Model Engine Maker

Engines => Your Own Design => Topic started by: Roger B on December 16, 2018, 09:31:44 AM

Title: Junkers CLM
Post by: Roger B on December 16, 2018, 09:31:44 AM
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
Title: Re: Junkers CLM
Post by: fumopuc on December 16, 2018, 10:16:12 AM
Hi Roger,
looking good, I am ready to watch every posting.
What a challenge.
Title: Re: Junkers CLM
Post by: Jo on December 16, 2018, 10:21:10 AM
Good luck Roger  :)

Jo
Title: Re: Junkers CLM
Post by: Ye-Ole Steam Dude on December 16, 2018, 10:25:09 AM
Hello Roger,

Very ambitious project, I to will be following along.

Have a great day,
Thomas
Title: Re: Junkers CLM
Post by: b.lindsey on December 16, 2018, 01:10:49 PM
Same here Roger. should be a great project!!

Bill
Title: Re: Junkers CLM
Post by: lohring on December 16, 2018, 02:39:31 PM
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
Title: Re: Junkers CLM
Post by: yogi on December 16, 2018, 03:08:57 PM
Very interesting project Roger!  :popcorn:
I'm looking forward to follow along on your progress.  :ThumbsUp:
Title: Re: Junkers CLM
Post by: Roger B on December 16, 2018, 04:00:24 PM
Thank you all  :ThumbsUp:  :ThumbsUp: I like a challenge  :wine1:

Lohring, I shall have a good look at those papers thank you  :)
Title: Re: Junkers CLM
Post by: Niels Abildgaard on December 16, 2018, 04:33:29 PM
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.

https://www.youtube.com/watch?v=jUQ_OFa-WKw

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
Title: Re: Junkers CLM
Post by: Admiral_dk on December 16, 2018, 05:38:04 PM
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.

 :cheers:      :popcorn:
Title: Re: Junkers CLM
Post by: Niels Abildgaard on December 17, 2018, 03:59:47 AM
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.
Title: Re: Junkers CLM
Post by: Admiral_dk on December 17, 2018, 12:45:49 PM
Thank you for the warning.
Title: Re: Junkers CLM
Post by: Roger B on December 17, 2018, 08:09:23 PM
Thank you for the video Niels  :ThumbsUp: 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  :headscratch: Has someone done something clever  :headscratch:  ::)  :headscratch:
Title: Re: Junkers CLM
Post by: Roger B on December 17, 2018, 08:11:17 PM
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  :headscratch:
Title: Re: Junkers CLM
Post by: lohring on December 18, 2018, 03:13:20 PM
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
Title: Re: Junkers CLM
Post by: Roger B on December 24, 2018, 09:14:46 AM
I have given this a bit more thought. The basic dimensions will be taken fron my horizontal diesel, the short connecting rod will be identical but the long pull rods are in tension so all the firing load is on the big end bolts. I did some stress calculations for the horizontal engine which gave a good safety margin with M3 bolts but I think these will have to be increased to M4. As the stroke is shorter the additional width of the bearing won't require a bigger crankcase. As the rods are in tension buckling won't be a problem so I think they can be reduced to 8mm diameter. The big ends will be reduced to 10mm wide to keep the crankshaft as short as possible.
I had a dig through my material stocks and have a cylinder block, cylinder liner, crankshaft and pistons.
Title: Re: Junkers CLM
Post by: Rustkolector on December 26, 2018, 05:59:38 PM
Roger,
Here is another OP diesel engine design from Achates Power currently in a joint research project with Cummins Engine Co. for development of combat vehicle engines for the US Army. It is a compact engine following more contemporary engine package design features. It does use a blower for scavenging which might complicate a smaller model engine design. Watch their video.
Jeff

http://achatespower.com/our-formula/opposed-piston/
Title: Re: Junkers CLM
Post by: Roger B on January 13, 2019, 05:35:43 PM
Thank you Jeff  :ThumbsUp:  There seem to have been many attempts at opposed piston engines but they have only been successful in larger sizes  :(

I am slowly working through the design. I now understand the square scavenge piston  :) It is so the ends of the pull rods for the top piston can go into the scavenge cylinder and reduce the height of the engine (and the piston).

The next step is to work out a governor design. It is mounted on a vertical shaft in the front part of the crankcase driven by a pair of helical gears. The principle is similar to the one I was experimenting with for the horizontal diesel:

http://www.modelenginemaker.com/index.php/topic,5545.195.html

In this case the bottom plate is mounted on a bearing and the balls are driven by a spider keyed to the shaft. A PDF of the principle is attached. I think I will have to make a trial version. The shaft is 6mm diameter and the overall diameter is 32mm with 6 6mm diameter balls.
Title: Re: Junkers CLM
Post by: Roger B on January 30, 2019, 05:33:01 PM
As I continue with the drawings the governor is a key part of the front of the crankcase so time for experiments  :)

I decided to make the drive spider from Delrin and the thrust plate and cone will be steel (case hardened if it works  ::) ) The basic form was turned and the keyway cut. As it was Delrin it just needed finger pressure on the broach  :) The blank was mounted on a short length of 6mm rod with a key slot and put in my Proxxon RT. I cut the slots with a 6mm 3 flute end mill in two steps.
Title: Re: Junkers CLM
Post by: Roger B on January 30, 2019, 05:39:49 PM
A quick check with some 6mm ball bearings and onto the cone. This and the thrust plate were turned from a length of 35mm free cutting steel. The thrust plate was polished before parting off. Next the cone was reversed in the 3 jaw chuck using a couple of parallels (6mm HSS tool blanks) to keep it in line with the face of the chuck.
Title: Re: Junkers CLM
Post by: Roger B on January 31, 2019, 07:47:13 PM
The cone was then drilled 9.8mm and reamed 10mm. The cone itself was turned using my little top slide. I used the body of a square to align the thrust plate at the front of the chuck so it could be faced and then moved it back for drilling and boring.
Title: Re: Junkers CLM
Post by: Roger B on January 31, 2019, 07:47:51 PM
And due to the 8 picture limit
Title: Re: Junkers CLM
Post by: MJM460 on January 31, 2019, 09:28:30 PM
That’s an ingenious, compact design, Roger.  It will be interesting to see how it performs, and how much force it can produce on the levers.  I assume the top cone also spins so the balls only move in and out?

