pic: Madtown Robotics Future Frame Proto 1

[R.C.]

[cdm-description=photo]31588[/cdm-description]

[JesseK]

It looks good, but I'm worried about cross-support when another bot hits this one on the side. Also, any details?

[Peter Matteson]

Okay I'll bite.

Why?

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.

[=Martin=Taylor=]

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!

[EricH]

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.

[sgreco]

I suppose you already know that two of the wheels are missing :] Are you planing on using omnis in the front?

I was wondering the same thing, it might depend. Are the center wheels dropped?

I like how it says madtown on the top.

[R.C.]

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.

[kramarczyk]

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.
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?

[R.C.]

My bad, too much writing: I meant 150 pounds.

[DarkFlame145]

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.

[artdutra04]

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.)

[sdcantrell56]

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.

[R.C.]

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 =)

[AdamHeard]

(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.)


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.

[R.C.]

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

[AdamHeard]

The scale just doesn't look right at all to me..... If the sides are 4x4, those motors look much smaller than small CIMs

[R.C.]

i got the drawing for the cims and the gearbox from a team at a regional, it is a dewalt setup.

[=Martin=Taylor=]

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...

This would be harder, better, faster, stronger...

I see you have learned much from Daft Punk :cool:

[AdamHeard]

i got the drawing for the cims and the gearbox from a team at a regional, it is a dewalt setup.

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.

[R.C.]

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.

Thanks,
rc

[AdamHeard]

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.

Thanks,
rc

I don't know where to download a model of the dewalt xrp gearbox, but 418 has been posting a lot of screenshots of them; ask them for the model.

As for the cims, go to www.firstcadlibrary.com under the motors section.

For the 4" omni wheels, I don't know anyone who sells them. You may be able to look at the 6" ones on AndyMark.biz and try to design a 4" version that uses the same rollers. Then make a hub to bolt two together.

[=Martin=Taylor=]

For the 4" omni wheels, I don't know anyone who sells them. You may be able to look at the 6" ones on AndyMark.biz and try to design a 4" version that uses the same rollers. Then make a hub to bolt two together.

He's refering to the Kornylak wheels, which are assembled the same way as the larger AM ones.

I've never bothered to make a detailed model of them. No point really... But all the specs can be found here (http://www.omniwheel.com/transwheel/transwheel-specifications.htm).

[EricH]

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.
I'm with Adam on this. Those are 100% not CIMs, definitely not DeWalts either. They sure look like they could be the old drills, or maybe FPs. Odd mounting method, though it would make sense if you were going for cantilever (which you don't want here).

[R.C.]

For the wheels I meant http://www.omniwheel.com/cgi-bin/plugins/MivaEmpresas/miva?plugins/MivaMerchants/merchant.mvc+Screen=PROD&Store_Code=KCWD&Product_Code=FXA456&Category_Code=Transwheel4 I'll ask team 418, thanks.

[Madison]

A handful of things:


The motor, transmission and mount models are from http://www.teamdelta.com/products/prod5.htm

It is not a CIM and it is a different model Dewalt gearbox than the NBD whitepaper calls for, as I recall. I can't say if it'd accept similar modifications and work the same way.

There's no way that tubing deflected several inches under that load. It would surely deform or fail before achieving that sort of deflection.

I designed 4" omniwheels for our 2008 robot that used a combination of custom components and AndyMark products. I'll see what I can do about making drawings of the individual parts. It might be a fun exercise to learn to model things from drawings instead of just expecting that someone will give you a completed model.

[R.C.]

Your right, that is a delta gearbox. I thought it was a dewalt with a cim and custom mount.

Solidworks showed an animation with several inches of deflection

I don't have time to draw 4 inch omni's because currently i am the only one that can use solidworks. I have b-ball practice and currently under an internship in which i draw and create signs.

[Madison]

Your right, that is a delta gearbox. I thought it was a dewalt with a cim and custom mount.

Solidworks showed an animation with several inches of deflection

I don't have time to draw 4 inch omni's because currently i am the only one that can use solidworks. I have b-ball practice and currently under an internship in which i draw and create signs.

Any FEA visualization software in a CAD package will enormously exaggerate the deflection. Use the colors and scale in the corner of the screen to determine actual deflection; don't eyeball it.

I work full-time with Solidworks and mentor a team, am moving and am tired, so if you're too busy to model the parts, I'm probably too busy to make the drawings. ;)

[R.C.]

I am sorry you do that for a living, most people are nice enough to share cad drawings. I know i have. I will use the scale for an exact reading. I posted this frame just to get some suggestions and ways to improve. Thanks for views.

-rc

[Madison]

I am sorry you do that for a living, most people are nice enough to share cad drawings. I know i have. I will use the scale for an exact reading. I posted this frame just to get some suggestions and ways to improve. Thanks for views.

-rc

Forgive me if I misconstrued my meaning. I offered to provide drawings to you of our omniwheels for your reference, but you've indicated that you're too busy to bother rebuilding models from those drawings. If you're too busy to make use of what I offered, then I won't take time from my own busy schedule to make them available.

I offered help and you turned it down. No harm, no foul, as they say, but I'm a bit dumbfounded that, not only was it unappreciated, but that you're saying I'm not nice because I didn't offer more.

[R.C.]

My bad, i thought you were telling me make my own with no reference. Sorry, i totally misunderstood. If you could send me those drawings i would greatly appreciate them. rcthekid1323@gmail.com.

[Madison]

My bad, i thought you were telling me make my own with no reference. Sorry, i totally misunderstood. If you could send me those drawings i would greatly appreciate them. rcthekid1323@gmail.com.

No worries. :)

I don't have the models at work; I will finish the drawings up when I get home tonight and will upload them to CD.

[R.C.]

Thanks for help, really appreciated