Quote:
Originally Posted by Mike Martus
We have used the dewalts from the very moment Dr. Joe invented them.
Some comments:
To get the press fit correct you MUST wire EDM to exacting size.
We use a fixture to press on to the shaft of the motor for correct alignment and distance.
We created a fixture to control the sizes of the housings (we do no sand as per instructions) using a mill.
We do run 4 cims with 4 shifters that are in coordination....no issues
I believe the NBD System is still one of the easiest, lowest cost, reliable drive transmissions that all teams can make.
We have yet to have a transmission failure.
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I'd like to echo everything Dr. Joe said, especially about the EDM, and the fixtures.
Carbide will not work well to machine the sun gears. They are some ridiculously hard powdered metal. If you want to use these transmissions, you really must find someone to EDM them for you. It's quick, pretty simple, and most shops will be happy to do it for you.
There are two distinct variables that affect the CIM mate to the gearbox. One is the final length on the plastic housing, and the other is the press fit of the sun onto the CIM. Both of these will need to be quite accurate, or else you'll need to modify one or the other. We ended up doing this, but it's really not a good idea.
If you do choose to shift (not at all necessary, these gearboxes are amazing just locked into second gear!), you'll need to make absolutely certain that your shift ring slips well, and there are no binds. You'll also need a longer horn to get adequate torque- I recommend buying a new, longer one, and not relying on the adjustable ones that come with the servos. They slip.
Ultimately, the Dewalts, as Dr. Joe has said, really are the best imaginable gearbox that can be adopted for FIRST. They mate to everything, they're super light, easy to mount, have awesome three speed capability built in, and are tough as nails, even if you abuse them. However, the challenge is in making them. If you are willing to invest the planning time and schedule dedication to get everything fabricated and ordered for them, they will give you few hassles, and really make the design of the rest of the robot easier.
However, if you hack your way through the process, you'll wind up with a hacked piece of junk. Imagine that... If you put the proper effort into the Dewalts, they will return it a hundred-fold.