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Electric or Petrol Locomotive

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NickG:
Bogs,

I've asked questions to the sellers and the 100 Watt motor is 65mm dia and 100mm long, which sounds ideal. The 180W is 75mm dia and 122mm long which I think will be just too big for my gears and for 5" gauge. I just don't really like taking things from people if I'm not going to use them, but I could do a few experiments and return them if not suitable?

Bernd, thanks for that website link, the top motor (100W) looks the same sort as I'm looking at on ebay so that confirms the size should be just right. It should just fit between the frames of a 5" gauge but it could be a bit touch and go! If push comes to shove I might have to make a 7.25" gauge.

Thanks,

Nick

bogstandard:
No problems Nick.

I had no idea of the phyical size you needed for your loco.

What I can tell you is that if it is a fairly high revving motor, the easiest way to get spot on reduction down to the speed you require is to use a worm drive.

They work on the principle that the worm is classed as one tooth, so if you want to reduce say 8K rpm down to 400 rpm, then just divide the 8K by 400 and that gives you 20. So you use a 20 toothed gear on your drive shaft and the worm on the motor shaft. That would allow the motor to sit along the loco length rather than across it, giving a much more compact drive system. It is also a low stress method of getting speed reduction, and the motor is usually running at it's optimum speed.

It is a shame I don't have any metal worm gears in my box.

John

Bernd:
Bogs,

I'm not sure but with a worm drive your not going to get any coasting when you shut the throttle down fast. I would think that the engine would come to wheel skidding stop if you shut the power off to quickly. I think RMI here in the states uses a worm and wheel to drive there engines. You can't push them with the power off because the wheels will only skid along the track. Just my 2 pence on the subject. (is that to much money?)

Nick,

I figured that would help a bit on size. I've been looking at those motors also. I have some ideas about controllers to. I'll have to follow up on that thought when I have a bit more time to write my thoughts down.

Bernd

bogstandard:
Bernd,

You are quite right, I should have jump started my brain cell before coming out with that suggestion.

Bogs

NickG:
I was liking the idea of the worm and wheel but good point about coasting Bernd.

Another idea I had many years back (the electric loco was going to be my first ever project but I didn't have the skill to do it) was to use bevel gears from a hand drill which also enables mounting the motor longitudinally. That seemed to give about the right ratio, however, they don't appear to be that accurately made, a bit rough and ready. I guess that depends on the quality of the drill though? Any thoughts on this method?

Thanks,

Nick

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