WCD-Belt Driven CAD practice




I have been working on this for a couple of days and I think I have taken it as far as I want. I think my team might prototype this in the coming fall. Well anyways feel free to comment/give suggestions. BTW the bottom plate pattern is just there to simulate it having holes it is in no way the final or complete pattern, it might end up being solid with no hole pattern. ALSO, I may have to widen the frame so I can get the gearboxes in and out. As of right now it looks like the gearboxes will not have enough clearance where the motors are, in order for them to get in and out.

Specs:
6 Wheel WCD belt driven
No weld frame held together by 3/16 rivets and gussets
1/8" center wheel drop
4in x 1.5in wide Colsons
1/2" Hex live axle system
Axle “sandwich” with bolts to hold on pulleys and keep bearings in
WCP WCD Shifter- geared for 16/6fps
weighs 19.3lbs without rivets that hold it together
24t 5mm GT2 x 9mm wide Belt and pulley system.
bent bumper mounts that rivet on to the side of the frame

Feel free to ask if you have questions or need clarifying.

Thanks for taking a look

EDIT: Shout out to Akash Rostogi for being the best help ever with this frame and for being my go to help in frc.

That’s really cool!

If you’re looking to save weight, our team has found that its usually better to go for a thinner wall on aluminum box tubing instead of lightening holes to reduce weight.

Looking good! A little advice: your gussets don’t need to be as big as they are. It’s not bad, but you could make them a bit smaller to use less material. Also, the extrusions on the sides that I take to be bumper mounts could be a little more solid. If they are indeed bumper mounts, it looks like a good collision would bend those mounts instantly.

Awesome job, though! Keep on submitting your models here and you’ll get a lot of helpful criticism.

Edit: Also, while the pocketed aluminum bellypan is nice, it’s not something you absolutely need. I find it’s just there to look good, if anything. 6mm thick plywood has the strength you need with low weight as well, and is cheap and easily machinable. Plywood doesn’t have the “cool factor” of a pocketed aluminum bellypan, but functionality-wise it does the same thing the same ways and is a lot more resource-friendly.

Yeah, I would go with 1/16th wall but Then I would have to support the axles some how. It is 1/8th right now and I am pretty happy with it’s weight as it is. I may in the future switch to 1/16th wall and then make bearing plates.

Interesting thought. The gussets are 3.5" x 4". I may shave 1/2" or 1" off of them or maybe not idk lol. You were right, those are bumper mounts. How would I go about making the mounts stronger? They are aready .090 5052 aluminum as it is.

Yeah, looks like you can easily shave an inch off the long end of the gussets, and a half inch on the two shorter ends each.

What makes your bumper mounts weak is that there is nothing supporting most of the front where the bumper makes contact. There is a large hole in between the mount, which is likely where something is going to cave into. If you still want to use that method of mounting, I’d suggest putting some wood or another light but solid material inside the gaps to prevent them from bending inwards. Another option is to make a rectangle around your base using 1x1x.125 aluminum to add bumpers to and to increase mounting space (especially if you’re not welding, mounting space for gussets is important, and it looks like a lot of the space on your 2x1’s is taken up). Here is an example of the surrounding 1x1 rectangle: http://media.team254.com/2012/08/drivebase.jpg .

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Andrew, I can assure you (based on my experiences with that design) the bumper mounts are just fine. This is also why we prototype, to find out what breaks! :slight_smile:

This looks great. We went to a belt WCD this year and loved it. My big question is with the WCP dual speed. Did you have to increase the size of the spacers and the hex shafts in the gearbox or did the 2 9mm pulleys fit into the basic gearbox. Also did you use the regular or the WCD model.

This looks like the start of a really great design! You’ve arrived at what many CDers would consider a “classic” WCD, albeit with a few small differences. I think you’ll be very pleased with this design if you ever run it, especially with the WCP DSes.

