pic: CV Robotics WCD 6wd Drivebase Prototype

[RonnieS]

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

[MrBasse]

Originally Posted by Sam_Mills

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.

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.

[R.C.]

Originally Posted by MrBasse

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.

Out of curiosity

What tolerance do you hold on the plasma cutter?

[MrBasse]

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.

[Dunngeon]

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

[JorgeReyes]

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.

[Jared]

Originally Posted by JorgeReyes

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.

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.

[Dunngeon]

Originally Posted by JorgeReyes

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.

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.

[JorgeReyes]

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

[asid61]

Originally Posted by JorgeReyes

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

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

[Dunngeon]

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

[StephenNutt]

Originally Posted by T-Dawg

Are CIMs glossy or am I clinically insane...

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

[Dunngeon]

Originally Posted by StephenNutt

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

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