Radius Testing - Practical Experiments.

Discuss the prototype and how to model it.
Knuckles
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Radius Testing - Practical Experiments.

Postby Knuckles » Wed Oct 24, 2018 8:33 pm

As the title suggests really.

I've been planning a few layouts for a while and the big dream layout I have not decided whether to do in 00 or P4.

Initially I scrapped the P4 idea for this particular layout because the 'minimum' curve radius of 48" wouldn't fit.
However, after spending several hours here and there reading posts on here and elsewhere it seems you CAN get a pacific or 9F around a 24-30" curve with a lot of side play and gauge widening.

With that in mind I redesigned the plans.
The big plan I now have MUST have a minimum radius of 34" other wise it is perfectly impossible. This isn't an issue of aesthetics but rather restricted space - the usual bane.

So the requirements for the proposed big layout is 34" minimum radius, must be able to use a black 5 and a Gresley A1. That's it. I do not currently believe I have the skill to build them well enough, yet one day if I keep at it there is no reason I can't achieve it eventually.

As I'm still pulling my hair out whether to do this particular layout in 00 or P4 I decided to conduct some practical tests. In line with my way of thinking there is no calculations, theory or algebra. Good luck to those who comprehend it.

Using a set of radius curves I brought from the stores a few years back the tightest one was 120cm. A quick online converter reveals it to be a little over 35" radius. Considering I need a 34" curve minimum this is rather worrying.

Using some C&L (underside moulding says K&L so it may be old) flexible track that is sometimes a wee tight to gauge I bent it to the curve.

Now I believe the laser cut curves represent the center line to draw meaning the curve I stretched will be tighter.

Other than the P4 Hymek and CoBo I have the tests were done with the rest of my current collection.

1) - LB&SCR E2 as Thomas - Own SCC kit built compensated. Runs amazing.

2) - Furness J1 - Own SCC Kit with a bit of play added. Runs good but teeniest bit jerky, barely noticeable.

3) - LB&SCR E2 chassis - South East Finecast. I built it with Alan Gibson sprung hornblocks. Runs good but teeniest bit jerky, barely noticeable.

4) - 5700 Pannier as Duck - Bachmann model converted with Ultrascale drop in wheelsets. Runs well, could do with more reduction though.

5) - 5700 Pannier. Bachmann Pannier with kit built chassis. Not built by me, runs well but not the smoothest of starts. Brought in a job lot.

6) - 1400. Old Airfix or Dapol with propeller/cardon shaft. Not converted by me. Didn't run when brought in same aforementioned job lot. After some monking about I got it working. Runs pretty well considering age.

Loco's built by me are set with a back to back of 17.75mms.

So all these locomotives ran through the mystery radius in both directions (wheelbase considerations) at slow and fast speeds.

Test 1 is green.

Then I bent the mystery radius a bit more. All went through fine although the kit pannier would fall off sometimes in one direction.

Test two mostly green with a shot of amber.

So then I dug some stuff out my box. These....


Image

I THINK they are 0.2mm gauge widened although maybe 0.1mm? I'll get the track gauges out later and find out. (Edit: 0.2mm yep)

Slid some rail through and made a test meter.

Everything passed with this track at the first mystery radius.

Test 3 green.

Then I bent it into another mystery radius that looks HORRIBLE! No idea what radius it is yet I am sure it is tighter than 34 inches. After smoothing the curve I managed to get all these locomotives to run through at all speeds in both directions.

The Panniers & 1400 have their rear wheel to next wheel as a 34mm wheelbase.

The Hornby Black 5 I have shares this measurement so in theory, considering the wheels are bigger if I build one one day it should go around a 34" curve easily providing it has the same side play these locomotives of the tests have, setting the back to back of the black 5 to 17.67mm should give it a gnats fart extra compared to the 17.75 standard I currently roll with. The side play of these locomotives were not measured but they range from basically 0 to 1mm.

Pics. Look at that horrid tight curve!!

Image

Image

I know full well tight curves are risky and not favored but unless you fancy bunging me £300,000 or more I got no choice! :D

This layout would very much like to build. 10-20 year projected time as a guess.

Any comments or advice very much wanted. I know a box of well smoked pigs ears are likely waiting for me around the corner and avoiding them is desired!

Edit: Typo's fixed.
Last edited by Knuckles on Thu Oct 25, 2018 6:28 pm, edited 1 time in total.
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grovenor-2685
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Re: Radius Testing - Practical Experiments.

