Finn writes:
Maybe, if I get hold of a end mill bit, I can "machine" the
rear bulkhead in
my drill press.
No way. Send me the box and I will do it for free except if I have
to farm out some parts for grinding. You pay for all parts
and shipping both
ways. I will need a new gear as no way can we salvage the
gear you have.
Or take it up to Tracy's and do it on his mill.
Finn, is your Ross bellhousing not machined on the back side, like mine?
I was thinking of adding a thrust bearing like your third drawing, adding a
plate to the back side of the bellhousing.
Chuck Dunlap
No, it's not. That's one of the reasons I'm very tempted to put the thrust plate
on the front side of the bulkhead. If I could just get some educated answers from
the engineer types on this list to the questions on minimum thickness of thrust
plate (I'm thinking 1/8" steel), minimum thickness needed for the pin (I think I
could go as low as 3/16") and consequences of using a thrust needle bearing
(designed to be piloted by the shaft) that's 1.5" ID instead of the 1.44" ID
(current shaft OD).
>From inside edge of support (8" circumference) for thrust plate to center of
thrustbearing race there's approx .5". How thick does the plate need to be to
support 1200 pounds?
2400 pounds over .72" (shaft radius) = 3333 pound/inch, over .028 sq inch (area
of 3/16" pin/bolt) would require 119000 psi bolt/pin shear strength, with a
safety factor of 2 (pin comes out through shaft and into sun gear at two points).
An AN3 bolt has 125000 psi tensile strength but is that also the shear strength?
I looked up the life of the 2mm needle bearing and it comes out to about 180
hours at 6500 RPM and 1200 pounds thrust.
As far as the shear strength of the pin is concerned Tracy already said
the friction does most of the work. I don't have a pin in mine. None what
so ever.
We may use two thrust bearings back to back just like Scott Speiror's unit.
The RPM is then cut in half for each bearing.
I mentioned that already. Are you reading these messages? Don't you
remember that? Here is the picture of Scott's unit again. Notice
the thrust bearings ride over the pin.
What is the life at 3250 RPM?
I have 13 mm available between planet gears and unmachined bulkhead.
13 - 3.6 (thrust bearing and race washers) - 4.76 (3/16" pin) - 3.175 (1/8"
plate) = 1.47 mm left over for clearance around pin.
Finn
You are confusing the hell out of me stick to inches or metric.
Forget the pin. The pin can go anywhere on a new gear and shaft.
The thrust bearing can ride over them.
No it can't. Tracy can sell me a sun gear cut (ground) to length I specify. There's no
way we can machine a recess into the sun gear for the thrust bearing and no need. It'd
be far less work to mount the thrust bearing thrust plate on the rear side of the
bulkhead.
Not true. Yes it can. I will have a drawing tomorrow now that I have the
right dimensions.
How thick is that seal? Are you sure about that 1/8 " seal
counter bore depth? Take a picture.
Current seal is 5/16" wide, 2.75" OD, and 1.75" ID: CR-17558-USA,
but needs to be replaced with a 1.44" or 35mm ID seal.
Let me explain: The current sun gear has been ground down to 1.75" OD along 1.5" of
it's length and sticks out back past the bellhousing bulkhead, with the seal riding on
the ground down part. The pin is also in the ground down area, forward of the seal, but
behind the teeth. We are not going to do that with the new gear. The new gear is simply
cut to length (just long enough for the planet gears and pin) and ground flat. The
thrust bearing will rest against the ground side and the thrust plate against the other
side of the thrust bearing.
OK so we go with a 1.75 ID thrust bearing.
>From Tracy's comments about omitting the pin, I figure a 3/16" pin will be fine for me,
and if you can confirm that a 1/8" steel plate can take the thrust load, I'm all set.
I won't know that yet until I make a scale drawing with all the proper dimensions.
Well, except for one thing. What happens if a thrust bearing that's designed to ride on
a 1.5" shaft rides on a 1.44" shaft?
If you think that that will reduce the bearing life more than 50%, I'll have to go to a
35mm ID thrust bearing and have the shaft machined down from 1.44" to 1.378" (35mm).
Finn
What is the ID of Tracy sun gear? The one I have is 1.45" ID.
What is the OD of the pilot shaft extension that extends beyond the gear and
into the output shaft?
You still sound like you still want to use your old shaft.
Have you been to a junk yard and looked for a used shaft yet?
This is a piece of cake Finn. Calm down. No big deal. cheap to fix
in fact. Much cheaper than $1500. Have a bit of patience.
Paul Lamar
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