Clarifying Some Dolly Wheel Issues
 

Someone correct me where I err (I would like to know I have this right):

Durometer: describes the hardness or smoothness of a wheel. 78a being one if not the most smoothest; 90a or so being the hardest. It is best to have a low-number durometer.

Abec: an association that rates bearings. abec7 is the smoothest bearing. Pair an abec7 with a wheel with a 78a durometer.

Are skateboard wheels and in-line wheels different? If so, what is the difference. And which is preferrable?

I've noticed there are different milimeter sizes of skateboard wheels. Does the mm size matter? What are the advantages/disadvantages of smaller/larger mm sizes? Will I have to match a bearing size with the wheel mm size?

I am about to build a dolly, using a combination of plans I've skimmed over on this site and over at HomeBuiltStabilizers. Any added info would help.

Lee B.

Roller blade wheels are softer (wrong word... less rigid?) than skateboard wheels. Also, the curved shape of a roller blade wheel compared to a typical skateboard wheel allows smoother movement along your track.

I went with larger diameter wheels. 1) you have more material to cushion along the track, 2) more surface area means more stability along the track.

Best advice I can give is don't skimp on the wheels. Make sure they have quality bearings. You don't need the best of the best, but don't get the cheapest thing you can find. You're build will ultimately suffer for it (lowQ bearings, misaligned grooves/tread, etc).

Lee,

Durometer readings do indicate the hardness or softness of rubber or plastics. The higher the number the harder the rubber. What you use depends on what type of dolly you are building, and what surface it will ride on.

If you use a softer rubber it will be quieter, but will not roll as easy. The softer the rubber and the more weight you put on it, the more it will make the contact area flatten out. As it flattens out, it will act more like a flat tire and it will push like you are going up hill. If you moving the dolly on a very smooth surface, you can use a harder wheel, as it will move quietly, but on a rougher surface you will need a softer wheel to make it quiet and dampen the vibrations.

The larger the wheel, the easier it will push and the rougher the surface it will go over with ease. If you are building a dolly to run in a track and your track is smooth, a small harder wheel like a rollerblade wheel would be fine. If it is free moving and will be used on many surfaces, then go for larger softer wheels. If it will be used on carpeted surfaces then go with larger wheels to make it move easier, as smaller wheels will sink further into the carpet and it will again move like you are going up hill, (which in reality you are!)

Another consideration is the width of the wheel. A rollerblade wheel is very narrow at the contact area and therefore must be much harder to support the weight without compressing or flattening very much. A skateboard wheel is much wider and so it can be much softer.

As far as the bearings go, you do not need ABEC 7s. These are generally used as bearings on the spindles of machine tools. I have installed a sets of two that cost over $10,000 in machines. If they are already in the wheels you buy fine, (and you may find them in some rollerblade wheels, as they are getting less expensive all the time), but if you buy the bearings separately just make sure they are a good quality ball bearing and they are shielded, or sealed on both sides. That keeps out dirt and other contaminates that will destroy them and make them unsmooth. Of course there should be two bearings in each wheel to prevent wobbling on the axel. MM size is just the size of the wheel and just get them with the bearings already installed.

IMHO, a set of rollerblade or skateboard wheels would be fine for what you are probably building. If you want to show me the plans, I could advise you further.

Sorry, I didn't see that I was rambling on so.

Mike

If you can find a roller skating rink, this is a terrific resource. The last bag 'o wheels and bearings cost me 5 bucks for about 30 wheels. These from old boot style roller skates. Originally I used the common mount at 45 degrees on angle aluminum secured to a heavy piece of mdf double thick for a gross weight of about 100 pounds.
Today, these home built bogies reside on an old studio dolly 3 arm spreader on wheels. Runs on 1 1/4 inch abs.
Perfect stability and the whole rig is carried under one arm.