Questions about building a West Coast Drive with VersaChassis
 

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 :D

Re: Questions about building a West Coast Drive with VersaChassis
 

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

Re: Questions about building a West Coast Drive with VersaChassis
 

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?

Re: Questions about building a West Coast Drive with VersaChassis
 

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.

Re: Questions about building a West Coast Drive with VersaChassis
 

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.

Re: Questions about building a West Coast Drive with VersaChassis
 

With the new products from VexPro and WCProducts, building a quality WCD can be done really quickly with little to no machining capabilities. Just to put it in some perspective, we used only a chop saw to cut the frame members down to length, and a drill press to drill holes for the bearing blocks. And none of these requires any form of accurate machining.

We have used both types of bearing blocks. Both the new sliding bearing blocks, and the older ones. I would highly suggest you go with the new ones because you just need to drill one oversized hole and clamp the bearing blocks on each side and you are done.

I think you are also a little confused about mounting a gearbox. You said that you would use the Toughbox Minis, but if you are to use those gearboxes you will be unable to build a true WCD. A true WCD has the center axle directly connecting the wheel to the gearbox without any intermediate chain/belts/gears, and I think the only way to build with the Toughbox Minis would be to chain the gearbox output to the middle wheel shaft. The part you linked is actually a part of the WCD versions of the gearboxes. Pic Here and link to gearbox.

If I were you, I would just go with using one of the WCProducts gearboxes as long as you can afford them. They are $90 each for a 3Cim single speed, but they are so much simpler to mount into a WCD and reliable. We used them and had nothing but good things to say about them.

In short, sorry if a come off as to pro WCProducts/VexPro, but their new WCD stuff is just so incredibly good that as long as you have the cash to spend, (we spent about $7000 for a 3 cim single speed including tubing/hex shaft/bearings) I would just go with what works really well.

Re: Questions about building a West Coast Drive with VersaChassis
 

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.

Re: Questions about building a West Coast Drive with VersaChassis
 

The ToughBox Minis used this year direct drove the center wheel. Are you saying that I won't be able to mount it so that I can direct drive the center wheel?
The thing I need to check with that is if the output shaft is going to be long enough, or if that will have to be replaced as well. Unfortunately we can't afford two new gearboxes right now, so I am going to try and find a way to make that work.

Thad House was right about the inner plate not being included in the KOP this year, though. In that case I may be able to use the 2013 version then, which did include the plates.

Re: Questions about building a West Coast Drive with VersaChassis
 

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.

Re: Questions about building a West Coast Drive with VersaChassis
 

Although the Toughbox Minis were direct drive, they were built to interface seamlessly with the new sheet metal frame on the KOP drive base. It looks like it would be a lot different to use them in a WCD application.

It looks like it will be a whole lot more difficult to both design and machine, and with you stating how you are trying to limit the amount of machining you have to do, Joel Glidden's method looks like it requires a lot of precision machining to get working.

My team has a hard time accurately machining things, so we always look to use and buy as many cots parts as possible. I feel that if you even question your ability to connect the gearbox reliably, you should go and find the excess money to buy a gearbox which better interfaces with a WCD tubing.

Re: Questions about building a West Coast Drive with VersaChassis
 

Typical West Coast Drive gearboxes allow the chains and sprockets to go inside the gearbox. I suggest downloading a CAD model of the West Coast Product single speed West Coast Drive gearbox to study how it's put together. That setup lets you avoid putting the chains between the wheels and the outside edge of the frame rails, which is best avoided since it makes your cantilevered axles longer/bendier and shrinks the space available in your frame.

I'm certain that a custom solution can be created to connect a Toughbox Mini to a VersaBlock WCD setup; one way would be to make two separate plates and house the sprockets between them. Another way would be to put two halves of a VersaBlock on the frame rail and offset the gearbox from the rail with standoffs to create space for the sprockets. Either way, one would at least need to machine some plates with mounting holes located reasonably accurately.

Why does your team want to build a non-KoP drive train? If funds are pretty limited, going with the kit drive is a great way to keep costs in check. And this year's kit drive featured direct driven center wheels and belt drive - what's not to like about it? I like VersaChassis a lot, but it's not something I would recommend for a team if they lack the resources to buy or fabricate gearboxes to match it.

Re: Questions about building a West Coast Drive with VersaChassis
 

Here's an excellent post of the parts one required to build a versachassis by Andrew Lawrence:
http://www.chiefdelphi.com/forums/sh...40&postcount=2

Our team will also be building a WCD as an off season activity:
http://www.chiefdelphi.com/forums/sh...d.php?t=129473

For a close look at the versachassis in action, look no further than team Copioli's reveal video:
https://www.youtube.com/watch?v=ffe8V9g1jmQ
https://www.youtube.com/watch?v=8tJMiGBpWHQ

We are using the same calculator that Brian posted to figure out what pulley and belt to get from WCP:
http://www.wcproducts.net/how-to-belts/
You decide the pulley size and the centre to centre distance to derermine the belt size.
From what I can see in videos and pictures, seems like team Copioli uses a 30 teeth pulley. Somebody correct me if I'm wrong.

Re: Questions about building a West Coast Drive with VersaChassis
 

I don't have the CAD model of the plate that goes with the Mini's, but is there a reason that that plate wouldn't work?

The "why" has a couple reasons. First because it generally seems to be the superior tank-style drive. Also ease of maintenance hurt us badly this year and having something a bit simpler to access would help.
More than this, though, we want to focus on trying a variety of things in the offseason to better prepare for next season. A different shaped base (28" x 28"), a variety of wheels, and maybe different joysticks or controllers will help with that.
Third, we want to transition of programmer from Python to Java as well as get more than one student to work on programming. Programming a brand new drive base is something that could actually motivate a couple students to jump on programming.

