Search found 17 matches

by PKM
Wed Jan 05, 2011 11:13 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Help with liquid piston lamina
Replies: 2
Views: 3690

Re: Help with liquid piston lamina

I don't think your engine is going to work, because it doesn't have anything to store momentum (the job done by a flywheel in a mechanical rotary engine). The running engine contains two elements absent from yours- the first is simply a large volume of water. The water will act as an inertial mass w...
by PKM
Thu Dec 16, 2010 5:30 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Alpha type engine Idea/need input
Replies: 31
Views: 22414

Re: Alpha type engine Idea/need input

nobody puts the power cylinder midway between the hot and cold cylinders in Stirling. Erm... I did, and my engine runs fine. The venerable walking beam engine has the power cylinder mid-way between the hot and cold ends. I can also confirm that the power piston does exert a force on the outwards st...
by PKM
Thu Dec 16, 2010 5:51 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Alpha type engine Idea/need input
Replies: 31
Views: 22414

Re: Alpha type engine Idea/need input

Your diagram illustrates horizontal pistons moving in tandem and in derwoods diagram vertical cylinders with pistons move 180 degrees. I agree they will shuttle air but with no volume change then where is the pressure change? At the power cylinder, which can move in and out just like a conventional...
by PKM
Wed Dec 15, 2010 7:47 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Alpha type engine Idea/need input
Replies: 31
Views: 22414

Re: Alpha type engine Idea/need input

Drat, forgot my own diagram. Imagine the double-piston-dumbbell-thing and the power piston moving in 90 degree phase and I think you'll get it.
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by PKM
Wed Dec 15, 2010 7:44 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Alpha type engine Idea/need input
Replies: 31
Views: 22414

Re: Alpha type engine Idea/need input

I think I'm possibly the only person who gets the idea here... as far as I can tell, what derwood is talking about is not really an alpha or gamma type engine... the closest thing I can think of would be the "moving cylinder" types, as in this design "displacer" doesn't make sens...
by PKM
Wed Dec 15, 2010 7:17 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Photo-voltiac cells vs. free-piston stirling generators...
Replies: 10
Views: 8607

Re: Photo-voltiac cells vs. free-piston stirling generators.

You've probably seen it before, but this flexible PV sheet sounds like an intermediate step in the right direction. I think it's about the 6% efficiency mark, but costs 2-4 US dollars per watt of capacity and weighs perhaps 100 lbs/kW capacity, so could probably go on your roof without serious reinf...
by PKM
Tue Nov 30, 2010 5:28 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: My first stirling engine
Replies: 9
Views: 6512

Re: My first stirling engine

Wanting a nice smooth cylinder and piston for low friction isn't OCD, it's attention to detail :) When you are machining parts to half a thou' and making your own crankshaft balancers we can talk about OCD. Remember to post pictures of that mirror-finish cylinder!
by PKM
Tue Nov 30, 2010 5:23 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Absolute Newbissimo question.
Replies: 7
Views: 5952

Re: Absolute Newbissimo question.

Hi Zeph, I think the answers to your questions boil down to yes, no, probably not much. A stirling engine runs on a temperature difference- the bigger that difference, the more power the engine can get. Simple tin-can engines are inefficient and need a high temperature difference, and it's a lot eas...
by PKM
Tue Nov 16, 2010 10:03 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling engine to pump water in Africa
Replies: 3
Views: 5401

Re: Stirling engine to pump water in Africa

Hi Phillip, I like your plan, and it's definitely a laudable aim, this is just a "back of the envelope" calculation to work out if your plan is feasible. An engine can lift water as far as you want (in theory) but lifting large volumes is a different matter. ------------ If we assume a usa...
by PKM
Tue Nov 16, 2010 9:41 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Condensation in LTD Stirling
Replies: 5
Views: 4961

Re: Condensation in LTD Stirling

I have had this problem as well, though I thought it might be due to some residue left inside the displacer cylinder. I just leave the engine with the piston taken out if it's standing for long periods, because the condensation wasn't doing wonders for the brass piston :shock: though I haven't seen ...
by PKM
Tue Nov 16, 2010 9:31 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Design on Experiment LTD Stirling
Replies: 5
Views: 6546

Re: Design on Experiment LTD Stirling

Bigsteve, Of the factors you mentioned in your original post all but one of them seem to be design factors, not properties suitable for tweaking and iterative improvement. Reducing friction (obviously) Displacer volume (increase vs. decrease) displacer bore displacer stroke The optimal displacer vol...
by PKM
Mon Nov 08, 2010 7:30 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Plans for this one? V-cylinder type from GreenPowerScience
Replies: 7
Views: 7447

Re: Plans for this one? V-cylinder type from GreenPowerScience

Dave, I believe that engine is a fairly well-known design by Andy Ross. The design was written up in an article which you can read online here (also thanks to greenpowerscience) and he produced kits at one point. The body of the engine is a moulding- the part of the crankcase you don't see behind th...
by PKM
Mon Nov 08, 2010 7:15 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Use pneumatic actuator cylinders for a Stirling model?
Replies: 3
Views: 5031

Re: Use pneumatic actuator cylinders for a Stirling model?

If you can get a 7H (or other high number- more than a 2H at any rate) pencil, that will contain much more graphite and less clay then an ordinary HB pencil. I don't think even 7H is pure graphite but it's probably much better than a regular pencil.
by PKM
Mon Oct 18, 2010 6:50 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Ideas for Regenerator
Replies: 4
Views: 6348

Re: Ideas for Regenerator

I'm not an engineer, but the few things about regens I do know are: - Packing should have a high surface area (packed metal discs with holes or steel wool/coarse swarf are common choices). Metal is the most common choice as it's easy to shape and conducts heat well, though in theory something non-co...
by PKM
Fri Oct 01, 2010 7:39 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Sanity check: airtight displacer a bad idea?
Replies: 3
Views: 6658

Sanity check: airtight displacer a bad idea?

I've made a displacer out of a roughly 70mmx70mm section cut from an aluminium drink can with flat steel sheet glued over either end. I made the cuts neat and flat, and used plenty of JB Weld to make the join, so I suspect the displacer is now pretty much completely airtight. I know the displacer is...