Holy Tether Bots Batman - 7975F worlds reveal(ish)

We were fed up of building the same robot as everyone else, so we decided to look at other designs. Everyone is building narrower chassis for robots, and we noticed that is was possible to slide two 25 wide chassis inside each other to fit inside the size limit. This inspired us to push forwards with a tether-bot design, with both a tray and a DR4B sub robot making up our design.

The 8 motor limit provided us with some challenges, and having to fit everything in such a small area was also a challenge. We designed a split tilter mechanism to allow for the other chassis to slide inside. We also designed a bar to mount the intake rollers to and transfer the power evenly to both rollers from one motor.

Our proof of concept cad:


Motor distribution:

Tray Sub Bot

  • 2m drive 200RPM 3.25" omnis
  • 1m tilter 100RPM 1:7
  • 1m intake rollers 100RPM

DR4B Sub Bot

  • 2m drive 200RPM 3.25" omnis
  • 1m DR4B 100RPM 1:7
  • 1m claw

We had started building the bot, with the tray sub-bot mostly complete and the chassis for the DR4B sub-bot also built. Progress halted about a week ago after not being able to go to worlds due to COVID-19.



We felt that this design would provide more flexibility than other designs in matches, being able to do towers and 8/9 cube stacks, also we could easily score more in autonomous which would be good as well. We also thought that it had good potential in the skills challenge, being able to do two things at once.

More importantly than all that though was that it is just more fun than a boring meta tray, it was more fun to design and build. We also hoped that the robot would be really fun to play with or against as it adds a different dynamic to the game.

Unfortunately, we don’t plan on finishing the robot anymore, but I hope everyone likes the design. Any questions or comments let me know. I should be able to get some more pictures on Monday if there is any particular parts people are interested in.


This is really nicely thought out, great concept.
Would have love to have seen this at Nationals and shame it won’t see the light of day but you never know, the basic concept might have merit next season.


Amazing concept those 1m intakes are really well built. I’m surprised we didn’t see more of that this year, but I guess there just wasn’t a second scoring objective that could use the extra motor. 18t 100rpm is definitely viable you’d probably even be able to move to 24t and you’d intake faster than half the 8m trays out there.

Fitting that clamp on the end of the db4 seems almost impossible. I think you’d probably need to shift to a non-linear lift, but that might prohibit high tower with the height loss.

A little extra torque with the 3.25” wheels is pretty smart you’d probably be able to avoid burnout completely with the bots being so light.

All in really well thought out build. It’s a shame we never got to see it in action. Thanks for sharing!


I’m truly disappointed I’m not going to see a fully working version. I would have loved to see what innovative ways you would have used this design for auton. Your bot looks like some very solid engineering when in to it.


What you could have done with the D4RB would have used a power takeoff as we had on our tether bot that chasis are both 9’ I would assume on our tether bot we chained up our wheels with 3.25’ my question to you is how long where you planning to make a tether. I would also assume you would have needed anti-tips but that is still pretty cool.


Thanks to everyone for their replies!

Thanks Chris. We were hoping to bring part of it to nationals (the tray with some extra motors bolted on) but we decided to go for the reliable bot we had used for most of the season instead, tetherbot next season would be fun if the game/rules allow it.

It would have definitely have been a squish, but we did manage to CAD a solution to go on the end, unfortunately the cool 360 render was made before that was added though. The DR4B sub-bot could be pushed further into the tray sub-bot than shown there as well. Heres a screenshot of the design:
A few things are wrong there as I was just a bit lazy! The motor isn’t meant to be at an angle and instead fits on the inside of the DR4B.

I saw your post and was really impressed with your tetherbots, very nice. Cool idea to combine the use of DR4B and Claw motors and great implementation, that would have helped a lot with lift/claw strength. Combining the tilter and intake roller motors would have also been good as well. We designed it hoping 1 motor would be enough for each mechanism and then if not we would have looked to modify it to make it all work.

We were planning on having a 4 metre tether as this is roughly the width of a field and also half the length of a roll of VEX cable stock. We planned to run the entire tether through a clear PVC hosepipe for protection and then throw in an LED strip as well to make it look cool.

Anti tips on the tray for sure, probably on the DR4B as well, but there is some space for them to add later.


Oh neat we had the same idea I am working on a reveal on my bot which is the same as ur except I made something that does 2 motor roller intake, 1 motor roller intake, 1 motor slip gear tilter and is very similar to urs I was gonna use it for a skills 2 months ago to get a 250-320 skills hopefully but then things stopped working the night before and we didnt want to drive s far anyways w/o a working bot but it was gonna get used for worlds but yall know what happened to that anyways be on the lookout for that reveal


I made one of these early season and i am making a reveal so dw u will get to see a working version


Hey, that’s a fun design! I had a pretty similar thought but the DR4B bot would have an expanding chasis(like the NorCal wallbot) and at the beginning of the match, the traybot would act as a stop but once the traybot drove forward, the DR4B would be free to expand with the power of too many rubber bands.