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I'm beginning to lust after the Bachmann K-27 but have several concerns that you pioneering owners might be able to help me with. I am in a small town in the mountains of Colo and do not even have access to a hobby shop to look at one. From reading the threads, it appears that Bachmann has now solved most if not all the serious design issues. 1) Am I correct on this?

Unfortunately, I have several curves on my layout where I had to use 8' diameter track. 2) Will the K-27 easily take 8' diameter without larger diameter transition track?

Finally, I had to quit using a Bachman Annie on my Aristo stainless 4 years ago as I am convinced that some sort of electrolysis occurred between the cast drivers on the Annie and the stainless track: required serious cleanup every 10 minutes of operation to the point of serious frustration. (I had no problem with the turned steel drivers of my LGB locos.) Of course, that was just on DC, not DCC which I am presently using. 3) Does the K-27 have power pickup thorough the drivers or throuch a 'shoe' a la LGB? 4) Are the drivers of the K-27 cast rather than turned? 5) Has anyone with stainless track experienced unusual black deposit on stainless while using the K-27?

6) Any recommendations of DCC decoders for ease of installation on the K-27?

I can perhaps answer all your questions. I currently have 3 K27 models on my layout. I have both stainless and brass track, run both DC and battery power, and have numerous LGB 1600 turnouts (which are gradually getting replaced on the main line)

I should note that I did provide some thoughts to Bachmann prior and post release and and this locomotive is clearly my favorite locomotive on my railroad.

The very early first production locomotives had loose counterweights. While there are likely a few of these models still in the market with this issue, Bachmann replaced all the ones that Dealers notified them on. If you get one of these Bachmann will supply free replacements which can easily be replaced.

The power pickups are through the drivers and work exceptionally well in both DC and DCC. With one K-27 I have installed Hybrid Drive so that I do not have to clean wheels or track. My others have other boards at present and work fine but these do have to have their wheels cleaned from time to time like any locomotive. As an aside installing Hybrid drive on your Annie will completely solve the issue you were having with the wheels.

The K27 has the expanded Aristo Craft socket which is identical to the one Aristo has been using for about 10 years. You asked about DCC use. QSI and ESU have DCC sound boards that plug into the socket. The ESU board supports all the functions including sound with no modifications. The QSI board requires a simple inversion transistor should you wish to use the on board chuff circuits rather then the boards auto chuff feature. There is one chuff sensor in each cylinder triggered at the half way point.

Perhaps it would be useful if I also commented on some of the comments that Matthew provided.

There is an issue with the horizontal play in the axles on the locomotive. On mine, Dave Goodson was good enough to lock the first and fourth axles with washers. This solves the problem of the locomotive sliding sideways on curves and striking objects near the track because the whole locomotive tended to travel to the outside of the curve, but still allows the inner axles to slide, which helps the locomotive on tighter curves. Other people have come up with other solutions, or run theirs as-is, in some cases adjusting the clearance along their lines to accomodate the 'slide."

As shipped the drivers of the K27 locomotive can go around 5 ft curves.(the total locomotive an tender need a little more then a 6 foot diameter). This is accomplished by a design with has an inner and outer axle with side play. Many of us have layouts designed for smaller locomotives and the K27 is rather large by comparison. Because of the locomotives size and design the side to side play can cause clearance problems on many layouts. As noted Dave Goodson developed a method to reduce the side to side play by locking the 1st and 4th axles. I did this on one of my K27s. Because of the subsequent tendency to derail I quickly altered the approach. One can accommodate 90% of what Dave was trying to accommodate and improve the locomotive tracking at the same time by locking the 2nd and forth axles. Locking the axles will indeed reduce side to side play but will increase the radius required. With this mode the locomotive will still easily handle LGB 1600 curves This after market improvement is totally optional. I should note that over time I have adjusted my layout to accommodate a greater side to side play and have not decided if I will do this mode to my other K27s.

Note that if you have the snowplow version you will have to do a minor mod for Aristo manual turnouts to prevent the plow from hitting the manual throw mechanism.

There is an electrical issue whereby the chuff trigger requires power for the light source in the optical chuff ... this makes the chuff inoperative at low speeds without modification. The chuff was also designed on a positive trigger instead of a ground trigger, which posed some problems with some existing control and sound systems. Those users who chose to use "auto chuff" of one kind or another avoided the issue entirely, and others installed circuits to power the light source, and invert the chuff signal. On mine, Dave Goodson installed a new chuff timer of the magnetic reed type on the rearmost drive axle, which works very well, and again circumvents the entire problem.

