Help me with my LTD.

Discussion on Stirling or "hot air" engines (all types)
old-ocker
Posts: 2
Joined: Tue Nov 07, 2017 9:50 pm
Location: Australia

Help me with my LTD.

Postby old-ocker » Tue Nov 07, 2017 10:34 pm

Anyone help me with my LTD that I cannot get to work.
It is airtight - proved by removing piston and blowing into airpot and it holds pressure.
Tried a counterweight for piston and displacer - no difference.
Tried increasing weight of flywheel - 5 cent coins stuck around the edge - no difference.
Displacer and piston set at 90 degrees apart.
Hard Drive bearings inside tower are used for axle.
Other bits are from a CD drive.
Connecting rods are 2 mm brass.
Tower and airpot are temporary help in place with poster putty until I can get it to work.
Piston stroke is about 9mm - is it too much.
Are the CD drive parts too heavy.
Any suggestions.
Thanks
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Ian S C
Posts: 1983
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Help me with my LTD.

Postby Ian S C » Wed Nov 08, 2017 2:33 am

old-ocker, you might try another one or two CDs on the flywheel. Are you sure that all the angles are ok, ie the crankshaft is square to the piston, and the crank pins to the con rods, the thing that really kills thes motors is friction. Get it all right and it will work, just that they can be a bit frustrating(a big bit at times).
Ian S C
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thanh-cuibap
Posts: 149
Joined: Tue Sep 06, 2016 8:09 am
Location: Việt Nam

Re: Help me with my LTD.

Postby thanh-cuibap » Wed Nov 08, 2017 3:32 am

Hi old-ocker !
According to your image I noticed that the displacer was too short and it looked much smaller than the cylinder
can you tell:
the inner diameter of the cylinder and the diameter of the displacer ?

Ian S C
Posts: 1983
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Help me with my LTD.

Postby Ian S C » Wed Nov 08, 2017 5:53 am

For a LTD motor the displacer looks ok, could perhaps have a little less clearance on the diameter, my one has about 1/4"/6 mm clearance, the bore of the displacer is about 160 mm. The flywheel is a ring cut from the edge of the top plate of the motor, the spokes are made of bicycle spokes glued into an aluminium hub. Top and bottom plates were made from aluminium frying pans, top 5 mm thick, bottom 3.5 mm thick. Piston, and cylinder are cast iron. This all works well on a bowl of boiling water.
Ian S C

old-ocker
Posts: 2
Joined: Tue Nov 07, 2017 9:50 pm
Location: Australia

Re: Help me with my LTD.

Postby old-ocker » Wed Nov 08, 2017 6:52 pm

Hi
Thanks for the replies.
The displacer has a clearance of 5mm.
Is this critical ?
The displacer is 7mm thick.
Is this critical ?
Top and bottom plates are 160mm.
I have only tried with hot water so I will try with boiling water to see if I can get it working.
As a last resort I will make a metal flywheel.
Thanks again.
Frank

thanh-cuibap
Posts: 149
Joined: Tue Sep 06, 2016 8:09 am
Location: Việt Nam

Re: Help me with my LTD.

Postby thanh-cuibap » Wed Nov 08, 2017 7:28 pm

Hi old-ocker !
I think
clearance : Depends on big or small cylinder . my LTD : inner diameter of the cylinder: 89 mm and the diameter of the displacer : 86 mm , The displacer is 8 mm thick
With power piston : you can try with a more short stroke or reduce diameter cylinder
you can try with boiling water
With power piston : it must be air tight-BUT: must move gently
And : Reduce friction in parts

Ian S C
Posts: 1983
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Help me with my LTD.

Postby Ian S C » Thu Nov 09, 2017 2:35 am

The clearance in the displacer is not critical (I suppose it might be if you need every thing 100% perfect). I'm not sure what the top and bottom clearance is on mine, its probably about 3 mm. My one has ball bearing races on the big ends of the con rods as well as the main bearings on the crank shaft.
Ian S C


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