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Minimum Turning Circle for Model Trains
Brian asks readers:
“What is the minimum turning circle (OO gauge). I have just had a new shed built it is 3m X 4m unfortunately it door opens inwards. I want to put a layout with the door open but don’t know what the smallest turn that I would need. Any help would be grateful.”
5 Responses to Minimum Turning Circle for Model Trains
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I think what folks call OO gauge is the same or near HO if I am right. In HO scale a lot of basic track comes in an 18 inch radius, not sure what that is in metric without looking but in many cases that radius is a tight turning radius. for most better rail equipment you can purchase for your layout. I have only one radius curve that is a 22 inch radius and it works well with longer cars and engines that I have. This radius will generally allow your better equipment to make the turns. But to run with good success you need to shallow out the turns as much as you can. This helps with your running of your trains, better performance with long trains, helps with the excessive swing with long cars and engines and keeps your couplers more in line with your tracks. Most of my main lines are a 28 to 40 inch radius. I am pulling trains as long as 30 feet with great success. That is hard to do on tight 18 inch radius turns. The same applies to your switches. Tight turn switches that come with common beginner sets are to tight for lots of better equipment. Obviously good smaller engines and cars work well on tight turns but don’t make your tracks so if you buy better equipment that they cannot handle this track. To get these shallow turns I built By doing this you would be surprised how shallow your curves can be. You can build a gate that will open and close easily and be dependable with care as you build it. I have a video of mine titled as Counter weight on the Pass through gate. It took me 2 months to build but I go through it ten to twenty times a day and has worked flawless to date. from Newman
Thanks Newman for your input.
Brian
This is probably the most often asked question relating to model railways. Hornby and Bachmann make set track curved pieces in 3 radii, none of which are much good if you are building a scenic rural layout with “sweeping” curves but are ideal in urban scenes. The radius is predicated by three things – your layout (or room) size, the longest piece of equipment you are likely to run, and you own concept of “reality”. Always try for the largest that will fit, and try for transition curves.
A transition curve is not written about in many British or Continental publications, however it does two things. Firstly when your train approaches the curve it won’t suddenly jerk into it but will flow gently putting less stress on couplers and bogies. And the second advantage – it just looks better.
To lay out a transition curve on your layout, draw the line of the straight, or tangent, track beyond the start of the curve. Plot the centre of your curve so that it sits about 0.5″ away from the tangent and draw it in.. Now take a flexible rod or wood lath and fix it with nails along your tangent so that when bent it curves gently into the plotted curve, merging with the circumference of your previously drawn curve. What this does is produces a spiral from a larger radius into you fixed radius. Use flexible track in open areas.
Give it a go, but remember, the larger the radius the better, AND HAVE FUN
Brian, Good thought about the Transitions. I do it to mine but never think about it when explaining the curves. The trains flow into the curve and not jerk into them. Good thought from Newman
Most trains will get round 2nd radius curves, in fact most will get round 1st radius and more than half round 12″ radius, however they do need very accurate track laying and look horrible. 3rd radius is a good minimum though standard Set track points have a 1st radius curve through the point blades.
Personally 4th Radius and 2ft radius points are minimum for visible areas but I am using a 12″ radius curve on my next layout which only uses small tank engines and bogie cars though trains will not be reversing or shunting over it. If you drop below 4th radius hide it in a tunnel