7mm On Heather's Workbench - a baby Small Prairie

Discussion in 'WR Action' started by Heather Kay, 2 August 2017.

  1. Heather Kay

    Heather Kay Western Thunderer

    I have cast connecting rods from two different sources here. Both are shaped so clearing the knuckle rivet ought not be a problem. I hope.

    This morning's fun and games will be working out what I’ve got for cylinders and slidebars, and out of that what will be kept for use.

    Let’s assess the various items I have, leaving aside the originally-designed etched construction.

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    This is the set of cast parts from the JLTRT 44/45xx super detailing kit. Cast crossheads are conspicuous by their absence, but on past history that’s no bad thing. Apart from the vacuum pump and bracket, and the slide bars, it strikes me most of this is far too chunky to be used on a dainty as-built 3107.

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    This is a set of bits from PR Components. Very tidy. Yes, I’ll have to add all the oil pots and bits to the slidebars, but the latter do actually fit in the cast crossheads before I’ve even fettled them. The motion brackets are much finer, too. There are also parts for the valve linkage, though precious little of this is really visible in the photos I’ve looked at.

    I think, based on what I’ve got here, the PRC parts will be used, plus the JLTRT vac pump and bracket. The various plates and glands round the cylinders themselves will be made from the kit etch. The real thing, even late in service, was apparently very tidy with plates and covers, albeit covered in grease and grime at the end.

    Time for some further studying of the photos, drawings and parts, accompanied by a coffee.
     
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  2. Heather Kay

    Heather Kay Western Thunderer

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    I think that’s how it’s supposed to go. I was worried at first as to how the motion bracket would be held. Then I found the etched bracketry which was not mentioned in the kit instructions - well, the drawn parts anyway. Note the valve chest cover casting acting as a temporary counterweight!

    One problem I need to overcome is how to make the castings look like they belong. All the holes in the cylinder skeleton seem to be oversize, and the etched parts meant to fit over them undersize. The destructions expect me to use tube to help the piston rod run nicely, and to help guide the valve rods as well, and I was expecting to do much the same myself. Once Mrs Mojo has made a reappearance - she bimbled off somewhere earlier, goodness knows where - I will make an effort to begin assembling the various parts.

    Oh, yes, by the way, I think quite a bit of gentle filing will be needed to thin the leading connecting rod boss to help give some clearance for the wiggly bits. Unless I decided to use the etched rods after all. They, however, are hinged on the centre crankpin, which may be suboptimal for a spring chassis.

    Lots to think about, then.
     
  3. Heather Kay

    Heather Kay Western Thunderer

    Right, a new week and time to get something constructive done - notwithstanding an absent mojo and Real Life getting in the way.

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    Cylinders. I am making them with a combination of the etched parts and the PRC detail castings. I had to check, which is always something worth doing and thoroughly recommended by the way, if I had to fit cylinder relief valves. These things are very prominent on the front and back of the cylinders, and have been allowed for on the etched parts. Happily, the original build of what became the 4400 class didn’t have these valves. That’s handy, since I haven’t got any in stock, and couldn’t find anyone who actually stocks them as a detail part.

    In the photo, I’ve used etched parts to plug the large valve chest holes. I found that filing the cusp off the circular plates allowed them to fit tightly in the etched holes with a cusp. Flooded with solder, I hope they’ll stay put as I drill them out later to take the cast parts. I’ve also fitted the back of the cylinders. This is before I tidied up to pretend I used invisible solder, of course.

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    For the cylinder fronts, I soldered the valve chest plates on the outside. I’m not sure why I did that, but it seemed a good idea at the time. It probably doesn’t matter, as this side will be lost - hopefully - up under the running plate step.

    Next, I futzed about with some brass tube, and cleaned up the PRC gland castings. I am liking the PRC quality, by the way. Now JLTRT and Hobbyhorse are gone, I think PRC will see some more of my custom. With the gland casting fitted (sorry, no pics) I installed tube to guide the piston rod. While I was at it, I measured, trimmed, and fitted the nickel silver piston rods to the crosshead castings. These assemblies would be used to help fit the slide bars later.

