POCKET WHEEL BALANCER
The Pocket Wheel Balancer
The Pocket Wheel Balancer - Revisited
K and R11 Rear Wheel Balancing
Simplified Pocket Wheel Balancer
Pocket Wheel Balancer - for dummies
The Pocket Wheel Balancer
Since the question on how to balance your wheels has come up yet once again, I dug out this write-up that I have been allowing to "season".
The cost was about US$20 total. Far less than the commercial units. It will balance wheels to within a few grams. If you have a monolever/shock suspended rear wheel you will need the adapter for an axle to bear on, and a 17 mm axle. But you will still be ahead of the game.
Per Rob Lentini, the BMW part number from the tool is: 36 3 613 CE 87
If you would like to have prepunched plates, and maybe bearings get back to me. I might be able to set up some type of kits for this.
Many years ago now, I wanted to balance my wheels. I also wanted the balancer to be portable. I came up with something that worked quite well a "Pocket Wheel Balancer" (PWB). I could carry this balancing rig on the bike. It worked fine at home, it worked for campground tire changes!
However, it did not work on my new K bike, the K axle was bigger. So, I recreated it, to work on a K bike. This was created, not designed. It was created so it "looked right". Checking for overload indications, it does not seem to have any. While the dimensions are given in English units, it can be built using metric components. With that introduction, here is how you to, can create a "Pocket Wheel Balancer".
First most balancing jigs are supported from the bottom. This means they have to be at least as long/high as the wheel diameter. This is not pocket size. So I created the PWB to be suspended or hung. This way the PWB only had to be big enough to surround the axle and hold some bearings. This was pocket size!!
Each side of the PWB has been built from a 1/8 inch plate (aluminum in my case) two bearings, two bolts, two nuts for the bolts, one screw with two nuts for it, possibly two washers, and a length of string to suspend it.
I sketched out what thought would work and then eyeballed what size outer diameter (OD) ball bearings I wanted, and since I had 1/4 inch diameter bolts handy, I wanted the bearing inner diameter (ID) to be that size.
I went to a bearing store and described what I wanted. The counter person asked for a bearing number. I didn't have a bearing number... Then I explained what I wanted the bearings were for, and showed him the sketch. I also mentioned that I wanted "economically priced" bearings. He went into the back and got four bearings. I bought them, built it, tested it, and used it for many years. The bearings were "shielded" by metal lips and I think this has been good. They have not accumulated grunge in the bearing races in their travels.
Again Anton Largidier assisted in this project. I got the plate, he cut and fabricated it and used bearings that fell readily to hand for him, and thus created a very similar PWB.
PWB plate. The plate I used was 1/8 inch panel aluminum. It could also be 1/8 inch steel, but then it would rust and should be painted. It could be thicker but then it would be bulkier. Also punching or making the large hole would be more difficult. We could detect no flex with this thickness. If it was thinner, it might flex, although that would probably cause no problems, you are on your own with a thinner plate.
__________ / * \ / | \ / | \ | | | | -O- | Height ~2-3/4 inches | | | Break points for angle ~2 inches | | | | -o-|-o- | ---------------- Width ~2-1/8 inch
The height and width are nominal dimensions. The "*" is a hole drilled for a 6-32, 8-32, 10-24, 10-32 screw. It is not critical, what ever you have. The capital "O" is the center of a 1-3/8 inch hole. It should be about 1-3/4 inches up from the bottom. The two small "o"s are the holes for the bearing mounting bolts. More on locating them later.
After you have the basic plate cut out, using a pointy object scribe a center line down the plate. The "*" hole will be on this. The center of the large "O" hole will also be on this. It will also be used for locating the bearing mounting holes.
The 6-32 etc. screw mounting hole is 1/4 to 5/32 inch below the top of the plate. It can be drilled for clearance, or tap size and the hole tapped.
