2363 builds a drivetrain - an instructional video series


#1

Last fall our students came up with the idea of producing a series of instructional videos. These would teach our incoming rookies the skills they would need to be productive robot builders. We never got past shooting footage for an intro before it became clear that we just didn’t have the time to do the job right while preparing for our two fall offseason competitions. So the project got shelved.

Now that competition season is over, we’re dusting off that idea once more. We’ve recently fielded questions about how we build our drivetrain, both at competitions and online. That’s true especially since the adoption of the laser cut gearbox we developed last summer, which won two engineering awards, by a couple of our friend teams. In the past, we’ve presented on our drive train development program at local FRC workshops and summits. While it’s nice to share with the handful of local teams who attend those events, the widespread viewing of our gripper prototyping video showed us that we can leverage Youtube videos to reach a much wider audience.

When we recruit new students, one of our favorite lines is, “Nobody who joins the team knows how to build a robot. We’ll teach you.” As an established team, we go to competitions and see younger teams, some of whom don’t have engineering mentors, struggling to learn lessons we have learned the hard way. We see our role in growing FRC as helping those struggling teams become better more quickly, so they remain inspired, and don’t fold. We see this video series, and the ones which will follow, as a tool which can help educate inexperienced students on our own team as well as other teams across FRC.

So, keep your eyeballs glued to the Triple Helix Youtube channel. We’ve mapped out a shooting schedule for the videos in the West Coast drivetrain series, and footage for the first three have already been shot. We expect to have the entire series posted within the next couple months. Then we’ll move on to another topic specifically aimed at getting rookie teams fielding a competitive bot in their first FRC season.


#2

This great, make sure to add all the videos to a playlist so it’s easy to send the links to teams.


#3

This is great! Just what many teams like mine need to get started. Our mechanical team will be definitely watching these.


#4

Love it!


#5

Great suggestion, thanks!


#6

Forum moderators, is it possible to allow me to edit the first post in this thread? I’d like to include an episode guide, and update it as episodes are released.


#7

Guide to episodes posted so far:

episode 1 - drive train design introduction

episode 2 - measure twice, cut once

episode 3 - bearing hole with the milling machine

episode 4 - axle clearance holes with the drill press


#8

episode 5 - hand drilling the attachment holes


#9

episode 6 - laser cutting gearbox plates


#10

Are these the award winning gearbox plates that I’ve heard so much about?


#11

Yes! In summer and fall 2017, Triple Helix collaborated with two teams on the design, implementation, and testing of a set of drivetrain gearboxes, with Triple Helix leading the design effort. Soon after the 2018 kickoff, we cut copies of these gearboxes for all 3 of our teams using our CNC laser cutter which we also designed and built last year. Both of these teams won technical awards in part for the design work that Triple Helix was involved in. Team 1610 Blackwater Robotics won the Excellence in Engineering Award in Portsmouth and ILITE Team 1885 won the Excellence in Engineering Award in Oxon Hill, MD. We are so glad this happened-- these two awards for our friends also represent a engineering victory for us!


#12

Just for reference, the summer 2017 version of the gearbox plates work with 4" wheels. The 2018 competition bot (Genome Kappa) version of the plates work with 5" wheels. STEP files of both versions can be downloaded from GrabCAD.


#13

episode 7 - Snap ring grooves on hex axles


#14

episode 8 - Snap ring grooves on hex axles, part 2


#15

episode 9 - gearbox spacers using drill jig


#16

Catching up on video editing. Two new videos last night:

episode 10 - making drive chains

episode 11 - installing drive chains


#17

These may be the final two episodes. If we do any more, it will be to answer people’s questions, and maybe do a lessons learned episode.

episode 12 - assembling the gearbox

episode 13 - installing the gearbox

This turned out to be a huge project, which took all summer and fall to complete. It was a terrific training experience for all the rookie students who had a part in building the drive rail. We’ve had quite a few inquiries with questions from teams who have chosen to use this drive train as a summer project of their own. If your team has done so, post up some pictures! We hope to see you out on the field, and want to compete against some teams who have taken our drive train and made it even better.


#18

FTFY.


#19

One of the coolest projects I have been involved with. Makes me feel like we are crystallizing a small part of our institutional knowledge. I want to do much more.


#20

Nate from 2363 mentioned the special motor mount bolts. Yes they are expensive but if they help keep a Cim from getting too hot they are worth it. 2363 came up with the idea and we tried it out as a test for them. We won a Excellence in Engineering award at one of our events because of this same design.

Keep in mind that we are in the district system with smaller events (and less teams per event) which in turn means we often have closely spaced matches with little time for motors to cool down. We did have motors on one side get hotter than the other side. We later found out one of the students had put a 12 tooth Cim gear on one of the motors instead of the 14 tooth that we used on the rest of them. This in turn had the effect of the motors fighting each other on that side. After finding this out we later corrected the problem and and haven’t had a problem with it since. Even if you don’t use pnuematics the air passages still help allow heat to vent and escape.

Like 2363 we also use a “chain in tube” drive system. One thing we do different though is while we use snap rings or shaft collars on the inside of a Hex shaft drive axle like 2363, we use hollow Hex shaft and tap the wheel side of the shaft for 1/4-20 round head hex drive bolts. We’ve had wheels come off because of snap ring damage (a match at the 2015 Virginia regional being an example and the nature of 2016’s field being another.) We use a washer to keep the wheel from sliding over the bolt and use Loc-Tite to keep the bolt from working loose. We had a bolt come loose one time (it hadn’t been tightened all the way) but the back side of the bumper kept it from working all the way out and dropping. (2015 was the last time we used outside snap rings and when the wheel came off we didn’t have bumpers that year and there was nothing to stop the wheel from coming off once the snap ring and spacer came off)