[modeleng] Electric engines and batteries

Topsy is a home brew 0-4-2 (I suppose strictly a B-1) narrow gauge outline=

shunting locomotive=2E  It has followed my traditional method of design, t=
hat
is one of over-engineering!  It has a 2=2E2kW (24v 90A) forklift motor for=

its main drive, powered by 2 x 12v batteries=2E  The original controller w=
as
from 4QD, but following a disaster on my first running day (where Topsy
gave the impression of not being able to pull the skin off a rice pudding)=
,
I had to have a rethink on the electric drive!

I think I have covered this before, but to refresh your memories!=20

I have been performing some experiments -

Firstly I had to determine whether or not it was the motor (secondhand fro=
m
a scrapyard) or the controller (brand new from 4QD) that was at fault=2E

Simple solution, bypass the controller and attach 24v to the motor!  Topsy=

needed a load so I coupled her up to Stumpy and three coaches with two
passengers=2E  Stumpy uses an Eaton drive, so I engaged the dump valve=2E =
 With
24v applied, Topsy struggled=2E  She made some progress, but came to a sto=
p
on the slight gradient approaching the station=2E  So it looked like it co=
uld
be the motor=2E  I then uncoupled Stumpy and pushed him away, well I tried=
,
it was very heavy and I found that the dump valve hadn't fully engaged, so=

Topsy had been dragging Stumpy down the track=2E  With the dump valve full=
y
engaged Topsy made light work of a circuit=2E  So it was the controller, n=
ot
the motor=2E

I tried to speak to 4QD, all I kept on getting told was not to use
secondhand motors and to use their "motor current" calculator=2E  I gave u=
p=2E=20
I then phoned Brian at Parkside=2E  Very much more helpful, he guessed tha=
t
the 90A was a running current and that at start up we were look at 3 times=

that, so approaching 270A - 300A (no wonder the 120A 4QD controller curren=
t
limited)=2E  Unfortunately he couldn't help=2E  So, Topsy was stabled for =
a
while whilst I considered my options=2E

The options changed when two things happened, firstly we went to
Lincolnshire to collect an 8 week old Clumber Spaniel puppy (Fergus) and I=

took the opportunity of collecting 2 of Mike Palmers 6v batteries (recentl=
y
offered at Station Road Steam) - who was only about 10 miles away!

So, now the burning question=2E  I have two 6v batteries and one 12v batte=
ry=2E
In series they give me 24v, but I have three potential tappings and it is
this crude method of control I plan to use (I did look at carbon pile, but=

I couldn't get the carbon washers)=2E

So, do I tap it as:

(a) 6v, 12v, 24v; or
(b) 6v, 18v, 24v; or
(c) 12v, 18v, 24v=3F

My first thought is (a) as it will give a smoother start, but are there an=
y
other ideas=2E=2E=2E=2E=2E=2E

Cheers

Peter




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