An Anniversary Parallel Boiler Royal Scot with CSB

Morning all!

If anyone knows of any more appropriate hornblocks to test for my project, I’d love to hear from them.

The ABC motor/gearbox arrived in the post yesterday and, on checking the measurements, is 15.4mm across the frame. This means slightly less butchery required if I went with the Griffin option but, frankly, I think they’re too good to butcher full stop!

As the hornblocks are not really visible on the PBRS, my ideal would be a clean, slim, simple set up that just went about its job of providing some accurate sliding surfaces.

Thoughts gratefully received!

I would suggest that the problem is not the axleboxes and horns but the narrow width of the spacers; 24mm is not a lot and will give a huge gap between the wheels and the frames. I've just use 26mm on the FS Hall that I am finishing.
Simon

Thanks Simon - but I’m pretty much stuck with them, regrettably. I’ve no facility to completely remaster them, particularly the ones that have some kind of role securing the body onto the frames. Outside dimension 25.8mm, back to back 27.7mm - 3 scale inches... is that going to look way out?

Sorry - 1.5 scale inches either side.

Depending on your curvature or amount of sideplay then yes it'll look too much.

Not sure where your 27.7mm back to back comes from (probably check rail to crossing which is different to wheel clearance), O fine is 29 mm between inside faces of the wheel and your frames are 26 mm (rounded) that'll leave a 1.5 mm gap each side (scale 2.57")

Unless you're running table top curves then you can go for wider frames. For six foot radius on a long wheel base engine I aim for 28 mm at the widest point, typically over etched rivets which if etched in 0.45 mm gives 27.1 mm over plate work. For shorter wheel base engines then you can push that out to 28.5 mm over rivets.

Some engines have large gaps in real life, those where the horn guides are mounted with the frame in the middle, as opposed to where the horn guides are bolted to the inside, these include Battle of Britain, Merchant Navy, Britannia, 9F etc off the top of my head; in those cases you can get your whole hand between the wheels and frames. Typically you'd be hard pressed to get even your smallest finger between frame and wheels.

Either way frame spacers are a personal choice and usually dictated by operating requirements on layout curves etc.

Mickoo, I stand corrected. I was away from my normal references this morning and had the wrong figure in mind in response to Simon’s points. 29mm+/-0.2 indeed!

I've changed the topic name slightly

Reviewing my posts, I think I'm being a bit wordy and perhaps it would benefit everyone, myself included, if I were a little more explicit when I have a question! So here goes...

Given I am pretty much forced into a narrow frame spacer scenario, can anyone recommend a good quality, slim version of horn block, ideally less than 4mm depth (into the frame) that I might not yet have considered?

Andrew,

Aaah, I like succinct!

In such tricky situations as yours I have tended to go for the Finney ones as I can slim them down a great deal and still retain their functionality. However, I'm not sure what the original Scot hornguides look like and whether there's one suitable. I am sure that the Princess Coronation ones can be trimmed down to be a fair representation of the versions fitted to the Rebuilt Scot as I have had sight of that GA (from the Wild Swan book)

Steph
Finney7 LLP (in the interests of full disclosure!)

Thanks Steph - as it's going to be very difficult to see the hornguides when in situ anyway I would certainly consider the Finney ones - they're a lovely fit and even my inner geek could happily live with them being Stanier not Fowler/North British! I think Stanier made quite a few changes, including reinforcement, when he revised the frames for the rebuilds. Looking at the GA in O S Nock's The Royal Scots and Patriots of the LMS (pp16-17) I think the originals were just the separate cheeks as per the Laurie Griffin example.

You've rumbled my Plan B - if that comes off then a lot of the problem goes away, so fingers crossed David is happy. Meanwhile I'll pause and sit on my hands for a bit. The 1st April 2018 target was always going to be a challenge so perhaps by giving myself more latitude I'll end up producing a far better finished product.

'scuse me but what is CSB?

Dave said:

'scuse me but what is CSB?

Click to expand...

Continuous Springy Beam (CSB) - it's a method of providing a sprung compensated chassis. My recent posting of the 3F chassis uses this method.

