IHC Titan 50 HP, 2 cylinder Doug Kelley, European version

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Hi everybody.
Now we need something to move the valves in the head.
So I have started with the rocker arm brackets.
Two pieces are needed, so I thought they could be both hidden in a round piece of AW 7075 bar stock.
Finally my assumption was right and the CNC mill has found both pieces in that piece of aluminium.

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... a second and third set was necessary to bring to an end at the CNC mill.
The M 1,6 was cut manually.
At one corner the is very little damage, I thing it caused by an incorrect adjustment of my CNC mill table guidance.
 

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... next step, to get them split from the  bar stock.
This was done by the lathe.
The conventional mill than was responsible for a proper surface and the correct height over all.
Finally the brackets in situ, they are not really big.

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Next to do, some rocker arms.
Also, in my eyes, very tiny parts.
Having several ideas in mind and rejected again, the conclusion was to make it this way.
<a href="https://www.youtube.com/watch?v=Osz4Odw9slM" target="_blank">http://www.youtube.com/watch?v=Osz4Odw9slM</a>
It took min 4 or 5 times longer to do the CAM than the final milling.


 

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The start was a proper prepared plate of AW 7075 aluminium.
And than some swarf over all.

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The G code has had something about 56.627  lines including some finishing operation.
But something was going wrong there during finishing the circles of the bosses around the shaft bearingss.
See the red marking.

During the milling operation I have noticed for a very short time a strange noise already.
It was a kind of growling.
I do know these noise, it does get created by the stepper motors if the are blocked.
I do have no closed loop at my CNC mill.

The visible failure in this case was, I have get at 4 rocker arms an offset in X and Y by nearly 0,5 mm.
My brain start to steam and I could not find any explanation for this issue.
A break for lunch time and cleared head after this given my the idea for the right way of analysis.
After a check of the entire CNC mill, if there was anything what could block the table in X and Y temporary, what in my eyes is nearly impossible, my attention was tracked into an other direction.

If there is nothing mechanical what does show two stepper motors a limit, than it must something different.

Some deeper diving into my CAM program does lead my to the feed rate of the final 0,1 mm finishing operation.
The crazy and optimistic guy at the computer has selected there 2.573 mm/min.
In theory, combined with the 24.000 rev of the spindle and the small 3 flute cutter, not so unrealistic, but over the limit of the performance of my stepper motors.
Conclusion, I have simply hit the limit of my CNC mill machine.
The very small circle and the very high feed rate did not match anymore in this case.
The stepper motors are at their limit, but get further pushed by the controller.
They show this by the growling noise, losing some steps in X and Y, and the result is visible at 4 rocker arm.
Why it was not at #5, no idea.

To confirm my failure analysis, the feed rate was reduced and the operation repeated with success.
If I will make new parts or I can life with these, will be a decision for later.

The tool was changed regularly now and the next operations making more swarf.

The very last picture is the end of roughing out and finishing of this set up here.
May be I can live with it, if there will follow no further accidents.

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The last operation in this set up, some more or less precise holes, made by drilling and reaming.
Now a new set up and the end of this operation already.

[Admiral_dk]

I do understand the fustration - but I always find it gives me 'Peace of Mind' if I can identify the reason for the problem and a solution + it really lessens 'the Pain' if I didn't ruin any tools ....

So all in all - not bad + and the rest are good Parts  Achim   

Per

[Kim]

Wow, Achim!  A lot of really good CNC work.  Nice walk-through of the brackets and rocker arms. 
You did some great sleuthing work to figure out what was going wrong with the rocker arms too.
Very interesting to follow along on your journey! 
Kim

[internal_fire]

The crazy and optimistic guy at the computer has selected there 2.573 mm/min.

I read that line at least 5 times while thinking that seems very, very conservative. Then I remembered the comma vs. dot differences. 

Very nice work! 

Gene

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Hi everybody,
today I have lifted the dust cover over the TITAN build again and after some orientation also some progress was made.
Unfortunately and additionally  the build report here, last edited here in March last year, is far behind the reality.
I will try again to catch up.


I have seen, that the rocker machining is still not finisher here so I will complete it first.
Alls machining from sides was done so far.
Next step to flip them around and to prepare the last last side machining, but first to find a reference point. I took  the middle hole.
Than the material was removed to level of the part surface in a small slot, wide enough to have space for some bolts.
This dimension is the overall width of the rockers at their bearing.
The challenge now was, to fix the whole story in a way, that after/during the final machining the single rockers could not move anymore.
A plate as a fixture was prepared, also drilled by CNC, with 5 threaded holes and 5 holes for pins.
The width of the previous mentioned slot was calculated also in way, that the 5 mm mill could start immediately beside the heads of the bolts without a collision.
Now the swarf was getting more and more and the shape of the rockers also.
tbc 

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.. and next steps of the rocker machining.


tbc

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... nearly finished.
Some minor scratches, for me and my mill impossible to avoid by the multi set up machining.
It can be polished.
First time in situ also.
Next step was a bore and a thread in each rocker.
Also made by the CNC mill.
Some bolts for adjustable valve clearance made also.


tbc

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... 4 rockers for the TITAN cylinder heads.


tbc

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The bearings of the rockers need some completion also.
Some very thin shims has been used as thrust washer.
The damage, due to the earlier shown little CNC crash is visible, but only for people who knows it.
Decision is done, the parts will stay like they are and no new batch necessary.