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#1
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Re: pic: Manually machinable one-speed gearbox
Would there be a problem if you ran the outer wheels slightly faster than the middle wheels?
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#2
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Re: pic: Manually machinable one-speed gearbox
One solution, if a drop center is really desired, is to cut a pocket on the bottom of the center of the tube for the middle sprocket. IMHO, that's kind of defeating the point of chain in then.
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#3
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Re: pic: Manually machinable one-speed gearbox
Quote:
What 118 currently does as far as I know is use all 17t sprockets and use smaller diameter wheels on the corner, causing their larger diameter wheels to have greater linear speeds than the outer wheels. Jack's idea is a possibility to fix that problem without having to implement a drop center. Last edited by String : 14-05-2015 at 19:01. Reason: Grammar |
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#4
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Re: pic: Manually machinable one-speed gearbox
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Your wheels are slipping in one way or another in any motion other than going straight anyway. The normal force is highest on the inner (larger diam) wheels as well. |
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#5
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Re: pic: Manually machinable one-speed gearbox
So what you are saying is that some one could run sprockets with 16t-17t-16t all on the same wheel size?
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#6
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Re: pic: Manually machinable one-speed gearbox
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The width of the vexpro sprockets can easily be solved by shaving them down a little. Beware of the 16t sprockets, however, as we found that the chain would grind on the bearings, as Mason pointed out earlier. All in all, 118 has it figured out. Their system is the easiest Texas Tube I've seen so far, no need to reinvent the wheel. |
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#7
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Re: pic: Manually machinable one-speed gearbox
To anyone who has run with "Texas Tube" in the past: How do you account for the stretching of the chain over the course of the season? There doesn't appear to be a lot of room for tensioners. Is this even a concern with the lengths of chain that are being used?
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#8
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Re: pic: Manually machinable one-speed gearbox
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#9
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Re: pic: Manually machinable one-speed gearbox
Alright, that's good to know! Now, since this is an awesome thread and I'm learning a lot from it, I'm going to ask another question.
Has anyone every thought about using timing belts instead of chain? Fitting it into a 2x1 box probably wouldn't be possible, but what about a 2x2 box. I'd imagine it would be even more of a "set it and forget it" scenario because a timing belt would be less likely to break than a chain. |
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#10
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Re: pic: Manually machinable one-speed gearbox
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#11
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Re: pic: Manually machinable one-speed gearbox
This season, 1477 used a Texas Tube style chassis. On a 4WD with all omni wheels, we used VexPro 16t #25 sprockets. We had tensioners on both our practice bot and our competition bot, and never used them on either robot. We had no issues with the 16t sprockets, and our chain runs were more than 200 links long. Game permitting, we will likely be running a Texas Tube style drive chassis again. Our experience with #25 chain in 2x1 tube has been outstanding thus far.
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http://www.chiefdelphi.com/forums/sh...ad.php?t=94701 Here is a picture of 2791 running timing belts inside tube extrusion. |
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#12
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Re: pic: Manually machinable one-speed gearbox
2791 has continued iterating on their belt-in-tube drive since then. Chris Picone would be the guy to talk to about that.
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#13
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Re: pic: Manually machinable one-speed gearbox
192 has also used belt in tube for the past three years. 15mm wide GT2 in 2x2 .125 wall. With our set up and access points it's incredibly fast to assemble and tear down even though you'll never need to.
It is possible to run 15mm wide belts in 2x1.5 but you'd have to bore out the pulleys around the bearings or move the bearings out. I wouldn't recommend 9mm belt in the DT unless you had a proper tensioning system like 971 and even then they have had issues breaking belts. |
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#14
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Re: pic: Manually machinable one-speed gearbox
How are your access points for belt in tube set up? How is it assembled?
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#15
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Re: pic: Manually machinable one-speed gearbox
Been running belt in a tube structure formed from sheet metal for the past three years with no issues. The sheet metal works great because we can start with a readily available belt/sprocket combo and size the tube accordingly, rather than the other way around. Access is achieved by opening up the entire side of the tube, which makes installation a lot easier than the through-the-end approach or small access pockets required by extrusion.
It is a fair bit larger than the texas tube approach, due to the increased sprocket diameter/width, and the need to add additional clearance for the rivets which hold the tube together, but it works well with our resources, and we like the insurance it provides. Last edited by Joe G. : 15-05-2015 at 01:57. |
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