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    After a few hours, this is where I am. The crossheads are a nice smooth run in the slidebars, the latter did need some fettling. Very careful fettling, as the NS used to cast them is very soft. Happy with the basic assembly, I have plonked it on the chassis for size.

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    Allowing for the fact nothing is properly aligned or physically attached right now, and this is to the slightly wider S7 standard, that looks like a fairly respectable amount of space down there. That’ll come back and bite me later, of course!

    The question remains whether I ought to use the etched connecting rods to give the proper scooped profile. If I do, can I ask if anyone has experience of converting etched rods so the knuckle joint works?

    I shall wander off now to nurse my fingers, which are a little sore from all the careful filing!
     
  4. Peter Cross

    Peter Cross Western Thunderer

    If your leading crankpin is at back dead centre. It looks like the pin will always be behind the crosshead.
     
  5. Heather Kay

    Heather Kay Western Thunderer

    Ooh, now that would be helpful. I suspect I shall find out properly tomorrow.
     
  6. freelance7

    freelance7 Active Member

    Heather Kay likes this.
  7. Steph Dale

    Steph Dale Western Thunderer

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  8. Heather Kay

    Heather Kay Western Thunderer

    Ignoring coupling rods for now, because they’re bothering me and I’m not sure which way to go with them, I got on with the cylinder block.

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    I added the front overlays, and the cast valve/steam chest covers. The motion brackets were fitted late yesterday. I ought to explain the slidebars slot into the cylinder block etch, and have a slight overhang at the front. Once I was happy with the location and orientation of the bars, I soldered them in place. The front ends were then trimmed and filed back flush, so the front overlays could go on. Later I will fill the relief valve holes, and add something to resemble the central nubbin. It’s not clear in photos what it looks like, but I’m leaning towards a small nut soldered on.

    The etched support bracket to the rear is still not fitted. I am puzzling over the location and fit of the vac pump. The etch bracket more or less is the right place, but puts the pump casting a good bit outboard of where it needs to be to connect to the crosshead. I think I may need to make my own bracket, and even source a better pump casting. The ones I have just don’t quite look right to me.

    With the main cylinder details done, it’s time to consider the wrappers. The kit wrappers are etched in NS. They’re like battleship plate. Even annealing them, I doubt I could comfortably form them to the right shape. They have massive cusps, and when comparing with the real thing, all the bolt heads are in the wrong place. It also transpires they’re too wide, and filing them back to the right size would lose the incorrect bolt heads! I suppose I could easily make new ones.

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    This is how the wrappers should look. This is a later loco, one of the "proper" small prairies. There’s some useful-ish info on the draincocks there, too, but that’s not important now. The position of the wrapper bolts is what we're after.

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    On the left, is the cleaned up etch wrapper. On the right, my paper template cooked up using the cylinder block and Mark One Human Eyeball. The blobs at the bottom of the template are where the draincocks will go. That position I assumed to be on the centreline of the slidebars at the bottom of the cylinder wrapper, and everything else came from there.

    I’ll transfer the template to some NS sheet and make new wrappers - once the mojo comes back. She’s going to need a good talking to when she does. :mad:
     
  9. Heather Kay

    Heather Kay Western Thunderer

    Mrs Mojo reappeared. We had a free and frank exchange of views.

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    The secret, which every other builder already knows, to making cylinder wrappers is to make them fit the right shape as near as it’s possible to get it without any fixative used. On that basis, and my sore thumbs, I think I’m happy with that. I think it may be time to deploy the RSU and fix the darned things in place.
     
  10. Heather Kay

    Heather Kay Western Thunderer

    I’m still trying to ignore the coupling rods!

    Vacuum pumps, or as the drawings have it, air pumps.

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    I have three specimens. One cast in white metal, which I think shipped in the box from Malcom M. The other two, I think, emanate from what was JLTRT. They are all fine and dandy, albeit in need of some careful filework, and what I deem an almost impossible task of drilling down the centre to take the pump rod from the crosshead.

    One other thing: all three are a mirror image of what I need for this build. Actually, let’s rephrase that: the mounting bracket is on the wrong side for this build. These castings are ideal for mounting inside the fireman's side frames on an inside cylinder loco.

