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Saturday 4 March 2017

Lima Class 117 DMBS to DMS - Pt 1

The Lima Class 117 DMU 3 car set was always shipped with two DMBS (Driving Motor Brake Second) cars. This arrangement does not match the prototype where the trailing car is a DMS (Driving Motor Second).

The difference in window arrangement is very noticeable:
(Photo Left = DMS, Photo Right = DMBS)

There is a conversion kit available from Silverfox Models. However, I choose to use a donor Lima DMBS and do a 'cut and shut' job for my running model because the donor body panels are exact same moulding and paint finish. I was fortunate in winning on eBay someone's butchered DMBS to be the donor.

Changing the body panels at this end of the coach is not the whole story because the window next to the driver doors at the other end is narrower on the prototype than on the Lima model. The difference is not that noticeable so I'll probably leave that alone.

First I cut both body panels off the roof of the donor DMBS using a stand mounted dremel (cutting speed set to 9). The cut was made into the roof a little above the top row of rivets. The cut on the body panel was clean (thankfully) but the roof suffered some distortion along the cutting line due to plastic melt. Not sure if this is due to a worn out cutter or inappropriate cutting speed but it occurred to me afterwards that had I first cooled the body in the fridge then melt during cutting may have been eliminated.

Once the panels were cut away from the roof I lowered the dremel and passed the body panels back through the cutter to trim down to the very top of the rivets. There will be further top trimming later to achieve the final fit.

Next, I selected the window and door arrangements that could be made up into the required replacement panels.

The new panel for each side is made up from two panels cut from the donor sides. Masking tape was used to mark the cutting lines (cutting lines shown arrowed).
The cuts are made with razor saw along the vertical door edges as this will disguise the panel joins except, it is done in such a way  to retain the door hinges and hand rails.

This results in door hinges and hand rails protruding from the panel. The adjoining panel will require cut out outs for the fit.

Alignment is assured by placing a slither of paint on the end of the projections and pressing onto the adjoining panel to leave a mark for cutting guidance. The cut out is then made with razor saw and file.

The two panels to make one are glued together with liquid poly glue.
Photo shows the completed left and right side panels. The panel join is imperceptible in this photo but there is a couple of small gaps that will be filled from the rear with epoxy putty and touched up with a dab of paint.

Turning now to the DMBS to be converted the rear section was removed with dremel and razor saw. The cut at the roof line was just below the row of rivets and finished with a file to the bottom of the rivets.

The edge of the end panel and mating replacement side are chamferred at 45 degrees to disguise the join.

The photo also shows the seams on the replacement panel that is already fitted to the other side and the door handle cut out on this side ready for the implant.

The row of rivets on the top edge of the replacement panel was filed away until a good fit to the body was achieved.

The final photo shows the DMBS (top) and DMS (bottom) body.

Next job is the interior.

To Part 2.

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