Perhaps I can correct this observation a little. Low track voltages not low speed. Most sound boards designed for DC use require a battery to run at low track voltages. The K27s motor will start at a slightly lower voltage then the chuff circuit. A pair of diodes on one motor lead (the LGB approach to allow the electronics to activate before the motor) or coupling the locomotives and battery circuit both solve this issue. DCC or RC users will not see this issue. The second issue raised is the need for a chuff inversion for many but not all sound systems. The ESU plug in board for DCC users works fine and the RCS plug in board for RC users has the required inversion built in. If you want to use a sound system that requires the inversion it is very simple to add.

There are some questions as to the current handling capabilities of the on-board electronics. My locomotive is equipped with battery power and radio control, and most of the factory wiring (the ubiquitous "Super Socket") have been removed .... so I'm not in a position to comment personally on the extent of the problem. You might ask Bob Grosh, or other users who installed DCC equipment about their results with this.

I try to follow all reported problems for this locomotive and I am not aware of any current handling issue if the stock electronics are used.. I run my railroad at 21.5 volts DCC and have many hours on my K27s

Finally the motor and gearing produce some interesting problems. The locomotive has a large motor and very solid metal gears, which is good ... but the gearing of those gears is such that the locomotive behaves as if it were a truck stuck in third or fourth gear sometimes, and has some issues with acceleration (see: very steep (fast) curve) and a lot of power consumption in the higher ranges. That said, the locomotive will pull prototypically long trains nicely, and with a little practice on the throttle can be made to run well, however if you have grades on your layout, you will find it difficult to find a "cruise" speed and walk away from the controls, particularly with a long train. To date there is NO fix for this particular issue, but I understand that the speed control inherent to some DCC systems may deal with it somewhat.

An issue you will likely never encounter. The K27 has a top speed that is very similar to other plastic models built by companies such as Aristocraft, LGB, Charles RO and others. This top speed is twice a K27 prototype speed and much faster then many comparable brass models. While the prototype modeler likes the slower speeds, the market still demands the faster speeds. Most of us use the after market electronics we have chosen to adjust our top speed to suit our preferences.

The K27 has a very large motor and some electronics in the market have problems powering the motor/gear mechanism. Comments such as a sluggishness, poor acceleration or stuck in third gear are an observation of a poor marrage between the drive and the electronics. Other electronics in the market is designed for high efficiency drives and the power is smooth across the speed range. I have used Lenz, QSI and ESU drives in my K27s. All have high frequency back emf as part of their design and none have any of the problems reported by Matthew. In fact several sound manufacturers had to slightly alter their software to accommodate the ultra slow performance that is achievable by this model.

Hope that helps.

Stan Ames

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354 Posts
So, the motors are to small, draw to many amps, and the gearing is wrong. That I understand. Would it be almost impossible to modify one and get it right???

Unfortunately whenever the Bachmann K-27 is discussed a lot of emotions seem to be put forward. We all have differences of opinion but hopefully it is possible to have civil discussions.

Dave has posted some useful information so lets continue the thread by filling in some of the blanks omitted.

The current production Bachmann K-27 uses a Pittmann 19 volt 9234 motor with ball bearings. This is one of the most powerful motor used in any large scale locomotive.

It has a max torque rating of over 41 oz-in and is an excellent choice for such a large model.

I am a modeler and not an expert in motor selection or gear ratio so when Dave first raised the question of gear ratio I asked several manufacturers who are known for excellent motor/gear selection.

What I learned is that the motor gear ratio is not as simple as a set number, there are many factors that go into the optimal selection.

Dave has a lot of experience with the Pittmann 8000 series motor and Dave has observed that for the 8000 series motor in a typical large scale locomotive that 30 to 1 is optimum for his usage. That of course assumes a similar driver size and similar desired top speed.

But there are differences. For one the 8000 series motor is a 10,000 RMP motor while the 9000 series motor is a 6,000 RPM motor, The same gear ratio for both motors is going to result in a much different speed curve as well as a much different top end speed.

