Finding Wheels For Your Robot
When I first started building robots, I was amazed at the amount of time I spent worrying about the wheels for my creations. It is sometimes pretty exasperating trying to find something that will work. Here are some ideas for wheels - some you can buy, some you can make, and some you can rob from toys. If you want to get a bit more technical (and use serious shop tools!) you can make sophisticated wheels from plexiglas and brass. See bell-217.bellevue.edu/robots/wheels/wheels.html for a nice way to make more advanced wheels. However, if simplicity is something you desire, then scan through the following for some ideas on how to solve that silly wheel problem!
The tail draggin' part of these wheels is from a craft store. Purchase a
wooden ball (a dozen for a dollar) and put some 1/4" dowel in it. The wheels on this
'bot are from an old Radio Shack car that cost $5.00 new (on sale) and lasted about two
hours before it died.
Same robot as the one above this, but a different angle. The wheels were
hot glued onto the servo horn. The center of the wheels was drilled out so a screwdriver
could tighten the servo horn set screw.
These are a couple of implementations of the DuBro model aircraft tire
installation. The first picture shows the wheel held on with the center set screw (I found
a couple that were long enough in an old junk box), the second uses small metal screws
through the servo horn. The second example has enlarged holes through the center
(1/4") so a screwdriver can access the horn set screws.
Another DuBro setup with 4x32 machine screws holding the DuBro to the
servo horn. Note the 1/4" hole that was drilled in the center to access the servo
Here's a tail wheel setup that is really nice (OBTW: I got this idea while
wandering around the hobby shop near me. I got all excited and came back home with a bag
of the wheels, jumped out on the web to tell someone and stumbled onto Don Roy's site .. He was already using them on his
robots. In fact, this is one of Don Roy's robots called 1stBot. Jump over to his web page
and check it out!). It is made with a .060 wire size tail wheel from a model airplane.
This setup uses a 1" tail wheel and some collars to make the whole effect. You can
get the tail wheel from a model shop (be sure to get some extra axle collars - much nicer
than soldering washers onto the axle to hold the wheel on).
To align the tail wheel properly, bend it to about a 15 degree angle and
then file or cut the extra that is sticking out with a Dremel tool. It will then track the
way it is supposed to.
Two different approaches using the same gearbox. The wheels on the first
were from an old car and they were pressed onto the dual motor gear box (available from
the Robot Store). You can see the shrink tubing
that was used to get a tight fit between the wheel and the axle. Note the diaper (made
from an old piece of stiff paper) on the first example. These gear boxes will suck up all
the junk in the world .. so if you use them, be sure to cover them up with something -
else you will be disassembling them all the time to unwrap dust bunnies from the axles!
The second picture shows a bulldozer base. It was also obtained from the Robot Store and
it included the dual motor gearbox.
Now for a more novel approach. Go to a craft store and buy some wooden
wheels! They are really cheap (about 50 cents) and they can be painted, drilled, glued,
etc. These have been painted silver and hot glued onto the servo horn.
This is a pretty small robot with 1 3/8" wheels. The wheels are
actually model 'vintage airplane' wheels purchased at a hobby store. The servos are
miniature ones, and the wheels are tied to the horns with 2 x 56 machine screws (available
from Radio Shack!). The tail of this robot is another one of those wooden balls that I
mentioned earlier. This one is a 1/2 incher.
And one of my favorites. This wheel is small (it is also about 1
3/8") and it is made by super gluing two 3 1/2" diskette centers together, then
super gluing a couple of rubber bands (one to fill the center and one to use as the
'tread') onto it. You can also make a nice pulley out of this approach (just don't put the
final rubber band on). You will need to clean the center hole and then drill mounting
holes through the wheel itself. This will secure the wheel together and mount it to the
servo horn (assuming you are using a servo).
Here is a very nice 2 3/8" wheel that can be made with no machine tools (other than a drill - and then only if you want a set screw). First, go to the hardware store and get a 1/4" ID bronze hip flange (take the first picture with you and you'll find them). If you want, drill and tap one end of the flange so it will take a grub screw (set screw) and you can really tighten it down over your motor shaft. If your motor shaft is not 1/4" then get the right size flange! Next, get some large washers (called Fender Washers) that fit loosely over the flange, but are still stopped by the bronze ring on one side of the flange. Get two types of washers, two big ones (2") and one just a bit smaller (1 1/2"). Make a sandwich out of them, then solder them together at the center using lots of flux. The total cost for this method is pretty small (no more than a couple of dollars per wheel) and you have some really professional looking wheels to use on your robot!. I used 6x32 grub screws for this wheel and it works just fine on a 1/4" shaft. If you have to buy a tap, you can get a cheap one for a dollar or two. The O Ring was purchased from the plumbing department of the same store I bought the washers and bushings from. I used silver solder (actually, I used the cheaper leadless solder which has some silver in it), a propane torch, and a little patience/clean up and it worked very well.
This wheel is made from 1/8" plywood (actually, the really cheap 3 ply stuff, but it would probably be better to use 5 ply model aircraft plywood). You can get a hole cutter for about $8 in a hardware store. The one in the above picture is by Great Neck and is advertised as a '7 in 1 Hole Saw'. Those who know tools, know that Great Neck is about as cheap as you can get, but this tool works just fine for making wheels up to about 2 3/4" in diameter - in fact, a higher cost hole cutter might not give you the taper you need on the edge of the wheel blank (read on). You can use a drill or a drill press to buzz into the plywood and what you get is a blank wheel that has a really nice edge that tapers to one side. Make two of them, sand them a little to make them pretty, and sandwich them together with the tapers going inwards. That makes a groove for your O Ring. You can glue them, bolt them at the center, and let the glue dry (use Elmer's Wood glue or similar). The wheel can then be painted or decorated, just like on Home and Garden TV!
You can make a wheel out of about anything that is round. I'll give you a hint about this wheel. It cost me 50 cents (US) plus the cost of the O Ring!