Are you planning on doing exact C-C for the wheels? If so, definitely try it out first before you do it in the season. If it works, it works great, but if it doesn’t it can really bite you in the behind. If you don’t want to do exact C-C, add some sliding wheel trucks and you should be good to go.

You’re going to want to offset two of your four wheel pulleys into the center. Otherwise, the second pulley in the DS won’t have anywhere to go. Also, double check that the pulleys won’t ratchet at the loads they’ll be experiencing. Gates publishes some great tables that show the maximum torque at a given speed with a duty factor of 1 (if your duty factor is .8, it still should run fine for FRC purposes). Personally, I’d either bump your sprocket size up to 28T or run 15mm belts instead, but if the tables say it will work, it will work. Just make sure.

I actually really like those bumper mounts. I know 254 does them in a slightly different way, which is stronger, but you shouldn’t have any problems with them. Of course, like Akash said, that’s what testing is for.

I highly encourage you to build a drive like this in the offseason! It’s a great experience, and is a good way to train kids too.

That looks a lot like what our team did this season!

Instead of using rivets for the gussets we used bolts so that we could remove the drive side completely to work on the gear boxes though.

Due to the belt pulleys being larger than sprockets, the gearbox will have to be widened by about half an inch +/- .125". Although it will take some machining to get this done, (some very basic machining) I see it as a benefit rather than a hassle. With belts rather than chains, after they are set since it is exact c-c you never have to touch them again unless something bad goes wrong. like thrown belt or ratcheting occurs or other issues caused usually by human error. I forgot to mention I added .003" to the c-c distance to get the tight fit on the belts. But I have seen some very good and bad things said about belts. Mainly good. So I am giving them a shot. I put the WCP WCD gearbox in there because it was built for the type of frame I designed so it was basically a plug and play. I guess you could try and use the regular WCP shifter but I didn’t. Glad I could help.

To be clear, Damprobot, this is all for a prototype to test out some sponsors we found for Cooper’s fantastic team. :slight_smile:

I have high hopes for their team, Cooper is awesome at absorbing information from all over and learning very quickly. They are also backed by some former mentors of 57 and 624.

We are also backed by people like you who are always willing to help :smiley:

I was doing some more messing around and found that if WCP would have made their gearbox a little more than an 1/8th of an inch wider maybe more like 1/4", we could have fit 5mm gt2 pulleys in there that are 9mm wide. It is so close. I wish WCP would just make a version of their gearbox for people like us who like to use belts…

Yet again, I did some more updating to make the bumper mounts legal (the distance between them was not <= 8in.) and I made their flanges beefier. Lastly, I widened the frame an inch and a half on each of the end tubes to better use all of the frame perimeter rule except 1 inch of it. so the frame perimeter is now 111" vs 108"

Talk to RC about this. He’s typically very responsive about design requests like that. It might even end up as one of the models for next year.

We did a very similar mod to the DS last week, except we were going from a Standard type to one that could fit one VP sprocket. It’s quite simple. You just need to turn a few spacers and one 3/8" shaft.

It can be made to work. We used stock WCP gearboxes with 9mm GT2 pulleys this year. Loved it. Two double flanged pulleys won’t fit within the transmission so you need to create a double pulley with one flange between them. It fits just barely. We modified pulleys from sdp-si and used 060 flanges. Using pulley stock would have probably been easier/better.







Oh man. You are going to have to go into more detail of how you made it work. I am really interested.

Cooper, you can buy pulley stock and cut it to size on a lathe. You can also remove flanges from Gates pulleys pretty easily and add in your own shim to act as a center flange.

We did the almost did the same thing, belt drive WCD with WCP gearboxes.

We were able to fit 9mm GT2 pulleys in there no problem.
http://31.media.tumblr.com/624ace34b1263e41576f971cbc011dfd/tumblr_mhj3psjwO21s3vcgvo7_1280.jpg I personally machined the pulleys out of 3/8 alum plate.