Questions about building a West Coast Drive with VersaChassis

[Monochron]

I will be leading our team in an offseason project to build this summer to build our first (and my first) non-KOP drivetrain. I decided to base most everything on VexPro's VersaChassis as we have very little machining capabilities and to use the Toughbox Minis that came in last year's (2013) KOP.

When I started to look into what parts specifically I would need to order I realized I still had quite a few questions as to what exactly would be needed. Here are all the questions I have come up with that I need to answer before I can begin:

1. In the power trasmission, how does the pulley connect to the shaft without sliding off? Shaft collar?
2. How does the wheel connect to the shaft? Same as the pulley?
3. In the VersaChassis picture it looks like half of a VersaBlock goes on the wheel side of the tubing across from the gearbox. If this is so, how does that VersaBlock attach?
4. Where would you use the "WCP side bearing block"?
5. I am right to assume that the "WCP Gearbox Bearing Block" is used to hold the bearing on the gearbox side of the tubing for the gearbox shaft?
6. Lastly, I am currently trying to figure out how to use the "WCP How To: Belts" I was expecting to enter a tooth count for the pulley and the center-to-center distance and get back a belt length, but I guess there is more that I am missing.

Thanks in advance, any help at all is appreciated

[Gregor]

There's a lot of useful information in this thread about using the Versachassis.

http://www.chiefdelphi.com/forums/sh...d.php?t=123281

As for belt calculators, I prefer to use this one.

http://www.sdp-si.com/cd/default.htm

[Monochron]

Originally Posted by Gregor

There's a lot of useful information in this thread about using the Versachassis.

http://www.chiefdelphi.com/forums/sh...d.php?t=123281

Awesome, one the longer replies on there answered one of my questions. Damp Robot says:
"assemble your drive gearboxes, and mount them to your side frame tubing by bolting them onto a half versablock located on the outside of the tubing, with their output shaft going through a bearing in the versablock."
Though this doesn't match the reference picture. Considering that I am using a ToughBox Mini instead, would you forsee any issues? Can I just go with long bolts straight through the mounting holes in the VersaBlock?

[Thad House]

Originally Posted by Monochron

Awesome, one the longer replies on there answered some of my questions. One part says:
"assemble your drive gearboxes, and mount them to your side frame tubing by bolting them onto a half versablock located on the outside of the tubing, with their output shaft going through a bearing in the versablock."
Though this doesn't match the reference picture. Considering that I am using a ToughBox Mini instead, would you forsee any issues? Can I just go with long bolts straight through the mounting holes in the VersaBlock?

Didn't the KOP toughbox not include a plate for the output this year? I thought it just included the housing, and that housing mounted to the side rails. If that's the case, you would need to machine a plate so the bearings have a plate to sit in. You could then put the versablock mounting holes into that plate, and have everything line up.

[Aren Siekmeier]

1. On the Toughbox gearboxes, the output shaft is usually tapped to 1/4"-20 at the end so that you can put a washer and button head screw on to retain the pulley and any spacers you might add. However, most "west coast drives" have the drive gearbox directly driving one of the wheels, rather than via an additional belt/pulley stage.

2. If you are running a West Coast drive, you'll have to design this bit. The most common options are to either copy the toughbox output shaft, by tapping the wheel shaft and retaining the wheel with a washer, or to machine a retaining ring groove on the end of the shaft.

3. The half VersaBlock gets bolted to the gearbox face rather than to another VersaBlock half. This is so you don't need to machine a bearing hole in your frame, you can count on the VersaBlock to hold the bearing in place for you.

4. The WCP side bearing block is another bearing block that takes up less space around the frame rail. It can be used in the same places, however, it requires a square slot machined in the side of the tube which it slides in. This requires some more sophisticated machining than the the VersaBlock.

5. You are correct, the WCP Gearbox Bearing Block is a half bearing block that attaches to the drive gearbox around the tubing to support the bearing on the main drive shaft. This is just like the half VersaBlock you mentioned in #3, but using the WCP block instead.

6. Yes. In the case of a WCP block, this large hole has to be a square slot for the block to ride in, but for a VersaBlock it just needs to leave room for the shaft to not hit anything, and can be pretty much any shape.

