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Re-Motoring a 16.5mm gauge
Class 03xxx / 04xxx
Drewry shunting locomotive.
This class 03 shunting locomotive is owned by K. Newell and is allocated to Otterbank shed on his 16.5mm gauge OO finescale (Peco Code 75 track/pointwork) home layout, Wyndy Lane & Otterbank. A short out & back branch line with a small station at each end and a short siding about half way between.
Kim's first 03 was returned to the supplier due to very poor running, (motor and wheelset binding, bent axles/wheels not concentric) a replacement was sent which also ran very badly, stalling at low speed, producing a lot of vibration and noise.
The locomotive was stripped down and the wheelset checked, the wheel tyres are concentric with the stub axles but the wheel flanges are not concentric with the wheel tyre, this is a slight fault and does not affect the free running of the wheelset on code 75 fine track and pointwork. We turned our attention to the motor and the fault was immediately noticeable, the motor windings were loose! The fine wire windings of motors ar normally held in place with a resinous substance to ensure the armature stays balanced, this particular motor appears to have missed this important process and the windings were free to shift having a negative effect on the armatures balance, this accounted for the excessive vibration of the loco when running. Two short lengths of the winding wire were protruding from one side of the armature core assembly making occasional contact with the locomotives chassis block, this accounted for most of the noise. If this motor had continued to be used the insulating layer on these stray windings would have worn off and a short circuit would have occurred. The motor was scrapped with only the brass worm gear being retained. A Mashima can motor was chosen as a replacement due to their reasonable cost and performance characteristics, low current starting and reasonable torque at low speeds. Fitting the Mashima motor required some modifications to the chassis, a small amount of material was removed from both halves of the chassis unit to allow for the new can motor and some insulating material to be fitted.
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Original motor as removed from loco. The armature windings were loose with two loops of the coil windings protruding from the armature assembly, these stray wires were contacting the chassis sides causing noise and vibration. If this motor had continued in service it would have further damaged the insulation on the stray windings and caused a short circuit between the stray winding and the chassis. |
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Stray winding on other side of armature. This winding moves visibly outwards from the armature when power is applied, this is no doubt due to centrifugal force acting on the loose windings. The motor shows no signs of any form of retaining compound to hold the windings in place. Any attempt at balancing such a motor would make it obvious that the core weight is unstable. I can only believe that this unfortunate motor somehow missed the usual quality assurance tests. |
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Chassis during removal of unwanted material to allow for the larger motor, this was performed with a small hand held power tool with milling bits to remove the bulk of the material, the rough surfaces were then finished with small hand tools. |
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Test fitting motor in first half of split chassis block to check clearances. |
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The process of milling away chassis material and test fitting the motor was repeated until the motor fitted well but allowing a little extra space for inclusion of rubber and circuit board insulating spacers. |
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The motor power feed tabs are curved to provide some outward pressure onto the shassis halves when assembled ensuring a good electrical connection. |
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Removing a few high spots before fitting insulating spacers. |
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After some finishing with fine files and some 1200 grit abrasive paper. I also used a curved file to get into some of the awkward to reach corners. The motor shaft will be shortened on the next one obviating the need to mill a channel in the end of the chassis. |
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Chassis re-assembled with Mashima Motor fitted. The piece of PCB material in the gap at the top of the chassis unit acts as an insulating spacer anh holds the motor shaft and worm gear in allignment with the reduction gear (white plastic gear seen in above photos). |
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Rebuilt model with green liveried body. coming off shed at Wyndy Lane. (K.Newell. July 2002) |
With the Mashima motor fitted this loco starts and runs at a scale walking pace and is now capable of reliable shunting at low speeds, hauling a heavy load without trouble. The real 03 and 04 class locomotives were not liked by drivers as they had a tendency to slip when pulling away and more worryingly when braking with a load making them somewhat troublesome to drive.
A new 04 has since been purchased which runs quite well at high speed but is unreliable at less than a scale 40mph. The 04 has only minor aesthetic body differences and uses the same chassis unit & motor as the 03, the motor in this new loco also has the armature windings free to move although they are within the armature assembly this loco will also be fitted with a Mashima can motor before being passed into service for use as a shunter/station pilot.
Both the 03xxx and 04xxx have now be fitted with `Kadee' buckeye couplers to suit the rolling stock on Kim's Wyndy Lane & Otterbank layout. These are very easily fitted to the 03/04 locos allowing stock to be remotely uncoupled with either fixed magnets or electromagnets fitted between the running lines. Once uncoupled the stock can be shunted into position and left standing where required.
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