Postby essdee » Tue Jan 26, 2016 12:03 pm
!!!!! Curses, Moriarty - found out! Such carelessness..... I should have pointed out the P4/EM factor - you get the extra piece of cake, Philip.
Knuckles - yes, I admit it looks a handful, and figuring out the first installation took a while. Now it comes almost naturally! Think of these three elements to it:
1) The easy bit, the TendeRiser; just follow Chris's instructions, for using the short setting, ie. no idler axle and remove the bottom section of the gearbox frame - snaps off along a half-etch, easy (I assume your pre-Group tender will be relatively low in profile). If using CSB suspension, or with narrower EM frames, you will probably also need to remove from the TendeRiser frame the redundant 'ears' for the offset idler gear, which may foul the CSB wire on one side.
The flexible coupling is Ripmax aircraft fuel line, 1.6mm ID and a tight fit on 2mm gear shafts. I made my own cardan shaft, using 1mm NS rod and nested brass tube 'bosses' at either end.
I made a detachable brass cradle, lined with cycle tyre innertube, to hold the motor/gearbox firmly and quietly. The cradle has two alignment spigots and is screwed to a broad centre spacer on the tender frames. A screw fitting at the top allows the motor to be slid out, or its fore-aft position adjusted.
2) Next easiest bit, the modified Compact+ with Drivestretcher D2 and replacement bossed axle gearwheel. Chris supplies the Compact+ with parts to add front and rear bearings for a stand-alone gearbox. I chose to make the rear bearing removable, by soldering 10BA nuts on the inside face of the rear fixing holes; this allows maintenance and re-washering of the worm shaft if needed.
Since the upper motor-fixing screw hole was now redundant, I reduced the height of the main Compact+ frame to allow more space for lead above it. As a 'belt and braces' measure, I soldered etch waste NS strip around the top for strength - not sure how necessary this was.....
The substitute D2 drivestretcher may be installed as per Chris's instructions, and angled to suit your required cardan shaft 'level'. However, I found that in this configuration, the bottom of the D2 frame would have fouled the bottom of the ashpan, requiring a cut-out and a visible D2 beneath the loco. By inverting the D2, I reduced its 'lower profile' and avoided that problem. I had to pay the price of modifying the D2, by removing part of the rear end of its fold-up 'base ' (ie 'top' in my usage), to allow articulation with the frame of the main Compact+ gearbox, as well as notching the underside of the front bearing bracket, to clear the idler gear which fouled it in my particular chosen articulation angle. This should be clear from the photos, I hope.
Actually, although the assembly is relatively simple, the setting of the articulation of the modified assembly is a non-trivial matter, and will depend on your particular prototype, particularly the 'space' available for the driveshaft run, as constrained by the relative heights of axle, ashpan, footplate and any raised cab floor. I spent a fair while 'trying' the mocked up gearbox against drawings, and then in the actual chassis, with the articulation tack-soldered for easy adjustment in-situ, before removal and completion of solder seams. However, I want to emphasise that the High Level gearbox components allow a great degree of freedom, even before you consider modifying them as I have done here!
3) The wormshaft bracket assembly. This part is entirely custom-built, though using spare High Level gearbox bracket components. In many ways it is less critical than the gearbox articulation, though it's dimensions will be set by the latter. The main thing is to allow sufficient wormshaft projection behind the bracket, to allow a firm coupling with the cardan shaft, whilst placing the bracket sufficiently rearwards to minimise the angle of rise/fall of the gearbox on the axle suspension, which also allows the easiest sideplay on curves.
The bracket comprises an 'L' shape, being a cut-down frame spacer, with a cutout to accept the bearing bracket itself, which is made removable via 10BA nuts on the front of the wormshaft bracket. Two NS spigots in the base of this, locating in holes in a dedicated frame spacer, prevent it from rotating when fixed in position.
When I assembled the chassis, I did not know the height at which the wormshaft bracket would sit, so I added the dedicated spacer low in the frames. I subsequently marked and drilled for the bracket screw and spigot holes - you can see a redundant set of three holes from my first trial! I soldered a NS washer under the wormshaft bracket to adjust the height once a discrepancy became evident, and subsequently adjusted it by adding shim washers to finalise the cardan shaft height.
OK, that's enough words from me for now - I hope the further illustrations will help understand what I am about. (Sorry, major hijack of your thread here....perhaps you/John McA might want to separate to a new thread and place a link here instead?)
Finally, mindful that you are aiming 'easy-build' kits for the relative newcomer to this side of the hobby, I should emphasise that there are easier ways to drive from the tender - directly and visibly, above the footplate. But I feel it is worth flagging up to you and potential customers of yours, the scope for 'hidden' drives. I fought shy of tender-motors for ages, partly because of perceived complexity, partly for the visual aspect of the exposed drive shaft.
Good luck with your developments, and if you decide to give this a try and want any further info, PM me any time.
Best wishes
Steve
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Maybe I shouldn't be idle. I always tin brass to 'paint' it metal anyway.
