MB-1-E Part Fifteen: Controller Upgrade

Dave,

Do you have a drill press and vise? What I did was drill a 1/4 inch hole offset 5/16" off center on my sprocket. Then, I drilled the centered 5/8 hole. For the key I filed the top edges of the key to fit in the half moon keyway created by the 1/4" hole. To hold the sprocket in the vise I drilled a hole in a block of dense wood using a hole saw the diameter of the outside of the sprocket. Then I cut the block of wood in half so I had two blocks of wood with a half moon cut in each half. I have what are called center dowels ( you could use a drill bit). They fit in the hole in the sprocket provided by the manufacturer which allows you to line up the spindle to the center the sprocket. Put the centering dowel in the chuck, put the sprocket on the dowel, line up the vise and clamp the vise tight against the sprocket, then clamp the vise down. Manually turn the spindle, you will feel if there is any runout. If the chuck spindle turns easily put in 1/2" drill bit and bore a hole, then put in a 5/8" bit and finish the hole. Good sharp drill bits and lubricant are required. Practice on an old sprocket or sheave if you can find one. I used a drill bit that was a thousanth over 5/8. Should have used a 5/8, I have to use locktite, that 1 thousanths was just a smidgeon to big.

Chuck

Dave,

Slow down, Don't drill that until I think about this. My motor drive sprocket is steel. You just said your's is aluminum. Rarely would you need lubricant on aluminum. High speed won't hurt on aluminum. I have been up since 5 am, thought I would check this site before I hit the hay. Aluminum will some times drill larger than the bit by a couple of thousanths, steel actually develops ridges when drilling which can make the hole about a few 10,000 thousanths smaller than the drill bit. A lot of the aluminum sprockets that I have come across are cast out of unknown properties. Some cast pulleys don't peel like steel, they powder. The dust from drllling these can make the hole size quite a bit larger. You can minimize your chuck runout with the bit that you buy. Visual sighting will suffice, use all three holes to tighten the drill bit, run the drill press, retighten all three holes if there is any visual runout. Use a digital caliper and measure the shaft on the scott motor before you buy your drill bit. Drill into some aluminum after you set the drill press up and try a fit before you drill the sprocket. Some of this is easy for me, I have chunks of all kinds of metal laying around. Aluminum is usually easy to identify by color, match the colors of two pieces of aluminum and they will usually machine the same. Aluminum machines very easily, drilling aluminum is not truly machining, runout is critical when drilling aluminum.

If you bought an alumimum sprocket from a top of the line manufacturer, I would not be so concerned, but, a lot of cheap sprockets are cast from aluminum and don't perform well. Also, with a good fit after boring, aluminum exands, so I would recommend locktite even on a perfect fit.

chuck

Dave,

Another comment,
No and yes I used a locking collar. I drilled a hole and used a hand tap to use a set screw to lock the sprocket to the motor shaft above the key. If you can remember, my sprocket drifted while I was riding which wore my belt enough that my belt started jumping. The sprocket drifted because of that 1 thousands over bore so I put a couple of collars on temporarily. Then, later on, I used blue loctite on the sprocket, will use red when I finalize my drive.

chuck

Dave,

Great!

Most machine shops want aluminum because it machines so well. Hope you drill this yourself. Usually my bores are better than the machine shops.. Just gotta check those tolerances before your final bore. Where I live here in Richardson TX, machine shops have $600,000 dollar minimum CNC machines, make parts for military and the electronics industry. No local small shops would bore this for less than $50.00.

I like aluminum sprockets if they are made well. There was a time I swore off aluminum. Belts slipped on cheap ones, the powder would act similar to a graphite and I would have to overtighten belts to overcome this. I did not think to ask Gates if they had aluminum in the pg2 line. My sprockets are cast on the perimeter, (just a guess). Usually cast iron pulleys are the smoothest running and the easist on belts but have seen drastic improvements in aluminum pulleys in the last few years. Very interested on this new development. Probably 90% of my belt noise, which is minimal, is from my over bored sprocket. My chain noise comes from the 14 tooth sprocket. Unbelievable the difference one tooth made. The chain was silent with a 15 tooth.

Chuck