Postby grovenor-2685 » Wed Oct 24, 2018 10:46 pm

Running the loco is not the whole story. What do you wnt to couple up to them?
With the black 5 the crucial issue is the front overhang and resulting bogie swing. And even if you manage to get that working on the tight radius the buffers are not going to meet up with anything you couple it to.
The tight radii will be fine if you are happy with the resulting limitations on stock and operability.
Regards

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jim s-w
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Re: Radius Testing - Practical Experiments.

Postby jim s-w » Thu Oct 25, 2018 12:38 am

Was going to say exactly what Keith said. It’s couplings that are the defining factor. If you think about it. If you have a 00 gauge bo-bo diesel that can easily go round first radius curves, swapping the wheels and track to P4 it will still easily go round first radius curves. You might need to keep the bogie mounted tension locks and RTR coupling spacings if you want to run a train though.

The catch 22 is the more sideplay you have, the more potential for buffer locking you introduce.

Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Thu Oct 25, 2018 5:01 am

Ok thanks you two.

I have been thinking about that too.

Screw, 3 link & Dinghams is what I want although I know they can lock. Was thinking coaches could be 8n fixed rakes and could keep their RTR couplings on and have aconverter for the end.

Also plan has it that coupling would only happen on a straight and trains would not need to ever propel stock so buffers shouldn't need to be used other than on one track which would possibly have the alternate couplijgs in a set rake.

I did an experiment and made a Dingham to tension lock converter that was basically a loop on a pole joined to a tension hook on a coach. Would need refining but it seemed to work mostly.

I hate tension locks with a passion by the way. Still mulling ideas.

I'm sure there is a way to solve the coupling problem fully. Main initial issue is the curves because if I can get to run what I need then that's the biggest thing out the way.

Any coupling suggestions apart from the above?

Again I know I'm on the wire with all of this but I'm given no choice if I want this particular layout in P4.
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Guy Rixon
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Re: Radius Testing - Practical Experiments.

Postby Guy Rixon » Thu Oct 25, 2018 7:59 am

On the tightest curves, will the stock be hauled or propelled? If it has to be pushed round the worst curves, then side buffers probably aren't going to work well and you need a coupling that takes the buffing forces. At that point I'd look at DGs.

Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Thu Oct 25, 2018 9:49 am

There is only one curve that would need to push a rake of coaches so the only major issue there...I think.
The rest would be pulled.

Will look at DGs thanks.

EDIT: Hmm,looked at DG. I like the way they look.

Can they be fixed to the beam as per prototype and Dinghams? They look to be very Dinghqm like but with the pad to do the pushing.

Thinking if they can go between the buffers them some semi compatibility for just those special considerations might be able to be arranged.

What you think? Might order some and piddle about.

Any advice on best cheap n easy to convert bogie coaches that will accept a basic wheel swap easily? Not bothered about how good they look, just for function tests.
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nigelcliffe
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Re: Radius Testing - Practical Experiments.

Postby nigelcliffe » Thu Oct 25, 2018 10:14 am

DGs work (I know someone with a large EM layout under construction using them), and they've a long history in 2mm scale where the first versions were designed. But they're not a magic solution to everything, there are constraints in their width (even if a non-standard loop shape is formed).

This isn't P4 vs OO, it applies regardless:

The issue on tight radii is over-hang and vehicle alignment. With a short overhang vehicle the couplings can be fixed to the buffer beam, be they scale, DG or tension-lock (or anything else), and all is fine provided all vehicles have similar overhangs and similar wheelbases. Then the swing at the ends lines up.
But, a longer overhang will mean the swing in the coupling can pull an adjacent vehicle off the rails, unless its overhang swing exactly matches the movement on the adjacent vehicle.

As to what can be "got away with", that will depend on the overhang on stock, the radius of the curve, the transition into the curve (if its abrupt, the first vehicle is on "full swing" and the second on "straight" and gets pulled off the track), and if there are any reverse curves (cross-overs on parallel lines for example) which result in swing in opposite directions.

Practical way out will probably be some short wheelbase and short overhang stock can have buffer beam mounting, but longer stock, and probably bogie stock, cannot be fixed to the buffer beam. Its possible that the eccentric extension arm (found on some coaches) is useful in keeping stock fairly close on the straights.

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David Thorpe
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Re: Radius Testing - Practical Experiments.

