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Front Wheel Axle Spacers - A Permanent Fix

 
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effectus(at)rogers.com
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PostPosted: Sun Dec 21, 2008 7:36 pm    Post subject: Front Wheel Axle Spacers - A Permanent Fix Reply with quote

Hi Everyone,

I want to share with you the permanent fix that I have come up with for
the front axle spacer problems we have been having lately. We have seen
everything from gouging of outer yokes to the bearing spinning on the
axle due to the loss of bearing pre-load.

I decided to take a real close look at the system to see what the root
problem is and I found that the spacers provided with the kit, both the
steel ones delivered with the kit initially and the aluminum ones sent
out as a fix do not interface with the bearing properly. This is due to
two issues.

The first is that the mating surface on the bearing for the spacer is
curved. I contacted Timken Bearing and they sent me the dimensioned
cross section of that bearing which showed that the curved mating
surface was a compound curve that melded two radii. This is not an easy
surface to mate to.

The second issue was that of the wall thickness of the aluminum spacers
set out by Van's to replace the initial steel ones. The wall thickness
of these aluminum spacers is .250in. The mating surface of the bearing
is approx. .187in. This is the steel contact area inside of the rubber
bearing seal. This meant that the spacer was pre-loading on the rubber
bearing seal instead of the steel portion of the bearing. In many cases
this has resulted in the loss of the pre-load as the rubber
deteriorates. Consequently, there were bearings spinning, yokes being
gouged and loose wheels which add to bearing wear and shimmy.

I initially thought that I would take the same approach as Ross Farnham
and machine profiles on the end of new steel spacers so that the
interface between them and the bearing was close to identical. I called
Ross and talked it over with him and he said that if he had more time to
put into it he would have made one of the spacers adjustable. I asked
him if I could run with that and he agreed it would be the best fix.

So, what I have been able to design is a system where there is a perfect
interface between the spacers and the bearings by utilizing the Timken
specifications and the accuracy of CNC machining. I have also been able
to design a robust and accurate adjustment mechanism into one of the
spacers so that the pre-load can be adjusted without having to take the
wheel apart.

Integrated into the spacer design are notches that accept the heads of
10-24 socket-head cap screws installed on the inner face of the yoke.
These restrict the spacers from being able to spin on the axle. As well,
you will now be able to accurately torque the front wheel bolt because
it no longer has any relationship to the pre-load of the bearings.

The screw adjustment ring is locked in place by two 1/4-20 socket-head
cap screws that have drilled heads so they can be safety wired.

All of these new components including the hardware is made from
stainless steel for durability and corrosion resistance.

I just finished installing a set in my front wheel assembly and it goes
together and adjusts very easily. I will be offering these for sale
through Mike Lauritsen at Cleaveland Tools. The kits will include all
hardware instructions and the drill guide used to locate the
anti-rotation screws.

You can go to my Blog site and read about these and see pictures of the
RV-10 as well as the RV6/7/8/9 components. It is located at the
following address: http://www.kitaircraftmods.com

I feel as though I have now installed a permanent fix to this problem
and I hope that if you are interested in the kit I have put together you
will go and visit the Cleaveland Tools site. The first 10 production
kits of each variant will be available sometime in mid January but
please leave your name with them if you are interested so we can get a
handle on how many are going to be required.

Many thanks for reading this long post.

Dave Hertner
RV-10 Builder #10164

Effectus AeroProducts Inc.


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bhughes(at)qnsi.net
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PostPosted: Mon Dec 22, 2008 3:07 pm    Post subject: Front Wheel Axle Spacers - A Permanent Fix Reply with quote

David,

Looks like a good solution to the problem. I locked the spacers to the
fork with screws but I am unhappy with the fit between the seal and the
spacers. Please put me down for a set.

Bobby Hughes
40116

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