Junkers CLM

[Roger B]

A Junkers pattern opposed piston 2 stoke diesel has been on my build list for some time. I now think that I am close enough to getting my horizontal diesel to run to start on the design for this.
The prototype is the smallest of these engines with 65mm bore and 90 + 120mm stroke which was used in tractors and boats and was manufactured under licence by CLM in France.

There are a number of interesting design features:

The unequal strokes are supposed to allow better port timing. This will require some simulations to reach a suitable design.

The scavenge pump is mounted on top of the top piston and is square. I think this will have to be redesigned round even if this reduces the capacity.

The top of the liner is unsupported and the ports open directly into the crankcase.

The top bearings on the pullrods are ball races, I assume due to borderline lubrication

I am basing my design on a 25mm bore which gives strokes of 35 + 46mm. This will give a liner around 135mm long which I think I can bore using an idea from Jason B of an asymmetric boring bar mounted between centers and the liner clamped to the saddle. The crankshaft also appears possible. Checking on the lathe the clearance over the cross slide is 33.5mm rather than the 31mm in the manual. That extra 2.5mm will allow me to use a chucking piece supported by the tailstock.
I do also have the option of reducing the bore to 20mm but from the diesel point of view the larger the capacity the better.

I am planning to fabricate the cylinder block and crankcase from steel rather than carve it from aluminium so I need a bit of welding practice first.

The outline design is attached in .dwg and .pdf

[fumopuc]

Hi Roger,
looking good, I am ready to watch every posting.
What a challenge.

[Jo]

Good luck Roger 

Jo

[Ye-Ole Steam Dude]

Hello Roger,

Very ambitious project, I to will be following along.

Have a great day,
Thomas

[b.lindsey]

Same here Roger. should be a great project!!

Bill

[lohring]

A modern version was built by Eco Motors.  As far as I know, they're not in business anymore.  They had a large version with an electrically boosted turbocharger and a small version with piston pumps.  See the attached files for the small version..

Lohring Miller

[yogi]

Very interesting project Roger! 
I'm looking forward to follow along on your progress. 

[Roger B]

Thank you all    I like a challenge 

Lohring, I shall have a good look at those papers thank you 

[Niels Abildgaard]

Nice sweet running engine
 I have owned one left over WW2 that worked 20 years in abrick factory.
They were made 1,2 and 3 cylindered and used as generators on some danish ligthships.

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

from ca 39:00.
The upper crosshead/scavenge air piston cannot be cirkular without making the two paralel side conrods figth instead of sharing work
Last minute of video is interesting

[Admiral_dk]

Thank you for the video Niels - I wasn't aware of an engine museum in Rødvig, but after my dad moved to Nødebo. I sometimes take the ferry from Rødvig to visit him, so I will definitely visit it in the future.

I do not see any transfer port in the previous drawings - is that through the upper scavenge piston down towards the upper piston and out the sides of it into some short transfers ?

As I said elsewhere, you're in for a challenge here Roger - one I very much would like to follow and hopefully see run in the end.

      

[Niels Abildgaard]

Thank you for the video Niels - I wasn't aware of an engine museum in Rødvig, but after my dad moved to Nødebo. I sometimes take the ferry from Rødvig to visit him, so I will definitely visit it in the future.

Museum is in Rødvig ,not Rørvig.

[Admiral_dk]

Thank you for the warning.

[Roger B]

Thank you for the video Niels  I have a short clip from somewhere else of the coin balancing on the same engine. The top piston and pull rods must be heavier than the bottom piston but the stroke is less  Has someone done something clever     

[Roger B]

Per, as far as I can see there are no transfer ports as such. The scavenge pump fills the complete crankcase and the short inlet ports at the top of the liner are the effective transfer ports 

[lohring]

There is a longer paper on Eco Motors big engine.  The most interesting feature to me was the electrically boosted turbo.  It's too large to post here, however.

Lohring Miller