Brettell Road

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ianpenberth
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Re: Brettell Road

Postby ianpenberth » Fri Jul 17, 2015 1:27 pm

Hi Jim,
This scheme has worked ok on the four-wheeled diesel bogies, wheelbases from 8' 6" to 10' 6". Location of the outer seats is constrained by the length of the bogie frames in each case, a more symmetrical arrangement might be preferable. But it works fine as is. If CoG not central, you could go to the spreadsheets, or might prefer to experiment, to position the middle seat: no idea offhand how sensitive it would be to that.
cl33SchematicPrimary_200.png
cl33SchematicPrimary_200.png (24.01 KiB) Viewed 6710 times

Cheers
Ian
Ian
PenBits Model Railways - Diesel bogie springing and detailing

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jim s-w
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Re: Brettell Road

Postby jim s-w » Fri Jul 17, 2015 1:53 pm

The pitch problem might be something I'd want to replicate for my 15xx tank Will

https://m.youtube.com/watch?v=dlcj1H7HsiA

See 2mins 24 seconds

Is the pitch problem you refer to a theoretical or a real world experience one?

Cheers

Jim

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jim s-w
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Re: Brettell Road

Postby jim s-w » Fri Jul 17, 2015 2:09 pm

ianpenberth wrote:Hi Jim,
This scheme has worked ok on the four-wheeled diesel bogies, wheelbases from 8' 6" to 10' 6". Location of the outer seats is constrained by the length of the bogie frames in each case, a more symmetrical arrangement might be preferable. But it works fine as is. If CoG not central, you could go to the spreadsheets, or might prefer to experiment, to position the middle seat: no idea offhand how sensitive it would be to that.
cl33SchematicPrimary_200.png

Cheers
Ian


Thanks Ian

If you fit shorter springs so that there's only the 1 pivot point does it make a difference?

Cheers

Jim

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Will L
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Re: Brettell Road

Postby Will L » Fri Jul 17, 2015 2:43 pm

jim s-w wrote:Is the pitch problem you refer to a theoretical or a real world experience one?


Theoretical Jim, 'cause I for one are am convinced enough not to want to try it. But before you do, just have a think about a 4 wheel vehicle with it centre of gravity well above the axle centre line and pivoting around the centre point of your spring, were are the forces are going? What you have there is a variety of vertical pendulum. Might be Ok if the springs were so stiff that calling them a spring would be pushing the point a bit, but for springing to be of any value it does have to give a bit, and if it gives its going to pitch.

Even putting the fulcrum point at the out ends doesn't entirely fix the problem but real experience does suggest it mitigates it enough that you probably won't notice, so long as the weight isn't too far above the axle hight. Ian's right that it is hard to get them out far enough on some bogies, and off centre CofG's look doable.

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Will L
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Re: Brettell Road

Postby Will L » Fri Jul 17, 2015 3:18 pm

Will L wrote:Theoretical Jim, 'cause I for one are am convinced enough not to want to try it.

Actual, thinking about it, not just theoretical, what your suggesting is in some ways analogous to the Prickly Pear suspension system, and a wagon I built some time ago, before I new better, which was not a success. See here.. It may not be immediately apparent, but these are all essentially a weight supported above a pivot point with its sideways movement controlled (or not) by a spring.

If I wasn't going away for the weekend I could explain in detail, with diagrams, but then that would be theoretical.

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jim s-w
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Re: Brettell Road

Postby jim s-w » Fri Jul 17, 2015 3:19 pm

I see what you mean Will. But the location of the pivot is really more of an anchor. Because the spring is a tight fit in the handrail knob a force on one side is taken up between the end and the anchor. There's no movement at the anchor itself and theres no movement transmitted to the other end. It's more of a cantilever really. To that extent it's really just a vertical force acting on the hornblock and not really any different to any 4 wheeled sprung wagon. They don't tend to suffer from pitch.

I suppose the best way to find out is to try it

Cheers

Jim

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grovenor-2685
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Re: Brettell Road

Postby grovenor-2685 » Fri Jul 17, 2015 4:25 pm

Because the spring is a tight fit in the handrail knob a force on one side is taken up between the end and the anchor. There's no movement at the anchor itself and theres no movement transmitted to the other end.

If that also applies to your 6 coupled example, then it is not working as equalising beams as in the class 31 but just as simple springing.
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Keith
Grovenor Sidings

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jim s-w
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Re: Brettell Road

Postby jim s-w » Fri Jul 17, 2015 5:34 pm

Hi Kieth

i did say the springs were a tight fit earlier. Call it what ever makes you happy because I'm not at all bothered. It does what I want for very little effort or faffing arround, for a first effort at a chassis that's all I needed. The point is I used the idea behind a diesel bogie (brush or EE, both follow the same principle) to dictate that the anchor should be on a third. I used that fact to illustrate that it's the thought behind prototype and that you don't need to think much further than that. Now either this method is idiot proof and doesn't need much thought or I've been incredibly lucky.
I think it's more likely the former because an idiot did it! ;)

Are you saying it should work for an 0-4-0 then? :?