    Now, before I embark on creating my own from tube and rod (the better to avoid having to break drills for a start), does anyone know of the "correct" outside cylinder driver's side pump being available anywhere? Before you ask, I have checked Warren Shephard, PRC and Laurie Griffin's catalogues with no joy. Mr Ragstone's site appears to be offline, and I sorely miss Hobbyhorse in these circumstances.

    While I’m about it, I need to think about draincocks. I think the early ones are simpler than the usual J-shaped castings most kits have. I fear something of a compromise might be on the cards.
     
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  11. simond

    simond Western Thunderer

    "Vacuum pumps, or as the drawings have it, air pumps."

    well, they may create a vacuum, but they pump air... I suspect pumping a vacuum might be a tad challenging!

    If you solder the pump to a suitable chunk of brass, presumably you could hold the brass in a vice, and drill using a pillar drill. But I agree, bit of an unnecessary challenge. If you go for the tube option, can you cut the lumps off one of the castings and silver solder them to your tube, or would it be easier to scratch the whole shebang?

    best
    Simon
     
  12. Heather Kay

    Heather Kay Western Thunderer

    Thanks Simon. You are correct about the air/vacuum thing. I seem to have got them muddled somewhere, probably because the idea was to create a vacuum by pumping out the air. Every day is a school day!

    If I’m going to drill out a casting, I may choose the WM one. Even then, binding and snapping seems likely. The real thing, apparently, had a 24 inch throw, so that’s a hole of 14mm I need to drill, straight and true, right down the barrel. I think I’m better off using tube and, as you say, trying to repurpose bits off the cast ones.

    I suppose I’d better get cracking!
     
  13. Heather Kay

    Heather Kay Western Thunderer

    It’s not perfect, but it will suffice, I think.

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    Raw materials. I’ve soldered the cast pump to some scrap brass to make it easier to hold while I dissect it. Some NS bar to replicate the square top, 0.8mm NS rod for the piston rod, and some brass tube of suitable section for the body. My aim was to cut away the two valves from the top of the casting, and the square flange affair at the end.

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    I only broke one piercing saw blade, which I felt was good going for me!

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    Some time later… before I assembled this, I filed a flat on the tube to locate the strip and upper parts more easily. I left the tube long so it was easier handle. Trimming the thing to length was the final stage, after another flat filed on the side of the barrel where the mounting bracket will need to go. Getting there. Not perfect, but I’m happy.

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    With everything mocked up, I could work out how long the piston rod should be and check it didn’t pop out of the end at the extreme of travel. As you can see, while the motion bracket support etch has a suitable pump bracket, it’s still not in the right place, plus it’s too far outboard. One tweak I could do is gently bend the crosshead bracket over a bit to give some extra clearance behind the pump for wiggly bits. That might also help the pump mounting situation. It’s supposed to have the centreline somewhere close to the rear edge of the slidebars, as far as I can make out.

    My eyes are complaining now, so I’m going to stop and let this fester for a bit. I think it’s time to consider how to actually fit this caboodle to the frames properly. That will also involve thinking about those coupling rods, I suppose. ;)
     
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  14. Heather

    Having studied the photo of 3102 on page 1 of this thread it doesn't look if there is flat on the body of the pump. The fold down flap on the bracket looks almost in the correct position. Could this be placed behind the pump and soldered up without using the supplied bracket? if it lines up of course with the crosshead is it possible to use the riveted part on the top of the casting to represent it's attachment. I realise this means remaking the pump which seems such a pity as you have managed to improve it's appearance no end over the cast item. All the work you done so far on the slide bar/crosshead/cylinders is looking fantastic and will greatly enhance the 'look' of 3107 and I look forward to further postings.

    Regards
    Malcolm
     
  15. P A D

    P A D Western Thunderer

    Hi Heather,
    This is a shot of my Warren Shepherd 45XX. Without checking I'm not sure, but I think I sawed a groove in the bottom of the vacuum pump make a slot for the piston rod to run in. Not easy, but saves on drill bits.

