Info re Bachmann K-27 from owners

haha, oh.....choke.......

"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. '

NOWHERE does he say it's wrong.
What he does is waffle on about "the market still demands the faster speeds".
And, that like Bose speakers, some manufacturers have "slightly alter"ed their software.

The gearing was supposed to be 29 or 30:1.
It IS 14.5:1.

Find me another steam loco with that gearing.

Toys, maybe, but certainly not 1:20.3 scale models!

One thing you may not have noticed, I have been working this problem for some time now.

I have copies of more stuff than even I can believe.


Stanley has many time said, in print, there is no problem with the gearing.
If 14.5:1 is okay, why not do away with gears altogether?

Remember:

Read with comprehension!

Posted By Marauderer on 09/03/2008 2:01 PM
Posted By Curmudgeon on 09/03/2008 9:10 AM
Another one failing to grasp the issue.
It isn't really worthwhile trying to explain it.
However, suffice it to say, if you follow Stanley's reasoning, we don't really need gears at all in our trains.
Rather, some new dcc control system, and the wheels connected directly to the motor shafts.
I am seriously puzzled by the total lack of any understanding of engineering and design principles shown by some.

That is pure bull on your part. All I got from that is that Stan felt the K 27 was geared wrong. No where did he say that gears shouild be done away with. Whats up???" border=0>




Oh, and telling me my comments are pure bull is not really productive.
I may be outspoken, and hard to get along with, but "bull" isn't part of the equation.

I did.

MANY years of experience showed about 30:1 with a 19V Pittman was ideal.

This engine is half that.

Because of that, the current "curve" is outside the normal envelope, i.e., while it will haul 28 cars on level track (do it), at 20 on 4% it exceeds 3 amps by so much it trips the output protection on the throttles every 4 feet.

Done it.

I know full slip is over 4 amps.

Elitist?

Really?

There is one person on this thread who qualifies as "elitist", and it i neither you nor I.

And, all of that said, the locomotive is fine within the confines of the limitations.
You stay inside something reasonable (like, say, prototypical loads on prototypical grades) you'll probably be just fine.

Personally, I don't like the current spike.
Nor 11/16" side-play at the pilot beam.
Nor cab doors that won't stay fully open.
Nor optical chuff triggers that don't work out of the box, nor wimpy yellow LED's and the need to re-wire to use incandescents.
Nor 13 wires between engine and tender (I cut out 5).

I know what was proposed over a year ago on the motor and gear ratios.
I have a fair idea of what was actually happening behind the scenes.

And, I'm not interested in doing any more to help sort out their issues under the current arrangement.

Waiting isn't going to accomplish much.
The "second run" of K's was originally scheduled for this fall.
That seems to have been supplanted by the Liver Spot.
The locomotive is what you get.
The fixes are easy, and if you don't run sound or don't care about bright incandescent-glow headlights, doors that open all the way, and have lots of side clearances with little grade or short trains, you're set.

The "fixes" are published.

I wasn't "involved" per se.
I was asked about motors and gearing, which I wrote a full report on (still have the original).

For 11-1/2 years now, I have been involved (on my own time and dime) with generating field fixes to keep locos running.
I tried to generate them in such a manner as to be able to be accomplished by the average modeler.

"Biggies" I have always run past Philly Phirst, to let them have a shot at their own "fix".
The last one, they sat on it, and it was released, including the "Model A" shim use (from the old shims when I had a Model A) to someone else to release, and I don't work with people who do that.

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
http://www.tttrains.com/largescale/

This is what was submitted:

K-27 motor proposal 12JUL07


I have in my possession for evaluation two Pittman motors for the upcoming K-27.

I have evaluated these motors, not only on their stand-alone merits, but based upon much experience with Pittman motors in Large-Scale locomotive.


Barry Olsen of Barry’s Big Trains uses Pittman motors.
I do R&D work with Barry on new chassis.
Much trial-and-error has resulted in a 19V motor that works with all applications.

The motors in hand are a 9234E847, 15VDC, and a 9234E848, 19VDC.
Follows is pertinent data:

9234E847 9234E848

Torque: 6.1 oz/in 6.1 oz/in

Stall Current 12.1A 10.1A

Continuous current 2A 1.7A

Max no-load speed 6150RPM 6150RPM

As you can see, the 15VDC motor will handle more current. The 19VDC motor will be a good “compromise”.
Be advised there is a 25-26% overload feature in both, so the 19VDC motor will function fine on 24VDC.
The 1.7A continuous rating of the 19VDC motor is about three times what any of your other engines draw.

Working with Barry, we discovered a 30:1 gear reduction was best for prototypical speeds. I would not want to see much less than 26:1, as we don’t need folks flying these big locos off curves.

The 30:1 works well with Barry’s use of Bachmann 4-6-0 2” drivers, as well as the 1.75” drivers on his 2-8-0.

I would suggest a double-lead worm with a gear reduction to obtain the desired end ratio.
Double-leads eliminate “worm lock”, yet can retard runaways on downgrades with heavy loads, something a gearhead motor with bevel gears on the axle are unable to accomplish.

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.

You need to discuss details with him.
++++++++++++++++++++++++++++

Since nobody runs at 6,000 or 10,000 RPM, the motor speed through the gears to the driver diameter governs speed.
Obviously, they missed the mark, and I know why.
Want that published, too?

And, you're right.
You DON'T know.

Hmmmm........I was wondering what was happening with the K-27 over at Bachmann! I, too, had my K-27 modified by Dave Goodson and I had him shim the counterweights (the fix before the replacement weights were available) shim the 1st and 4th drivers (by the way, NO derailments and the K tracks properly!) change out the headlights and the classification lamps (much better!) fix the door so it opens properly, rip out most of the electronics including the "supersocket" and install one of those tried and true "Jurassic Park" RCS r/c units with a Soundtraxx Sierra digital sound system and powered by NiMH batteries. My K-27 #463 is now the flagship of my fleet and it runs spectacularly!

DCC may indeed prove to be the wave of the future. Maybe someday I'll try it but for now I am satisfied with having my trains run when and where I want them to without having to worry about dirty track, polarity, amperage overload, computer interfaces, etc....

I'll say this one last time. Dave Goodson is THE expert where the issues of electronics and mechanical innards of Bachmann's products are concerned. He has time and time again devised "fixes" for each and every one of Bachmann's Spectrum locomotives and he has done this for the good of the hobby. He's not looking for a legacy! His reviews in Garden Railways were always scrupulously impartial but certain individuals at Bachmann were afraid of what he would publish about the K and more importantly, the "Super Socket" and so he was essentially "blacklisted" by Bachmann!! Dave may no longer be doing any reviews but I won't buy another new Bachmann engine unless he first goes over it and "debuggs" the thing!

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.


Dave

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.