Integrated WCD "Warp drive" chassis

[mman1506]

Originally Posted by thefro526

I designed a similar system (technical term/name for this style of drive is 'nested tube', see notes about WCD above) in 2011 when I was on 816 and it worked reasonably well, although servicing it was a complete pain - or at least when servicing anything out of the norm. Here are some pictures:

Frame: http://www.chiefdelphi.com/media/photos/36107

Completed Chassis: http://www.chiefdelphi.com/media/photos/36163

Some general specs:

Drop Center 6WD
6" AM Plaction Wheels, Roughtop Tread
AM Super Shifters, Standard Gearing
Direct Drive Center Wheel, #35 Chain to outer wheels.

That drive didn't have any method of tensioning* and we never had any issues with the chain tension through two regionals and the off season. The drive only ever had one major failure that I can remember - the tread on one of the wheels came off and lodged itself in between the wheel and the tube.... Other wise, aside from needing to swap out the roll pins in the Super Shifters for 4-40 screws (or the other way around, it's been a while) the drive was solid.

* The Chains were 'dead spaced' meaning that they were spaced on exact center to center distances. #35 chain is really easy to dead space as it's a bit more forgiving to misalignment and weird tensions, #25 is a little more difficult, primarily due the tighter tolerances on tension and misalignment. (341's drive this year has a total of 6 #25 chain spans that have been dead spaced, no issues yet *knock on wood*)

Another note on dead spacing in drive applications, I only recommend doing so if one of the wheels is direct driven from a transmission. If one wheel is direct driven and all other wheels are chain driven a lost chain shouldn't render the entire drive useless for the rest of the match.

wow, could you explain more about how to dead space the chain?

[CENTURION]

Originally Posted by mman1506

wow, could you explain more about how to dead space the chain?

You can use a calculator like this one to figure out exactly how far apart your sprockets should be to perfectly take up the slack in the chain.

[Gregor]

With a CNC Plasma, I would consider doing drivetrains similar to 610. They have very nifty flat plate drivetrains, and is probably much easier to access and service. They cut their's on a CNC router.

http://www.chiefdelphi.com/forums/sh...&highlight=610
http://www.chiefdelphi.com/forums/sh...&highlight=610

[CENTURION]

Originally Posted by Gregor

With a CNC Plasma, I would consider doing drivetrains similar to 610. They have very nifty flat plate drivetrains, and is probably much easier to access and service. They cut their's on a CNC router.

http://www.chiefdelphi.com/forums/sh...&highlight=610
http://www.chiefdelphi.com/forums/sh...&highlight=610

+1 on this. I really really really want to get a CNC router for 1306 so we can make stuff like this.

[mman1506]

Originally Posted by Gregor

With a CNC Plasma, I would consider doing drivetrains similar to 610. They have very nifty flat plate drivetrains, and is probably much easier to access and service. They cut their's on a CNC router.

http://www.chiefdelphi.com/forums/sh...&highlight=610
http://www.chiefdelphi.com/forums/sh...&highlight=610

I would but sheet metal is really expensive, I'm not sure if its just Canada but two 6061 6x37 .125 sheets would be double what the 3x3x37 .120 box tube costs. Plasma cut metal also takes a long time to finish and isn't as precise. Does anyone know how 610 hold's there sheetmetal in place on there router? I cant think of a way to do it without using wood as a relief material but it looks like there using something else in there pictures.

[CENTURION]

Originally Posted by mman1506

I would but sheet metal is really expensive, I'm not sure if its just Canada but two 6061 6x37 .125 sheets would be double what the 3x3x37 .120 box tube costs. Plasma cut metal also takes a long time to finish and isn't as precise. Does anyone know how 610 hold's there sheetmetal in place on there router? I cant think of a way to do it without using wood as a relief material but it looks like there using something else in there pictures.

Can you link to the photos of them cutting it?

A wood panel under the workpiece is one of the easiest ways to do it, plastic is a good substitute, but a bit more expensive. For accuracy, it's common to have the router face a small amount of material off of the top to true it to the spindle.

You can also get a vacuum table, but that is also more expensive.

[mman1506]

You can see it in one of the images of there pdf http://team610.com/wordpress/wp-cont...-Edition-4.pdf it's a small picture though. It looks like some sort of a vacuum table with plastic relief?