7. The WCP Belt calculator is designed to show you the WCP/VexPro belt/pulley options that will work for your desired center to center distance, and unfortunately does not go the other way. The SDP/SI calculator Gregor linked is similarly limited to SDP/SI's selection of belts and pulleys (which is larger), but it does the calculation with any set of inputs, filling in the missing numbers, so many of us find this one more useful.

[Joel Glidden]

We built a drive like this for our 2014 bot. The biggest difference from what you're planning is that we used #25 chain instead of belts. I'll upload our CAD (w/ a full set of drawings) when I get home tonight so you can see how we mounted the TB minis. We ran 4" x 1.5" Colsons on live axles with the TB minis geared 8.45:1. You will need the long hex output shaft (am-0801) for this design.

Here's a pic to give you the general idea.

[Monochron]

Originally Posted by Joel Glidden

We ran 4" x 1.5" Colsons on live axles with the TB minis geared 8.45:1. You will need the long hex output shaft (am-0801) for this design.

Awesome, thanks for pointing out the part I need. I'm eager to see how you used this year's minis because I haven't quite figured out how I would mount them.

[Joel Glidden]

Originally Posted by Joel Glidden

We built a drive like this for our 2014 bot. The biggest difference from what you're planning is that we used #25 chain instead of belts. I'll upload our CAD (w/ a full set of drawings) when I get home tonight so you can see how we mounted the TB minis. We ran 4" x 1.5" Colsons on live axles with the TB minis geared 8.45:1. You will need the long hex output shaft (am-0801) for this design.

Here's a pic to give you the general idea.

Here's the CAD.

[Monochron]

Originally Posted by Joel Glidden

Here's the CAD.

Thanks, that's awesome. One question though, what material / fasteners did you use the mount the gearbox to the frame? It looks kind of large piece of a large aluminum round stock with the ends tapped. Or it could even be a round shaft from Vex/AndyMark with the ends tapped as well.

[Joel Glidden]

The blue part is just a bent aluminum sheet metal bracket (1/8 in thick). It bolts to the TB mini through the top two holes that secure the mounting plate to the plastic housing. Then it is secured to the top of the robot frame via four 10-32 screws and rivet nuts (McMaster 93483A661). The green cylindrical parts are just some stand-offs we made from half inch round stock that we drilled through with a .196" clearance hole. We secure the gearbox to the side of the frame by just running a long 10-32 screw through the TB, the standoffs, and the frame.

Refer to drawings 4293_2014-005 and 4293-2014-018 for the standoff and the bracket.

Edit:
Also, we cut the bottom off of the TB mounting plate for ground clearance. You can just trace the profile of the housing on the plate and then use a band saw to cut it down. Drawing 4293_2014-019 shows all the mods we made to the mounting plate.

[Monochron]

Thanks for all the replies everyone, the project is really coming along. A couple new questions that I came up with:

1. I have never tapped anything harder than aluminum before, but we have a fairly decent set of taps that isn't showing too much wear. How possible is it to tap the ends of this shaft in order to secure pulleys/wheels?
2. I can save some money by going with round shafts in stead of hex. Will this long shaft (meant for the ToughBox Nano) work in the ToughBox Mini?
3. Here is my total list of items to purchase, is this a reasonable price to pay? I was expecting a little lower as it would end up being a good deal greater than the voucher amount you get if you go without the KOP drivetrain.

[Joel Glidden]

1. The taps you've been using for aluminum should work fine for that shaft.
2. See below for a screenshot of the TBNano round shaft installed in a TBMini. It fits, but you will need a hex bearing. Also, there are two things to note. First, the hexagonal portion of the shaft protrudes about .150" beyond the bearing. Make sure it's not going to interfere with anything in your design. Second, the TBNano shaft is .335" shorter than the TBMini long hex shaft that is used in the 4293 design.
3. Will take a look at your shopping list as soon as you share the gDoc with me =)

[Monochron]

Originally Posted by Joel Glidden

[*]Will take a look at your shopping list as soon as you share the gDoc with me =)

Ha, duh. Fixed, should be open to everyone now.

[Joel Glidden]

Seems like chain and sprocket would be cheaper than belts and pulleys. Also, I'm not sure why you need the WCP side bearing blocks. Do you have CAD you can share?

[BJT]

We have built west coast drives for the last several years using either a toughbox or supershifter with the long hex aluminum output shafts. the wheel is held on by the screw in the end of the shaft, the sprockets to drive front and back are between the inside of the frame and the transmission. the transmission is then mounted to frame crossmembers.