RV-10 Axle Extension Replacement
1/18/2007 - 192 Flying Hours
Page updated 2/9/2007 after Completed
Recently on the 2 main forums,
we've seen threads about a couple people who have had their axle
extensions break at the AN4-6A bolt. The
extension holds the outer side of the wheel fairings on to the
axle, while the inner side is well supported by a backing plate on the
wheel area. I haven't had any problem with mine, with 190
hours of flying, but I've been mainly landing on pretty good condition
landing strips. Only landing a dozen or so times in grass.
The ones that broke were often used on grass or rougher
asphalt strips. Still, considering that there should be no
real downside to this modification other than cost, time, and effort,
it's probably a worthwhile thing for most builders. The time
lost to repairing the damage done to or from a broken wheel fairing can
The problem, in more detail: The stem lays against the large
flat washer, that protects the axle nut from rubbing by the stem.
With such a narrow base, and flats on that base, the shaft
can rock back and flex slightly, putting a large bending load on the
threaded area of the AN4-6A bolt.
The solution, in more detail: To fix this, you can use a
heavier bolt, but you can also eliminate the bending by using a stem
with a much wider base area, which is the common theme to the fixes
listed below. I'll comment more on the fix below.
This is the
original plans area for the construction of that stem
page 46-5 figure 2
Here is a drawing of the
replacement stem that I had made up for my plane.
1/20/2007 to remove previous .25" counterbore hole, and
lengthen overall length by 1/16" to eliminate need for large flat
washer under the fat end of the assembly, and added notation changes
for thread depth. Revised
to reduce thru hole to 3/16" on suggestion from the friend who made
them. Also changed minimum thread depth to 3/4" for both
I've been told that this
alternative design, slightly less smooth looking than my Rev. 1 Drawing
of the taper
save some work for the smaller machinists by allowing the use of
a bit on the lathe that could cut a 45 degree taper
It adds a little more thick area too, but that strength isn't
necessary...but it does allow the threaded hole inside more room from
the outer edge of the shaft to keep some wall thickness there.
1/31/2007: Labeling and moved #40 screw hole further from
Here are my completed parts. This was a one-off
me to the drawing above, by a friend. They look great to me.
of new extensions
Today, 1/28/07, I got the extensions
|It's easy to see when you
compare them the smaller thickness of the original part, that can lead
to flexing and stressing
the AN4 bolt that holds it together. The new part uses a
AN5-6A bolt and AN960-516 washer, and has the same overall length as
the original shaft plus the large flat washer between it and the axle
nut. I also installed MS24693C298 1" philips stainless
screws instead of the 3/4" originals, and used blue loctite, as I've
had them rotate out and almost come off before. You still
the washer that gets epoxied to the fairing.
|Looking at the photos you
can see the length was an exact fit. It turned out perfectly.
I also installed brand new
MS24665-292 (thin) and MS24665-362 (thick) cotter pins for both the
axle nut and to pin the extension to the drilled #40 hole in the AN5
bolt. Installation was perfect, and required about 1.5 hours
time including the removal of the wheel fairings which is the longest
part of the job.
up the parts for the cost-sharing group purchase
Well after only about a week from the cutoff
signup for the axle extension list...the one that I originally figured
maybe 10 or 20 people would get on, to have a cost-sharing small
production run of extensions made, I picked up my first load of 198
extensions. They're still working on the rest of them which
be only a couple more business days away. They're making a
of 336 parts, which will be the exact number required to satisfy the
current and final list.
Before I even got home, I had my slave labor working on
the boxes made. You can tell that the kids were working
diligently, but that ol' dog was looking pretty lazy. Shown
are some photos of the finished product, which looked fantastic, and my
first night's packing and shipping job. There are 194 parts
out today (2/9/07).
This is the part made for
Russ Daves. It is available for sale for those interested in
a turnkey product.
Here's is one of Russ's posts from the forum:
"Dr. Linnard Griffin has agreed to build additional Wheel Pant Spacer
Extension, like the ones he build for my RV-10 (See previous post and
pictures), for the price of $125.00 per set including shipping in the
It you decide to place an order send me an e-mail at dav1111 at
cox.net, and advise me as to the status of your build so that I can
have Dr. Griffin ship such spacers out to the builders who are closest
to being ready to fly. There are currently 13 other builders interested
in the spacers."
Here is another design
posted by Zack #40512 on the RV-10 Matronics List
info updated 2/2/07
(My Note: This option may be
perfect for a builder
who has not yet done the fairings, as it would be light, and strong.
For people who have fairings done though, and have glassed in
their outer washer already, it may be tougher to retrofit without a
little added work.)
Here is Zack's post:
" Here is another solution to the Axle Extenders for the
wheelpants on the RV10. Since the Vans supplied extenders are having
problems in the field, my brother Jim (who is an engineer) came up with
a solution. The pics below show his design. The axle extender rod is
hollow in the center. This setup is lighter, thats right, lighter in
weight than Van's nut and bolt on extender. It doesn't look like it in
the pics, but it is! And it's stronger too! The one piece billet axle
rod screws onto the axle. The Capture washer was machine to fit exactly
on the axle rod extender and is bonded onto the wheel pant just as Vans
has you do with his. The capture washer distributes the loads on the
wheelpant with this plug and socket design."
If you want a set, contact Dave Czachorowski at 302-437-6087
As for my design above, I posted
a follow-up post with these comments. Just thinking points if
you're considering it.
Also, a couple other things to consider:
had a couple replies on the length. The original was 3-5/16".
The length including the AN970 washer is
If you still want to use the washer, you'll have to grind the extension
down by 1/16".
#2. On the VAF site thread, some people
questioned using an AN5 bolt vs. an
AN4 bolt. Considering the improvement in
the part, I'm sure an AN4 would work, but I am doing it
AN5 just for added strength "just because". You probably
can't go wrong either way, but other than having to
order a proper length AN5, I can't see any reason why not
to just go that size. The ONLY thing I can thnk might
be an issue is in a drastic event, the AN4 might shear
before your wheel nut gets ripped off, whereas
the AN5 may crack your wheel nut off and you could lose
a tire. But you'd have to take a direct hit on
that extension before you'd have a big worry.
#3. As Dan Lloyd pointed out, you don't *need* to taper
this thing and make it cone
shaped. He used 1" material and just
made it straight. So it IS possible to do this very
cheap and easy. Those who know me know I didn't care
much about weight before, and that still holds true about
the couple ounces of extra aluminum. But, I figured the
tapered one would look pretty, and be a little lighter too.
(Not as light as the hollow one from yesterday though) Either
way, there should be plenty of strength in the new
part. Also, the taper on mine makes it an easier retrofit
on mine, because I have existing epoxy holding the
outer washer to the fairing, so I need to stay less than
the washer's OD or I may have to grind epoxy. So
for the DIY guy, you can go many routes with this part... none
of them really wrong, AFAIK.
Here's one more option done by an RV-10 builder "Niko".
When this part of the kit snuck up on him, he went a different
route and got some 3/4" diameter hex from McMaster Carr and used an AN6
bolt on them. While not as wide in the base the those above, it's
larger bolt is much stronger and the overall part is many times
stronger than the original. Another good option that would save
money over some of the other methods. Proving once again that if
you're skinning felines, you can use a variety of methods.
For those involved
in the group purchase who want to pay their share via paypal, send your
payment using this link here: