Author Topic: Junkers CLM  (Read 17453 times)

Online Kim

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Re: Junkers CLM
« Reply #120 on: March 24, 2024, 03:33:22 PM »
Making nice progress, Roger!  :ThumbsUp: :popcorn: :popcorn: :popcorn:

Hope that's not blood up there in post #118 (third picture down, just below the ball-peen hammer?)

Kim

Offline Roger B

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Re: Junkers CLM
« Reply #121 on: March 29, 2024, 08:15:21 AM »
Thank you Kim  :)  That's just red marked pen to keep the orientation until I make some permanent marks.

Due to my small machines I could not make a long enough crankshaft so now I need to add an extension to drive the water pump etc. As the crankshaft was in the lathe I turned a small radius on the webs to make it easier to fit into the crankcase. The extension will be in two parts, a sleeve and a sacrificial extension shaft. I chewed up the end of the crankshaft on my diesel trying to start it and expect similar problems with this engine so I shall make it replaceable. The starting dog is not keyed to the shaft, just clamped, to act as a mechanical fuse.

The end of the crankshaft was turned down to 8mm and a 12mm sleeve was drilled and reamed to fit. The sleeve was then broached for a 2mm key. It will be Loctited to the end of the crankshaft and the extension will use the same key but be held in place with a couple of grubscrews.
Best regards

Roger

Offline Vixen

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Re: Junkers CLM
« Reply #122 on: March 29, 2024, 10:55:52 AM »
Hello Roger,

An ingenuous way to extend the shaft to compensate for the small size of your lathe. Excellent !!  :ThumbsUp: :ThumbsUp:

Will there be an outboard bearing to support that long shaft?

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Roger B

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Re: Junkers CLM
« Reply #123 on: March 29, 2024, 02:55:33 PM »
Thank you Mike  :) Yes there will be a ball race fitted in the end plate to support the shaft.

The keyways in the crankshaft and extension were cut using the small Proxxon mill. This was also used the mill a flat for the grubscrews. Two M2 holes were drilled and taped in the sleeve using the Proxxon drill. After a trial dry assembly the sleeve and key were fixed to the crankshaft with Loctite 648. This will be allowed to dry completely before I try the extension piece as I don't want it getting stuck in.

A quick check showed the run out on the shaft and sleeve to be the same, around 0.1mm, probably due to a bit of stress relief in the C45k that the crankshaft is made from.
Best regards

Roger

Offline Zephyrin

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Re: Junkers CLM
« Reply #124 on: March 30, 2024, 02:48:56 PM »
great thread on the built of this engine Roger, as always...
I wonder how you succeed to mill steel shaft with such a flimsy cross table, hats off to you !

Offline cnr6400

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Re: Junkers CLM
« Reply #125 on: March 30, 2024, 03:12:36 PM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
"I've cut that stock three times, and it's still too short!"

Offline Roger B

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Re: Junkers CLM
« Reply #126 on: March 31, 2024, 08:32:40 AM »
Thank you both  :)

Zephyrin, it actually works well, it is just in a completely different range to 'normal' milling. This was done with a Proxxon 2mm carbide end mill running at around 8000 rpm. Depth of cut was 0.2mm and the feed was as fast as I could turn the handle. It would have taken more depth of cut but I wasn't in a hurry.

I fitted the extension into the crankshaft nose and tightened the two M2 grubscrews with a key about the size of a paperclip. I seems to run true  :)

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

Next up is the side connecting (pull) rods, another part on the list of things that are too big for my machines. These will be made in two pieces, the big end with be fixed to the rod with an M6 x 0.5 thread and Loctite. I am modifying the original with a three piece big end so I can fit shims to adjust the top piston position. The prototype only has shims on the lower connecting rod.
Best regards

Roger

Offline cnr6400

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Re: Junkers CLM
« Reply #127 on: March 31, 2024, 03:39:54 PM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
"I've cut that stock three times, and it's still too short!"

Offline Roger B

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Re: Junkers CLM
« Reply #128 on: April 01, 2024, 08:00:40 AM »
Before I made a start on the connecting rods I made the oil connection for the main bearing. This was set at the correct orientation and angle using the angle vice my father made as an apprentice  :) I started with a 6mm centre cutting end mill followed by a 2.5 mm drill through into the bearing. Not quite into the middle of the oil groove but fixable with a rifler file. The hole was then opened out to 4.5mm and taped M5 x 0.5. Finally I milled a flat for the sealing washer.

