Inside valvegear in 7mm. Techniques and components

iploffy

OC Blue Brigade
Simon Dunkley said:
Not 7mm (smaller!) and not GWR, but the photo below shows some of the constructional details of the working inside valvegear fitted to an S scale GER T26 (LNER E4) 2-4-0 built by Trevor Nunn.

The motion unit is removable, and soldered to thin single-sided PCB. It is held in place either side with a screw into in a captive nut, which is electrically insulated from the rest of the motion as the loco has split axles and split frames. The screw heads are hidden behind sandboxes when the body is in place.

 

Steph Dale

Western Thunderer
Simon,

The use of copper clad Paxolin in that application certainly bears some closer inspection. I'm fortunate that although I'm using split axles on the front and rear of the chassis for the loco I'm building the crank axle is solid. The frames end up being neutral too, as the insulation is at the hornblock/frame interface.

The concept of an insulated crank axle doesn't automatically fill me with fear; I've got a couple of thoughts on how I might set about doing it for an 0-6-0t I should be building shortly (LSWR G6). Incidentally, I notice some similarities in the motion arrangement with the G6 - I assume it's the Adams GER-LSWR connection.

I've just noticed that the loco is left-hand lead; which is a little peculiar. I wonder whether the model is correct in that regard or why Adams locos for the LSWR were right hand lead (as on most railways in fact).

Pete,

As you can see in the build I'm doing here, I've got the Finney 7mm parts available. The problem was that they were lacking a certain degree of 'heft' that's obvious in the prototype. It makes the valvegear relatively(!!) simple to assemble and the instructions seem good. In 4mm it's always fiddly though...

You may have benefited from building your crank axle with Loctite 638, as I did with this loco. Admittedly I'm likely to go back to silver soldering for a couple of double-framed locos I'll be building although there's no real reason why; I know that the Loctite 638 would be stronger in theory. In 4mm you could also have done it with something like Powerflow flux and a good quality lead-free solder. Anyway, my hat is raised in your direction this evening; I wouldn't be brave enough to silver solder a crank axle with the eccentrics mounted!

Ian,

You might be surprised: it's taken me longer each evening to keep this thread updated and take the photos than I've spent at the workbench. I think it's probably added about a dozen hours all told...

And so to tonight's update and another milestone passed. Connecting rods have been fiddled and fitted. I started out by finishing off the crossheads with their piston rods and then trimming off the web at the back. They were then bedded into the slidebars/piston rod gland with Brasso and then rinsed off in meths as before. The lengths of the piston rods were set by dropping the crossheads into the back of the slidebars and cropping the piston rod off on the front side of the cylinder back:
 

Attachments

  • IMG_8094.JPG
    IMG_8094.JPG
    71.2 KB · Views: 74
  • IMG_8093.JPG
    IMG_8093.JPG
    106 KB · Views: 73
  • IMG_8092.JPG
    IMG_8092.JPG
    93.7 KB · Views: 73
  • IMG_8096.JPG
    IMG_8096.JPG
    102.4 KB · Views: 71
  • IMG_8098.JPG
    IMG_8098.JPG
    111.6 KB · Views: 71
  • IMG_8102.JPG
    IMG_8102.JPG
    62.3 KB · Views: 152
  • IMG_8097.JPG
    IMG_8097.JPG
    110 KB · Views: 76

OzzyO

Western Thunderer
Hello Steph,
how long does the Loctite take to go off, and then how long before it's at full strength?

OzzyO.  :thumbs:
 

Steph Dale

Western Thunderer
Paul,

If you do a search for 'Loctite 638' you'll come up with a datasheet pretty quickly; but it's a pain to link to otherwise I'd have done it here.

I've just had a quick squint at my copy and the curing time is highly dependant upon fit, materials and temperature during the curing time.  72 hours is the absolute maximum, which suits me; I make the crank axles up during the early parts assembly and then leave them on my heater cabinet until I'm ready to use them...

I hope that gives some help; you'll be better of looking at the manufacturer's info though.

Steph
 

Steph Dale

Western Thunderer
OzzyO said:
Thanks Steph,  :thumbs: Just going to venture into the auction site.

