I just installed Rodney Eddington's gearbox between the factory Pittman motor and the existing Bachmann gearbox on my K-27 #455. I also added some lead to the engine.  At full voltage, (19 volts), the engine moves along at just over half of it's original speed. At 14 volts, (the voltage I intend to use to RC/battery control), the speed is much more realistic with way better torque. It will pull 10 cars up a curving 4% grade barely slowing. It's more like starting up in 1st gear instead of 3rd gear. Before the conversion the engine would slow way down on even modest curves and then would take off like a rocket on the straight track. Now only minor voltage changes are needed if at all to control the speed. With this new gearbox the engine runs very smooth with only slight gear noise. I uploaded a video to Youtube from my phone. The noise you can hear is from a plane that I didn't notice while I was shooting the clip.

http://www.youtube.com/watch?v=bGENcVgSbv0

If anyone is interested in this modification Rodney Eddington can be contacted at:
http://www.randkrailroadproducts.com/

I know that Rodney has been working on this project for two years and I am really happy to have a solution for the gear ratio problem. This brings the ratio close to what I think Bachmann originally intended. The K-27 is such a beautiful engine. I think this gearbox will help the K-27 to run as good as it looks.

John Lyans

Hello Bach-mann,

I was just wondering if there has been any discussion or if there are any plans to address the problem of the 15:1 gear ratio on the K-27?  My K-27 runs smoothly but I can't run it double-headed with my Accucraft K-27 because the gearing is too high. I understand the intention was to have 30:1 gearing but this didn't happen. What would it take, a different gear box or a different output at the motor?

I don't think it was intended for these fine models to run a scale 80 mph at 18 volts.  Also, the model's operation would sure improve on both up and downhill grades, (especially uphill).

Do you know of any fixes for this problem? Thank you.

John

QuoteDear All,
As reported here, some (many? all?) K-27s have loose counterweights that can bind from time to time. Dave Goodson has examined the locos and made a suggestion, which has been independently corroborated by a couple of other Large Scalers.
We have been in contact with China, and shim sets are being prepared. A call to the service department will get you a set. I'll post here when they arrive; please hold your calls until then.

Bach Man,
Wow, I had hoped for something better than that. I don't think that this is the best solution.  I am a relatively experienced modeler and this is a task that is not for the faint of heart.  I have placed brass shims in four counterweights so far and they have varied from .004" on the drive axle to just under .008" on the fourth axle. They don't go on real easy and some of the axle ends have to be filed down a little.  Also, a lot of people are going to end up with those little plastic retainers broken.  The thicknesses of the needed shims vary some from model to model which will make for a difficult fix unless a variety of shim thicknesses are provided.  There are a lot of folks that won't mind taking this on but I don't think the majority of your customers are going to want to be filing away on the axles.

I think a better, but admittedly more costly solution would be to make up new counterweights with the correct fit at the axle and a little bit thicker so that the axles wouldn't have to be filed. I wouldn't even mind paying for better fitting counterweights.

Sorry to make this observation because this is a beautiful model, perhaps the nicest looking 1:20.3 model I have ever seen.

Thank you.
John