Postby David Thorpe » Thu Oct 25, 2018 11:02 am

I've had some problems with Dinghams on bogie coaching stock going through a crossover on my layout. Basically, the loop on the Dinghams was too narrow to accomodate the swing of the hook on the adjoining vehicle, thereby causing derailments. Or at least I think that's what caused them. I have therefore modified some of my Dinghams following the method shown on page 2 of http://www.rmweb.co.uk/community/index. ... detailing/ (there's also some useful stuff on bufferbeam furniture on page 1). It was fiddlier than I thought it would be, but initial results on the first 3 coaches I've fitted seem promising though not yet conclusive - I've still to do some slightly longer stock.

DT

Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Thu Oct 25, 2018 3:01 pm

Thanks you two.

With the loft work, preparation and frame work being almost done I think best bet may be build the boards then I'll have a proper canvas to test things on before any solid decisions are made. Board joins and turnout clearance already planned.

Current thinking then is to buy some DGs, convert a few coaches to P4 and see what will or won't do a 34" curve.

Again I'm all ears to avoid the pigs ears!
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Armchair Modeller
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Re: Radius Testing - Practical Experiments.

Postby Armchair Modeller » Thu Oct 25, 2018 4:05 pm

Of course, there's always N gauge ;)

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Andy W
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Re: Radius Testing - Practical Experiments.

Postby Andy W » Thu Oct 25, 2018 6:13 pm

Knuckles, can I suggest you build a test segment in both P4 and OO to see which you feel comfortable with and which works as a test, before setting of on one road or the other?
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Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Thu Oct 25, 2018 6:14 pm

Armchair Modeller wrote:Of course, there's always N gauge ;)



Already modelling N!

https://www.youtube.com/watch?v=-vv5KammA34
Small layout for my room as a side project. Also above pictures shows evidence of a N gauge terrace I am designing for the layout. 3D printing it.

I never fully abandoned 00 either and have dabbled in 0 so really I model 3 (4) different scales/standards.

My heart is very much fixated on P4 though, that's what I want to be the main focus.
Last edited by Knuckles on Thu Oct 25, 2018 6:29 pm, edited 2 times in total.
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Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Thu Oct 25, 2018 6:17 pm

Andy W wrote:Knuckles, can I suggest you build a test segment in both P4 and OO to see which you feel comfortable with and which works as a test, before setting of on one road or the other?



I did a test layout in P4 before so already know I like P4 and can do it.

If you mean for the curves I intend to. :) Read above with the mention of me building the main baseboards but for trials and tests to take place on top first.

The layout I want has been in the designing on and off since 2011 and has gone more revisions than I can remember, done 00 and P4 versions of it and the baseboards are the same for either so all ok on turnout locations and joins etc.


Thinking of trialing those DGs and converting a few coaches to P4 first. That way I can hopefully conduct some more in depth trials to see what will work or not.
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Noel
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Re: Radius Testing - Practical Experiments.

Postby Noel » Thu Oct 25, 2018 9:52 pm

There is another potential issue with bogie coaches [and bogie bolsters, etc possibly]. R-t-r coaches have solebars which are much thicker than the prototype, and the tops of the wheels are normally behind them. In OO this doesn't normally matter, although even then the wheels will eventually foul the solebars if the curve is sufficiently tight. P4 wheelsets are wider, so will foul the solebars sooner. Whether this might become a problem at the sort of radii you intend to use I don't know, but you may need some extra clearance.
Noel

Philip Hall
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Re: Radius Testing - Practical Experiments.

Postby Philip Hall » Thu Oct 25, 2018 11:32 pm

Gavin,

The close couplings supplied as alternatives by Bachmann and Hornby will work on ridiculously silly curves very well, and they are currently my standard for couplings within a rake for corridor stock. No need for sprung buffers inside either. Not so for non-gangwayed stock where it is easier to see the couplings. Possibly this kind of ‘expanding’ coupling could be adapted here to represent screw couplings and hoses, like the cast brass ones available. I would suggest that you also make sure each bogie vehicle is weighted well (I use 180 grams minimum) as this will help the body of a carriage to stay steady regardless of the gyrations of the running gear which will appreciate the weight to help it stay on the rails.

If you have a problem, solebars can be thinned at the rear to wafer thin dimensions which for your curves should just be enough. I was at one time planning for Maunsell carriages to be stabled in sidings down to 30” radius, but only viewed from the inside of the curve, which makes it look less awful.

The mechanicals are possible in various ways, but the trick will be to make it look OK. Good luck...

Philip

Terry Bendall
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Re: Radius Testing - Practical Experiments.

Postby Terry Bendall » Fri Oct 26, 2018 6:58 am

Knuckles wrote:The layout I want has been in the designing on and off since 2011 and has gone more revisions than I can remember, done 00 and P4 versions of it and the baseboards are the same for either so all ok on turnout locations and joins etc.Thinking of trialing those DGs and converting a few coaches to P4 first. That way I can hopefully conduct some more in depth trials to see what will work or not.


