Large Scale Central

K27 - Fred was right!

Modeling Rolling stock
#1

In a previous thread there was some discussion about Doug Matheson’s Bachmann K27 teeter-tottering on its third set of drive wheels. Posts from other K27 owners convinced Doug and I that this was normal, but Fred insisted this was wrong. As this would probably reduce the tractive effort of the locomotive and encourage derailments, the locomotive was opened to investigate the cause of the problem. The investigation revealed the installation of the R and K reduction gearbox had stopped the motor and Bachman gearbox from be able to pivot.

The reduction gearbox moved the K7 motor rearward about 1 1/4 inches. This unfortunately caused the K27 fan to prevent the gearbox and motor from pivoting normally, and interfered with the suspension of the third drive axle to which the motor and Bachmann gearbox are attached. The impression in the Play-Doh shows the fan pressing on the new gearbox and limiting motion of the motor.

To eliminate the problem, the fan wires were unsoldered from the K27 printed circuit board, and the fan removed. But that only solved one of the problems. In the area behind the motor is a large printed circuit board with several sets of headers and multi-wire connectors. Now that the space for this myriad of heavy wires was cut in half by moving the motor back 1 1/4 inches, the wires were interfering with the movement of the motor and rubbing on the flywheel.

Although some K27 owners trimmed the mounting posts of the circuit board to resolve the problem, it appeared this would not provide enough clearance for the headers, connectors, and wires on the front of circuit board above the flywheel. Noticing that the motor was offset to one side, it was decided to mount the circuit board in the larger space on one side of the boiler.

The circuit board was fastened to the side of the boiler with hot glue. The wires on the front of the circuit board were pressed against the boiler and taped in place to insure they did not interfere with the flywheel or movement of the motor. All other wires were routed over the flickering firebox as the boiler was re-installed. After the locomotive was re-assembled, it was placed on a piece of track. All the wheels now sat squarely on the rails, and all four drive axles now moved freely on their suspension components. The teeter-tottering effect of the frozen third axle had been eliminated. This should improve the tractive effort of this fine locomotive. The locomotive was then taken and tested on the IPP&W Railway. Except for plowing aside the occasional bits of intrusive scenery, the K27 ran flawlessly. Fred was right! All four sets of K27 drive wheels should sit squarely on the rails and move up and down freely on their suspension components.

#2

Quote:
The reduction gearbox moved the K7 motor rearward about 1 1/4 inches. This unfortunately caused the K27 fan to prevent the gearbox and motor from pivoting normally, and interfered with the suspension of the third drive axle to which the motor and Bachmann gearbox are attached. The impression in the Play-Doh shows the fan pressing on the new gearbox and limiting motion of the motor.

I told Doug all that when I talked to him on the phone. I had noticed that pivoting motion before I started working on it. I removed the fan and moved the top circuit board up out of the way. That relieved the problem for me. As a matter of fact, I couldn’t even get the boiler shell to set down all the way without removing the fan and moving the circuit board. The board on the bottom was fine. All I did with that one was place some tape around it and held in place with a ty-wrap, just in case. I checked the pivot motion and it was moving freely.

(http://rgsgardenrailroad.com/K_regeared03.jpg)

Quote:
Except for plowing aside the occasional bits of intrusive scenery, the K27 ran flawlessly.

Mine always comes around after a trip with a snoot full of flower petals, tiny branches and leaves…:wink:

#3

Yep, I think Rodney even told me that the fan would have to move/be removed. So I removed mine. Just like Ken, I couldnt even get the boiler shell down because the fan was in the way.

#4

Good info.
I’m starting my RK conversion soon.
But I had already removed the fan and gutted every piece of electronics out of the
shell, hardwired the motor and lights back to the tender for AW.
So I should be OK.

#5

If you remove the fan, do you have problems with heat in the boiler area?

#6

I haven’t had any heating problems.
But all the electronic stuff is gone, except the big motor.
And the motor produces only minimal heat.
I have no idea what the fan was for.

#7

@Jake,

I am not sure how much heat it takes to ‘have problems’ with heat, but I have run mine in the middle of a Florida panhandle summer sunny day, close to 100 degrees ambient and had no trouble. In that confined space, with as little available space for free flow of ‘cool’ air, mine ran flawlessly. I was completely bone stock, out of the box, Bachmann at that time (about years ago).

On the other hand, a fellow club member running some dismal in NS scheme with a Revolution controller on board shut down from heat overload about 2 weeks ago at our club meeting. The ambient was about 85 and the sun was no where near the intensity when I was running my K. I am considering going with a Revolution, and from that experience have already decided that fans in the tender to control the heat will be absolutely necessary (not for the B’mann electronics but the Aristo).

My tuppence worth.

Bob C.

#8

I’m making a guess here, but I’d say mine has about 50 hours of running time on it and I’ve never had any problems from the heat, and it runs mainly in the summer or in warm weather anyway… It’s even sat out on the layout in the sun. I would venture another guess and say that with the reduction gear, the motor probably isn’t working as hard as it would be without that gearing especially on hills.

What I do worry about when it’s hot is the batteries and electronics in the tender, so if the engine is going to sit for awhile, I lift off the coal load and set it x-wise over the opening so heat doesn’t build up in the tender, but still shades the insides. . Since I have to remove it anyway to shut it off, it’s just easier to do that.

#9

Sorry for not getting here sooner but I’ve been under the weather the last 3 weeks and getting better now.

I just realized that the fan pc board issuse is not in my instructions and will get that included.

Paul
I like the way the way you relocated the PC board. That is a very nice way of doing it and will try it on on of my new ones.

Jake
I have over 1000 hours on one of my K-27’s and have had no problem with the motor getting hot. With the gear reduction, the motor
is not working as hard to move the train and is does not build heat. When I was testing the gearboxes, most of the time I was pulling 60
pounds of lead in 2 gondolas for up to 12 hours at a time and the motor stayed cool.

Bob
I have Revolution in one of mine and never had a heat related shut down even running in 90 deg plus heat. I don’t think you will have any
problems with the receiver getting to hot in the tender.

Rodney

#10

@Rodney,

The fellow club member who experienced the trouble has had this happen before. I believe the loco is a USAT hood unit but don’t remember which one. I don’t doubt that others have experienced different results over heat, it is a frustrating element. The second reason I am going to use the fans, I am also looking into Lithium batteries, and am acutely aware of the temperature sensitivity of them. I have not done a check of the surface termp of the tender shell, but think I will this summer. It might be interesting information. I can tell you that in the panhandle of Florida, at 2:00pm in the afternoon after a couple of hours of running in the summer sun, you want a towel between your hand and the shell to pick it up, it is d@$% HOT!

As an aside, I have measured rail temp at 145 degrees in late August or early September, out of the peak of sun and heat. Most electronics don’t like to function above about 120 without additional cooling, hence the fans.

Welcome back and glad to hear you are recovering. Had read on another forum you were under the weather.

Bob C.

#11

Bob
I have had a lot of problems with Revolution in Aristo and USA Train locomotives overheating and this is running on the club layout in the mall where the air temp is around 80 deg. These loco run on track power and I think the problem is in the stock electronics in the locomotives. One of the problem loco, a Aristo E-8, I’m going to gut the electronics out and give it a try and see what happens.

With the exception of the one K-27, I have Airwire in everything that I have converted to battery and have had NO
heat problems and using Cordless Renovations Li-ion batteries. Nice thing about the batteries is if something goes
wrong with them, Rick will stand behind them 1000%.

I know that there has been a few time that I been working on the layout and burnt fingers on the rail in the late afternoon with the temps around 100 deg.

Rodney