[CENTURION]

Not a vacuum table, those strap clamps are definitely doing the holding. I think they just have a sheet of plastic (the black part) as a backing.

[Gregor]

Originally Posted by mman1506

I would but sheet metal is really expensive, I'm not sure if its just Canada but two 6061 6x37 .125 sheets would be double what the 3x3x37 .120 box tube costs. Plasma cut metal also takes a long time to finish and isn't as precise. Does anyone know how 610 hold's there sheetmetal in place on there router? I cant think of a way to do it without using wood as a relief material but it looks like there using something else in there pictures.

The team I was on had a CNC router. We used a big piece of plywood and wood screws to hold the metal down.

At Metal Supermarkets a 6x37 sheet of 6061 0.125 would be $30, and a 6x37 sheet of 5052 would be $24. That is pretty cheap to me, considering you only need 4 sheets. Why 37", and what is your source?

[mman1506]

Originally Posted by Gregor

The team I was on had a CNC router. We used a big piece of plywood and wood screws to hold the metal down.

At Metal Supermarkets a 6x37 sheet of 6061 0.125 would be $30, and a 6x37 sheet of 5052 would be $24. That is pretty cheap to me, considering you only need 4 sheets. Why 37", and what is your source?

The more I think about it the more I want to build it that way.. Anyway It still doubles the metal cost. I'll see if I can get the funding, my teachers are picky. I'm building it off of 2011 size specs

[thefro526]

Originally Posted by mman1506

wow, could you explain more about how to dead space the chain?

Originally Posted by CENTURION

You can use a calculator like this one to figure out exactly how far apart your sprockets should be to perfectly take up the slack in the chain.

You can use a calculator like centurion posted, or if you're using two sprockets of equal Pitch Diameter/Tooth Count/Etc, just make sure that the center spacing between the two axles is divisible by the pitch and comes out to a whole number and you'll be good to go.

It's worth noting that the chain will wear in (stretch) after some use, so depending on how well your critical tolerances were held, this may or may not cause problems...

[Jeffy]

This makes me think of these

Way more heavy duty than is needed, but lots of good engineering and explanations for it on the website. Could be helpful.

[Teched3]

Originally Posted by mman1506

I'm working on a off-season drive train project for our team. It takes some cues from the WCD.

It's made from 3 X 3" .120" box tube and uses the VEX ball shifter with a modified 3 stage with 34:50 gearing. The rear VersaWheel is directly driven and then chained to the middle VersaWheel with two sprockets, This wheel is then chained to the 3rd.

The top of the chain runs inside the tube on and outside on the bottom chain for easy tensioning.

Has anyone done anything similar to this? Any comments?

Any particular reason you are extending the driven wheel hex shaft outside the frame?

[mman1506]

Originally Posted by Teched3

Any particular reason you are extending the driven wheel hex shaft outside the frame?

Well we are thinking of putting spikes on it to attack other robots

I'm just lazy, I'm redoing the cad so it can be built in a plate configuration and fixing up the references

[Mr. Lim]

Originally Posted by mman1506

I would but sheet metal is really expensive, I'm not sure if its just Canada but two 6061 6x37 .125 sheets would be double what the 3x3x37 .120 box tube costs. Plasma cut metal also takes a long time to finish and isn't as precise. Does anyone know how 610 hold's there sheetmetal in place on there router? I cant think of a way to do it without using wood as a relief material but it looks like there using something else in there pictures.

We use hold-down setup clamps, step blocks, studs and t-nuts. Similar to this set found on McMaster: http://www.mcmaster.com/#fixture-clamps/=mc62a5

The top of our router's table has t-slots running down the length.

In between the t-slots, the top surface has black Sintra strips glued to the surface. These came with our router, and we replace them around once a year. When we replace the strips, we face them down with the router to make sure the working surface is level.

Whenever we cut a part on the router, the cutter goes through the part, and barely scratches the surface of the Sintra strips beneath. This does leave scratch marks on the Sintra, but not enough to warrant replacing them more than once a year.

In hindsight, a vacuum hold-down table would've been a nice addition, but we've been able to do without. Cutting COMPLETELY THROUGH plate is easy. Cutting partially through thinner plate is an issue, because the middle section tends to lift off the surface of the table when clamped using the hardware above.