super rough draft
looky looky
http://i52.photobucket.com/albums/g12/c9ollie/take3iso.jpg
http://i52.photobucket.com/albums/g12/c9ollie/take3side.jpg
http://i52.photobucket.com/albums/g12/c9ollie/take3top.jpg
http://i52.photobucket.com/albums/g12/c9ollie/take3front.jpg
http://i52.photobucket.com/albums/g12/c9ollie/take3transmission.jpg
Very nice! Don’t forget to add some cross bracing to the vertical members. And always remember that rubber tread moving next to the motor will induce some static electricity.
How thick are those sideplates? I am almost they are currently not thick enough to be strong enough
Ditto. They look 1/32 to 1/16ish. Make em thicker. I’m not sure how thick but 1/4" is probably a safe bet.
-Vivek
Ditto. They look 1/32 to 1/16ish. Make em thicker. I’m not sure how thick but 1/4" is probably a safe bet.
-Vivek
they are a 1/10 anything more is shear over kill and more weight. we ran 1/10th side panels last year with zero issues. the illustration rendering style has a black outline on every edge so it makes them look super thin. this is just a revamp of our current transmissions so we know they are already tough as nails. also the wheel does not rub on the motor its just packaged in a way that it looks like it does. i will get a few more renderings to show it. the top ring is just our packaging goal. also pictured in these renderings is the lower support bearing. i didnt have time to model it in the first renderings.
btw this is for our crab drivetrain.
Is this what they call a swerve drive???
But hten what’s a crab drive???
I’m a little confused as to the difference
your not already planning on using a crab drive for the 09 year, are you?
It isn’t exactly in the modules. You could have both of those with the same modules and different turning gearing.
It’s the way it’s set up. Correct me if I’m wrong, but a swerve drive has two or more sets of modules and a crab drive only has one. (Or it’s the other way around.)
I’m going to say that 1/10 is too thin for stress points. What a lot of teams do is take 1/4 and put the holes in, then mill the rest of the plate out, leaving a border and a small area around each hole at original thickness to add strength. You really don’t want to make a mistake and go too thin; having the thin stuff fail mid-match will take your robot out of the match. No spare means you may be out of the competition.
If nothing else, do the stress analysis and post it so that we know that you know what you are doing. If that analysis (which should probably take into account getting hit by 3 robots simultaneously from the same side) shows that it won’t break, even under running conditions, then I’ll retract my statement that 1/10 is too thin. If it doesn’t, then we’ll help you redesign so that it won’t fail.
I’m not as concerned about the thin-ness as I am about the lack of connections between the two sides. You really ought to add some standoffs down near the wheel, or better yet, machine the whole module out of .125" thick boxed aluminum.
You could always use steel. That would certainly strengthen the connection points.
lol that looks like a disc brake in the wheel…or is it?
I think its a gear.
-Vivek
Yes, with the .1 thickness, some real serious cross support will need to be added for it to be strong enough. More than just some cross supports probably.
Imagine the stresses the module can take when it rapidly changes directions while the robot is moving full speed (and even worse takes a hit from another robot at the same time).
Swerve drive and crab are very similar and often the two terms are interchanged. Many years ago, some teams developed a type of drive that could steer all four wheels but had limited turning of the running gear. It allowed the robot to “swerve” around obstructions on the field. Crab drive allows the robot to move in any direction without needing to turn the robot. The steering gear has the ability in most cases to turn more than 180 degrees and sometimes continuously. The first robot I remember with crab was a Chief Delphi robot from around '97 or '98 and there was one steering motor and a chain that wrapped around all four steering modules.
i can assure you that 1/10 is as thick as it needs to be anymore more is just a waste of time and pocketing 1/4 plate is just waste of aluminum. we ran this exact setup last year with zero issues. the frame of our robot bent before these “PODs” did. also since this is a super rough draft and i havnt really got to making the spacers for it. there is more support in these PODs but im more concerned about the geartrain layout.
Ollie,
Don’t forget that a 140lb robot running at 12 ft./sec imparts a pretty big side load to your module and all the force will be transmitted to the frame through the ring and a small amount to the top bearing. You can’t keep your friction numbers unless all the tread is on the floor.
As you said earlier you used 1/10, was it for this type of swerve/crab setup or for a 6-wheel? As a mechanical engineer I would take the advice of fellow mech-heads and increase the width of your side plates, 1/8th is the smallest I would go with major cross bracing. Looking at your setup your main drive shaft is about 6" away from your main mounting point for those side plates, and that type of torque on 1/10" sheet won’t last long. Take a look at some of the more successful crab drives of the last couple years (i.e. 71, 111, 1625), and make your modules beffey to start and slowly cut away the fat as you improve the design.
i understand that. we ran this same setup last year with zero issues. we even ran it without the lower support bearing for our 2 regionals. we did break 2 of the top posts but that was because of faulty welds. we redid them in billet and they held more than ok. the lower bearing is there for secondary lateral support and is not our main means of lateral stabilization. yes the forces are so great but they are so instantaneous that even if it does make something bind it will do it for such a short period of time it would be insignificant. the module is designed to be 100% support by the top post. the lower bearing is there for redundancy. i just put it where it was because i was just to lazy to redo the side panels, but it will probably be located closer to or below the axle of the wheel
Lol crab drive is really awe some
I’m asking for a stress analysis. You probably won’t convince 99% of us without one. Just run it in the worst-case scenario that you can think of and post the results picture, or something like that. If you can show us that it won’t fail, more teams might wind up using .1" metal on their robots next year. We all win. If you don’t show one, there’s a good chance that the first time it breaks, someone will say, “I told you so” or “Why didn’t you use…” or “What were you thinking?”. We all lose. You’ve got the CAD files, so it should be pretty simple to run the analysis, and if you don’t know how, it’s a pretty good way to learn.