OzzyO.

Cool - let me know how you get on!

In terms of progress on this set of 'gear, it's not slowed down.  In fact it sped up in the lead up to Bristol 0-gauge show as I had a couple of interested parties in close attendance.  It did mean that in the push to get it finished (yes, really) I missed out photographing a couple of stages.  I'll come back to these later and then edit this post to include the update as I take it apart ready for painting... :headbang:

However, it went together splendidly quickly.  The only remaining parts in need of adjustment were the lift links.  The only part in the Laurie Griffin set which was a bit 'out' for dimensions; the top joint needs some subtle re-shaping:
 

Attachments

  • IMG_8103.jpg
    IMG_8103.jpg
    36.1 KB · Views: 77
  • IMG_8104.jpg
    IMG_8104.jpg
    78.4 KB · Views: 82
  • IMG_8105001.jpg
    IMG_8105001.jpg
    83.1 KB · Views: 184
  • IMG_8106001.jpg
    IMG_8106001.jpg
    78 KB · Views: 181

Steph Dale

Western Thunderer
Dan Randall said:
Aroooga!  :drool: :drool: :drool:

Regards

Dan

Dan,

Can I quote you on that?  Oh, I have....  ::)

Yeah, I'm pretty pleased  ;D  The silly thing is that it really hasn't taken all that long to do; decent parts and drawings have helped a lot along the way though.  The next loco I'm building with inside motion won't be quite so simple (LSWR G6).

I've even had it running this evening and in the last half hour I've done the disassembly into the main components:
2 con rod and crosshead sets.
Motion bracket and cylinder back.
Crankaxle.
Eccentric straps, rods, reversing gear and valve rods.

Steph
 
S

Simon Dunkley

Guest
Trevor Nunn's inside valve gear.
iploffy said:
Very intricate I wonder how long it takes someone to do a work of art like that
Ian
I finally got around to asking the great man (surely the most compleat railway modeller around today?)
Basically, between 40 and 50 hours, or put another way, the equivalent of a full week's work plus a bit of overtime...
 

phileakins

Western Thunderer
Oh dear!

Having been encouraged by this thread I've had a rush of blood to the head and gone and bought a Griffin Stephenson valve gear set (previously owned by Geoff Stenner of all people) from that well known auction site.  It needs replacement crossheads and slide bars to fit the SECR P class it's destined for though.

But, it having arrived and I have seen what I have undertaken, I have a serious case of the willies, so I might well be asking for lots and lots of advise before it's done.  :)

Phil
 

Steph Dale

Western Thunderer
phileakins said:
Oh dear!

Having been encouraged by this thread I've had a rush of blood to the head and gone and bought a Griffin Stephenson valve gear set (previously owned by Geoff Stenner of all people) from that well known auction site.  It needs replacement crossheads and slide bars to fit the SECR P class it's destined for though.

But, it having arrived and I have seen what I have undertaken, I have a serious case of the willies, so I might well be asking for lots and lots of advise before it's done.  :)

Phil

I don't quite know how to put this.  How about:  :shit:

I've got a couple of Meteor 'P's to do and they've stalled because the parts required to make them fit aren't yet available from Laurie.  They will be, but I haven't even drawn them up yet, let alone cut anything out...

The two problems are mainly in the expansion link, which is very much smaller than the one Laurie does and the crossheads, again; Laurie doesn't do any small enough.  You'll also quite probably need to turn a section out of the front axle to give the crossheads enough space to travel.  You'll also need a very short-throw oval crank, which I don't think Laurie does.

It's not a great place to start.  The GAs are fairly readily available (which series are you doing?) they're screens 8174 for the short cab, 5602 for the tall cab and 5601 for the pipe and rod (which is good and clear for the motion).  The screen numbers refer to the NRM's microfilm list; copies are easy to get hold of (email Search Engine for an order form).