The first PWB large hole was probably made with the largest hole punch I had and then filed to the final size. The "K" PWB large hole that Anton punched which was much easier. A 1-3/8 inch hole saw could also be used. If you are using a 1-3/8 inch drill bit use a drill press and ANCHOR the plate when you drill it. If it is not firmly anchored, when the drill cuts through the plate it will snatch the plate and make a heck of a mess. DO NOT HOLD IT WITH YOUR HAND!!! Making a 1-3/8 inch hole with out a punch, or a hole saw is a PITA. But it does not have to be pretty. Determine where the center of the hole should be. Get or make a 1-3/8 inch circle guide (A circle guide can be made using a compass and a piece of cardboard or plastic.) and align it on the center mark. Scribe the circle outline around or inside the guide. Drill a series of holes around the inside of the scribed circle. Use a scroll saw to cut between them. Use a large, quick cutting file to remove the bumps that are left. It does not have to be pretty, but the axle has to fit inside the hole.
My bearings were about a 7/8 inch OD with a 1/4 inch ID. Anton's bearings had a 13/16 inch OD, with a 3/8 inch ID. Bearings with slightly smaller ODs are probably better than those that are larger.
The bearings were positioned on a line perpendicular to the plate center line. I moved them in and out so that they projected into the large hole about 1/8 inch. Anton had his projecting about 3/32 inch to 1/8 inch. It can be less, but your hole ID has to be smoother, or you will be spending some time with a file. I tried to keep them as low as possible and at the same time, as close as possible together. Keeping them close allows you to use the PWB with smaller axles. We can use the K PWB with 17 mm R bike axles. It probably would not work with 14 mm R bike axles but one with smaller bearing ODs could be made just for them.
When you have the bearings positioned, mark the bearing ID on the plate with a pen, remove them, figure where the perpendicular line should be, scribe it, measure to the center of both bearings and take the average of the distance, mark this on the perpendicular, reposition the bearings centered on where you will be drilling, and make sure they will not hit each other, and they will overhang the large hole. (Measure many times, drill once.) Remove the bearings. Mark where you will be drilling with a center or indenting punch. Use a small drill like a 1/8 or 1/16 inch drill bit and drill a pilot hole, then follow it with the final size bit. This keeps the final drill bit from wandering around on the plate.
The centers, IDs, and ODs of all the holes and bearings can be marked on the plate before any metal is cut. This decreases the chances of dimensional errors. The bearings will project into the large hole. The axle can be use to see that the bearings will not lift it up to much so that it hits the top of the hole.
A construction suggestion. Get the bolts, bearings, and some cardboard, or even paper. Cut the paper to size of your intended plate. Mark where the "hanger" screw will go. Mark the large circle on the paper. Position the bearings where you think you want them. Mark where their OD projects into the large circle. Place the big end of the axle on the bearing projections and make sure it clears the top of the large hole. Measure everything from the center line.
It is much easier to remark the paper, or recut it than it is to file the metal plate!!! ;);)
So, now drill and cut all the holes and you have a holey plate.
Using a screw that is at least 1/2 inch long thread a nut well onto the screw. Put the screw through its mounting hole. Thread a nut on so that it is fully engaged, and then turn the other nut towards it, so the plate is trapped between the nuts. There should be about 1/8-3/32 of and inch of thread showing between the nut and the screw head.
Press the bearings on a flat surface by their inner races. If they turn, you will not need washers. If they rub, you will. Both PWBs used bolts with heads narrower than the bearing outer race, so we did not have drag there. Bolt the bearings to the plate and confirm they do not rub. I used Nylock nuts since they will not fall off by themselves. If you do not have or cannot obtain Nylock nuts, Loctite or Silicone rubber/caulk/seal will also keep the nuts you use from falling off. If the bearing outer races rub, find some washers with the right ID and an OD less than the bearing outer race and put them between the bearing and the plate. Check that the bearings project into the large hole. Check the big end of the axle will fit inside the large hole and does not rub anywhere. If it rubs on the edge of the large hole, enlarge it.
Find two lengths of string. Mine are about 4 feet long. It has to be at least about 2 feet long. It can be longer. It has to support the weight of the wheel so it should be stout. Tie the end of the string to the screw between the plate and the screw head. (One could cheat and just tie it though the hole, but the plate will tilt for sure and the axle run on the edges of the bearings. The screw provides an offset that keeps the forces and bearing centers in line.) Put a knot in the other end of the string.
Find something you can drive nails in that will hold the weight of the tire. I used the floor joists above me in the basement. Ceiling joists in the garage should work. Space two nails so the axle could rest on them with the tire between them. Drive two more nails outside of the first nails by about 2 to 4 inches.
