Views: 3742

Re: Multiple tube Thermal Acoustic engine

I am going to make some changes to the tail end. It uses 29 stainless steel .25 inch tubes welded on each end. The hardest part is to weld the tubes without air leaks. I tried to mig weld the tubes but could not get leak free welds. Tig welding was the key. Thanks for the interest.
by derwood
Fri Jan 20, 2017 5:35 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Multiple tube Thermal Acoustic engine
Replies: 11
Views: 3742

Multiple tube Thermal Acoustic engine

This is just a first test of a new Engine I have designed. The heat source is small but it runs quite well with just a small pencil torch.

[youtube][/youtube]
by derwood
Thu Jan 19, 2017 4:27 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: generators
Replies: 32
Views: 9486

Re: generators

Video?
by derwood
Wed Jan 04, 2017 10:22 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Alpha type stirling engine Problem
Replies: 8
Views: 3012

Re: Alpha type stirling engine Problem

cbstirling2 wrote:Ian, what do you think is a lifetime of a graphite piston? What about Teflon?
If your cylinder walls are smooth the piston will last a very long time. Ive been using the same piston for years. It is also very easy to machine.
by derwood
Mon Jan 02, 2017 6:52 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Alpha type stirling engine Problem
Replies: 8
Views: 3012

Re: Alpha type stirling engine Problem

You need to replace those pistons with graphite pistons.
by derwood
Thu Dec 22, 2016 3:06 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Thermal lag plans
Replies: 7
Views: 3862

Re: Thermal lag plans

I just purchased a tig welder and as soon as i learn how to use it i will try some multiple tube designs. I am currently practicing welding .25 inch ss tubing.
by derwood
Thu Dec 22, 2016 2:50 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Thermal lag plans
Replies: 7
Views: 3862

Re: Thermal lag plans

I based it on a video posted here a while back. The member who posted the vid was Geoff V. It was a much smaller version but he never provided any dimensions. Through trial and error I managed to produce a larger version.
by derwood
Tue Dec 20, 2016 3:49 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Thermal lag plans
Replies: 7
Views: 3862

Re: Thermal lag plans

The gap between the inner and outer tube is the stack. The inner tube is for expansion. The gap between the inner and outer tube needs to be as small as possible without restricting flow.