Main wheel preload

[RVG8tor]

I am wondering about a difference between Van's and Grove directions. Van's says to tighten the axle nut until there is not free play the drill for the cotter pin. Grove directions have you tighten while turning the wheel until you can't turn it any more then back off until just prior to "free wheel" my assumption is that is spinning with just a slight amount of drag.

I tried to tighten the Grove wheel (the one I have) according to the directions, but I can get it really tight, so much so I am worried if I go further I will strip the aluminum axle nut, but I can still turn the wheel.

I know what the Grove procedure is trying to do and that is seat the bearings on the races but tighten until the wheel does not move, that seems excessive. I am not sure what certified planes use for axle nuts but an aluminum nut on a steel thread would not be as strong as steel on steel.

So you guys with the Grove gear, did you tighten it up until the wheel will not move? Thanks for the help. I am trying to set the wheel on the bench so I can drill the cotter pin hole on the drill press.

Cheers

[David_Nelson]

Hi Mike,

I went down this path. I literally interpreted "rotate the wheel and tire while tightening the axle nut until it is so tight that you are unable to turn the wheel and tire. " so that's what I did. Common sense finally kicked in and I stopped doing what I was doing. Part of my todo list before moving the project to the hanger is so inspect the hub to make I didn't bend/distort it. I just inspected the left side and all looks good. <phew>

I think what Grove means is "... so tight that you are unable to turn the wheel and tire freely." This is supported by a couple sentences down when they say "Loosen the axle nut just enough so that the wheel and tire are on the ?edge? of rotating freely." I repeated this process a couple of times and called it good.

Grove could certainly improve their instructions. I doubt that many folks have a 1-1/2 socket or a crows-foot lying around so that a torque value could be specified. Perhaps something like:

"... so tight that you are unable to turn the wheel and tire freely. While turning the wheel and tire, tighten the axle nut an additional 1/4 turn. Finally, loosen the axle nut just enough so that the wheel and tire are on the ?edge? of rotating freely."

The "1/4 turn" is just a number I made up. It could just as well be something else and is only an example. I believe that he intent of seating of the bearings is performed, though.

Disclaimer: This is pure speculation on my part as I don't represent Grove in any fashion or manner.

[RVG8tor]

Dave,

Thanks for the info, I actually came to the same conclusion yesterday. I read up on these types of bearing and I also read the Cleveland manual I found on line. All of this told me what I already knew from my work on a trailer. Just snug it up, so that is what I did, I put a wrench on it to get it good an snug to seat things then backed off till I could just loosen it with my hand then tightened up with hand pressure only.

With this I get a good 3-4 revolutions out of the wheel with a good spin and no side loads. I put the gear legs on yesterday and will do the wheels today. I will take a look at the bearings and see if I messed anything up with the heavy tightening I did with the first one. The good thing is the bearings are cheap if they have to be replaced.

Cheers

[Transporter]

The Cleveland maintenance manual (AWBCMM0001-7; available online) provides some specific torque guidance:

"Torque axle nut using value specified in aircraft manual or the following:
1 Rotate the wheel/tire while tightening axle nut to 150 to 200 inch-pounds (16.9 to 22.6 Nm) to seat the bearing.
2 Back off axle nut to zero torque.
3 Tighten axle nut to 30-40 inch-pounds (3.4 to 4.5 Nm) while rotating wheel/tire.
4 Rotate axle nut (clockwise or counterclockwise) to nearest slot and cotter pin hole, and insert cotter pin. Bend ends of cotter pin around axle nut. Note: Wheel must rotate freely without perceptible play."

These torque settings worked well for my Clevelands...should be in the ballpark for Groves in terms of seating the bearings and final pre-load.

Good luck,
Mike

[RVG8tor]

I talked to Grove today and I did not mess up my bearings by really trying to stop wheel movement IAW the directions. The reason they have you do this is to make sure the bearings are not crooked in the race. The final setting is much like Van's; you snug to get the most smoothest wheel turn without side play.

I get a good 3-4 turns out of the wheel with a good spin, my nut is on hand tight but a snug hand tight. I might be able to go looser but the cotter hole pin is set now so I will shave the nut some if I need a looser fit or drill a new hole. I will wait to get some miles on them before I change anything.

Cheers

[DENMACRES]

TAPERED BEARINGS DO NOT LIKE VERY MUCH PRELOAD.

[terrye]

Originally Posted by DENMACRES

TAPERED BEARINGS DO NOT LIKE VERY MUCH PRELOAD.

Not only that, the rollers can damage the bearing races by tightening the nut too much. Yes, even brand new bearings!

[aerhed]

Man, you'd really have to vise them down to put dents in your bearing cups.
Of all the airplane wheel bearings I've seen destroyed, the number one culprits have been corrosion and dirt. Number 2 failure cause has been bearings too loose. I've seen only one failure from bearings too tight. That one actually melted the fork off a Navajo. Melted the ears right off it.