Regauging Bemo 12mm HOm locos to 9mm H0e

After advice from members on several forums I managed to re-gauge theBemo 1260/1 Loco No. 81 ‘Wallis’ electric tunnel loco from 12mmH0m to 9mmH0e gauge. I thought therefore, as this information appears to be a well-hidden ‘secret’ that I would post how I did it.

1: To remove the bogie cover plates to expose the wheel-sets turn the loco upside down and insert a small screwdriver into the slot at the outer end of each bogie between the metal peg and the cover-plate, apply a small amount of downward pressure to the screwdriver and lever back towards the centre of the bogie whilst exerting gentle upward pressure on the cover-plate. The cover-plate should ‘pop’ off its locating catch. Repeat this for the other end of the bogie and the cover-plate should come away.
Dismantling the Bemo Wallis bogie

2. Remove the wheel-sets making sure that you note which way they fit in the bogie and that you note which axles have traction tyres and on which side of the loco they fit.

 

3. You then need to make a press tool. As I was re-gauging from 12mm to 9mm I needed to bring each wheel in on its axle by 1.5mm. This is 0.0590551181102362″ Or as makes no difference 59 thousandths of an inch.

I therefore cemented 2 layers of 30 thou plasticard together using solvent (not cement) and drilled a 3mm diameter hole through them both when they had been stuck together. I then used my digital vernier callipers to check the combined thickness and this fortuitously came to 0.059″ i.e. 1.5mm exactly.

Sticking on a backing piece now gave me a hole with a known depth of 1.5mm.

The next stage is to re-gauge the wheel-set4. Using one of my 90mm Hatakane brass bar cramps I could place the re-gauging tool over the outside of one of the wheels so that the axle pin could slide into the re-gauging tool I had just made. A gentle turn of the cramps screw was sufficient to move the wheel in on the axle by no more that 1.5mm.

The wheel-set was then removed and the operation repeated on the other side. The back to back measurement of 7.25mm was then checked using the digital vernier calipers and final sizing could then be done by tightening the cramp screw a little more if required.

The wheel-sets were then ready to be replaced in the bogies.

This is a ‘before’ and after’ shot of the wheel-sets.

5. The wheel-sets can then be returned to the bogies. Care must be taken to ensure that the electrical pickups are correctly running on the rear face of each wheel before the cover-plates are gently snapped back into place.

 

This picture shows one bogie after re-gauging and the other awaiting its turn.