Still following and enjoying.

MJM460
Title: Re: Junkers CLM
Post by: Roger B on February 01, 2019, 07:25:45 AM
In this version the top cone is fixed so it is it's own thrust bearing. The thrust plate will rotate at twice the shaft speed. I tried a couple of other variants in my diesel thread. This design is the same as was used on the full size version of the engine.
Title: Re: Junkers CLM
Post by: Roger B on February 03, 2019, 08:31:38 AM
The bronze bush was turned, pressed in place and reamed again. The sleeve was made from 8mm silver steel, hardened and polished. I made a trial shaft from 6mm silver steel and cut a 2mm keyway to drive the spider.
Title: Re: Junkers CLM
Post by: Roger B on February 03, 2019, 08:37:05 AM
I drilled and tapped an M3 hole in the side of the cone to be able to apply a load and assembled the system for a trial in the bench drill (it has a speed indicator). With the two springs I was using it would lift between 2000 and 2500 rpm depending on the preload (set by winding the table up and down).

https://www.youtube.com/watch?v=kuLW0hDWwog
Title: Re: Junkers CLM
Post by: Kim on February 03, 2019, 08:56:40 PM
That works pretty well! :ThumbsUp:
Kim
Title: Re: Junkers CLM
Post by: Roger B on February 12, 2023, 03:35:17 PM
As my diesel trials were not as successful as I hoped I moved away from this project. Now I have running diesel I have restarted. Along the way I have picked up various pieces of information and pictures of the engine components. There are a number of different variants with different configurations. Some appear to have round scavenge pistons, some have the inlet ports at the bottom and the exhaust at the top. Some have a closed transfer port system, others fill the complete crankcase.

I have decided to keep to my original prototype of the sectioned engine with the open inlet ports but with the bore reduced to 20mm to make machining easier with my lathe. Studying the other information I have collected and thinking about the design has shown me a number of things:

1) The scavenge piston is coupled to the shorter crank throw. This means that the area of the scavenge piston must be at least 2.5 times the area of a working piston. This fits fairly well with the scavenge cylinder fitting around the pull rods for the top piston.

2) The slots for the top piston yoke are carried on below the inlet ports. This allows the length of the piston and the total height of the engine to be reduced. This is visible in the cutaway picture.

3) The forces are not insignificant. The 40 bar compression pressure of my horizontal diesel gives a load per piston of 125kg. If the combustion pressure is 80 bar that is 250kg per piston. The bottom connecting rod is based on the horizontal engine so that will be ok but the design of the pull rods will need some calculation. The rods themselves are in tension so will be free from buckling problems but the loads on the top bearings and the big end bolts may be a problem.

4) Some versions have a float chamber feeding the injection pump but I don’t understand what this is for.
Title: Re: Junkers CLM
Post by: cnr6400 on February 12, 2023, 04:13:43 PM
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
Title: Re: Junkers CLM
Post by: Admiral_dk on February 12, 2023, 06:29:40 PM
I still have just found some tech info on this engine type :
https://www.thesahb.com/technical-talk-3-1929-junkers-diesel-engine-for-cars/ (https://www.thesahb.com/technical-talk-3-1929-junkers-diesel-engine-for-cars/)

So I'm finally wise to how the Intake / Transfer took place - see middle of page + text.

I find your example of the Injection pump peculiar Roger .... It appears to have both an adjustment for the stoke, by moving the roller hinge sideways + the modern turning the piston to change the inlet port height too  :headscratch:
Oh and no - I can't explain the float very well either Roger - but I'm glad to see you back on this one again  :cheers:

Per
Title: Re: Junkers CLM
Post by: vtsteam on February 12, 2023, 08:34:35 PM
 :popcorn: :popcorn: :cheers:
Title: Re: Junkers CLM
Post by: steamer on February 12, 2023, 09:30:04 PM
That's cool!!!    I'll be watching Roger!    that's a neat engine!

Dave
Title: Re: Junkers CLM
Post by: Michael S. on February 13, 2023, 10:24:04 AM
Hello Roger, I have now discovered your construction report for the Junkers engine. An interesting project.
In my stable there is a 1 HK 65 with a 7.5 Kw generator. And I've been waiting for a power outage for a long time 😁.
It could be that I still have a spare parts list for the operating instructions.
If it helps you.

Greetings Michael
Title: Re: Junkers CLM
Post by: Roger B on February 13, 2023, 05:19:35 PM
Thank you all  :ThumbsUp:

Michael  :)  I have a rather poor PDF of the spare parts list for a 1 HK 65 (NDZ 9/12) and some French operating instructions for what CLM called a CR1. More information is always welcome  :cheers:

Per, the French information I have suggests that the helix part was used by the governor in the conventional way to control the speed and the other rocker roller on the cam was used for stopping.