Tales from a sporadic modeller.

You have a length of spring steel wire between fulcrum points on the chassis frame and wheel bearings to provide a sprung setup.



all the technical stuff is here Continuous springy beams

Dave - many thanks for asking about CSB. Please continue following this thread and I’ll do my best to explain (from my perspective) as the build unfolds.

Unfortunately I’m forced into a short hiatus while I rethink an aspect of the kit I’m using, but as soon as I can get properly underway I’ll be sure to explain things a little better for those for whom the method is new.

andrewb said:

A bit of Sunday silliness: following on from Dave's comments above, and having reviewed the number of people who have viewed my thread I'm surprised and, to an appropriately British non-cocky extent, flattered that I have a very high hit-rate on this topic! Thank you all for your interest and support. While I also have the humility to realise that it may be symptomatic of people checking back wondering whether I'll ever get to the bloomin' point, I'd be grateful for (light-hearted please ) feedback as to whether the main interest is in:

a. Continuous Springy Beam matters
b. The Royal Scot class
c. The RAF
d. What on earth my avatar captures me doing
e. Wondering whether I'll ever get to the point
f. Nothing... I clicked on by mistake...
g. All of the above
h. None of the above

This will help determine my priorities for future posts

Click to expand...

The number of hits doesn't necessarily relate to the level of interest. Many WT members will check all the new messages so the more posts the greater number of views there are likely to be. 'Likes' are a better guide to interest. While only a proportion of members click on the like button the best way to get likes is to post photos of progress on the model as you go. As well as photos, feel free to write as expansively as you feel the need to. Readers can skim over paragraphs that don't interest them.

btw, personally I am interested in how you get on with CSB on a loco of this size, less so in the other options but don't let that stop you telling us all about them as there is bound to be things of interest. It is always good to learn from people with enthusiasm for their topic.

Many thanks Overseer - I spotted this a fraction of a moment after I had taken down the post as I had decided it could be interpreted as a little too silly, even for a lazy Sunday! But I'm glad you quoted it, thus maintaining the context, and thanks for your reply.

While not 'seeking' likes as such (although the occasional tummy rub is always welcome!) my main concern is that what I write isn't a waste of time either for the reader or, indeed, for me. I'll continue in that mindset but hope that if you, or any other reader, feels I'm missing the mark that they can give me a nudge back onto topic!

andrewb said:

. . . . . wondering whether I'll ever get to the bloomin' point, I'd be grateful for (light-hearted please ) feedback as to whether the main interest is in:
a. Continuous Springy Beam matters . . . .

Click to expand...

Andrew,
(a)
Please unleash the soldering iron and don't restrain it when on heat

-Brian McK.

Thanks Brian - normal service will be resumed as soon as possible. I’m in the process of resolving the hornblock size issue by going for wider spacers - something I didn’t really want to take on but realised I’d be unhappy with out-of-scale gaps between wheels and frames if I didn’t - and hope to start this coming weekend. I’m really looking forward to it!

Any more news on this?

Len

Hi Len - I've been really tied up with other stuff since before Christmas and have not done any building. However, I haven't been completely idle! The final etches I needed were delivered this morning: what started life as 'simply' creating wider spacers has turned into 5 sheets of metalwork as I've also taken the opportunity to super-detail some of the original components. But, most tellingly, I have had to design my own horn blocks for the CSB, as I just couldn't work out how I could achieve the required accuracy using modified, cast ones. This is what arrived in this morning's post. I'm really hopeful I now have 'all the ducks in a row', so to speak, and can get on with the project! But then again, I wrote that on 27 Nov 17, didn't I...!

I’m quite pleased with my home-spun hornblocks - I knocked a sample up in about an hour, and I think the concept is going to work.

I managed somehow to over-cook the slots for the horn cheeks, which I wish I hadn’t but it still works OK. The rivet detail was more a trial than anything, and has worked quite well. V2 would have more, accurate detail applied, but these will do for this project. The important thing is it works smoothly with minimal slop. And the tab on the axle box is exactly 7.5mm above axle centreline and 2mm ‘in’ from the inside face of the frames - perfect for the CSB wire position.