Stirlingengineforum.com

Roger,

I really like your idea - open source design, collaborative effort, sticking to the DIY approach.

I am no expert, so can't answer your questions, but I think the power output issue is an important one to have addressed early on, i.e does the math work?

I am looking forward to watching this discussion and your progress. I am esp. interested in the gasification idea. Do you have a good resource for studying up small scale stuff here?

Kudos for starting this.

Dale.

I have sometimes considered using a propane tank as a pressure chamber. I want to someday make one with a BBQ sized tank and install it in the garage ceiling. I think the hot air in the attic and the cool garage air would be more than enough to make it run very well.

Your idea sounds good. If you want the engine to be as efficient as possible I can think of a few things you would need to optimize. It would be nice if you could make a thermal break between the hot side and the cool side. The metal tank conducts heat so well that the engine will try to equalize its temperature. A thermal break to slow this down means that less cooling is required and you have a better chance of air cooled operation.

The shape of the propane tank presents some challenges. The displacer will have to have a similar shape as the end of the tank in order to displace the air.

You could use a steel wool displacer if you wanted it to act as a regenerator. There is a regenerator discussion going on this week at the Stirling engine forum on Yahoo Groups. The winning recommendation there was to use copper pot scrubbers from the grocery store as the core for the regenerator.

Another way to get more horsepower from a Stirling is to use helium in the pressure chamber. It is relatively cheap and easy to come by. It makes a noticeable improvement in performance when used in my small models. You have to get serious about stopping your leaks if you plan to run it on helium for long.

I think that scaling up is a great idea. I would encourage you to think about something that could be powered by solar energy rather than a flame. Someday I am going to scale up my low temperature differential models just to see what they can do with sunlight.

Jim Larsen
[url]http:stirlingbuilder.com[/url]

The problem with bigger engines is to heat or cool the air in the middle of the lets say a propane tank. Air next to the metal will be hot or cold, but not in the middle. Maybe try a very large area with a very short stroke or a small area and a long stroke.

Keep in mind I could be wrong :D

theropod2

Please keep in mind I only build 1 walking beam :D I`m not an expert :D
In order the make a stirling bigger and powerfull you must make the delivery of heat and cold
to the air inside more effective than a simple hotcap.
Please read the next journals of people before you:

http://ntrs.nasa.gov/archive/nasa/casi. ... 016056.pdf (nasa guys)

http://journals.tubitak.gov.tr/engineer ... -98073.pdf (failed engine)

http://www.stirlingmotor.com/buecher/bp ... ch_500.jpg ( 300watt)

http://www.nmri.go.jp/eng/khirata/stirling/index_e.html (see the ecoboy for ideas)

http://www.oldengine.org/members/orrin/lnk_stir.htm (not all links are working)

As you can see after reading all this, there are engines with 30 watt with poor design or
engines with 300watt with better design.

In my mind there are 4 problem area`s to make a good design:
1 - heat/cold delivery to the air inside
2 - low dead space area (unswept volume), this strongly contradicts with point 1
3 - low mechanical loss (bearings ,piston seals e.d.)
4 - low gas flow friction, this contradicts again with point 1

I know you`re just making a bigger walking beam and maybe it will work to get power from it.
You only know after you build it, so please do !

Have you worked on your project yet.

I am interested in a larger (more torque) engine

The small ones are interesting. Some are beautifully machined, but I want one I could do a little something with (1/4 to 1/2 HP)

Hi
Just some toughts.
I would love to see a walking beam this size.
The volumen of the displacer will be around 130 times the org.
Stroke about 40cm.
Walking beam lenght: 3meter?
Height of frame ??? WOW!
Power cyl. and piston will be large,following the org. proportions.
But whats wrong with large ?!
Try to imagine the size of the flywheel,beam,rods..and everything moving.
It wont go fast,but mayby enough torque to drive a generator (with gearing)
(But what a great "Steampunk" project.)
Jan
Ps.
The domed top/end is ideal.
More surface area=more heat/cold transfer.
Better flow of air between displacer/tank.
The displacer top/bottom should fit the shape of the domes.
See this displacer:
http://www.stirling.dk/?Technology:Biom ... ng_Engines
PPS:100 lb tank,48.5"x14.6" ?

see this:http://www.youtube.com/watch?v=mjFbi_dJT6U