Other factors are driver size weight, trying to stay at the high efficiency side of the motor curve and ensuring that the locomotive slips well before motor stall.

When all this is factored into a locomotive the final and key issue is both slow speed performance and top speed. And it is the top speed that is the hardest for modelers to agree on.

As has been pointed out on a few other threads there is a great difference in what modelers desire in their large scale models. We are very fortunate that multiple manufacturers are building some beautiful locomotives in a variety of large scales. But we as a community do face an interesting issue. It takes a lot of money to produce a mass produced model so the manufacturers have to support a large variety of modelers.

On the high end we are very concerned about fidelity to scale and gauge and also prototypical speed. The mass market however tends to operate trains faster and is less concerned with the details and specific prototype.

What the manufacturers are trying to do is develop models that can appeal to both groups of modelers. This can be a win win for all concerned.

The K-27 prototype has a max allowed speed of 30mph. This speed limit is posted in the cab. A typical RC user operated his locomotive at 14.4 volts and the Bachman K27 will have a top end speed in the 30mh range at that voltage.

Some time back when this issue first came up I actually measured the speed of the Bachmann K-27 at a scale of 1:20.3. Unless I made a mistake in the calculations the unloaded speed on DC was 41 scale MPH at 18 volts DC. At 23 VDC 69 scale MPH and at 13.8 VDC about 33 scale MPH. Personally I think the 24 volt speed is a little high. I personally prefer a mid 50s speed at 24 volts as this allows headroom at the slightly lower voltages but can live with the slightly faster top speed. At the low end I measured 0.2 scale miles per hour which is well below what the prototype is capable of.

If I do the math right, for you 1:29 folks for comparison that would be a top speed at 24 volts of under 50mph which is slower than the max speed of most of your equipment and well in your preferred operating range.

If we as a community could agree on a desired top speed then I am sure we could get the manufacturers to implement that desire. But as it is now a lot of us like to run our locomotives much faster than prototype narrow gauge speeds and reducing the 24 volt DC top speed of the Bachmann K-27 by half as Dave suggests would I fear only appeal to a very few.

I am confident that if there are enough models that prefer a lower speed that after market folks will develop a new set of gearing. For me the current gearing is fine as most of the electronics I use has the ability to customize the speed range and it is trivial to set the top end speed to be what I desire. For DC users that want a slower top end speed simply do not crank the throttle up to full voltage.

Hopefully the above provides a balanced view of gearing issue and perhaps will lead to a positive and productive discussion on desired top end speed for the community.

Stan Ames

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354 Posts
Discussing this with Barry, he advises me that his new replacement gearbox and motor for the 2-8-0 Bachmann Consolidation is ready for production after having been field tested.

He also states that he would be willing to discuss with you sharing the use of the development of this new gearbox, which has ball-bearings on each shaft, and quite beefy gearing.

The 9000 series motors I have will bolt into this gearbox and fit his worms.


I saw Barry’s drive in Phoenix. Very impressive and with the 8000 series motor a sure hit in the 2-8-0. The 2-8-0s production motor is way under powered and Barry’s replacement will be a big plus. Barry also told me that his drive would fit the 9000 motor.

Any yes indeed with a 30:1 reduction you will get a true scale 30mph on the K27 at 24Vdc. But this for me who runs at 20 volts will likely be to slow a top end speed and in the opinion of most its way to slow for the mass market. I personally believe it will be a hard sell get Bachmann to half the top end speeds for their models.

I always welcome discussions with Barry as I am also a customer. But I do not understand your comment about sharing development. Those types of comments should be directed to Bachmann Industries. I think you can agree that they have shown in the K27 that they know how to build a top end motor gear box. True you do not like the top end speed but that is a marketing decision they have made. Perhaps we can get a 10-20% reduction in top end speed at 24 volts in the future but frankly most do not see a real large market for real slow models in Large Scale.

But who knows. If Barry’s replacement drive is a real big hit and the market starts wanting slow models who knows, they have adopted to change in the past and will likely continue to do so in the future.

I will be in Portland next week for the NNGC and I believe Lee Riley from Bachmann Industries will be in attendance as well. Why not stop by and share your thoughts.

