idler rumble, heat, and record wear--a connection?

Is it an L34?

You might try a heavier oil and new rubber on the wheel because it is possible to get rid of the rumble. Check the idler wheel shaft, too.

I wouldn't worry so much about the heat, although there should be a way to devise a deflector, if it really bothers you.

At 33 rpm, assuming no significant slippage of the idler wheel against the platter, and assuming there is some sort of mat between the platter and the LP that ought not to be a very efficient conductor of heat, unless it's made of copper, I cannot imagine that it could be "normal" for the LP to heat up as much as 30 degrees F during one 20-minute play. Something is amiss. I am thinking about the bearing assembly in particular.

Lew... that was a thoughtful reply. +1

Maybe there's a heat lamp hanging over the turntable.

I'm thinking the massive ply plinth does not allow enough ventilation. Seems like after 1 hour of use when I remove the LP, it's like it was in a warm car. I've had tons of turntables, even a good number of idler drives, but this is my first idler ROK. With the clunky motor, the heat generated isn't so much my concern, its record wear from a warmed, softened LP.