We did butterfly last year https://youtu.be/iTNBnCr1Fgs
There were a few examples posted here on CD (back when it was actually possible to find such things on this site) from 2015 (various) and 2010 (frc148 / frc217). The best I can do is describe one I saw after we built ours which is what I would do if I had to build an H-Drive again. There a few different approaches to suspensions, but this is the simplest one I’ve seen.
Basically, keep the frame in your original post the same, but remove the two 8020 bars that go down the center (attached to the center wheel). Then, add an hinged arm (I’d use 1"x2" rectangular tubing) that goes from the left or right side of the chassis to the center (not all the way across) and mount the center wheel and gearbox to it such that it can move up and down to some extent. Then, you can either add a short gas spring to apply a constant down pressure (this may require trying springs with different amounts of force) or use a pneumatic cylinder and just actuate it when you want to strafe.
The goal is to apply enough down force to the center wheel (at least when strafing is desired) such that it maintains good traction to the ground, but not too much that it lifts the other wheels completely off the ground (and, thus, the robot off-balance).
that was just an example. do you think it’s possible to modify kitbot to accomplish the same thing? (thanks for the detailed instructions by the way, much appreciated)
Our team is planning on building a 8 wheel drive using 6" pneumatic wheels
Probably a close to stock kitbot. No need to get too fancy.
any reason to 8 wheel vs 6 wheel?
I don’t see why not, basically just take the standard kitbot and don’t put wheels in the two center positions (so you’d only be driving the sprockets, rather than the wheel and the sprockets), and swap the other 4 wheels with omni wheels. Adding the strafe wheel would be basically the same process as what I described above.
Now that said, just because you CAN do this, doesn’t mean I would for this years game. I think people are underestimating how much defense is going to be played this year, and H-drives are going to get pushed around a LOT. IMO, the ideal drivetrain this year is clearly a swerve/crab, but if you don’t have the technical experience for it (many teams, including mine, do not), you’re probably better off with a standard tank drive (IE what comes in the Kit) for most of the objectives this year.
the only benefit i see for 8 over 6 is while climbing it leaves you with more wheel surface to use
Another benefits is that 8 wheel is more stable than 6 wheel for a robot with a fully extended arm or elevator placing on the top row of the rocket.
I think just speeding off of the second level is doable as long as your robot is very sturdy with no loose parts as this jump will give a pretty major shock to the entire robot.
Last I met with the team, I believe we were looking at building a west coast style drive train with 6" pneumatic tires. This would give the bot some bounce once it jumped off the second step, while also giving the robot some lift; not leaving it so close to the ground.
Thanks. That’s a great idea especially for this challenge.
I see the defense of the game to be an important role, but a defending blue robot can only do so much to the maximum 3 red robots trying to score. I can see targeting as an option for a defender if there is only one mecanum driver, but if 2 or 3 red robots are all using mechs, then defenders would have a harder time trying to block and push all the extremely mobile mech drivers. The only time I would see defenders pushing all the robots is if they are on the same side of each other.
Our team has decided that using mechs would be advantageous, at least for our sakes due to the fact that we’ve had moderate success with mechs in the past since our main drive team has left last year and that we’ve had to train a new drive team. The pros of the mech wheels such as mobility or the ability to strafe outweigh the cons like less power and traction in our case.
You can if you have the time and knowledge do something like octocanum.
This is a drive option where when you need mec wheels you can activate them, and when you don’t you can keep standard traction wheels engaged.
Vex Pro sells a kit for this.
^^We made the same mistake last year for power up. If you use h-drive, which is a decent option, make sure to get the pressure and traction on the H-wheel right.
Swerve is gonna kill for the 3rd year in a row. Mechanum/h drive is a viable option for low level competition, but come worlds, any robot with those drive trains will have trouble placing in the rockets while dealing with defense. We’re doing a drop down tank drive again, for the 6th year, mostly bc we’re good at it and we don’t want to risk building our first swerve drive in build season.
My team is planning on doing a 4 wheel drive with 8" pneumatic wheels. Do you guys think 4 wheels would cut it? It worked for us in 2016 but I’m not sure if we should do 6 wheels instead.
We may be using a tank drive with 2 tuffbox minis. Besides that, I really have no clue.
You could run into some problems when you are trying to turn. You will want to to do some tests to ensure this isn’t a problem.
Regarding mecanum and defense… Do you think any drivetrain is going to hold you in alignment while being hammered? I think the answer is no. Recovering from the hit may be quicker with swerve and mecanum and other side to side drives.