Remotorising (2019)

The drive of the Philotrain SHM 26 kit was supplied in the form of a Tenshodo SPUD WB 26. As mentioned often during the build of this model the riding qualities of this thing were less than desirable, to say the least. After much tinkering and experimentation I was not able to make it run reliably, much to my frustration I must add. Finally I finished this model and put it in my display cabinet as a non-runner.

It kept bugging me though and over time I kept searching for solutions mainly aimed towards building my own drive. I bought a Sagami drive with gearing in the hope I could somehow convert it to fit in the existing space. I couldn't. The main problem was the extremely restricted space. With only 26 mm between the axles and a fully closed footplate on top there was hardly any more space to fit anything else then another Tenshodo SPUD. Even other underfloor solutions were often just a tad bigger or higher.

After many thought on available solutions I decided to try and scratch build my own drive. I bought Alan Gibson wheels, sprung axle bearings, frame spacers, a motor from Tramfabriek and various belt drive parts from Nigel Lawton. I had a plan at last. I made my own frame plates from brass sheet. Then at some point I found I had made an recoverable error in drawing up the frameplates and progress stalled. My attention turned to other projects and the whole thing rested.

Early attempts

Top half: my scratch build attempt, with the smallest motor being from Tramfabriek. Bottom half,right: the Sagami drive which never took off

The Universal Power Bogie kit

The contents of the package was simple enough. An etch with the frame plates, the spacers and an optional top plate and some washers. And a bag with drive components. The second (top) bag was added because I needed conversion bushes from the 2 mm axles to the 1/8" axle hole in the Alan Gibson wheels I already had. It also contained a longer layshaft as I wanted to add two tiny flywheels.

The included manual was simple enough, for anybody who ever built a loco almost everything is self-explanatory. Yet some fully adequate drawings clarify the few dark passages in the building process.

Publication of the manual on this site was kindly granted by Mark Clark

The individual drive components

Construction

The frame spacers were soldered into place. The frame plates offer multiple positions for the axle bearings to achieve the correct wheelbase.

This is how the motor will fit into the frame. The ruler demonstrates how small the Universal Power Bogie is. I made this photo for demonstration purposes only. The manual clearly states to solder the second frame plate first and then slip the motor with a twist into place in the opening in the frame plates. I forgot an soldered the second frame with the motor still in place. A bit more fiddly, but then again it is a fiddly hobby.

Once the axle fits in the first bush, mark the reamer with a water proof felt pen and the other bushes can quickly be reamed to the same size.

Same story for the delrin gears, now aiming for press fit. If that has been achieved, the gears are placed in the exact centre. A mark is made with a water proof felt pen. The gear is slid aside, a bit of epoxy glue is added and the gear is slid back into place working the epoxy under it.

The holes in the brass worms are also a bit undersize. Although it would be technically desirable to aim for a press fit, it will in practice be difficult to press the worms on the layshaft when it is in the frame. So I opted to ream so they would just slide over the layshaft. They will be secured with epoxy later.

As reamers are tapered, ream from both sides in equal measures so the narrowest point of the hole will be approximately halfway the worm.

Now the motor is slipped into place and the second frame plate is soldered.

Do not forget to insert the axles before soldering because you cannot get them in after soldering if you have already glued the delrin end gears in place.

I turned two 7 mm long 6 mm wide brass flywheels from brass rod, each weighing a diminutive 2 grams each!

The centre hole is drilled undersize and reamed to fit the layshaft.

I could not make them any longer as they will then cover the screws that will hold the power unit to the superstructure. Neither could I make them any wider as they will become too high to fit under the superstructure. I hope four grams will make a visible difference. If it doesn't well, I tried :-)

Again a photo for demonstration purposes (the belt drive isn't even there!), just to show where the flywheels will go.

The third wheel is added and quartered approximately. You do not need to achieve an exact 90 degrees as long as the angles on both axles are the same. So 90 degrees by eye is good enough.

For Dutch steam locomotives the rule of thumb is that the right hand leads, so the right wheel sits at three o'clock (pointing forward) when the left wheel is at twelve when looking at the face of the wheel.

I made two temporary coupling rods that exactly match the wheelbase of the loco.

Once the glue of the third wheel had set completely I glued the fourth wheel, quartered it approximately and added the coupling rods. Then I gently pushed the loco over a piece of track. This movement forced the fourth wheel, with its glue still soft, to take the same position as the third wheel by the action of the coupling rods. Then I let the glue set. The fourth is now quartered in the very same position as the third wheel.

The layshaft is put into place at the same time adding the main pulley and the belt. Don't forget it, you won't be able to add it after this stage

First step in adding the worms is moving a washer over the layshaft.

The trick here is glueing the worm and the worm alone. I use a greased paper shim for that. It serves two purposes:

• glue won't hold on grease so when a little overspill touches the paper cum grease it will cause no harm;
• the shim will also automatically create a little play for the layshaft once the shim is removed.

The shim is pre-drilled with a hole of 1.3 mm, slightly less then the the shaft's diameter, so when moving it over the shaft the paper forms a tight, shallow collar. When placed the grease is added with a brush.

Then a bit of glue is put on the shaft. Although the paper shim should hold the glue in check there is no reason to be liberal with glue, we are talking droplets on pin points here!

The worm is gently rocked back and forth over the shaft while moving forward.

And so goes on the second worm, with one significant difference. You cannot rock the worms back and forth and move it forward, because the delrin gear is now blocked by the the other gear over the wheels and the coupling rods. And you need the keep the rods in place in order to keep the wheels synchronised. I you fail to do so you have the feedback over the coupling rods effecting both worms causing the unit to stall. So it is not only quartering that is utmost important but also synchronising. The trick to move the worm in place is turning clockwise, let the worm grab the delrin end gear and gently continue turning it until it reaches the paper shim.

Done! Two new coupling rods

Electric pickups

The electrical wipers were made of two 2.0 mm wide strips of copper clad circuit board which where soldered together with the base of the wiper. The  piece of black insulation will keep the wiper off the motor and prevent a short. It also serves to space the two copper strips correctly during soldering.

A home-made top plate

SHM 26 showing off its new hooves. She runs fine.

The SHM 26 stabled along three other builds of mine.