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P4 Radius Tests - Practical Experiments



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 pullijg 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 calculagions, 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 t8ght 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 noticble.


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


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.


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....




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


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 HORRABLE! 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 sideplay these locomotives of the tests have. They were not measured but they range from basically 0 to 1mm.


Pics. Look at that horrid tight curve!!






I know full well tight curves are risky and not favoured 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!


Also please forgive the typo'sas I typed all of this out on a 'phone and editing is awkward and risky. Will clean it later on PC.


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