27-10-2014 13:30

Munchskull

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Why are you not using Versa Blocks?

27-10-2014 13:53

RonnieS

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

They might be using the COTS WCP ones or one they machine in house. Its dark so I can not tell much. We used versa blocks last year and are switching to the WCP version because...

1. We wanted to enter a new field this year with machining. Something as simple as slots for them is a good practice that is not super complex.
2. It gives a MUCH cleaner look.
3. Although super minimal, it saves space and some weight.

27-10-2014 13:57

Boe

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

4. You can mount things right above the slots easier

27-10-2014 14:01

Munchskull

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Sorry I meant the WCP Versa Blocks. It does not look as if they are using them, however i could be wrong.

27-10-2014 14:34

AdamHeard

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

I think a waterjetted bellypan only makes sense for a handful of teams (and it's still wastefull then...)

Garolite or 4-6mm high quality plywood are plenty strong, and easy to mount electronics too.

My personal preference is the wood painted black.

the water/laser time put into a bellypan can cut out several systems worth of parts elsewhere on the robot.

27-10-2014 14:36

Jean Tenca

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Looks great guys!

And I wonder how many people went looking for Glossy CIMs after seeing this post. (Guilty.)

27-10-2014 18:49

Dunngeon

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Bingo, the Versa Blocks take up extra space and change the profile of the extrusion. We are using WCP Side Bearing Blocks in this drive. Sorry about the black parts, this render was the only one I had on hand.

We have a shop that's offered up their CNC Plasma Cutter. We plan to cut it, then check tolerances to see if it's good enough for use. If it isn't, our fallback is to use one of our schools CNC routers to machine a wooden bellypan and paint it black.

I got a few PM's about the glossy CIM's. Regrettable to report, but they don't actually exist

27-10-2014 20:23

Adrian Clark

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

I cannot stress enough how important it is to test new fabrication methods before the season. In 2013 I tried to cut a bellypan out of .090 5052 Al on a plasmacam machine, a machine I had never used before. When I came to the shop and showed the staff what I was making they told me it wouldn't work, and they were right. As I was cutting out the profile the sheet began to warp, I had to give up shortly after I started because the sheet bent up and hit the torch. This is exactly what I was warned would happen.

Before you take the time preparing to go to your sponsor and make the test parts I recommend you talk to an operator first. They will know the machine and it's limits and can tell you if your parts can be made on their machine and even give you tips on how to design your parts to be easier to cut. The main things you need to convey to the operator is the materiel, its thickness, and the complexity (run time) of your parts. With that information they should be able to tell you if they can cut them without the sheet warping.

There a several teams with in house CNC plasma cutters, you should be able to find them with a quick search. I would recommend talking to them as well, they can provide you with valuable insight on how to best utilize a plasma cutter for an FRC team.

-Adrian

27-10-2014 21:10

Ethroes

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Looks nice guys. Will you have a prototype on your Bunnybot robot or will you be using another drive train? For last year's Bunnybot competition, we field tested our first swerve modules on 2471-A. It was a valuable system for us and I recommend it for you guys if you have the time and budget. Of course, a gen 1 swerve drive is bound to have a few kinks to work out, but you never know. It's just a tip.

27-10-2014 21:22

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

If you do insist on having a machined bellypan, make yours lighter. We shoot to have ours be around 1.5 lbs for an 1/8" thick sheet of 6061 aluminum. I noticed the strand thickness on your bellypan is much thicker than the thickness we usually design for, so you could probably go a lot thinner than you currently do.

I'm assuming you are choosing to use a custom transmission because it fits your resources better than a COTS one, though if it doesn't I could always lead you to some sources about why COTS transmissions are a great solution.

All that aside it looks like a very promising design that will serve you well should you choose to use it for the 2015 season.

27-10-2014 22:21

dragon_pilot

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Why did you guys decide on using chain instead of belts?

27-10-2014 23:04

Dunngeon

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

I hadn't considered that it would warp, thanks for pointing that out! I'll look into it. Our sponsor wasn't sure, they are primarily a steel outfit.

I neglected to mention that we are building this drive right now, the 2x1 entered machining yesterday. Unfortunately for swerve drives, we subscribe to the "swerve is never necessary" ethos. Even though I think your drives are pretty brilliant.

The strand thickness was fairly arbitrary, we weren't sure how thin we could go and still have torsional strength, looks like we can scale it down a fair bit (though not to your level....yet)


I'd prefer a COTS gearbox over this one, but we use the gearboxes to teach advanced CNC code to students. All of the CNC code used to mill these gearboxes is handwritten. The only other advantage to this gearbox for us is it sits much lower than a WCP or Vex gearbox in the frame. Personally, I'd like a 2-stage gearbox (16.8 FPS is high) w/ shifters, but team history precludes that effort for the time being.

It simplifies our drivebase, with belts we would need tensioning blocks and would also run the small risk of snapping a belt. We ran our drivebase without chain tensioners last year, and that's carrying over because it worked so well (71 matches, still within tolerance).

