Curves

Discuss the prototype and how to model it.
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kelly
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Curves

Postby kelly » Wed May 03, 2017 6:39 pm

As some of you will be aware from the thread about the layout I'm working on atm, I've hit a bit of a planning snag.

I have 9ft in length, I can't really go much beyond this by much I expect due to being able to set it up at home. The current plan is for double track curving to create an L.

The plan for the station and sidings I'm for the most part happy about (as is my cohort Natalie after the laying of templates etc).

The problem, is the curve to form the L. The L is meant to have a traverser on the end of it, but using Templot, it is giving warnings (understandably) about how tight the curve needs to be to get to the board for connection onto the traverser. (the boards are 3ftx1ft6"+3ftx1ft6"+3ftx2ft currently).

Advice from those more experienced with P4 would be appreciated before I create a mess of too tight curves and regret it. However, the layout is an effort to learn these things to some extent.

Stock is mainly going to be bo-bo and EMUs, with some co-co and possibly some 6 coupled steam turning up (probably though more likely 4-4-0 or 0-4-4 etc).
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Noel
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Re: Curves

Postby Noel » Wed May 03, 2017 7:18 pm

There is insufficient data here for a proper response, really. However, on the basis of the figures you give, it appears that, on the assumption that the L is a right angle, that you are intending to turn the track through 90 deg on the 3ft x 2ft board :?: . If so, the outer track will be less than 2ft radius, for clearance reasons, and the inner track will be a smaller radius still. The clearance on such curves for bogie vehicles will mean wider track centres, with a consequent further reduction in the radius of the inner track. The other obvious problems are buffer separation between vehicles, even with sprung buffers, to allow stock to take such curves without derailing because of the geometry, and the conflict between bogies and outside cylinders on steam locos. It may be possible, but probably would not look very pretty. A dimensioned plan of the whole space available for the 'L' would be useful...
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kelly
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Re: Curves

Postby kelly » Wed May 03, 2017 7:42 pm

Noel wrote:There is insufficient data here for a proper response, really. However, on the basis of the figures you give, it appears that, on the assumption that the L is a right angle, that you are intending to turn the track through 90 deg on the 3ft x 2ft board :?: . If so, the outer track will be less than 2ft radius, for clearance reasons, and the inner track will be a smaller radius still. The clearance on such curves for bogie vehicles will mean wider track centres, with a consequent further reduction in the radius of the inner track. The other obvious problems are buffer separation between vehicles, even with sprung buffers, to allow stock to take such curves without derailing because of the geometry, and the conflict between bogies and outside cylinders on steam locos. It may be possible, but probably would not look very pretty. A dimensioned plan of the whole space available for the 'L' would be useful...


Yes, the original idea was 90degree turn to form an L on the 3ftx2ft board. I had thought about starting the curve before the start of the 3ftx2ft board.

This is intended to be a portable layout, so the dimensions can be changed if needed. I am just unsure if I could erect a layout over 9ft in my flat is the issue (probably possible). I could put the traverser on the end and have 9ft scenic + 4ft storage, but that wouldn't allow the storage to be erected in my flat really.

I don't really have a dimensioned plan as such other than what has been posted on the previous thread.
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grovenor-2685
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Re: Curves

Postby grovenor-2685 » Wed May 03, 2017 8:18 pm

For the stock you mention I would recommend a minimum radius of 1100 - 1200 mm to minimise problems, if you want to push it you could go down to about 920 mm. Either way your corner board needs to be five sided so you end up with a triangular fillet. The tracks don't have to cross the board joints at 90 degrees.
my corner board is 760 mm on each long side fitting to 305 mm wide boards and the double track curve is 1300 minimum radius crossing each board joint at approx 45 degrees. See attached sketch
Board 4.jpg

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kelly
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Re: Curves

Postby kelly » Wed May 03, 2017 8:49 pm

p4_trackplan.png
Rough plan.


I've played around with the plan in Templot a bit.

Not added are a set of points to allow running around (not sure if I could fit those in properly). The plan means an additional 3ft on the other side, which should be a problem as such. Rotating the plan has helped keep the curves within the 9ft length.

Does this look workable?

Attached is what I originally roughly drew up. It was revised when we looked at templates on boards, but no plan was drawn from that.
Attachments
post-11572-0-76813100-1488330988.png
Original sketched plan.
post-11572-0-76813100-1488330988.png (10.21 KiB) Viewed 688 times
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kelly
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Re: Curves

Postby kelly » Wed May 03, 2017 9:42 pm

After some discussion with Natalie, we might try to avoid the curves problem and having it with the traverser attaching at an angle, so only needing a gentle curve rather than going around 90 degree. It would mean a bespoke board, but that isn't a major issue in itself.
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