That seems a sensible approach. There are tales on here, and I have heard elsewhere of layouts built with tight curves that don't work and end up being scrapped. Building perhaps just a short section of the track with the curves, wire it up and then extensive testing of the locos and stock (passenger and freight) that it is planned to use, running in both directions and all possible combinations of train consists will reveal what will work. If double track is involved then of course the inner track has to be built first but don't forget the outer one as well.

If after all that it doesn't work then the only options are to try a different plan or find more space. The second is unlikely. For the vast majority of us, designing a layout is always going to be a compromise and that ideal grand project has to be scaled back. Better to accept that at an early stage then spend time and money on something that proves to be unworkable.

Terry Bendall

Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Fri Oct 26, 2018 8:05 pm

Thanks for all your collective feedback. Very much appreciated.

We'll continue working on the loft and then some tests can begin once boards built. You've given me many extra considerations and factors to muse over and for that I am greatful. :)

So far we got some more L brackets to put up, finish plugging the leak...or rather waiting for some heavy rain to test it. Put the sky boards back up after, sort the curtain rail for removable/customisable backscene sheets. After that it is installing the LED lighting followed by that silver moment when the baseboards can finally be built and extra testing can be conducted.
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Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Sat Oct 27, 2018 10:01 am

Been looking at the DGs and might by a set for coach tests.

However after scrutinizing them it seems they are basically the same as a Dingham with the main differences being mounting height and that buffing plate.

Based on this it seems if I were to use that dodge of adding a bar across the buffers (often seen with Sprat and Winkles) to avoid buffer locking the Dinghams and Screws may be compatible still on the tight curves.

I don't like the look of the bar but as long as it was a smooth plate it would only need to be on the coaches and it could also be made as a clip on to remove it.

The locomotives and trucks could keep their buffers to push but as they would be pushing a smooth plate there would be nowhere to lock. The bar would have to towards the top of the buffers to make room for the coupling though. Loop should still lift.

...in theory.

Any thouhts or previous experience on the idea?

I've tested my wagons on the excessive mystery curve and they don't lock so all good there.
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Armchair Modeller
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Re: Radius Testing - Practical Experiments.

Postby Armchair Modeller » Sat Oct 27, 2018 10:08 am

Dinghams and DGs are different. DGs have their own built-in buffing plates. You also normally have a loop on all couplers, whereas Dinghams have a loop one end of the stock and a hook the other.

To prevent buffer locking with DGs you adjust how far they come out from the end of the vehicle. There should be an optimum distance for eaach vehicle that prevents buffer lock.

Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Sat Oct 27, 2018 10:30 am

Ok many thanks.

Had another thought too, and this is based on my experiments so I know the concept works but whether it will work well enough in anger with long wheelbase stock with more pressure and weight I'm yet to find out.

With Dinghams and with the overscale but easier and more compatible Smiths screw links I have found the Dingham loops can push stock inside the 'hook space.' The loops themselves doing the pushing rather than the buffers. Failing that the lip on the running plate tends to hold things in place fine.

Like the above post where Dingham loops can be widened if they were lengthened also on just coaches and using a thicker beam, say 0.7 - 0.9mm wire to avoid bending under the strain this might work.

I think this will be the first proper test.

I got some coaches and coach wheels.

Not done a P4 coach before so providing that goes well (x2) I'll try this Dingham bodge and report back.
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David Thorpe
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Re: Radius Testing - Practical Experiments.

Postby David Thorpe » Sat Oct 27, 2018 12:15 pm

You might also consider the Keen Coupling System (http://www.keen-systems.com/Couplings.html) - not exactly finescale but might well do the job reasonably unobtrusively in a rake of coaches, for which indeed it is designed ("The system is intended for coupling fixed rakes of carriages buffer to buffer and still go round Hornby radius one curves"). But whatever you do, please don't resort to putting a bar across the buffers!

DT

Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Sat Oct 27, 2018 1:14 pm

Lol, I hate the bars too, I really do. Before I saw your post I was doing this....

Video Description....
Dingham Auto Couplers - I love them. You can use them with real 3-Link, Instanter & Screw couplings with the minimal of fettling, they provide delayed uncoupling and they use the buffers to propel stock thus giving a very realistic operation and look. Not too unobtrusive either. Plus if you bash the stock aggressively they won't couple so you can do some fly shunting!

Problem is, tight curves are a no no because the y will cause buffer locking.

