Radius Testing - Practical Experiments.

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

Postby Knuckles » Wed Oct 31, 2018 6:20 pm

David Thorpe wrote:
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



Been considering 00-SF on and off for a long time but I have the view that if I am to put effort in track building then might as well go the whole hog and do it in P4 otherwise it feels to me like wasted effort.

It's exactly why I joined our society in the first place. :thumb

I have room for a P4 and 00 layout in the loft now most the L brackets are up for the higher teir and will be doing both gauges regardless. The major challenge for me is deciding which gauge for which layout.

It's a PITA I tell thee!


Note: I want the 00 layout to be able to operate the considerable stock amassed over the years while a select few are converted bit by bit and still be able to buy something off the shelf and enjoy it. Best of both worlds then.
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David Thorpe
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Re: Radius Testing - Practical Experiments.

Postby David Thorpe » Wed Oct 31, 2018 6:54 pm

So really you want a small but beautifully built P4 layout and a big fun to run 00 one?

DT

Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Wed Oct 31, 2018 7:15 pm

Deep down would rather it be the other way around, have the big one as P4 so it is the main one but tight curves and other things keep swaying me to do the easier and quicker 00 option but then every time I see anything P4, my own or other wise, I wanna do it in P4 and the cycle continues. It's been winding me up for several years and the actual plans for the layouts have been revised more times than I can remember because of the tight spaces.

It's like that game you have with 8 tiles in a 9 tile square, you shift one and it knocks the rest out so you shift another curing the problem and it knocks something else out and it's like that repeatedly with other factors also.

Eeys baad.
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Noel
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Re: Radius Testing - Practical Experiments.

Postby Noel » Wed Oct 31, 2018 8:39 pm

Knuckles wrote:It's like that game you have with 8 tiles in a 9 tile square, you shift one and it knocks the rest out so you shift another curing the problem and it knocks something else out and it's like that repeatedly with other factors also.


Not all tile puzzles are solvable...
Noel

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David Thorpe
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Re: Radius Testing - Practical Experiments.

Postby David Thorpe » Wed Oct 31, 2018 8:53 pm

I can't see the point of having a big P4 layout and a small 00 one unless the latter is built for exhibition purposes. Surely better to have a big 00 layout, on which you can use your existing stock and have fun running (and 00 with handbuilt track - or Peco bullhead - can be surprisingly good albeit not P4), and a small but beautiful P4 layout which you can take your time building and perhaps take to exhibitions with a fairly modest selection of converted stock. If you start by building a big P4 layout without assistance and want to have sufficient stock for it I fear it may take you an awfully long time (and cost you a lot of money).

DT

Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Wed Oct 31, 2018 10:33 pm

The big layout regardless of gauge is a 10-20 year projection and would cost a fair bit either way.

I can't do exhibitions as I can only attend Sundays and buggered if a manager wants to fill a slot for only one day. Besides which I helped exhibit a layout on a Sunday once and it bored the crap out of me. All I truly wanted to do was go look at the other layouts.

Regarding why I'd want a big P4 layout.

Well, lets just say I have a very specific vision and goal I want to fulfill and I'm doubting 00, even a more finescale 00 is going to cut it. Not going to expound upon it here though.

I'll decide eventually all being well. If I do it in P4 then the track doesn't have to take too long based on my tester layout. A day or three for a stardard turnout etc.
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Barry Davis
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Re: Radius Testing - Practical Experiments.

Postby Barry Davis » Thu Nov 01, 2018 4:27 am

Noel wrote: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.

Hi Knuckles, I have been following this subject with interest.

I have built a hidden line with a reverse curve in the shape of a figure "S " in an available space of only 10 foot wide, which by my calculations, are two curves with a radius of only 30 inches each.

I used the P4 gauge track tool for gauge widening and applied super elevation to each curve. The line was only designed to turn my EMU stock, it will also turn diesels, bogie coaching stock and 4-wheel goods wagons. As Noel states there can be a problem with wheel-sets fouling the inside of solebars of bogie coaching stock. But no matter how much side play my steam engines have, I can not run any 6 -coupled locomotive round theses curves so I have to revert to hand shunting to turn my steam locomotives.

Hope this helps

Regards Barry

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Noel
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Re: Radius Testing - Practical Experiments.

Postby Noel » Thu Nov 01, 2018 11:33 am

Have you tried lwb 4-wheel stock such as Tubes or ex-LNER CCTs and SR design CCTs/PMVs on those curves, and, if so, with what outcome, please?
Noel

allanferguson
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Re: Radius Testing - Practical Experiments.

