Min Thickness for Countersunk Bolts

[JesseK]

Sorry Adam, I meant 254/1868. They had a box tube that ran down the side, above the wheel. We like that reinforcement, but don't want to risk warping of that box tubing.

Attached is what I could come up with in an hour. In hindsight, I could still put the sprockets wherever I wanted -- either in the box tubing or next to the wheel -- and maintain the constraints above.

The middle wheel isn't shown because it's dependent upon the attached gearbox. The gearbox would attach using a slightly modified wheel block (though still 2x1). I also didn't add in the 3/16" spacer to drop the center wheel.

Maybe more to come after the dog park.

[MrForbes]

That looks like it could be riveted relatively easily

[AdamHeard]

Originally Posted by JesseK

Sorry Adam, I meant 254/1868. They had a box tube that ran down the side, above the wheel. We like that reinforcement, but don't want to risk warping of that box tubing.

Attached is what I could come up with in an hour. In hindsight, I could still put the sprockets wherever I wanted -- either in the box tubing or next to the wheel -- and maintain the constraints above.

The middle wheel isn't shown because it's dependent upon the attached gearbox. The gearbox would attach using a slightly modified wheel block (though still 2x1). I also didn't add in the 3/16" spacer to drop the center wheel.

Maybe more to come after the dog park.

I know I probably sound like a desperate salesman now, but that frame looks like substantially more work than a proper west coast drive. A wcd doesn't NEED CNCing or anything fancy, 973 ran a very, very, very simple and reliable wcd for four consecutive seasons before my time.

I'm not tooting my own horn either, we've made some tweaks and optimizations, but it's really NOT our design. We just love it so much, and despite our best efforts, haven't really found a way to improve it!

[lemiant]

Originally Posted by AdamHeard

I know I probably sound like a desperate salesman now, but that frame looks like substantially more work than a proper west coast drive. A wcd doesn't NEED CNCing or anything fancy, 973 ran a very, very, very simple and reliable wcd for four consecutive seasons before my time.

I'm not tooting my own horn either, we've made some tweaks and optimizations, but it's really NOT our design. We just love it so much, and despite our best efforts, haven't really found a way to improve it!

Ok, your raw crazy loyalty has me interested. Can you tell me what the pro's Con's of this are versus six wheels with dead axles supported on both sides (http://www.chiefdelphi.com/media/photos/36993)?

[JesseK]

WCD requires only 4 pieces of very rigid aluminum tubing for its frame -- which is the key to its success. So long as bumper rules are complied with, it's still the simplest most versatile drive train frame for teams who have these capabilities:

1.) Welder who can keep things square
2.) Low tolerance, low slop drilling capability
3.) Some sort of milling capability is probably needed regardless of variant
4.) It doesn't hurt to be able to do your own gearboxes so you can customize the gearing while also driving chains to each end.
5.) It probably also doesn't hurt to be able to make custom wheels of any diameter/hub configuration

With WCD, I would have to figure out gearbox configurations for the wheel size such that the gearbox doesn't bottom out on the field when put into direct drive configuration. For 4" wheels, this is somewhat difficult without doing a custom gearbox (with plates). For 6" wheels, it's a bit better since a large variety of COTS gearboxes exist with decent spacing between the output and bottom of the gearbox.

Sheet metal is only simpler if the mentors in charge are comfortable with it and have th resources for it. It's like apples and oranges, imo.

Adam, show me a team with sloppy drill presses, hand drills, a basic lathe (and 3 tools), and a surplused mill who has done WCD ... then you'll probably be able to convince my other mentors.Until then, they want to do what we know with the drive train and focus learning on other parts of the robot. It's not me you have to convince, heh.

[AdamHeard]

Originally Posted by JesseK

WCD requires only 4 pieces of very rigid aluminum tubing for its frame -- which is the key to its success. So long as bumper rules are complied with, it's still the simplest most versatile drive train frame for teams who have these capabilities:

1.) Welder who can keep things square
2.) Low tolerance, low slop drilling capability
3.) Some sort of milling capability is probably needed regardless of variant
4.) It doesn't hurt to be able to do your own gearboxes so you can customize the gearing while also driving chains to each end.
5.) It probably also doesn't hurt to be able to make custom wheels of any diameter/hub configuration

1) No need to weld, robot delivered and took some beatings this year and it survived.
2/3) a poor quality manual mill is adequate, kind of like our poor quality manual mill....
4) This is certainly nice, but Super Shifters (we ran them stock in 08, and "stock" in 09) work just fine.
5) This is no longer as big as advantage as it used to be. The AM performance line is fantastic.

With WCD, I would have to figure out gearbox configurations for the wheel size such that the gearbox doesn't bottom out on the field when put into direct drive configuration. For 4" wheels, this is somewhat difficult without doing a custom gearbox (with plates). For 6" wheels, it's a bit better since a large variety of COTS gearboxes exist with decent spacing between the output and bottom of the gearbox.

The super shifter is a great choice here as you can change gears out in that final stage for easy ratio adjustment.

Adam, show me a team with sloppy drill presses, hand drills, a basic lathe (and 3 tools), and a surplused mill who has done WCD ... then you'll probably be able to convince my other mentors.Until then, they want to do what we know with the drive train and focus learning on other parts of the robot. It's not me you have to convince, heh.

Uhhhh... us right here! While we've recently (last 3 weeks) expanded on our in house capabilities, you described the capabilities of us in house. With some know how and practice our kids make very high quality parts (that often get mistaken for CNC'd parts). We do have a large amount of industry sponsors, but that only started for the teams 6th year of doing west coast drive. We get a lot of drive components CNCd and outsourced more out of convenience than necessity (the parts are ready to go really early in season, when sponsors are generally idle).

Also, most of the complaints you listed seem applicable to any drivetrain style. Our CAD models are out there, and I'm here to answer any questions (along with all the other teams that run it I bet). I've helped quite a few teams make easier to make WCD's that are tailored to the resources they have available to them.

Back in the day, I was also against WCD out of some preconcieved notion it was harder, and would make these massive plate sandwich drivetrains (294 07 and 08) that just can't compare at all to WCD in terms of weight or efficiency of manufacture. Once I saw and understood how simple, clean, and easy they are to make, I never looked back.

[Chris is me]

A west coast style drive can be done in a simple manner too. We don't even use bearing blocks (the trickiest part IMO), we just made some bearing holes on a manual mill and use a simpler tensioning system. We have an in house setup that's nothing to write home about and we did a west coast like drive quite easily. We even finished our frame earlier this year than any other.

I like the posted frame design for things like obstacle climbing, etc though. Pretty neat stuff.

[Aren Siekmeier]

We also have all the sloppy tools you mention (manual mill and lathe, some ok drill presses, chop saw, etc.), as well as basic welding that we can do square (which could be foregone with some more holes, gusset plates, and riveting), and a WCD is something I think is very much within our capabilities.

It seems to me that the biggest thing is easier maintenance of the wheels, but after just replacing one last night at the shop due to a failed bearing on our drivetrain that's supported on both sides, it was really a snap, so those benefits are really the last few percent. Also, frame simplicity and weight are improved.

We could even probably do the bearing blocks in house on our manual lathe and mill if we felt like spending a lot of time on it, but since we know some people with CNC capabilities we probably wouldn't bother. I actually think I would prefer dead axles because that gives you more wheel options (namely, plaction, omni, etc.) and you could just slot the axle hole on a manual mill for chain tensioning.

[roystur44]

You could also try using a Pem Stud.

http://www.pemnet.com/fastening_products/pdf/fhdata.pdf

Roy