Wheel Construction Tips & Tricks (not designs)

[Mac]

Hey guys,

Am currently awaiting items ordered and thought it might be nice to have a thread for construction tricks we've learned along the way. Please do NOT post wheel designs, claims, or flames.

Here's a few:

- Auto body filler (bondo, etc.) works well for odd shaped parts. It can be easily worked for a few minutes before it sets hard, then can be sanded/drilled as needed - or can be used to make several identical parts from a mold (and can be used to make the mold itself). It's also designed for minimum shrinkage, and can be used to fill holes and gouges and other boo-boos.

- When using a mold, make sure all surfaces are very smooth, and apply several coats of heavy duty wax (such as carnauba floor wax) or a commercial "parting film" to ensure release of the part. You can also drill a small hole in the mold (or several if it's large) for blowing into and aiding release (these can be covered with tape etc. before molding). All sides of a mold should have a slight outward slope so it is physically possible to release the part.

- "Stick on" auto wheel weights are handy for adding weight (mass) or balancing wheels. The ones I have are 1/4 oz and come in sticks of 12, which can either be separated at the creases or bent to fit contours. Be aware they can fly off of outer surfaces at high speed though. And they're lead, so wash after handling.

- Plumber's tape can be used for clamps, brackets, or small linkage if it's heavy enough. It's metal, comes in rolls, has holes every 1/2 inch or so and is designed to hang pipes under houses. It's available in various widths and thicknesses, although sometimes a store only carries a single type so you may have to shop around.

- To make a wheel perfectly round, first mount it on it's axle or shaft. Then firmly attach your tool (sabre saw, grinder, file, etc.) to the wheel's mounting frame where it will cut the outer edge. Just turn the wheel by hand and you have a crude lathe (you can actually cut a wheel out this way to start with). As always, be careful with cutting or power tools.

- Sealed bearings actually create a noticeable drag because of the seals rubbing. Try to find "shielded" bearings instead, they have a dust shield that does not quite touch the inner bearing race, yet does a good job of keeping the bearing clean for most indoor applications. You might also want to remove the grease from bearings and use a light oil instead.

[ken_behrendt]

Mac...

I have never even considered trying to mold the parts that I might use in a model wheel. I generally cut them from stock sheets, rods, or tubes of various materials.

I have, however, discovered a way of making interesting "tinker toy" like structures which can serve as a kind of open frame drum to hold one's weighted levers. Basically, I just take 1/2" spruce wood dowels or rods, cut them to the appropriate lengths, and then, after lightly sanding the surfaces that will make contact, use epoxy cement to attach them to each other. I once used this technique to fabricate a hollow wooden drum that was 4 feet in diameter. Its axle was just a larger diameter cylindrical piece of wood with long screws inserted into the ends to serve as pivots that would rest on open bearing plates. It was incredibly strong and I could mount weight up to 2 lbs each inside of it without the danger of any of the epoxy joints breaking loose.

Each of us, eventually, finds the construction techniques and materials with which we are most comfortable working with.


ken

[Mac]

Hey Ken,

Each of us, eventually, finds the construction techniques and materials with which we are most comfortable working with.

Agreed, but I enjoy learning new and/or different methods and thought others might as well (especially beginners). Your "giant tinkertoy" approach is a good example.

I mostly work with models under 30", and my current test hub is the bearings and rotor from a junked ceiling fan. It's a bit heavier than I really need for this size, but it's smooth and well balanced (not to mention cheap). ;)

Mac

[rlortie]

The Bondo or body filler is a good one, but I found a new type!

It does not use a hardener, UV or sunlight is the activator. You can work with it right straight from the can and take as long as you like to mold it. Providing you do it in the shop or in the shade. There is no premixing required.

When ready to let it harden, simply set it out in the sun. It will set up as fast as the earlier types requiring the hardener mixing.

Works great! I used it to fill a dent in the roof of my pickup, primed hit with a little filler, sanded and primed again and finished with Acrylic Lacquer. Saved myself a $1,200.00 Body shop bill.

Your local Nappa auto store is a good place to find reasonable priced self- aligning bearings. I use the 3/4" and 1" ID, these can be face bolted using common carriage bolts. I find 3/4" black pipe and flanges convenient for hubs and axles. A 3/4" shaft can slip through the pipe and with a little dressing a 1" ID bearing can be friction fitted to the OD.

Recently needed a 3/8" ID bearing that would fit in a Wal-Mart 2-1/2 pound exercise weight. Went searching through my goodies and discovered that those little doughnut magnets sold by Radio shack were just the ticket. They have a 3/8" ID and an OD that will fit the weight. Make for a great ceramic bearing! and besides if some one asks me if my design uses magnets I can reply yes it does!

More to follow

Ralph

[KAS]

Here's a tip on weights.

When I first started constructing, I had weights made which proved expensive. Then My son bought a multigym system and gave me 6 x 0.5kilo weights (dumbell type) which he did'nt need.
At 6" diam x 1" thick, these were just what I needed. I subsequently bought 6 more and use them all the time.

They are relatively cheap and can be bought from any sports store.



Kas

[ken_behrendt]

For weights, I once tried using washers. No, not the small ones used with regular sized bolts. But, rather, the really large ones that are used with the bolts that attach fire escapes to the sides of buildings!

I found that a lot of hardware stores in urban areas carry these oversized washers. They are about 3 inches in diameter and have a 3/4" hole in the center. I would take a stack of about six of them and slide them onto a section of a wooden mop handle which they fit perfectly onto. They could then be either glued onto the mop handle piece or a cotter pin made from a piece of heavy wire could be placed into holes drilled in the mop handle piece to hold everything together. I found that the resulting weights had a mass of about 1.5 lbs.

Finding small (i.e., 1 to 5 lb) weights for one's model wheels can be a headache. The washer approach is nice because the one I used were galvanized and, thus, resistant to the corrosion that can take place when handling bare metal pieces with sweaty hands.


ken

[rlortie]

While doing research on sprockets and chains I ran into this free download for viewing Cad files. Covers a number of file application types.

http://www.infograph.com/products/dwgviewer/

Ralph

[Mac]

I often like to do a quick sketch of an idea while it's still fresh, but that usually takes a lot of erasing (or completely starting over as the idea comes together in visual form).

So I had the wife pick up a small "marker board" (8 1/2" x 11 1/2") for about $3.00 US, just like the large ones used for presentations.

With the marker board it's easy to remove whole sections of a design if necessary, and is still small enough to rotate and get an idea how the thing might look as it turns around.

Faster than CAD (for me anyway) and sure beats a chalkboard. ;)

Mac