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pic: DeWalt drive base
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Re: pic: DeWalt drive base
Correct me if I'm wrong, but isn't it risky to use two shifters on the same side?
Suppose one of the servos stops shifting... Then you'll have two gearboxes chained together running at different speeds. The DeWalts will strip themselves, and you'll lose half your drive train. Yes, it is an unlikely scenario. But its the kind of disaster that could ruin your day. |
Re: pic: DeWalt drive base
and why 8 40 amp fuses and 10 victors
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Re: pic: DeWalt drive base
It wouldn't be quite as risky if you didn't chain all 6 wheels together...just connecting the middle wheels to the back wheels...I would probably try that first and see how it drives before added a second set of chains. On the other hand, I have seen other teams like 418 use this configuration successfully with no shifting problems
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Re: pic: DeWalt drive base
I'm intrigued by your frame design. What made you do the two triangles?
This would make manufacturing it take a bit longer, as well as welding it slightly more difficult. I personally would have just run the bars straight across, which would have also given more area to mount to for other mechanisms. Looks like and interesting idea, good luck with it! |
Re: pic: DeWalt drive base
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This is a possibility. If the servos do not shaft at the same time one or more of the following might happen: The Dewalts might break:eek: (they are very strong) the CIM might burn out (unlikely) the sprockets might break the chain might break If this happens it will be bad. The plan is to have another 1 or 2 spare side modules ready to go on.:cool: It will be able to come on and off in just a few minutes, to we will be ready to drive again in the next match. If the drivers realize that this is happening during the match they might be able to shift one dewalt into "neutral" (between 1 and 2 or between 2 and 3) and use the other one. I really don't know how likely this is. Quote:
I chained them all together because that way each of the 6 wheels has the power of 2 CIMs. If you did what you are saying you would not have as much power to each wheel itself. Quote:
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DB |
Re: pic: DeWalt drive base
Slick design, I'd love to see pictures of the real version, and perhaps some battle reports, so make sure to keep us updated after next season.
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IF one of them didn't shift, then the DeWalt that didn't shift would just be powered by the one that did, so it shouldn't create any significant damage (though it will be quite obvious something is wrong). If this happened, I'm sure the driver would just shift back and stick with that gear for the rest of the match. But again, this is a very unlikely scenario if you follow the whitepaper word for word and your code does what you want it to. Quote:
If you have one DeWalt powering 2 wheels, and another powering 1 wheel, you will have a significant power bias. Think of it this way, you get into a pushing match, your back wheels have their own CIM-DeWalt to themselves, and the middle and front wheels share another. While the back DeWalt easily delivers enough torque to slip your back wheels (creating significant wear on the thread, and reducing your traction) your other DeWalt struggles to provide enough torque to the the middle and front wheels. I'm sure you COULD distribute the weight such that the traction of the back wheels is the same as the combine traction of the middle and front wheels, but that seems unnecessarily constraining. Another advantage is that if one of your back wheels isn't contacting the ground, the wheels that are contacting the ground still have the power of both CIM-DeWalt assemblies. This might seem like an unlikely scenario, but if you lower your center wheels (as most teams with 6 wheel drive do), and your center of mass changes (you pick up a heavy game piece, for instance) then before you realize it you're driving around on your center and front wheels... and half your power is uselessly spinning wheels that aren't contacting anything. |
Re: pic: DeWalt drive base
This is a very cool, interesting design.
Do the Dewalts work good on your robot? Was it hard to make the Dewalts and put them on? |
Re: pic: DeWalt drive base
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1/8" wall box tubing is very strong. A rectangle would work just fine. You've seen our robot drivebase this year, right? All rectangles and we never had any problems with it bended (even when people stood on it for various reasons). |
Re: pic: DeWalt drive base
That CAD looks amazing, nice work! :)
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Re: pic: DeWalt drive base
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It took a fair bit of work to modify the DeWalts, but it was still less than any other 3-speed transmissions I know of and that we were capable of making with our limited resources. |
Re: pic: DeWalt drive base
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Keep refining this until it is 100% ready for production, it will save your team a lot of time. |
Re: pic: DeWalt drive base
I'm not a big time drivetrain guy... but can a DeWalt transmission take the torque of two CIM motors? Perhaps you could combine their torque before going in to the transmission?
Or, to avoid the 'losing half the transmission and stripping them out' problem if one shifts and the other doesnt (or other reasons why one might sease) can't you just turn the torque clutch down on the drill to a reasonable number so that in case you start to backdrive the transmission too hard it just slips? I don't know how much torque the clutches go up to in those things before they go direct drive, just a thought. -q |
Re: pic: DeWalt drive base
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Re: pic: DeWalt drive base
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As for the torque clutch, it's typically removed with the CIM configuration, since we remove the first stage of planetary gears. Since this design is keeping those, I'm not sure if he's going to keep the clutch or not. Either way, in a high torque application (like the drive train), you probably wouldn't want to mechanically limit your power unless you really knew what you were doing. dbell - are you planning on keeping the clutches? If so, you should read this: http://www.chiefdelphi.com/media/papers/1680. They kept the clutch in and found that it bent after a couple of matches, causing them to service the transmission frequently. If you aren't going to keep them, how are you going to keep the first ring gear in place? |
Re: pic: DeWalt drive base
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This would be a possibility, but a significant change to my current design. But part of me wants to try using the extra stage. If it works it could be great. Using a chain reduction would a significant amount of weight and space. Quote:
-weight balance of CIMS -if any chain were to break, only one wheel would lose power -does not require an extra gearbox to gear the 2 cims together Quote:
DB |
Re: pic: DeWalt drive base
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