Author Topic: Junkers CLM  (Read 22601 times)

Online Casting Iron

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Re: Junkers CLM
« Reply #180 on: July 10, 2024, 11:22:50 AM »
Roger-

Quite an exotic engine.
Nice work !

.

Offline Roger B

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Re: Junkers CLM
« Reply #181 on: July 11, 2024, 08:22:19 AM »
Thank you all  :ThumbsUp:

Michael, The scavenge cylinder is square as the top piston yoke and the pull rod little ends have to fit inside to reduce the height of the engine. As it is the scavenge pump it will only work at up to 1 bar so the fit does not have to be as good as the main cylinder.
I have thought a lot about how to make the cylinder, a shaping machine would be ideal but I don't have access to one. I could admit defeat and ask the tool room at work to EDM it, but at the moment I am looking at milling it with an 8mm cutter and then rounding the corners of the piston to suit.  :thinking:
Best regards

Roger

Offline Admiral_dk

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Re: Junkers CLM
« Reply #182 on: July 11, 2024, 07:57:40 PM »
I have thought similar tings .... You can mill the Piston Square -
But there is no way to do the same for the Cylinder ...!!!

As for the Radius - that is probably mostly down to practical choices ....  :thinking:

It is one of those Engines that will never be sexy in my book - but mighty practical and usefull in all it's full size version => deserving a Model done after it  :ThumbsUp:

Per           :cheers:

Offline gipetto

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Re: Junkers CLM
« Reply #183 on: July 12, 2024, 05:14:48 AM »
mild steel box iron is widely available. there is a seam on the inside that would have to be removed. i guess you want cast iron though.
would the engine still run if you modified the design to use a round cylinder instead? Since you would be circling the square the displacement would be a little greater.

Offline Roger B

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Re: Junkers CLM
« Reply #184 on: July 12, 2024, 07:59:44 AM »
Thank you both  :ThumbsUp:

The scavenge piston needs to be rectangular as it is also the crosshead for the top piston and needs to stop the two pull rods from twisting.

The next stop was to mill clearance slots in the bottom of the liner for the conrod. The liner was set up on the RT with the Keats angle plate and centred with the 20mm Acrolap. The slots were cut with a 10mm end mill. Having reached this point I could finally put all the rods together and see if it would turn.

<a href="https://www.youtube.com/watch?v=nB0P1z6LGpM" target="_blank">http://www.youtube.com/watch?v=nB0P1z6LGpM</a>

Now it's time for the somewhat boring messy lapping of the bore using the 20mm Acrolap and 40 micron diamond paste.
Best regards

Roger

Offline Michael S.

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Re: Junkers CLM
« Reply #185 on: July 12, 2024, 08:35:17 AM »
Here is another picture of how the square flushing piston is arranged in the engine. I didn't give it a thought at first, but the square piston guides the two connecting rods.
It is nice to see,
how the engine is made.

(Roger, do you know the book about Hugo Junkers? It's interesting and maybe you can read it.)

Greetings Michael

Offline Roger B

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Re: Junkers CLM
« Reply #186 on: July 12, 2024, 03:44:53 PM »
Thank you for the picture of the scavenge system  :ThumbsUp:  :wine1:

I was not aware of that book however I have found a copy on line and have ordered it  :)
Best regards

Roger

Offline crueby

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Re: Junkers CLM
« Reply #187 on: July 12, 2024, 04:22:25 PM »
Quite a complex system, I've never seen anything like that.   :popcorn:

Offline gipetto

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Re: Junkers CLM
« Reply #188 on: July 12, 2024, 04:42:19 PM »
could you use an oval piston like hondas nr500? I'm not sure how to bore an elliptical hole, but even if the shape was a combination of a bisected cylinder and a cuboid that should work right? in that case you could bore two holes at each end of the cylinder, then bore many more holes closely spaced in between.
<a href="https://www.youtube.com/watch?v=aULQ7PavvTs" target="_blank">http://www.youtube.com/watch?v=aULQ7PavvTs</a>

Offline Michael S.

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Re: Junkers CLM
« Reply #189 on: July 12, 2024, 05:21:47 PM »
I find these engines very fascinating and I once got a tip from a school friend years ago that there was still an engine like this in an old railway signal box. It was used there as an emergency generator. But it was only used for maintenance all these years.
My school friend works for the railway himself and got the OK from “above” so that we can remove the engine. The signal box will also soon be demolished and the engine will be scrapped.
The signal box was in the middle of busy tracks and we had to get the individual parts across the tracks as quickly as possible. The whole campaign wasn't really official either 🤫. But everything worked well. (Officially asking the Deutsche Bundesbahn wouldn't have worked, but there were still people on the railway who loved old technology.)
Now the thing is in the old pig sty and there has still been no power outage. The engine starts with one revolution of the hand crank. This is an advantage of the two pistons. The disadvantage: the engine is loud as hell.

Michael

<a href="https://www.youtube.com/watch?v=D82Y-s3200M" target="_blank">http://www.youtube.com/watch?v=D82Y-s3200M</a>

Offline crueby

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Re: Junkers CLM
« Reply #190 on: July 12, 2024, 06:07:22 PM »
Michael, fantastic that you were able to save another old engine from the scrap heap!

 

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