RobJ's 7mm and electronics workbench - Side project, Fairmont Speeder

[RobjUK]

Some of you may remember I was enquiring about possible sources of very small wheel for an O Gauge / 7mm project last September.

Based on PatB's suggestion, I got some Marklin HO wheels and started trying to work to what to do with them...

 

When the wheel sets arrived, I found they had 2mm axles. The only tiny geared motor I could find had 1mm axles & far too narrow.

More parts searching followed, ending up with a mix of DAS87 spare shafts & sleeves, some Nigel Lawson machined adapter bushes, 1.5mm bore bearings and other various bits of shafts.

 

Then brass "chassis bashing" - The photos show the progression, spread over several months as time and parts sourcing progressed:

Edited March 27, 2020 by RobjUK
typos & spelling, as usual.

[RobjUK]

The cast front and footplates / mudguards are from a Wiseman static white metal kit, which is a slightly smaller scale, hence the split and stretched footplates. The seats are spares from some other 7mm parts I collected for my other projects.

 

Painting was rather slow - I tries airbrushing the yellow to start with, but all it did was put a faint tint over the primer, It ended up with something like five coats by brush to get a solid colour.

 

The drive system all assembled quite nicely, or so I thought - the machined 2mm to 1.5mm reducer bushes pressed in to the wheels, with a solid 1.5mm shaft at the back and some DAS87 1.5mm OD sleeves in the driven wheels, through the bearings.

 

Everything test fitted, then reassembled with locktite to permanently fix it.

 

After it had time to cure, I tried the motor and that ran nicely - but the wheels did not turn! The gearbox shaft just turned freely with no connection to the motor.

At that it went back in storage for a couple of weeks.

 

Edited March 27, 2020 by RobjUK

[RobjUK]

I never realised how strong loctite could be on something as small as this, I ended up prying the shaft and sleeve in opposite directions with two pairs of sidecutters & still needed to heat the shaft with a soldering iron to try and break down the locktite.

 

The gearbox shaft was wrecked in the process but luckily one of the DAS87 shafts was exactly the same size.

 

I took the gearbox apart and soldered the output gear to the new shaft, to try and be sure it could not come loose again.

 

The minor disaster turned out to be a benefit in a way, as I could offset the shaft and move the gearbox near one side.

I also left out the inner bearings when reassembling it - with the joints as strong as they were, it had no need of any extra support!

 

With it now turning the wheels, I added the decoder (ESU Loksound 5 micro) and some pickups.

 

The result below:

 

Edited March 27, 2020 by RobjUK

[RobjUK]

I still have a lot of tidying up and finishing off to do, plus the centre engine cover to make.

 

The sound project also needs a lot! of work - I have a new respect for the people that do them full time!

 

It runs, but so far the control is very touchy at low speed, which I think is due to it being a nominally 3V motor.

Hopefully it will improve with some tuning of the motor parameters.

 

[RobjUK]

Videos - I've only got the sound working for startup and idling so far, nothing while it is moving, so two separate clips for sound and motion:

(The driver is on loan from the Barclay project)

 

 

 

 

Edited March 27, 2020 by RobjUK