Sorry to be the bearer of bad tidings; it's nice to know that the person who out-bid me will give a good home to the parts in a Southern loco.  A SECR 'C' 'D' would have been much easier though.  ;)

Steph
 

phileakins

Western Thunderer
Steph Dale said:
I don't quite know how to put this.  How about:  :shit:

I've got a couple of Meteor 'P's to do and they've stalled because the parts required to make them fit aren't yet available from Laurie.  They will be, but I haven't even drawn them up yet, let alone cut anything out...

The two problems are mainly in the expansion link, which is very much smaller than the one Laurie does and the crossheads, again; Laurie doesn't do any small enough.  You'll also quite probably need to turn a section out of the front axle to give the crossheads enough space to travel.  You'll also need a very short-throw oval crank, which I don't think Laurie does.

It's not a great place to start.  The GAs are fairly readily available (which series are you doing?) they're screens 8174 for the short cab, 5602 for the tall cab and 5601 for the pipe and rod (which is good and clear for the motion).  The screen numbers refer to the NRM's microfilm list; copies are easy to get hold of (email Search Engine for an order form).

Sorry to be the bearer of bad tidings; it's nice to know that the person who out-bid me will give a good home to the parts in a Southern loco.  A SECR 'C' 'D' would have been much easier though.  ;)

Steph

Oh dear (again!).

Strangely I have a D kit in the kit pile (at the bottom) but a very poor GA copied from a magazine (I think it was 'The Engineer') of the time. I'll have to order a set from the NRM when the time comes.  Too expensive to make a horlicks of and I need to gain a lot more experience before I start it.

I've got the Meteor P kit and haven't been able to get on with it, an instruction to break parts apart 'cos they were wrongly drawn and etched does not fill one with confidence.  I've built and taken it apart twice now, third time lucky - but obviously without working valve gear to start with.  :-[

I've got the GA's for the original (tall) pair of P's with lever reverse, which makes it more interesting, and means a bit of scratch building in the third try. I've got to make new frames as well as the ones I have are now well mangled.

I'll look out for the pipework diagram as I passed that one up when I bought the GA's some time ago. Thanks for the heads up. 

Sorry Steph, I was in two minds whether to up the bid at the last minute, but it was a bargain at the price even if I can't use it at the moment. At least I now know what you are writing about.  :D

Phil
 

OzzyO

Western Thunderer
Hello Steph,
would it be possible for you to let me have a look at the G/A, frame plan of the 2251.
TIA
OzzyO.
 

Steph Dale

Western Thunderer
OzzyO said:
Hello Steph,
would it be possible for you to let me have a look at the G/A, frame plan of the 2251.
TIA
OzzyO.

Yeah, sure.  I can take the mag with me to Kettering (I should have the loco/chassis with me anyway).  Of course it's probably just as easy to drop Simon a line and get him to sort out a copy for you; Great Western Railway Journal #24.  I've also found the one on the 94xx class useful, that's #62.

Steph
 

OzzyO

Western Thunderer
Thanks for that Steph, I wont be doing Kettering, 8hrs. on a train 2hrs at the show, 8hrs on a train.
But I would check your crank axle in relation to your wheels.
Thanks to all for the PMs.  :thumbs:

OzzyO.
 

OzzyO

Western Thunderer
Steph Dale said:
???  Um; how/what?  :scratch:  ::)

Steph
check the position of your inside cranks in relation to your out side cranks, it shows it quite clearly on the G/A drawing.

OzzyO.
 

Steph Dale

Western Thunderer
OzzyO said:
check the position of your inside cranks in relation to your out side cranks, it shows it quite clearly on the G/A drawing.

OzzyO.

Aah, I did wonder if that's what you were driving at.  Nope; this has been confirmed by photos.  Some, not all, of the 2251s did have balancing as I have done it; so-called 'Stroudley' pattern.  Take a good look at the balance weights of the locos and you'll see they occur in two positions; a relatively small one near the crankpin indicates conventional balancing, a large one opposite the crankpin indicates 'Stroudley'.  You'll also no doubt have noted the two patterns of wheels in use across the class (crank between or crank in line with spokes)...?

'Shown quite clearly on the GA' is a bit of an oxymoron really - they represent intent, not fact.  And many have got caught by that one!
Steph
 
Top