Wobbly Wheel

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Model T Ford Forum: Forum 2005: Wobbly Wheel
Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Thursday, March 13, 2008 - 01:40 am:

I have a wobbly rear wheel on my '23. The wheel is tight on the axle and the spokes are tight. It's up on jack stands and as you free turn the wheel the wobble is apparent. Any ideas? Do I need to take a hammer to it and "tap" it true? As always, thanks for your help.
Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Thursday, March 13, 2008 - 09:16 am:

Is the wheel actually wobbling or is it the tire not running true to the rim?

Also, be certain that your rear hub is properly seated on the axle taper. If the key slid up in the axle keyway as you installed the wheel, it would cause the hub to appear tight on the axle taper while it is, in fact, hanging up on the key.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Thursday, March 13, 2008 - 12:15 pm:

Jerry,
The tire seems to be running true on the rim. The entire wheel wobbles...I will pull it tonight and see if the key has slipped...hope thats the problem.
Thanks,Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick - (2) '26's - Bartow, FL on Thursday, March 13, 2008 - 12:31 pm:

The wheel should not turn on the tapered shaft. The wheel should fit tight enough on the tapered shaft that, a special wheel puller is required to remove it. With the wheel tight on the shaft, do the spokes appear to be an angle other than 90 degrees from the hub as you look at the wheel from the rear? If so, the hub should be loosened and the spokes repositioned, if they are not cracked at the hub and the hub tightened. If not, your bearing could be worn out or your shaft could be bent. Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Gould on Thursday, March 13, 2008 - 12:34 pm:

Could be a bent axel as well. Many if not most are bent a bit at the taper. Usually not enough to cause a real problem, but yours may be the exception. When you have the wheel off, check the run out with a dial indicator. My bet is you find run out. Whether that's the main issue or not is another question.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Thursday, March 13, 2008 - 02:12 pm:

What do you mean by wobble? If you set a straight egde by the wheel and rotate it what does the clearance vary?

It may or may not be a problem.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Thursday, March 13, 2008 - 04:53 pm:

Thanks guys. I will check these options this evening after work.
Jim- The wheel does not turn freely on the shaft, the key is firmly in place. I just ran by the house and it looks like it might be a tad off angle. Hope it's the key pushed too far up the race.
Richard- Hope it's not bent...that would be awful.
Ted- The height of the wobble .5 to one inch.
I'll report later tonight, Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Seager on Thursday, March 13, 2008 - 08:46 pm:

How much run out at the wheel is acceptable? Can you place shims under the wheel attach point on demountable rims to correct run-out safely? Mike


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Thursday, March 13, 2008 - 10:15 pm:

O.K. I pulled the wheel and turned the opposite wheel and it looks like the axle shaft is ever so slightly bent. The wheel doesn't wobble wildly but it is noticeable. It looks like major surgery to replace the shaft...any tips?
Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Friday, March 14, 2008 - 01:11 am:

Would it be safe driving with a little wobble? Could the problem be caused by a bad bearing? I just can't see how a hardened steel axle could get bent. Just grasping.
Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick - (2) '26's - Bartow, FL on Friday, March 14, 2008 - 08:33 am:

Yes, you will have to dismantle your differential to remove the shaft. Once done, I would take it to a reputable machine shop specializing in auto repair / engine rebuilding and ask the master machinist if he can straighten it by means of a multi-ton press. If he can't, you will need to replace the shaft. An obvious wobble, as you describe, puts a lot of stress on the wooden spokes of the wheel, which are designed to provide vertical, not diagonal, strength to the wheel. Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Friday, March 14, 2008 - 09:47 am:

Bob,

Most Model T wheels wobble to some extent, it's not a big deal. The stesses that wobbling place on the spokes are nothing compared to cornering.

Jim, if the spokes are only meant to provide "vertical strength" we better never park our cars on a hillside.

If the total wobble is less than 3/8" I wouldn't worry about it a bit. The only annoying thing about a wheel wobble is that every 5 miles someone will pull along side you and tell you your wheel is wobbling and did you know about it.

