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Balancing the Tyres


Peter008
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I have issue from time to time with tyres going our of balance. Have tried to stick weights on whilst spinning vertically held in a vice but the friction of the bearings are a little too great for the tyre to settle on a heavy spot.

 

Have tried bike shops and tyre shops for electronic balancing all to no avail. Best I got was a bike shop where they could get the rim on the machine but it would not work electronically due to the small circumference of the tyre.

 

What do others do for balance issues on the small Jab tyres?

 

 

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Had a go at that early on. Looked good in the hangar with stick on weights but when spinning at 40-50 kt vibration is really quite bad. On the rear a touch of the brake fixes the issue but the front becomes annoying more so than causing an issue. That is why we believed that the bearings were muffling the issue.

 

Next we were going to get a couple of bearings and spin them clean without grease but thought others may have better ideas.

 

Tyres are quite cheap but it still annoys me to throw them away at 50% wear. When spinning they are not out of round by much at all.

 

 

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Thanks TP. Your post came in while I was typing. As I note that was our next thought so will probably try it.

 

What about a static balance that was the norm before electronic balancers. The tyre was horizontal on a cone with a bubble to centre it. Do you think the diameter of the tyre would be too small to get it close to correct. It would be quite easy to turn up a cone to fit the old balancers to the Jab rim.

 

 

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Talk to an old tyre guy, but I think if you can get the bearings loose enough that the tyre will fall to the lowest point each time (mark with a piece of chalk) then you can experiment with weights on the opposite side of the diameter. As you get the weight closer of course the friction will beat you. You could also turn up a blank with a centre which is a slide fit into the bearings and each end turned down to a very small diameter, then sit that on two pieces of flat bar beveled to a very small edge (or buy two cheap hunting knives.)

 

 

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Are you sure you aren't bumping on flat spots causing the vibrations?

The reality is probably something like that. The heavy vehicles that we run shows that once a flat spot is there it never goes away. A bit of vibration in the air and the heavy spot falls to the bottom, land a few times and suddenly the there is a flat spot.

I'm not discounting the rims either as they are far from precision built, although very light. Interesting however, once a new tyre is fitted there is no vibration after take off until the tyre is down to say 75%, then at 50% wear it becomes very annoying. This morning, (great conditions by the way) I pulled the nose wheel off the ground very early so that it would not spin as long once airborne and therefore not annoy me as much. It seems to occur on all tyres but as I noted earlier a touch of brake once airborne sorts out the rear wheels.

 

I wonder if I refitted the spats it would make a difference....

 

 

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Do you have that goo in the tubes that seal punctures? If so, my experience is that we don't rotate the wheels long enough to distribute the goo.

 

I recently replaced the bearings in my 230 wheels, new ones were completely sealed both sides so different model number than j specify and the seals were metal not just rubber... Anyway they definitely are very free running, unlike the ones I replaced. Not hard to do and didn't cost heaps.

 

Andy

 

Yes mine is 19 registered.

 

 

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Most of the bearings are sealed and don't spin easily. Get yourself a piece of "bright shaft" the right length and run the wheel on the edge of two bits of angle iron filed nicely flat and fit the shaft in the bearings.. Have it level and check in both positions. (change sides to eliminate the possibility of a slope affecting it. I don't like the idea of weights that might come off . I would consider removing some rubber in preference. Balance the bare wheel first, and then with the tyre and tube. Nev

 

 

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Do you have that goo in the tubes that seal punctures? If so, my experience is that we don't rotate the wheels long enough to distribute the goo.

Some time ago I enquired about balancing with the material that is sold commercially. Supplier advised that it does not work on small wheels and may even be a detriment. On aircraft where the wheel does not spin all of the time he thought it may even be worse. He said that it is not recommended to use the puncture goo on any small wheels that spin fast. Wheelbarrow or small trolly may work OK.

 

I don't like the idea of weights that might come off . I would consider removing some rubber in preference. Balance the bare wheel first, and then with the tyre and tube. Nev

I have not had any issue with stick-on weights coming off in the past. Granted, the rim is rough cast so will have to be prepared well but I would think possible.

In the past I asked Jab and whilst they were knew of the issue and were sympathetic with it, really had no suggestion other than change the tyre. The chap I spoke with did not know if there was a balancing device they use at the factory for repairs. They did suggest rotation at service time may assist, depending on the take off's and landings. Tracking of the vehicle could be an issue as there is light scuffing on one wheel that is more than the opposite side.

 

 

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If a weight goes into your prop it will be noticed. I don't think those tyre goo's are legal on the road. I know how vulnerable tyres are to caltrop seeds. There is a wear and wear issue with wheel out of balance, and out of round. Many aircraft when sitting for a while will develop a "flat" due to hysteresis of the rubber compound that usually goes after a bit of taxiing, but it certainly shakes things. Nev

 

 

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Another issue could be alignment, made one of my "legs" wobble badly just on take off speed as weight was lifted and touchdown, felt just like balance problem

 

Theres a method to check it in manuals

 

 

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If the aircraft is off the ground and the bearings are not shot and you are getting a regular vibration which stops on the mains when you pull the brake on then almost certainly either the wheel or the tyre or a combination is out of balance. Facthunter's post #10 is the best so far.