Stan Ames

PS In Phoenix Barry was using the 8000 motor. The 9000 K27 motors I sent you some time back to look over have a continuous torque of 6.1, max 41 while the 8000 motor has a 2.6 continuous max 17. While I am sure Barry can get an 8000 series motor in the 2-8-0 I doubt a 9000 will fit and likewise while he can get a 8000 motor in the K27, I suspect he will find it is not powerful enough. I also suspect you will find that the 9000 motor in the same drive will result in a slower top end speed then the 8000 motor. I for one have an open mind and will be eager to see the results in both locomotives.

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354 Posts

Thanks for the most informative post. It will take some time to get to the bottom of all of your observations. Some are likely limitations of the model and your observations will hopefully lead to improvements. Some of what you report may be a result of a damaged locomotive or a result of the modifications you made. All manufacturers have a feature set they provide in their models. As modelers we often modify them to try to improve upon them but it is often a mistake to blame the manufacture when we are unsuccessful with those modifications.

I am on my way to Portland so I am unable to take apart one of my Ks to try to recreate some of your observations until I return. Some of what you report however can easily be addressed.

Lets take them one at a time.

It will navigate my R3 turnouts at each end of the passenger sidings.

The only problem is, the loco AND TENDER WON'T.

It throws the tender off the tracks at both ends of both sidings. I looked at possible modifications, but decided they weren't worth the effort. and would make the loco look bad.

Just so we are on the same page by R3 you mean the 1600 line of turnouts. As many have reported (even in this thread) the locomotive and tender work just fine on these turnouts. If you like I can post a video of the K27 (and tender) going through a pair at full speed. I made this video while experimenting with Daves axle locking procedure.

So why then do you have problems while others do not. I think I may have a clue. When I first got a K27 of my own, the first thing I did was take it apart so I could fully understand it from the perspective of the additions I chose to make. When I reassembled it the first time my locomotive and tender could no longer navigate 1600 turnouts. Most times the tender derailed. After a lot of head scratching I found the reason was that I had inadvertently shortened the wires to the tender and when the locomotive entered the 1600 curve it literally picked the tender wheels off the track. The problem went away when I went back and lengthened the wires. Perhaps you inadvertently did the same thing.

There have been many reports that screw towers inside the tender break. Three of the four in my tender were broken. In addition, part of the tender shell was broke out at the rear.

When you first got the K, I seem to remember you reported a greatly damaged outer box that occurred during shipping. I would never accept a clearly damaged model. All manufacturers will try to improve things when problems occur but some things are out of their control. The back of the tender does not get a hole in like yours had without some real extreme pressure. In your case a shipment that clearly had gone through the wringer and had a broken tender inside should in my opinion been immediately returned.

This time I noticed that the third right hand driver had a wobble.

I knew I had not moved the front wheel to the third position, so I removed the CW. and found... A BENT SCREW.

The problem seemed to go away. still, every once in a while, It won't budge going forward after a smooth gentle stop when backing a string of cars. When that happens, the only way to get it to move, is to throw it in reverse, back up slightly and then go forward. When it is locked, all the junk on the sides are free of binds, only the geared driver is tight.

I mentioned the shipping damage because I know of no one else who has these performance problems. True with the loose counterweights many had binding problems, especially on rollers, but to the best of my knowledge no one else has had these binding problems or bent screw problems once the proper counterweights were installed. I can not help you with this one. In my opinion, either something got real damaged in shipment, you put it back together wrong, or something has been damaged in some other fashion. All 3 of my K-27s have the replacement counterweights (one set I did the others had been done already) and none have any binding problems. Perhaps someone else can help you with this one.

To get the smoke to come out the stack, remove the four screws holding the fan in place. Discard the two longer screws. Flip the fan over and re-install the two shorter screws.

Yep you are credited at finding this one. A fan that blows air into the locomotive is sure going to dampen the smoke output.

Despite assurances that the fancy current regulator would not interfere with FX effects like firebox flicker, they did. There is no way to get the two phase flicker effect included with Digitrax and SoundTraxx decoders to work through the Bachmann circuits.

