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Archive indexWay back in the mists of time I was a spotty apprentice at a Buckinghamshire garage that sold Cyclemasters and of course the early machines did not have a dismantleable silencer system. We had a way of de-carbonising which was a 100% efficient and lots of fun too ... it works well with a steel exhaust system that is not plated. An oxyacetylene welding torch with a No 3 nozzle is lit and placed in the top end, whereupon the carbon deposits will glow. The acetylene is then turned off and the burning carbon front will advance, being fed by oxygen alone, the progress of the burning being monitored by watching the dull red area of the exhaust.
Smoke will pour out the end as the oily deposits are removed and there may be an occasional bang as gases ignite at the flame front, so it's best to do it outside. Ideally send the Missus out and keep upstream of the smoke to avoid smelling like a kipper.
First published - April 1997
The dearth of Cyclaid belt rims and recent advertisements hunting for them, have prompted me to explain how I made mine.
Although the original rim was made of steel, I decided to make one out of copper first, as this metal is easily wrought, and then go on to make a steel one with the knowledge and skills I had learnt. In fact, the copper rim (painted black) works so well I have not yet bothered to make one of steel!
The first thing required is a wooden disc 12¾" in diameter. ¾" blockboard or chipboard is ideal. You will need about 50" of ½" copper water pipe. This is first annealed by bringing it to red heat and then quenching in cold water. Copper in this state will bend easily around the disc, but do beg or borrow a plumber's bending spring to stop the tube from flattening. Allow the ends to curve past one another by 6" or so, to ensure they describe a true curve where they will meet.
Using a fine tooth saw, cut through both pipes where they pass. Gently pull the two cut ends into alignment. It is probably a good idea to anneal the copper again here. I didn't, in the belief that the work hardened metal should be better able to resist the engine's forces. But later on the copper was hard to work.
The next stage is to silver solder the ends together. You may find that some sort of clamp is necessary; I was lucky, the two ends stayed perfectly in place during soldering. Silver solder is the amateur engineer's 'dream glue'; it will allow you to fabricate almost anything, with a strength not far short of steel. (For those not familiar with it may I recommend: "Soldering and Brazing" by Tubal Cain, Argus Books Ltd?)
You should now have a continuous circle of tube of 12¾" inches internal diameter. The problem now is to cut right round the outer edge of the tube, just off centre.
I did this with a 14" hacksaw - it wasn't easy! It may be easier for people with access to a big enough lathe, to mount the tube on its wooden former, and pierce it with a narrow tool.
Next, keeping it true on the wooden disc, open out the cut. First with a screwdriver, then pliers when you can get them in the gap. Work around the rim a bit at a time, don't try to open up too much in one place. Finish off the long side with a hammer on a flat surface. You now have a J-section ring. Again with pliers and a little at a time, turn the short edge outwards and, after inserting a bit of ½" bar or rod in the channel, hammer this edge down.
The rim should work and transmit the power in this basic form, but a few refinements are advisable. From about 6" of 1¼" × 1¼" hardwood I made a male and female shape of the required V-section. After putting one half in the vice, I worked round and round the rim with hammer blows on the other half former. It wasn't very successful! Steel blocks would have worked much better. However, after squeezing around the inner edges with a Mole wrench and a lot more hammering with the blocks, the result was quite acceptable. Remember that, on a pulley of this size, the belt contact area does not have to be perfect to have a much larger grip than the little engine pulley has.
Lastly, because copper is softer and more easily deformed than steel, I soft soldered strips of brass to reinforce the back of the rim where it is bolted to the spokes. Short lengths of alloy strip (about 3/4" × 3/8" × 1/8"), drilled and tapped 4BA, behind each spoke complete the operation and you are now ready to spend even more time than you did making it, in trying to get it central and running true on your wheel.
Paint the rim black; shiny copper would look wrong - and give the game away!
My local bearing stockist informs me that:
Most bearing suppliers will give you 40% - 50% discount if you ask for it.
As with all small two stroke motors, it is recommended that during restoration and renovation, as well as attention to the magneto and compression, the oil seals and bearings are also changed. Due to the technicalities of the two stroke engine and the 'sump' acting as a pressure vessel, it is necessary for the 'sump' to be gas tight. Crankcase seals therefore are most important in this respect.
To help fellow Mini-Motor owners, since ours has recently received the bearing/bush treatment after the Stowmarket run on which it performed less than satisfactorily (it now performs admirably), the following are the items obtained from our local dealers (Bearing Services Ltd - but Edmunds Walker are probably just as good and I am sure there are other similar places).
Total cost about £20 - for a world of difference.