Postby allanferguson » Thu Nov 01, 2018 10:22 pm

I have a fairly large setup in my loft, which is about 40ft long but only about 8ft (effectively) wide. My tightest radius is 40 1/2 inches round the ends, and I found that 6 wheel locos could not reliably go round. However I relaid the curves using Exactoscale Gauge Widened trackbases, which give, as I recall, about 0.8mm gauge widening. Everything now runs round the curves with no problems. Things still fall off, but that's down to my bad tracklaying!.


Allan F

Philip Hall
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Re: Radius Testing - Practical Experiments.

Postby Philip Hall » Fri Nov 02, 2018 12:13 am

I have been using the Fast Track bases and the gauge widening is said to be 0.2 mm, therefore 19.03 mm. I think 0.8mm is possibly not right; Steve Hall used 0.5 mm widening and recounted no end of problems. My bases measure 19.10 mm, so
0.27 mm widening and this seems to work well.

Philip

allanferguson
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Re: Radius Testing - Practical Experiments.

Postby allanferguson » Fri Nov 02, 2018 1:24 am

Philip you are probably right -- I can't get up into the loft just now to measure it. But I think that, within reason, track gauge can be wider than standard on plain track with no harm done. But not through points and crossings. The only difficulty is trying to couple SWB wagons (and indeed pushing them)

Allan F

Barry Davis
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Re: Radius Testing - Practical Experiments.

Postby Barry Davis » Fri Nov 02, 2018 8:30 am

Noel wrote:Have you tried lwb 4-wheel stock such as Tubes or ex-LNER CCTs and SR design CCTs/PMVs on those curves, and, if so, with what outcome, please?

Hello Noel,

As they say a photo says a thousand words, so today following your suggestion I took photos of a short parcels train travelling round my small radius reversing curves. The train was pulled by a Heljan Type 3 Crompton Diesel Locomotive pulling the following vans, Hornby Doublo SR CCT van, Lima LMS 42' GUV, Mainline LMS 50' BG, Lima LMS 42' GUV, Lima BR CCT van, and a Lima BR Bogie GUV.

As a point of interest I checked the amount of gauge widening that the P4 track gauge applied to these curves. The track gauge has widened the track gauge on the curves to between 19.08 mm and 19.1 mm.

Most of the rolling stock including the locomotive have working sprung buffers which as you can see from one of the photos are not fully compressed.

So yes Noel, lwb 4 -wheel stock seem to go round 31 to 31 inch curves OK, but I did file away some of the inside of the solebars on the bogie stock.

Regards
Barry
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Noel
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Re: Radius Testing - Practical Experiments.

Postby Noel » Fri Nov 02, 2018 4:22 pm

Thanks for that, Barry, most useful.
Noel

Julian Roberts
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Re: Radius Testing - Practical Experiments.

Postby Julian Roberts » Sat Nov 03, 2018 8:57 am

Knuckles, I'm not sure this adds anythng of value to what's been said already! I think you have seen this previously, but just in case you didn't




This is a 2ft radius curve with reverse and no transition. AJ couplings. The buffers don't lock when reversing, to my surprise, but longer locos and coaches probably would.

The loco is an 0-6-0 Barclay Tank, suspension as per my Snooze 199 article

I wrote all this up on May 6 2017, towards the bottom of this page, under the heading 600mm/2ft curve:

viewtopic.php?f=5&t=4732&start=300

To get bigger locos etc round sharp curves you may have to compromise on realism as has been said (front steps, cylinder draincocks, etc etc)

Good luck!
Last edited by Julian Roberts on Sat Nov 03, 2018 5:38 pm, edited 2 times in total.

Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Sat Nov 03, 2018 9:15 am

Many thanks and also to everyone who has posted so far, it helps.

I'm still a wee stuck on it all but thinking so far providing I don't do a piggy ear hole job things will be fine. Won't know fully until the loft is more finalized but then some more in depth tests can be conducted.
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Julian Roberts
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Re: Radius Testing - Practical Experiments.

Postby Julian Roberts » Mon Nov 05, 2018 9:46 am

Hi Knuckles I realised I could try a couple of things for you on my 2ft radius test track. First here is a video of a Class 782 loco on it. I designed it for a 4ft radius but clearly I overestimated the amount of sideplay needed! - outside brake pull rods add to the challenge. The 782 has a much longer wheelbase than the Barclay tank in the previous video. So I suggest it should quite possible (though not necessarily easy) to design mainline locos to go round your bends, given thought and compromise.


Next I tried two of my coaches, 57 footers. There are bogie problems (all my stock is designed for 4ft radius minimum) but the point was to see how the buffers behave. These are sprung. The AJ couplings are mounted on the bogies, not the vehicle itself, but using the Society jigs that give the correct mounting position relative to the buffers. The buffers are slightly compressed at this radius.

20181104_081551.jpg
2 coaches


On the reverse curve this will not work at all when propelling.

