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#1
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Re: pic: 176 Prototype 6WD Rev. 7
You could probably do away with several chassis members and still be tough enough for just about any game in the Bumper Era
![]() We have used T-slot extrusion (Bosch 20mm rather than 80/20 because we can get it at cost) for our frames since 2005 and they have served us well - only in 2010 with the vigors of bump crossing (and some weight problems resulting in fewer cross members than we would have liked) have we had any structural problems. We have learned a few things about these types of frames through the years: 1. Through-bolt wherever possible. At the very least, leave it as an option. Remember that a 3-way joint is impossible to through-bolt when it's in the middle of a frame member (like on the front of this design). 2. If your extrusion manufacturer offers multiple types of "corner cube" connectors, go with the beefiest one you can get. Direct impacts have shattered our corner cubes in the past. 3. If we are going to use T-slot connectors on a particular piece, we prefer to use slide-in (not drop-in) T-nuts for the strongest connection. To facilitate easier insertion, we often mill the T slot wider somewhere near an end to provide an insertion point. 4. Think long and hard about using the T-slots for holding your pillow blocks. While having a sliding axle makes tensioning a chain trivial, locking it down in place requires that you diligently tighten everything after EACH match. Using a cam bolt or turnbuckle to make sure your pillow blocks don't slide can be a good idea if you can figure out how to do it in a lightweight way (usually we just through-bolt and add idlers for tension if necessary). I can tell you that the design just as you have it will make for a rock-solid frame that will serve you well! Good job. |
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#2
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Re: pic: 176 Prototype 6WD Rev. 7
Also, another possibility if you want the weight of box tubing but not the challenge of finding a good welder: 8020 Quick Frame.
http://www.8020.net/Quick-Frame-1.asp |
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#3
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Re: pic: 176 Prototype 6WD Rev. 7
really nice job.
Like others have said probably a bit too beefy. Welding will save you a ton of weight just in fasteners. Instead of welding we use gussets, rivets, and good epoxy and haven't had a frame failure in the two years we have used this method. |
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#4
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Re: pic: 176 Prototype 6WD Rev. 7
Looks good.
Any reason the Gaming Adapter is so low in the Chassis? You might have some signal issues, though I'm no expert on the subject. |
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#5
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Re: pic: 176 Prototype 6WD Rev. 7
If we applied the previous years' rules regarding frame behind the bumper, the corners of this frame wouldn't pass inspection. The entire length of the bumpers must be supported with no gaps under those rules.
I'd also put a bearing into the plate with the live axle coming off of the super shifter. The 80/20 is great in that you will be able to make minor adjustments to keep the bearing perfectly aligned. Other than that I think it looks good for a preseason prototype. |
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#6
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Re: pic: 176 Prototype 6WD Rev. 7
Quote:
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#7
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Re: pic: 176 Prototype 6WD Rev. 7
If you do use the 80/20 inserts above be sure check them for tightness after every match and use Loctite. They tend to vibrate loose because they don't have the natural "lock washer" properties of things mounted on the sides of the extrusion. These little inserts are very strong and much lighter than L brackets and plates but they can be a pain if they become loose in a hard to access place.
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#8
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Re: pic: 176 Prototype 6WD Rev. 7
Thank you guys for all of the comments thus far!
This will be our first year building just about anything with 80/20, and to go straight to a frame with it is a little nerve-racking. All other robots we've ever built have been either box or angle aluminum, welded by one of our sponsors. Unfortunately, we don't know if we have that option yet, and that was the impetus for trying some CAD with 80/20. I appreciate the advice on tightening methods, because that's one of the key things we're worried about. Also, thank you guys for the mention of not needing as much support as we've added. I'm going to bring this info to our next meeting and we'll work accordingly. James |
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