[Ri3D] BOOM DONE. We're not done...

[AllenGregoryIV]

Originally Posted by JohnFogarty

So. We're in our shop today trying to figure out a way to expand the 1/4" Schedule 80 PVC to fit onto the 1/2" hex shaft and it seems to be quite a challenge. How did you do it?

We played around with it too, it's pretty easy if you heat up the 1/2" hex shaft.

We just clamped a 1/2" hex shaft in a vise sticking straight up. Then we just heated it with a heat gun, didn't even need to use a torch. Then just press the 1/2" Schedule 80 PVC on to the hex shaft. We just pressed it by hand, it wasn't easy but it wasn't that difficult.

[JohnFogarty]

Our problem is we have been heating up the PVC. We've decided on a different way to secure the tubing to the hex shaft that will work just as well I think.

[Joe Johnson]

Originally Posted by AllenGregoryIV

We played around with it too, it's pretty easy if you heat up the 1/2" hex shaft.

We just clamped a 1/2" hex shaft in a vise sticking straight up. Then we just heated it with a heat gun, didn't even need to use a torch. Then just press the 1/2" Schedule 80 PVC on to the hex shaft. We just pressed it by hand, it wasn't easy but it wasn't that difficult.

Yes, this is exactly what we did. Heat one end of a small (~6") hex shaft -- the other end in a vice. Get it hot and then just push the PVC tube onto the hot hex shaft.

Worked great for us.

Note. It is the size Schedule 80 that has a hole of a little bigger than 1/2"

That is the beautiful thing about Schedule 80 (rather than Schedule 40 available at Home Depot, Lowes, ...): you can get them in sizes with IDs just a hair bigger than 1/4", 3/8", & 1/2". That makes the perfect for making spacers for 1/4", 3/8", & 1/2" shafts.

FWIW.

Dr. Joe

[Joe Johnson]

Originally Posted by ekapalka

Please excuse my lack of intelligence, but aside from using the Green Cord to spare your motors, what stopped you from simply using AndyMark gearboxes with that or a similar reduction (like a pair of 8.75:1 toughboxes with reduces by 2:1 on the output)? Is there some other mechanical advantage to using the gigantic sprockets? Thanks!

I was scared of the impact loads we were going to put into the arm. So, I worried about going with a "live axle" where we transmit the torque to the arm via a hex shaft (or worse, a 1/2" round with a single key).

So... ...we went with a larget sprocket on the last stage because then we get to transfer the torque to the arm out at a nice (6" in our case) radius. Also, we have all those teeth engaged rather than just a tooth or two.

We went with the green cord on the first stage because it is springy and it can slip. This lets the energy in the armatures go someplace other than into breaking gear teeth and/or snapping chain.

COULD we make a Toughbox work? Maybe yes. But, we made the thing we had work so, I have an existence proof the system with chain and green cord working. I like that the loads are lower and the energy has someplace to go. So... ...unless I had a compelling reason to go another way, I wouldn't change.

Dr. Joe

[Team1339]

We are going to be using the 7 segment display and the rangefinder and we wanted to know how you mounted them.

Thank you!

[nxtmonkeys]

My team is in its rookie year, and we were sooo glad that there were RI3D teams such as Boom Done this year. Without them, we would probably not be anywhere close to where we are now with our bot. Thanks!


We used #35 chain on our sprockets, so we don't have to worry about the chain breaking at all.

[discobrisco]

Originally Posted by Joe Johnson

Also, the mecanum wheels were not my favorite choice. And I think I was right. They are scaring me. A number of the small wheels on the 6" mecanum wheels are pretty wobbly already and they don't seem to roll well. Have others had issues with the Vexpro mecanums? do tell...





Dr. Joe.

I was looking at this and I thought id add we had to switch to andymark mecanums because in one of our rounds we literally broke off half of our rollers on one of the vex. Andymark haven't had any problems yet. Also, is it legal to have 4 mini cims with 2 bags? Rules seemed to make it seem like it was up to 4 total instead of each.

[Whippet]

Originally Posted by discobrisco

Rules seemed to make it seem like it was up to 4 total instead of each.

The FRC Manual states any combination of up to four VEX BAG and/or mini-CIM motors may be used, per R29. This means that you can have two mini-CIMs and two BAGs, three mini-CIMs and one BAG, four mini-CIMS and no BAGS, etc. Your stated configuration would be illegal because it totals greater than four of the stated motors.