It looks good, but I’m worried about cross-support when another bot hits this one on the side. Also, any details?
Okay I’ll bite.
That’s a lot of machining to make something that looks cool, but why spend the machine time and effort on it?
Looks good and all I’m just putting my pragmatic hat on and thinking about resource alllocation.
I suppose you already know that two of the wheels are missing :] Are you planing on using omnis in the front?
Secondly I’d be interested to know what kind of motors and transmissions you are using. Those look kind of like the Bosch drill motors that used to come in the kit. Your guess is as good as mine as to what parts we are getting in the kit next year, but I’d venture to guess that we won’t be seeing the Boschs again
I’m not sure I’d dismiss this design as requiring too much machining. It really depends on what kind of resources and experience Madtown has. If they have access to a water-jet cutter this shouldn’t be too hard to make.
I do think however, that some of the lightening patterns may be weakening the frame too much. When making a truss pattern like that its best if you leave a bit of a radius at each corner. Simply cutting right angles can lead to stress fractures at the joints.
Good job so far!
How are you going to maintain it? It looks like if something breaks, you are going to have to reach in through the bottom, and that isn’t going to be easy.
I was wondering the same thing, it might depend. Are the center wheels dropped?
I like how it says madtown on the top.
The Frame: It is two 4x4 1/8" 6061 Aluminum tubing CNC out for the lettering and pattern. Solidworks says it weighs about 25 pounds with the 4 gearboxes, 4 cims, 4 4x2 wheels and everything else minus the battery. I put it through a three hundred force test and it bends in the middle by a few inches and the front wants to really cave in. The sheet of aluminum can stand about 110-120 pounds of force without really caving in. The back is sheet of carbon fiber and it bolted in. The reason for this is the weight saving and the high impact strength. The reason for this frame is because it’s twenty pounds lighter with more stuff added on. Quick and easy assembly.
For the first question: Currently it is held together with a 1/8 CNC bottom sheet of 7075 aluminum. Depending on what we go with: forklift, 4 bar arm or telescopic arm. We will either put two 1x1 aluminum tubing across to support it or put a sheet in the front.
Question 2: The reason for all the machining is that we have started a summer program. Our Vp got a brand new 60,000 dollar CNC Machine. Also our engineers were leaning toward a new frame. Our two stage frame was industructable but really heavy and that affected the building of our hand.
Question 3: Yes were putting omni’s in the front, but i am having a real hard time making them. Does anyone have a link or the file for a 4 inch double set omni wheels? Thanks in advance. No they’re not bosh drill motor gearboxes, i wish they were. But they are the dewalt drill gearboxes, i forgot to put the color in. We also have access to a waterjet cutter now.
Question 4: Our new cart is designed to be able to work under the robot. We prefer to work under and this year at nationals we managed to pull the supershifters about 10 times. The only way to pull them was to go under. The supershifters were great but the cims and the roll pin kept giving us trouble in between rounds. This setup is better because there are square cut outs in the bottom that allows easy access for the wheels and chain.
Question 5: No the center wheel is not going to be dropped. We talked to the Kil-a-Bytes, 1024 and few other teams that used omni’s in the front and did not drop the center wheels and had way better turning. Our turning sucked this year but it helped our robots center of gravity out by a lot because it had that rocker affect.
Thanks Cd for the support and continue giving 1323 ideas to improve this frame.
Perhaps I am misunderstanding your test, but the results are throwing a flag for me. Assuming that was a simulated test, did you get the deflection by looking at the screen display or did it actually give you a number?
My bad, too much writing: I meant 150 pounds.
Personally I dont like the direct connection between the motor and trans to the wheels cause if you get hit hard enough you could bend the drive shaft coming off of the trans. Or am I just seeing it wrong and it’s chain/belt driven.
You should look for a stronger way to beef up that frame; especially running along the length of the robot. I would suggest making the ribs along the corners of the box extrusion have at least a .625 or .75 lip.
Also, what kind of CNC machine would this be produced on? If it’s just a regular milling machine, you’d honestly be staring at the machine for days to machine those side rails. I’ve seen even simple triangulation patterns take an hour.
A much better solution would be to reduce the number of pockets in half by using larger, triangular-shaped pockets. This would be harder, better, faster, stronger, and a lot easier to machine. (Time is money during the build season).
(Remember, a 150 pound force on a robot frame would be the equivalent of static loading if the robot were to push against a wall. During impacts, the force skyrockets in short bursts, which could easily exceed the 150 or 300 pound load test and bend your frame.)
Another consideration is that all of your cool designs on the machining will not be visible due to bumper.
If it was me I would simplify the trusses to a triangular pattern to speed up machining and make it stronger.
It is Chain driven and the machining for this proto will be done over summer as a CNC test and we will make another and i do need to strengthen it up a bit =)
Very, very true. If you have taken physics you can do some approximations (they won’t be very accurate) of the forces involved if two robots impact. Even though inaccurate, you’ll be able to see that some very high forces can be applied in impacts.
Our 2006 robot came back from Nationals and the 80/20 material was all bent up and the bot looked as if it had fallen off a roof top or something
The scale just doesn’t look right at all to me… If the sides are 4x4, those motors look much smaller than small CIMs
i got the drawing for the cims and the gearbox from a team at a regional, it is a dewalt setup.
I’m almost certian those aren’t CIMs you’re using. Try downloading the CIMs from the FIRST CAD Library and seeing how they compare…
I see you have learned much from Daft Punk
Hmmm… I am 100% sure that those aren’t CIMs w/ dewalt xrp gearboxes.
I don’t know for sure, but I think those might be older drill motors from the KOP a long time ago.
I would go with Hachiban’s recommendation and download from firstcadlibrary.
If you’re sure i’ll do it, do you know of anywhere to get the dewalt gearboxes and the cims and 4 inch double set omni’s. That would help me out a lot.