    If you don't have slide bar lubricators, Peter Roles has nice castings on his range.
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    Cheers,
    Peter
     
  16. Heather Kay

    Heather Kay Western Thunderer

    Hi Malcolm! I've been assessing fit by eye up until now. I think it'll pay me to make the cylinder block and support bracket fixings to the chassis next, then I can really see exactly how things will fit without things shifting about all the time. The flat on the pump barrel was to give me an area to solder a bracket to. I'm beginning to think I may need to revisit what I made yesterday, but I'll fix the main stuff in place first before I make that decision.

    I do have those bits. I've been leaving them off until I'm happy with the way everything fits. There's nothing worse than attaching tiny castings only to lose them at some point later! I like the idea of cutting a slot, though. I'll file that one for future use. :thumbs:
     
  17. Heather Kay

    Heather Kay Western Thunderer

    Right. What’s been happening?

    Well, a lot of huffing and puffing to be frank.

    I set about working out how to attach the cylinder block to the frames. The idea was to use one long bolt up through the frames, through the cylinder block and into the smokebox saddle. That worked, so I fitted the frames to the bodywork to check for alignments and so on. Various captive nuts and washers were deployed in various places to overcome holes that were etched a bit on the large size.

    I found the motion bracket castings didn’t align with bracket extension in front of the tanks.

    That could be sorted out. Some minor adjustment to the slide bars to let the brackets move further back and all would be well.

    Things went well, until I managed to dislodge a frame spacer. :headbang: It’s been downhill since.

    I currently have more off the model than on, as I retrace my steps to fix things I thought had already been fixed. Looking on the bright side, it’s also allowing me to make good some earlier less than adequate work.

    No pictures, I’m afraid. It’s not pretty.
     
  18. Heather Kay

    Heather Kay Western Thunderer

    Feeling happier.

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    More steps back before making forward progress. The boiler front and smokebox had to come off. Previously, the saddle contained a captive nut. The issues I’d been having were caused because the frame spacer through which the frame fixing bolt went had dropped out and I couldn’t get it back in line with the saddle nut. Having gone back to first principles, I’ve now fitted a bolt that goes down from the saddle. Now, the chassis and cylinder block drop over the bolt, and can be held with a nut. Obvious when you think about it.

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    The next problem to solve was how to attach the cylinder block so that it would still be possible to disassemble the frames easily. The most obvious thing would be to just solder the block to the frames, but that could lead to issues taking wheelsets out. Now, I don’t suppose frames disassembly will ever be needed, but I don’t want to cause headaches for someone down the line. Then again, I seem very adept at causing headaches for myself instead!

    I managed to align the cylinder block where it was supposed to be, with some scrap NS sheet packing to stop fore and aft movement. I then tack soldered the block in place while I drilled a small hole through a vertical frame spacer and into the block itself. This was tapped 10BA, and took a short bolt. Now the block is held sufficiently firmly in both main axes, and I can once more begin to sort out the motion brackets.

    *sigh*

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    Some mild surgery to the slide bars to remove the leading part of the cast-in packing plates was required. Here I’ve posed a cast bracket where it will end up, and it is now in line with the extension above the running plate. Happily, the large etched platework that will support the top of the cast brackets still fits, and even better it seems the dropped flap will match with the air pump location properly.

    You will see that the cylinders are a smidge further back than they ought to be. The real thing shows top of the cylinder front just tucked in under the hanging bar by the square drop. That’s not going to happpen here, sadly, which is down to a couple of factors that make it hard to shift things up. One is the cylinders are a fraction wide, so they won’t tuck behind the vertical part of the hanging bar, even if I made suitable adjustments to the location. Just one more little compromise along the way.

    So, winning? Perhaps. I shall tidy things up and get the motion brackets fitted again. Then I think some time in a darkened room with soothing music and a cold compress will be in order!
     
  19. Heather Kay

    Heather Kay Western Thunderer

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    I think that’s where I want to be. Happy with that. There are still some details to do around the cylinders and slidebars, but I think they can wait for a bit. Next, I suppose, is those pesky coupling and connecting rods. That ought to keep me gainfully employed for a day or two.
     
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  20. Peter Cross

    Peter Cross Western Thunderer

    I'm hoping it's the camera angle Heather. But are the top and bottom halves of the motion bracket lining up?
    All looks impressive.