Ohrndorf V12, new challange

[petertha]

You maybe have already encountered this with your other engine builds but mentioning FWIW. On my Ohrndorf radial, I made a fixture to drill the ~1mm oil passage holes. What was a nice lapped fit before this operation turned into slight some resistance on the crank pin. I was worried I distorted the main hole a bit, but turns out a micro burr can form on the exit hole, even though it was supported by a dummy fixture pin. You don't want to go back in the main hole with a reamer to de-burr. And re-lapping can be counter productive & wear the face of bronze when all you really want is the burr gone. So a better fix IMO was a spherical ball ended diamond burr like on a Dremel rotary tool & relieve the hole from the inside, almost like an internal countersink.

[gerritv]

Incredible workmanship and fixturing on this build.

Gerrit

[Art K]

Just wanted to let you know that I am watching along with interest!
Art

[fumopuc]

Thanks Peter.

Hi Gerrit, Art, thanks for watching. Good to know you are following along.


Some more experiments has been made, this time more virtual ones.
First I would like to know more about the cylinder and piston assembly.
So the cylinder and liner has been modeled in the CAD, a good opportunity to send it to the 3D printer and to get something to hold it in the hand.
These parts are really tiny, 21 mm bore and 21 mm stroke is not very much.
The new parts in the CAD model gives me now the basic for an animation of the crank drive with the CAD model.
<a href="https://www.youtube.com/watch?v=1vmKm8RziN4" target="_blank">http://www.youtube.com/watch?v=1vmKm8RziN4</a>
Here I could see  also a small collision between con-rod and crankcase, inside in the V.
This was mentioned by the designer already in his description, coming together with the plans.
Nothing serious, sure can be removed by  some strokes with a file.
For me this research is a good help to understand the overall design hopefully better.

[ozzie46]

Another one following along. Great job!
Ron

[petertha]

Is the collision you are detecting happening between the rod & crankcase lip, or rod & liner skirt chamfer? Hopefully not both. I made this mistake myself stopping at only on the first collision occurrence thinking I fixed the problem.

Its amazing how many times you see this on model engines & I suspect I know why. If you make a cross section through the center of the rod/piston, you may well see clearance daylight between rod & other surfaces. But what is more important is take a section down the FACE of the rod, because it will be seeing the curvature of cylinder bore features. Radials even have one more potential trap. Rods angles can vary by cylinder depending on layout geometry, whereby you can have clearance on some cylinders & interference on others. Thankfully many CAD packages can show exactly where & how much interference.

[fumopuc]

Hi Peter, you are right.
The small collision is not only inside the V, as shown above in reply#123, picture "Pleuel 60", the two red triangles, it is also at the other side.
Here also shown by the red triangles.
The liners do not have an contact.

[fumopuc]

Another one following along. Great job!
Ron

Hi Ron, thanks, good to have you following along, too.

[fumopuc]

Some more CAD work done.
Cylinder heads and valves are redrawn.
Rockers and rocker bearings are missing still, inlet manifolds and exhaust pipes, also.
There is a strange lay out with a M10 nut clamping a tube into the head.

[Vixen]

Hello Achim,

It may be a good idea to check that your pistons do not collide when they are near BDC. That happened to me with my big Bristol Mercury engines. Here is a quote from one of my posts

{quote]
Here are the cylinders in place. It's looking like the job is completed. But NO, 'Houston we have a problem',  the engine won't turn over. Several of the piston skirts are clashing as they pass BDC. I have forgotten one small, but essential, machining stage; the tiny 20 degree flats on the bottom of each pistol skirt.




The piston chamfers are clearly shown on my drawings but somehow I managed to ignore them. You can see the cylinders already have a 20* chamfer on either side of their skirt, to prevent them touching each other deep inside the crankcase. The pistons also need a similar 20* chamfer to prevent clashes.






Interestingly, the piston skirt collisions only occurred in the cylinders opposite side to the Master rod. This clearly demonstrates how the reciprocating motion of a radial engine's pistons differs with individual cylinders due to the Master/slave rod geometry. The greatest geometric errors always occur on the side opposite to the Master con rod.

[/quote]

[fumopuc]

Hi Mike, the pistons seems not to be critical.
It is really nice, if you can animate all motion in the CAD model.


Maybe the faulty mainbord battery in your computer will say, "He Mike, it is time to change and to buy a new (refurbished) computer with Windows 11".


   

[Vixen]

Maybe the faulty mainbord battery in your computer will says, "He Mike, it time to change and by buy new (refurbished) computer with Windows 11".
 

Ha ha. I do have another PC with Win 10 for my normal 'office' work. I use the Win XP to run my legacy CAD and CAM software.

Interestingly, I love the 'feel' of Win XP, I don't get the same comfortable 'feel' from Win 10, Would Win 11 be any better or worse?

Mike

[fumopuc]

Hi Mike no idea about Windows 11 so far.
All my / our Pc´s in our house are refurbished desk top pc´s  or note books.
All of these , including my HP workstation are not useable with Windows 11, if I believe the test program and check.
So I have to find a solution maybe latest end of next year if windows 10 will be not be supported anymore.


By the way, my CNC controller will be driven by an old refurbished Windows XP PC also.
Only Eding CNC there, no Network connection, no up date sine years, no other software installed.
Only disadvantage so fare, I have to quit the impossible attempt of Windows with its try to call to Redmond.
He tries it every time but he is not allowed to do it.
Than he is offended and tells me somethings about, it could be dangerous and my Windows could be illegal, he does this since years.
When I have  purchased this refurbished PC some years ago, he spent one night and half day at the network and getting official updates.
After this he has never seen a network cable again.

[petertha]

My eye was drawn to what looks like an annular ring slot beneath the cylinder/liner assembly. Is that simply a bit of extended counterbore or does it have some other purpose? Your pictures remind me of similar issues I modified on Ohrndorf radial. I made the cylinder flange component flush but extended the liner length deeper into the crankcase. So the liner OD guides into the crankcase with a slip fit & its a smaller diameter hole. I used a thin (0.001") PTFE gasket under the flange which I recommend. He had an O-ring at the cylinder base which seemed kind of complicated & I was not keen on aluminum / aluminum fit for potential galling. I mention this on the off chance he had some kind of seal at the base of liner although I rather doubt it. (Mein Deutsch ist schlecht und seine Anweisungen waren eher kurz HaHa)

[petertha]

... inlet manifolds and exhaust pipes, also. There is a strange lay out with a M10 nut clamping a tube into the head.

You may not have these same issues on the V12 but I struggled a bit on the O5 head prototypes. Prototype is my fancy word for scrap pile haha. FWIW link to some pictures of my tubing bending, trumpet bending, ports & coupler nuts... The ports were quite shallow & threads have only partial contact due to fins & maybe complicated if the entry axis is non radial. I ended up widening the head but I don't want to detract your post any more with this story. But I did incorporate a Teflon washer between the tube face & counterbore which I feel is very useful to seal & vibration & thermal expansion etc. But the washer also comes at the expense of using precious remaining space in those shallow depth ports. Good luck, It looking amazing!

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