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pic: CV Robotics WCD 6wd Drivebase Prototype
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Re: pic: CV Robotics WCD 6wd Drivebase Prototype
Why are you not using Versa Blocks?
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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. |
Re: pic: CV Robotics WCD 6wd Drivebase Prototype
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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. |
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.) :p |
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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 |
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.
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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.
Spoiler for A useful tip:
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. |
Re: pic: CV Robotics WCD 6wd Drivebase Prototype
Why did you guys decide on using chain instead of belts?
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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. Quote:
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I wasn't aware you could add cams to this type of bearing block |
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And those cams were invented for that kind of bearing block. ;) |
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EDIT. Andrew beat me to it. |
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Are CIMs glossy or am I clinically insane... :confused:
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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. |
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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 |
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.
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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 |
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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. |
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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. |
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 |
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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. |
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What tolerance do you hold on the plasma cutter? |
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. |
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
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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.
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Re: pic: CV Robotics WCD 6wd Drivebase Prototype
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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. |
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 |
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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 ![]() ![]() ![]() |
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