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Nick
Experienced Roboteer
Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW
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Have you been weighing the parts? That hub must weight several Kg and with all the other parts it looks like the bot would be over weight. If you drop the hub, you still need to keep it's function with the bearings and retaining the wheel on the axle. In the hub, notice that the bearings are Choices are:
Ball bearings: They are strong but heavy and they have a large OD i.e for a 1" shaft, they have about a 2.5" diameter. That means boring out a large hole in your pulley and making a large bearing block to go on the top of the wheel.
Needle roller bearings: As used by Glen, they have much smaller diameter and weigh far less than ball bearings. They have two problems; their outer shells are quite weak & need good support b) they don't take axial forces very well, so you will need to include a thrust bearing on either side of the hub. the bottom bearing should be a roller type, while the top one could be just a bronze disk as it won't be used much apart from during impacts. Needle bearings need to run on a smooth surface. For long life they should run on precision polished and hardened shafts, but for bots, just a machined smooth shaft will do.
Bronze bearings: even cheaper than needle roller bearings and about the same weight. They need to be lubricated regularly and need a polished shaft to run on. They can be as strong as roller bearings, but people have been noticing they have much higher friction. They also need thrust bearings.
What sort of axle are you planning to use? if its a smaller diameter solid shaft, I would think about ball bearings, if its 1" or larger, Bronze or needle bearings will keep the size & weight down. Personally, I would go for alarge diameter tube for the axle with needle rollers for bearings.
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Sat Jul 04, 2009 10:24 am |
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