Hello I was wondering how many cars an Athearn ready to run HO scale dash 9- 44 cw can pull. My layout has no grades. I am thinking some where along the lines of 20-30 cars.
I have the Bluebox version, but it can haul all of my 20 or so cars around my curvy layout with ease, but I have to be easy on the throttle on the get-go so I don’t do a “burnout”. 
Hope this helps.
Keep adding cars until you run out of traction.
That’s what i do!
My last layout had a 3.5% grade & my AC4400 had no issues with 20 cars.
Gordon
How much you can pull is going to depend on the quality of the rolling stock’s wheelsets and weight, also. With wheels that put a lot of drag onto the loco, you’re not going to be able to pull as many cars as you could if they have good, free-rolling wheels.
Santa Fe, I have a RTR Athearn Dash 9. Mine when it is running will pull 20+ cars. I did add a little weight put stock it should handle 20 free wheeling cars.
With that being said, I would look at Kato and Proto 2000’s instead of Athearn’s RTR engines. I personally have had very bad luck with there motors. I have 4 of the RTR engines and the only one running at this point is the Dash 9, and it sounds like it’s motor is on it last leg.
Cuda Ken
You must just have very bad luck or you’re overloading the motors trying to pull too much weight. Of the 100+ Athearn blue box, RTR, and Genesis locomotives owned by members of our local club, not one single motor has ever needed to be replaced.
You could be right about working them to hard. But, I have seen other post about there RTR motors being a little hit and miss on QC.
Cuda Ken
Hi Ken, Regarding Athearn’s BB motors, I’ve worked on a ton of these and found the quality is there, you just have to bring it out. The first thing I noticed was the magnets in the motors that ran poorly were not the same consistent length and were actually longer than the outside shell of the motor. End play on many of the armatures was either horribly sloppy or non-existant and caused binding. Also, the armature bushings on several of the motors were pressed in crooked. I re-assembled the motor housing without the armature and checked this by sliding a length of drill rod the same size as the motor shaft thru both bushings and turned it with my fingers.
I chucked the armature in a small table top drill press and spun it at a medium speed, to eyeball it for concentricity and these were mostly all perfect. While in the press, I carefully cleaned the commutator with a machinist’s rubber stick. It did a nice job of polishing the thin copper. With the motor re-assembled with no brushes installed, I checked the armatures end play. Athearn used to use thin brass washers for shims, then went to plastic ones. If there was a lot of end to end sloppiness, there was a chance of the brushes to hit the wired end of the com. I found Kadee truck washers worked perfectly in eliminating it. During the re-assembly, I made sure the top and bottom motor housing clips had approximately the same holding tension.
Brush springs are another problem with these motors. Some are stiffer than the others and on several of them I had to remove part of the coil to make them even. After going this far, I alway’s replaced the brushes, making sure the curve in the brush lined up with the curve of the com. After putting everything back together, I gave each end of the shaft a sideway’s tap with a plastic screwdriver. A small drop of Labelle oil on each bushing and power from a small transformer, the run in began. Watching that the RPM’s stayed consistant and there was minimal or no sparking at the commutator, I
That’s some great info for motor tuning/ maintainance, I remember doing very much the same years ago w/ slot car motor tuning and balance.