After literally MANY months of thinking and a few experiments I finally found a dodge that works.

In this clip you will see a very rough and ready 'Super Loop' I made to modify a standard Dingham hook. it needs more refinement but a Black 5 (Henry) is going around a 2nd radius 00 curve with a Gresley teak no problem.

I only need a special at each end of a rake and Bob's your Auntie.


https://www.youtube.com/watch?v=o0zPtn6 ... e=youtu.be

Baby write up:

Daddio ages ago gave me a fishing pellet thingummy, so I chemically blackened Dingham parts and bunged them in. A real boon it is.
Image

Considering I'd need to solder them I got a fresh brass one from the etch.
Image

Following David Thorp's modification I purposely went overboard and extended the length and width.
It was a very quick nock up thus the rough uneven nature of it.
Image

Middle partly removed, needs more filing but good enough for the tests.
Image

The extended bar does the pushing on the inside of the coupling hook, that's the concept. Here is a super picture...
Image


So, current verdict.

1) - It works. Nuff said. Tests were mostly with Smiths Screw Link and Standard Dinghams.

2) - Shape needs to be a wee thinner and about 1mm longer, possible nominally triangularly shaped with the curved end.

3) - Brake pipes can get in the way, yet not on all stock. A little re-shaping of the pipes or hooks will easily get around this.

4) - These were tested on 2nd radius 00 curves and I only need a minimum of 34" if doing P4 not the extra silly 2nd radius. Ergo, it'll work better with more gentle curves.

5) - I'd only need one 'Super Loop' at each end of a rake of coaches. The rest of the layout stock can have standard Dinghams, 3-Link, Instanter & Screw fitted.

6) - Pig in poo. :thumb

7) - Awaits chastisement! :shock:
Would like your thoughts on this good or bad. Isn't a normal solution I know. Seems good so far.
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bobwallison
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Re: Radius Testing - Practical Experiments.

Postby bobwallison » Wed Oct 31, 2018 11:56 am

Knuckles,

The discussion above has focused on buffer locking and couplings, but I would urge you not to overlook the problem of clearance between bogie/pony wheels and fixed obstructions like cylinders, footsteps and (for pacifics) the rear frame extensions.

I have converted a Hornby Black 5 to EM gauge: amongst other mods it has Gibson wheels throughout and I have filled up the awful notch at the rear of the cylinder casings. The front bogie wheels now rub on the back of the scale cylinders when it negotiates my minimum 36" radius curves - it doesn't derail and the wheels continue to rotate, at least most of the time, but it is sufficient to rub the paint off the rims. P4 wheelsets are about 0.7mm wider over the rims than EM ones, so I would expect them to lock solid and probably derail when negotiating a 34" curve. There may be similar issues with the rear pony truck of a pacific loco, with the wheels rubbing against the inside face of the frame extensions.

Of course there are solutions to all of these: notches can be cut in the rear of cylinder cases (or not filled in); footsteps can be omitted; and the rear carrying wheels on a pacific could be made flangeless and hovering above the rails. None of these compromises would be required in OO with 34" curves but then of course the track and wheels wouldn't look as nice, so it comes down to which set of compromises one is more comfortable with. Each of us will have our own take on this conundrum and must answer it for ourselves, so you may have some soul searching ahead.

As for the absolute minimum radius, BR's official diagrams for their traditional 4-wheel wagons quote a minimum radius of 1 chain. 1 chain = 22 yards = 66 feet = a mere 264mm at 4mm to the foot. Way way back, Exactoscale (or it may have been Studiolith) had on their exhibition stand a 4 wheel loco with P4 wheels, running continuously around a circle of track which didn't look much bigger than a large dinner plate.

Regards,
Bob

Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Wed Oct 31, 2018 4:54 pm

Thanks, Bob.

Bogie swing etc indeed is an area I over looked initially so thanks for the reminder. I have read about P4 Black 5s and Pacifics going around sub 30" P4 curves which is why I revisited the option.

I can live with cylinder cut outs as indeed I have since day 1 but the other points you brought up may have to be addressed too no doubt.

If only space wasn't an issue. :-/ No way of increasing it so have to work with what have somehow.

Choosing gauge for this layout is killing me.
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David Thorpe
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Re: Radius Testing - Practical Experiments.

Postby David Thorpe » Wed Oct 31, 2018 5:30 pm

Knuckles wrote:Choosing gauge for this layout is killing me.


You could also consider 00FS (or is it 00SF?). If you really feel that P4 will limit your aspirations for this layout, that might be the answer.

DT


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