Making a bench power supply to test car & bike starter motors at no load?
Car Starter motors on large cars do draw a lot of current even at no load .Old pre internet figure is 70 Amps at 12 VDC revving at 7800 rpm .This is from Joseph LUCAS Prince of darkness .The more modern permanant magnet motors will draw less and rev less under no load .Delco units like the lucas units are series wound and behave pretty much the same .Your bridge rectifier is not man enough to do the job .Your transformer will be OK for intermittant use under no load .We did this for a saw bench with rectifier diode aggregate rated at 400 amps .Remember that the start current of the starter motor is many times the run current at no load .I used lots of 100 Volt TO247 shottkies to rectify the DC .You could parallel your bridges to stop them blowing up at start up .You could also use big stud mount diodes .These series wound motors are not happy at 7800 rpm    long term,There are stories about solder in the commutator softening in the heat and the copper bars flying apart that I have not seen .If your transformer setup makes less than 12VDC when running the starter motor then it will not turn as fast making your set up more idiot proof .I would check your Armature resistance figure .It seems far too high ,