Readers' Engine Questions

| April/May 2002

A Brief Word

In the February issue there were numerous comments about repairing flywheels. Without going into the engineering details of stresses, forces and other technicalities, let it be said that ye olde Reflector is adamantly opposed to repairing flywheels. Our attitude is, 'If it's busted, don't use it.' While there are some people who likely can repair a flywheel in a satisfactory and safe way, there are many others who think they can. Why take the risk? Cast iron has a way of turning to shrapnel. We just don't think it is worth the risk.

In the same connection, there were numerous comments about shrink fits. Now in the case of a cracked hub (say around the keyway), an iron band shrunk over the hub is a good idea. However, don't take our word for it, talk with a professional engineer if one is available to you, or at the least consult a text like Machinery's Handbook before calculating the shrink you desire.

Some of the figures we saw in the February article will give too much shrink, and others will not give enough. Again, if you don't know what you are doing, go to someone who knows, and preferably not to some windbag who has all the answers to everything. We're sure you folks tire of us incessantly talking about safety, but that's the only way we can prevent a tragedy.

Remember, too, that the tragedy can happen in your own back yard, perhaps with your grandkids. Accidents don't just happen at engine shows or county fairs. Nowadays, in our sue-happy world, if it can be proved that you knew there was a problem ahead of time and did nothing about it, that's called negligence. If that is proved against you, somebody else is gonna own what you now call yours. Please be careful!

The March issue arrived while we were typing this copy in early February. We note the article about magnet chargers. We heartily agree that the more amp-turns the better job you will do of recharging a magnet. The matter of permeability is also important.

However, we have always charged a magnet by putting it over the poles, and after energizing the coils we tap the magnet lightly with a piece of brass (or a brass hammer). This helps rearrange the molecules within the magnet.