From: Al Sandrini Date: Thu Sep 27, 2001 5:02 pm

Subject: Remotoring AHM's Minitrain (HOn30) Plymouth

I just recently started stocking some of the Mashima 9mm motors for

repowering some of the older HOn30 locomotives. The first unit that I

remotored was the AHM Minitrains HOn30 Plymouth. The following how I

did my installation:

ATTENTION: The first thing that is necessary before starting this

project is to be sure that the gears in the AHM Minitrains Plymouth are

not split. If you have a gear problem, the motor will not help the

engine at all. Check the gears by taking your strongest magnifiers and

checking the gears on the axles for splitting. The crack will appear at

the valley between the teeth. If you need to, clean the teeth very well

with an alcohol based cleaner. If the gears are fine, proceed. If not,

you need to purchase a regear kit for the AHM Minitrain locomotives.

IF YOUR GEARS ARE SPLIT OR CRACKED

A regear kit is offered by NWSL and is stocked by B & F Hobby Shop,

Portland Locomotive Works and can be special ordered through any hobby

shop. This gear set includes two new steel worms that go on the long

drive shaft and two new delrin worm gears that go on the axles. The

gears do not come with any instructions, but Jeff Schumaker has written

a detailed instruction sheet to install these gears and do some shimming

to make allowances for slightly different diameter on the new gears.

This sheet is available with the gears from B & F Hobby Shop and

Portland Locomotive Works.

INSTALLING THE MASHIMA 9MM X 20MM MOTOR

Motor Specs

The Mashima 9x20mm motor turns 14,000 at 12 volts. It has a 1.5 mm

shaft and sells retails for $29.95.

Step 1

Remove the body from the Plymouth carefully by inserting a flat

screwdriver between the sides of the cab to loosen it from the frame.

Gently pull up until it releases.

Step 2

Remove the motor by gently bending out the brush contact pieces, then

gently rock the motor until it is free and then pull straight back until

it clears the gear tower.

Step 3

Check the position of the gear on the motor. Take note of the distance

between the motor and the gear. Also note how much shaft protrudes from

the gear on the side away from the motor.

Step 4

Remove the gear from the motor shaft by gently pulling on it with your

fingers. It should come off without too much effort. If not, use a

gear puller. DON'T PRY WITH WIRE CUTTERS OR PLIERS AS IT COULD DAMAGE

THE TEETH ON THE EDGES OF THE GEARS. These gears are not replaceable.

Step 5

Measured the length of the original motor shaft. Transfer that length

to the new motor shaft and cut the shaft to that length with a Dremel

Motor Tool. Be careful to not cut too short. It is better to cut it

slightly longer and then gently shorten it to the correct length.

Step 6

The motor shaft on the original motor is smaller than the shaft on the

new motor. The hole in the gear needs to be enlarged to fit on the

1.5mm shaft. I took my numbered drill set and found one of the drill

sizes that would just fit through the hole and then selected the very

next size to ream the hole out. I tested the new sized hole on the

shaft and it was very snug, but did press on. The drill I used was a

#54, or .055". This gave me a hole size of 1.397mm to press on a 1.5mm

shaft. IF YOU USE A #53, IS IS .060 AND IS EXACTLY 1.5 AND COULD BE TOO

LOOSE.

Step 7

Press the gear onto the shaft, leaving the same spacing between the

motor as the original. Set the motor against the gear tower (WIDE SIDE

DOWN) and the gears should have the correct mesh. To test, you can bend

the tabs on the Mashima over the brush contacts from the AHM loco as a

temporary connection, hold the motor square with your fingers and apply

a low amount of power with jumper wires. The motor should turn nice and

free and the gear noise should be quiet. If the gears make a lot of

chatter, there may be too much mesh and you may need to add a piece of

plastic shim material under the motor. I would suggest a piece of .003

plastic stock for a starter. My loco did not require any shimming.

Step 8

Square up the motor and hold in place with some rubber bands and make

sure that after the rubber bands are in place that the motor is still

square. Once the motor is square, use a little RTV Silicone on the

floor of the chassis and the magnet end of the motor to hold in place.

Let the Silicone cure for about an hour before you remove the rubber

bands and test the engine. If everything runs fine, go to the next

step. If not, go back and shim the motor as necessary, or if the

position of the motor moved, remove the silicone and reposition the

motor and do again. It is critical that the motor shaft be in alignment

with the center of the chassis.

Step 9

Your Plymouth body will be about .002"-.004" to narrow to fit over the

width of the motor. Dremel makes a 1/4" sanding drum which you can use

to thin out the inner walls of the body. Do this in steps so that the

body fits snug over the motor. This tight fit will also help keep the

motor in alignment. Make sure that you remove enough of the material so

that the body is not forced to bow outward, but not so much that it does

not touch the body.

Step 10

Test run your repowered locomotive and see the improvements

ADDENDUM

There are two more things that can be done to improve the running of

these little locomotives:

1. You can add A-Line's "lead putty" to the rear of the cab and in

front of the body. You can add almost a ounce of weight and it will

make a difference in pulling power and electrical contact. If you add

this material, you may need to shorten the rear drive shaft.

2. You can add a brass flywheel to the rear shaft. At this time, I

cannot find a commercially available flywheel to fit this shaft and

clear the chassis. I am having some of these turned just for this

application. If you do add a flywheel, you can remove some of the lead

putty from the cab area.

Good Luck and Happy Modeling

Al Sandrini