I have attached the current state of the design, some way to go  ::)
Title: Re: Junkers CLM
Post by: Roger B on May 14, 2023, 05:08:09 PM
Finally cutting some metal. The crankshaft is made from 60 x 15mm key steel which I have used before but the design of this shaft is on the limit for my Hobbymat (I can cheat if I have to, but model engines should be made on my machines). Marking out is also stretching my equipment but so far all is ok.
Hacksawing the waste away is somewhat of a change from fuel injection systems  :)
Title: Re: Junkers CLM
Post by: cnr6400 on May 14, 2023, 08:03:20 PM
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
Title: Re: Junkers CLM
Post by: Michael S. on May 14, 2023, 08:59:02 PM
Hello Roger,
I watch with interest.
Especially if someone is still sawing by hand.

Greetings Michael   :cheers:
Title: Re: Junkers CLM
Post by: RReid on May 15, 2023, 12:02:29 AM
Off to a good start. Hope you're enjoying the part size "paradigm shift"! I'll be following along for sure. :popcorn:
Title: Re: Junkers CLM
Post by: Kim on May 15, 2023, 06:19:31 AM
It's fun to mix it up a little bit, isn't it!  :D  :popcorn:

Kim
Title: Re: Junkers CLM
Post by: Roger B on May 15, 2023, 07:10:14 PM
Thank you all  :) It is fun to play with some (relatively) big stuff for a while  :ThumbsUp:

A bit of 'dodgy set ups are us' machining of the exhaust crankpin. OK at 500 rpm for the webs and 250 rpm for the crankpin.
Title: Re: Junkers CLM
Post by: Roger B on May 23, 2023, 05:41:22 PM
On with hacking out the crankshaft. For the outer two crankpins I need to support the centre webs. This is done with a bolted on bridge piece as before. Some more was hacksawed away and the first outer crankpin was rough machined using a variety of tools to deal with the narrow (10mm) gap.
Title: Re: Junkers CLM
Post by: cnr6400 on May 23, 2023, 10:01:28 PM
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
Title: Re: Junkers CLM
Post by: AlexS on May 23, 2023, 11:20:04 PM
Great start. Sometimes designs or hobby work need some time to "cook" before to get started. Now you have more knowledge about making model diesel engines! Some crazy opposite engine is something on the list to design.
Title: Re: Junkers CLM
Post by: Roger B on May 28, 2023, 01:18:55 PM
On with the crankshaft, it looks to be possible with my lathe.

There are a few more challenges to come  ::)

The cylinder liner will be 105mm long, bored 20mm. I may need to look at making a between centres boring bar. The maximum diameter will probably be 15mm so making a fine adjuster for the cutter will be difficult.

The scavenge pump is mounted on top of the upper piston. The original piston and cylinder were rectangular. I could possibly fabricate the cylinder from 4 pieces of flat steel silver soldered together  :headscratch: The piston will need to be aluminium on weight grounds. Leakage will not be too much of a problem on the compression stroke as it will be leaking into the crankcase that it is filling.

The valves for the scavenge pump are also difficult to fit into the space. I am looking at fitting reed valves to the underside of the piston as delivery valves, the suction valves can then be mounted on top of the cylinder. The original appears to use disc valves. I have some carbon fibre reeds that I bought when working on the two stroke diesel that I may be able to adapt.
Title: Re: Junkers CLM
Post by: RReid on May 28, 2023, 03:00:35 PM
Quote
I may need to look at making a between centres boring bar. The maximum diameter will probably be 15mm so making a fine adjuster for the cutter will be difficult.
A fine adjuster would be nice but not really necessary, since the piston can be sized to fit? I've had success in the past with such a boring bar. Takes a bit of patience, but we all know you have that covered! Looking forward to learning from your solutions to the various challenges to come. :cheers:
Title: Re: Junkers CLM
Post by: Michael S. on June 03, 2023, 06:31:45 PM
Hello Roger,
I checked the parts list. It is also just a paper copy. But maybe this will be of use to you.
If you need specific parts to view let me know.

Greetings Michael
Title: Re: Junkers CLM
Post by: Roger B on June 18, 2023, 08:15:13 AM
Thank you Michael  :ThumbsUp: That looks similar to the copy I have. I will let you know if I need any details. I will have to change a few elements of the design to allow for the small scale and for fabrication rather than castings.

On with the crankshaft. I have had to use a variety of tools for turning the crankshaft due to the small size of my lathe and the deep slots between the webs. The full stroke of the crankshaft is 65mm, the same as the centre height of the lathe  ::)

https://www.youtube.com/watch?v=nBqRCy_7ZXE

The first section of shaft I turned ended up with a rather poor finish although the earlier cuts looked ok  :( This is not a critical problem as I still have 1 mm left for the finishing cuts. The set up will also be more rigid as the opposite shaft will be held in a collet chuck rather than between centres.

I received a parcel with a huge warning label stating 'Fragile' and 'Open immediately and check for damage'. The contents: 25mm and 35mm cast iron for the cylinder and pistons and aluminium plates for the crankcase  ::)
Title: Re: Junkers CLM
Post by: Michael S. on June 18, 2023, 02:13:44 PM
Hello Roger,
the crankshaft looks very good. 👍 For me, this is an exciting work process on this type of crankshaft.

And was something broken in the package?

Greetings Michael
Title: Re: Junkers CLM
Post by: RReid on June 18, 2023, 03:06:38 PM
Crankshaft is coming along well. It's always fun to get small machines to a good job of big jobs! Just take care with that fragile cast iron.  :Lol: :ThumbsUp: :ThumbsUp:
Title: Re: Junkers CLM
Post by: Kim on June 18, 2023, 04:46:31 PM
Nice work on that one piece crankshaft!  That's a lot of material to remove on that spindly part! Nicely done  :ThumbsUp:

Nice to see that your fragile package arrived with all the CI in tact!