27-10-2014 23:16

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

If you are not tensioning your chain, then why do you have bearing blocks instead of just placing the bearings in the tube? If you have milled slots in your tubing and bearing blocks like you mentioned, it is a simple addition to have cam tensioners added in that could easily stop a potential problem from happening. They're no work at all for a season-long reassurance.

27-10-2014 23:41

Dunngeon

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

To be honest, we weren't sure how the cantilevered shafts would affect the 2x1 bearing holes. Last year our shooter utilized 2x1 with bearings mounted directly into the 2x1. Over the season, the pressure caused the holes to ovalize. The forces aren't equivalent, but the construction is. I linked a picture of our shooter mechanism (JVN Cam).

I wasn't aware you could add cams to this type of bearing block

27-10-2014 23:44

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Look at 2791's recent drivetrains. I'm sure Chris Picone can elaborate more on their processes, but they run a C-C WCD variant without blocks and haven't experienced any problems that I'm aware of.

And those cams were invented for that kind of bearing block.

27-10-2014 23:44

Thad House

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Those blocks are designed to be put in slots and moved by cams. That's exactly how our drive worked last year. If you use the blocks, it doesn't hurt to slot them and make them slide.

EDIT. Andrew beat me to it.

27-10-2014 23:58

Dunngeon

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

This is why I love Chief Delphi, I feel stupid for missing that ... Thanks for pointing it out

28-10-2014 00:02

Oblarg

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

I learned that a month ago, and had the exact same feeling.

28-10-2014 00:21

T-Dawg

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Are CIMs glossy or am I clinically insane...

28-10-2014 00:30

Merfoo

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

I'm pretty sure CIMs are not glossy...

28-10-2014 00:34

asid61

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Nice drivetrain! Very clean, looks good. A few questions, if you don't mind:
1. What is the weight with what is shown in the picture?
2. What size wheels are those? Are they custom or COTS? Tread?
3. What is the thickness of the 2x1 and the bellypan?
4. How are you planning on tensioning?
5. Are those gearboxes mounted directly to the 2x1 or via standoffs? If it's the latter, change it to the former.

A small recommendation: Make sure the gearboxes shown have the same mounting hole pattern as either the Vex or WCP gearboxes, just in case. Or both even.

28-10-2014 00:38

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Read the thread. Half of your questions were answered within it.

28-10-2014 00:42

Dunngeon

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

1. Mass Properties says 40lbs (which is heavy)
2. 4in, custom, they will be 70a Polyurethane
3. 1/8th and 1/8th
4. In thread
5. The front plate mounts directly, it's already setup for Vexpro IIRC

28-10-2014 00:44

T-Dawg

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

I just updated the mass properties, and it gave me approximately 40lbs. I'll edit this post if I find any mistakes in the settings.

28-10-2014 00:48

Aren_Hill

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

I've had to cut a fairly large sign out on a plasmacam machine and ruined a nice piece of material due to this issue, I then tried again but leapfrogged around the piece doing various cutouts far away from others. This technique allowed enough time for the sheet to stay relatively cool and prevent warping, but it did take awhile longer.

Sometimes all it takes is the right technique.

(also CIMs are Gloss black paint, just not as glossy as that render, and the end caps are tumble finish)

-Aren

28-10-2014 02:05

Aren Siekmeier

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

We ran into the same issue with the first rev of our 2013 bellypan and had a much better time after "leapfrogging" on the comp bot version as you described.

28-10-2014 07:56

MrBasse

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

The Plasmacam software will cut the holes in the order they were created. So if you take the time in your pre cut operations to lay out your design with cutting in mind you can avoid this problem all together. I have cut many 4x4 sheets of thin steel and aluminum with no warping and my torch running full power at 45 amps. Speed is also important, if you are cutting that thin of a sheet the machine should be zipping along at a maximum speed of 380 IPM according to my book. If you aren't careful, moving that fast can be mildly terrifying.

28-10-2014 11:24

JesseK

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

I really like this approach to bumpers and mounting. For a pre-season prototype the most significant advantage of it I see is the ability to change wheel size without re-designing things for ground clearance or field obstacles. This should allow for some fast Day 0 answers.

Personally I'd adjust only one thing about the bumper system, and that would be to add a "wall" (like half of a 3"x1.5" C-channel, probably only 1" length) at the very center of the front & rear rails in order to give the upper part of the bumper some support against hard collisions. As it stands, it seems like the bumper would flex a lot if hit in the middle by a team whose bumpers were not at the lowest possible point of the bumper zone.

28-10-2014 13:10

Sam_Mills

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

In 2013 we tried to use our plasmacam for the exact same operation and had the exact same issue. Luckily it was in house, so we were only wasting our own time and resources, but we quickly learned a plasma cutter is not a precise machine, even if the software and rigging is.

