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March 09, 2018 2 Comments
Trick procedures are as important to your tool box as the individual tools. Please share them whenever possible. In that spirit, check these:
Proper dial indicator use
Indicators magnify movement and provide numbers to better judge trueness. However, your standard dial probe indicator is not made for rapidly moving surfaces. Even when an indicator is fitted with a bearing, the measure surface (rim brake track or edge) should only move slowly for two reasons:
1/ The probe is not designed for sideways force. Its accuracy is wrecked if the probe bushing wears.
2/ The probe return spring is as weak as possible. Consequently the probe can jump off the test surface with a tiny bump and vibrate with a pattern of roughness. To navigate a rapidly moving surface, the probe would need a strong spring and a dampening mechanism to maintain contact.
Spinning a wheel on a truing stand is normal when a light gap is used to watch trueness. A gently spun wheel can turn at 60 rpm. With a full sized wheel, this is 4800”/min, the same as a 1/4” drill at 6,000 rpm. This is not slow speed!
So, move your wheel at any speed for visual truing but turn it slowly with dial indicators. Don’t let your measuring instrument use cause machinists to cringe!
Builders deal directly with hub bearing play. Play interferes with truing, even when it’s too little to bother riders. In some hubs, play can be adjusted to zero for the build and then returned to the recommended amount for use. In most cases, however, it must be tolerated.
How to measure play? Axle play is magnified 10X at the rim but quantifying is delicate work. Hold the rim where a dial indicator is located. Give it a slight lateral force, left then right. The wheel is easy to flex so your finger force must be extremely light to reveal bearing play only.
What is reasonable? No single answer exists for all wheels. One number many experts would approve is 0.008” (0.2mm) at the rim (TIR—total indicated runout). Such a reading at the rim can be produced by less than 0.001” (0.02mm) movement at the axle. These numbers are at the very extreme of manufacturing tolerances for consumer products. More accuracy may be needed by NASA, but not us.
Heat Guns rock
A must around any shop is your standard 1500W heat gun. Like anything with voltage and heat, special care is important—flammables must be far away and good ventilation present. Some of my favorite uses:
1/ Removing adhesive vinyl stickers from nearly anything. Vinyl stickers lift off effortlessly with the right heat. Use less until you discover the perfect amount. Be careful not to damage your surface.
2/ Heating metal so stuck screws or bearings can be removed. Heat makes metal expand, each material with its own CTE (coefficient of thermal expansion). Aluminum expands much faster than steel. But even in steel-to-steel assemblies, a larger unit will expand faster than a smaller (like a stuck screw). Frozen nipples are a good example.
3/ Drying touchup paint, adhesives, spoke prep, rinsed chains, etc.
4/ Removing old sewup glue from metal rims. Heat then scrape or wipe with steel wool.
5/ Lubing old leather saddles. Apply a preservative cream or wax, heat the area and watch the saddle inhale the lube. Be sparing, it’s easy to make a crispy old saddle way too oily.
6/ Paint removal where the substrate can take the heat. This works on metal or wood. Paint softens before burning and can be scraped or wiped off.
7/ Applying shrink wrap. Handy shrink wrap is available is many colors and diameters, used extensively in electronics. Find ways to employ it on bikes—bar tape or cable end finishing, for example.
Got some other tricks? Wheel specific? Please share!
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