Kim
Title: Re: Junkers CLM
Post by: Roger B on June 18, 2023, 08:11:40 PM
Thank you all  :) Nothing in the package was damaged, it did not pass through the British Postal system or airport baggage handling  ::)

I changed to a DCMT tip and got a much better finish on the shafts, I think the original tip may have been worn or chipped but not visibly. Next I moved over to the Keats angle plate to finish the crankpins. The inlet (shorter stroke) ones were ok with a reasonable finish. Next the exhaust (longer stroke one).
Title: Re: Junkers CLM
Post by: Admiral_dk on June 19, 2023, 10:12:04 PM
Great to see that you have made progress, while I was on extended Weekend  :ThumbsUp:

A very interesting project  :Love:

Per   :cheers:
Title: Re: Junkers CLM
Post by: cnr6400 on June 20, 2023, 12:50:38 PM
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
Title: Re: Junkers CLM
Post by: Zephyrin on June 21, 2023, 10:31:51 AM
you've embarked on a great and very original project, and the crankshaft is already a feat!
I've found quite a bit of documentation in French on this engine, which seems to have been very popular here in agriculture and industrial locomotives...

https://wikimaginot.eu/V70_glossaire_detail.php?id=1000986
http://vieux.tracteurs.free.fr/pdf/moteur_CLM_type_LC_et_CR.pdf
Title: Re: Junkers CLM
Post by: Admiral_dk on June 21, 2023, 09:45:19 PM
Thank you very much for the Service Manual Zephyrin  :LittleAngel:  :ThumbsUp:

That explains a lot more than what I've seen so far + much more if I understood French better  :embarassed:

Per               :cheers:
Title: Re: Junkers CLM
Post by: Roger B on June 23, 2023, 08:53:39 PM
 :ThumbsUp: :ThumbsUp: :ThumbsUp: Thank you for those links Zephyrin  :) :) CLM and Peugeot seemed to produce a lot of these engines in smaller sizes, Junkers developed them as the Jumo aircraft engines  and Napier then produced the 18 cylinder Deltic.

There are some interesting features of the design. The two different length strokes seem to give a balance to the engine that I have not really analysed:

https://www.youtube.com/watch?v=yi2XD8PY5dk

The exhaust crankpin was clocked true and finished to 12mm and then on to the oilways. The 2.5mm dia. 57mm long holes through the shaft were my biggest worry but they were ok. As the stroke on my tailstock is only 40mm there was a lot of sliding in and out to clear the swarf. The only big problem was drilling one of the inlet crankpins, the drill dug in when breaking through but luckily just bent.
Title: Re: Junkers CLM
Post by: Roger B on June 23, 2023, 08:56:15 PM
Reaching some of the holes required a variety of tools and threading for M3 grub screws will also be fun  ::) I think I will have to make a special tap holder for the inlet crankpins  :thinking:
Title: Re: Junkers CLM
Post by: Kim on June 23, 2023, 10:13:48 PM
Ouch on the bent drill bit, Roger!  Glad it didn't ruin anything!

Were you able to straighten it and use it more? Or did you have multiples of that drill in stock?

Kim
Title: Re: Junkers CLM
Post by: Admiral_dk on June 24, 2023, 09:26:22 AM
Close call on the Drill Bit  :hellno: - glad it didn't ruin anything   :cheers:

The Crank looks to be very nicely staight and smooth  :ThumbsUp:

Per
Title: Re: Junkers CLM
Post by: Roger B on July 06, 2023, 05:46:22 PM
Thank you both  :)

I broke and then binned the bent drill, too much risk otherwise  ::) I bought 4 originally as I felt they would be 'disposable'. The next step was to tap the ends of all the oilways M3 for sealing grubscrews. As expected I had to make a special tap wrench for a couple of the holes. Finally I drilled the oil holes to the journals. This now defines the orientation and rotation direction for the crankshaft.
 
I have been thinking further about boring the liner. By the time there is a revolving tailstock centre and some means of driving the boring bar there is barely enough space. As it is not actually a single cylinder but two separate cylinders with a space between them I could bore from both ends in the usual way. With careful clocking of the outside of the liner any final errors would be removed by lapping.

The connecting rods have required some thought. Assuming a peak pressure of 80 bar the load per piston is 2500N. The exhaust piston (single) connecting rod is copied from my other diesel and should be ok. For the inlet piston (twin rods) this is 1250N per rod if all is balanced. For the bearings at the top of the rods I am looking at some model RC car units with a dynamic load of 1321N and a static load of 530N, a bit close but we will see what happens. The big end bolts will be M4 in a 6mm wide rod. The proof load is 5100N (8.8) which with 2 bolts per rod is fine. I could reduce to M3 with a proof load of 2920N (8.8) which still has a good factor of safety.
Title: Re: Junkers CLM
Post by: steamer on July 06, 2023, 07:09:38 PM
Hey   don't be glossing over that faceplate fixture!     Looking for details here!

 8)
Title: Re: Junkers CLM
Post by: Kim on July 06, 2023, 07:40:39 PM
Roger, I like your special tap wrench!  Very nice  ;D

I'll be interested in how you do this on your lathe.  I can see that it is a little challenged in the bed length department...  I'm sure you'll figure out a way!  :ThumbsUp: :popcorn:

Kim
Title: Re: Junkers CLM
Post by: Roger B on July 06, 2023, 07:52:53 PM
Thank you Kim  :)

Dave, I guess you mean the Hemingway Keats Angle plate:

https://www.modelenginemaker.com/index.php/topic,4275.0.html

An excellent tool/accessory for a small lathe  :ThumbsUp:
Title: Re: Junkers CLM
Post by: Admiral_dk on July 06, 2023, 10:32:01 PM
Great progres again  :ThumbsUp:

I have two comments :

1)  The ballance of the different strokes probably matches the fact that the Inlet-Double Piston is a lot heavier than the longer stroke Exhaust Piston ....

