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pic: prototype drivetrain v2.1
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Re: pic: prototype drivetrain v2.1
Any comments?
Should the bushings be brass or nylon? |
Re: pic: prototype drivetrain v2.1
This drive design does not need suspension.
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Re: pic: prototype drivetrain v2.1
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Re: pic: prototype drivetrain v2.1
I am not sure if this is what you are trying to convey in your above image so if not consider this. Using your pivot shaft as a jack shaft will enable the chains to freely rotate and stay tensioned throughout the range of suspension. You can determine the center distances for chain runs with an even number of links and then do not require external tensioners. Here is even an calculator to do it for you. http://www.botlanta.org/converters/d.../sprocket.html
As for if this drive needs a suspension or not totally depends on your team and it's engineering decisions regarding the application for this drive. Keep thinking outside of the box it will serve you well in the future. ![]() Quote:
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Re: pic: prototype drivetrain v2.1
last year we did the same type of thing with our prototype, we had a delrin tube tensioned with a zip tie, the tubes 1/4 inch thick wall was completely destroyed by the chain in about 15 min, if you do that, you are going to need some large diameter nylon.
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The goal was to show how I intend to keep the chain under tension while it is pivoting. The nylon spacers are adjustable so that they can act as chain tensioners. When the carriage moves up and down, the tensioners will as well, theoretically keeping the chain under tension. If any one knows whether or not this will work, please let me know. The bushing question was in reference to the bushings on the carriage that are currently brass. I guess a better way to phrase it would be to ask whether brass or nylon has a lower coefficient of friction with aluminum. |
Re: pic: prototype drivetrain v2.1
The solid/plain surface bearings (which are different from bushings) that the suspension pivots on could be made from brass, with a ground steel shoulder bolt being used as a shaft, which would be very strong and durable. Better yet they could both be purchased parts. If the shaft is aluminum I would use a nylon or delrin bearing so that the bearing wears faster than the shaft.
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Re: pic: prototype drivetrain v2.1
Good deal. Look at 7075 or 2024 for the axle, with a good lathe you'll be able to get an excellent surface finish and great strength. I don't know if you have one, but a HSS reamer to do the inside of any polymer bearing is much much much easier/faster/idiot proof than boring it out.
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I'll figure that out at our next meeting, along with the answer :D. |
Re: pic: prototype drivetrain v2.1
Drill bits are great for clearing material out and for making holes where fasteners can pass through, but a drill bit will never come close to surface finish or precision of a reamer. Say you're making the bearing for a 1/2" axle, I would drill with a 0.4921 jobber bit then ream to 0.5010, a HSS reamer in that size is $21 from McMaster and has a tolerance of +/- 0.0003" an impractical tolerance for drilling or boring, but anyone can do it with a reamer.
Best of luck! |
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