i got an old Athearn RDC and no matter what i did, it never ran well. I guess its inherent of the rubber band drive, I was wondering if theres an easy, cheap fix to get that car moving reasonably well?. Im sure adding a power truck from NWSL would solve the problem but that power truck alone would cost 5 time what i paid for it years ago…
IIRC Ernst Mfg. made/makes a conversion kit for the Athearn Hi-Fi drives.
Here’s a photo of what i did
I removed one side of the drive shaft and put a flywheel on the end
also added lead weight for better rail contact
worked out good for the price
actually improved slow speed performance
This might be an option.
http://www.trainworld.com/2008_ho_scale.htm
Life Like Powered Units
#23972 Budd RDC2
#30385 Budd RDC3
Ahhh the old rubber band drive. Years ago this was the cats meow when it hit the market. I have a few old Athearn GP9’s that are rubber band drive. They never really ran really good, but were ok.
C&O Fan pointed out about adding a flywheel and just powering one truck. Thats going to be your cheapest way to go.
I have an old Hustler also made by Athearn, this little loco does run pretty good for as old as it is.
Back around 1960 or so there was an outfit whose name I can’t remember that offered flywheels for the rubber band drive units. They were held onto the motor shafts with a setscrew and had a counterbore so the driveshaft could be hooked back up. That way all the axles could be powered. I’m not certain they would fit on the RDC, but I know they worked on the GP.
I have several RDC’s that are rubber band drive and one that has the conversion pwr truck on both ends…This one runs exquistly well,if you have the money I would buy the conversion trucks…
Spending a lot of time and money on the original Athearn RDCs is to me a waste of effort. They are shorter than the prototype, and great quality Life-Like RDCs can be bought for very little. As someone noted, Trainworld offers the RDC-2 for $19.95; the RDC-3 for $14.95 and the RDC-1 for $59.95 for some reason. I’ve bought several from them over the years, there is no choice of roadnames at these prices.
Power trucks like the NWLS PDT are or were in the $70-80 range each.
I have quite a few of the Athearn models, including their original 1950’s metal ones. I bought an Ernst regearing kit a long time ago, but noted it didn’t seem to be worth the effort to install it. It required grinding away some of the frame near the powered truck and a fair amount of fiddling around. I never used it.
If you must keep the original rubber band powered models, just get a supply of new rubber bands and replace them once in a while.
I’d park it on a shelf and get a new Proto 1000 RDC, which would no doubt run much, much smoother than the Athearn. A fellow club member has an old Athearn engine with the rubber band drive that must go a scale 500 miles per hour.
You could do what the MBTA did after they blew out most of the RDC engines. Pull them with a F unit. Boston commuter trains of RDC’s pulled by F unuts ran from the 1970’s until the T came into money and bought new cars and locomotives in the earlier '90’s.
DS:
Big John did that too…remember Big John? 
Maybe Ernst had a couple different versions of their gear drive, but I found the conversion for the RDC I have took less than an hour, and gave me the ability to haul an Athearn dummy RDC-3 and an extra coach or two at reasonable speeds. I wish the conversion on my Hustler was going as well.