Re: Four wheel drive question
 

You will also need the wheel adapters or make your own. IFI is currently out of stock. I was planning on making four plates and using only one wheel adapter per wheel. The plate would go on the opposite side from the sprocket. There are drawings for wheel adapters on the FIRST CAD library.

Re: Four wheel drive question
 

I saw this FAQ on the IFIrobotics.com Site...

So, we also need the sold out hubs? Does this mean we also need an additional chain OTHER than the one included. Also, the sprockets listed below - those are IN ADDITION to the ones already in the kit (all four of them?), correct?

Sorry if this is a stupid question...

Thanks,
Jason

"What do we need and how do we make a four wheel drive system out of what we have in the kit?

Please check section 3 in the "2005 FIRST Robotics Competition Kit Transmission Manual -RevA" document located at http://www.ifirobotics.com/kitbot.shtml.

You do not need the custom PVC spacer used in the 2 wheel drive configuration and you need to use the 40mm key provided in the kit instead of the 20mm key. You also need additional parts to make the 4 wheel drive configuration. The additional parts you need are:

1. 21 tooth sprocket - Quantity 2. Available from ifirobotics.com
2. 28 tooth sprocket - Quantity 2. Available from ifirobotics.com
3. Skyway wheel hubs - Quantity 2 sets.
4. 10' of chain. Available from ifirobotics.com"

Re: Four wheel drive question
 

Kit Bot Parts

I just found out yesterday that IFI now sells individual sprockets of both kinds for 19.99$

Re: Four wheel drive question
 

Yes, but according to that FAQ it seems that we need 2 of BOTH anyway? Is that true?

Re: Four wheel drive question
 

Well, you should need a total of 4 big sprockets, one for each wheel, and a total of 4 small sprockets, 2 on each geabox output. Then you will put 4 separate chains, one to each wheel. You could run with only 1 sprocket on each output and use one longer chain to turn both wheels on that side but I'd advise against it. You would need to make a semi elaborate idler system to get an adequate (more that 150°) of chain wrap on the drive sprocket.

Re: Four wheel drive question
 

In either case, you need more than just the wheel sprockets. For the 4 chain option (two per transmission) as documented in the kit you need four output sprockets (two per transmission). For the two chain option (one per transmission), you will need at least one idler per side.

Bottom line, for four wheel drive you need more hardware than just two more wheel sprockets. That is why IFI packaged the sprockets together.

-Paul

Re: Four wheel drive question
 

well.... you can forsay create your own 4-wheel drive system you know.... but it does involve lots of build time and 3 weeks have passed now.... to keep it sweet and simple.... 4-wheel drive will not a big issue this year.... i forsee that most teams will be using 2 wheel drive or swerve.... so if it is easier right now use 2- wheel drive for the timeframe we have right now... :D

Re: Four wheel drive question
 

last year we used 4 wheel drive, but it was extremely jumpy on the carpet last year when we were turning with the supplied wheels. We improved our control by using zip ties, but they weren't 100% effective. How have other teams overcome this jerkiness?

Re: Four wheel drive question
 

A TechnoKat robot from a few years ago used a pneumatic "puck" that lifted the front end of the robot when the joysticks were calling for a turn. This was on a tank-tread drivebase rather than a four-wheel drive, but the idea works either way.

If you aren't dead set on the supplied wheels, you have many options, including omniwheels. The 2004 KatsKlaw just used extremely grippy rear tires and enough motor power to make the front wheels slip without too much skipping.

Re: Four wheel drive question
 

What are your thoughts on using the supplied wheels as the power (attached to the motors) with omniwheels as the front wheels? This way there would be no drag on the front tires it would go freely either direction?

Re: Four wheel drive question
 

Indeed, that's exactly how we have built the kitbot for testing purposes this year. Though the omniwheels aren't really designed to be freewheeling, it works. It seems to give a little more of a bumpy ride than I would have expected, but that might just be due to the lightness of the front end of the chassis.