2)  I'm not comfy with the close match off Max Load allowed on the Top Bearings, and the Calculated Load ....
Any Pre-Ignition or too much Fuel - and you will have a Catastrofic Failure  :zap:   :cussing:   :'(

Just my two Cents (for what ever they are worth) ....

Per       :cheers:
Title: Re: Junkers CLM
Post by: Dave Otto on July 07, 2023, 12:42:26 AM
Impressive work on the crankshaft Roger!
I have one similar to that in my future, taking notes here.

Dave
Title: Re: Junkers CLM
Post by: Roger B on July 16, 2023, 06:13:46 PM
Thank you  :ThumbsUp:

I'm not too worried about the load rating of the bearings as that will be for a defined life span rather that than being the ultimate load. Here the the potential side connecting rod and bearing, plenty more machining to do  ::)
Title: Re: Junkers CLM
Post by: Roger B on July 23, 2023, 06:08:10 PM
A start on the cylinder liner. This is a piece of cast iron rod. I marked one centre with it resting on V block, marked it and cut it to length with the bandsaw. The other end was then centred and both ends were drilled.

I didn't have a big enough driving dog so I improvised with a 38mm exhaust pipe clamp  ;)
Title: Re: Junkers CLM
Post by: Roger B on August 06, 2023, 02:11:50 PM
A little bit more on this. The outside was roughed out from one end and then the blank was turned around. Unfortunately the tool dug in (hard spot?) and cut a groove. This doesn't look good but will be turned off at a later stage. It was then finished to size using an aluminium insert.
The blank was then set up in the four jaw chuck, drilled 5mm from both ends with a standard drill and then finished through with long series drill. The hole was then opened out to 15.5mm using the bench drill.
Title: Re: Junkers CLM
Post by: Roger B on August 06, 2023, 02:18:33 PM
The cylinder was then set up in the four jaw chuck with the fixed steady and was faced to length. It was bored to 19.5mm from each end and than finished to 20mm. The lap just enters and the 20.1mm plug gauge wont go in.

As with the outside there is a visible difference in the cutting from both ends but no discernible step.
Title: Re: Junkers CLM
Post by: Admiral_dk on August 06, 2023, 11:04:18 PM
That is a rather thick walled Liner - will you be removing more material on the outside, before it is finished ?

Still following this interesting build  :popcorn:   :cheers:

Per
Title: Re: Junkers CLM
Post by: Roger B on September 05, 2023, 07:20:06 PM
Hello Per,

There are inlet and exhaust ports as well as water spaces to be machined from the liner. It's easier to turn from the outside of the liner than to bore in the cylinder block.

Next up is to rough out the sections of the cylinder block. There is a long section that surrounds the liner, a short piece around the inlet ports, a cast iron section for the scavenge pump cylinder and finally another aluminium section for the scavenge pump inlet valves.

I was quite pleased with the similarity of the sectors sawn from the round scavenge cylinder blank. I am sure they must have some use  :thinking:
Title: Re: Junkers CLM
Post by: Roger B on October 28, 2023, 08:36:20 AM
Slow progress carving out the various parts of the cylinder block. After some experimentation I ended up with a 16mm roughing end milling cutter and 1mm depth of cut. There was not sufficient travel to use a flycutter.

https://www.youtube.com/watch?v=EsDqwiQb_8E

Title: Re: Junkers CLM
Post by: cnr6400 on October 28, 2023, 02:08:55 PM
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
Title: Re: Junkers CLM
Post by: Kim on October 28, 2023, 03:41:31 PM
Nice to see some progress, Roger!  :ThumbsUp: :popcorn:
That's a pretty beefy chunk of metal for your cylinder block!  :Lol:
Kim
Title: Re: Junkers CLM
Post by: Roger B on November 04, 2023, 08:59:49 AM
Thank you both  :) The block will get smaller over time.

The next step was to set the block in the four jaw chuck to core drill out the bulk of the material. My hole saws will reach a depth of 40 mm so the 79 mm high block was on the limit cutting from both ends (but planned so). It is easier than drilling out when the tailstock travel is only 40 mm. There is also very limited clearance between the chuck jaws and the bed, but again I knew I can hold 60 mm in the full jaws. As Chris Rueby often demonstrates with small machines careful planning is required.

The centring was checked again, not easy on a square workpiece, but seemed top be within 0.1 mm so OK and the block was bored out to 34 mm to be a running fit on the cylinder liner. All the sealing between the liner and the block will be with O rings.
Title: Re: Junkers CLM
Post by: RReid on November 04, 2023, 03:14:39 PM
More of your always nice work, Roger. I like the use of a hole saw to rough out the bore. The picture of the chuck jaw just clearing the bed looked very familiar; been there done that! :ThumbsUp: :ThumbsUp: :cheers:
Title: Re: Junkers CLM
Post by: Kim on November 04, 2023, 03:44:17 PM
Nice work, Roger!  :ThumbsUp: :popcorn:

That's a LOT of work on a little machine like that.  You're certainly stretching it to its limit!