Tie the ends of the string over the outer nails. Loop the string over the inner nails and give it a few wraps. Level up the PWBs by adding or removing wraps. (One should be slightly higher than the other since the axle is slightly smaller on one side.)
With the axle through the wheel bearings, lift the wheel up and shove the axle through the PWBs. Make sure the axle is fairly level and the wheel is not rubbing on the strings.
You are now ready to balance your wheel and find out how sensitive the balance is. Balance the wheel. (It should not rotate no matter where you put it. Make sure it is not rubbing the strings!!) Then add small amounts of weight perpendicular to the strings. I found my PWB would balance to approximately 1/16 of an ounce. Close enough for me.
When I was in a campground I slung the PWBs over a teeter-totter to hold the wheel up in the air as I got the balance set. This was after considering the swing set cross bar.
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Back in December 1997, I did a write up on how to construct a "Pocket Wheel Balancer" (PWB). It could be carried in the under seat tool area, and used virtually anywhere. That article can be found on the IBMWR Tech Pages at: http://www.ibmwr.org/otech/balancer.html (above).
Recently I took it from a hypothetical discussion for K bikes to reality. I built a PWB set for my K bike. Here is what I found and some parts information. First I found that I don't do machine design and fabrication for a living. With hand tools, the first one took me about 3 hours..., the second about an hour.
The PWB will work on all front wheels and dual sided swing arm rear wheels If you get the BMW balancing adapters, it will also work on rear single sided swing arm wheels. And it will also work on other brands. ;);)
Here is a short parts list.
The bearings I used were General Bearing Corp, 1603-ZZ bearings. They are metal sealed units to keep dirt out of the balls and races and to keep down corrosion. They are not soft sealed units since I think they would have more drag. The bearing OD is 0.875" (7/8") The ID is enough for a 1/4" bolt to pass. They were equivalent to what I used for the R bike PWB model.
A washer is needed to keep the bearing outer race from dragging on the plate. The bearing outer race "almost clears" but clearance cannot be depended on. Split type, "lock" washers OD are smaller than some flat washers and that is good to keep the shield from dragging on the washer.
I put the bearing bolt hole centers 1/2" above the plate bottom, and 1/2" from the plate center line. The axle clearance hole which was centered 1-3/8" from the plate bottom.
The bearing OD holds the axle away from the plate on the bottom, but not so high that the axle hits on the top of the axle opening. In use, the axle may not be completely perpendicular to the plate. (I get the axle close to horizontal, when I adjust the string length.) So some slop is needed in the hole size. I kept the bearings close to the center line so that it will work with smaller axles like on the R bikes (17mm)
I put the angle breaks 1/2" in from the outer edge and 2" up from the unit bottom.
The first unit, I cut the plate out of the aluminum sheet first. Not a good move, it is hard to hold onto the plate as you do other stuff. The second unit, I did all the marking and hole drilling/fabricating first and then cut the unit out of the plate. Much better.
I used a spring loaded center punch to locate and spot all the hole centers first. Then I used a circle guide to mark the edge of the 1-3/8" axle clearance hole. Since I had a 11/16" chassis hole punch, I again used the circle guide to locate where three 11/16" holes would hog out most of the 1-3/8" hole, and marked where to drill the holes for the chassis punch.
Using a hand electric drill, I drilled 1/16" pilot holes. Then in steps I drilled the rest of the holes to final size. (The hanging screw hole, the bolt holes, and the three holes for the chassis punch.) I used a chunk of 2 X 4 behind the plate to drill into. (This is much better than drilling into the table, or floor.) (I did not have a drill press.) When I left the unit as part of the larger plate it was much easier to hold onto the plate, than when I cut the plate to size first. ;);)
I deburred the hanging screw and bearing bolt hole sharp edges. I then used the chassis punch to hog out the axle opening. I don't have a formal work bench. So I C-clamped the vise to the deck railing and clamped the plate. A half round file cleared out the rest of the axle opening to size. This is where the earlier punch marks worked out well. I filed to where the punch marks were.
After all the holes were done, I cut the unit out of the larger plate. The top angle cuts were next. I don't like sharp edges, so the plate cut edges were filed to take off the high spots.
