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Author Topic: Re-gearing the Bachmann K-27  (Read 7936 times)

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« on: April 04, 2011, 04:26:43 AM »

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.

If anyone is interested in this modification Rodney Eddington can be contacted at:
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

« Last Edit: April 04, 2011, 04:29:59 AM by JLyans » Logged
Jon D. Miller

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« Reply #1 on: April 06, 2011, 03:24:06 PM »

Thanks for the information on Mr. Edington's gear box.  Also thanks for posting the video.

I sent my motor to him this morning to have a gear box installed.  Sent an e-mail and he responded the unit will be returned the first part of next week.

I've had the K-27 since they were first introduced.  My K-27 has in excess of 1000 hours of run time.  Never a problem with anything on the locomotive.  It's proven to be bullet proof.  The Edington great box should make this fine unit even better.

"One of the Enthusiastic Children"



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« Reply #2 on: April 16, 2011, 06:44:19 PM »

 I want to John Lyans for his help and support this project.

 Jon Miller, Thank you for your purchase.
Jon wanted all brass gears so he could test a few things.
 I have sent out over 20 of the gearboxes and I wanted to have some
feedback on them before I posted anything here. So far the feedback
has been great and the gear noise gets better the more they are used.

 I have been very busy with gearboxes and getting the website up
and running. The website is still a long way from where I want it, but
it is getting it there slowly.

 The gearbox is a gear reduction that goes between the motor and the
stock Bachmann gearbox.  There is 4 gears in it, 2 of them are brass and
the other 2 are Delrin.  This gearbox is all made in house, including the
gears. The final gear ratio with this gearbox is almost 26 to 1.  The only
modifications needed to install this gearbox is that the fan and the PC
board in the top of the boiler needs to be raised by simply cutting off
the plastic studs about 1/4". Most feel that the fan is no longer need
and are leaving it out.

  I use 3 of the K-27 for testing and they are:

 #453  latest release with metal tender trucks and factory added weight.
Aristocraft revolution installed in factory socket, Phoenix sound, with 18
volt battery installed in tender.

 #463 Early release with revised counterweights installed. 3 pounds of lead
added and balanced between 2nd and 3rd drivers. PC board removed from
tender and Airewire and Phoenix sound wired in to factory wiring. 18 volt
battery installed.

 #464 Early release with shimmed counterweights. Over 5 pounds of lead
added and balanced  between 2nd and 3 rd drivers. Factory wiring gutted
and Airwire, Phoenix sound and 18 volt battery installed.

 All of my locomotives are wired for a battery car also.

 For testing on my layout, I use Accucraft gondolas with lead weight in them.
I also use 2 sets of rollers in the shop and they run on them in bad weather.
  With #464 I have pulled over 100 lbs in the gondolas on a flat track.
On the 4% grade on my layout, I have started and stopped pulling 60
lbs of weight. It slips just a little at the start.


  My overall view of Bachmann K-27 is that it is the best engineered locomotive
available in plastic except for the factory gear ratio. It comes close to the
Accucraft and Berlyn brass.  I have completely tore a chassis down to the
bare frame. The driver equalizers work, and all the driver axles are running
in ball bearings. The factory gearbox is bullet proof with what I think is a
stainless steel worm, a bearing bronze worm gear and a brass idler and
a brass gear that drives the axle. The drivers appears to be cast of some
sort of bronze also. The 9000 pittman motor is what used it the Accucraft
and Berlyn brass and has more power than most will ever use.  I think the
Bachmann K-27 is the best deal on any large scale locomotive.

 I model 20.3 and have over 25 Bachmann 20.3 locomotives, 6 of them are K's.
My layout is built around what they have to offer in this scale. I also have
a Accucrft K-28,  K-36 and Berlyn K-36 and K-37.  

 Now if we can talk Bachmann into doing a K-28. I would make a great
locomotive to run with the K-27 on any layout.

I will add some pictures and video within the next few days of the
K's on the layout.

 Here is the link to my website and my e-mail and phone number
is there if you have any questions.

 Thanks for your interest

Rodney Edington
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« Last Edit: April 17, 2011, 10:40:12 PM by R and K RR Products » Logged

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Barry BBT

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« Reply #3 on: April 17, 2011, 07:57:59 PM »


One correction, the motor is indeed a 9000 series Pittman like Accucraft, but it is spec'd differently to different performance standards.
The motor turns faster and has higher torque ratings, plus it is a 19Volt motor.

Barry - BBT

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« Reply #4 on: April 18, 2011, 03:11:36 PM »

I'm curious about not needing the fan, I understand the motor does not need to provide as much torque but it is now turning faster to maintain the same loco speed, is it running cooler then it did before?  and if your adding more weight and cars then aren't you bringing the torque needed from the motor up? which = more heat? I don't have a K27 yet it's on my wish list this year and the gear box seems like a great upgrade so I would likely install one.

