https://grabcad.com/library/team-4926-2018-off-season-drivetrain-gearbox-2
A gearbox designed to reduce the high-speed low torque power of VEX 775Pro motors to the high torque lower speed requirements of a drive train. It uses 4 775Pro motors connected to a gear system that outputs to a 1/2 inch hex shaft for use with pulleys and belts. The current mounting is designed for 2 x 1 square tubing but could be modified for other applications.
Interesting mounting concept. Is there a reason you chose to mount to the top and bottom of the tubing, rather than on the 2" face?
Mostly due to complications with the wheel on the other side. In our layout for a drive train there is a wheel attached to the output shaft. Whatever way we mounted the gearbox there would be something sticking out be it a nut or a bolt head.
Did you consider making a clearance hole on the outside of the driverail for the fastener head to pass through? You could simply slide the bolt through the rail then thread it into the gearbox plate or go all the way through a standoff to the far plate. This would remove any possibility of squishing the tube and would also eliminate any fastener sticking out in the way of the wheel or getting caught in the carpet below the rail. With >.1 inch tubing and 4 bolts in a rectangular pattern, this style of mounting would be more than sufficiently rigid.
All that said, I really like the mounting solution you came up with and it definitely isn’t something I’ve seen before. It’s a really creative solution and I’m starting to question if everyone else has been doing it wrong this whole time :0.
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The main drawback of doing a mounting feature like this would probably be tolerances. Since you’re adding another 2 degrees (bracket + screws) between the mounting points, it can stack up and maybe add +/- .03", which can be killer in some of the tighter areas. In addition, although the angle brackets will help, there is a risk of crushing the tubing and twisting up your frame. It’s certainly workable, but that is another layer of challenge.
On a separate note, I think that this mounting method would work excellently with the Versaframe system. I could imagine a COTS gearbox which would take essentially zero machining (literally just the shaft clearance hole) but with the same lightness and simplicity as the face-mounted WCDs.
There are probably 1000 better ways to do this, but I asked the students to design it this way so that we could use this transmission for the center wheels in a center drop design. By making different angle brackets we could test different center drop values easily.
What are the other solutions for optimizing center drop?
Thanks for the comments everyone.