Kim
Title: Re: Junkers CLM
Post by: Zephyrin on November 04, 2023, 06:58:36 PM
impressive work with the cylinder block Roger, whew!
this little hobbymat is a rather man machine !
Title: Re: Junkers CLM
Post by: Roger B on November 12, 2023, 01:54:01 PM
Thank you all  :ThumbsUp:  :ThumbsUp:

The next step was to turn the various grooves for the port belts, water passages and O rings. First I turned a centring plug so I could support the liner with the tailstock. The water passages and exhaust port belt were cut with a 2.2mm parting/grooving tool. There were some chatter marks but they are not a problem.
Title: Re: Junkers CLM
Post by: Roger B on November 12, 2023, 01:58:14 PM
The O ring grooves were cut with a 1.5mm Aplitec tool. There was again a little bit of chatter which cleaned up easily with a square Swiss file. The liner was then turned round to machine the inlet port belt. Still a lot of bits to go  ::)
Title: Re: Junkers CLM
Post by: Kim on November 12, 2023, 04:16:23 PM
The liner is looking good, Roger!  Nice photos showing the sequence of your work.  :ThumbsUp: :popcorn:

Kim
Title: Re: Junkers CLM
Post by: RReid on November 12, 2023, 06:07:53 PM
That was rather more involved than most cylinder liners. Nicely done!  :ThumbsUp: :ThumbsUp:
Title: Re: Junkers CLM
Post by: Admiral_dk on November 12, 2023, 10:08:29 PM
Plenty of oppertunety for things to go wrong here - so I'm sure you are happy that there were no mishaps so far  :ThumbsUp:   :ThumbsUp:

Do you put five O-Rings on the liner, or ...?

Per     :cheers:
Title: Re: Junkers CLM
Post by: Roger B on November 19, 2023, 09:53:30 AM
Thank you all  :)  Per, there are five O rings as the top of the inlet section is open to the scavenge pump.

The next step was to fix the liner to the cylinder block. Due to the design of the engine there is very little load on the liner so I decided to hold it in place with a tapered dog point grubscrew. The tip is tapered from 3.8 to 4.2mm and the hole in the liner is reamed 4mm. The injector is mounted opposite so I drilled 5mm for the nozzle, cut an 8mm recess for the O ring and then opened out to 10mm to clear the nozzle clamping nut. There is some more work to be done for the injector fixings but that will come later.

The next step is to mill the angled inlet and exhaust ports. Luckily using a Proxxon V block I need a simple 12mm spacer under the small Proxxon RT.
Title: Re: Junkers CLM
Post by: Roger B on November 25, 2023, 08:56:49 AM
The liner was set up in the Proxxon mill and offset from the centre line to create the angled ports. These were cut with a 3mm carbide end mill at 6000 rpm in 0.5mm steps. The inlets and exhausts were machined at the same settings, the exhaust ports are 1mm longer. The liner was then further offset to cut a chamfer on the inlet ports.

This could have been done on the Hobbymat mill but it's much easier to see what is going on with the little one.
Title: Re: Junkers CLM
Post by: Roger B on November 25, 2023, 08:59:24 AM
Next I moved to the Hobbymat mill to cut the slots for the top piston yoke. This was cut in 0.5 mm steps.

Now there is some deburring and smoothing work before lapping the bore.
Title: Re: Junkers CLM
Post by: Roger B on December 16, 2023, 08:52:02 AM
A little bit more progress. I had to remove the milling head to repair the controls for the lathe and assumed that removing and replacing the round column from its socket would not upset things too much.

Unfortunately it was way off true  :(  I did a quick check with an angle plate an DTI and it appeared that the head had tilted so I did a quick basic realignment with a ground rod and the angle plate.

The cast iron block for the scavenge pump was squared up next. This will be my next challenge as it requires a precise rectangular cut out for the scavenge piston  ::)

The clearance slots were for the pull rods were cut in the inlet block and it was set up for boring.

https://www.youtube.com/watch?v=0tDWx67H7qU

Title: Re: Junkers CLM
Post by: Admiral_dk on December 16, 2023, 09:51:27 AM
Great to see another instalment of this special saga - you do pick the less traveled roads Roger  :ThumbsUp:

Funny to think that this kind of engine was very common back in the day - yet most people (including myself) had never heard of the type, as a small workhorse ....

Per      :cheers:
Title: Re: Junkers CLM
Post by: Kim on December 16, 2023, 04:18:42 PM
Sorry for your setback there Roger, and having to re-tram the mill head.  But it's good to know it's square now!

Enjoying watching your progress.  :ThumbsUp: :popcorn: :popcorn:

Kim
Title: Re: Junkers CLM
Post by: Roger B on January 12, 2024, 05:51:09 PM
Thank you both  :ThumbsUp:

I am slowly working my way through the cylinder assembly. The inlet block was bored out to 34mm and the fixing holes were drilled 4.2mm so they could be spotted through to the cylinder block. I then opened the holes out to 5mm and spotted them through to the scavenge pump section.
The next step was to bolt the inlet block to the cylinder block so I could mill the slots for the top piston yoke. It would have been easier to make them in one but it would have bee too long to bore on the Hobbymat. The 8mm slots were milled in one setup with a long series 8mm end mill.
Title: Re: Junkers CLM
Post by: Roger B on January 12, 2024, 06:55:44 PM
Next the water cooling ports were drilled to link the two cooling jackets. The top and bottom will be joined by a vertical hole and the open ends will be plugged. The exhaust port was drilled 8mm and then the port band was then opened out using a 20 x 8 mm T slot cutter. This was a bit on the limit for my machines but seemed to work  ::) Now the exhaust needs to be opened out to 10mm and there is some work with riffler files to smooth and blend all the edges.
Title: Re: Junkers CLM
Post by: Michael S. on January 12, 2024, 07:12:21 PM
Hello Roger,
nice progress.
It's always surprising what can be done with small machine tools.

