In my experience burning out alternators on a Pontiac and an Oldsmobile, you can get about 100,000 miles out of it before expecting to replace the alternator.
alternators are classified as stators and rotors
Firstly, no you must not pick the particular Alternators
Make sure the alternators are properly installed and aligned.
This question is not clear since alternators produce alternating current.
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One can research the prices of used alternators by going online and looking up alternators of the right sort on Amazon. There are various different merchants there so they will have various prices.
Yes.
Alternators are generally not user repairable. It takes special tools and access to parts to repair. While there are repair centers, it may be cheaper to just replace it.
Alternators produce AC, which is rectified by diodes if DC is needed. Dynamos produce DC by using a commutator.
Depends on what kind of Race Car. Circle Dirt Track Race Cars Between races. Asphalt cars have alternators. Race cars have alternators that keep the battery charged while racing. Some dirt track cars have alternators some asphalt cars don't have alternators. Need more specifics.
Since the alternators are in parallel, the resultant voltage should be the same as either alternator - exactly as it would be if two batteries are connected in parallel. Voltage remains the same but current capacity is doubled. I would recommend connecting the alternators through a network that will balance the load between them.