A small G3 loco

Discussion in 'G3' started by jamiepage, 9 April 2015.

  1. JimG

    JimG Western Thunderer

    Jamie,

    Here are the PDF copies of the pages from the G!MRA Newsletter in 1982. I think they will appear at attachments which you can download. Haven't done this before so we'll see what happens. :)

    The first two files - JG-Gear-01/02 - are the excerpts from my letter to the newsletter describing the differential driven valve gear idea. The next five files - JvRPage01 - 05 - are John van Riemsdijk's response in the following Newsletter with a full description of his gear driven valve gear.

    The last two files - HinesDrainCocks01/02 - I just happened to come across and remembered your recent discussion about working drain cocks. This is a simple idea which you might be able to hide successfully on your cylinders, especially if the "drain cocks" can be fitted almost under your valve faces.

    Jim.
     

    Attached Files:

    Last edited: 17 April 2015
  2. jamiepage

    jamiepage Western Thunderer

    Jim,
    I really am most grateful to you, thank you very much indeed. Have opened them all successfully, and will now print off to read at leisure.
    And actually, you've given me an idea for the draincocks. I didn't want to fit overscale jobs out on the cylinder bore centrelines, (although the design Steve sent this morning has promise). However, it might be possible to drill up from underneath into the steam ways betwixt ports and the cylinders- near the bores but inboard enough to be less obvious, especially if hidden behind cosmetic cocks and links. The nearer they get to the bores the more efficient at clearing the cylinders, presumably.
    Much to think about, and many thanks again.
    And I must say, that gear driven reversing system is rather clever.
    Jamie
     
  3. JimG

    JimG Western Thunderer

    Jamie,

    And some of JvR's comments on setting the valve gear might be appropriate to the earlier discussions on slow running and the use of devices like the Slomo to achieve it. He advocates the retarding of the valve gear to give much better slow running and that can be achieved with the gear driven setup and you can advance the gear to give better high speed running when required. The only thing you can't do with this valve gear is to notch up, as you can with traditional gears.

    Jim.
     
    Last edited: 18 April 2015
  4. jamiepage

    jamiepage Western Thunderer

    Thank you, Jim. This is very interesting
    Jamie
     
  5. jamiepage

    jamiepage Western Thunderer

    A happy hour or two on pantograph and lathe produced some 'bottle' buffer stocks. And now 'Steam Trains in your Garden' has arrived so it's time for a cup of tea and a bit of reading, which beats trying to get the lawnmower to start. IMG_0001.JPG
    IMG_0001.JPG
     
  6. JimG

    JimG Western Thunderer

  7. jamiepage

    jamiepage Western Thunderer

    Thank you, Jim. That's an imaginative solution, although at some point Stephenson's link starts to look attractive again! I won't know exactly how much lateral space will be available until the slimline Slomo arrives, but the eccentrics plus reverser gubbins need to be quite slim. Unless that is the Slomo can be mounted on the trailing axle, but again I need to wait for it to arrive. Your gearbox could well be a good solution either way.
    That is an interesting forum as well; bookmarked now for some investigation later.
    Thanks again,
    Jamie
     
  8. jamiepage

    jamiepage Western Thunderer

    The long steamways on this design of cylinder/ steamchest offer probably the greatest potential for problems. Each has to start on an angle and right on the lip of the bore, and c.40mm later has to find a steam port 1.5mm x 4.75mmx 3.2mm deep. It would be quite easy to have a drill snap, or for the bore to wander off and miss the port completely. Or worse, find the larger exhaust port.
    First, the ports themselves which were straightforward; a slotdrill in the milling machine plunged into the portface at correct centres did the job, good use being made of the mill's indexing wheels.
    IMG_0002.JPG
    There seemed no point in lapping the portface until the steamways were successfully (or not) completed, so each end of each cylinder was set up in turn in a machine vice and adjusted, using a long series drill to align the desired entry point and the target port. The ports were to run 3mm below the portface so were not aligned with the bore centre, which meant that care had to be taken to ensure the start point didn't wander from its required position- just, but only just, breaking the bore's lip.
    After much prevarication, each port was started with a 1.5mm slot drill, to about 5-6mm., followed up with a brand new 1/16 drill, then completed with a long series drill (brand new again). Great relief and a cup of tea each time as the drill broke through into the desired port.
    As an aside, the standard length drills had been bought as a set of 10, but were awful. All but 3 were visibly bent; fortunately the good ones ran true, so were used to deepen the ways a little more before trusting to the long series drills. IMG_0001.JPG
    Exhaust ports are larger diameter but significantly shorter so with luck the worst is now done.
     
  9. JimG

    JimG Western Thunderer

    Jamie,

    A bit late now but another way I have seen suggested for difficult steam ways in cylinders such as yours is to drill down from the cylinder ends to break through the bottom of the cylinder block, and drill down through the steam ports to break through the bottom as well. Then connect the appropriate holes with milled channels in the bottom and make a plate to cover them and seal them off from the outside and each other. You would probably want a gasket or some sealing compound to make sure that everything was steam tight. You could treat the exhaust similarly although the more normal circular hole exit might be preferred if you want to put a union on it. It would also probably be better to angle the holes from the cylinder ends towards the centre so that the holes break through the bottom as far away from the edge as is possible to help with sealing.