Bachmann uses a single wire to control its firebox flicker. To get the effects you desired you need two independent wires to control the flicker. There is nothing wrong with wanting to add more features to a model than is provided off the shelf. Many of us do this type of enhancement to a model. (I especially like the three LED effect on the classification lights) I doubt that you will ever get all your desired effects in a production locomotive

If you want the headlight to brighten and dim properly in sync with the generator sound on a Tsunami sound card. you will have to bypass the regulator circuit

I have not tried the Tsunami effects but all the other brands tested the effects work just fine with no mods. For example the ESU decoder also has a similar lighting generator effect and it works perfectly out of the box with the K-27. Current regulation is usually ideal for LED effects. When I return I will try to get with Soundtraxx and figure out why you had the problem. In Phoenix Soundtraxx was demonstrating the Tsumani with the Airwore RC inside the K27 and I thought they showed the lighting effects working properly but I may be mistaken on this so will check it out.

Those are the easy issues you raised

Now lets get to the harder ones.

I noticed that this train lugged down the Kay in the curves.

An interesting set of observations. I will have to try to recreate your cause and effect. I chose a different set of decoders for my installations and have absolutely no lugging or lack of power in or out of curves. My slow speed performance is exceptional and my Ks will pull much longer trains than you report up the long 2% and 3% grades on my railroad. I can set the locomotive at speed step one and it will tie crawl over the entire layout for hours with no change in speed or ability to pull. 12 volt versions of the same Pitmann motors are used in brass O scale and one of the brass builders has used them for year. He also has reported that not all decoders control these motors well. It is the high efficiency aspect of these motors that can confuse the back emf detection on most of the earlier decoders and many of the decoders produced today. For many years these motors have been the gold standard for achieving good performance which few have met. I will have to talk to him about his observations with the decoders you chose but based on the magazine decoder reviews performed in Europe, I suspect this one of the the real root causes of the problem you have reported.

I was also noticing burn marks on the tops of both my brass and Nickle silver rails. Some might mistake these burn marks for a crud build up. In reality they seemed to me to be caused by arcing. By watching the loco at night I discovered severe sparking on only one side of the loco when running on DC. On DCC the arcing was less, but equal on both sides of the loco. By running the loco in one direction for an hour on on a freshly polished test track, I discovered the black "deposits" were only showing up on one rail, the one where I observed the sparking. I therefor theorize that these black "deposits" are related to the arcing and may be carbon deposited from the pits in the wheels.

It has been a long time since I have run on DC but I will try to recreate your observation when I return. On DCC with the installs I did I have not observed the problem you report and on one locomotive I am charging batteries as well as operating the motor and effects. As we discussed in the past the capacitors on the +- leads can cause problems with some decoders. In particular manufacturer of the decoder you chose specifically cut the ground wire on their production decoders because they did not want this connection made. This issue interests me so I will look more into it when I have some time. Perhaps there is a design principle that needs to be explored for specifying internal locomotive wiring that needs to be explored here.

All for now

Stan Ames

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354 Posts
Stanley, you stuck your nose in where it didn't belong, utilizing skills you didn't have, and you alone stand responsible.
Now you're involved with the Liver Spot, and God alone knows what you've done there.


The above is a well written expression of your feelings. It is very unfortunate that you self destructed on the internet earlier this year and no I did not do any of the things you claim I did to you, you did it to yourself.

In the past you have been a great asset to the hobby. Most of us here have used your procedures to improve on those model you choose to do this on or used your procedures as a starting point to develop our own set if improvements.

Bachmann industries took a great risk in developing what is perhaps the most advanced 1:20.3 mass produced model ever produced. Many of us in the community had pleaded for years for Bachmann to produce a large locomotive. And many of us clearly hope that they will produce another such model for a different prototype in the future. Most of us who have this model really enjoy it and to many of us it is our favorite locomotive.

We had many discussions and many attempts were made to get you involved. You simply can not continuously insult everyone; try to scare everyone with fictional door number two, DCC for all, etc; break confidences continuously; and expect people to share things with you.

Unfortunately since the first pre production locomotive first ran on my layout last year as part of the NNGC, you have continuously blasted me, many Bachmann employees, their products and just about anyone who tries to post anything positive.

I truly hope that in the future there is a way to work together for the better of the hobby which is why I invited you to sit down in Portland next week and try to work things out. I am going to be in your neighborhood as an attendee and Bachmann will be there as an exhibitor. Its not often that such an opportunity presents itself.

You have worked hard to get a very loyal and vocal customer base who will follow you anywhere. Lets hope the community can find a way to harness this energy in a positive fashion for the good of the large scale community.

Stan Ames
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