pic: FTC Bearing and Axle upgrade



Half way through the season our brass FTC bearings worn out which damaged our gears, “expensive”. Our axels also would bend. We came up with this HDPE block that would support roller bearings and a larger axle (size of motor axle). It stronger, rolls much better and will last a lot longer.

This looks like a great idea!

A very good solution!

We’ve found that the Tetrix axles to just be too wimpy to use for a drivetrain. Though we never tried a motor-diameter shaft.

This past season, we just went with AndyMark 4" HiGrips, live axle on ball bearings and 0.5" steel axles. Probably way overkill, but that drivetrain is pretty much indestructible.

https://drive.google.com/file/d/0B8vSHm05FxGTdnk0NzRNeXlONVk/edit?usp=sharing

https://drive.google.com/file/d/0B8vSHm05FxGTVWZnMzRqTk93SWc/edit?usp=sharing

Though I daresay yours is more compact. What does the rest of your drivetrain look like?

We use four pairs of 4 in Tetrix wheels and 2 pairs of 4 in Omni wheels which all wheels are driven for our drive system (six wheel drive).

Our trouble with the bearings was our arm to move the blocks, we are really geared down and wore out the bearings moving the blocks back and fourth. We are hoping this new design will help us next year.

Very nice… I’m going to bookmark this so I can show it to my teams this fall.

Can someone explain why Tetrix, with how much it costs, requires this level of tweaking to get an effective drivetrain?

It doesn’t necessarily require it, there are just always better ways to do stuff. Personally, I would use a little tetrix components as possible if I was a team myself, just like in FRC teams make sheet metal robots instead of using the KOP. The only difference is that in FTC almost everyone uses the KOP and it includes some of the game specific construction as well, partially stemming from the fact that you used to be strictly limited to using tetrix parts and another small list of parts, which has been loosened. As for the cost, I can’t explain that.

I feel it would be much easier to do an H frame out of 1/16" alu square tubing and this way the chassis would be really stiff and it would be a lot easier to install a drive train.

It didn’t require it until robots started getting extremely heavy.

When the unlimited raw materials rules started taking hold, robots started getting heavier and heavier in FTC. My senior season our robot weighed 68 pounds. We still built our base frame out of Tetrix back then. Now I know for a fact 3864 has gone away from using anything Tetrix in the drive base with the exception of the wheels. Tetrix parts just were not made to handle the weight that the FTC teams put on them now a days.

See, this is what gets me… I’ve NEVER seen someone say “Tetrix is great we use it every chance we get”

Which begs the question, why are we going to lengths to use the Tetrix parts? It seems you are using 4" wheels already. I know someone used the AM kit wheels in FTC earlier in this thread. Why not utilize FRC levels of construction and forego the 1/4" axles entirely? 3/8" hex is cheaper than most Tetrix components… Heck, with the weight some of these bots are getting (I think Minotaur was 70lbs+ in 2013) it might make sense…

Joe, I guess what I’m asking is, why not just go full blown parallel plate drive with 3/8" axles. Simple chain 1:1 from the Tetrix motors. Wouldn’t it be easier than working inside the constraints of the Tetrix parts?

We are from Michigan where our students are junior high school students and with Tetrix they can fully assemble a robot with out our help. Its great to set back and watch them do everything. With FRC we have machine most of it.