DCC Loco Conversions - 39 - Tri-ang Hornby Power Bogie X.3710 (X.337,X.213)

Discussion in 'DCC Control' started by Jim Freight, Aug 16, 2022.

  1. Jim Freight

    Jim Freight Full Member

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    This article applies to the X.3170 power bogie fitted to Hymek R.758, but is also applicable to similar power bogies, for example, although not a comprehensive list :-

    X.337 fitted to the
    Brush Type 2 (Class 31) R.357
    English Electric Type 3 (Class 37) R.751
    N.S.W.R. Diesel Locomotive (Aust) R.307​

    X.213 fitted to the
    EM2 Electra R.351​

    The two collector units (phosphor bronze pickups) are identical parts for both sides of a bogie so if you want to reverse the modification to the collector unit just swap them over.

    Four simple modifications are required to isolate track power from the brushes and attach a decoder.

    1) cut off the tab from the collector unit that makes direct contact with one brush arm.
    2) add packing to the top housing hole to replace removed tab .
    3) insulate both ends of the brush spring and add loose fitting sleeves for strain reliefs.
    4) Prepare the decoder connection points for soldering decoder wires.

    I will now go through these in detail.

    The first two images show the power bogie after servicing and testing ready for conversion.

    1 DSCF0766.JPG

    2 DSCF0768.JPG

    1) The collector unit to be modified is removed from the top housing,

    Remove the brushes and then release the nut on top of the bogie, remember the sequence of parts, the images above will help.

    Taking care not to damage the raised pips of the top housing, as the plastic can be quite brittle due to age, (the pips were already missing at one end of this bogie) release the collector plate to be modified. Easier if the housing is removed from the bogie but this may adversely affect the magnets strength requiring re-mag or NEO replacement.

    The tab (circled in red) is part cut off

    3 DSCF0770.JPG

    4 DSCF0771.JPG

    and then finished with needle files to emulate the shape of the collector plate near the other brush arm.

    5 DSCF0772.JPG

    6 DSCF0774.JPG

    2) Notice that the brush apertures in the top housing are different, the one that the collector unit tab entered is cut back so that the brush arm was pressed against it, this needs filling with packing of some kind, either glued, screwed or wedged.

    Holes are 0.1 inch and 0.15 inch wide looking from the bogie end (note these would have been designed to imperial units), the difference of 0.050 inch is close to 1.25 mm.

    Gluing could be difficult given the apparent type of plastic used for the housing, alternatively solder some .050 inch shim to the back of the brush arm for that side, which approach you use depends on your resources and how often you may want to change the brushes. However that may use up too much of the locating curve of the brush arm.

    The option I chose was to use was fitting a short length of grommet strip, this is a polythene type material in a square U section for lining cut outs in the panels of electrical equipment to protect wire insulation from chaffing. Just about the right thickness and holds the brush in a good position relative to its opposite number, it was necessary to tack into position with a little cyano glue to stop it falling out when inserting the brush arm.

    This discontinued grommet strip was obtained from RS (Radio Spares) as RS 548-546, alternatives are available, e.g. Order Code 49-7811 from Rapid Online may be a suitable alternative Ref 39.1, but as I still have plenty of the RS part in stock I am not likely to find out. However Rapid Online gives the dimensional data for their strip.

    Split PVC conductor insulation from e.g. power mains cable may also be suitable.

    7 DSCF0776.JPG

    3) Remove the original insulation sleeve if it looks to be in a poor state and fit new insulation tubes to both ends of the brush spring, I use PTFE, if you use PVC then remove them while soldering decoder wires to the brush arms and ensure they are refitted afterwards.

    Add loose sleeves (unshrunk heat shrink) on the vertical parts of the brush spring to act as strain reliefs when the decoder wires are attached.

    8 DSCF0788.JPG

    4) Clean up and tin the tabs at the end of the collector plates from which track power is to be taken to the decoder, and the tops of the brush arms to receive motor drive from the decoder. Which tabs will depend on the body shell or chassis of the loco the bogie is for and where you intend to fit the decoder.

    9 DSCF0789.JPG

    10 DSCF0790.JPG

    Summary

    This conversion is relatively straightforward, remember to ensure that if the magnet is removed to either use a keeper or re-magnetise when refitted between the pole pieces but before adding the top housing.

    I would recommend fitting of metal wheelsets and power pickups to the un-powered bogie, an example of this is shown in my conversion of a Hymek R.758, ref 39.2 which this particular bogie is part of.
    Discussion is always :welcome:

    Jim

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    References

    39.1 Rapid Online

    https://www.rapidonline.com/
    item: HellermannTyton 251-10109 G51P-A-PE-NA Flexiform Edge Protector Natural
    Order Code: 251-10109

    39.2 Tri-ang Hymek R.758 Conversion

    https://platform1mrc.com/p1mrc/index.php?threads/dcc-loco-conversions-40-tri-ang-hornby-hymek-r-758-1968.6117/
     
    Last edited: Feb 24, 2024

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