Free up JD R wheel from axle

deanvp

New User
On another forum we are having a discussion about how safe it is to use a sledge on the end of the axle to free up the wheel. There has been concern brought forward about damaging the wheel bearing/race. I have used this technique succfully on a JD 720 LP recently and was able to free up the wheel quite easily with a 20 lb plus sledge. One of the tapered sleeves was even broken by a PO making it even harder to remove. But a couple taps it came free. Now I know a wheel on an R is on splines but would not the same tapping on the end of the axle also break the rust bond? Once the rust bond is broken it should be able to be pulled off with a puller assuming the splines are not damaged or heavily rusted. The axle only has to move a 0.001 or so vs the wheel hub to break the bond. That slight movement should not damage a bearing or race. Your comments on this procedure would be appreciated.
 
Bought a parts JD 820 several years ago and needed to dismantle it. Had the fenders, seat, operator's platform and the powr-trol all removed, removed one rear wheel without any difficulty. The second was a real bear. Had to use 3 or 4 10T hydraulic jacks. Just kept adding jacks and finally with one propped against the end of the axle and a chain rigged over the end of the jack and secured to the wheel casting it popped loose. Must have worked on that thing for 3-4 hours. Never could figure out why one came off so easily and the other didn't want to budge.
 
I think there is a good chance of doing damage to the bearing. They weren't designed to be beat on. I had a real stubborn one on a JD-H. I made 3 tapered wedges and tapped them in the grooves of the hub, soaked them, cleaned up the axel, put a 5 ton jack on it and it came right off. I have since wrapped the axels with burlap held on with bailing wire, add some oil to the burlap and eliminated the problem of stuck hubs and rusted axels except for newly acquired rust buckets.
 
If you find any tractor manufacturer or bearing company who will condone beating on the end of a shaft or axle that is located axially by tapered roller or ball bearings, please let us know.

The instantaneous shock loads can be extremely high, sometimes high enough to cause brinelling (permanent indentations) of the contact surfaces of the bearing. And even if brinelling doesn't occur, the contact stresses are likely high enough to contribute to cumulative fatigue damage and result in reduced service life of the bearing. Despite those who claim they have pounded on innumerable axles and never had a problem, it doesn't mean damage wasn't done or bearing life reduced.

Here's a little high-school physics: lets say you have a 20-LB sledge hammer and you swing back and smack the end of your axle. And let's say the sledge hits the axle with a velocity of, say, 21.4 MPH which is 31.4 feet per second. (That's the velocity of the hammer head making one revolution per second at a five foot swing radius same as swinging your arm windmill-style, in one second.) The kinetic energy of that hammer is 306.5 ft-lb based on the relationship KE = *m*v*v.

Now, the theoretical average force required to stop that hammer in only 0.001 of stopping distance is 3,678,000 LB!! Does that mean that over 3 million pounds of force is imposed on the bearings? Of course not. A lot of the kinetic energy is dissipated in plastic deformation (dents and dings on both the axle and hammer head), elastic (spring-like) compression and rebound of the axle length and within the hammer head, as well as energy absorption by the mass of the wheel and/or hub, etc. But regardless, the bearings will still see a very significant impact.

Many years ago, one of my ME professors told about early failures of wheel bearings experienced by a certain auto manufacturer. They eventually traced the problem to the hard pounding the stationary bearings received while in shipment on some rail cars.

The point of all this is that if you value your axle bearings, you shouldn't pound on the axle.
 
This is the kind of post that I was looking for. However, I think one detail is being overlooked in your analysis. If I understand correctly your calculations assume the ball or tapered bearing is fully loaded against the surfaces. That is typically not true on an axle that has the wheel weight suspended. In fact it probably will be just the opposite and there probably will be a few thousands of play. Now if the axle moves less than that play or clearance when impacted but the wheel doesn't move then that very slight movement may break the rust bond and do no damage to the bearing.
 

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