Greetings Michael
Title: Re: Junkers CLM
Post by: Admiral_dk on January 13, 2024, 10:11:35 AM
That is a very wide Port - I'm guessing that you don't plan to use Piston Rings .... or will it get a sleeve inside ?

Good to see that the project is going forward  :ThumbsUp:

Per      :cheers:                   :popcorn:
Title: Re: Junkers CLM
Post by: Roger B on January 27, 2024, 07:25:29 AM
Thank you both  :ThumbsUp: Per, yes there is a cylinder liner, That is just the collector from the actual ports.

Next up was milling a recess for the injector in the cylinder block and drilling and tapping various fixing holes.

Having been thinking for some time how to hold the top of the crankcase for milling to size I realised I could drill two fixing holes where the slots for the pull rods for the top piston would be. This allowed me to machine one side and one end at the same setting which would ensure they are at right angles to each other (I know that in theory the cross slide on a lathe is not quite true to ensure that surfaces are turned slightly concave but I don't think this will matter). I was able to use the power feed on the lathe when cutting the long edge  :) I know I should really have taken the chuck off but there was enough clearance  ::)

https://www.youtube.com/watch?v=ND03Spe3BV8
Title: Re: Junkers CLM
Post by: Kim on January 27, 2024, 04:31:12 PM
Roger, it always impresses me; the incredible work you do on that little machine!   :popcorn:

Kim
Title: Re: Junkers CLM
Post by: Roger B on February 03, 2024, 04:06:20 PM
Thank you Kim, I think Chris Rubey must be the master of small machines though  :ThumbsUp:  :wine1:

I finished milling the crankcase top and then out of interest checked it for accuracy. It is square to the limits of my equipment, a couple of hundredths of a mm under size on the width and flat/parallel to a couple of hundredths as well  :) I'm happy with that.

https://www.youtube.com/watch?v=PyFGa-grlbs

Next I centred the bore for the cylinder liner and cut the bulk away with a 29mm hole saw. I am tempted to cut a bit more off the length of the boring bar but the chatter does not seem to be too bad.
Title: Re: Junkers CLM
Post by: Roger B on February 04, 2024, 09:18:37 AM
And it all seems to fit together  :)
Title: Re: Junkers CLM
Post by: RReid on February 04, 2024, 03:15:10 PM
Nice work Roger, it's coming very well. I find that shapely cylinder liner interesting to just look at! :wine1: :cheers:
Title: Re: Junkers CLM
Post by: Roger B on February 09, 2024, 07:15:19 PM
Thank you Ron, All those who think two stokes are simpler to make than four strokes should look at that liner  ::) Everything is in that. If the timing is wrong I can't just modify a camshaft it's a complete new liner  :(
Title: Re: Junkers CLM
Post by: Michael S. on March 01, 2024, 05:39:30 PM
Hello Roger,

I also have a centrifugal pump on the Junkers engine.
It is mounted on the frame.
This is an engine with generator and cooler and everything is attached to the frame.

Michael
Title: Re: Junkers CLM
Post by: Roger B on March 02, 2024, 07:34:06 AM
Thank you for the pictures Michael  :ThumbsUp:  Is that an electric control of the governor in the second picture or just start/stop?
Title: Re: Junkers CLM
Post by: Michael S. on March 02, 2024, 07:07:15 PM
Hello Roger,

yes, that is a magnetic switch. He switches the engine off again.
The engine with generator was in a signal box for switches and signals on the railway. It served as a backup in the event of a power failure and switches on and off automatically. But for me the only option is to start by hand.

Greetings Michael
Title: Re: Junkers CLM
Post by: Roger B on March 04, 2024, 07:57:05 PM
I have a Kohler direct lighting set that is currently in a museum in Southern England. It is designed to start when a load of 40W is applied and shut down when the load is reduced below this. As it delivers 110V DC it is not that much use in Europe.
Title: Re: Junkers CLM
Post by: Roger B on March 09, 2024, 07:35:24 AM
On with cutting the plates that will make up the crankcase. Due to my small milling table and limited Y travel the set ups took a bit of thought but I was able to mill two sides in each set up and all ended up square and on size. Next I cut the slots for the pull rods for the top piston. These were roughed out with a 10mm slotdrill and finished with a 6 mm endmill.
Title: Re: Junkers CLM
Post by: Roger B on March 09, 2024, 07:37:07 AM
Ready to start drilling and tapping for the fixing screws.
Title: Re: Junkers CLM
Post by: Admiral_dk on March 09, 2024, 09:42:30 AM
Good to see that you are making progress and really good to confirm it all ligns up as it should  :ThumbsUp:

I also see where you got some of the inspiration from - though having it home to look and measure from might be a bit more conviniant than it being in a British Museum  ;)

Per         :cheers:
Title: Re: Junkers CLM
Post by: RReid on March 09, 2024, 03:06:41 PM
It often seems that the number of steps (and time) required is inversely proportional to the size of the machines. I always enjoy the examples you offer of how to get the most from what you've got. Nicely done!:ThumbsUp: :ThumbsUp:
Title: Re: Junkers CLM
Post by: Kim on March 09, 2024, 04:47:50 PM
Yes, what Ron said!  You get a lot done with your small machines! Very impressive.  :ThumbsUp: :popcorn: :popcorn:

Kim
Title: Re: Junkers CLM
Post by: Roger B on March 16, 2024, 08:50:54 AM
Thank you all for the support  :ThumbsUp:

First a mistake  :( I picked up the centre plate rather than the endplate and drilled a set of holes in the wrong place  :facepalm2: Not a disaster as they are not in an important place and can be plugged.

