7mm On Heather's Workbench - the answer to life, the universe and…

[3 LINK]

Evening Heather,

I hope the photos below are of some help, I took them when the loco was at the Watercress line a few years ago. It's a bit photo intensive but at least it is of the 52xx class, the Great Western Railway Journal also did an article on the 42/52xx classes over two issues, I will find out the numbers if you are interested. As we all know you can never do to much research . I think Pete still owns 5224.














There's some more if you want them .

Martyn.

 

[Dave Bowden]

Hi Heather
Here's a couple of photos that may be of some use, location Didcot.



Dave

 

[3 LINK]

Here's some more,























Look at the fine tolerances here....









Nearly done....

 

[3 LINK]

Oh Dear a 72xx has joined the photo shoot , just a couple more to go .









There are some more but I think these are the more interesting one's.

Martyn.

 

[Dave Bowden]

The GWRJ's are numbers 68,69,70. There is a GA in 68 but is only a side view.

In No's 69 and 70 it covers the 42's in Traffic by John Copsey, there are lots of pages of information and loads of pictures.

Dave

 

[Heather Kay]

Oh my! My cup runneth over!

Thanks chaps! I shall "archive" those images for offline reference, if that's okay.

 

[oldravendale]

I should admit to an error in my earlier post. While the K&ESR are rebuilding an actual 4200, the images I borrowed came from the ongoing refurbishment of a 7200 class at Quainton Road.

Amazing - is that still not complete? It must have been on the go for about 40 years now.

I'm pleased to see that they may be making some progress now, though.

Brian

 

[SimonT]

Can I add my thanks for the photos, there is 72XX lying on the workbench alongside a nearly finished 8750. I might follow Heather and "archive" as well.
Heather, I have the appropriate GWJs if you want info from them.
Simon

 

[Heather Kay]

Heather, I have the appropriate GWJs if you want info from them.
Simon

Simon, if you are at Mark this weekend, I'd appreciate a sight of them if you don't mind lugging them along. The Hampshire Reference Library has copies, but someone seems to have put them back on an incorrect shelf at present.

 

[SimonT]

Heather,
unfortunately I won't be at Mark as I am helping Peter Kirmond with Laramie at the Winchester get together on various US outline modellers. We can sort something out by PM?
Simon

 

[Heather Kay]

I'm hoping the lending library may have sorted the storage problem soon, but I'll drop you a PM when my breakfast kickstarts my brain!

 

[Dog Star]

Heather and Simon,

I can see the GWRJs concerning the GWR 7200s are on the library shelf. I believe that the volumes are reserved for an inter-library loan (whether to Mark, Kent or somewhere in Dorset has yet to be decided).

regards, Graham

 

[Ian@StEnochs]

Useful detail photos Martyn.
Note the bottle in the cab, no doubt to slake the firemans thirst, but in service it would be glass! Up here it would have been a 'ginger bottle, Irn Bru likely. I made one for my Caley tank from a piece of clear Perspex turned and polished in the lathe but you can only see it if you know to look for it!

Ian.

 

[pete waterman]

Yes I do. As I note there are two types of cabs. If you needs pics I think I have some.

 

[Heather Kay]

Thanks Pete!

As I mentioned earlier in the thread, this build is already part way through. Because of this I am sort of restricted as far as choices are concerned, being somewhat stuck with what the client did. The finished model will look like a 4200, but whether it will be a dead accurate replica of 4250 is moot.

This morning I resolved the motion bracket issue. What you don't see here is the extensive off-list chats that go on between Graham and I. I punt questions here or via email, and sometimes within seconds of hitting "send" the phone will ring! Graham is, I am certain, gently guiding me away from my LNWR/LMS/BR(M) predilections to things Swindon.

It turns out the bracket castings were often shimmed as the slide bars wore. As the cast brackets are slightly - half a millimetre each side - too wide, the answer was to solder in some thin shim material, and fettle to ensure the crosshead still moved smoothly.



I found the easiest way to align the bracket with the structure above the running plate was to mount the frames to the superstructure with the cylinders in situ. A quick dab with the RSU held things together, and I made the joints firmer by taking everything off the loco again. A bit of tidying, and I was pleased with the result.