Re: Questions about building a West Coast Drive with VersaChassis
 

Here's the CAD.

Re: Questions about building a West Coast Drive with VersaChassis
 

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.

Re: Questions about building a West Coast Drive with VersaChassis
 

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.

Re: Questions about building a West Coast Drive with VersaChassis
 

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.

Re: Questions about building a West Coast Drive with VersaChassis
 

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 =)

Re: Questions about building a West Coast Drive with VersaChassis
 

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

Re: Questions about building a West Coast Drive with VersaChassis
 

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?

Re: Questions about building a West Coast Drive with VersaChassis
 

Chain and sprockets may be a good idea as our team has no experience with them. I would have to factor in the costs of chain accessories like a breaker and holder(?), though, as I never want to do chains by hand/pliers again like my old team used to.
If I go with the round shaft I should be able to save ~$20 by switching to sprocket/chain, but the cost of accessories would mitigate that. Still though, trying something new has its benefits.

As for the side bearing block, I was going to use it to hold the bearings for the gearbox shaft. I was kind of assuming that you had something similar in your model as you aren't using the VersaBlock at the gearbox.

As for CAD, unfortunately no. I started learning CAD recently but don't actually have a spare computer to put it on. We are trying to find mentors to teach CAD, but as of now I am the only one learning it.

Re: Questions about building a West Coast Drive with VersaChassis
 

If you use #25 chain, get Dark Soul Chain tool, which costs about $40 with shipping. It eliminates the connecting links (weak links).

Chain for one WCD costs $10 vs ~$50 for four belts, so it pays for itself. With the sale on the AndyMark pulleys, the cost isn't much different either way, so I would focus more on whether you'd rather end up with belts or chains. I think it would be cool to run belts, but I also like having a bunch of sprockets and chain around so we can make up a manipulator chain connection pretty easily without ordering a specific belt or stocking a dozen different belt sizes. Chain is annoying in some ways, though.

Re: Questions about building a West Coast Drive with VersaChassis
 

Man, I would like to use that but if I go with #25 chain then I can't use the Vex Double Sprockets (They only sell #35 doubles) meaning that I would have to get 8 Single Sprockets which pushes the price even higher than with belts.
I do really like the idea of training the students with chains but adding in the cost of accessories pushes this up around $60 more than with belts. It's a tough choice.

Re: Questions about building a West Coast Drive with VersaChassis
 

You can always go with the lower cost choice for now and then revisit it in the future.

Re: Questions about building a West Coast Drive with VersaChassis
 

Yeah that's a possibility. Any suggestions for other #35 chain breakers? most of what I have found so far has been for chain sizes in the hundreds.

Re: Questions about building a West Coast Drive with VersaChassis
 

This looks like the tool we use.
http://www.amazon.com/Koch-7725010-R.../dp/B004HKIU4C

Re: Questions about building a West Coast Drive with VersaChassis
 

I use a flanged hex bearing pressed directly into the frame opposite the gearbox. Really this is bad practice. You shouldn't have more than two bearings on a shaft, and I have three (two in the gearbox and one in the robot chassis). I get away with it because two of the three bearings are hex bearings and they have a pretty sloppy fit with the hex shaft.

If you're going to do the same thing with round shaft, make sure you spin the output shaft by hand or wrench once you have the gearbox mounted to the chassis. If the torque required to spin the wheel is inconsistent or excessive, the bearings are probably over-constraining the shaft. This will kill your efficiency and lead to fatigue problems later if left uncorrected.

Re: Questions about building a West Coast Drive with VersaChassis
 

Huh, I didn't know that, thanks for mentioning it. I can't really tell from pictures of other WCDs around but how is this usually handled? For instance the WCP gearboxes all come with two bearings; should you mount them with no bearings in the tubing?

Re: Questions about building a West Coast Drive with VersaChassis
 

For #35 chain I'm kind of partial to this one:
http://www.ombwarehouse.com/-35-Chain-Breaker.html

BTW, for #25 I recommend:
http://www.davesmotors.com/s.nl/it.A/id.2258/.f

If you notice, they are both similar in design and operation.
I highly recommend both of them.

Re: Questions about building a West Coast Drive with VersaChassis
 

Awesome I was looking for a #35 version of that DS one. One question though, the thing I remember hating most about chains is trying to put pins back in to assemble the chain once it is under tension. Using a chain holder seems like it would make this significantly easier, but it looks like the chain breaker you linked may not be able to be used with a holder. Can you use them together? Or do you have to manually pull the chain in that breaker to line it up?

Re: Questions about building a West Coast Drive with VersaChassis
 

We have never used a chain holder. The chain breaker has teeth and a lock pin that holds the chain in place. It correctly aligns the links so you can just push the pin in. It's just like the DS one it that respect. If you have to stretch the chain to put the pin back in, it's too short and will likely fail from being over stressed. (Yes, I know chain stretches some).

Re: Questions about building a West Coast Drive with VersaChassis
 

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.

Re: Questions about building a West Coast Drive with VersaChassis
 

Oh nice I see that now. The DS only has one pin to align one side of the chain (as far as I could tell) so having pins on both sides really makes a difference for that one.

Yeah I knew the output shaft was tapped at one end but I didn't know what to do about all the other shafts for the front and back wheels. I am thinking now that we will just tap each shaft manually and use bolts/washers just like the output shaft.