20181104_081006.jpg
Coach and CCT van on reverse


Then here is the as yet unfinished Crab. The buffer alignment is similar to a coach.
20181104_095753.jpg
Crab and coach

Longer locos have oval buffers of course so may still be OK.

And a couple of shots showing the pony wheel. I think a front step when attached would not be affected, but the draincock pipes would have to be angled outwards a bit.

20181104_081350.jpg
Pony wheel

20181104_081403.jpg
Pony wheel.


So my general point is that you should be OK if you avoid a reverse curve for propelling trains, and AJs work well (well that's just my preference!)

The Crab seems to have enough sideplay too so later I'll see if it can run without derailing...!

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Andy W
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Re: Radius Testing - Practical Experiments.

Postby Andy W » Mon Nov 05, 2018 11:27 am

When I started working in this gauge someone gave me two pieces of advice. Spring your buffers and avoid reverse curves. I know Julian's example is a test track and invaluable as such, but the real railway avoided them whenever possible.
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Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Mon Nov 05, 2018 11:38 am

Many thanks for those extras (addressing last two posters).

I wouldn't need to go as tiight as 2' so that is looking very promising indeed.
There is only one reverse curve on the plan that isn't a standard crossover but not that tight.

I love your Crab by the way. On a different earlier video seeing the valve gear at the top above the slide bars moving is most impressive. Usually that area on models is static.
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Re: Radius Testing - Practical Experiments.

Postby Julian Roberts » Tue Nov 06, 2018 1:05 pm

Thanks Knuckles! The moving bit you refer to is the radius rod. The amount of movement it makes varies on the real thing, basically according to speed and how hard the loco is having to work. Only at the slowest speeds is it likely to be in "full gear" as I have made it, but my locos have a max speed of 30mph. At normal running speed it is likely to be so near "midgear" that movement is almost indiscernible, so the typical RTR set up is just as realistic.

Going back on message, don't take this the wrong way, I don't fully know what your plans are, but it has always seemed to me it's a bit daft* modelling in P4 for its realism yet making trains whizz round unrealistic curves, relative to the stock and speed. But there's "onstage" and "offstage", and what we do offstage is entirely our own affair, with no limit on lateral thinking. If I wanted to turn a circle in the minimum space "offstage" I would resort to anything that was practical. Checkrails could be very useful, fairly easy if making the track. They could be all the more more effective if slightly high, say using Code 100 where running rails are 75. Something I had speculated doing was, instead of running on rails, trains would run on pcb, on their flanges, with rails soldered on inside the gauge area acting simply as checkrails. The limitation would be inside gubbins like cosmetic springs or actual pickups, so the "rails" might have to be Code 40 or even less. There could even be outside checkrails too, though maybe they have a different name where they (rarely) occur on some bridges.

These are just ideas, I'm sure you could have lots more. I haven't tried any of this, except I did solder checkrails on my kids layout RTR turning circle at the rail joints which was fully effective.

Yeah my 2ft curve test track is just my ideas test bed, taking things to extremes, proving P4 works! 3ft should be much easier but it's still a lot of work to make a mainline steam loco reliably take model train curves. On my Crab thread I showed all the places of the running gear that foul even on a 4ft curve, there will be that much more filing and fiddling the smaller the radius. As usual I suggest reliable running is impractical without some sort of effective suspension, but I also claim that where the suspension is effective there can be much slacker standards of track laying, no fooling about looking for half millimetre inaccuracies of rail level!

* by which I mean counterproductive. I fully admit to being daft...daft about trains, model railways, Pythagorean tuning, global warming, Brexit ... ....etc etc!

Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Thu Nov 08, 2018 12:54 pm

Thanks Knuckles! The moving bit you refer to is the radius rod.


No problem, and cool. I have learned the names of the various rods before but keep forgetting. So many of the bloomin' things. It does look very convincing in motion, something I'd like to see modelled more. Whether I'll be a one to do it is unknown. Currently not thinking so as it looks a bit of a pig to get to work well.


Going back on message, don't take this the wrong way, I don't fully know what your plans are, but it has always seemed to me it's a bit daft* modelling in P4 for its realism yet making trains whizz round unrealistic curves, relative to the stock and speed. But there's "onstage" and "offstage", and what we do offstage is entirely our own affair, with no limit on lateral thinking. If I wanted to turn a circle in the minimum space "offstage" I would resort to anything that was practical.



Awful space restrictions make it the only way. It's either do tight curves or don't do anything.
Tight curves or not, P4 track and wheels is still miles more realistic and convincing than 00 to me.

On my Crab thread I showed all the places of the running gear that foul even on a 4ft curve, there will be that much more filing and fiddling the smaller the radius.