Again, unless it's extreme, don't worry about it.

That said, whether your axle is bent slightly or not, always inspect for cracks or imperfections that will lead to cracks, e.g. galling, grooving, keyways stretched until a crack appears at the corner where it blends into the shaft, etc.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick - (2) '26's - Bartow, FL on Friday, March 14, 2008 - 10:25 am:

Jerry, Please give me a little more credit than that. Of course I don't mean we cannot park our cars on hills or turn a corner. I am saying that the stresses incurred by a spoked rear wheel with a bad wobble, going 30 or 40 miles an hour are not what the wheel was designed for. Think about it. It would be like bending a coat hanger back and forth, in the same direction, until it weakens and finally breaks. It will endure the stress at first, but as time goes by with the constant side to side stress, it will eventually weaken and fail.

If the wobble is on a front wheel and not all that bad, I would agree with you that the hickory (not oak) spokes should be able to handle it, because on a front wheel, which revolves on the spindle, the wheel wobble is random and not always on the same few spokes, but on a rear wheel, with the wheel secured to a revolving axle, the same spokes continuously get the stress as the wheel turns, so I would not tolerate any sort of wobble on a rear wheel. If it is bad enough to worry him and he can fix it, he should. Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Friday, March 14, 2008 - 12:24 pm:

Thanks for the advice. I think I'd be more comfortable replacing the axle. Wish I could video the thing to show y'all but I'm a still camera guy. I guess the up side is that this will be a great time to fully go over the rear end. Better safe than sorry.
Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Friday, March 14, 2008 - 12:38 pm:

"It will endure the stress at first, but as time goes by with the constant side to side stress, it will eventually weaken and fail. "

No, it won't.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Gould on Friday, March 14, 2008 - 01:34 pm:

Bob, how much run out do you see on the axel close to the thread? How much run out do you see at the rim of the wheel? As Jerry says, a little run out, say 1/2" at the wheel, honestly won't hurt a bit. They all have run out to some degree. Heck I drove a 17 touring many years with a whole lot more run out than that on the right rear wheel due to a bent axel. Except for grease leaks, I had no problems. If you decide to change out the axel, keep everything, I mean everything, in the same order and orientation when you put things back together. I have a large press if you can't find a way to remove the axel gear and reinstall it on a new axel.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick - (2) '26's - Bartow, FL on Friday, March 14, 2008 - 01:38 pm:

Okay Jerry. Have it your way. It's your life. As for me, my family and fellow members who ask for opinions, I would prefer to err on the side of caution and the laws of Physics and common sense, as opposed to advising them to take chances with something as crucial as a wooden spoked wheel, upon which everything else depends. I have read too many accounts of and seen too many pictures of shattered wheels on this site to agree with you that spoked wheels do not fail. Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Friday, March 14, 2008 - 02:01 pm:

Richard- Please define run out...is it the pitch back and forth of the wheel? There doesn't seem to be any grease leaking. I'm going to try to trailer it down to Gator's shop in the near future. He has offered to help with a few minor things. I will talk with him this weekend. I may take you up on the press offer-thank you.
Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Gould on Friday, March 14, 2008 - 02:27 pm:

Bob, yes, I meant the difference between the high and low points. When you turn the wheel, the total wobble or pitch back and forth


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Friday, March 14, 2008 - 02:36 pm:

O.K. Jim,

First, I never said spoked wheels do not fail. It's just rediculous to get that from what I wrote.

Second, you compared a wood wheel to a hanger wire. What has that got to do with physics? Even if our wheels were made of hanger wire, your premiss that a wobble causes a reverse bending is flawed.

Let's imagine that the wheel is REALLY wobbly. So much so that it sits at a 45 degree angle to the axle. Now, imagine two points on that wheel, 180 degrees apart, located at the extremes of runout. As the wheel begins to spin those two points will experience a centrifical force wanting to pull them radially, away from the axle. However, because our wheel is leaning over at 45 degrees, that centrifical force will cause a torque, or more correctly a moment, that will want to push each of our reference points laterally and in the direction of the wheel hub. In other words, the resulting forces will tend to correct the wobble, exactly in the same manner that a gyroscope returns to its nuetral position when external forces are eliminated. The wobble can't be corrected however due to our bent axle, (or whatever is causing the wobble), which maintains the wobble angle of 45 degrees.