At this stage it rather looked like the etched bracket support plate across the frames might be superfluous. However, I had decided the cylinder block should be removable - it has to be so I can fit the front drivers again! - so a modicum of trimming things let the plate fit.

So, aside from the valve chest covers, I reckon the cylinders and slide bars are complete. I think the next move should be to motorise the chassis.



Pushing-along-the-test-track trials yesterday showed that even opening arches in the front frame extensions was not enough to prevent the truck derailing. A small amount of surgery has chamfered the frames behind the cylinders, which I hope will provide sufficient swing to get the model round a 5ft 6in curve. The issues of driving wheel sideplay is yet to be sorted out, so expect some fun and games!

 

[3 LINK]

On my JLTRT 42xx, the front axle has no side play, the second maybe 1mm, the third ( motor ) rigid and the last axle same as Simon loads of side play.


I can just get mine around a 5'9" curve, but the problem was not so much the wheelbase but the pony wheels pressing on the inside edge of the cylinders.

Martyn.

 

[Heather Kay]

Thanks for that Martyn. It seems the best way forward. I may have to lose the etched bolt detail behind the rear wheels to allow some sideplay without catching!

Thanks to everyone that has provided images, info and so on. I also have a wealth of information in books and magazines on loan, and sight of the frame drawing for the mid-1920s stepped frame version. It's thrown up some interesting things I need to follow up.



I printed it out as large as I could, then set about it with coloured felt tips. These help me identify the frames, motion, brake rigging and sanding equipment without having to peer intently at the various lines. A couple of things pop out immediately, the first being - for this variant at least - the front sand boxes are inside the frames. I was under the impression from the 'structions they were outside, squeezed in between the cylinders and brake hangers. Anyway, at least I know where the brake cylinder lives, and how it's connected to the pull rods and cross shafts.

 

[Heather Kay]

Thoughts turn to how to get sufficient sideplay in the rearmost drivers. On the real thing the rear drivers were treated almost as a radial truck, with neat joints on the coupling rods to allow swing, and the frames joggled in to help.

Here is an extract from the frame drawing, marked up for clarity.



You can see the joggle quite plainly.



On the model the joggle ought to start about where the twin rows of rivets are. I have marked on the wheel diameter. Obviously there isn't a joggle. To be fair, it probably wouldn't be noticeable, even though it would actually be quite useful at this scale!

I have considered whether removing the half-etch overlay behind the wheels would help me. I'm still considering this option, as it is rather drastic.



Other things to consider. The arrow shows the rear of the loco. Red lines mark the wheel diameter and a hole for the plunger pickup. Just above and left of the pickup hole is the brake hanger. Green shows half-etched detail that could usefully be sacrificed. Cleaning the area behind the wheel would mean the detail won't catch the spokes on an extreme curve. While the detail would actually be visible, the cab step helpfully obscure things at this point. The wheel still needs a spacing washer to avoid touching the frames and causing shorts, of course.

So, my first step will be to remove the half-etched detail within the radius of the wheel. If that doesn't give sufficient sideplay, the nuclear option is to remove the overlay from the vertical frame join rivets backwards. The hornblocks and axle boxes are set back a little, so I could gain almost a half millimetre each side by doing that.

 

[Heather Kay]

Well, it seems removing the half-etch detail was enough. So, with no sideplay on the leading axle, some on the second, none on the third (powered) and loads on the fourth, the monster will crawl through my minimum radius reverse curves without derailing - most of the time.



You have my permission to chuckle. This rather ungainly concoction was a way for me to simulate the weight of the bodywork without having to trim back the crankpins to clear steps and slidebars just yet! Gentle shoving back and forth showed things ought to just scrape by without shorting and derailing.

I suppose the next stage ought to be wiring things up and getting electrickery in the mix.

 

[Heather Kay]

Baby steps. I put the provided motto/gearbox in and fed it some power. I don't know the provenance, so I was pleasantly surprised when it ran fairly sweetly.

That was until I changed direction.

I am not terribly gearbox clever, so I am at a bit of a loss as to why it would be noisy in one direction and not the other. Any ideas.