Many forum members will be aware that besides owning H0 trains I also have a few 1 Gauge locos and trains, including a KM1 BR01 180 steam locomotive that features KM1 Dynamic smoke.

The loco with all smoke features turned on looks quite spectacular and is quite popular at our MRR shows and has featured on the cover of the NZ National Association of Model Railroaders magazine 'The Coupler'.

The following is a Youtube video showing how the smoke looks when working properly.



Unfortunately in the last year or so, the cylinder smoke has stopped working, although the smokestack smoke still works.

With some help from KM1, this is how I fixed the problem - I know that at least one other forum member owns this loco and others may own other KM1 locos so I hope this blog post will help anyone with the same issue.

The first decision to make was whether to send the loco back to KM1 for repair, or attempt to do the repair myself. Given the return trip would cost $600 NZD+ plus the repair cost, that was never an option. KM1 advised the following parts would be needed:

Wig material – 3,00 €
Smoke-fan – 5,35 € (these turned out to be replacement fan motors)
Smoke sensor – 9,90€

Note: I use term 'Smoke Sensor' as that's the term KM1 use for it. However, it consists of a small diode and a large green resistor and it more accurately might be described as a heater element for the smoke fluid.

Two sets of each item are needed for the smoke unit repair. Contact details for KM1 are at https://www.km-1.de/html/kontakt.html

This is what you get.



On the left is a fan motor, centre are smoke sensors and on the right is one of the Wig material items (not sure if this should be called the wick).

The instructions as advised by KM1 to remove the smoke unit are "To bring the smoke-unit out you have to open fire box-door and losen the screws from the ring. Then you can remove it.
Then loosen the screw in the chimney and the small screws left and right of the smoke generator. Then you can pull it out carefully."



That translates to removing screws 3 and 4. You will also need to remove screw 12 as it will impede the extraction of the smoke unit.

I got a bit confused by the instruction "loosen the screw in the chimney" which made me think the screw was down inside the smokestack. After poking around with a screwdriver and putting a small led down the smokestack to see where the screw was, I eventually realised that the smokestack itself was the screw - You can see on all KM1 steam locos (I checked a few others belonging to a friend) have a hex head built into the top of the smokestack. Using a 6.5mm hex key I unscrewed the smokestack from the smoke unit.



Photo from a KM1 BR03 clearly showing the hex head built into the smokestack.



Smokestack after it had been removed from my BR01.

We can now extract the smoke unit. First, you have to retract the lower nozzle from the plastic tube - refer to the picture above of the front of the boiler. Under the smoke unit you can see a nozzle going down into a plastic tube. The nozzle is spring loaded and can be pushed up with a screwdriver enough to extract it from the tube. Once done pull the smoke unit towards the front of the loco's boiler being careful not to pinch or damage any of the wires at the front of the boiler.

Now that we have the smoke unit out, the real work begins.



We will need to remove the two screws holding the blue circuit board as well as the two screws holding each of the red plastic covers. The blue / black connector from the switch at the front also needs to be removed. I would suggest you photograph the position of all connectors, wires and screws before you remove them so that you know how to put them back.. For now, only remove the blue circuit board, the connector from the switch and the first red cover.



Front of the smoke unit



Rear of the smoke unit showing the fans. These will eventually be removed and the motors replaced with the new ones. Note the connectors as these will have to be lined up with the socket inside the loco's boiler when refitting the smoke unit.



Clearer picture of the two fans.



Picture showing the smoke unit with the blue circuit board unscrewed and folded away at the bottom. Be careful not to break any wires. Note the two sets of blue and red wires going to the fans at the rear. Now you can unscrew the two screws holding the top red plastic cover on. Remove the cover.



This exposes the wires attached to the back of the smoke sensor. Make a note of the sequence of where each wire is connected to as the old smoke sensor will get unsoldered and the new one put in its place. Don't forget the two fan motor wires.



Underside of the smoke sensor, with the wig material perished into two pieces and looking rather manky. Note the charring - this makes me wonder whether someone ran the loco with the smoke unit on with no fluid in it (Other folks were known to run this loco at shows when I was off doing other things).

New fan motor and smoke sensor



Paper based gasket which came off the front of the smoke sensor. I reused it, but I could have made a new one with some ordinary automotive gasket paper.



New smoke sensor with the paper gasket fitted



Picture of the 2nd smoke sensor after I removed it with the wig material still attached. The replacement wig material is inserted into the new smoke sensor end up and inserted into the smoke unit. You wedge the wig material in between the green component and the wire loop, compressing the wire loop inwards to hold the wig in place.



At this point attach all the wires to the new smoke sensor in the correct order after removing all the wires from the old smoke sensor. Insert the wig material and new smoke sensor into the smoke unit, but don't put the cover back on yet as we still need to connect the new fan motor wires to the smoke sensor. Repeat the process for the other smoke sensor.

Now it is time to replace the fan motors.

Unscrew the two screws holding each of the fan motors in and remove them including the retaining clip, the motor holder and the fan itself. The fan and fan motor are both press fitted so it is easy enough to pull the fan off the motor spindle and pus the motor out of the housing. Reverse assemble with the new motor in place.

Picture showing the fan motor housing. Push the motor in with the two wires perpendicular to the mounting arms.



Picture showing the replacement motors installed.



Connect the wires from the fan motors to the two contacts at the left end of the smoke sensor. Once done put the red cover back on (making sure the holes in the gasket line up) and screw everything down.

When both fan motors have been connected and both red covers screwed back on you can screw the blue circuit board back in place. Don't forget to reconnect the two wires from the front switch.



Picture of the completed smoke unit repair - doesn't look much different to what came out!

Now we have to put the smoke unit back into the loco, which means we need to seat the smoke unit correctly into the rear connector while getting the nozzle at the bottom seated into the hose while avoiding pinching or breaking any of the wires at the front of the boiler. To avoid the later, I taped the wires to the side of the boiler making it easier to get the smoke unit in. The hard bit is getting the nozzle into the hose and I can't say there were any special tricks in doing so other than saying I had a screwdriver in one hand pushing the nozzle up against its spring loading and another screwdriver in the other hand trying to get the lip of the hose under the nozzle. Because the loco was still mounted on its baseboard it was easy enough to push the end of the baseboard up against the wall behind my desk to stop the loco moving.



Wires taped



Nozzle finally inserted into the hose.



Test of the reassembled smoke unit - also see the below video. Nice to see it smoking properly now!



Hope this blog is of some use.

Edited by user 16 January 2021 12:08:46(UTC)  | Reason: BD's rumpty spelling!

It's a common problem on KM-1 steamers. I suspect the smoke fluid is damaging the motors, but it's a guess.

Back when I was in large scale I fixed my KM-1 BR50 in a similar way. I didn't change the "smoke sensor" as it's always the motor that stops working. When I had the smoke generator apart I noticed the felt wicks were burned through and broke off, so obviously it's not the right material for the job.

What I did was:
1) Replace the fan motors with a slightly longer one which can be found as a spare part for the tail rotor for a micro RC helicopter.
2) Replace the wicks with pieces of braided fiberglass normally used as sealing gaskets on indoor stoves.

That worked for me.
I know of several refits with the tail rotor motors and none of them have failed as far as I know.

Just remembered that I've got some spare motors which are intended for a friend.

Size is 6mm diameter by 10.4mm length.