Since Tracy is no longer doing it, who is supplying a good redrive? Lots
of good designs using Ford parts, but would like to avoid having to
fabricate the housing, spline adapters etc.
David Josephson
Cozy Girls said they were going to do it when I spoke with them
at Sun N Fun.
I hope Neal Ungar does it. I would have more input :)
I would like to do it but I have my hands full with this ignition
system.
Paul Lamar
David,
Paul is correct in that I am trying to get redrives made. BY
the end of this week I hope to have the CAD drawing done to see if it all
fits and works. The biggest difficulty I am facing is to get the machining
done with CNC at an affordable cost. Aust is full of sharks and I am not
talking the oceans. The redrive will be the 3.17 ratio and will fit
exactly where Tracy's redrive exists. I am leaning towards two timken taper
bearings on the prop shaft. Yes it may be a weight penalty, but will be
indestructible. and I will sleep at night. Weight saving can be made in the
housing and the flex drive, so that the overall weight will hopefully be
lighter than Tracy's.So far the dreams.
Neil Unger.
There is another factor to consider about Tapered rollers Neal.
The shaft is 8 to 10 inches long and the housing is aluminum,
That means the fit of the tapered roller bearing will vary with
temperature.
Jeff Spitzer was the project engineer on the famous GAT Predator drone
that has killed many terrorist.
Here is a real old message on the subject.
.
Paul Lamar
Old message:
-----------------------------------------------------------------------------------
-------- Original Message --------
Subject:New PSRU design
Date: Thu, 26 Aug 1999 18:20:14 -0700
From: Paul <
rotaryeng@earthlink.net <mailto:rotaryeng@earthlink.net>>
To: zz <
rotaryeng@earthlink.net <mailto:rotaryeng@earthlink.net>>
Jeff Spitzer wrote:
At 03:02 PM 8/26/99 -0700, you wrote:
>I finally got around to getting a Timken roller
>bearing catalog. IMHO tapered roller bearings are
>the way to go. They are light weight for the thrust
>load handling capabilities and compact.
Note that in a later post you quote the thrust load from the sun helix as
greater than what the prop will likely produce. Yet you chose two ball
bearings for the thrust of the input shaft.
I will take a look at back to back tapered bearings for this
application. Do you think my calculations are right for
the helix thrust?
I would suggest that you abandon the pilot in the e-shaft and add a
flywheel-end bearing to your input shaft.
Do you mean abandon the pilot in the output shaft?
One needs a pilot in the output shaft for the sun gear
shaft.
If you do indeed mean the pilot in the e-shaft yes I think
that will work. However any bearing added would then act as a pilot
would it not. I am a little confused on what you have in mind here.
Would'nt this limit the diameter of the bearing? I'll consider it.
can you make a sketch and send it? I am open to all suggestions.
I suggest this because
planetaries are very sensitive to centering properly and the notion of
accurately aligning the whole gearbox to the e-shaft is not a good idea
IMHO. Note that the clutch center is capable of dealing with as much
misalignment (more) as the plantaries if done right. Perhaps you would now
choose to use tapered roller bearings here too. I'm not sure you would
want to.
The differential CTE of the aluminum housing vs. the steel input[output?]
shaft causes the bearings to either loosen or tighten with temp.
Tightening is not bad as long as you let it warm up before you run it hard
(and build it a little loose at room temp). Loosening is very bad indeed
unless you build it very tight. Either way when the bearings are loose the
shaft will misalign.
Jeff Spitzer
I knew you would say that. I am going to warm the housing to 200
F when I adjust the tapered roller bearings preload. Other options are
to make the output shaft out of aluminum or the housing out of
steel. A steel housing is not a bad way to go as it could be rather
thin wall.
I am counting on the low modulas of elasticity of the planet carrier
to adjust the centering. I think that is what Ford had in mind when
they choose aluminum in the first place. Chrysler uses steel and
they have had a lot of trouble. GM uses steel or cast iron
but I will bet they hold tolerance real close. Another factor
in the centering is the output bulkhead is splined to the
ring gear so the ring gear can float somewhat relative to
the sun gear and planet carrier.
Thanks for your thoughts on this Jeff.
Paul Lamar
---------------------------------------------------------------------------------------------
I would be inclined to put the roller bearings back to back for end
thrust control and use a journal bearing or roller bearing to support
the other end.
When the tapered bearings are close the CTE becomes a non issue as the
amount of metal experiencing the differing expansion rates is minimal.
Yes weight is affected but durability is impoved and setting of preload
is taken out of the equation. Just another one of those compromises that
need to be dealt with.
Dale Davies
Yes that will work but IMHO unnecessary, costly and over kill.
Weight is critical in this location.
The Ross was first built in 1973. Thats 40 years ago :)
Hundreds where sold and thousands of hours of experience were accumulated.
It was ten pounds lighter than Tracy's and better IMHO :)
IMHO old Lou Ross got it right :)
Paul Lamar
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