Lots of aligning pieces then drilling and taping, this time marking the pieces for identification and orientation. When the three plates for the crankcase were screwed together it would stand on the surface plate without rocking  :)
Title: Re: Junkers CLM
Post by: Roger B on March 16, 2024, 08:56:11 AM
The next step was to bore out for the crankshaft. The centre plate just has a 16mm hole that the bearing will be pressed into, the endplate is bored out to 55mm for a bearing housing to allow the crankshaft to be fitted and removed. The plates were clamped together and drilled and reamed to 16mm. the centre plate was then removed and the end plate was re-centred using the reamer. I used my largest hole saw to remove as much as possible and then bored out to 55mm.
Title: Re: Junkers CLM
Post by: Vixen on March 16, 2024, 06:34:01 PM
Hello Roger,
It's all starting to come together and we can see an engine emerging. Quite a robust structure, must be testing your small mill/lathe,

Mike
Title: Re: Junkers CLM
Post by: Roger B on March 17, 2024, 04:38:25 PM
Thank you Mike,

Yes, each design stage is a challenge both for how the engine will work and how I can make it. I started out thinking about a 25mm bore version but too many parts were just too big. The 20mm bore version is ok so far but I have had to make the cylinder block in two pieces due to my limited boring capabilities. The next big challenge is the rectangular scavenge piston and cylinder. I have a few ideas of how I could make the cylinder but I am tempted to take the easy way out and have it made at work (EDM?) to reduce the level of uncertainty when I finally try to start the engine.

I am currently sorting out the lubrication system which has an interesting 3 gear oil pump so it can scavenge oil from the main crankcase and the governor/fuel pump section. Not quite as complicated as your MB system but something to think about  :thinking:

Next up is the main bearing housing. This starts as a dog end of 70mm aluminium which was turned to fit the endplate. It was then drilled 13.5mm bored out to around 15.7 mm and them reamed 16 mm. There was a bit of chatter but it is only the housing for the main bearing. After some fairly heroic parting it was ready to finish the other side.
Title: Re: Junkers CLM
Post by: fumopuc on March 17, 2024, 05:16:47 PM
Hi Roger,
chips again.
I enjoy the progress.
Title: Re: Junkers CLM
Post by: Admiral_dk on March 17, 2024, 07:59:00 PM
Interesting solution to your 'Getting the Crank Into the Engine' and closing the hole again  :ThumbsUp:

I have never seen an Oilpump with three Gears before - but as the sketch shows - you do end up with a two scavenge and (kind of two into) one pressure Out  :thinking:

I can't blame you if you decide to use the Company Tools (EDM) - as it will not be an easy task to make @ Home ....

Per        :cheers:
Title: Re: Junkers CLM
Post by: Mike R on March 17, 2024, 08:46:59 PM
The three gear pump is interesting, saves 1 gear at the expense of a less intuitive oil routing and possibly tighter tolerances (or tolerance stack up)? 
Also interesting is to think about failure modes.  If no oil is supplied to one pump intake, it can be viewed that both pump halves will have 1/2 as much oil but still have oil all the same.  How the pump performs in this case I don't know, maybe its intentional (i.e. some is considered better than none)? 

Mike
Title: Re: Junkers CLM
Post by: Vixen on March 17, 2024, 10:13:07 PM
Thank you Mike,

I am currently sorting out the lubrication system which has an interesting 3 gear oil pump so it can scavenge oil from the main crankcase and the governor/fuel pump section. Not quite as complicated as your MB system but something to think about  :thinking:


Roger, as you say, an interesting and innovative 3 gear scavenge pump arrangement. I guess the sump will be providing mostly liquid oil, whereas the flow from the governor/fuel pump section will likely be an oil/air froth. Gear pumps are usually quite happy on a diet of air and oil, so I would not expect any scavenging issues.

Mike
Title: Re: Junkers CLM
Post by: Roger B on March 18, 2024, 07:06:11 PM
Thank you for all the interest  :)  :wine1: The oil system on this is quite interesting, it appears that the top piston and scavenge pump are lubricated by oil mist. I don't see where the oil for the governor fuel pump section comes from other than the centre main bearing  :thinking:

A quick family picture with the governor I started some years ago.

Next step some main bearings.
Title: Re: Junkers CLM
Post by: cnr6400 on March 19, 2024, 03:43:42 AM
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
Title: Re: Junkers CLM
Post by: Roger B on March 24, 2024, 08:10:48 AM
Thank you Jeff.

The bearing housing was then centred in the Proxxon drill using a stub of 16mm silver steel and offset the required 31mm. The holes were drilled through with a 3mm spotting drill. These were then spotted through to the endplate and tapped M3. A length of 16mm bar fitted smoothly through the bearing bores  :)

The main bearings are turned from RG7 bronze. They were drilled 6mm, then 11mm, bored to 11.5 mm to ensure the concentricity and then reamed 12mm.
Title: Re: Junkers CLM
Post by: Roger B on March 24, 2024, 03:09:27 PM
The two main bearings were completed and then pressed into their housings. Due too the interference fit they needed to be reamed again. Luckily my planning was correct and the centre plate could be held in the 3 jaw chuck. I assembled the crankcase and the crank turned fairly smoothly  :)

https://www.youtube.com/watch?v=wh_XvW12ZZY

Next the oil grooves were cut with a 3mm radius tool to a depth of 1 mm. Access was a bit awkward but the small compound slide just fitted. Finally I drilled the oilway for the centre main bearing. The end bearing housing needs a slightly more complex setup.
Title: Re: Junkers CLM
Post by: Kim 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
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