Search found 28 matches

by tmk
Mon Jun 25, 2007 6:23 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Help with aluminum piston
Replies: 11
Views: 11821

you're probabaly right about the piston weight thing according to this site (which sells the stuff?) http://www.apikolon.com/index.asp?page=kocetal_grade melting point is 166 C = 330 F so some heat resistance but not that much. here, 'alpha stirling' notes that the thermal expansion is the biggest p...
by tmk
Mon Jun 25, 2007 11:22 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Help with aluminum piston
Replies: 11
Views: 11821

Brass is very heavy. Weight is a big deal in the piston. Anything going one direction then having to stop and go the other direction takes a lot of energy to do that. I talked to someone who built stirlings professionaly at the Maker Faire, and (assuming i interpreted him correctly) he was saying t...
by tmk
Thu Jun 21, 2007 3:55 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: 'cookie' engine diary
Replies: 7
Views: 7098

.

thanks for the tips, i'll check into those
by tmk
Mon Jun 18, 2007 12:02 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: 'cookie' engine diary
Replies: 7
Views: 7098

.. and on to the end

I had several hours today to fiddle and tweak my engine, and although it ran, in the end it was pretty much ruined. I've been testing my prototypes out on the stove (it's nice and big so it fits over the burner like a pot), and it just wasn't happening. I'd added some weights to help it spin, and co...
by tmk
Wed Jun 13, 2007 2:40 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: stirling thermodynamics
Replies: 1
Views: 3657

stirling thermodynamics

I've been trying to figure this out for a bit, perhaps someone can clear it up for me if you have a heat source at a certain temperature, and you run it through a stirling engine to produce work, does the heat in == the heat out, or is the heat converted to work, and so you need to dissapate less th...
by tmk
Tue Jun 12, 2007 8:08 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: would a block of ice work
Replies: 5
Views: 6462

sure

i saw an engine at the maker faire which was similar to a LTD in shape, but the bottom plate was basically an aluminium heat-sink, with a block of ice frozen around it

the hot side was just the air, and it ran fine

-tmk
by tmk
Mon Jun 04, 2007 12:59 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: power producing engine
Replies: 8
Views: 9377

you mean like this general configuration:

Image

Not sure what you would need a bearing for though if you are using this type of spring.

-tmk
by tmk
Sun Jun 03, 2007 10:46 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: hybrid steam/stirling engine
Replies: 14
Views: 11470

hmm, does this make sense?

Hey so regarding this, i looked into it a bit more, and it seems that although the numbers are more impressive, it actually requires more energy per unit expansion to evaporate water vs heating air. It took 1.472 Joules to expand the water by 1cc, whereas it took .378 Joules to expand the air by 1 c...
by tmk
Wed May 30, 2007 11:16 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: hybrid steam/stirling engine
Replies: 14
Views: 11470

.. and since i like pictures

here's a picture of what one might look like http://home.comcast.net/~nufan_wfk/stirling/stirling-hybrid.gif blue stuff is water orange is the hot side flywheel not shown, but this is a crankshaft arrangement the piston on the left side would move down and displace the water (maybe it would have a s...
by tmk
Wed May 30, 2007 10:21 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: hybrid steam/stirling engine
Replies: 14
Views: 11470

math time

From the heat pump article above: Water, for instance, expands 1600 times when it vaporizes at 1 atmosphere. Some math: Working gas volume: V1 Cold side: 25 C (298.15 kelvin) Hot side: 150 C (423.15 kelvin) Thermal expansion (charles law): V1/T1 = V2/T2 So without water the normal expansion due to t...
by tmk
Wed May 30, 2007 9:57 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: hybrid steam/stirling engine
Replies: 14
Views: 11470

Thanks, here's my thinking: say quantity of water per cycle is very small, like a few drops. if the hot side is hot enough, it should vaporize pretty much on contact. I wouldn't have a lake on the hot side, as that wouldn't really be productive. I would envision a reservoir of water from which a dro...
by tmk
Tue May 29, 2007 11:36 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: hybrid steam/stirling engine
Replies: 14
Views: 11470

hybrid steam/stirling engine

This idea just occurred to me.. a stirling operates on heat difference causing pressure changes in a sealed chamber due to air expansion. But the expansion of air is only so much. The expansion of liquid->gas is much greater. what if we had our hot side at say 150 C and added a small amount of water...
by tmk
Tue May 29, 2007 8:56 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: It works!
Replies: 6
Views: 7330

polyacetal

polyacetal sounds like it'd make a great piston, but doesn't it have a really low melting point? like 120F?

Is yours a higher melting point version? Where did you get it?

-tmk
by tmk
Sat May 19, 2007 8:30 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: increasing displacer 'dwell' time
Replies: 14
Views: 12100

For reference, went to the maker faire and met a guy who used to run a company who designed stirling engines for power generation. He cleared up a few things for me, but in particular he said that it 'seemed like' changing the dwell time of the displacer should make it more efficient, and that peopl...
by tmk
Fri May 18, 2007 10:24 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: 'cookie' engine diary
Replies: 7
Views: 7098

pcitures

Here are a couple of pictures of what i have so far (click for a full-size version): http://home.comcast.net/~nufan_wfk/stirling/cookie/cookie0001-small.jpg The pistons on top are made of epoxy. The piston cylinder is glued on with superglue. You can see some chicken-wire in the background.. same st...