Sunday, November 10, 2013

Adding Traction to the Arduino Woody Bot Wheels

Woody Bot
After building the Woody Bot, one problem I encountered was the lack of Traction from my homemade plastic wheels. Mainly on smooth flooring but sometimes on carpets as well. So I investigated a couple ways to fix this and decided on this.

Plastic Wheels are Slick
The problem with plastic is that it is slick, and even if you made the wheels out of any other material except maybe foam or rubber, traction is going to be a problem. This isn't a big problem unless you have plans for your robot that involve precision movements. Which describes just about everything you do with a robot ;-). So I decided to add some traction to my wheels. I experimented with a couple of things. I tried foam tape like you use around the edges of a door or Window Air Conditioner to keep the weather out. It worked fine except it got tore up pretty fast. It was really soft and raised the amp draw from the motors a little bit because of the rolling resistance. I tried sandpaper attached using double sided tape. It worked fine except it was little rough on the hard wood floors.
Old Potter Serpentine Belt

Wrap and mark for cutting
Serpentine Belt
So I finally stumbled across something that worked well and looked good in the process. I had an old Serpentine drive belt from an old Plotter that was exactly a 1/2" wide. It was rubber, so I figured it would fit the bill. Plus the horizontal ribbing should give excellent traction. What I did was cut the belt with a pair of side cutters, the wrapped it around the
wheel to get the length I needed. I marked it and cut it off with the Side cutters again. Duplicate this for both wheels.

New Tires for the Bot
Cut with Side Cutters
New Tires
You end up with two flat pieces of belt that we have to attach to the wheels. Essentially you have two tires that need to be mounted on their rims. Digging around on my shelves I stumbled across an old roll of Double Sided Carpet tape from 3m. This stuff is amazing and I have yet to find anything it will not stick to.  I cut a piece a little longer than the belt pieces I made then laid it sticky side up on the table. I aligned the first belt along one edge making sure to keep the tape just inside the edge of the belt. If any Adhesive is showing your going to have a huge Fuzz ball of carpet strands when you run the bot later.

Taping the Tires On
Once you mount both strips to the tape, take and X-acto or Utility
Roll the back half up by hand
Roll the Bot forward
until the two ends meet.
knife and trim around the that you have to belts with the tape stuck to the back side. Peal the paper backing off of one strip and lay it down on the table sticky side up. Place your wheel on top of the tape roughly in the middle. Then slowly wrap the back half up and press on to the wheel keeping the outside edge flush. next move to the front part but instead of lifting it up just roll your bot slowly forward onto the remaining portion until the two ends meet. You now have one new
3M double sided carpet tape
wheel with a home made tire. If you use the 3m Tape your done. If you had to use some cheaper tape, I would recommend putting a couple of drops of Super-Glue on the ends of the tires to help keep them in place.

Completed Tires and Wheels
Other Materials Work Too
You could definitely do this with other materials as well. Any material that has traction but will still wear good will work. Old inner tube material from a bicycle tire would be a good candidate. As would a large rubber band wrap over the wheels. Use your imagination and come up with something that works with the materials you have laying around. 

End Results
First off the results are immediately apparent. no more slipping and sliding while it turns. Repeat-ability has increased dramatically.  So the wheels are tracking true and working in sync again. What was not readily apparent was how much the traction was increased. Before if the bot hi any little object on the floor it would stop and spin the wheels till the program changed and it went somewhere else. With the new tires it will power up and over things like Extension cords and socks on the floor. If the front end gets up on something it will torque it completely off the ground to clear it. Sometimes even flipping over int eh process. Definitely torque to spare now.

So enjoy your bot with its new found traction abilities and keep wasting more time. 

More Woody Bot articles to come.

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