So, what if anything, is reacting to the gyroscopic effects of the spinning, wobbly wheel. The answer is; it's the axle shaft. True, the spokes are communicating the forces to the hub and the axle so they are bearing an extra load. But, the load is CONSTANT, not fluctuating back and forth as in your analogy of bending a hanger wire. (By the way, the hanger wire eventually fails due to fatigue. I'm really not sure wood can fatigue. I'm fairly certain it undergoes elastic deformation up to its yield stress, which would be why we can't bend wooden spokes and have them stay bent. They will either return to their original state or fracture.)

Returning to our wobbly wheel. The example above assumed a wheel 45 degrees off from the axle, which of course is not what anyone would consider using, but was assumed simply to illustrate my point. In my previous post, I mentioned not being concerned about wobble of more than 3/8", total. Let's look at that. Assuming a wheel diameter of 30" means that the lateral forces acting to correct the wobble would be (.375/30) X Centrifical Force, or 1.25% of the centrifical force. Again, that's a constant force for any given speed, not a fluctuating force that would cause fatigue due to cyclic loading of reverse bending of the spokes or the axle.

I'm certain that a decent Model T wheel can take that small, additional load. Again, nothing like cornering loads which actually ARE a reverse bending situation as the point of applied force stays stationary, while the wheel continues to rotate.

There's the physics for you.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick - (2) '26's - Bartow, FL on Friday, March 14, 2008 - 03:43 pm:

Jerry. Agreed. It is no more rediculous for me to get that from your post than for you to get from my post that we should not park our Model T's on hills. Touche'

As for the Physics. I cannot site for you specific studies that demonstrate that wood will fatigue and eventually fail, but from personal experience, I am of the opinion that just like anything, no matter how strong or flexible, wood can and does fatigue.

You say that on a wobbling wheel, the load is CONSTANT and not fluctuating. On that, we agree. On a rear wheel where the wheel is fixed on a bent and turning axle there are specific spokes that recieve the full constant stress and other spokes that do not receive any stress. Looking at the bent axle from the rear, turn the axle until the bend is apparent and pointing down with the axle tip closest to the ground. A is at the top and B is at the bottom. Now mount the wheel. With the wheel mounted, A is angled outward and B is angle inward. Without much imagination, it is easy to see that the downward force of the weight of the car puts undo and excessive stress on the spokes that are at an angle and not vertical. As you spin the wheel and A is at the bottom, angled outward and B is at the top angled inward, with the same excessive downward force being applied to the outwardly angled spokes. When A and B are to the sides and horizontal, the vertical spokes that are 90 degrees from points A and B are straight up and down and receiving little stress, so there are two points on a wobbly rear wheel that get CONSTANT and continued stress, always at the same points and at the same angles. No matter what material something is made of, if it sustains the same forceful stress time after time, it will fail.

We must also take into consideration that, the wheels we are talking about are, in most cases, 80 to 100 years old and have seen their share of abuse over many decades of use and should be given the benefit of the doubt. Especially wheels that are spinning at 30 to 40 MPH, wherein other dynamics come into play. Better safe than sorry and in this case sorry usually means dead. Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick - (2) '26's - Bartow, FL on Friday, March 14, 2008 - 04:28 pm:

PS. Having thought about it a little more, while driving home from work, I must revise my arguement and say that the load does fluctuate as the wobbling rear wheel turns. As the A point outwardly angled spokes approach the bottom of the revolution where the most load is, the downward load is applied and immediately relieved. As the inwardly angled B point spokes come around to the bottom of the revolution, the downward load is, again applied and removed as the wheel revolves past the bottom point of most load. Repeat this rapidly as the wheel spins at 40 mph and you will see that there is alot of fluctuating flex going on in the spokes at points A and B, as the wheel revolves, which is not a good thing. Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Friday, March 14, 2008 - 04:47 pm:

Thanks Jim.

