Setting Breakout Force on Nose Gear

[Jeff R]

Just wanted to confirm that the breakout force for the nose gear is set by measuring from the axel bolt hole at the far aft end of the fork. This means the nose wheel has to be removed to set the force.

Also, the instructions say to install a cotter pin after the force is set. I assume you are to drill through the threaded bottom part of the gear. However, it seems that other have to periodically readjust the breakout force. Does that necessitate drilling a new hold when doing so?

Finally, I have the Grove nose gear upgrade. My understanding is that the axel nut should only be lightly torqued, 10 ft-lbs, as with the standard wheel.

Thanks,
Jeff

[L.Adamson]

On my 6A, it was done with the wheel and pant installed. A bent wire hook that bent out both directions like a "tee" was placed in the wheel pant hole for the axle. And then a fish scale was attached with the small chain to the hook.

[jjconstant]

I hook the fish scale just above the axle, onto the lip of the wheel pant mounting bracket with the wheel pant off. I clean off the grease that has inevitably migrated between the belleville washers so they are clean when setting the 22lb pull. I simply go to the closest flat that still reveals the cotter pin hole. If it's in between I tighten it until I can see it. I've checked and it's only about a half pound difference tightening it one flat to reveal the hole. I am more comfortable going a bit tighter than spec rather than a bit looser.

All Best

Jeremy Constant

[Bob Axsom]

I think you are talking about two things here, the NLG axel in the fork and the castering NLG fork on the strut.

NLG axel tightening - I have the instructions for the axel tightening that was printed in an old RVator in the other computer with my annual condition inspection checklist. If you want it I will send it to you via e-mail. Let me know if you want it.

The breakout force setting - This is where you tighten the nut on the strut where it holds the NLG fork until it takes the required force applied to cause it to pivot on the strut. My book says 23 lbs. but I would consider that a minimum value. It says to apply the force at the center line of the wheel until it moves in a castering sideways direction. I made an adapter out of coat hanger wire and I hook it around the side of the fork just forward of the axel and connect it back to itself. Then I connect the fish scale to the adapter wire. I keep pulling sideways on the fork to see where it breaks out (pivots) and tighten the nut on the strut and repeat until it requires 23 lbs to pivot the fork on the strut. Now since the radius of the pull force is smaller that the callout the actual breakout force will be a little higher than nominal but that's OK as long as what you came up with was worked up to slowly (so it is not grossly over torqued). It does loosen up early and you do have to retorque it a few times before it settles in. But as has been said, once you reach the required breakout fource just continue in the tightening direction until the nut slots align with the original hole in the strut.

Bob Axsom

I'm sure there are errors in this and I will revise it when I wake up.

RA

[gasman]

Originally Posted by Jeff R

Finally, I have the Grove nose gear upgrade. My understanding is that the axle nut should only be lightly torqued, 10 ft-lbs, as with the standard wheel.

Thanks,
Jeff

I have never been a fan of torquing taper bearings. The Matco thing is a disaster!! Glad to see you are using Grove.
Before you torque to 10 ft-lbs, Give Grove a call...612-562-1268 and ask.

This is from their web site.........


Pre-Load Wheel Bearings — It is important that the axle nut be tightened properly. With the aircraft jacked up, rotate the wheel and tire while hand-tightening the axle nut until it is hand-tight. The wheel and tire should rotate freely with little or no drag. If not, loosen the axle nut just enough so that the wheel and tire are on the “edge” of rotating freely. Install a safety cotter pin through the axle nut and axle. Check to see that the installed cotter pin does not interfere with the valve stem, or any other part of the wheel and tire assembly...... GROVE. correction: this is instructions for the mains.

Walt is correct (two posts down) about how Grove sets up their nose wheel..... http://groveaircraft.com/rvnosewheelinstall.pdf

My 6A has a Cleveland nose wheel as did my Warrior and are set up in a different manner.

[pierre smith]

I don't like to use a hook to pull on the brackets for fear of either bending them or tearing the wheelpant.

Simply get a 3/8" drive socket and extension that fits the axle nut. Put it on and push with a vertically held bathroom scale.

Best,

[Walt]

The bearing pre-load for the Grove nose wheel is set buy adjusting (shortening) the length of the inner axel "shim" provided. Once you get that trimmed to the correct length (be careful, easy to take to much off) then the bolt gets torqued to standard specs for a 3/8" bolt.

The breakout force using the spring scale will get you to where you should know "about" how it should feel when correctly adjusted, use this as a minimum setting. Much better to have this a little tight than too loose.

[IowaRV9Dreamer]

I'm getting ready to set the nose gear breakout force. The manual simply says to adjust the nut for 14 ft-labs of breakout torque... Which apparently corresponds to 22 lbs of force at the axle nut.

My question is: are these values with the U-611 washers lubricated? It seems like they should be greased, and it also seems that lubrication on that interface might change the breakout force a lot. The instructions or plans don't say anything about grease.

I understand that many have had better luck with higher breakout forces, and also that the breakout force degrades quickly as the parts wear in, and readjustment will be required.

Thanks for any info,

[Walt]

Lightly grease the bevel washers then crank down on the nut, hard to set the break-out force too high but easy to set too low.