On with the conrods.
Best regards

Roger

Offline Vixen

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Re: Junkers CLM
« Reply #129 on: April 01, 2024, 02:09:47 PM »
Nice work Roger.   :ThumbsUp: :ThumbsUp:

I see you have wisely put some tissue into the headstock taper, but do you ever get swarf ingested into the fan of that motor alongside it?

Cheers

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline RReid

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Re: Junkers CLM
« Reply #130 on: April 01, 2024, 03:56:52 PM »
Lots of excellent progress, Roger. Nice to see the picture of the full size example, especially the piston/rod assemblies laid out. :ThumbsUp: :ThumbsUp: :wine1:
Regards,
Ron

Offline Roger B

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Re: Junkers CLM
« Reply #131 on: April 06, 2024, 04:41:29 PM »
Thank you both  :ThumbsUp: Mike, the long swarf tends to go the other way so no problem. I believe the lathe originally had a filter on the end of the motor but this stopped the chuck jaws being fully opened.

On with the con rods. The little ends were marked and then drilled and reamed 6mm to act as a reference. Next the ends were marked and centre drilled so the rod could be turned down to 8mm. Finally the end was turned down to 6mm for the M6 x 0.5 thread to fix the big end assembly in place.
Best regards

Roger

Offline Roger B

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Re: Junkers CLM
« Reply #132 on: April 07, 2024, 08:46:17 AM »
Now a not unexpected problem  :(  When I designed the sealing O rings between the cylinder liner and the cylinder block I went for 1.5 x 31mm rings. I knew from the O rings I used in sealing the helix fuel injection pump that there was a risk of the O ring being damaged by the various openings in the cylinder block.
The various ports were carefully radiused and smoothed. The first trial O ring passed through undamaged but the subsequent attempts were broken, sometimes in more than one place. One piece had gone down one of the water passages.
There are several possible solutions:

- Glue the O rings into the grooves so they can't drop into the openings.

- Open out the grooves and use a 2mm section O ring.

- Seal the liner with an appropriate Loctite type liquid.

Still thinking about this one  :thinking:


Best regards

Roger

Offline Admiral_dk

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Re: Junkers CLM
« Reply #133 on: April 07, 2024, 12:19:11 PM »
Hi Roger

The most obvious culprit is the Exhaust Port in my book. It is big enough to let the O-Ring 'fald out' of it's groove => resulting in a Cut much closer to 90 degrees, than one should think possible  :censored:

I have sometimes successfully used Grease to 'lock/park' the O-Ring during assembly ....
Call off Nature ....

Sitting on the Throne (some do their best thinking there) ...:
 ... No the Grease won't work here .... Need to plug the big Ports and other places the O'Ring can 'drop into' (the small ones can usually be ignored) .... 3D Print stoppers ...?... they need to be water solvable ..!!.. (being in the bathroom) how about Soap …?

String some hand soap and apply a drop or two of water to the mix. Apply to all desired places. Press the Liner through (without the O-Rings) to ‘clean’ the bore. Install the O-Rings and mount the Liner into the Cylindercase.
When all is well – soak in hot water for some time, followed by circulating tap-water under normal preasure through every single Port and hole, to get rid of the rest ….

Hopefully a fully functional Cylinder assembly that is sealed and flowing in all the right places 😊

Per     :cheers:
« Last Edit: April 07, 2024, 07:31:01 PM by Admiral_dk »

Offline Roger B

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Re: Junkers CLM
« Reply #134 on: April 10, 2024, 06:57:28 PM »
That's an interesting idea  :)  :) I think that it would work to assemble the cylinder once  :ThumbsUp: As this is very much an experimental engine I am assuming that I will need to remove the liner at some point for modifications.

Maybe I can develop it to use a low melting point metal/alloy. I have some what I think is tin based from New Years Eve Blei Giesen which hopefully will melt out without damaging the O rings.

Interestingly the damage seemed to due to the two slightly offset water cooling ports at the top of the cylinder. The exhaust port is big enough to see what the O ring is doing.

Development is fun  ::)
Best regards

Roger

 

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