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Why does my wheel need Pb?


Roger Lee

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Hi Guys,

 

Let's swap a few topics on wheel balancing. There was a time when I didn't think those little wheels needed any balancing so long as I had the little red dot on the sidewall of a tire in the right place. BUUTTT now I know different. Now I am a firm believer that all tires should be balanced. It doesn't take long and stops any vibration. You say my wheels don't vibrate and they aren't balanced. They do vibrate you just can't feel it unless it gets bad then the whole plane can shake if it is bad.

So what to do.......

First when you change out a tire the stem of the tube should be aligned with the red dot on your tire sidewall if it has one. The 6.00 series tires do and the 4.00 series tires don't. These are supposed to be pre-balance tire positions, That's great for the tire, but doesn't take into consideration all the things that are mounted to the tire.

 

When you swap tires just put them on a static balancer and add a little Pb, a.k.a. lead. Here is a picture of a wheel balancer I use for not only wheels, but a prop static balance too. All you need to do is slide off the bearing end and cone. Slide the wheel on up to the other side cone and then push the cone back in place that you took off. Align the set screws on each cone so they are 180 degrees opposite from each other. (i.e. one at 12 o'clock and one at 6 o'clock) Then slide the bearing back on. These are very high quality bearings and are very sensitive. Set the ends of the balancer on the flat spot of the bearings on something taller than the wheel. ( i.e. two one gallon cans) The wheel will then turn and the heavy spot will seek the 6 o'clock position. You will also need some 1/4 oz. stick on weights. This takes about 3/4 oz. - 1.5 oz of weight. I use a piece of tape at first to stick these on the wheel to test my weight distribution. I put maybe 1/2 oz - 1 oz on one side at the 12 o'clock position and an 1/2 - 3/4 oz. on the other side of the wheel at 12 o’clock. I have been finding most wheels take about 1.5 oz. of Pb (lead) weight. Since the wheel is so small and the weight is close to the center it takes more weight to balance it than it might if the wheel were 2-4 times its diameter. Once you have the weight temporarily taped in place rotate the wheel to either the 3 o'clock or 9 o'clock position. If it stays put then you are good to go. If it still moves to a heavy spot at the 6 o' clock position then you may need to add a little more weight or take some off. The wheel when balanced should stay in whatever position you place it in. If you have the right amount of weight then take the wheel off the balancer. Mark where the weights go with a pencil and clean that spot 2-3 times with a lacquer thinner. I’m dead serious when I say clean, clean again and clean one more time. Then peel the back off the weight and stick it down. Get a wrench or something and press it down really, really well. Then do the other side where the other weights are. Now the wheel is ready to go back on. This really is a fairly quick easy process. The cost of this particular balancer is about $120.

 

 

 

 

 

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I hope this helps some.

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My Sky Arrow, with 500x5 mains, had a bit of a shudder right after takeoff.

 

I own a little portable balancing device called a "Beemer Balancer" I bought to balance motorcycle wheels. Last time I had the wheels off I checked them, and boy, were they out of balance.

 

Here's a little video of one wheel after balancing - you can get an idea how much weight was needed:

 

 

Anyway, shimmy gone!

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Roger and Eddie, good info on balancing. Regarding the balancer, I bought one from Harbor Freight tools which is similar to the balancer you use. As you know, the Matco aluminum wheels are balanced at the factory and run true due to them being lathe turned. I will check these out now that I have the Desser "monsters' installed on them next time the bearings require greasing. My front factory wheel gives me a shake at takeoff and I can't hit the brake to stop this so this will definitely be balanced next time it's off the plane.

 

Here's the Harbor Freight balancer

http://www.harborfre...tand-98488.html

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Roger, your balance looks like a sensitive piece of equipment and is compact so you can throw in your CT and take it with you for "house calls". The Harbor Freight balancer has two offset small wheels at each end that are on ball bearings and the 1/2" axle shaft runs in these at about a 10 to 1 ratio. I'll have to see how sensitive it is. I'm hoping that it will blance to 1/4 oz. of weight at the 2" or 3" radius of the wheels. If it isn't up to the task for the airplane, me or my buddies always have some trailer wheels or motorcycle wheels that need balancing.

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