Brettell Road

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jim s-w
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Re: Brettell Road

Postby jim s-w » Sat Jan 10, 2015 10:13 am

Thanks Noel

Black is definitely the most likely and safest option.

It really is a world apart from modelling more recent themes where colour images are common (obviously) but I have been surprised at how different it is.

Cheers

Jim

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jim s-w
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Re: Brettell Road

Postby jim s-w » Mon Jan 12, 2015 10:23 pm

Hi All

I've been busy finishing off some stock for Brettell Road.  Starting with some wooden opens.

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The Tube is an old Colin Ashby kit and is sprung with Bill Bedford springing units. I think you can get a kit for these wagons from Chivers now. These wagons have been weathered to look wet but you cant see it in the picture.

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Back to the loco that started the whole project my GBL Jinty.

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Cheers

Jim

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jim s-w
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Re: Brettell Road

Postby jim s-w » Thu Mar 05, 2015 8:12 pm

Quick question, when is a shark not a shark?

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When it's an oyster. Been hacking a cambrian shark kit to represent the earlier oyster. For more see

http://www.p4newstreet.com/the-origin-of-species.html

Cheers

Jim

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jim s-w
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Re: Brettell Road

Postby jim s-w » Thu Mar 05, 2015 9:00 pm

I've always liked engineers trains (what do you mean, we know?) so a short one for Brettell Road was always going to be on the cards.  I've shown you my build of a gannet before but now it's painted. 
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Shown here with a Cambrian starfish ballast open.  

From one of thier old kits to one of thier newest, the recently released herring ballast hopper. There were 2 very different designs of ballast hopper given the herring title. One of them was closely related to the mackerel and of the catfish ilk (walkway one end, single hand wheel).
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The Cambrian kit is for the GWR design and it suffers from the same problem the gannet had, that being to discharge the ballast a track worker had to stand by the side of the wagon, right next to where the falling ballast is going to be. It's a diminutive little wagon and features a one piece hopper and a one piece chassis, the latter being a big improvement on the catfish and dogfish kits. For such a small wagon there's a lot of details to be added and the underside shows a nicely pleasing complicated look.  Of course most people probably won't notice so if you wanted a rake you could probably miss a lot of this stuff off but having said there nothing that's really tricky if you take your time.
I swapped the buffer heads for MJT ones and drilling the shanks for these proved a bit tricky with the sides ending up really thin. I didn't spring them (never do) but think the metal heads are a worthwhile improvement. 
Some of the smaller parts had quite a bit of flash on them which was a bit of a surprise as most Cambrian kits I have built recently didn't have any. That's the only negative of what is a nice little kit.
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I have a couple of Tunnys still to do and I might throw in a catfish too but that's for another day.

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jim s-w
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Re: Brettell Road

Postby jim s-w » Tue Mar 17, 2015 8:14 pm

Been bunging a few more wagons together

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Image

Cheers

Jim

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jim s-w
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Re: Brettell Road

Postby jim s-w » Tue Mar 24, 2015 9:59 pm

Been doing some experiments on modelling rain

Image

More on my website

Jim

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David B
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Re: Brettell Road

Postby David B » Tue Mar 24, 2015 10:13 pm

jim s-w wrote:Been doing some experiments on modelling rain


. . . . ?? Go on, Jim. Do tell. Please. This looks great.

DougN
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Re: Brettell Road

Postby DougN » Tue Mar 24, 2015 11:15 pm

Read up again Jim... looking really nice. The idea of the layout being viewed after Rain is an interesting and challanging one as you are finding. I bet a few new skills have been created by this.

I still have a hankering for a P4 layout just need some time free to do it. :D
Doug
Still not doing enough modelling

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jim s-w
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Re: Brettell Road

Postby jim s-w » Wed Mar 25, 2015 7:09 pm

David B wrote:
jim s-w wrote:Been doing some experiments on modelling rain


. . . . ?? Go on, Jim. Do tell. Please. This looks great.


