Model Flat-Belt Pulley Wheels


| November/December 1983



Wheels

1001 Parcus Rd., S.E. Huntsville, AL 35803

In my visits to steam shows, I have had the pleasure of seeing many fine models of old engines and machinery, of special interest to me was the several model threshers I've came across since I'm building one myself and hope to build more in the future. I've seen many approaches to the fabrication of the belt pulleys ranging from using solid sleeves to soldered, built up, spoked pulleys.

There are indeed many methods that can be used. A good method is the 'lost wax' or investment casting procedure; however, not many modelers have the necessary expertise to make use of this technique. Beautiful castings can be made if they do.

The method I settled on produces pulleys that look very much like they are cast; however, in my estimation, it is much easier. It does require the use of a lathe, however. A small lathe such as a Taig Micro Lathe should serve just fine for this procedure and they do not cost an arm and a leg either. I use a 9inch lathe on which I've made pulleys from one half inch in diameter up to six inches both straight spoked and curved spoked and solid web with and without lightning holes. This procedure will also serve just fine for making spokes in gears, sprockets and hand wheels. For gears and sprockets I purchase the correct size solid units from a supplier and finish them myself to shape.

I will assume that the research has been completed and that the scale dimensions are established. I use aluminum in my discussion although other metals may be used. Prepare a billet of aluminum of sufficient size to make the pulley. This can be prepared from either round rod stock or from flat sheet stock. The round rod stock is ideal if you can get it. Turn it to the correct outside diameter and leave it uncrowned for the time being. If flat sheet stock is used you may have to turn it first on one side and then on the other unless the stock is thick enough to make the pulley with metal left over. Many of the pulleys on my model are on inch wide. I started out with a one inch thick octagon of aluminum which I chucked with one fourth in the chuck and three fourths out to be turned down to near the final diameter. Since one is not likely to get a match, when you rotate the piece, finish the final pass on the out side diameter when you prepare to crown the pulley. Turning a piece in this manner involves working the lathe bit very close to the chuck so extreme care is advised to prevent gouging into the chuck. Also, do not inhale any of the aluminum dust if it is created.

Two alternate methods may be used if the pulley characteristics permit. One is to turn the inside of the pulley down first and rough out the hub. Then chuck onto the hub and turn down the blank using very light cuts. The second is to bore the shaft hole first and use a mandrel again use very light cuts.