    You are really cracking on with this - excellent stuff. At this rate you might even beat all the PMV's. :):):)

    Jim.
     
  10. jamiepage

    jamiepage Western Thunderer

    Ha, PMV's ? Thanks Jim., your point about a milled channel along the under side is well taken. I am trying to work out what to do about the cylinder drain cocks an am starting to think along those lines - a milled channel along the underside to some sort of drain cock mechanism inboard, camouflaged by a scale set of dummy cocks, linkage etc. Anyway, all good fun,
    Jamie
     
  11. jamiepage

    jamiepage Western Thunderer

    Have managed some work on the coupling rods.
    Blanks pantographed from steel-
    IMG_0001.JPG

    Held in a makeshift jig for accurate drilling thanks to DRO- IMG_0001.JPG


    Bearings added-
    IMG_0001.JPG

    Cleaned up after soldering. -
    IMG_0001.JPG

    They still require tapered cotters and caps to the oil cups, both of which will add character so long as I don't mess them up.
     
  12. Jon Nazareth

    Jon Nazareth Western Thunderer

    Jamie

    They are coming along very nicely. I like the way you have placed a dummy bearing block over the actual bearing, at least I think that's what you have done, really looks the part.

    Jon
     
  13. jamiepage

    jamiepage Western Thunderer

    Thank you, Jon. Yes, that's it. The turned bearing is pushed through from behind, (with the collar to act as a rubbing surface against the wheel), and is overlength so it projects outwards beyond the rod's front face. A cosmetic rectangular bearing is cut from thin brass sheet and slipped over , held in position and the whole lot soldered up. All filed back flush and cleaned up. Truly a bit of a fudge to be honest; JimG would have proper split bearings. And in S.
     
    Rob Pulham and Steve Cook like this.
  14. JimG

    JimG Western Thunderer

    Jamie,

    Not quite. :) But what I did do on a G1 chassis of an early Caledonian locomotive with similar bearings was to actually make rectangular bearings with rectangular holes in the connecting rods with a small amount of horizontal movement, then solder the brasses in place when mounted on dummy axles on the locomotive. It was a way of getting the coupling rod centres exactly correct for the chassis and didn't require too much accuracy in the making. :) I think I must have milled all the holes and bearings on a vertical slide on the ML10 since those were the days when milling machines were way too expensive to own. :)

    Jim.
     
  15. jamiepage

    jamiepage Western Thunderer

    I knew it.:thumbs:. :)
    Do you still have the loco, Jim? I like the early locos very much and think they make very attractive models.
    Jamie
     
  16. JimG

    JimG Western Thunderer

    Jamie,

    As much as I built of it.:( I was building it along with a garden layout in the late 1980s then had to move house therefore the layout idea was stopped, and so was the loco building. It took another year or so before I could set up my workshop in the house we moved to (still there/here) and by that time the G1 development had stopped. This was the loco that the spur differential gearbox was to be fitted to.

    G1loco-01.jpg
    G1loco-02.jpg

    I had started to fit slip eccentric instead of the gear-driven valve gear.

    G1loco-03.jpg

    And in good politician fashion, I had mis-remembered what I had done with the connecting rod bearings. :) I had made the bearing holes slightly sausage shaped to allow normal circular bearings to be moved fore and aft to be positioned, then soldered and I had milled out a rectangular recess for a rectangular brass plate to mimic the prototype bearing and hide the subterfuge. :)

    The loco was being built to 3/8" scale and the wheel flanges were a lot finer than the G1 standards at the time. I never found out if they would have worked. :) Like your loco, the cylinders were cut from solid and shaped in the lathe, with a big milling cutter in the chuck and the cylinder mounted on a stub through its bore in a machine vice on the vertical slide, and a long handle clamped to it to rotate it around the stub while feeding in to the cutter - decidedly dodgy but a recommended method of the time for those of us with no milling machine and rotary table. :)

    Jim.
     
  17. jamiepage

    jamiepage Western Thunderer

    That's excellent, Jim. Thanks for the photos. It deserves to get finished. Presumably that's an exhaust 'manifold' bridging the cylinders- how was steam to get into the steamchests?
    Jamie
     
  18. JimG

    JimG Western Thunderer

    Jamie,

    Yes, that was/is the exhaust manifold on top of the valve chests. I think I was forced into making it like that since the centre line of the boiler was quite low and I had to get the blast pipe quite low. At this remove, nearly thirty years later, I dare say I could have put the connections to the exhaust outlets at the bottom of the cylinders and brought the blast pipe up between the valve chests.

    There is no indication of how I was going to connect the steam inlet on the valve chests and I can't remember what I was going to do. :) I suspect I might have been thinking of fitting a tee piece between the valve chest covers but looking at the situation now, I think that would have presented big problems. It could well be that I would put connections to the valve chests on the top just behind the exhaust manifold and connect them with a 'flat "U"' shaped pipe with a "T" connection in the middle.

    Jim.
     
    jamiepage likes this.
  19. jamiepage

    jamiepage Western Thunderer

    Splendid model, Jim. Thank you.
     
  20. Simon

    Simon Flying Squad

    A lovely bit of work, I'm sure it would run through the track work at "Launceston Road".......

    Simon