Converting Bachmann SECR Coaches to EM Gauge

[Richard StevensonParticipant]

A few years ago I converted two sets of these coaches, the first in SR Olive Green and the second in SE&CR Dark Lake livery.

On removing the wheelsets and supporting metal pressings I found that there was a conical hole with a vertical slot in the plastic sideframe. At the time I doubted that this would provide a satisfactory start for accurate drilling for a top hat bearing and thought it desirable to retain the metal pressings which carry the wheelsets. I was able to bend these sufficiently to just clear the faces of EM wheel sets. There was sufficient thickness in the plastic bogie frames to allow the frames to be trimmed back enough to accommodate the modified metal pressings, carefully preserving the locating pegs in order to maintain alignment. Shorter than standard axles, about 25.25 mm long, were required, which were produced on my lathe.

Bogie as purchased

Conversion retaining the metal pressings with trimmed sideframes and shortened EM axles.

More recently I gave some thought as to whether a pin point bearing conversion was possible without the use of a lathe. An opportunity to purchase a brake third in SECR dark lake at a pensioner friendly price was an incentive to experiment.  It occurred to me that wheelsets removed from Hornby Maunsell coaches had slightly shorter than standard axles and might be suitable. The coach arrived the day before the Southampton show. I was manning the EMGS stand and a demonstration of the conversion seemed to be a good idea. Once set up I got to work, dismantled a bogie and took some measurements. It became apparent that there would be very little thickness left in the bogie frames. I concluded that this approach was a non-starter and decided to think further about fitting top hat bearings.

Unfortunately, the Knowle bearing tool is too bulky to fit within the bogie frame and cannot be used as supplied to drill out the bearing holes. The central cylindrical portion of the tool would have to be reduced in diameter. I could easily do this on my lathe, but I was looking for a method which did not require lathe work. Could I come up with some other means of holding the short twist drill supplied with the bearing tool?

It occurred to me that the worm from a gear set for a 2 mm dia. motor shaft might provide the answer. I had a set to hand which had not already been installed in a locomotive. Its outside diameter was about right to align the drill with the hole by resting it on the top frame of the bogie. How to rotate the drill? I could not get a grip on the worm, but it proved possible to rotate the drill by gripping it with a pair of flat nosed pliers.

Positioning of worm with drill and modified drill for recess.

The width inside the bogie frame is 22 mm, sufficient to accommodate an EM gauge wheelset, but the flange of the bearing has to be recessed into the side frame by about 1 mm. I ground up a broken drill to do this. It was quite effective at removing material, but final tidying up with a craft knife was necessary to get the flange to seat correctly. The existing vertical slot was extended downwards to allow the bearing to be levered out if the recess for the flange was found not to be deep enough. It also served to reduce the amount of flexing required to insert the wheelset.

Rotating the twist drill with pliers was effective but somewhat tedious. For any future conversions the bearing tool will receive the lathe treatment!

Top hat bearings fitted and first wheelset inserted.

Completed bogie.

For my earlier conversion method it might be possible to shorten the axles without using a lathe by cutting an appropriate amount out of the centre and reassembling with some 2 mm bore tube.

Both methods are capable of producing a good result.

[Nigel BurbidgeParticipant]

Thanks for sharing your experiences Richard.  I may pick up some Bachmann Mark ones and Thompsons so will bear this in mind when looking to convert them to EM.

Nigel

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