Cheers

Jim

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grovenor-2685
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Re: Brettell Road

Postby grovenor-2685 » Fri Jul 17, 2015 6:19 pm

If the springs are held tightly in the mounting then it is just 4 cantilever springs, as others have already said, in which case it should work fine. Your 6 wheel equalised design should not have had the springs held tightly, just loosely as in the diagram supplied and in the diesel bogies you compared it to.
So you have each axle suppoerted by a cantilevered spring, still works OK, just not equalised.
If you did bother with the maths you would find that the 1/3, 2/3 rule only applies to rigid equalisers as with the diesels. For cantilever springs, or springy equalising beams the numbers would be different for equal axle loads as spring rates are non-linear. So your arrangement will be lighter loaded on the centre axle, but that's OK too.
There is little or no need to worry about calculations unless you want to be anal about the weight distribution.
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Keith
Grovenor Sidings

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jim s-w
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Re: Brettell Road

Postby jim s-w » Fri Jul 17, 2015 7:00 pm

grovenor-2685 wrote:If the springs are held tightly in the mounting then it is just 4 cantilever springs, as others have already said, in which case it should work fine. Your 6 wheel equalised design should not have had the springs held tightly, just loosely as in the diagram supplied and in the diesel bogies you compared it to.


Hi Keith

Initially I did use lighter springs that were loose and it didn't make any difference to track holding. Then I added a bit more weight and stiffer springs as the sandpipes sometimes shorted? I even started with different springs on the front and back because I mistakenly figured that the weight of the motor would have an effect (didn't twig that it's unsprung weight)

Cheers

Jim

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ianpenberth
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Re: Brettell Road

Postby ianpenberth » Fri Jul 17, 2015 8:47 pm

jim s-w wrote:If you fit shorter springs so that there's only the 1 pivot point does it make a difference?


There's no rotational constraint on the central pivot (it's just a hole, a little larger than the spring wire, in a vertical brass lug) so the chassis would just fall over onto one end or the other. Maybe if you had two such seats between the axles: moving them further apart would increase the stiffness of the springing and decrease the tendency to pitch: you might be able to find a sweet spot that gave you the response you were after.

HTH
Ian
Ian
PenBits Model Railways - Diesel bogie springing and detailing

billbedford
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Re: Brettell Road

Postby billbedford » Sat Jul 18, 2015 10:28 am

jim s-w wrote:The pitch problem might be something I'd want to replicate for my 15xx tank


That's easily reproduced, you just use mercury for ballast and make sure there's plenty of free surface in its container so that it can surge back and forth........
Bill Bedford
Mousa Models
http://www.mousa.biz

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Simon_S
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Re: Brettell Road

Postby Simon_S » Mon Jul 20, 2015 11:24 am

grovenor-2685 wrote:...or springy equalising beams the numbers would be different for equal axle loads as spring rates are non-linear.


The forces on the axles and the pivots are not affected by whether they are acting through a rigid or a springy beam; the 1/3 rule still applies if we want equal axle loadings, even if the wheelbases are uneven.

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Re: Brettell Road

Postby billbedford » Tue Jul 21, 2015 8:08 am

The 1/3 rule only applies if the centre of load matches the centre of the the reaction forces. This is easy to arrange on a bogie, but less so on steam type loco frames.
Bill Bedford
Mousa Models
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jim s-w
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Re: Brettell Road

Postby jim s-w » Sun Aug 02, 2015 2:31 pm

Hi All

A while ago I wrote about the benefits of using modern techniques and processes on my website, specifically laser cutters.  However I have sort of come to change my view on this a little recently. You see, if you are doing more than 1 thing that is the same then laser cutting can offer a distinct time-saving. If however what you are doing is pretty much bespoke then the extra effort is, I have concluded, not really worth it. Take my retaining walls for Brettell Road. I did draw up the larger one but it took for ever. It turned out to be much quicker and easier to just get some sheets of embossed plasticard and get stuck in!

Image

Image

These walls use Slaters bricks and I have done the top row by cutting individual blocks from evergreen strip and gluing them in place. Even taking the time to do this (Which isn't exactly taxing but is long-winded) these walls didn't take all that long to do.

Image

Finally this is pretty much what I hope Brettell Road will be all about, dark and wet! It's always been my intention to depict a rainy  night somewhere in the Black Country and this is the first time I've really been able to get an image that illustrates what I am looking for (although perhaps, not this dark!)

Cheers

Jim

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Re6/6
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Re: Brettell Road

Postby Re6/6 » Mon Aug 03, 2015 6:15 pm

Looking excellent Jim.
John

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CDGFife
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Re: Brettell Road

Postby CDGFife » Thu Aug 06, 2015 5:45 pm

All my Black Country rainy night railway memories are of sitting in New St waiting for the (blue diesel) train home to Wolves and therefore more suited to your other work! However this is looking really lovely.

