First Sterling Finally Running

Discussion on Stirling or "hot air" engines (all types)
mhafele
Posts: 16
Joined: Sun Oct 08, 2017 10:27 am

Re: First Sterling Finally Running

Post by mhafele » Tue Nov 28, 2017 7:04 am

Ian S C wrote:That's excellent speed, just needs a bit of engineering to redesign the hot end. If you haven't broken something, you are not really trying hard enough, the hot end probably needs to be brazed into the flange, what is the hot cap made of?
Ian S C
Hot cap is mild steel tube turned down to make it thin. I tig welded the end cap on. I tried to braze the end cap but it got so hot the braze would drip off. Right now I'm trying some jb weld extreme heat crack sealer. So far so good. Seems to be kind of a ceramic material that holds up to 2400F. Looks ugly and slopy though. To do it right I might remake the hot cap flange and tig that on to the tube. Its aluminum now because I had the material on hand. Kind of nervous to tig material that thin.

Sent from my SM-N950U using Tapatalk

Ian S C
Posts: 2137
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: First Sterling Finally Running

Post by Ian S C » Wed Nov 29, 2017 3:56 am

At first I made hot caps from solid stainless steel, bored out in a cup shape, the displacers were made in a similar way but from mild steel. Newer motors have the hot cap made of thin walled stainless steel tube (0.010"/0.25 mm or less), with the end TIG welded in place, and a mild steel flange brazed on the hot cap, and an aluminium plug held in place with high strength/ high temperature Loctite. I'v got a tame TIGger who dose the welding for me, some of the displacers I made hade a thickness of 0.007", he didn't like that.
Below is one of the hot caps made from solid, it has an internal thread to screw onto the rest of the cylinder of a BETA motor.
Ian S C
[img]
Copy of Image001.jpg
Copy of Image001.jpg (28.9 KiB) Viewed 982 times
[/img]

mhafele
Posts: 16
Joined: Sun Oct 08, 2017 10:27 am

Re: First Sterling Finally Running

Post by mhafele » Sat Jan 06, 2018 2:35 pm

mhafele wrote:Runs good with propane torch. Any tips on running with less heat? Or how to get it to run longer without over heating?

Image

Sent from my SM-N950U using Tapatalk
Number 2 running, Vertical Fan, 400RPM

[/img]

Sent from my SM-N950U using Tapatalk

Ian S C
Posts: 2137
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: First Sterling Finally Running

Post by Ian S C » Sun Jan 07, 2018 2:41 am

On the top motor you might be able to put a fan driven by the engine to blow across the power cylinder, it doesn't take much air movement to move quite a bit of heat. You might be able to fit a pulley beside the flywheel. That is the main draw back with that design of motor, no plain shaft sticking out to drive anything. Once you get it running on gas, see how much you can turn down the flame, also direct the flame across the motor, keep it away from the cold end. You could try Meths.
The fan motor, have you tried it on a stove(electric or gas), or a log burner, it should go well, and you won't need to use the G clamp.
Ian S C

cbstirling2
Posts: 143
Joined: Sat Dec 17, 2016 9:35 pm

Re: First Sterling Finally Running

Post by cbstirling2 » Sun Jan 07, 2018 8:54 am

6500 rpm that's too fast imho.
I recommend placing a load on it to see how many watts you generate.
Do this set up: hook up a electric generator (a low voltage motor) via a rubber band belt.
Send its power to a lower voltage motor. If the generator is AC, send it thru a bridge rectifier.
Measure the voltage off the generator and the amps being sent to generator load.
Now you know the watt output of your engine. For a toy, getting near 1 watt is impressive.
CBStirling2

Ian S C
Posts: 2137
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: First Sterling Finally Running

Post by Ian S C » Tue Jan 09, 2018 3:17 am

Another thing you can try, drive the motor in it's normal direction , you can use a rubber tired wheel in an electric drill against the flywheel, get it going about as fast as it normally goes, or faster if you feel its ok, after a few minutes feel the end of the hot cap, it should be getting quite cool, maybe even some frost on it, that horizontal motor of yours should be able to go to -20*C with an ambient temperature of +20*C, it might take twenty minutes or so, this demonstrates one of the main uses Stirling Engines have had over the last 60/70 years.
Ian S C

mhafele
Posts: 16
Joined: Sun Oct 08, 2017 10:27 am

Re: First Sterling Finally Running

Post by mhafele » Wed Jan 10, 2018 4:59 am

Ian S C wrote:On the top motor you might be able to put a fan driven by the engine to blow across the power cylinder, it doesn't take much air movement to move quite a bit of heat. You might be able to fit a pulley beside the flywheel. That is the main draw back with that design of motor, no plain shaft sticking out to drive anything. Once you get it running on gas, see how much you can turn down the flame, also direct the flame across the motor, keep it away from the cold end. You could try Meths.
The fan motor, have you tried it on a stove(electric or gas), or a log burner, it should go well, and you won't need to use the G clamp.
Ian S C
Stove top was the intent just haven't tried it yet. I used a 20:1 volume ratio. If I used a smaller ratio would I get a higher rpm?

Sent from my SM-N950U using Tapatalk

Ian S C
Posts: 2137
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: First Sterling Finally Running

Post by Ian S C » Thu Jan 11, 2018 1:14 am

With the twenty to one ratio, the motor will run on a lower temperature. I stick mine on the electric stove evert now and then while I cook my lunch, or put the LTD motor on top of the pot of vegetables while they cook.
Ian S C

mhafele
Posts: 16
Joined: Sun Oct 08, 2017 10:27 am

Re: First Sterling Finally Running

Post by mhafele » Sat Jan 13, 2018 7:55 pm

Ian S C wrote:With the twenty to one ratio, the motor will run on a lower temperature. I stick mine on the electric stove evert now and then while I cook my lunch, or put the LTD motor on top of the pot of vegetables while they cook.
Ian S C
Starting to design #3. Want to try vertical again with a 5:1 ratio to get more rpm on fan. At what point can you get away with no cooling section on displacer cylinder? Just a steel displacer cylinder with a aluminum plate on top for cool end?

Sent from my SM-N950U using Tapatalk

Ian S C
Posts: 2137
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: First Sterling Finally Running

Post by Ian S C » Sun Jan 14, 2018 2:21 am

Depending on your heat source, you should be aiming at getting nearer to the 1.5 : 1 ratio that is considered the optimum ratio as used by Robert Stirling over 200 years ago.
Ian S C

Post Reply