Finally I assembled the units, and checked the axle would fit through the axle opening, and not hit anything. If it did, I opened it up some.
I had some small ~2-3mm nylon cord around, I used to suspend the units from the floor joists. It appears to have sufficient strength. (The original units used cotton cord....)
Parts cost was about US$30.00
If anyone is interested in a kit of a preformed plate, fasteners and bearings let me know. We may be able to make some up and get some volume discounts.
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Balancing K and R11 rear wheels it is diffcult since there is no rear axle. If you are using a bubble type balancer the balancer itself will server as the axle. However, if you are using a bearing type balancer like the Pocket Wheel Balancer (explained above) you need something different.
The part number of the BMW tool useable for both the Ks and the R11 rear wheels is 88 88 6 363 613 and called a "Flange". The actual (CARTool GmbH) manufacturers part number is 36 3 613. This is what you will see stamped on the tool itself. This is the bit used for dynamic wheel balancing. (At least the shops that I have gone to that did dynamic balancing have.)
The tool is bolted onto the wheel using the stock lug bolts. Then you need a 17mm rod to go through the tool, and rest on the balancer bearings. I used an old /6/7 axle for this purpose. Worked fine, and it was cheap from Eurotech.
The BMW/CARTool is not cheap. It is pricey for a turned slug of steel. Around US$80 as I remember, but changing two tires yourself will pay for it in labor charges, or one tire including the lower mail order price.
So, make your decision.
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This is a static wheel balancer that costs about $10 and is built using readily-available parts -- primarily ABEC3 skateboard bearings.
Brian provides very thorough instructions - maybe too much, but read the article and you'll have a good idea of what you are trying to accomplish. My big simplification is to use skateboard bearings and standard handtools for construction.
If you don't have some laying around your garage, go to the local hardware store and get a short piece of the aluminum bar stock that is 2" wide, about an 1/8" thick and comes in standard lengths like 3' or 4' (you know the place - usually has various sizes of straight, angle, and channel stock in various sizes standing upright in slots at the end of an aisle). I got the three-foot length - it is enough to make 5 sets of balancers.
The center hole on skate board bearings is 8mm (or 5/16"). Get four bolts just long enough to go through the thickness of the plate, a bearing, an 8mm (or 5/16") flat washer and a 8mm (or 5/16") nylock nut (4 bolts, washers, and nuts total). You will also need two small bolts (I used 4mmX 20mm but 1/4"X 3/4" is fine) with a nut and nylock nut apiece and a few feet of sturdy nylon string or twine.
Cut two 3-1/2" - 4" lengths from your aluminum stock with a hacksaw. Scribe a center line all the way down the length of each (this is important!). Drill a 1-3/8" inch hole in the center of each plate with a hole saw (at least that's what I used; the aluminum is soft, so I just used an old hole saw I had for wood boring -- the trick is to stop every few seconds and clean the aluminum out of the saw's teeth). Once you've got the holes bored, clean up and smooth the edges with a small file, sandpaper, emory paper, whatever.
Now you need to mount your skateboard bearings. You want them side-by-side, perpendicular to the centerline with the tops of the bearings sticking up into the 1-3/8" hole far enough that your axle will rest on them and not the aluminum (in effect, you are making a rolling V-groove). Since skateboard bearings are 22mm in diameter, I found that putting the bearing centerline 6mm (.225") below the bottom edge of the 1-3/8" hole is about right (you can go a bit less, but not much). Just use a square to scribe a perpendicular line acoss the plate, 6mm below the hole. Since the bearing is 22mm in diameter, just measure out 11mm out each side from the scribed 'vertical' centerline on the newly-scribed 'horizontal' line, centerpunch the spots very carefully and drill your 8mm (or 5/16") holes. Go to the other ('top' )side of the plate and drill a 4mm (or 1/4") hole for your hanger bolt right on the vertical center line about half-way between the 1-3/8" hole and the top of the plate. Do the same for the other plate.