Hmm, see this sort of thing is what worries me, on the converse side of things; part of why I reconsidered this particular plan to be in P4 is because I read several of your posts and those of other people elsewhere saying you can get Black 5's around a 30' radius or whatever, and another guy got a 9F around a 2' 6" curve. Reading those posts gave me some more hope yet what you just said about the 4' radius still being not enough then dashes that.

So what is it!?

Ok I know there are many variables. My current plan if I go P4 for this one is to construct the loco's I need, some are already done and I have proved to mysself they go around a much tighter curve than I need, the majority of other loco's are 0-6-0's so no problem there. My gripe is the 4-6-0 & 4-6-2 I'd need to somehow build later to traverse those 34" radius curves.

Is it possible.....and I know pitch forks may be aimed my way for saying so, but is it possible to just pull the whole cylinder assembly out by 0.5mms either side or something? Ok so I know that is possible as you just snip the link between the cylinders and mount them outwards, but practically speaking, as long as platform clearances are adhered to would it be viable to do whilst avoiding binding? My biggest worry is doing everything then when it finally comes to tackling those bigger engines finding out it is impossible....even though I have read from you and others before it is possible.

I suppose if I personally found it impossible I could dig deep and find someone who would be willing to build them for me, really don't want to even have to consider that though.

Also a baby question tagged on, some of these 34" curves will require curved points and a diamond. This may be asking for pain I guess. Viable? Gauge widened by 0.2mm with a wide check gap thus still gauged from the crossing, would it work?

Hoooo :?
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Julian Roberts
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Re: Radius Testing - Practical Experiments.

Postby Julian Roberts » Sat Nov 10, 2018 4:32 am

Sorry for delay Knuckles. Exhibition in Newcastle today.

And for perhaps being confusing. When I have a moment I'll test more of my locos round my 2ft curve. I reckon that as my 782 goes round it they all might...but my tender locos will be too close coupled to manage with the tender.

Even for a 4ft curve we have to make compromises - that's very sharp in prototypical terms. Wiki says what the 9F minimum radius is, I think it was 5 chains, and that was supposed to be a very flexible loco for its size. For a start, on any loco, the frames will probably have to be made with EM spacers. I always work out for myself the sideplay required and hence maximum frame width ever since after using the P4 spacers my first loco the 439 0-4-4T wouldn't go round my 4ft curve.

But as the 782 shows, by being pessimistic and ultra cautious I have succeeded there in making it take a far more challenging curve than I designed for. Possibly the gauge widening is what makes it work at this radius. So perhaps it'll be the same with the Crab.

ThE Crab is the biggest loco I've done so far and I'll finish that next year when I've got some modelling time again.

I suggest it's my heretical ideas on suspension (Snooze 199) that make my locos stick to the track in this challenging situation.

If you don't mind the compromises built into a Bachmann or Hornby Pacific designed for 3rd radius curves, the same compromises in P4 will get you round a 34" curve I'd have thought...?

Similarly the curved points and crossover sound like fun. I think you'll be really pushing the envelope, and isn't a curved diamond supposed to be an ultimate challenge?!

Rarely in London, I was amazed going through Borough Market Junction the other day to see what sharp curves there are in that vicinity. Especially a Waterloo to Cannon Street lines connection. Checkrails everywhere. Once steam locos were grinding round those curves. But I don't think these curves were as sharp as your 34"!

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steamraiser
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Re: Radius Testing - Practical Experiments.

Postby steamraiser » Sat Nov 10, 2018 10:46 am

Having skimmed the posts have you considered KDs?

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Knuckles
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Re: Radius Testing - Practical Experiments.

Postby Knuckles » Sat Nov 10, 2018 12:00 pm

Yep, and the verdict is a solid no.

I'm not sure what looos worse, those or tension locks. :?

I figured out my coupling conundrum with a gool ol' bodge job (vid on an earlier page). It's just the curve issues with big locomotives that are currently taxing me. I'll reply to Julian once I get on the PC.
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Armchair Modeller
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Re: Radius Testing - Practical Experiments.

Postby Armchair Modeller » Sat Nov 10, 2018 12:06 pm

I remember an article in MRJ some time ago where Jas Milham had an S gauge layout with very tight radius curves. He got around the problem of a loco with a very long wheelbase (J17?) by articulating the chassis i.e. so that part of the frames pivoted. Unfortunately, I have no idea which edition it was.

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Noel
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Re: Radius Testing - Practical Experiments.

Postby Noel » Sat Nov 10, 2018 12:36 pm

Armchair Modeller wrote:I remember an article in MRJ some time ago where Jas Milham had an S gauge layout with very tight radius curves. He got around the problem of a loco with a very long wheelbase (J17?) by articulating the chassis i.e. so that part of the frames pivoted. Unfortunately, I have no idea which edition it was


It is MRJ 100 from 1998, and yes it is a J17.
Noel


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