 

With that setup you will be able to get a very fine balance. Start with the rims, and if they are in balance then you know it's not wheels or bearings and can focus on tyres.

 

 

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This may not be relevant to small aircraft tyres, but:-

 

I also play with vintage cars and had trouble balancing 30 X 3 1/2 tyres on a Model T Ford equivalent wheel. The Model T club in the states put me on to glass beads as used in steering wheels on trucks. I didn't believe that this would work, but bought a kit to try to prove the idea one way or another. The results were startling , to say the least. With the car on a hoist you can spin the front wheels and as they come up to speed the beads distribute themselves to the lightest spots and all vibrations disappear as you hear the beads stop rolling around. We drove this 1923 car to Canberra and return last October and had zero balance problems ( nearly 3500Km). I'm not sure about the small diameter of Jab wheels, but is anyone up to trying it? Google "balance beads" for more info.

 

 

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That is the material that I alluded to in post #11 BC. I am not sure that we could put it in the tube as I have only ever used that type of balance bead on 11R22.5 tubeless. The advice was to not do it on the smaller tyres. Your 30's are somewhat larger diameter I would think.

 

After a couple of enquiries today I think I am on to an old static balance frame that is no longer used. It may take a couple of weeks to get it and turn up a coupler for the rim to fit on centrally so I will post what the results are. Hopefully it will work but if not will go with the axle with clean grease free bearings on a couple of angle pieces or hanging from a vice.

 

Thanks for the thoughts one and all.

 

 

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That is the material that I alluded to in post #11 BC. I am not sure that we could put it in the tube as I have only ever used that type of balance bead on 11R22.5 tubeless. The advice was to not do it on the smaller tyres. Your 30's are somewhat larger diameter I would think.After a couple of enquiries today I think I am on to an old static balance frame that is no longer used. It may take a couple of weeks to get it and turn up a coupler for the rim to fit on centrally so I will post what the results are. Hopefully it will work but if not will go with the axle with clean grease free bearings on a couple of angle pieces or hanging from a vice.

 

Thanks for the thoughts one and all.

Peter just to clarify, is this a shudder type issue at about 150ft on takeoff?

 

 

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It is easily recognisable as a tyre balance issue as you can feel it getting less of a vibration as the tyre slows down. I am probably too busy getting annoyed at it at the time so not sure of the height but 150 would probably be correct.

 

The front does vibrate more than the rear I think, perhaps due to the nose wheel suspension of the Jab. Also the brake, as has been spoken about a few times shuts up the rear.

 

Just to be sure, you are referring to a vibration? At first I suspected that you were referring to an engine hiccup at somewhere between 200 & 500 ft that I have experienced. It would just cough, then keep going. A number of people suggested carb ice from the taxi run but it ended up being air swirling into the engine chambers. A modified goose (turkey) neck into the carby as suggested by Jab fixed the issue.

 

The tilting of the plane and spinning the front wheel should tell you as was suggested but bearings that have some resistance so only lightly out of balance may not how easily.

 

The tyres are relatively inexpensive so I would change the suspect one then fly as a test. If not the problem then use it again next time you need one.

 

 

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It is easily recognisable as a tyre balance issue as you can feel it getting less of a vibration as the tyre slows down. I am probably too busy getting annoyed at it at the time so not sure of the height but 150 would probably be correct.The front does vibrate more than the rear I think, perhaps due to the nose wheel suspension of the Jab. Also the brake, as has been spoken about a few times shuts up the rear.

 

Just to be sure, you are referring to a vibration? At first I suspected that you were referring to an engine hiccup at somewhere between 200 & 500 ft that I have experienced. It would just cough, then keep going. A number of people suggested carb ice from the taxi run but it ended up being air swirling into the engine chambers. A modified goose (turkey) neck into the carby as suggested by Jab fixed the issue.

 

The tilting of the plane and spinning the front wheel should tell you as was suggested but bearings that have some resistance so only lightly out of balance may not how easily.

 

The tyres are relatively inexpensive so I would change the suspect one then fly as a test. If not the problem then use it again next time you need one.

Peter not engine issue just a shudder as described. Agree tyre imbalance most probably the cause and will apply brake next tkof as suggested by everyone. Thanks for input

 

 

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Peter, if you use this method you can leave the grease in the bearings - the boss (A) takes the place of the axle and the wheel rotates with the spigots.

 

The smaller the spigots are and the sharper the knife edges are the more accurate the balance, and it will be a lot more accurate than spinning the wheel on a dry bearing.

 

Click on the diagramme.

 

Balancer.pdf

 

Balancer.pdf

 

Balancer.pdf

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Agreed - good idea TP. A nice sharp edge will have little friction and provided the uprights are level, it should be fine.

 

Thanks for the tip.

 

I also liked the comment on the other thread on the same issue, to balance it on the plane as it does not have to be perfect to remove most of the vibration.

 

 

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