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#16
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Re: FRC Bearing Load Ratings (Climber Winch)
The idea of using 1/2" shaft to support a winch drum to lift over 100 lbs, sounds a bit crazy to me.
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#17
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Re: FRC Bearing Load Ratings (Climber Winch)
It's not that it's the optimal design, but it's a widely accessible design; some teams and some winch designs may not really work through a stronger method.
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#18
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Re: FRC Bearing Load Ratings (Climber Winch)
I totally understand....many folks seem to be rather focused in their conceptions of how robots are built.
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#19
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Re: FRC Bearing Load Ratings (Climber Winch)
Depending on which concept we opt for, we may well go with a larger diameter tube based design. One of our concepts calls for elements protruding multiple inches from the surface of the winch drum, so a smaller diameter helps reduce packaging concerns. Thus the desire to use a 1/2" hex shaft.
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#20
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Re: FRC Bearing Load Ratings (Climber Winch)
Slightly off-topic but does anyone have experience using 3D printed bushings? We want to 3D print a 5mm hex bushing to interface with REV Robotics' 5mm hex shaft[1], but we want to make sure the 3D printed bushing won't crack under load[3]. We are planning on printing a few and testing them by hand, but if anyone has any info on this, I would appreciate it.[4]
[1]http://www.revrobotics.com/rev-41-1349/[2] [2]I know they sell bushings for that purpose, but we don't want to have to wait for them to ship overseas. [3]To be clear, this is not the load of the climber. This is a small flap we are actuating with a REV Smart Robot Servo. The flap is only taking a few pounds of force total. [4]Both empirical and anecdotal information is welcome. If anyone has any ideas on how to lathe and mill that small of a hex bushing that would be welcome too. |
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#21
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Re: FRC Bearing Load Ratings (Climber Winch)
For a hole that size, I would just use a file to make a hex shaped hole in an aluminum bushing.
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#22
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Re: FRC Bearing Load Ratings (Climber Winch)
If you use 5mm hex stuff a lot it may be worth investing in a 5mm hex broach (McMaster has them). Some teams have ground their own broaches from old machine tooling for a lower-cost option. (Not that I have anything against filing, if you making just a few it's a great option)
To directly answer your question, I recall seeing a team last year with 3D-printed wheel hubs, so printed parts can be used in high-stress situations. Your success will depend on the printer, materials, and printing pattern, not simply that its 3D printed. You can also do fun things like soaking the part in epoxy to make it ~100% dense and thus stronger. |
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#23
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Re: FRC Bearing Load Ratings (Climber Winch)
Quote:
We did bend a shaft during prototyping when we tried lifting using one spool in the center of the base we were using (which was probably about 28" wide) with the shaft only being supported on the ends by bearings. Still no damage to the bearings, but the shaft was definitely shot. |
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#24
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Re: FRC Bearing Load Ratings (Climber Winch)
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#25
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Re: FRC Bearing Load Ratings (Climber Winch)
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This is coming from the person who was EXTREMELY skeptical and made sure we printed half a dozen extras. Like with a lot of things, YMMV. On the topic of climbers, this year 'Snow Problem designed one that used 4 1/2" hex bearings and a ~29" run of 1/2" 1018 steel hex shaft, with a bolt attached to a shaft collar serving as the "hook" for a loop. So far it has failed twice: once was the rope (turns out a random cord from a surplus store is NOT what you should be making your rope out of), and once from shearing the bolt, which was 1 1/2 or 2", 8-32 SHCS, alloy steel, and costs us about 10 cents and 10 minutes (if that) to replace. Last edited by cadandcookies : 16-01-2017 at 17:45. Reason: added info on 'Snow Problem' |
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#26
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Re: FRC Bearing Load Ratings (Climber Winch)
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