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pic: Linear bearing rails: the Cheesy RAWC way
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Re: pic: Linear bearing rails: the Cheesy RAWC way
Pretty, but................... What keeps it from pulling apart vertically?
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Re: pic: Linear bearing rails: the Cheesy RAWC way
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Re: pic: Linear bearing rails: the Cheesy RAWC way
They had two of these mounted exactly as shown, but mirrored so that the inside rails could be connected via cross members. Then the outside rails were firmly mounted to the drive train frame and cross-braced at the top. It required exact spacing at the top and bottom to be smooth, and I will conjecture that the force that pushed/pulled it up had to be almost dead center as well. If you got to see their model up close, it was smooth as butter and very lightweight.
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Re: pic: Linear bearing rails: the Cheesy RAWC way
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From the CAD, I can see how it is restrained in two dimensions, but not the third. |
Re: pic: Linear bearing rails: the Cheesy RAWC way
Any time anyone uploads a photo to CD Media it auto-tags the photo with 'frc###' (or 'ftc###') where ### is the Team Number in the profile of the uploader.
Try searching 'frc254' and 'frc968'. |
Re: pic: Linear bearing rails: the Cheesy RAWC way
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Re: pic: Linear bearing rails: the Cheesy RAWC way
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Please upload what you have. We are always trying to improve our lifts. I would love to see some that worked better than ours. |
Re: pic: Linear bearing rails: the Cheesy RAWC way
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Re: pic: Linear bearing rails: the Cheesy RAWC way
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The outside is a plain 1x2 that makes a U frame, with the bottom being solidly attached to the robot base, and the top the open portion. The top is held at the correct width by a spanner that goes across the two beams. You can see this in pictures of our robot--it's the piece the pulley/flag holder/spring mounts to. The bearings then mount as you see here, top and bottom. The inside is a rectangle made of channel on the left and right sides, and 1"x2" on the tops and bottoms. it rides inside the bearings, as shown. |
Re: pic: Linear bearing rails: the Cheesy RAWC way
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I think this is a "Picture paints a thousand words" situation. |
Re: pic: Linear bearing rails: the Cheesy RAWC way
33 actually used some benchmarking off of 254 for our elevator this year. It was a really cool experiment in the importance of certain dimensional tolerances. While many dimension in this system can be reasonable, many have to be extremely precise. Too tight and the system will die a binding death. Too loose and it will beat itself to death.
Overall it was a very cool project, but tough on a mill without a digital readout. Definitely gave me additional respect for the POOFS craftsmanship. If you have never built an elevator it is definitely a good off season project to learn what is important. |
Re: pic: Linear bearing rails: the Cheesy RAWC way
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Cory, thanks for the pictures. They're a little fuzzy but they confirm what I finally realized. I'm glad that you mentioned you were using Teflon as a glide surface. In some situations it makes perfect sense, this being one of them. It is also much easier to manufacture a Teflon glide that fits properly then it is to manufacture a bearing mount without access to a decent mill. |
Re: pic: Linear bearing rails: the Cheesy RAWC way
Actually our glides (254) for 2007 where simply adhesive backed Teflon from McMaster, they where really easy to manufacture, we just cut them out with scissors. :)
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