Junkers CLM

[crueby]

Looking great!  One question: why is one of the big ends thicker than the other two?

[Roger B]

Thank you both 

Chris, this is an opposed piston engine with a single connecting rod to the bottom piston and two side pull rods to the top piston. The two side pull rods carry around half the load of the centre connecting rod so they are 8mm wide and the connecting rod bearing is 14mm wide.

[crueby]

Ah, got it!  Clever setup!

[Admiral_dk]

Nice progress Roger + feels good when the right Plug fits and the other don't enter 

Per         

[Roger B]

Thank you Per 

Next up are the big end bearing shells. I had an offcut of split bronze with a 12mm bore that would make the centre bearing. This was trimmed to length and mounted on a mandrel made from some scrap binium. At high cutting rates it would give a mirror finish and thick blue swarf, with small cuts it was just rough. I made a small mistake and parted off the end after I had turned it to size  Problem solved with a washer  The blank was turned to size and the centre recess was cut with a grooving tool.

[Roger B]

The conrod fitted nicely in the recess so I unsoldered the two halves and assembled it for a trial.

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

Next I cut a length of 19mm bronze in half to make the bearings for the two side rods. The two halves were soft soldered together and set up in the four jaw chuck with the cut line on centre to clean up the outside to 15mm. This was then reversed and mounted in a 15mm collet to clean up the other end.

[cnr6400]

  The crank / centre rod assembly looks great in the video! 

[Roger B]

Thank you Jeff 

Next I drilled the split bearing 6mm and then 10mm. I like to do the drilling before turning down the outside to reduce the chance of splitting the bush if the drill grabs. This produced a fine pile of swarf, but not up to Chris's standard. The bore was then opened out to 11.7 mm and reamed to 12mm. The outside was turned down to 14mm and checked in the big end housing.

[Roger B]

The two bushes were parted off with 0.5mm grooving tool to minimise the waste and then split apart with an electric soldering iron. I pressed the little end bearings into the pullrods in the vice, using a 1mm thick washer as a spacer. The pullrods were then Loctited into the big ends and kept flat on the back of my big milling table whilst the Loctite cured.
That being done I moved onto the cylinder liner to chamfer the ends to make it easier to get the piston rings to enter.

[Admiral_dk]

Nice progress Roger 

Per       

[gipetto]

I wouldn't trust that glue to hold the big ends, i'd drill through both, thread the hole and screw in a bolt with loctite on the threads, then cut off both ends flush.

[Roger B]

The two parts are joined with an M6 x 0.5 thread plus a cylindrical section to take the side forces. The Loctite is to stop unscrewing and fretting.

[gipetto]

I have a pair of hydraulic cylinders on an articulated loader that are attached to their ends the same way, apart from the glue that is. they work fine.

[Minh Thanh]

 Hi Roger !
A Very Interesting Project
   

[Michael S.]

Hello Roger,

I've never thought about the hood piston. The piston that is integrated into the upper counter piston. I thought the piston was round. But it's square!
Does the piston have to be absolutely tight in its raceway?
It's still a big task to build the engine.
But you've already made it this far.

Greetings Michael