Ohrndorf V12, new challange

[fumopuc]

Hi everybody.The  CNC milling is done, the remaining unfinished tapping is also done by hand.
But still two places where machining, drilling and threading is necessary, on the faces front and rear.
No chance to use the little Proxxon CNC mill, so the plan was to go the conventional way.
A little mandrel was made to fix the crankcase at a defined place on the mill table, useful for a flip around also.
For the centering, Todd´s self made coax indicator in use, very useful, due to low space in Z at the mill, supported be a MK2 direct collet.
https://www.modelenginemaker.com/index.php/topic,8677.msg189574.html#msg189574
The coordinates at a drawing and tapping by hand.
 

[Vixen]

Hello Achim,

Nice work.

That's some really fine work on the crankcase.     Not much of the original block of aluminium left. I bet you feel relieved now it is finished, without a hitch.

You convinced me that I should make one of those low profile coax indicators, so I just checked Bill Todd's page but find the link to the PDF drawings no longer works.

Cheers   

Mike

[fumopuc]

Hi Mike, thanks.


In the meantime we got some con rods.
It it designed as an assy, with the con rod by aluminium AW-7075 and two bushes made from RG7, similar 660 bronze.
Thickness is 5mm, so it could be made from a standard plate material.
My decision was to make two batches of 8 pieces each.
3 set ups at the CNC mill with a conventional reaming between first and second set up.
The CNC had to machine the holes to 4,8 and 6,8 mm by drill milling with a 3mm cutter.
The reaming followed for final dimension.
Flipping over of the whole plate for second set up. 
Shortly interrupted by a leakage of the coolant, nothing serious, quick fixation was possible easily.
tbc ...

[fumopuc]

... pocket at the other side first milled and than followed by cutting out each single part.
Process was successful and proofed now so the next batched followed immediately.

[Roger B]

Very nice  How long did it take to machine both sets?

[fumopuc]

Hi Roger thanks.

The second set was a bit quicker, here it was 50 Minutes for the upper side and 140 minutes for the lower side.
I have been very carefully with the 4 mm cutter, specially with slot cutting.  Ap was 1 mm only and the entrance according to the contour by a smooth angle each time going down very slowly. So a lot of fear has been involved also. But the cutter is still alive.
The final shape in the pockets was done by a 3 mm ball cutter.
This is very thin and an issue for vibration and chatter, so her also I haven been far far away from my usual feed rates between 1200 and 2000 mm/min.
I took some time to figure it out. So at the first batch I have tested each operation by a single part only, also with a iteration at a single part before doing the "production run".
That was the reason, why we have 16 pieces in work for a V12 engine.

[fumopuc]

Conrods, progress.
First the Dremel to cut them out.
Next was to make a fixture to grab them for the last set up.
tbc ...

[fumopuc]

... to get a proper surface around the con rods, I have made the shape at the fixture a bit smaller as the contour of the part.
So the cutter has had never contact to fixture.

And now they are waiting for their bearing bushes, 36 pieces and no CNC lathe available.

[Kim]

Very nice, Achim!  Great looking con rods.  All 16 of them! 

Kim

[fumopuc]

Very nice, Achim!  Great looking con rods.  All 16 of them! 

Kim

Hi Kim, thanks.


Next and new challenge, main bearings for the crankshaft.
Partly a CNC machining is possible, if the basic job has been made conventional at the lathe.
Below some CAD pictures how the are looking like.
Also the scheduled tool paths.
Drilling will be started with a short VHM drill bit and later finished conventional at a drill press.
I have prepare a piece of a AW 7075 aluminium at the lathe as a kind of raw close to the final needed dimension, but still some overstock.
So I like to make each individual bearing step by step.
There will be enough material to make min 6 pieces, one set up part and 5 pieces for the V12 minimum in these stock.
First a 23,97 mm hole for the ball bearing, which will pressed into it directly.
The outer diameter should be 0,02 to 0,04 mm smaller than my center bore in the crankcase, which is 42,19 mm.
A real challenge for me.
tbc ...

[fumopuc]

... we have the beginning here, two parts with slightly different outer diameter, 0,02 mm, are hosting a 9 mm drill rod bar as a dummy.
Some unusual measurement tools at my desk and in use to keep control.
At the end I have made 6 pieces to get 5 of them as the ones needed, plus one set up part and the shaft is still moving.
I have knocked the part by a soft hammer into their hopefully  final positions at the ground of the circle.
And surprise after a lot of measurement, swapping and matching them around, I have a combination of 5 of them, which seems to run together still.
<a href="https://www.youtube.com/watch?v=kS-b9_Kv3JA" target="_blank">http://www.youtube.com/watch?v=kS-b9_Kv3JA</a>
Next step, to check my CNC machining, if it will give me what I have wanted.
This first check was made with the extra set up part first.
After a slightly modification of the diameter for the M4 bolts it was easy to assemble.
At the end of this day we have, the set up part and #1 and #5 final machined and bolted to the crankcase.
The shaft is still movable, so let´s see what will happen, if I add #3 next.[size=78%] [/size]

[Admiral_dk]

Interesting construction 

Glad to see that you got a sequence that runs well together Achim 

Per         

[fumopuc]

Interesting construction 

Glad to see that you got a sequence that runs well together Achim 

Per         

Hi Per, thanks for popping in.


Today I have finished the remaining bearing blocks and added them with bolts step by step.
#3, #4 and finally #2
And totally surprised, there is still movement.
<a href="https://www.youtube.com/watch?v=aRtM302bV-M" target="_blank">http://www.youtube.com/watch?v=aRtM302bV-M</a>


I think it is time for a beer per each bearing block now.
Sure not the Bavarian 1 liter "Maß", but maybe the 0,1 liter "Kölsch" from my home town Cologne, still available in some "Brauhäusern" downtown.

[RReid]

Hello Achim. Enjoy those beers, they are well earned!

[fumopuc]

Hi Ron, thanks and I am down to earth again.


I had to sort out some issues with the drawings.
I am very glad that I have remodeled all the design so far in my CAD, so I have somethings I can trust 100%.
Next to make was the rear bearing plate at the crankcase.
This will host the gear train also.
There are no real dimension for the position of the idler gears at the drawing.
The designer has given an recommendation only, to mark them when all other related things are finished.
That means crankshaft gear and camshaft gears in final position.
Always a good idea to do it like this.
I have done it virtually in my CAD to get an general idea about it.
The original drawing does show the gears in one horizontal line.
For copyright reasons, here the link to the picture at Mr. Ohrndorf´s shop page.
https://www.engineman.de/wp-content/uploads/2019/06/12-zylinder-v-motor-bauplan01.jpg
In my CAD model is does look different.
The gears are purchased by Mädler, exactly the same as shown in the BOM.
It was a reason for me to redesign the hole surrounding a bit, plate and cover of the gear housing.
Now I am happy with it, even if it is different to the original design.
I have made some dummy  parts with the 3D printer to confirm it with the already machined crankcase.
At the end it has affected the bolt position at the rear bearing plate also, the part I want to make next.