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  #31   Spotlight this post!  
Unread 03-05-2011, 21:55
Trent B Trent B is offline
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Re: The Frame thread

Team 2502 uses mostly 80-20 to construct our robot, while the sentiment that T-slot is heavy is correct that doesn't make it a bad building material necessarily. Our robot this year ended up at about 110 pounds with an 8 foot lift



Also included on the robot were a pair of RS775's and about 15 feet of chain. Tslot can be doable at light weights, you just have to keep in mind it is very strong. I (150 lbs) have stood on a 4 or 5" piece of cantilevered tslot bolted in the end by an end fastener and 1/4-20 screw without causing any damage. I am not familiar with square tubing but I would expect it to have different results.

I would have no qualms with supporting my weight on any of the bars on that frame.
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  #32   Spotlight this post!  
Unread 03-05-2011, 22:11
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Re: The Frame thread

Quote:
Originally Posted by Trent B View Post
I am not familiar with square tubing but I would expect it to have different results.
I wouldn't. We picked up the entire 2009 robot on 2-3" cantilevers with abosolutely no visible flex. For the record: 1X1 1/8" wall 6061 Al.
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  #33   Spotlight this post!  
Unread 03-05-2011, 22:43
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Re: The Frame thread

We "discovered" a company ESTO that makes connectors that are primarily designed for trade show displays and such non-impact applications. Their connectors seem to hold up pretty well and make for some pretty quick prototyping and/or finished products.

Magically they seem help any project "new" students touch stay "square."
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Last edited by Phyrxes : 03-05-2011 at 23:02. Reason: Clarity
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Unread 03-05-2011, 22:48
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Re: The Frame thread

Quote:
Originally Posted by Jeffy View Post
I wouldn't. We picked up the entire 2009 robot on 2-3" cantilevers with abosolutely no visible flex. For the record: 1X1 1/8" wall 6061 Al.
I haven't played with stress analysis on square tubing for a long time so this may be correct. I was more trying to get at the fact that while T-slot is heavy it is also very strong and has its merits (such as linear bearings)
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Last edited by Trent B : 03-05-2011 at 22:56.
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Unread 04-05-2011, 02:25
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Re: The Frame thread

We've run into much the same problem over the years, except not with weight, but with delivery time.

Taking a quick look at your design, it does look very bloody strong, which is good, and heavy. One thing that my team is looking very long and hard at is building a chassis out of 1/4 inch Al plate that has been machined down. A preliminary image is posted immediately below... But what we plan to do is cut lightening groves in it--- projections put it at ~20 lbs, and it incorporates our Electronics, Gearboxes, and bumpers nicely:

As you can see, it's just 1/4 inch plate on the sides, front, back, and top. Sides hold together the actual Drive Train mechanisms and two internal bars that support the Kit Metal in the middle, the top allows for the side bumpers to be mounted, and the back and front plates allow for the front and back bumpers.

Last edited by 11douglash : 04-05-2011 at 02:28.
  #36   Spotlight this post!  
Unread 04-05-2011, 02:30
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Re: The Frame thread

the pic:
Attached Files
File Type: pdf DTpic.pdf (263.9 KB, 88 views)
  #37   Spotlight this post!  
Unread 04-05-2011, 02:37
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Re: The Frame thread

The chassis was 53 lbs with even more than what is seen there, I would estimate maybe 35 pounds for that including the linear bearings and all the hardware.
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Unread 04-05-2011, 22:14
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Re: The Frame thread

Here is Team 85's 2011 frame:



Some features:
-1/4" AL, bolt together construction
-Outer wheels articulate
-Very reliable, no issues all season long
-Requires significant lighting (not shown)
-Very stable even with the arm raised

Although the drive-train/frame was successful, we are opting for simpler designs in the future. We simply need more time to concentrate on the rest of the robot.
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Unread 05-05-2011, 00:08
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Re: The Frame thread

Quote:
Originally Posted by JesseK View Post
The major flaw I saw at champ's with design that Alex posted is with the side rails -- the ones that are supposed to back the bumpers.
We found an cool way around having to deal with welding that super structure. The bumper mounts are pictured below and were relatively easy to use, although next year we may update the design a bit.



That is our drive base from this year fresh from the welder. (You can see the welds aren't even ground down.) 3"x1.5" tubing that is 1/8" thick doesn't require bearing blocks, and internal belts are easy to change with the window above the center wheel. This DT is REALLY simple and it doesn't even require CNC milling (although it is nice). Virtually no maintenance was required and our 9mm wide belts held up fine for 2 regionals.



Above is a concept drive based on our "WCD" from this year. Custom 3" wheels only require a single 12:56 reduction in the gearbox to go 12 fps. (The 56 tooth gear is ~2.8" in diameter so there is little ground clearance, but it is right behind the wheel anyways. The tubing is also only 2"x1") It weighs somewhere in the low 30s with CIMs and w/o the shown arm superstructure. I'm working on getting a similar sheet version out soon. Basically this is a lighter and simpler version of our robot this year (which weighed a whopping 98 lbs.)

Feel free to contact me for any CAD.
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  #40   Spotlight this post!  
Unread 05-05-2011, 00:33
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Re: The Frame thread

I like how we're trying to save weight when we came in at 95 pounds. Continuous improvement!
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  #41   Spotlight this post!  
Unread 05-05-2011, 09:08
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Re: The Frame thread

816 experimented with a "Drive train in a tube" style frame this year, similar to Team 221 LLC's "Rockbox". Either side of the drive was put into a 4x4x1/8" Aluminum Tube, and the two tubes were welded to some 1x1x1/8" Cross tubes to make the frame. The Bare frame weighed 15lbs without any pocketing. If we were to have done some modest pocketing we probably could've pulled out a pound or two but we didn't see the need to.

Here's a picture of the frame with all drive components and electronics installed:



In retrospect, the frame was easy to build and plenty strong for a game with bumpers and moderately light weight. If you've got welding and some basic machining abilities, it's not a bad way to build a frame, though there are better options out there.
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