It's actually surprisingly simple. Do the water with layers of varnish as per Gordon Gravetts book, then sprinkle baking soda onto another layer of wet varnish. Let it all dry and coat it with another layer or 2

HTH

Jim

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David B
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Re: Brettell Road

Postby David B » Wed Mar 25, 2015 8:34 pm

Thanks Jim.

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Guy Rixon
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Re: Brettell Road

Postby Guy Rixon » Thu Mar 26, 2015 12:19 pm

jim s-w wrote:
David B wrote:
jim s-w wrote:Been doing some experiments on modelling rain


. . . . ?? Go on, Jim. Do tell. Please. This looks great.


It's actually surprisingly simple. Do the water with layers of varnish as per Gordon Gravetts book, then sprinkle baking soda onto another layer of wet varnish. Let it all dry and coat it with another layer or 2

HTH

Jim


Fascinating - and looks good. The baking soda blows bubbles into the varnish to represent the raindrops striking the puddles?

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jim s-w
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Re: Brettell Road

Postby jim s-w » Thu Mar 26, 2015 2:04 pm

That was my thinking

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jim s-w
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Re: Brettell Road

Postby jim s-w » Tue Jul 14, 2015 12:05 pm

Hi all


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No I haven't put this in the wrong place and yes this is a bogie off a class 31 but it serves to show how the real thing goes about springing 3 axles. When I first wrote about building the chassis for my Jinty I didn't go into too much detail on how it was sprung, mainly because I wanted to check that it worked properly before telling people how to do it (or leading them down the wrong path , possibly!). In truth I knew it would work as when my friend Simon built his fully spring class 31 (from a Bill  Bedford kit) he sprung it using a similar principle. AS he's an engineer and I've seen his 31 perform faultlessly on may occasions there was little to worry about other than I possibly didn't get it or couldn't do it!

Anyway after a few days of shuffling wagons around on Brettell Road  I feel confident to tell you how it was done. I admit off the bat that CSB's work and work well as I've seen many examples of them (Continuous Springy Beams). I also admit that all the maths, tables and discussion put me right off the idea from the start. It just seems so 'faffy' somehow. Sure they first appeared when there was an element of the finescale side of the hobby who likes to pretend they were actually Stephen Hawking and seemed to revel in making things look as difficult as possible but there was always the thought in the back of my mind that a lot of the clever theory, whilst fine on paper, didn't actually translate to any effect in the real world. That and why don't real 3 axle vehicles do it that way then? (Yes I know a Jinty isn't sprung like a class 31 either!)

The principle of equalised springy beams is very simple. If you have a beam with a pivot in the middle the effects on either end will be the same. If you move the pivot to a 3rd of the way along the effects are more on one end than the other, By using 2 beams on 3 axles, with 2 of them acting on the center axle and the pivots towards the outer axles, the effects on all 3 should be about the same. It's a mix of old-fashioned, very rigid compensation beams and springs to get a sprung result. I am sure that you can apply loads of complicated maths to this to refine the thinking further but it works for me, appeals to me KISS approach to things and all you need is 4 handrail knobs and 4 springs of 18 gauge guitar string. Nothing has to be pivoted and you can just change the gauge of the springs to adjust the effect.
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HTH

Jim

dal-t
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Re: Brettell Road

Postby dal-t » Tue Jul 14, 2015 4:11 pm

What's the effect of the 6", Jim (Jinty wheelbase is 8' x 8'6", isn't it?)? And what about locos with even more unequal wheelbases (e.g LNWR Cauliflower with 7'3" x 8'3")? Does the centre axle bounce more in one direction than the other, or do you vary the thickness of the wires?
David L-T

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Will L
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Re: Brettell Road

Postby Will L » Tue Jul 14, 2015 4:22 pm

I agree that separate springy beams like this will work quite nicely, though of course this isn't really how a class 31 does it either. Nothing springy about the beams on a class 31 chassis. (As an aside, I'd be interest to know how you ensure the springy beams stay put where they are supposed to be.)