Warning you now, do not try to do bearing holes or gearboxes with the plasma cutter. You could do a solid 1/16 Al bellypan, if you just use it to make ziptie holes for your electronics. Think of the plasma cutter to be just more precise than a bandsaw, that can also do pockets. If you have access to a manual mill, that should get you most of what you need for a WCD.

28-10-2014 13:37

RonnieS

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

221 Robotics also has been putting bearings directly into the 1x2" tube without bearing blocks. Although this is a chain-in-tube design.

http://www.team221.com/viewproduct.php?id=140

28-10-2014 19:55

MrBasse

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Before you give advice like this you should calibrate, tune and use the proper equipment and consumables. Don't base advice off of your bad experiences. We have great success with our plasma table on steel and aluminum for bearing holes and thin sheet as well. We just cut a plate for a gearbox last week and it is working fine after cleaning up a little dross and a slight bevel.

One of our sponsors just cut 1" thick steel for mounting forks to a front end loader that needed a perfect 2.25" diameter hole. They used a plasma cutter and didn't even clean up the edges. They are perfectly straight, perfectly sized, and fit like a glove. It is all about using the machine properly and with the correct settings.

28-10-2014 20:15

R.C.

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Out of curiosity

What tolerance do you hold on the plasma cutter?

28-10-2014 20:35

MrBasse

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

If cutting fast and I don't care it gets up in the .030-.050 range. But if I take my time and get the settings right it is under .010. I'm not saying we don't do a little cleanup after cutting, but it is far more accurate than I am.

I have cut three plates for our mockup gearbox and on all three the gear mesh is very close to perfect.

29-10-2014 18:50

Dunngeon

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Wow, thanks for all the machining advice. We are going to talk to our sponsor and make a decision. I'll post back here once we are finished

24-11-2014 19:16

JorgeReyes

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

I noticed how the 3 cims are really close to each other. How were you able to achieve this because I found that while its possible to get a small gap by using a smaller tooth gear, it wasn't possible to get such a small gap because you are limited by the bearing size (.375X.875 flanged bearing) which interferes with the placement of the cim motors.

24-11-2014 19:33

Jared

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

The 0.375" ID 0.875" OD bearing used here is thinner than the plate, so it's okay if the CIMs overlap with this bearing. You should put the flange of the bearing on the inside of the gearbox where the CIMs aren't.

24-11-2014 20:49

Dunngeon

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

There were 3 solutions

The first was use plate thicker than the Bearing, we went this way because we had 3/8 plate left over from last year and it was quicker than waiting for thinner stock to arrive

The second was to make cim-spacers, which would offset the CIM face. Then pocket out the required curve in the spacer to make the bearing fit. A little bit hacky, but I've tried it before. Another important note is it increases the overall length of the gearbox, pinching the bellypan even more

The third was to flip the bearing around, then use the overlap from the cims to hold the bearing in the hole (aside from the press fit).

We chose the first simply because we didn't want to waste time on the CNC. In the future, with a single reduction, I'd prefer 1/4in plate and method 3........ Depending on the game next year, I'd actually prefer a 2-speed over the single reduction.

In other news, I got the CNC plasma cutter dialed in and thus far I haven't seen any warp. I cut 5 of the diamonds into a test strip, running at ~45-50 amps and 130IPM. There wasn't any warp, but perhaps more interestingly, the cut edge was cool to the touch immediately after cutting. I'll be cutting the bellypan next Monday, and I'll document that more throughly.

26-11-2014 13:06

JorgeReyes

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

I think that the reason I am unable to have the 3 cims so close to each other in my gearbox is because it is a shifting gearbox. From what I can tell, the gearbox you have on this drive train is a single speed. Basically my gearbox is the same as the WCD DS gearbox but with smaller shafts for the idler gears which means smaller bearings and a closer spacing between the bottom 2 cims to the top cim.

It would be interesting to see if anyone has gotten the cims with a small spacing using a dog shifting gearbox

26-11-2014 16:16

asid61

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

If your gearbox is custom, you could make it in the 192 style. See their thread on their 2014 gearbox with the flipped cims.

07-12-2014 23:42

Dunngeon

UPDATE!

Hey CD,

Small update today

The drivebase has been finished for a few weeks, I'll post pictures soon.

Our first revision of the bellypan, which was CNC Plasma Cut, failed. We had issues with air pressure dropping below 65 PSI, and the entire table wasn't flat which is why part of the pan wasn't cut. We plan to either retry with the CNC Plasma, or route a wood/poly-carbonate sheet.



We are waiting for parts, seems like all of our orders have been held up along the way.

Our wheel hubs have been finished, but are missing tread for the reason above

01-01-2015 17:05

StephenNutt

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

A matte black dissipates heat faster than a glossy black. (I've even been thinking about painting the CIM coolers matte black )

01-01-2015 18:14

Dunngeon

Re: pic: CV Robotics WCD 6wd Drivebase Prototype

Are you doing this in an effort to increase convection emissivity or radiation emissivity?