  I only set up my large scale tracks a few times a year for the holidays and I leave them running 8:00am to 10:pm, I want a K27 to run slowly around the perimeter pulling a long train.

I hope everyone will keep posting here on how their loco's perform.
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« Reply #5 on: April 19, 2011, 03:01:52 AM »

 Thank you for the information on the Pttman 9000
motor that Bachmann uses in the K-27.
As I recall, you spec'd this motor out.
It is a great motor.

  Narrow Minded
   I was told by somebody  that they burned up
1 or 2 motors on the prototype locomotive. This is why they
had the fan installed on the production run .The condition the
the locomotive was under when they had motor failure was
continuous hard pulling in very hot weather. The average
user will not be doing this to their locomotives. I'm not a
electronics guy but if I understand it right, using a lower
gear ratio such as my gearbox, the motor will not build up
a lot of heat cause you are using less energy to move the
train.  On my test locos, they have ran continuous for 12
to 14 hours pulling 30 to 40 pounds in the gondolas on my
home layout.  The hottest day we had since I started the
testing has been only 80 degrees.  As the layout stands
now, I have about 600 feet of mainline with almost all of
it on a grade. Here is some more information about it.


« Last Edit: April 19, 2011, 01:53:43 PM by R and K RR Products » Logged

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Jon D. Miller

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« Reply #6 on: April 19, 2011, 02:16:11 PM »

Completed the installation of Rodney's gear box to the point I could make an initial test run this morning.

This is the video of the K-27 with Rodney's gear box.  Installation was a piece of cake.  Moved a PC board at  back of boiler top to give more clearance.  Also modified fan location.  

You'll note the boiler/cab is not put in place.  That's masking tape on the cab holding up the foot board.

My battery was just about run down when the runs were made.  The gear box is smooth as silk.  At slow speed you can not hear any gear noise.  Any noise will be covered by the Phoenix sound.  The engine will run so slow the micro-processor in my old Phoenix system gets confused and keeps blowing the start forward signa.

It appears the 14.4 volts and the RCS PnP system will run the K-27 at speeds we usually run on the CD&stL.

Need to get the locomotive all put back together and do some serious running.  The K-27 does real well for a locomotive with over 1000 hours of run time.  I could find no wear on any components.  The K-27 has proven to be bullet proof.  Rodney's gear reduction box will only make the k-27 that much better.  Thanks for all your hard work Rodney.

One of the "Enthusiastic Children"

« Last Edit: April 19, 2011, 02:19:17 PM by Jon D. Miller » Logged

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Kevin Strong

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« Reply #7 on: April 19, 2011, 02:44:58 PM »

JD, if you've got Phoenix's programming software, you can reset the start voltage a bit lower.




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« Reply #8 on: April 19, 2011, 03:28:07 PM »


Not sure what you call hard pulling, but I have run mine on our club layout pulling 20+ mixed Bachmann/Aristo/LGB cars with steel wheels for over four hours in the Florida sunshine at 95+ degrees. I am not sure how much hotter the ambient can get, but I have (so far) experienced no motor issues, there runs were done at about 14 volts.  The loop of the layout I prefer to run on (best photo ops) is about 300 lineal feet with a 1.5% up and down gradient in the loop.

My tuppence worth.

Bob C.
Jon D. Miller

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« Reply #9 on: April 19, 2011, 05:50:47 PM »

thanks for the great tip.  I'll try to remember that with my 2K2 sound cards.  However, this Phoenix is one of the old BIg Sound systems that uses pre-programmed chips.  Not much I can do to change them.  Guess I should have mentioned that so as not to confuse folks.

One of the "Enthusiastic Children"



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« Reply #10 on: April 20, 2011, 03:37:54 PM »

Thanks Rodney that's Great news, I live in Southern California and the temps are 70 to 90 depending on the time of year, I'll be running it during the holidays so the temps are usually lower. I plan on running a long train so this info is good news.

I'm figuring on getting the K27 around Sept. and I'll likely get the gear box then as well.

Jon D. Miller

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« Reply #11 on: April 23, 2011, 04:11:39 PM »

The K-27 is now all put back together.  Spent most of today running with the new Edington gear box.  Slow speed and power are excellent.  Still has some gear whine.  Will experiment with some various types of lubricant.

This is a video of the k-27 slow running passing Delphos Depot with 18 loads.  The locomotive will maintain its speed around both 5' and 10' radius curves without slowing.  Given its performance the K-27 should be able to handle at least 25-30 loads on the CD&StL.

There are no grades on the CD&StL.  Our Track Foreman describes the profile as "undulating."  We can live with that! Wink

One of the "Enthusiastic Children"


« Last Edit: April 23, 2011, 09:52:51 PM by Jon D. Miller » Logged

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« Reply #12 on: April 25, 2011, 12:51:16 PM »

   The video looks good


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