6 wheel drive with chain tensioners and shifting

[Edoc'sil]

Ya, ideally I would use 5/16 or 1/4, but we don't have it and off season projects are on a shoestring budget. Dropping the plate to 1/4 would save me 3.2 lbs if I left it with as many holes in it as I do currently, but that would be to weak. Likely I could shave off 2 lbs by doing thinner material and triangular cutouts.

If 45 lbs is considered heavy the women of our shop are quite obese

[548swimmer]

Originally Posted by Edoc'sil

Ya, ideally I would use 5/16 or 1/4, but we don't have it and off season projects are on a shoestring budget. Dropping the plate to 1/4 would save me 3.2 lbs if I left it with as many holes in it as I do currently, but that would be to weak. Likely I could shave off 2 lbs by doing thinner material and triangular cutouts.

If 45 lbs is considered heavy the women of our shop are quite obese

Are you sure it would be too weak? I recommend running stress analysis on one side of the frame, using the wheels for your fixed constraints. Put 300lbf on the outer plate and see what happens.

Since this is for off season, go ahead and use what you have, I understand completely. We're currently working on an old bot using the IFI control system because its what we have around. As previously stated, switch the 80-20 out for 1"x1" with 1/16 wall square tubing. You can mount it to the sides with threaded inserts pressed into the tube. My team usually uses 1/8" thick wall and to mount things on to the tube we just use a bolt. I'm not sure how well 1/16" wall would hold up to this though. Again, I wouldn't be too concerned about implementing these suggestions if it's only a off season robot.

[Edoc'sil]

I did run it through a stress analysis already, it crumpled like a wet rag. ( I don't really know what I'm doing in the stress analysis, I will give the tutorials another shot tonight however) A large portion of the strength comes from the flexmation attached to the sides and I do not have the skill to run a compound system like that. I anyone else knows how I would be happy to post the cad files. They are for Inventor 2010.

With the flexmation tubing I will look into it, but flexmation is one of our primary sponsors, we build build most of our bot out of the stuff because they give us anything we need for free.

What do people shoot for for chassis weight? 30 to 40 lbs?

[Dale]

There are several sources for the 1" nylon inserts if you want to go that way. Mcmaster.com has them. We've been using the 80/20 Quickframe series and so far have never had a failure of an insert. http://www.8020.net/Quick-Frame-5.asp

These are designed to be used with their 1" aluminum box that have little groves inside to to hold in the inserts. We always drive in a sheet metal screw or 10-32 bolt just to make sure they don't come apart. The profiles are at http://www.8020.net/Quick-Frame-4.asp.

Compared to normal 80/20 extrusion it's more of a pain to work with but it's almost exactly half the weight.

[ttldomination]

Originally Posted by Edoc'sil

If 45 lbs is considered heavy the women of our shop are quite obese

Not one of the smartest things said on these forums, but if your frame weights 45 pounds, then I would recommend another route.

Most teams can pump out a frame at about 10-20 pounds.

[sdcantrell56]

Frame should easily be in the 10-20lb range. For a complete drivetrain 45lbs isn't great but its also not entirely horrible. You still have a decent amount of weight to play with. It really just depends on what you're going to add on the robot.

[Edoc'sil]

looks like our frame weighs 22 lbs and the gearboxes/motors/wheels weigh 23 lbs

I like the sound of these, I will suggest them to the other students.


With the women comment, that is just what we have always called our bots, mainly due to the fact that our whole design and fab team is male.... I can see how the comment could easily be misconstrued.


Thanks for all the input guys.

[548swimmer]

If you want me to, I'll run stress on the CAD. If you want, I'll also see what I can do to strengthen/lighten it.

[Edoc'sil]

Actually my mentor showed me how to run the side panels and their supports as a single part, which apparently is a good enough approximation. I will post the files though if anyone wants to look at them.

[548swimmer]

Originally Posted by Edoc'sil

Actually my mentor showed me how to run the side panels and their supports as a single part, which apparently is a good enough approximation. I will post the files though if anyone wants to look at them.

Only if you're up for it. I am interested in seeing the result file though.