Imperfect 2" Tracking wheels: Is it that major?

[GSBots]

Hey forum,

So I was researching Odom and path and came across the fact that the 2" Omni wheels aren’t a perfect circle. I have seen teams that sand down an insert that offsets the wheel and creates a perfect circle, but my organization doesn’t have enough of the wheels and we can’t order much right now.

I was wondering if the imperfect wheel would drastically affect the tracking, because it doesn’t look like too much of a difference. Would I have to overshoot my path by a little?

Thanks
GS

[74100dEli]

You could figure out how much your robot travels per revolution of the tracking wheel in order to scale it correctly. This will still have some error as the tracking wheels would spin farther for the same distance sometimes due to the variance in diameter. Another option would be to use a larger wheel that is a perfect circle. However, if space or time is a concern you will probably be fine as long as you can deal with an error of around a half inch every time you drive.

[Gigahertz.t]

@bkahl

Because the Omni Wheels were designed with intake applications in mind first, they are designed such that you can clock the rollers along a shaft. The bore is not perfectly clocked to the rollers, intentionally. A fully assembled roller with these wheels can be made with offsetting rollers, helping to smooth out the “gap” you’re worried about.

@bkahl

I use two wheels offset from each other per odom pod so they cover each other’s gaps. They work quite well.
If you can only use one per odom pod, as long as your mount can pivot and is actively pushed to the ground (like using rubber bands/polycarb springs) it shouldn’t create a drastic amount of error. Just keep @74100dEli 's advice in mind and measure how much your error is to compensate for that.

[GSBots]

Thank you @74100dEli and @Gigahertz.t . I saw something on the offset insert but didn’t quite understand, thanks for the resource.

I recently asked my coach and he said we may or may not get two per pod, so if not I will use Eli’s advice on the error.

Yes, also we are going to use Echo’s leafspring polycarb pod no matter if we have two per pod or what, so that should help.

Thank you again.

[Cam91745B]

In the batch that we got some of the wheels were offset for some reason, so we didn’t have to do any cutting on our odom pod.

[Boombatn]

We were also going to do that, however, polycarb is great for making things light this season, and the leafspring was meta back in the old poly rules. The same pod is probably still viable, except you might want to consider rubber bands.