I see your point when considering the weight of the car as a loading force. In my example of a hypothetically extreme wobble, the weight of the car would indeed be an issue. I choose to ignore that factor because such an extreme wobble would never occur in actual use and because the point I was trying to make was to describe the forces acting on a spinning, wobbling wheel. You might say my expample was valid for a jacked up wheel.

In actual use, the wheel with slight runout would be affected by the vehicle weight just as minutely as it was affected by the gyroscopic forces. In other words, nearly nill.

I agree with you Jim; better safe than sorry is the best practice with wood wheels.

Thanks for your postings Jim.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick - (2) '26's - Bartow, FL on Friday, March 14, 2008 - 05:18 pm:

Thank you Jerry. There is nothing better than a healthy discussion that encourages both participants to think out their reasoning and learn from it, which is what your very valid arguement did for me and for that, I am grateful. Sincerely. Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Friday, March 14, 2008 - 05:45 pm:

Raise the rear axle off the ground and put on jack stands. Clamp a straight edge even with the bottom of the axle. Release the brake. Have your wife or child or neighbor slowly rotate the opposite wheel and see if there is noticeable eccentricity in the axle rotation.

I have, with mixed emotions, put washers bewteen the the rim clamp and the wheel to eliminate wobble. As best I remember the rim still pulled up tight against the flange on the wheel.

If the rear axle is "original" and still has babbitt thrust washers the real danger is they may disintegrate and let a tooth on the pinion chip off and leave you with no brakes. If you have Rocky Mountains or 26-27 large drum brakes in good condition then you can stop otherwise you have no way to stop the car. The small 8 inch drum brakes won't do it.

The rear axle can be overhauled in your garage, but I suggest finding a club member who can help you. Get the MTFCA rear axle repair manual. It will be $10 well spent and you can see what you are in for. Don't straighten the axle, replace it with a USA made part.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Friday, March 14, 2008 - 08:23 pm:

Thanks for everyone's input.I have really been snake bit with my rearend. First two flat tires, loose spokes on left rear (replaced wheel) now this one is wobbling and probably has been all along just didn't know. Now an axle...really hit the ground running in my new found hobbie. I'm up for the challenge...want to get this old gal mechanically sound enough to drive with conifendence. Thanks for your patience.The dialog is great...two sides to every issue.Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Friday, March 14, 2008 - 08:52 pm:

If your axle is slightly bent it will cause much more run out at the rim. Are you sure the axle is bent? If it is, you will need to replace the axle, which means completely disassembling the rear end. While you are at it, inspect all the parts and replace everything worn and make the adjustments according to the book on the rear axle. If you still have babbit washers be sure to replace them with bronze so you won't have the surprise of no brakes or stripping the gears. The washers are not expensive and well worth the cost and labor to install. I have rebuilt two ruckstells and it only requires simple tools. You don't need a machinist for most repairs.
Be sure the problem is not loose spokes or crooked spokes. I wouldn't replace the axle unless I were sure that was the problem. If the other side doesn't wobble, try the wheels on opposite sides. If the wobbly wheel is still on the same side, you have an axle problem. If it changes to the other side, your wheel is crooked. you can do this test with the keys out. Just tighten the nuts. This will make it easier to remove the wheels. Don't drive with the keys out.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mack Jeffrey Cole on Friday, March 14, 2008 - 08:57 pm:

Uh,would it be alot of trouble to switch wheels with the other side,and see if the wobble is the same? Sounds to me like that wheel needs chunking.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Friday, March 14, 2008 - 11:56 pm:

Just got back in, I'll swap the wheels but I think it's the axle.Report shortly. Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Saturday, March 15, 2008 - 01:10 am:

