[modeleng] Re: Motor requirements

Thanks Alan - I thought that I might be struggling with the 6 volt motor, 
but it was the size and weight of the batteries that appealled to me. I am 
not sure about passenger haulage at this stage though, as the principal 
challenge will be to make something that actually moves, under it's own 
power if not exactly it's own steam ... ;-) The 3-4 mph that you quote is 
the crucial thing at the moment however, just so that I can work backwards 
(like my spelling that I have just had to delete ... <sigh>) to sort the 
required rpm's out.

Tony.


----- Original Message ----- 
From: "Alan Stepney" <alan@xxxxxxxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Tuesday, May 29, 2007 9:26 PM
Subject: [modeleng] Re: Motor requirements


> My initial thoughts are:
> A toothed belt for the drive. Available in a wide range of sizes, they 
> allow
> simple adjustment for tension thus facilitating wheel movement etc.
>
> As for speed, 3 -4 mph is about all that you will need as a maximum. There
> are lots of options for motors, and of course for batteries. Probably best
> to decide on one, and then select the other to suit.
> At a very rough guesstimate, you will need at least 1/8 HP, preferably 
> much
> more, to use it for passenger haulage.
> (depending upon gradiant, track and wagons and many other factors.)
>
> I reckon 6 volt is too low and would look at 12 volt. Thinner cable and
> simpler controls with the lower currant compared to 6 volt at the same
> power.
> For the motor, my personal choice would be ex-car motors of some sort. 
> But,
> this depends upon what you have / can scrounge.
>
>
> Alan Stepney
>
> http://www.alanstepney.info
> Model Engineering & steam engine information pages
> ----- Original Message ----- 
> From: "Tony Wells" <oaksfield@xxxxxxxxxxxxxxx>
> To: <modeleng@xxxxxxxxxxxxx>
> Sent: Tuesday, May 29, 2007 7:50 PM
> Subject: [modeleng] Motor requirements
>
>
> 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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