Hornby class 25 susu motor

[GWR_fan]

I had a cantankerous old class 25 that no matter what I did I could not get it to run reasonably well. I rebuilt the motor and added pickups but it still performed poorly. With nothing to lose I fitted a Susu motor. These are CD drive motors and while really only for a 3v - 6v operating range. they spin at a higher RPM so minute power is only required to get good speed.

Unlike the Model Torque motor these do not have a mount bracket, although from memory 'Bufferstop' fitted one to a ringfield housing using the threaded insetrts in the motor casing. The seller recommended supergluing the motor insitu and to date I have fitted several motors to Lima stock with no problems encountered.

To fit the Susu motor the ringfield housing brass bushing must be removed and the hole enlargened to 0.250" approximately to allow the motor mount spigot to seat the motor in the ringfield case. A problem arises with the shaft diameter. A three pole syhaft is 0.095" whereas the Susu diameter is around 0.085" and has a flat section milled on it. Before fitting the pinion a small piece of tubing may be fitted onto the Susu shaft to space the pinion gear at the outer extremity of the end of the shaft to assist positioning of the pinion once fitted.

To fit the 11 tooth Hornby brass pinion from the three pole armature, I cut a tihin piece of styrene 0.020" thick to 'fill' the flat section on the Susu shaft and placed the pinion gear over the shaft. A small sliver of styrene was then used to 'fill' any remaining clearance. The pinion was then superglued to the shaft. Possibly one could apply solder to the inside of the brass gear and then drill out to suit the Susu shaft diameter.

If screwing the motor to the ringfield housing then one would temporarily attach now to ensure that the screws will not interfere with the intermediate drive gears. For my installation, I intended supergluing the motor and so assembled the gears and then applied superglue to the motor case and then inserted into the housing, aligning the pinion gear on the motor shaft with the drive gears to ensure that no binding was occurring while the glue cured.

I then wired up the drive and watched a now very happy class 25 trundle around my test track. It happily hauled around fifteen waggons with ease at a dead slow pace. The seller advised when I questioned the application of higher voltages to the motor and he claimed no mechanical/electrical issues other than the motor may run hotter than normal. For analogue operation there is really no need for more than a few volts to use the loco as it responds perfectly at lower voltages. I as yet have not decoder fitted a Susu so do not know the consequences of full track voltage to the motor.

Once you start the Susu install you cannot back track as the ringfield housing cannot be uses again with a Hornby armature due the mods carried out. I am extremely happy with the analogue performance to date. The loco moves off slowly and runs a lot better than when it had the three pole armature.

[Bigmet]

I'd be cautious about DCC, because a decoder applies full rectified voltage in pulses. With the motor stationary you can burn out the metal wiper brushes that are typical in these motors very quickly, if you are applying twice (or more) the specified 6V maximum.

[GWR_fan]

Bigmet,
analogue is their main attraction. The locomotives that I have put these in are not worth the price of a decoder so will remain as analogue only.