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Nosegear breakout force adjustment

A

avi8tor50

Well Known Member
Hi all-

Quick question about adjusting the nosegear breakout force. Building a 9A. I am assuming that one must drill hole in the nosegear axle for the cotter pin that goes thru the nosegear axle bolt. Similar to what is done on the mains-correct? If that is the case, what happens if you have to adjust the axle bolt just a a small amount and the openings in the nut no longer line up with the holes in the axle? I have read that many have to change the position of this nut once they start flying and continue to re-adjust the breakout force from time to time. Does everyone get away with one hole in the axle and if so do you make the hole across (parallel to the wings), front to back (parallel with the fuselage) or does it matter?

Thanks everyone.
Peter K
9A QB-Where is my engine????
 
Good questions.

Break Out Force: What I have found with tri-gears is that if the break out force is less than spec (or nose wheel shimmies) just tighten the big nut to the next hole and call it good. It may be up to 35 pounds break out without noticable side effects, but it will help stop the shimmy. The steering may be a tad stiff for a few hours, but it will loosen up again. Don't over use the brakes.

Axle Tension: This is a little more tricky as if the nut is tighened to the next hole it may be too tight for bearings. What I do is leave the nut in the same position and if the "donut" turns on the bearing then drill & tap a 10-32 screw into the front fork on both sides to keep the donuts from turning on the shaft.

Hope that helps.
 
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Peter:

You will find that the adjustment of the breakout force is not that fine tuned. You will be able to turn the retaining nut past where you feel you are happy with the breakout force to align the cotterpin holes without adversely affecting the function of the nosegear.

Regards,
 
Be sure to read RVator article

You should use what ever hardware is called out for you airplane. if you think you have to drill a cotter pin hole in a standard AN bolt some alarms should go off. The AN standard bolts are available with holes in the head and in the shank and if you needed one of them the drawing would callout the correct code letter for the hole in the shank. The nose gear installation is to be done as described it the recent RVator. I had not originally done mine that way but it was timely since I was doing my annual condition at that time so I did it right. I do not know what the breakout force is for an RV-9A but if you set yours too low you are in for a wild and shaky ride on landing. I set mine at 23 lbs on my RV-6A and that works fine. The initial hardware stack yields after a few hours and you will have to retighten nut to get your breakout force back to the correct level. After that it pretty well stabilizes but this year I did have to tighten it again during the annual when I found it had dropped off to around 15 lbs. This is not critical so when you have the correct breakout force if the nut is not aligned with the hole just tighten a fraction of a turn until the hole alignment is established.

Bob Axsom
 
breakout force

IIRC, the breakout force on the nose gear fork is adjusted with the big nut at the bottom of the gear leg fork, applying pressure to the cupped washers, to set and maintain a pulling force of appx 22 lbs at the axel to swivel the fork. You need to drill a hole for this castle nut thru the gear leg for a cotter pin. The axel bolt is not drilled for a cotter pin. Use a nylok nut as called for in plans, and torque to recommendation.(7 to 10 lbs) This leaves the wheel quite hard to rotate, but it will free up somewhat over time. :)
 
RV6A nose wheel break-out force?

I own, but did not build, an RV6A so as a non-builder, I have much to learn. Can someone provide a link to an article that explains the background on the topic of nose wheel break-out? I assume this is similar to a tailwheel breakout mechanism but for a nose wheel, I have just recently heard about it. Thanks, Tom
 
avi8tor50 said:
What happens if you have to adjust the axle bolt just a a small amount and the openings in the nut no longer line up with the holes in the axle? I have read that many have to change the position of this nut once they start flying and continue to re-adjust the breakout force from time to time. Does everyone get away with one hole in the axle and if so do you make the hole across (parallel to the wings), front to back (parallel with the fuselage) or does it matter?
Click to expand...

I'm not sure this applies to your specific nose gear situation but I read about this trick in the Slick mag overhaul manual for the gear nut...If the nut doesn't line up with the bolt hole to insert the cotter pin at the specific torque you remove the nut and run the bottom of the nut across some fine emory paper a few times. This will remove a few microns of material and polish allow the nut to move further on the bolt at the proper torque spec...do this until the holes line up.

From Slick Overhaul manual...
If cotter pin will not align with pin hole within the specified torque range, remove nut, lightly lap the bottom of the nut with emery cloth, and retorque drive nut to specified torque range.
Click to expand...
 
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avrojockey said:
I read about this trick in the Slick mag overhaul manual for the gear nut...If the nut doesn't line up with the bolt hole to insert the cotter pin at the specific torque you remove the nut and run the bottom of the nut across some fine emory paper a few times. This will remove a few microns of material and polish allow the nut to move further on the bolt at the proper torque spec...do this until the holes line up.
Click to expand...

I don?t think this is a good method as it removes some material from the nut and any surface treatment. Since the breakout force is a range and changes with time (requiring a periodic adjustment), adding a thin washer under the nut would be better if needed.

Bevan
 
I had one main gear axle nut that, over time, was either way too tight or just a bit loose when aligning the holes to get a cotter pin in. I found some peelable ply shim of the appropriate size at McMaster, and just a very small (1 or 2 layers) of that shim installed over the axle allowed for proper alignment and good, snug, but not too-tight fit of the nut.

I don't have the part number handy, but can look it up in my order history and get it for you if anyone would like it.
 
Bevan said:
I don?t think this is a good method as it removes some material from the nut and any surface treatment. Since the breakout force is a range and changes with time (requiring a periodic adjustment), adding a thin washer under the nut would be better if needed.

Bevan
Click to expand...

Makes sense...weird it's a technique in an FAA approved repair document.
 
Belleville Washer

Any idea where I can purchase a Belleville washer for my RV6A. I've tried to find one on VAN's site but have had no luck.
 
The part number and name: U-611 Disk Spring. You ca go to Van's site and search the store with the above part number. Price is $3.30 each
 
Bevan, I really appreciate you responding. Big help !! I did not build my RV6A and have had some shimmy ever since purchasing it 3 years ago. I've tried other things mentioned in the forum but not this; want to be prepared when I pull it apart. Thanks again. Tom
 
Belleville Washers

Thought I'd share with you what I found... I ordered 2 new B-washers from VANS just to have them available if needed. When I removed the nose wheel assembly, I found 2 washers already installed BUT they were both facing the same direction. Installed the 2 new ones as intended and my first (and only to date) was successful; no shimmy! Wonderful!
 
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