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1. 09:28 AM - Re: Torque Tube Rod (John Dilatush)
2. 10:19 AM - Re: Torque Tube Rod (Phillips, Jack)
Message 1
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| Subject: | Re: Torque Tube Rod |
----- Original Message -----
From: alexms1@comcast.net
To: pietenpol-list@matronics.com
Sent: Tuesday, March 08, 2005 2:08 PM
Subject: Re: Pietenpol-List: Torque Tube Rod
Alex,
I am not sure now since I sold Mountain Piet and can't measure the diameter of
the spreader bars on the plane.
I also sent the buyer, Greg Bacon, the plans for the plane. However, if my aging
memory is correct, I followed the sizes shown on the plans. I think if you
increased the diameter/wall thickness from that shown by maybe 25% you will
be ok. Even if you follow the sizes shown, there is no real problem, the spreader
bar simply bends a little more under a braking load
John
John,
I am still studying your words of wisdom so when I get to my axle installation,
I will have good info to work from. Your comment about "next time using spreader
bars with thicker walls", what did you use and what would you go to?
Thanks so much.
Alex Sloan
-------------- Original message --------------
----- Original Message -----
From: David Paulsen
To: pietenpol-list@matronics.com
Sent: Thursday, December 09, 2004 5:06 PM
Subject: Re: Pietenpol-List: Torque Tube Rod
Dave,
Pardon me for jumping into this discussion about how to keep the straight
axle from rotating when the brakes are applied.
May I suggest an alternative method of doing this so that the axle is free
to move in any direction without excessive strain on welded joints? I also
believe that the integrity of the axle is not compromised by cutting a hole through
it and I think this is a lighter solution to the problem.
I have attached a photo of the installation on my ex- "Mountain Piet". You
just weld a couple of 3" tabs on the top and bottom of the axle in the middle.
Do the same thing on the rear spreader bar. Now drill some 1/4" holes at
the top and bottom of the tabs to use Heim joints. Then connect the Heim joints
with a 1/2" round aluminum rod drilled and tapped for the 1/4-20 threads of
the Heim joints so that when when the whole thing is assembled you have a parallelogram
formed by the tabs and links.
The system works well. If I were to do it over again, the only change I
would make would be to use a rear spreader bar with a little thicker wall so that
it is not as apt to bend under loading.
Hope this is helpful in your decision.
John
Thanks Jack. Perhaps I will try to find two 8 inch pieces of pipe that can
slip tightly into my axle - position them so there's about 4 inches of pipe
on either side of the holes - and drill them through. This will double the thickness
of the axle in that critical area acting as reinforcement in case there
is a exceptionally hard landing.
Dave Paulsen
----- Original Message -----
From: Phillips, Jack
To: 'pietenpol-list@matronics.com'
Sent: Thursday, December 09, 2004 7:10 AM
Subject: RE: Pietenpol-List: Torque Tube Rod
Dave,
The guide pins don't have to be welded. However, just putting a hole through
the axle causes a stress concentration. My axle broke at the guide pin,
but my axle was only .120" wall. My new axle will be .188" wall, and I will
have it heat treated after welding to raise the yield strength to 105,000 psi,
which will make it about 50% stronger (and 8 lbs lighter) than a .25" wall axle
non-heat treated. I am also going to change the design of the guide pins
to allow the holes through the axle to be on the neutral axis so any stress concentrations
caused by the holes will not matter.
Jack Phillips
Slowly beginning to repair NX899JP
-----Original Message-----
Why does the bolt or rod that some of us have put though our straight though
axles have to be welded? I'm probably missing something obvious but I don't
know what. The rod can't jump out of the axle because there is a nut at
the bottom that will prevent it from coming up through the torque tube. Thanks.
Dave Paulsen
Message 2
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Being somewhat interested in alternative ways to carry braking loads, I
just ran some numbers to see which would be of more benefit when using
John's design - thicker walls or larger diameter for the spreader bars.
I ran some quick calculations, assuming my memory is correct and the
plans call for 1" x .035" wall tubing for the spreader bars. I don't
have my plans here so I can't check them.
Anyway, if you started with 1" x .035 and wanted to go one step bigger,
you could either go to 1" x .049 or 1-1/8" x .035. The larger O.D.
would be preferable, for a couple of reasons:
1. The larger OD will give a higher section modulus (measure of
torsional stiffness) - about 44% more than the original size, whereas
the thicker wall will only give an increase of about 34%
2. The larger OD with .035" wall is lighter than the original OD
with .049" wall
3. The larger OD tubing with .035" wall is cheaper than the
original OD with .049" wall
4. The thinner wall section is easier to flatten on the ends
(which the spreader bars require) than the thicker material would be.
Jack Phillips
Raleigh, NC
----- Original Message -----
From: alexms1@comcast.net
Subject: Re: Pietenpol-List: Torque Tube Rod
Alex,
I am not sure now since I sold Mountain Piet and can't measure the
diameter of the spreader bars on the plane.
I also sent the buyer, Greg Bacon, the plans for the plane. However, if
my aging memory is correct, I followed the sizes shown on the plans. I
think if you increased the diameter/wall thickness from that shown by
maybe 25% you will be ok. Even if you follow the sizes shown, there is
no real problem, the spreader bar simply bends a little more under a
braking load
John
John,
I am still studying your words of wisdom so when I get to my axle
installation, I will have good info to work from. Your comment about
"next time using spreader bars with thicker walls", what did you use and
what would you go to?
Thanks so much.
Alex Sloan
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