EM Lima Class 37 Conversion to EM with Strathpefferjunction LA4 Kit and 12mm CD motor

[NFWEM57]

I recently acquired a nicely detailed and weathered Lima class 37 with the original motor bogies for £37 for conversion to EM gauge.  Although I had a new Class 37 Hornby Railroad chassis and bogies, and had converted a Lima Class 47 variant to EM recently using Railroad chassis and bogies, I wanted to keep the original chassis will all its detailing but did want to reduce the considerable running noise and I decided that a CD motor conversion was the best option.  The Strathpefferjunction Lima LA5 conversion kits for CoCo bogies uses a smaller (9mm) CD motor (9mm) to aviod the CD motor fouling the middle axle.  This means less power, and therefore drawbar bull, and possibly the need for voltage droppers.  However, for an EM gauge conversion, it is possible to fit the larger CD motor (12mm) if the motor is modified slightly and use the generic Strathpefferjunction Lima LA4 generic conversion kit instead which comes without a motor.

 

The conversion is undertaken as normal with the only modification required being to remove the casing overhang on the lower part of the CD motor and the addition of shim washer on the central axle.  An Ultrascale Lima 6 Axle Pack B set was used for the replacement wheel set.  Protrusions on the non gear side of the existing power bogie must be removed as they prevent the correct back to back being set irrespective of motor change.

 

Although Strathpefferjunction do sell 12mm CD motors separately,  I had a set 6 CD motors from an educational motor generator experiment set for children that had been sat 'gathering dust' for some time.  The motors are 12v and measure 12.4mm in depth.  The 2mm shaft protrudes by 8.75mm but this does not need trimming as the excess simple passes through the existing motor housing and does not cause fouling.  On the back of the CD motor, the case overhangs the motor rear by 0.75mm and it is necessary to remove this overhang on the bottom quarter of the motor.  I used a small file and filed away from the centre of the motor to prevent filings entering the motor ventilation holes.  A little of the rear casing can also be removed if required.  Before and after shots below.

 

    

 

It is now a matter of temporarily putting the motor in place in the LA4 mount and checking the clearance between the central wheel and the motor casing.  I used two 1 mm thick 1/8" shim washers on the side opposite the gears to ensure the wheel did not foul the motor casing but, in hindsight, could have used 1.5mm.  After checking for free running, permanently fitting the motor with its gear wheel and the central wheelset, the remaining two axles are fitted and similarly checked for free running.  The back to back was set at 16.5mm but with the Ultrascale wheels a back to back of 16.6mm could be used whilst maintaining a wheel check gauge of 17.2mm; every little helps.  There is limited side play on all the axles but the minimum radius on my planned EM layout will be 48", much more on the scenic section, and on my test track it is a minimum of 32" but 34" for the outer track;  the locomotive it will not encounter 2nd radius curves (18").  The complete bogie is shown below.

 

    

 

Bogie eased out to show fine (cigarette paper as the late Iain Rice would say) clearance between middle wheel set and new CD motor housing.

 

 

Prior to conversion the locomotive weighted 400 grams (205 grams power, 195 grams dummy) and, with its traction tyre fitted wheels, had a drawbar pull of 110 grams; at 55%, a low conversion, 75% expected.  The weight of the converted loco was 375 grams with 195 grams on the power bogie and 180 grams on the dummy bogie.  Draw bar pull was measured at around 30 grams and quite low at 15%.  Adding finger tip weight  considerable increased draw bar pull and so more weight might need to be added toward the power bogie end.  On test, light loco, the conversion ran smoothly around a 34" radius EM gauge test track and through a British Finescale B7 and Double Slip.   An additional 65 grams of weight was added toward the power bogie end of the locomotive with 240 grams on the power bogie and 200 grams on the dummy bogie; total 440 grams.  Draw bar pull increased to 40 grams, a minor improvement to 17% but no the nominal expected 60 grams (25%).  Locomotive has been converted to  has been DCC with red and white running lights .  Converted loco images below.

 

  

 

On test the DCC converted locomotive hauled 6 Mainline Mk1 coaches (total weight 900 grams) with ease and attained a scale speed of 90 mph (measured using a DRM Speedometer SPC100R) at speed step 16 of 28 using an unconfigured LaisDCC 8 pin direct decoder.   A LokPilot 5 Basic will be fitted in due course and auto tuned to initially set up the decoder before other settings are adjusted.  Video of converted locomotive and 6 Mainline/Replica Mk1 coaches at link.  There was only a slight warming of the motor after 30 minutes of running.

 

 

I will be undertaking a similar conversions on a Lima Class 52 and (hopefully) a Mainline Class 56 (using a Hornby  conversion kit), both with Ultrascale wheel sets.  I have several R758 (Ringfield) conversions to undertake as well but the BoBo's conversions accept the full size CD motor without issue.

 

I have another Lima Class 37 in mint condition which will be receiving a replacement Hornby Railroad chassis and bogies, running, marker and cab lights and a 21 pin DCC fit.  The bogies will have Alan Gibson wheels fitted, gauged for EM, in place of the RTR ones with traction tyres.  I'll upload if there is interest, I successfully converted a Lima Class 47 to EM in the same manner recently. 

 

Patrick

 

Edited June 9, 2023 by NFWEM57
additional info and spacing adjust

[KeithHC]

Well done for one of the longest thread titles. Please keep the conversions going on here. Any info I can gain about conversions the better.

 

Keith

[NFWEM57]

Guess I could shorten it to - Lima Class 37 EM Conversion Tips.  But it is an accurate description to attract interest across several modification areas..!  Read the title, not for me, move on..! 🙂

Edited April 7, 2023 by NFWEM57
additional info and typos