It will not run.

Discussion on Stirling or "hot air" engines (all types)
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nigelhitmiss
Posts: 4
Joined: Sun Jan 21, 2007 9:51 am
Location: Missouri

It will not run.

Post by nigelhitmiss » Sun Jan 21, 2007 10:06 am

I just finished building the "Moriya" Stirling fan. I aso have built the mini propane burner with plans ordered from Jerry Howell.
I can't get it to run after considerable effort.---- With the plug out of the drill chamber (to relieve compression) it spins very freely. I am not sure as to the amount of heat it needs to operate. I have adjusted the timing relationship between displacer and power pistons. I have displacer piston leading power piston by 90 degrees.

All and any help would greatly be appreciated. TJ
Missouri
TJ

SScandizzo
Posts: 66
Joined: Tue May 16, 2006 5:06 pm
Location: California

Post by SScandizzo » Mon Jan 22, 2007 10:21 am

Hi TJ,

First thing I would do is take a look at the thread "little machine shop walking beam engine" because its about another engine that isn't (as yet) running. There are quite a few tips there to try. The only thing I will repost here is DO NOT over heat the engine. If it is not running with the appropriate amount of heat, applying more heat will only risk damaging your work. If possible, please post some pictures and a detailed description of what the engine is doing and we'll try to help you out!

-Stefan

nigelhitmiss
Posts: 4
Joined: Sun Jan 21, 2007 9:51 am
Location: Missouri

Post by nigelhitmiss » Mon Jan 29, 2007 8:33 am

I have posted a photo of the problem engine on American Stirling forum. It is labeled "problem engine" dscn2150.jpg TJ
TJ

SScandizzo
Posts: 66
Joined: Tue May 16, 2006 5:06 pm
Location: California

Post by SScandizzo » Mon Jan 29, 2007 11:34 am

Here's the direct link to see the picture:

http://www.stirlingengine.com/file-stor ... ion_id=355

Wow, that's a big boy!

Ok, so you mentioned that you do have compression and that the engine turns freely when the plug is removed. I'm still willing to bet that there is an air leak somewhere in the system. I'm basing this on a couple of thoughts: the engine is a "commercial" design, so we know the dimensions are reasonable, and this model appears to be well constructed, so I'll take your word that there is low friction.

That pretty much only leaves leaks. When you do use the burner, does the output shaft seem to turn almost freely? The best way to search for leaks is to put small drops of oil around any inside/outside interfaces such as the walls of the power piston and cylinder and the displacer shaft bushing. Sometimes this is enough to seal small leaks. Other times it will reveal air moving about in the form of very small bubbles.

Chin up, we should be able to get it running!

-Stefan

Henrik
Posts: 10
Joined: Sun Dec 10, 2006 1:58 pm

Post by Henrik » Mon Jan 29, 2007 2:50 pm

How high are the displacer. After what I can see is that your displacer must be about 2/3 of the total chamber height, because of the short stroke of the displacer. You must be sure that the displacer goes all the way from bottom to top to gain max performance.

but nice piece of work you have do there.

-Henrik

nigelhitmiss
Posts: 4
Joined: Sun Jan 21, 2007 9:51 am
Location: Missouri

Post by nigelhitmiss » Mon Jan 29, 2007 5:32 pm

The crankshaft turns very easily when spun. It always ends spin with displacer at the bottom. I put a tiny bit of oil on power piston/cyl and the displacer gland. No leaks. ???????? I will make a fitting tomorrow so I can put a tiny bit of pressure in it to check for leaks. TJ
TJ

SScandizzo
Posts: 66
Joined: Tue May 16, 2006 5:06 pm
Location: California

Post by SScandizzo » Tue Jan 30, 2007 10:38 am

TJ,

If possible, place a counter balance on the fan so that the displacer stops at a random position every time you free-spin it. This will help balance the engine and prevent it from stalling at low speeds (such as start-up). Also, with low heat and the system closed, try spinning the fan. Does it spin almost freely, or does it try to spring back to its starting position. The fan should be easier to spin as the engine heats up. If it isn't, it could mean that there is positive pressure inside the system (due to heating the air) thus favoring the piston in the bottom position.

-Stefan

nigelhitmiss
Posts: 4
Joined: Sun Jan 21, 2007 9:51 am
Location: Missouri

Post by nigelhitmiss » Fri Feb 09, 2007 7:19 am

I finally got back to this engine. I never did get it to run. Would anyone have any new ideas. It sins very freely and I checked for air leaks with soapy water. Never found any. How do I know if I have enough heat? I'm using the small propane burner made from Jerry Howell's plans. Flame is about 1 -1/2" and yellow.

TJ
TJ

SScandizzo
Posts: 66
Joined: Tue May 16, 2006 5:06 pm
Location: California

Post by SScandizzo » Fri Feb 09, 2007 11:40 am

TJ,

When sealed, the engine should "bounce" back when you try to spin the fan/flywheel. Does it do this? If so, does this bounce become less pronounced when you light the burner?

If that "bounce" is diminishing, it means that the engine wants to run, but may need more heat/better cooling on the other side.

-Stefan

stanhbaker
Posts: 33
Joined: Wed May 31, 2006 5:14 pm
Location: KnoxTn

It will not run.

Post by stanhbaker » Sun Mar 11, 2007 11:59 am

When you bring the engine up to dead center and hold it in that position, how long does it take for the pressure to dissapate and the blade stay there?
If it takes more that 10 seconds the engine is most likely too air tight.

First be sure there are NO leaks anywhere in, on, or about any part of the engine EXCEPT a the packing gland. The packing gland is usually the easiest point to adjust for a tiny leak sufficient for the engine to "breathe" as breathe it must in order to run at all. The average or mean pressure must be the same as the surrounding atmosphere. Otherwise on initial heating the engine becomes pressurized by the heat and consequently air bound.

Stirling engines without a pressurized crankcase must have a leak, albeit, a tiny one to operate at all.
Why be difficult?.. When with just a little application you can be absolutely difficult!

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