Does a 6 wheel drive with omni wheels on the outside and regular 4" wheels (triangle tread) on the inside work? The omni wheels are a little bigger than regular wheels, but does the sinking into the tile compensate for this and allow the middle wheels to have traction? Does this work if high traction wheels are used in the middle? Would it be advisable to use all omni wheels, or does the sideways drift and easiness to push around make this configuration not useful?
On a side note, which way do the wheels go? (triangle pointing forward or backward?)
6 wheel drive with either traction or regular wheels in between 2 omnis was the preferred drivetrain for a lot of teams in Gateway and some in Sack Attack as well. Your center of turning will be along the line between your 2 middle wheels and the omnis on the outside negate any friction while maintaining a full length wheel base.
The omnis are slightly larger and the wheels sinking into the foam tiles doesn’t completely compensate for this, although it is still okay if you don’t drop your center wheels slightly. You can do this with pillow blocks and washers to push the axle of your center wheels a couple millimeters down.
All omni wheels do end up being extremely easy to push while traction wheels in the center, if the wheels are dropped slightly and especially if there is anti-static spray on the fields, are nearly impossible to push without a specially torqued up drivetrain, extra drive motors or a transmission.
Arrgh… SweetMochi beat me to the post XD
Anyway:
I don’t think there is a specific way the High Traction Tread are supposed to face.
High Traction Tires work well too:http://www.vexrobotics.com/vex/products/accessories/motion/276-1489.html
Thank you for the suggestion about the pillow bearings. The difference between the 2 wheels is .053" radius.
We have also found that if you put a high traction tire on a 30-tooth high strength sprocket it makes a traction wheel the same size or even a tiny bit larger than the omni wheels. This allows for weight on the center wheel without mounting it at a different height.
There is another way to do it that is a little more work, but does not require extra chassis parts.
Wait I’m not sure that answers the same question? Or am I misunderstanding you?
If I understand correctly Rick is just saying to remember that if you work smarter you won’t have to add an extra pair of wheels.
This year though, you pretty much have to either raise the chassis, or have 6 wheels. Otherwise, crossing the bump will likely be a problem.
nope
our grade 9 team has a standard 4 wheels chassis 4 motors 1.6:1 internal
goes over just fine…
can it be balanced on the bump with its wheels off the ground?
If you are looking for a slightly dropped center traction wheel, you could give NARdrive a try (credit must be given to the college team NAR for this one).
Essentially what you do is take a 30 tooth sprocket, and wrap a closed loop of chain around it. Then around this chain, put on a high traction tire. (It will be tight, but will eventually squeeze on).
This creates a slightly larger wheel than an omni wheel, and further facilitates turning. Additionally, being larger, it digs into the foam tiles a bit more, and gives a robot more traction.
We tested this out a fair bit, and liked it, however it can leave you a tippy if you have a light robot.
This is another example why you can’t name stuff like “NZ” bot, because I’ve see seen several teams in the past few years, as well as myself, use this method.
Thanks – wrong link. Try this one.
that makes a lot more sense now
Well, you probably can’t straddle the bump that way, and you might get stuck if you get pushed. Of course, if you do get stuck, you could just shake your arm or something, but it’s still better to design the bot in a way that keeps metal from touching the bump. Do you rely in momentum to slide over the bump or something?
lol no
i guess i can reveal our “trick”
the bump didnt straddle on metal…
it was straddling on a chain sprocket
so when we drove, the robot would drive forward as if the wheels were on the ground
precision engineering at its finest
im proud of our grade 9’s :')
Speaking of wheels I would love those 200mm omni wheels from IQ to be usable.
I am not sure why we are not allowed to use non electrical parts from IQ. You would think they would want to spice things up competition wise by adding new parts even if some are sub-par to what we already have.
Also if I remember right when they announced IQ it was said that the parts lined up perfectly with VEX parts and even used the same axles and we would be happy we could use IQ parts or something along those lines.
The other reason you would think so is VEX would have more sales if they opened up the IQ parts to VRC even if it was just the gears, sprockets, belts, tank tread, wheels, etc. I’m not sure how well allowing the snap together parts would go over but it would be nice to use the larger pieces as bearings.
But yeah money wise you think they would open it up to VRC teams to use…
Unless there is a good reason not to allow us to use those parts.
Just my thoughts…
If I were to guess I’d think they’re going to open it up next year after the parts have had some time to be tested out. And while I do agree with you for the betterment of robotics, we just don’t have the budget to buy anything else for this year so doesn’t really affect me much 
You might as well just put a wheel there lol. It doesn’t have to touch the ground during normal driving, only while crossing the bump.