Paul wrote:

<big snip>

Sounds like supposition to me. The cast iron front housing will take
tons of thrust as will the six, six mm bolts.

Lets run some numbers.

The needle bearing  Life Factor is equal to Ca/(SF*P*HF).

Ca is Basic dynamic load rating. See below.

SF is speed factor at 6000 RPM the speed factor is 4.75
at 4000 RPM the speed factor is 4.25

P is the applied load or in your case the thrust lets say 350 pounds.

HF is the race hardness factor anything above Rockwell 58 is less than one.

I would guess the stock needle thrust bearing diameter is a 30 mm ID size.
According to the Torrington catalog. The 30 mm needle thrust bearing
has a 3560 pound dynamic load rating. Max RPM is 9100 RPM

Lets say you have 350 pounds of thrust and 4000 RPM
so your Life Factor with a 30 mm would be a 2.4. Looking that
up on page E71 of the Torrington catalog gives a L10 life of about 9000 hours!!

The plate is fine as is but a small increase in thickness would stiffen
it greatly.

I think the reason Tracy's failed it was pounded out by impact forces.

I was going to say, the only casualty in Tracy's estimated 800 lbs. thrust
was the bearing.

The larger needle prop thrust bearing in the Ross box gives no problems
and I would guess that it is a 55 mm size with a 9,250 pounds dynamic
load rating  and  5300 max RPM. The Life Factor is up to 3.6 so
the life is about 40,000 hours.

Mazda engineers are no dummies.

Get a Torrington catalog and check my calculations.

You have not noticed any increase in end play yet have you?

No, none at all.  The end play on the original bearings after being
run in a car for over 100,000 miles and on my plane for 100 hours
was in the middle of the range.  I replaced them anyway.

I will need to replace this engine at some point, but it is still running
strong.  Another race guy told me the engines start to loose power
about 80,000 miles in the car.  My car experience showed serious
degradation started around 175,000 miles, with failure at 209,000.

When I did the inspection at annual I saw absolutely no abnormal
wear in the bearings or the thrust plate.  I'm not really concerned
about the bearings anymore, but wanted your take on his comments
about the strength of the plate, front side housing, and the thrust
plate bolts.

BTW the clutch throw out load is way more than 100 pounds.
There was a hydraulic cylinder and a lever in most older set ups.
You are talking to the inventor of the annular hydraulic clutch throw out
bearing widely used on all manual transmission cars these days.

Paul Lamar

Impressive.  Thanks for taking a look Paul.

--
Perry J. Mick
Mick Duckt N7XR
http://www.ductedfan.com

 
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