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jim s-w
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Re: Brettell Road

Postby jim s-w » Fri Aug 21, 2015 12:09 pm

Thanks both

Image

I've started on the buildings for Brettell road with one that locals to the Stourbridge area will recognise as heavily influenced by the bonded warehouse. Construction is based on 2mm card overlaid with South Eastern Finecast garden wall bond. The large tiles were  kindly laser cut for me by Tim.  I get a kind of perverse satisfaction by putting the interesting bits facing away from the viewers!

Image

The public facing side is plainer than a really plain thing. Only the little bit of detail at the top of the smaller building giving any vague nod to any sort of design or creativity!

Image

I plan to depict this building as abandoned, with all sorts of clutter in the now disused courtyard area. The base of the courtyard is foam-board and bearing in mind my wet theme I cut some holes in the top surface so that I could heat the plasticard with a hairdryer and give some variation to the floor for puddles. You can see how I approach the top of the wall with individual evergreen bricks (some missing of course!)

Image

Close up of the courtyard showing the battered doors. I decided to depict the main building chained up with the now customary padlock in place!

Cheers

Jim

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jim s-w
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Re: Brettell Road

Postby jim s-w » Tue Sep 29, 2015 7:09 pm

Hi all

My abandoned warehouse is nearly there now. A spot of paint, Brassmasters windows and roof tiles kindly supplied by Mr Horn. These images show it roughly positioned.

Image
Unusually for me the more interesting side is actually the side that people will see! The yard has been suitably strewn with waste from plastic strip and Scalelink bits. The 2 tanks are from Unit models.

Image

Cheers

Jim

BrockleyAndrew
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Re: Brettell Road

Postby BrockleyAndrew » Mon Oct 05, 2015 6:13 pm

Hi Jim

Firstly, thanks for your advice, I enjoyed chatting to you at Scaleforum and bothering you with fairly basic questions about windscreens and windows for cars.

I like your dark, rainy night scene. Have you chosen time of year? Has anyone tried exhibiting a night scene? Even a letterbox viewing system would surely let in too much ambient light!

Andrew,
Brockley SE4

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jim s-w
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Re: Brettell Road

Postby jim s-w » Tue Oct 06, 2015 8:47 am

Your welcome Andrew

I've always thought of late-ish October for the time of year. There was a night exhibition layout at Wigan that seemed to work pretty well. It's not so much that the layout has to be dark, just darker than you would expect ;)

Cheers

Jim

dal-t
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Re: Brettell Road

Postby dal-t » Tue Oct 06, 2015 9:16 am

Most commercial model railways displays (yes, I confess I've visited a few in various countries over the years) seem to feature a 'night scene' where they turn all the house lights off. Personally, I've never been impressed - it seems to simply be an opportunity to show off how many special effect lighting units they've installed, from flickering 'gas' lamps to glowing bonfires/braziers and moving searchlights illuminating the 'sky'. Creating the sort of atmosphere coming through in Jim's photos would be something else altogether, but although it is clearly difficult to overcome the ambient light problem - how irritating that most exhibition venues are too badly lit for 'daylight' viewing, but too bright for night-time! - I take Jim's point about it just having to be darker than expected, so putting the layout in a semi light-tight box with narrow viewing slit ought to get close to the desired effect. There's also the wet and windy aspect, of course, so how about combining the 'darkness' with some water nozzles mounted on the fascia to drench the unsuspecting audience from time to time, and a floor-level aircon unit to shoot icy draughts up trouser legs when least expected? Then you're starting to get close to the 'real' railway on a damp October evening ...
David L-T

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Paul Townsend
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Re: Brettell Road

Postby Paul Townsend » Tue Oct 06, 2015 10:03 am

BrockleyAndrew wrote: Has anyone tried exhibiting a night scene? Even a letterbox viewing system would surely let in too much ambient light!

Andrew,
Brockley SE4

A couple of years ago at Cardif MREx I saw a small but delightful operating model of the yards in and around a steel works at night.
It was probably no more than 6' x 2' + Fiddle and contained in a theatre Proscenium arrangement.
Low level of light inside the model obviously and the ambient light was controlled by a hood that extended several feet forward over the punters.
It worked very well.

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Guy Rixon
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Re: Brettell Road

Postby Guy Rixon » Tue Oct 06, 2015 9:31 pm

It doesn't have to be that dark to be realistic. Firstly, it could be a moonlit night. Secondly, the sky in urbanized Britain - and the Black Country isn't exactly rural - is very bright with airglow and light reflected off cloud. Just try some naked-eye astronomy in the Midlands and you'll see the effect.

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jim s-w
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Re: Brettell Road

Postby jim s-w » Thu Oct 08, 2015 1:17 pm

The layout I saw at Wigan had a blue fabric roof and that seemed to give a nice coloured light. I like the idea of extending it over the viewer. When we were in Austin several stores had misting systems outside to give a respite from the humidity. They were really nice but I doubt that the average exhibition goer would get that sort of benefit! I have thought of a wet grass air freshener though.

Cheers

Jim


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