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Old 06-21-2019, 09:02 AM
gfb gfb is offline
Join Date: Jul 2014
Location: Madison, WI
Posts: 611
Default Main Axle cotter pin no longer lines up

Just replaced tires and brake pads on my RV-9A / Beringer setup and noticed that if I torque the axle nut to 25 Nm as described in the Beringer instructions the cotter pin hole no longer lines up with the holes in the nut.

Is it ok to drill another hole? Some other solution?
RV-9A - started 01/2015, completed 07/19/2018
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Old 06-21-2019, 09:19 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,272

The short answer is yes. A second hole (but no more) spaced so you can do half a flat is fine.

Before you do that, try over torquing the nut a little, spinning the tire, then backing off the nut. This makes sure your bearings are really seated.

In most cases a second hole is not needed.

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Old 06-21-2019, 01:39 PM
Gusmax Gusmax is offline
Join Date: Jun 2014
Location: Sherwood Park, Alberta
Posts: 72

On the Boeings we torque the big nut to 550ftlbs while spinning the wheel just like Carl stated to seat bearings, then we back off the nut and then torque to 150ftlbs.
Phil Kite

F4 Raider project with RV-8 wings and tail
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Old 06-21-2019, 11:38 PM
gasman gasman is offline
Join Date: Mar 2007
Location: Sonoma County
Posts: 3,673

Originally Posted by gfb View Post
Just replaced tires and brake pads on my RV-9A / Beringer setup and noticed that if I torque the axle nut to 25 Nm as described in the Beringer instructions the cotter pin hole no longer lines up with the holes in the nut.

Is it ok to drill another hole? Some other solution?
Replacing tires and brake pads should not change the location of the wheel on the axle.

I would remove the wheel and re-inspect. You did not mention if the fit was short of, or beyond the hole.

Maybe you just crossed your nuts.........
VAF #897 Warren Moretti
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Old 06-22-2019, 02:24 AM
jliltd jliltd is offline
Join Date: Sep 2013
Location: Rancho San Lorenzo
Posts: 611

Drill the axle as a last resort. It is counterintuitive to go poking holes in airplane structure to accommodate a "safety" item. It's a forest for the trees or throwing the baby out with the bathwater sort of thing. You might be able to add a thin or thick washer under the nut (or combination) to change the hole lineup. Gasmax makes a good point about swapping nuts from each side's axle and see if there is a difference. And don't be afraid to over or under torque from the nominal specified value a bit for cotter pin alignment. I am not sure how Beringer might differ from Cleveland but is common to add or subtract up to one flat either side of the value to accommodate the cotter pin. There is a tolerance built in. Borrow another torque wrench and there may be enough tolerance difference to make it. And always consider contacting Beringer about this.

Last edited by jliltd : 06-22-2019 at 02:30 AM.
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Old 06-22-2019, 09:30 AM
wjb's Avatar
wjb wjb is offline
Join Date: Nov 2012
Location: Half Moon Bay, CA
Posts: 934

It seems to me that putting a shim washer in place to make up any gap would be far preferable and easier than drilling new holes in the axle. It comes in lots of different materials (18-8 SS is common), in thickness increments of 0.5 mil.

I did a bearing seating operation like described above, but it's hard to tell right now how loose/tight the bearings are until I get some taxi time. I was planning on shimming as needed; it's unlikely to be too tight in the end.
Bill Bencze
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Old 06-23-2019, 01:01 AM
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RV7A Flyer RV7A Flyer is offline
Join Date: Jul 2013
Location: US
Posts: 2,077

I had one that after a year or so was just a smidge amount of fiddling with it would allow it to line up such that it was tight enough, but not too tight (causing the wheel to not spin freely). I used a peelable shim that I think I got from McMaster and it has worked great. Only needed the thinnest of shims to get good rotation with the nut tightened appropriately, cotter pin alignment is now correct.

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Old 06-23-2019, 02:14 PM
Sue Sue is offline
Join Date: Nov 2012
Location: Ok
Posts: 91
Default Cotter pin

Donít make the mistake of backing the nut off
1/6 of a turn, all kinds of problems will pop up.
Like ......less wear, less friction, and the awful
ď.001 gap in the wheel assembly.
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Old 06-23-2019, 03:58 PM
Ted RV8 Ted RV8 is offline
Join Date: May 2007
Location: Northern CA
Posts: 425

Thinking the above post is a sarcastic one bit never can tell on message boards.

Guess I’m old school where you kept some play in the wheel bearings, at least tapered roller bearings. So tighten them to seat, then spin the wheel, then back of to allow free play and install cotter pin. Don’t forget to safety wire the wheel pant Bolt!

Can’t imagine torquing the wheel bearings. These aren’t Boeing’s!!
Maybe Beringer uses ball bearings and if they have a preset spacer between the ball bearings then can see them recommending torquing them. If no spacer, that’s properly set up, can’t imagine torquing them either. Just going to preload a ball bearing that’s not designed and engineered for preload.

Also don’t see a problem with drilling new holes as long as you’ve checked everything to be sure it’s not another problem that’s causing the difference.

Again old school but don’t see the need for these different bearing systems on landing gear. With a good side load from a cross wind or botched landing tapered roller bearing is the best.

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Old 06-23-2019, 05:12 PM
Tom Martin Tom Martin is offline
Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,499

With Ted on this one, for the standard supplied parts from Van’s. After about 700 hours I drilled another hole. 400 hours later and no disasters.
Anyone have a few hundred hours using a shim? It also sounds practical
Tom Martin RV1 pilot 4.6hours!
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