What I don't get is this theory that you need to be all mathematically involved to determine where the fulcrums on a CSB need to go. My version of the spread sheet will give you a good enough answered if you just plug in the wheel base which is hardly a lot of faff. As a bonus, and for no further faff, it will also tell you where you need the centre of gravity of the loco to be if you want the best performance and (in extreme cases) for it to sit level, and what size wire you need for a given weight of loco.

Better still ask on here and some smart a**s (often not even me) will post the answer before the sun sets. Once you have that, what's the difficulty? There's more maths involved in working out where your 1/3 - 2/3 points are.

The fact that Russ used to quote fulcrum point positions to two places of decimals was a bit off putting I agree, but I though we were well past that and have now agreed that the nearest 0.5mm will do.

That the CSB method is underpinned by a mathematical model that allows the numerically minded to understand what's happening and pontificate about it at length, should not be allowed to obscure the fact that CSBs are a simple to build and and reliable in action method of obtaining a fully sprung chassis that is fully KISS compliant. Much simpler to build, and will run just as well if not better, than many a fully compensated, or individually sprung chassis systems.

As to why the real thing didn't do it that way? Well what's practical in different sizes changes a lot,and I suspect a single springy beam doesn't scale up any better than multiple leaf springs scale down. Even then a lot of American loco's sprung/compensated arrangements come out got pretty close to what a CSB does. As close as that class 31 bogie is to a 0-6-0 with 4 overlapping springy beams for instance.

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jim s-w
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Re: Brettell Road

Postby jim s-w » Tue Jul 14, 2015 5:07 pm

dal-t wrote:What's the effect of the 6", Jim (Jinty wheelbase is 8' x 8'6", isn't it?)? And what about locos with even more unequal wheelbases (e.g LNWR Cauliflower with 7'3" x 8'3")? Does the centre axle bounce more in one direction than the other, or do you vary the thickness of the wires?


Hi

No noticable difference at all. I did try lighter springs on the front to allow for the gearbox and motor hanging on the rear axle before I realised that the extra weight on the axle was unsprung weight anyway - DUH! The different springs didn't make any difference either!

Cheers

Jim

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jim s-w
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Re: Brettell Road

Postby jim s-w » Tue Jul 14, 2015 5:20 pm

Will L wrote:I agree that separate springy beams like this will work quite nicely, though of course this isn't really how a class 31 does it either. Nothing springy about the beams on a class 31 chassis. (As an aside, I'd be interest to know how you ensure the springy beams stay put where they are supposed to be.)


Hi Will

True but the beams on a 31 are sprung. I was using it more for an example of how the idea of thirds work. The beams are a tight fit in the handrail knobs and thier movement is restricted by the cross braces in the chassis

What I don't get is this theory that you need to be all mathematically involved to determine where the fulcrums on a CSB need to go. My version of the spread sheet will give you a good enough answered if you just plug in the wheel base which is hardly a lot of faff. As a bonus, and for no further faff, it will also tell you where you need the centre of gravity of the loco to be if you want the best performance and (in extreme cases) for it to sit level, and what size wire you need for a given weight of loco.


I did say it put me off in the beginning. Don't forget that you would need further modification of the chassis too to allow for the outside pivots. I appreciate the work you've done to dispell the myths.

The fact that Russ used to quote fulcrum point positions to two places of decimals was a bit off putting I agree, but I though we were well past that and have now agreed that the nearest 0.5mm will do.


Didn't realise that. See what I mean about being put off at the start. I admit though that most stuff on E4um used to go over my head anyway, plus I've never really needed to pay any attention to the subject since.

