[modeleng] Re: Motor requirements

At the 2½" Gauge Rally on Sunday one of the chaps had a little electric 
0-6-0 shunter. The motor used was a 12volt 100W motor from an electric 
scooter. The motor was mounted vertically in the cab and used the bevel 
gears from an angle grinder to turn the drive through 90°. The final 
drive was by chain to all 6 wheels. The speed control was by a 35amp RC 
unit and as there was no room in the cab for any controls, you had to 
drive it by radio control as well!
The scooter motors appear on Ebay regularly and seem to range from 
80Watt to 120Watt in the 12 volt versions and more in the 24 volt types. 
The batteries used in the little shunter were only 4.5Amphour but it ran 
for quite a time as people queued up to have a go. Had a fair turn of 
speed as well.

John

Tony Wells wrote:
> Well, I have finally surcumbed to the lure of the loco, and gone loco! My 
> 3.1/2" gauge train now has a chassis, and both front and rear bogies, all in 
> wood in true Richard Blizzard fashion though, so perhaps I should not be 
> mentioning it here .... <VBG>
> It is a scratch built 4-6-2, with 3-axle tender, all to be made from polished 
> hardwoods, and not "hard words" as I just mistyped - they will come later! As 
> I am working from the bottom up, I need to decide on the drive train next, so 
> as to be able to design the body around it. The idea is for it to look like a 
> steam loco, but be electrically driven, but more Basset Loake than Hornby 
> Triang, hopefully! With an overall length of nearly 30", at least I have 
> given up on the Basselt Loake clockwork motor idea though .... I am therefore 
> thinking of putting a battery (or batteries) in the tender, with a disguised 
> power cable through to an electric motor in the loco proper.
>
> Chatting to Al and Tel off list, I have come round to the idea of either a 
> cordless electric drill or a recycled windscreen wiper motor, though whilst 
> out shopping today, I saw some of the big 6-volt zinc lamp batteries, the 
> ones (very) approximately 2" square and 3" high, for only £2 each and so may 
> look into a 6-volt motor as well. I had thought about trying to find such as 
> a small motocycle battery to fit into the tender, but decided that the 
> additional weight made matters worse, not better, taking me into the lands of 
> diminishing returns, incidentally. My problem is that while I have the bit of 
> garden where the fruit trees are for some track, it is only 30' x 40' at the 
> most, and so it would be a very twisty one at this size, round those trees, 
> and so what design speed should I aim for please, so that I can determine how 
> powerful a motor will be required?
>
> >From my working days, the clearance times for pedestrian crossings were 
> >based on 1.2 metres (4 feet) per second, so should my train go faster or 
> >slower than that, bearing in mind the lack of long straights where an 
> >express could be wound up to maximum speeds? Should I be able to keep up / 
> >catch up with it in the event of an accident, such as when Unka Jesse fell 
> >off his and could then only watch it disappear into the distance until it 
> >(literally) ran out of steam ? As my driving wheels are 2.1/2" diameter, I 
> >did a bit of mental arithmetic to work out that at 3mph, a brisk walking 
> >pace but not rushing, the wheels would be doing around 225rpm.
>
> If I was to use a cordless drill with a natural speed of 900rpm to 1,000rpm, 
> it would need to be greared down rather than using the standard sort of speed 
> control, as these are inclined to over heat if used for a prolonged period of 
> time. I would need a pulley ratio of 4:1 if I was to use the flexible drive 
> belt that I am looking for. 1" to 4" would give me problems in housing the 4" 
> pulley, whereas 1/2" to 2" might well give me slippage problems on the 1/2" 
> one, however. Physical gears has (for me) the problem of achieving alignment 
> as well as maintaining it due to possible moisture movement of the timber 
> frame and chassis. This as well as being far noisier, though nylon gears 
> might get around that if they could take the loadings.
>
> I am open to any help, ideas and suggestions that the Group may come up with, 
> please, but precision engineering is just not possible for me I am afraid, as 
> bittter experience has shown far too often.
>
> Thank you,
>
> Tony.
>
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