Bachmann #32-135 class 4575 Prairie

[GWR-fan]

Received this loco this afternoon,  purchased as a non-runner.  I found that the motor was terminal so looked for a replacement.  After a fruitless eBay search I decided to try a small Mitsumi which I had purchased in bulk a few years ago for approximately GBP0.99 each including postage.  This motor was touted as a replacement for the Heljan Garrat loco.  My installation was crude and more to see if the motor could be fitted and how it would run.  The only mod to the motor was to reposition the worm a few millimetres closer to the motor case to align better with the Bachmann intermediate gear.  The worm diameter is the same as the Bachmann worm however the pitch may be ever so slightly coarser on the Mitsumi worm.

 

To fit the motor I glued a 0.030" plastic spacer piece to the stock motor mount then superglued the motor to the plastic spacer piece.  This looked to give me the correct height for the shaft.  The motor was then wired and run.  Performance was far better than anticipated,  running quite smoothly from a slow crawl to a more than adequate top speed on 12 volts.  I then coupled up five medium length goods wagons and ran for several minutes.  It handled the load with ease but the case did get quite warm.  I will try at a lower voltage and recheck the case temperature.

[GWR-fan]

Even at around 9 volts the motor still heats up after about ten minutes running with a light load.  At dead slow the loco "cogs" but as power is applied it smooths out.  If I was to revisit the installation I would rotate the motor 90 degrees and possibly replace the worm with the stock Bachmann part.  From my previous play several years ago with the Mitsumi motors the worm is very, very difficult to remove and the 1.5 mm shaft likes to bend easily when fitting a new worm.   I have never used one of these motors before so do not know if the can heating is normal or possibly down to the chokes fitted to the circuit board.  I do not know the function of these components or if the chokes may cause the cogging.

[Butler Henderson]

Bachmann will probably have a spare motor  http://www.Bachmann.co.uk/service-request/ 

[DCB]

I would try the stock worm on the rear end of the armature shaft and turn the motor round.  The worm profile looks a bit chunky to me from the photo and the resistance of an imperfect meshing could cause some of the heating.  A mount which gives an air gap under the motor might help. 

5 wagons is a bit of a pathetic load, Mine spend some of their time shunting 7 coach rakes and the real thing ended up shunting 12 coach rakes in and out of Paddington.

If all else fails have you thought of a little N20 motor driving a cooling fan?  Its what I planned for an overheating K's GWR 28XX.

[GWR-fan]

Many thanks gents.  I decided to revisit this chassis.  With some difficulty and a degree of applied heat I was able to remove the worm from both the old Bachmann motor and the replacement Mitsumi motor.  The Bachmann worm was then fitted and the Mitsumi motor installed.  The loco now crawls away very smoothly from rest.  I found that with six full length coaches the loco had no difficulty,  however, with eight the wheels slipped.  

 

I was reluctant to investigate a replacement Bachmann motor as the cost involved with purchase and shipping to Australia would negate any financial advantage in buying a non-runner in the first instance.  With the replacement Mitsumi motor costing me under $2.00 it was worth it to get a functional loco.   Of all the many, many, many pre-owned non-runners purchased (at least 100 models) I have had two Bachmann motor failures (both GWR pannier tanks), a Mainline 43XX ringfield and a Hornby King 5-pole.   

[The Johnster]

Have you overcome your heat problem*?  If so you are definitely on the winning side.  The heat, and cogging at low speed, suggests to me that there was something retarding the motor and creating back EMF, generating the heat.  Mine is capable of working an auto train of two very heavy cast whitemetal K's A31 kits, complete with internal seating and cab details, which I reckon to be equal in weight but perhaps with less rolling resistance (they are on very free running Stafford Road/Shapeways printed bogies) than my 11 wagon and a van loaded mineral train, capable of being hauled by the fundamentally similar mech in a Baccy 56xx.

 

If the loco hasn't been run much by the previous owner before the original motor cooked, the wheel rims may not have worked in, and haulage will increase over time; I have found this will all new or newish Baccy locos.  I've never had any issue with a Bachmann motor, but as you will realise my loads are light and on a short BLT they do not have to work hard for a living.  Sounds like life is tougher on your layout!

 

 

*Just realised that the question may look a bit insensitive to someone in Oz at the moment!  Hope you are well away from the flames and coping with the hot weather.

 

 

Edited December 30, 2019 by The Johnster

[John Isherwood]

On 28/12/2019 at 05:32, GWR-fan said:

With some difficulty and a degree of applied heat I was able to remove the worm from both the old Bachmann motor and the replacement Mitsumi motor.

 

 

A (probably) useless piece of information, but the Mitsumi worm is a match for a Hornby Dublo worm wheel - which was very useful when I was remotoring an HD Barnstaple.

 

Regards,

John Isherwood.

[GWR-fan]

John,

         thankyou for the information,  I am sure that some one with HD will find the information useful. 

 

Johnster,

         after replacing the worm with the correct pitch Bachmann gear the heat was less but the motor still heats up.  After some running no heat could be felt transferred into the body.  The motors are remarkably smooth and will pull away with just a couple of volts.   As regards the numerous bushfires that seem to stretch from the Queensland border down around the southern coastline and across to Western Australia,  many of the mega fires are relatively close to me, living in Sydney.  Ash has fallen on a regular basis across most of the Sydney basin and the sun takes on a red glow each day giving the impression of a Martian atmosphere.  One "advantage" is that the smoke haze does keep the temperature down slightly as the fires coincide with an unusually very hot summer and we are yet to the early couple of months of the new year when temperatures will soar.  Over 1000 homes lost in the last two months along with hundreds of outbuildings, sheds, etc. and unfortunately to date approximately ten fatalities with nearly half being volunteer fire fighters.  

[The Johnster]

Stay safe, mate! 

[Virgil]

I too have noticed that the Mitsumi I fitted as a replacement for a K's HP20(?) motor gearbox runs very hot, uncomfortably so. At present driving only a replacement brass gearbox of unknown manufacture, see photo. So I'm about to try an open frame motor of similar dimensions to see how that fares.

Any ideas on the manufacturer of the open frame motor and also the gearbox?