A friend & I keep jokeing about the pulling of a 4-8-4 hauling a freight with a 2-8-0 banker on the back pushing. I said around 80 cars. He said 75 to 100. Both engines are bachmann. Neither of us can't find out for 2 weeks because we want to do it on a operation day (canceled due to the holidays). Anyone got an educated geuss on how much they can pull on a flat surface?
Too many variables. Loco weights; car weights; rolling characteristics of the trucks; curves on the layout; etc. Given all that, my educated guess would be in the neighborhood of 50.
Let me share a little warning, from experience...
On model trains, when you have a 'helper' in the back, there is the possibility that something could happen to the lead locomotive: a derailment, stall... whatever. Then the helper is pushing cars into the problem up front. It can create a mess. The worst possibility is pushing cars off the cliff (edge of the layout).
That being said--it is loads of fun. I have done it with three locomotives: up front, in the middle and in the rear. I've even posted a video of it once. Did it with two Mountains and a Kanawha. I kept it easy with about 40 cars... then I have grades.
I'd agree that a rough guess would be 50 cars at the most, if all is rolling well.
Regards,
Jonathan