That the CSB method is underpinned by a mathematical model that allows the numerically minded to understand what's happening and pontificate about it at length, should not be allowed to obscure the fact that CSBs are a simple to build and and reliable in action method of obtaining a fully sprung chassis that is fully KISS compliant. Much simpler to build, and will run just as well if not better, than many a fully compensated, or individually sprung chassis systems.


True and not having done one I can't say. I'm sure a properly worked out CSB chassis would be better than what I have done but my method uses less parts and required less modification to the chassis ( the high level jinty wasn't designed for CSBs) so it seemed easier for a first attempt. It works how I hoped so I'm happy.

As close as that class 31 bogie is to a 0-6-0 with 4 overlapping springy beams for instance.


A class 31 has 4 overlapping solid beans. It's just that the springs act on th beams and the beams themselves aren't springy.

I'm not advocating anyone should do it this way but it's an option and it worked for me :)

Cheers

Jim

billbedford
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Re: Brettell Road

Postby billbedford » Wed Jul 15, 2015 7:59 am

How do you work out the spring rates for those coil springs? especially if you have unequal wheelbases?

It seems to me that as soon as you move away from a simple model with evenly spaced axles and a fixed CoG you will run into the same problem that CSBs have, i.e. that calculating the spring rates is a mathematically indeterminate problem. Hence the spreadsheets.
Bill Bedford
Mousa Models
http://www.mousa.biz

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jim s-w
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Re: Brettell Road

Postby jim s-w » Wed Jul 15, 2015 2:28 pm

Why do you need to Bill?

Jim

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ianpenberth
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Re: Brettell Road

Postby ianpenberth » Fri Jul 17, 2015 10:59 am

Thanks, Jim, for showing that the "four springy beams" scheme works for a six-coupled wheelbase - I'd been wondering about that.

It is, as you pointed out, a great way of modelling the primary springs on a 6-wheel diesel bogie, being as it's how the real thing does it in most cases. Whether they're rigid beams mounted on coil springs or springy beams on rigid foundations makes no difference to the response at the wheels. I use them on my bogie kits, as described here: http://www.penbits.co.uk/Content/TechDesc.html#BogieS.
Ian
PenBits Model Railways - Diesel bogie springing and detailing

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grovenor-2685
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Re: Brettell Road

Postby grovenor-2685 » Fri Jul 17, 2015 11:14 am

Thanks, Jim, for showing that the "four springy beams" scheme works for a six-coupled wheelbase - I'd been wondering about that.

Started doing tenders that way in 2003, see http://www.norgrove.me.uk/tender.htm "Inner frames" (And it is in the digest!)
Regards
Regards
Keith
Grovenor Sidings

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ianpenberth
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Re: Brettell Road

Postby ianpenberth » Fri Jul 17, 2015 11:25 am

Hi Keith,
Yes, I was thinking more about the coupling rods...
Cheers
Ian
Ian
PenBits Model Railways - Diesel bogie springing and detailing

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grovenor-2685
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Re: Brettell Road

Postby grovenor-2685 » Fri Jul 17, 2015 11:37 am

There's no effect on the coupling rods any different than with any other variety of springing or compensation, you just use the normal 2 part rods.
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Keith
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jim s-w
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Re: Brettell Road

Postby jim s-w » Fri Jul 17, 2015 11:43 am

Do you guys think you could just use a centrally mounted springy beam on an 0-4-0 too?

Cheers

Jim

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Will L
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Re: Brettell Road

Postby Will L » Fri Jul 17, 2015 1:00 pm

jim s-w wrote:Do you guys think you could just use a centrally mounted springy beam on an 0-4-0 too?


Not directly as you have nothing to stop it pitching back and forward. Would be a bit sensitive to Centre of Gravity placement too. Holding a spring rigidly in the middle ( i.e. two independent one ended cantilever springs that happen to meet in the middle), should be ok for a bogie, where you've got the rest of the vehicle to stop it playing games, but for an 0-4-0 you would probably still have a pitch problem.


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