Ohrndorf V12, new challange

[fumopuc]

As mentioned earlier this day, I wanted to be sure with all cylinder bores to be safe for any interference.
My idea was a classic go and no go test.
So I took a feeler gauge with 0,5 and 1 mm.
With this I have increased the critical distance of the small con rod eye into the "bad" direction.
By the 1 mm gauge, the rotation has been blocked between con rod and crankcase.
With the 0,5 mm gauge there should be a free rotation still possible.
So the test has been done with all cylinders in the same way with nearly equal results.
Inside in the V its was more critical than outside,  so main focus on the inside.
tbc...

[fumopuc]

And now at the end of this day, everything assembled again.
With the external jig all angle position has been carefully checked again, also clearance of con rods between the webs and the overall adjustment.
At the end my crank shaft build is 0,1 mm longer than the theoretical distance in the CAD, that should be fine.
Everything tighten with a hopefully reasonable torque.
And yes it is still spinning.
So next to do, cylinders and liners.

[petertha]

You did a good job milling out the rod clearance notches. I didn't get as far as you in my CAD model but I had an early hunch there was interference, which made me a bit suspicious what other things might be hiding? If he mentions 'file modifications' in the instructions at least it was addressed. I very likely missed it because my German is poor (sadly, despite both my parents were from Germany). But I think a token note on the plans would be helpful so you could be aware of the issue. These things could be dealt with on a casting, but us metal whittler's have to find a workaround.

Every engine has different layout geometry but what I found on my radial is relatively small chamfers on the rod corners resulted in significantly less material removal because the rod corners intersect the liner circle first. Chamfers or fillets on the rod corners would come at the expense of rod strength a bit depending on the amount. Maybe better suited to the 'dog bone' rod profile - or maybe that's why they look that way to begin with? A lot more work to do 12 rods x 4 corners plus spares. Anyway, looks like you have a nice, practical clearance gap with smooth fillets. Looks right to the eye. Personally I believe tight clearance gaps (even though they work on paper) is asking for trouble if one has to worry about a tiny bit of debris or wear causing bigger scuffing or seizure problems while running. Maybe clearance is why some rods were circular section even though rectangular might be stiffer.

For deburring all those corners, I really like those rubber abrasive wheels & cylinders on a rotary tool. Very controlled blending of corners & such. They are dirt cheap on AliExpress & Ebay. I found carbide burrs need to be really fine teeth & very high RPM, even so not as controlled if they ever dig in or zing off in wrong direction. But with the rubber abrasive, you really need to clean the parts well as the residue shavings can stick & hide in corners. I found hot water & dish soap & compressed air worked best on aluminum parts. I seem to get inconsistent results with my ultrasonic cleaner for some reason.

[fumopuc]

You did a good job milling out the rod clearance notches. I didn't get as far as you in my CAD model but I had an early hunch there was interference, which made me a bit suspicious what other things might be hiding? If he mentions 'file modifications' in the instructions at least it was addressed. I very likely missed it because my German is poor (sadly, despite both my parents were from Germany). But I think a token note on the plans would be helpful so you could be aware of the issue. These things could be dealt with on a casting, but us metal whittler's have to find a workaround.

Every engine has different layout geometry but what I found on my radial is relatively small chamfers on the rod corners resulted in significantly less material removal because the rod corners intersect the liner circle first. Chamfers or fillets on the rod corners would come at the expense of rod strength a bit depending on the amount. Maybe better suited to the 'dog bone' rod profile - or maybe that's why they look that way to begin with? A lot more work to do 12 rods x 4 corners plus spares. Anyway, looks like you have a nice, practical clearance gap with smooth fillets. Looks right to the eye. Personally I believe tight clearance gaps (even though they work on paper) is asking for trouble if one has to worry about a tiny bit of debris or wear causing bigger scuffing or seizure problems while running. Maybe clearance is why some rods were circular section even though rectangular might be stiffer.

For deburring all those corners, I really like those rubber abrasive wheels & cylinders on a rotary tool. Very controlled blending of corners & such. They are dirt cheap on AliExpress & Ebay. I found carbide burrs need to be really fine teeth & very high RPM, even so not as controlled if they ever dig in or zing off in wrong direction. But with the rubber abrasive, you really need to clean the parts well as the residue shavings can stick & hide in corners. I found hot water & dish soap & compressed air worked best on aluminum parts. I seem to get inconsistent results with my ultrasonic cleaner for some reason.

Hi Peter, thanks for watching and your comments.

[fumopuc]

Next part lot, cylinders.
Always two hidden in one cut off, was the plan.
Material is EN AW 2007.
Always a pleasure to press the 20 mm drill bit in it and getting nice swarf.
Only a sharp drill bit is needed.
4 pieces already after the first set up on the lathe.
Another 10 pieces are queuing beside the lathe.

[fumopuc]

More cylinders have past the first set up.
10 pieces done, another 2 still queuing and 2 already at the lathe, first operation done.

[fumopuc]

Another test with the new 1 mm parting off tool.
Same material as the already prepared cylinders and same diameter.
And my prepared 3D printed jig in action.
Another jig was 3D printed to adjust the angle later again.
Here used as a sample only to verify the machining process.
And the go for the 14 pieces of my prepared cylinders.
Two already done in the second set up now.

[Kim]

That looks really nice, Achim!  And I love your little 3D-printed spacing jig. That is very clever! 

Kim

[RReid]

Doggone it Achim, you keep making me daydream about buying a 3D printer...

[Admiral_dk]

Like Ron and Kim, I find your 3D printed Stop for the Cooling Fins very brilliant 

The Cylinders look great too 

Per     

[fumopuc]

Kim, Ron, Per thanks for watching and the friendly words.

Some development was necessary to get it work as it does it now.
First idea with a simple pin in the adjustable limit stop failed, to much possible tolerance.
The printed stop solved it at the end.
The overall shape of the big part, with the stairs, also has been revised two times.
Now it seams to be reliable.
Still 12 cylinders to machine in that way.

[Roger B]

Excellent  I do like the stepped block to set the spacing between the fins   

[fumopuc]

Excellent  I do like the stepped block to set the spacing between the fins 

Hi Roger, thanks.
In the meantime we have MK IV.
Another development step was made.
To get it easier and more precise to handle, I have increased the surface against the support.
Much better and quicker to adjust.


 

[fumopuc]

The whole lot of 14 cylinders does got the fins now.
And surprise, still all alive so far.
Optical quality check always against my sample machining from full stock.
Nearly the half was done with MK IV stepped jig.
Next will be the conical shape of the fins.

[crueby]

That is looking amazing, a LOT of work!