The Home Machinist!

Hu Guys,

interesting Discussion.
Here some pics of my new Rods,
made by stainless Steel (1.4571).
The roller bearings arrived me on Friday,
so we could mounted the Rods with bearings
for the first time. The wheels moved very easy.
Good to see that all tolerances fit and work together.
Regards
Chris

Nice!
Please discuss the boring of the bearing seats.

Harold

Hi,

next Set of the Rods, right side Tandem Rods.
Harold,

the bearing seats are made by the mill.
The seats have a diameter 0.01mm smaller then the bearings.

Regards
Chris

Do the rod bearings have any allowance for independent axle motion, where one wheel set moves out of parallel from the other ones?
~RN

Hello NP317,

look, the bearings have no chance to move on
the Bolts. The movement of the axles will equilized
by the rods. Because of the cut outs in the rods, they can move
by itselfs. We've tested it, one eye was in the vice, on the other end
we pulled with a dynamometer. By a force of 8Kg the rods moved
in pull direction 3-4mm. The axles can move +/- 2mm so the rods
ca follow easily.

I hope that is what you mean.

Regards
Chris

Hi Guys,


some Smartphone footage of the last weeks.....i hope you can enjoy...


https://www.youtube.com/watch?v=NIYl3k3 ... e=youtu.be




All the best
Christ

Harold,
You head it! Fits are most critical due to the tiny ball bearings used for the connection rods. Construction was made different to that of the prototypes which used compact pairs of tapered roller bearings pressed onto the cranks. The outer races glided in bronze bushings which were rolled into the rod eyes. That construction allowed to remove the rods very easily and gave a small amount of play, too.
I regret, but tapered roller bearings of needed dimensions are not available. To overcome problems I found a solution which worked properly in my class 44 for some 20 years.
This construction was adepted to the dimensions of the Timken running gear of my class A 1239 some years ago (photos).
To meet the needs of steamchris' class J 611, the special tandem rods had to be considered, too. The tandem roods needed to be milled very precisely!
The cross sections of both connecting and main rods were to be milled very slim (like those of the prototypes) to reduce stiffness against torsion. Please look at the scans which are showing dimensions of prototype versus [model in brackets in mm].
Bearings (made of stainless steel, too) were pressed into the connection rods as steamchris desribed already. The fits on the cranks had been smoothed to about - 0.01 mm to allow to mount and disassemble the rods without excessive strength.
The inner races and intermediate washers are pressed tohether safely onto the cranks by means of the outside caps. Small (loose!) rings made of bronze between the bearings will improve sealing. Lubrication greece is to be pressed into the hollow cranks from the outside once a year. Distribution is achieved by cross bores between the inner races as to be seen in one of the photos.
The construction of the Timken crosshead is a little more sophisticated, yet. The topic of my A 1239 is showing more details, please have a look.
A lot of construction work and precise milling will be weighed against engines running very smothly and powerful with roller bearings all out.

Asteamhead

Thanks, gentlemen, for the replies. I'm impressed!
The one thing I wanted to learn wasn't answered, as I was not specific. I'm just curious.
Were the bearing bores interpolated, or was a boring head applied? I'm curios if interpolation will offer the level of roundness that would be desirable, in other words. I expect that would depend on the quality of the mill, but does it?

Harold

Morning Harold,

im sorry, didn't understand you correct.
Look, the machine i used is a very good CNC Mill,
from a Company called "Hermle" some people say, the Best CNC Machines ever....but those exacly bores are absolutly Standard! !!
My machine have a roundness tolerance of 0.001 to 0.002mm .
So, those bores are no Problem. You can change the bores diameter by correcting the Radius of the milling cutter.
Smaller = bigger bores ! Thats the way how the correct and exacly diameter was made.

The bearing seats are cycle made, a ready to Mill Programm You just have to type your values into the cycle and the machine Starts milling by the optimale way.


Some Infos about Hermle milling machines....

https://youtu.be/E1e5p2JOtbU




And some Infos about cycle based milling
Just some footage showing round cut out milling

https://youtu.be/r7xdDRWagpc




All the Best
Chris

Steamchris wrote:My machine have a roundness tolerance of 0.001 to 0.002mm .
So, those bores are no Problem.

Thanks, Chris. Truly amazing what CNC has done for the machine shop. The numbers you quoted would have demanded a jig borer in my day.

While I didn't understand the first video, it, like the second one, was enjoyable. Thanks for your efforts in making them available for us.

Harold

Harold,

yes, in the last years the CNC-Milling
is very far. Look, new machines are able to be
a Mix out of lathes and milling machines.
The new Hermle C60 combined both of those machines.


Have a look at this.....

https://youtu.be/Xi6QTAf4KSA


Awesome in my opinion.

Kind Regards
Chris

Steamchris wrote:Hello NP317,

look, the bearings have no chance to move on
the Bolts. The movement of the axles will equilized
by the rods. Because of the cut outs in the rods, they can move
by itselfs. We've tested it, one eye was in the vice, on the other end
we pulled with a dynamometer. By a force of 8Kg the rods moved
in pull direction 3-4mm. The axles can move +/- 2mm so the rods
ca follow easily.

I hope that is what you mean.

Regards
Chris

Chris:
If I understand correctly, the very thin profile of the side rods allow them to twist longitudinally, compensating for independent axle movement. Remarkable! I was not aware that was done on the prototypes. This explains much!

Your work is amazing, and I enjoy your posts. I always learn something.
Vielen Dank,
~Russ