Track laying

[Mike BrettParticipant @mikebrett89695]

Curve radius

[Mike BrettParticipant @mikebrett89695]

Hi

I am trying to work out the minimum radius curve I can comfortable get away with when laying 3 1/2 gauge track . My engine is a Rob Roy 0-6-0 with flanges on all the wheels. Track would probable be aluminium. Space is limited so very important.

Cheers Mike

[vintagengineerParticipant @vintagengineer]

What about if you bank the track slightly?

[richardandtracyParticipant @richardandtracy]

What immediately springs to mind from vintageengineer's comment is an extreme wall-of-death experience on a Rob Roy going round a 10ft radius at 15mph. Mind boggles.

However cannot contribute anything useful.

Regards,

Richard.

[BazyleParticipant @bazyle]

It rather depends on the tread width and amount you can widen the track gauge too. Full size narrow gauge locos have extra wide tread to help with this. Some people manage to get a 5in loop into the width of a standard semi-detached plot , 15ft radius so you could scale down but really if the loco is already built it is going to be worth some practical experiments to ensure it is both stable and not causing extra rail and flange wear. Also look carefully at the effect of gauge widening on other stock on the line.

[Paul KempParticipant @paulkemp46892]

Minimum radius for a short wheel base 040 5" gauge is 10' with minimal gauge widening. An 060 however won't go round that, needs closer to 30'. Not tried with a 3 1/2" gauge loco but 20' would probably be the minimum ideal, you might get down to 15' if you widen the gauge by 1/16" or so. Best to use aluminium rail for tight curves then the rail is more likely to wear than the wheel flanges on the loco! Also remember you will need to be loose coupled or on a reasonably long bar to prevent buffer locking. As already said don't forget anything you will be pulling behind, again for tight curves 4 wheel, short wheel base bogies under any stock will be best.

Paul.

[duncan webster 1Participant @duncanwebster1]

Before our rebuild, our track had 27ft radius curves on 5"g and we managed some pretty big locos, Duchess, Britannia etc. Gauge widening of a couple of mm helped a lot. You can scale this for 3.5"g, and Rob Roy is fairly short wheelbase even if it is 6 wheels.

[Mike BrettParticipant @mikebrett89695]

Thanks for the replies. At least I have an idea now where to start.

Mike

[Dennis RaynerParticipant @dennisrayner52782]

I think people worry too much about this. My 5" gauge bog-standard 0-6-0 Boxhill is perfectly happy on 12½' radius curves in my back garden. Video on Youtube shows it happening.

[julian atkinsParticipant @julianatkins58923]

Here is Dennis's youtube clip of his lovely 5"g terrier in his garden at the back of Portsmouth

**LINK**

I would guess Dennis added a 1/16" onto the gauge on the curves. This isnt a problem, and is standard on club track curves in 3.5"g and 5"g.

Cheers,

Julian

[OldMetallerParticipant @oldmetaller]

Julian, I'm guessing Dennis is using about 15' radius there, could you confirm that please? I'm quite excited by that clip, as it looks about the same size garden as mine and I'd written off the idea of a 5" gauge line years ago.

Regards,

John.

[Dennis RaynerParticipant @dennisrayner52782]

John, I used PNP plastic sleepered dual gauge track (5" & 7¼&quot with gauge widening on the curves of 1/16" as Julian said. The curves are 12½' radius in a garden which is 30' wide. Overall the garden is about 120' long. The track circuit is just over 200'. I run my 5" Terrier and all my 7¼" stock has a maximum fixed wheelbase of 12".

[OldMetallerParticipant @oldmetaller]

That's great Dennis, thanks very much! I'll go up in the garden later and have a think about it!

I've got about 60' x 40', only problem is the gentle slope up away from the house…although that could mean some interesting civil engineering!

Regards,

John.

[Dennis RaynerParticipant @dennisrayner52782]

John, In my Youtube video you can see my Terrier pulling me up a 1 in 26 slope. My Terrier has a lot of additional weight since most locos have their haulage ability limited by wheel slip rather than lackl of tractive effort. I achieved this by filling the side tanks with lead and carrying my water supply in the driving trolley. which has the bonus that it is good for the injector.

My garden is about 20" higher at the far end so having climbed the slope it was downhill all the way back to the beginning so I had ti have the blower on all the time to maintain the fire. As a result I now run in the opposite direction – that means that the loco is working all the way round until it comes to the top of the slope which is about 25' long.

If you have a gradient to negotiate I recommend you try to add as much weight to the loco as possible.

Regards, Dennis

[OldMetallerParticipant @oldmetaller]

Thanks Dennis, food for thought there…

I have a friend who is a surveyor/soil mechanic, he's offered to bring round his laser-powered theodolite or something- he clearly thinks it's normal, I don't understand it, but it will be interesting to find out what slope my garden has and what I could do about it.

I take your point about adhesion, I have the same problem at work with a 3,300 hp loco that only weighs 128 tonnes!

Thanks again for all your help.

Regards,

John.

[Bob YouldonParticipant @bobyouldon45599]

Good morning Mike,

As you are aware the Rob Roy design is based on the Caley dockyard shunter; in full size they were designed to negotiate tight radius curves down to as little as 1½ chains in the restricted dock areas and yards, if you use that figure the radius for 3½″ gauge comes down to just over 6’ radius! I would think if you used a radius somewhere in the region of say 10’ you wouldn’t have a problem particularly if you gave it a touch of gauge widening.

The locomotives weren’t nicknamed Beetle crushers for nothing.

Regards,

Bob

[Neil WyattModerator @neilwyatt]

Posted by Bob Youldon on 27/02/2017 10:01:00:

Good morning Mike,

As you are aware the Rob Roy design is based on the Caley dockyard shunter; in full size they were designed to negotiate tight radius curves down to as little as 1½ chains in the restricted dock areas and yards, if you use that figure the radius for 3½″ gauge comes down to just over 6’ radius! I would think if you used a radius somewhere in the region of say 10’ you wouldn’t have a problem particularly if you gave it a touch of gauge widening.

Wouldn't that be the 0-4-0 shunters?

Edit I found these is this what you mean?

You could turn off the flanges on a Rob Roy's centre wheels. Not a sin with a freelance design

Neil

Edited By Neil Wyatt on 27/02/2017 11:02:50

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