Sterling Diaphragm Engine

[Trevor]

Nearly finished the radiator for the Hot air engine. Looks great and have used this idea before but only with a baby model not this large.
The heat sink with its cooling fins come from an old 12VDC cooler. The fan runs on 12v and draws 190ma. The generator I have for the engine puts out 12VDC at 1.3Amps. It is going to be a good guesse to see if the engine will run all this.
Hope it works. Trevor

[Trevor]

Have just finished the crankshaft and fitted the bearing blocks into their seats.
Don't let anyone tell you that crankshafts are easy to make - THEY AREN'T I had a hell of a time getting it straight after silver soldering it. I think there was to many cranks. At least it is done and straight now. Will be fitting the condors next and making the water pump drive including the generator.\Trevor

[Ian S C]

A simple way of making straight crankshafts. Thread the crank webs onto the main shaft, don't cut it, space out the webs, fit a shaft through the two outside pairs of webs, don't cut. Fit the crankpin in the center pair of webs, set the angles of the cranks. You can use silver solder, but high strength shaft lock Loctite will do the job. After the adhesive has cured (24 hrs), cut the surplus steel from the cranks.
A better design for your crankshaft: the center crank webs should be made in an L shape, and for the other cranks only require one web, the other being incorporated in the L shape of the center crank.
Try and keep the bearings as close together as possible, this will help to stop the shaft from flexing.
Ian S C
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Simple Crankshaft.jpg (66.46 KiB) Viewed 10373 times

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[Trevor]

I have just fired up my Diaphragm engine for the first time today - After 30 seconds of heat the engine started to turn. Whoopeeee!!!! I am stoked.
With the heat turned up to moderate I had the engine spinning over at 1100 rpm. Hardly any noise except for the water pump as it is gear driven and since it is a gear pump she was pushing the water through the radiator. I have not fitted the generator yet as I haven't had time to make the pulley for it. That will tomorrows job with luck.
I must admit I didn't expect it to run as well as it did and I am sure when I put on the generator the revs are going to drop to 4 or 500 rpm. The generator will be around 3:1 ratio so I would expect it to run around the 1500 rpm or so. I will post pictures soon.
One thing I did do was try and change the flywheel from the 100mm steel one to a 12" aluminium pulley. Well that worked a lot better in the rev range and ran smoother. Maybe Ian might know the answer as to why it ran smoother, Guessing its to do with the larger circumference..... Trev

[Trevor]

Hey! thanks for that Ian! That looks a lot better idea than what I was trying to do. Putting the damn thing in the lathe and hitting in places to get it straight - Got there though. Thanks mate, really appreciate the help.
Trev

[Ian S C]

With the larger flywheel the effective weight is at a 6 inch radius compared to the 2" radius of the smaller one, so you can have a more effective FW with the large diameter, and actually get away with less weight. A well built motor will(sometimes)work with no FW but it will have very little torque, and will need to run at high speed, the only difficulty is turning the shaft to start it.
Ian S C

[Trevor]

Thanks Ian - I found that out the hard way and the larger flywheel certainly made the difference. As you said, the aluminium flywheel was actually lighter in weight. Thanks for your help again - My next post will show the engine running, however, I had to remove my generator as I found the radiator fan ran better with a pulley system. All in all it works great and now fitted a fan which pushes quite a lot of air. The photos will tell it all and it does look impressive with no electricity running it. My neighbour was excited thinking it was self powered ie. free energy - Now that would be nice. Trevor

[Trevor]

Hi all - Below is the photos of the finished engine. You will notice the methylated spirit burner is a red flame. This is due to me adding 35% water to the mix which makes the burner run cooler and cleaner .
From my original idea of having the generator running the pump and fan worked OK, but pulled the revs down to around 450 or so as it was putting out 12VDC at 520ma. I found by changing the pump to a gear system and running the radiator fan with a pulley system from the drive I got far better results. The Fan is now running at 700 to 750 rpm.
Trevor

[thanh-cuibap]

Really impressive !! very nice..

[Trevor]

Thanks Thanh - Some changes will need to be made. The alloy top plate gets too hot from the fire box, so, I am going to take the fire box apart and try and make the heat disperse away from the top plate as it also effects the radiator as well.
Trev

[thanh-cuibap]

you can look at this solution, I think it would reduce the temperature of alloy top plate !!
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Engine from the Side - Burner Opening.jpg (274.47 KiB) Viewed 10338 times

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[thanh-cuibap]

I really like it !! Very.. very nice !!!

[Trevor]

I have used ceramic heat brick 30mm thick just before the cooling tubes. You can see the white brick sitting under the red top plate, however, you may be right about the ceramic fibre wrapped around the heater box though. Something I never thought of. I have just returned from the shed and cut it all down to have an open area with the heart blocks removed. Removed the meths vapourisng burner and replaced with a single wick type. Worked just as good without all that heat. Then ALAS! it slowed down and I think a strand in the displacer has jammed as I can feel the restriction. Got to fix that now. I will post you another picture when I have finished.
Buy the way, I like your word graphics on the photo - Well done

Trev

[Ian S C]

Hi trev, Like your little mate hanging off the rafters, we don't have them this side of the pond.
I'v had quite good results using thermosyphon for the water cooling, the hot water rises to the top of the radiator, as it cools it feeds back to the bottom of the cooling jacket, no pump needed. I do have one motor with a pump, just because I wanted a pump on a motor.
Ian S C

[Trevor]

Hi Ian, I am not sure that would work due to the height of the cooling tubes, but it is worth a try.
Today I took it all apart and got rid of the heater box completely and just kept a shroud around it. I do not know whether you have had any experience in what is known as back heat or wasted heat that is reflected back down. Gets the wood so damn hot. I have seen some vids on Utube showing the heat going through a small opening into the burner box, maybe that's the way to go. Still the top plate gets so hot you can't touch it and makes the engine slow down.
The diaphragm is working great and seems to be lasting. Oh1 one other thing Ian I moved the radiator high above the stand. Makes the engine look enormous - Haha!
You have good eyes to see that lizard Ian. We also have large Goannas that just trundle through our carport and lots of snakes - Makes life interesting.