# Regear Bachmann K27



## RIO WARREN (Dec 9, 2009)

can anyboby advise if there is an after market regear set of different ratios to Bachmanns std ,avaliable which might help with a slower speed & increase load capacity with out loading boiler with shot


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## steam5 (Jun 22, 2008)

Currently no after market parts available. 

Barry of Barry’s Big Trains has indicated he has been looking into some possible replacement parts, I’m sure he will see this thread and give an update. 

Alan


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## TonyWalsham (Jan 2, 2008)

The inventor of the "Super Socket" in the K-27, who also had quite a bit to do with the gearbox ratios claims there is no need to do anything to the gears. They are correct. 

Others disagree, and as you have found out, the gear ratio is most certainly not correct. 

As Alan has said, Barry Olsen is working on a replacement gear set. 
If it is as good as the new gearbox he recently released for the Bachmann 2-8-0, it will improve the K-27 greatly and provide the performance this excellent loco would otherwise be capable of.


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## chuck n (Jan 2, 2008)

Gentlemen:

I thought that I would do a simple test to see if the gearing of the Bachmann K-27 is reasonable. It is certainly a lot faster that either my Accucraft K-27, or my Accucraft K-28. You can decide for yourself if the gearing is OK or not.


This afternoon I timed the Bachmann on one lap of my layout. I measured the voltage on the track and the length of time it took to go around once. Several years ago I measured the length of the track and prepared a graph to match scale speed (MPH) with time. I have the table in 1:20.3, 1:22.5, and 1:29.

I believe that Bachmann says that this engine is to be run between 0 and 22 volts DC. 


Today's results are as follows:


10 volts 56 seconds 21 MPH 


13 volts 44 seconds 27 MPH

15 volts 35 seconds 35 MPH 

20 volts 25 seconds 50 MPH 

22 volts 22 seconds 55 MPH 

I believe that the top speed of this locomotive in real life was about 30 MPH. I would say that gearing that would allow slower speeds at higher voltages would give us more more control and greater pulling. 


Chuck N 


PS This was done with just the engine, no cars.


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## K27_463 (Jan 2, 2008)

Chuck: your estimate of real life speed on the narrow gauge is a bit too high. If 30 mph was ever achieved, it was for very brief periods on tangent track. 15-20 mph is far more typical and likely. There are numerous areas of documentation to affirm this. The problem is that even though you may achieve a reasonable speed of 21 mph at 10 volts, the B k27 has no power at that voltage. if you boost voltage to it to attain power, then it moves at warp speed as soon as the load is reduced. It is a very difficult loco to operate on any line other than table flat as a result. Finally, if you load the k27 down enough to allow the train to moderate the speed somewhat, then you are running the motor very close to rated stall, and things will heat up very fast as you are close to both rated voltage and current. The motor will not likely fail under these conditions, as it is a very high grade unit, but things could still get interesting. 
The best solution would be a 2:1 planetary reduction gearbox placed in line with the flywheel removed. This would provide both the proper overall gear ratio, and the needed power to allow fun operation. 

Jonathan/EMW


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## chuck n (Jan 2, 2008)

Jonathan:

I knew the 27 was slow, but I didn't realize that it was that slow. 


I agree, with a load, at 10v, it doesn't move a train or move it very well. I'm going to go out side and measure it with a 9 car load (including a caboose).


Chuck 


With the following load: 2 Accucraft box cars (with Phil's bbs), 2 Accucraft reefers (stock wheels), 4 Bachmann Spectrum hoppers, and a Bachmann Spectrum caboose, at 15 volts it took 42 seconds to go around. That is a scale speed of about 27 MPH. Much less voltage and I start having problems.


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## jimtyp (Jan 2, 2008)

According to Blackstone models, the K-27 prototypes were run, rarely, up to 45mph. 

This is regarding their HOn3 K-27 model running at full throttle: 

"At twelve volts, top speed was about 45 scale mph... well within the prototype's capabilities according to the old-timers (though they were seldom run at those speeds except perhaps on the straightest of track and when no one was looking!)" 

This review by Marc Horovitz claims: "Top speed was a sedate (estimated) 25-30 scale mph": 
 Accucraft K-27 Review


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## Steve Stockham (Jan 2, 2008)

You can forget Botchmann ever admitting (never mind fixing) this gearing problem! It was a "spin job" from the moment it was pointed out by customers! No, Barry has a gearbox that he's testing. Wait for it!


