Leicester North

You do come across some SOAP in our hobby; there's one in my club; usually best ignored, but ...plastic curtain rail the only way....computer aided design a waste of time... OMG. Joking apart, like many others, I've been there, done it and moved on. Obviously there's a place for free-form curves in model railway track design, but as in the real world, I think there should also be some attempt at engineering. After all, aren't we trying to model the protoype? This may involve a bit of maths etc, not everyone's cup of tea, but still worthy of serious consideration. For those that want to take up the challenge see my earlier posts. That's all folks, Cheers Brian

From the www I've read that prototype mainline transitional curves are of the order of 80metres which scales to approx 1metre on the oo layout! Also a line speed of 50mph requires a minimum curve radius of approx 350metres which scales to 4.6 metres in oo. Although these dimensions are unlikely to appear on a layout they produce a ratio L/R of 0.23 which may be a useful guide. I have also seen a ratio of 0.6 recommended but no reason given (see www.youtube.com/watch?v=Nu9qlIckU7Q.) I personally have been satisfied with the 22.5 degree case using setrack. As for the diagram which I created in Word, my apologies, I should have added that it is not to scale and is only indicative of the geometry. Points A & B are intended to be tangential. The offset t is a function of theta and is an ouput of the equations not an input: as theta increases so do q and t. I believe the program AnyRail has an "easement curve" option which can be printed out as a template, but I haven't used it. I totally agree "if it looks right it probably is right" all I've done is attempted to get there quicker more consistently. In the end I'm just sharing what works for me. Cheers Brian

I have been out of action for a few weeks for various reasons, but now back with the data sheet I thought I'd attached last time. Originally intended for my own use, I've now added some explanatory notes in the event it may be of use to other modellers. q t DataSheet.pdf

At the risk of appearing obsessed with transition curves (I do think they add a lot to a model railway's looks and operation), I have extracted some Euler offset data from the spreadsheet I posted last month and put it into the attached pdf file. I know that modellers using track design software (where easement curve templates can be easily generated) will probably have already incorperated same into their layout design. This data sheet I hope would be of interest to those who, like me, still design a layout with pencil and ruler!

I've updated my transition curve spreadsheet to be more user-friendly and more robust. It now includes some suggested starting values and the sheet has been protected to prevent accidental changes to the calculations. The calculated values are theoretically correct for the Euler Spiral as used prototypically. However, using approximations when marking out on the baseboard is ok since I reckon some easement is better than none. Similarly for double track I would mark out the centreline between the tracks rather than each individual track. I hope this is of some use for those starting a new layout or modifying an existing one. Transition Curve Calculation v2.xls

I've updated my transition curve spreadsheet to be more user-friendly! I've posted it in the Layout and Track Design section where I think it belongs.

I'm a new member of RMweb and I recently posted a blog with a spreadsheet attached which I have used for setting out transition curves. I now realise that the best place for it is in this Layout & Track Design spot so I've attached same to this topic. If any member finds it of interest feel free to download and use. Brian Watkinson Transition Curve Calculation (1).xls

I am a great fan of transition curves in model layouts, particularly for mainline track. I think it improves the realism no-end. Seeing a train at speed easing into a section of curved track is very satisfying. My own first efforts were very hit-and-miss, applying offsets by eye. But after a bit of research on the web I've come up with a spreadsheet to calculate theoretically correct offsets for a transition curve for any given curcular curve. I am happy to share this with any member who is interested. Transition Curve Calculation.xls