I don't want to convert it to a one speed bike at a cost of several bucks, and still not have what i need. What I want to do is to put a coaster wheel on the rear of a lightweight bike frame. I also want to put a twenty inch crank set on it. Those crank sets only come in coaster configuration. A twenty speed bike comes with two different front chain rings. I don't need them and they probably won't fit on a 20" crank.
If you stick a home made drive on the rear wheel, it is most likely to get in the way of a levered brake. Hence the question... Can I swap out the cranks. I did it on a three speed lightweight frame bike, but the road bikes are even lighter weight. I have no idea if the crank is compatible They probably are but I would hate to have a bike I couldn't use laying around.
I'm trying hard to avoid a trip to the bike shop because they don't do this kind of modification. They will insist I buy what they are selling not what I want to do.
The frame of a road (also called racing) bike is much lighter and usually made of aluminum as I understand it.