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I'm sure this has been done before, but I think it would be interesting to make some of the surfaces that rub against each other in an engine out of bronze or even brass, since these two alloys offer some of the lowest coefficients of friction of any metal.
It might be a challenge making the engine
strong enough, and some of the metal might melt if things got out of hand, but these problems could easily be overcome, since bronze has about the same strength as aluminum, another metal widely used in engines. The biggest problem would probably be keeping the bronze from wearing off and floating around in the oil.
Even a thin coating of bronze or some other low-friction alloy could reduce engine wear. These coatings could also be applied to the valve seats to create a tighter seal, or to the surfaces of gears in the transmission to reduce friction.
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Nikasil is a common, extremely hard and low friction coating used especially for high rpm engines. Disadvantage is that when it gets damaged or finally wears out, it can not be bored or honed and the cylinder sleeve has to be replaced. |
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//since these two alloys offer some of the lowest coefficients of friction of any metal//
Not exactly. Brass is not good. Bearing grade bronze is not too bad, but sintered bronze, impregnated with lubricant is much better. At the temperatures in an engine cylinder though, any of them would be destroyed very rapidly.
Saying that the coefficient of friction is low is a bit misleading. You have to talk about the coefficient between two surfaces. You get the lowest coefficients when one material is a bit softer than the other, and different enough that it won't alloy itself with the other (bronze against steel, for instance). And then you have to consider all the other variables, such as load, lubrication, temperature, etc. The main factor in reducing wear is lubrication. |
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