Since we are limited to 8 V5 motors, 2 motor drives will probably be common. Would there be any significant advantage to having the front and back wheels chained vs not having them changed and simply letting one side rotate independently (assuming that the driven motors are traction wheels and the free wheels are omni wheels)?
Yes, there are some important differences:
- The chain will have more friction, causing some power losses.
- Driving both wheels (chain) means you can push off of both wheels, creating greater force and power limits based on the wheels gripping the surface(s).
- Driving both wheels (chain) means you can lose contact with some and still push, which is handy when climbing over obstacles.
- Chains are more vulnerable to being broken, which can be a reason to direct drive a wheel and then chain it forward to the other wheel so you can still drive something if the chain breaks.
The wheel issue is really a separate one as you could use all omniwheels or two omni and two traction either way. That will change the axis around which the robot rotates, how easily it can be pushed sideways, how well it grips the floor, etc.
also if you are only driving with front or back wheels (lets say front wheels in this case) instead of all 4 wheels, your center of turning will be the point between the 2 front wheels instead of the dead center of all 4 wheels (center of the robot), which can create inconsistencies in turning and your back end will sweep around while doing a point turn, requiring more space.
also, you will want all wheels to be powered to be able to successfully climb platforms, so i would suggest a 6 wheel drive with omnis on the corners and traction in the center with chain wrapped around them and the tracttion wheels directly powered by the motor, so you can still drive if the chain breaks and you will still be able to complete perfect point turns and not be able to be pushed side to side and fall off the platform. if you use bigger sprockets, it reduces the friction due to the chain and it lowers power loss as well as the chance of it breaking. I am also pretty sure you can use white lithium grease, which can help
Quick question: Would it be better to do two traction two omni or just four omni?
I always say to use all omni, but others might say that traction wheels make it harder to be pushed off the platform. They do make it harder, but not even close to impossible. In my opinion, the traction wheels make turning slower and in general strain the motors more, so sacrificing speed for a small amount of extra grip isn’t worth it. If they provided more grip, I might’ve said something different.
One thing I noticed last year though about using sprockets on your drive is that they’ll have a lot of play and wear out really easily. And with more motor power in v5, expect to be changing your sprockets extremely often if you want the best results. For some reason doesn’t sell sprockets with high strength inserts, and I really wish they did.
This isnt the case if you use the following setup on each side
+
|
+
where + = omni wheel and | = traction wheel
thus, you can use a 6 wheel drive and chain them all together
since the traction wheels are in the center, they are perpendicular to the center of the turning point of the robot (pun not intended)
thus, the traction wheels just spin in a cricle around that point while turning and there is no extra friction because the ones at the corners, that do slide across the ground are omni wheels
thus, this is extremely advantageous and all the help you can get f to prevent being pushed off the platforms is valuable, which the traction wheels will do, compared to just a 4 wheel omni drive, which can easily be pushed sideways
being able to be pushed sideways can not only cost you the center platform, but people can push you a little and make you miss a shot or make you have to line up again to score a cap after being nudged slightly, just the way a lot of teams pushed other robots sideways from their driver stacking station to prevent them from stacking in In The Zone
One thing that you can do to strengthen your sprockets is adding the lock bars. If the sprocket doesn’t have holes to screw these in to, you can drill them. Since they’re metal, they won’t wear out all season guaranteed.
Yeah, that you can do, but I also remember reading somehwere that vex is planning on bringing out the insert compatible sprockets sometime this year.
The best way to fight getting pushed off is to make certain you can turn on the platform and fight back, as well as use some sort of brake to add friction while being pushed
Drop-Center drive is the absolute best if you are only planning to power two wheels. It really only works best if you have 6 wheels in total on the base. But since only two wheels are lowered, getting up on the park will be much harder, probably impossible…
best drive: tank treads
You know your third sentence explains why the first is untrue, right? Drop-center drive may be the best with two powered wheels, but not always, so it certainly isn’t the absolute best.
Lol relax, they do different things. Drop centers are nice for games where you don’t need to climb anything, chained drives are better for higher traction, lower speed applications. They both have their places.
+100
Drop center was amazing in the case for Starstruck since there weren’t any real instructions to climb over and the centralized turning was really beneficial, but for ITZ, a direct drive or chained drive was the best since there could be the possibility to get stuck on the 10pt bar.
Thanks for the up vote 
Drop center would have worked really well for NBN too.
Definitely