Junkers CLM

[crueby]

Do you have any of the Wicking Grade Loctite?  Its alcohol thin and designed to wick into assembled threads. Perfect for this kind of use.

[Kim]

Nice work on your con rods, Roger! 

Love the tuning. I can understand this kind of engine tuning!   

Kim

[Roger B]

Thank you both 

I will have to investigate wicking Loctite, I just have the standard bearing fit and thread locking grades.

Next up the big end studs. Nothing really special here except I used 3mm stainless steel which didn't part of very nicely leaving a large pip to turn off. They look a little short as the bearing cap still needs to be profiled.

[cnr6400]

 

[Roger B]

Now on with the centre connecting rod. This is somewhat simpler and is made from a single blank, cut to size with a slightly dodgy set up on the bandsaw. The little end is narrower than the big end so the sequence needed some planning to ensure I didn't cut off something I needed for a later set up. The little end is drilled and reamed 6mm as a reference point. It will be opened out for the bronze bush at a later stage.

[cnr6400]

 

[pirmin]

why did i see this so late !!! i know someone who owns a real junkers engine ( 2 cylinder configuration and he always asked me why i am not building a model of his engine

[pirmin]

nice stuff here !

[Roger B]

Thank you    I tend to try and make somewhat different things and am more interested in the technology than prototypical appearances.

The Junkers, like most two strokes, suffers from the problem that so much is built into the cylinder liner if you open out a port too much you have to make a new liner.

[Roger B]

I Milled 1mm off both sides of the little and and then moved over to the lathe to turn the rod. To turn the big end I could drive it with a 6mm stud through the little end. To turn the little end I had to make a driving plate from some scrap aluminium to bolt onto the big end fixings. The bulk of the excess material from the little end was removed with a hacksaw.
Next step over to the mill to radius the little end but before that I need to bore the holes for the big end bearings.

[Roger B]

The big ends were marked and the set up in the 4 jaw chuck to be drilled 5.8mm and reamed 6mm. This will allow them to be set up on the RT to finish the big end cap before it is bored out to 14mm. I put all three on a 6mm rod and the tolerances seem quite close 

[Roger B]

The next step is to shape the big end caps, cutting a seat for the nuts and then radiusing the centre. The nut seats were cut with a 6mm end mill, first the flat and then the recess. Unfortunately I was not concentrating and cut the wrong side of one   

After some thought I decided that as the area was under compression I could fix a small block of aluminium in place with some Loctite and a couple of 1mm steel pins. Saved 

I then set up the RT, rounding the end of the centre conrod before moving on to the bearing caps.

[Kim]

Nice work, Roger, as always! 

And excellent save on that big end mishap.  Well done!

Kim

[Roger B]

Thank you Kim 

The next step was to bore out the big ends for the bronze bearing shells. I decided that it would be easier to hold them in the milling vice than in the 4 jaw independent chuck although both routes would have worked. The 6mm pilot holes were opened out to 13mm with a drill and then finished to 14mm with the boring head. I had a plug gauge for this size which helped and I was happy that the same setting on the boring head worked for all three pieces.

[RReid]

An excellent, and appropriately stout looking result, Roger. There is a lot of work represented in that last photo, and doesn't even include the pull rods!