Good suggestion Mack. Switched the wheels-the suspect axle with the new wheel still wobbles slightly. The suspect wheel on the opposite axle wobbles more (not as bad as before on the suspect axle)...conclusion suspect axle is slightly out and suspect wheel is warped slightly. Solution??? The wheel is otherwise very sound.I feel a little better about this...what do y'all think. I'm going to try to post a cell phone video. Thanks all.Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Saturday, March 15, 2008 - 02:57 am:

This is a poor quality video of the "wobble". The left video is of the suspect wheel on a true running axle. The right video is of the true running wheel on the suspect axle. You be the judge. I may be over reacting...let me know.Hope the links work. As always,thanks.
Bob

http://www.youtube.com/watch?v=qZmRtq_LkVE

http://www.youtube.com/watch?v=5DyS-Z_QmMk


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Saturday, March 15, 2008 - 10:38 am:

I've followed T's on tours with wobbles like you have, and they seem to go on and on that way. If the spokes are tight and solid, you will probably be ok. If you don't like the appearance or don't want to chance it, looks like a lot of work to fix.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Saturday, March 15, 2008 - 12:03 pm:

Thanks Norm...didn't know what is acceptable wobble.
Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Saturday, March 15, 2008 - 12:05 pm:

Forgot to add: the wheels are very solid. Spokes are strong and tight.
Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Gould on Saturday, March 15, 2008 - 04:01 pm:

Bob, after viewing your videos I don't think you need to do a thing. Like I said earlier, most all have run out to some degree. Lets face it, after 80 plus years, all components are a bit out of alignment due to accidents, wear, etc. You probably drove the car for a long time without incident and only recently became aware of a condition that existed for years.
What is a guy to do, replace everything? If you were to opt for a better sitution, you would have to remove the hubs and machine the vertical surface perpendicular to the centerline of the axel hole, make sure the rim is true, replace the axel shafts, and probably sleeves and roller bearings. All for a true turning wheel? I don't think so.


Top of pagePrevious messageNext messageBottom of page Link to this message  By andy samuelson on Saturday, March 15, 2008 - 04:14 pm:

Take a good close look at the lugs on your rim.
If a lug gets just a slight bend or a little out of line it will look real bad at the outside of the tire. If your wobble is at or near a lug you can maybe shim between the wheel and the rim.
Another thing to look at is run the wheel without any tire and rim and see if the wheel has the same wobble. Also your tire could be seated a little off on the rim. I have had Firestones do this, I let the air out and bounce the tire all around and then blow up again. Watch how tire seats on the rim. All this could be the tire, you can measure and see if the tire is more on oneside than the other.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Saturday, March 15, 2008 - 04:53 pm:

Thanks fellas. I'm still learning whats acceptable and whats not. I'm glad to hear these wheels are o.k. to ride. Wish we had done the video earlier...think it was a big help. I'm going to experiment with the shims and see what results I can get. There are so many variables, y'all are right about the age and the different things that can contribute to this. I'll continue to piddle.
Thanks again,Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Denny on Saturday, March 15, 2008 - 05:05 pm:

Hey guys,

Dont forget that a wheel with wobble will also cause uneven tire wear.

Denny


Top of pagePrevious messageNext messageBottom of page Link to this message  By aaron on Sunday, March 16, 2008 - 03:12 pm:

If my rear wheels were that good I'd say one is running true and the other is even more true.

When I did front end alignments in the 60's they recomended changing any wheel that had more than 1/4" runout. And that was on 15" & 14" wheels.
As to the tire wear caused by that little amount of runout,,...ya, driving the car alone without a rt. side passenger may also cause the tires to wear unevenly.
It's right up there with running without a radiator cap to help cut wind resistance!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce on Sunday, March 16, 2008 - 05:08 pm:

Doesn't look all that bad. Most T's I am behind on tours have that much wobble in all the wheels.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sanders on Sunday, March 16, 2008 - 10:01 pm:

Well I put the wheels back on and took her for a spin through the neighborhood ...putted along like a champ. I figure if they wobble a little it will entertain the folks behind me. Thanks all, Bob


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