You now have 2 aluminum plates with 4 holes drilled in them and are ready for final assembly. Put two 8mm bolts through a plate, then two 8mm washers (thesse shim the bearings away from the plate, so try to make sure the washers are the same thickness), then two bearings, side-by-side, then snug everything in place using the 8mm nylock nuts. Turn the bearings and make sure they spin freely and do not rub - particularly on each other. Because of the way I laid out the holes, there is a good chance the bearings will just barely rub each other. To fix this, diassemble the unit and LIGHTLY file the 8mm holes just a pinch to allow the bolts to move away from each other JUST enough that the bearings do not rub. Once you have the bearings spaced properly and spinning freely, tighten them down firmly.
Now run a 4mm standard nut down a 4mm bolt and insert the bolt in the 4mm hole at the top of the plate, with the bolt head and nut on the bearing side of the plate. Thread your nylock 4mm nut onto the end of the bolt until the threads are flush with the end, then snug the standard nut down to the plate.
Tie about 8 feet of the nylon string to the 4mm bolt between the bolt head and standard nut. This puts the string directly over the bearings and allows the balancer plate to hang straight with the weight of the wheel and axle. Repeat the process with the other plate and you are ready to use the balancer.
In use, you just hang the two plates from any convenient overhead support. Brian's suggestion of four nails in the rafters is ideal, but I've hung mine from the handlebars of my moutain bike which is hanging from the ceiling of my garage, I used overhanging tree branches, a step-ladder, you-name-it. The trick is to space the plates about 8 inches apart and allow for easy up-and-down adjustment of the string length. I usually give the string a couple of wraps around the main support, then place the wheel\axle into the plates, then adjust the string length until the wheel is centered between the strings and hanging straight. At that point, wrap the free ends of the strings to hold everything in place and you are ready to balance the wheel.
I use the stick-on weights that you can buy at NAPA - they come in the form of a lead bar with regular marks - you just cut off the weight you need with a diagonal cutting pliers.
Note: For the true purist who has tapered wheel bearings, you should use 1/2"diameter, properly-machined custom spacers to slide onto your axles to allow snugging down the wheel's tapered roller bearings squarely to the axles. Snowbum describes these spacers on the Airheads.org website in his tech article on wheel bearings. In practice, I have found that you get quite acceptable results just sliding the axle through the wheel, as the bearings seems to 'hold their position' due to the tension of the standard spacers and seals, but you must be gentle as you slide the axle in and out so you don't knock the tapered bearing out of alignment.
I've got photos of the balancer to help with the understanding of the whole construction/use process I can send off-list.
Hugh Kenny, ABC 6051
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I found Brians instructions very confusing. All those bolts and washers? Cutting and hacking aluminum plate? I just couldn't figure it out. So after years of contemplation, I figured out how to build a simple pocket wheel balancer for dummies!
This is what you need.
2 small bearings that fit the axel 2 pieces of lumber 1x3x3.5 inches (size is not too critical) 4 wood screw eyelets a length a thin cable 2 cable clamps
I brought my axel to a bearing supply house, and found 2 small bearings that fit. ($10)
From the 1x3 inch x 6ft piece of lumber (83 cents at home depot), I cut off 2 pieces about 3.5 inches long.
I drilled a hole in each piece of wood to mount the bearing, which is 1.5/8 inches in diameter. It must fit loose or the bearing race will distort and bind the rollers. To prevent wood dust from getting into the bearing, I varnished the wood. At the same time I popped the bearings into place, effectively gluing them in.
I assumed it would be impossible for me cut and tie 2 pieces of string the same length. So I bought about 8 feet of thin cable and clamps from home depot. (Aprox $5).
I formed 2 small loops at each end of the cable and clamped them.
I purchased some eyelets, rated 25 lbs. They must be opened up a bit with some pliers so the cable can be slipped in. ($2)
I screwed 2 eyelets aproximately 1 foot apart into the 2x4 overhead supports of my garage storage area. (which spans the width of the garage, about ceiling height.)
I screwed an eyelet into each piece of wood.
To mount the wheel, slide one of the bearing assemblies onto the axel. Run the axel through the wheel, then slide on the other bearing assembly. Hook the cable over the overhead eyelets. Then lift the wheel and hook each looped end of the cable onto the eyelet of each bearing assembly. Tilt the wheel to slide the wire along the overhead eyelets until the wheel is perpendicular to the floor.
To store. Roll up the cable. Stuff bearing assemblies and cable into a sandwich baggie.
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