Re:Railmotor 2
ge_rik said:
That's really helpful - thanks. Yes - it is the bog standard IP Engineering gearbox - I assumed it was 40:1 - which is what it says on their website -
Rik,
I'd noticed that, but it must be a typo, as the gear wheel is too small for it to be a 40:1 reduction, without adding another gear stage.
For any simple worm drive gear box, the reduction is calculated by counting the no of teeth on the worm wheel and dividing that by the no of starts on the worm. Ivan uses standard off the shelf 0.5 mod plastic gears and the worms are single start, so the reduction can be worked out easily by counting the teeth on the gear wheel and he only sells 16 tooth and 30 tooth gear wheels.
The large IP motor is an MM28, or the equivalent RE280, type. These are nominally a 3-6V motor that develops maximum power at about about 9000-10000 rpm.
My railmotors have 24mm wheels and 4 x 1.2V cells, so travel at around 25 scale mph at their maximum speed setting. I usually run them at about 2/3 speed so the motor and gears aren't howling. In the photos the models have the original 20mm dia wheels, but they've since been increased to 24 mm dia, mostly for appearance, but with the bonus of a higher top speed without having to find the space for another battery cell.
ge_rik said:
Hopefully a li-po will have a 'flatter' decay rate than alkalines (yes?).
The discharge curves for LiPo that I've seen aren't markedly different to NiMH. The r/c car and aircraft modellers love them because they have about twice the energy density as NiMH cells.
Lower weight for the same power output isn't an important consideration for model railways, the opposite in fact. We need as much weight as possible for traction purposes, given the co-efficient of friction for metal wheels on metal rails is only about 0.2. The lower self discharge rate of LiPo technology is useful though, especially if the model isn't run very often.
ge_rik said:
Another option I'm considering is making a baggage van to go between the two cars over the top of an LGB or Aristo motor block. Then I'll be certain to have the oomph I need (and maybe more besides).
You'll certainly get a more reliable and powerful drive by going down that road.
My main interest is building models and since I can give a cat lessons in being stubborn/patient, my normal reaction would be to keep fiddling until it worked.
From what I read of your railway, you are more of an operator than I am, so a reliable solution is probably the more important outcome for you.
Regards,
Graeme
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