I wanted to get some feedback/opinions on a drivetrain I’ve been designing. With the rise of teams successfully using simple ctc chain runs (with that added bonus stretch), I thought it might be cool to design one of these drivetrains for myself. I’ve been trying to challenge myself to speed up the process of manufacturing, especially on the drivetrain. For next season our team is planning on routing a standard 1" hole pattern into a ton of tube in the first couple days of build season (and in the weeks leading up to season for training/practice bot) to reduce manufacturing time once the robot is designed, so I thought I might take advantage of that pre-machined stock to speed things up a bit. The bearing blocks are routed from 1/4" aluminum, and are designed such that the wheel drop and chain stretch offsets are accounted for in the part (hole is not centered), keeping the hole pattern the standard 1" tube hole pattern we like to use everywhere. By using a few templates or just quickly drilling/drill pressing in oversized clearance holes for the shaft, these bearing blocks will bolt in to the closest holes that haven’t been drilled out and make life super easy for assembly, leaving all the hard alignment work to those bearing blocks. The next challenge was gearbox holes, and assuming I don’t do custom gearboxes next year (in which case I’ll match the pre-existing hole pattern) I’ll either mill out those two holes or use a template and drill press carefully. Bellypan is lasercut 6mm Baltic Birch, and all of the tubes are 1/8 6061 Aluminum.
Screenshots/STEP file can be found here:
I’d love to get some feedback on this type of drivetrain as we have never really run it before (kinda did in 2016 but lots of different stuff going on). Obviously this method of speeding things up really only works for my team (unless yours has the same shop, resources, etc.), however I think lots of the concepts could be used by other teams looking to speed up their drivetrain process, make it more adjustable on the fly, or just make life easier in the shop while sending plates out to sponsors.
For no reason other than the fact that I was bored, I designed this drivetrain using Onshape variables and some backend Featurescript. Essentially, that means it can be modified to suit any game’s frame perimeter rules. You can edit these variables on the left, on top of the features list in the drivetrain frame tab. None of the assembly beyond whats referencing the frame will change (for example, changing wheel size will move the bearing block over, but it won’t replace the 4" default wheel in there) (yet).
Here are the variables and what they do:
#Length: adjusts the overall length of the frame
#Width adjusts the overall width of the frame
#drop adjusts the wheel drop
#Wheel_Size adjusts the spacing of the wheels so they fit (buggy, yes I know I’m working on it)
#Gearbox adjusts the spacing of the gearbox mounting holes
#L_Length adjusts the size of the L Brackets
#Chain_offset adjusts how much added spacing there is from the ctc of the chain runs. Default should be .02, a number I got from other posts on chief and discussions with designers more experienced than I am
#GB_Slot_Width sets the width of the gearbox cutouts in the bellypan
#GB_Slot_Length sets the length of the gearbox cutouts in the bellypan
Thanks in advance for all of your feedback, I’m looking forward to seeing what everybody thinks!
Special thanks to Anand, Chak, and that mechanical crew for putting up with my stupid questions, as well as Michael Bick (1836 alum) for inspiration from his 2016 drivetrain and Adam Heard from 973 for pushing me and my team to get faster and better at everything we do (also answering my stupid questions yesterday).