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## armorsmith (Jun 1, 2008)

Along with what has bee posted above about the prototype, it is my understanding that the 464 surviving on the Huckleberry RR in Michigan has a plackard on the backhead restricting operation to a maximum speed of 30mph. 

That being said, I also own a B'mann K-27 in G scale and will re-iterate what I have said on another forum about mine. To set up the scenario, I run on my club's layout in Florida. The second mainline is about 300 feet with an overpass with a 1-1.5% approach and decent. I have run my K with up to 23 mixed Bachamnn and LGB cars for several hours at about 12-14 volts, which runs it at about scale 20 MPH +/-. There is a visual decrease in speed on the up grade and a noticable run on the down grade. I find this to be quite prototypical, following the laws of physics. I have never noticed any excessive heating of the engine in the boiler area after a several hour run. 

That being said, is the gearing too high? Yes I believe it is, but not quite as high as Tony W. indicates. Based on the information I have been able to collect, I believe and additional 1.5:1 (total ratio of about 21:1) would be ideal. That would put the top speed at 22 volts right at 45 mph. And for all those who just want to see it go mindlessly 'round in circles, it would most likely pull some heavy grades without falling off in speed (not very prototypic). 

From my 'For what it's worth' dept. 

Bob C.


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## chuck n (Jan 2, 2008)

Nancy and I were out in the yard this evening having coffee and watching the K run with the consist listed earlier. I adjusted the voltage to where it would just make it around the layout. This is the speed and voltage that I usually use. It took 62 seconds to go around and the voltage was about 12 volts. This works our to about 19 MPH. Any lower it wouldn't go around.

Chuck N


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## K27_463 (Jan 2, 2008)

Do not forget that high speeds are a complex function of individual loco, tracks, and environment. For a k27 to go 45 the engineer would need to be absolutely fearless, the track in perfect condition, and no supervisor around. 
Engineers that are still alive have recounted stories about what happens as speeds climb. Inherent imbalance gets magnified at higher speeds and while theoretically possible, the loco bouncing on the rails, or in well related cases of the K28, begins hunting side to side as it goes down the track, dictated they never went at the speed that Baldwin calculated in Sales catalogs. DRGW track was very far from perfect, full of speed restrictions everywhere. Even the later and more modern k36 had many issues within the 10 loco class, and individual locos would behave differently and sometimes badly as speeds climbed past 25mph. As regards ideal gearing ratios, 21:1 is still too high for good operations. 19:1 has been tried and found deficient. Accucraft has used ratios from 30:1 up to 38:1 and this range works well. The Botchmann K is currently at 15:1. That is why a 2:1 planetary which would change overall ratio to 30:1 is the best solution, for both scale speed and good power. 

Jonathan/EMw


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## chuck n (Jan 2, 2008)

Jonathan:

I am eagerly awaiting a gear conversion. My only hope is that it will be simple and not too expensive. It is too bad that Bachmann seems to have problems on its otherwise fantastic locomotives (Conni and K-27).


Chuck


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## RIO WARREN (Dec 9, 2009)

Thank you gentlemen for your interest and replies I will keep an ear to the ground for any further developments to improve the operation and speed of my K 27 I was hoping that there may have been some one who had recalculated the gear ratios and could cut new sets of gears to use within the Bachmann gear box 

regards Rio Warren


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## BarrysBigTrains (Sep 4, 2008)

After studying the existing K-27 gearbox for a year or so.......A really nice gearbox, I couldn't change the gear ratio simply and reliably. I am taking a new approach which should work out a whole lot better.

After a bit more progress is made, I'll give some hints as to where we're going. One interesting note, you won't have to buy a motor, the one that is there is great.

Barry - BBT


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## TonyWalsham (Jan 2, 2008)

As Jon Bliese has suggested. A 2:1 reduction planetary gearbox mounted on the end of the motor would be ideal. 

Assuming there is room to fit it.


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## BarrysBigTrains (Sep 4, 2008)

Since the axle passes through the existing gearbox and the motor bolts to the gear box, you would need a gear head motor to add any gear changes. Too expensive.

Jonathon is right if there was a gearhead motor present, then just add the 2:1 gearsetBuilt on the existing axle 


Barry - BBT


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