Radii

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SpudUk
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Radii

Post by SpudUk » Wed Oct 03, 2018 11:45 am

Me again (sorry).

What's the "ideal" radii for 16mm/32mm railways? I'm planning a curved bridge as my first build and I'm not sure what radii I should be aiming for, and if I can use set-track to make it slightly easier.

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Re: Radii

Post by tom_tom_go » Wed Oct 03, 2018 11:51 am

What locos and stock are you planning to run?

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Re: Radii

Post by SpudUk » Wed Oct 03, 2018 1:36 pm

tom_tom_go wrote: Wed Oct 03, 2018 11:51 am What locos and stock are you planning to run?
My passion is for the L&B but I very much doubt my garden is big enough to get a Manning Wardle around a curve in it! So I'm thinking W&LLR bogie stock might be the longest, with something like a Roundhouse Lady Anne?
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Re: Radii

Post by tom_tom_go » Wed Oct 03, 2018 1:53 pm

If you want to use set track go for the larger Peco R607 curves but I would strongly recommend you use flexi track and put in the biggest curve radius you can!

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Re: Radii

Post by SpudUk » Wed Oct 03, 2018 2:17 pm

tom_tom_go wrote: Wed Oct 03, 2018 1:53 pm If you want to use set track go for the larger Peco R607 curves but I would strongly recommend you use flexi track and put in the biggest curve radius you can!
What's the best way to guarantee a smooth and consistent curve? I'd use a rail bender in real life but I don't image there's a 16mm equivalent!
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Re: Radii

Post by tom_tom_go » Wed Oct 03, 2018 2:21 pm

You can make your own or buy one, GRS for example:

https://www.grsuk.com/Trackwork-Accessories-C306000

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Andrew
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Re: Radii

Post by Andrew » Wed Oct 03, 2018 2:30 pm

Arrgh, keep trying to send this but it won't go - I'll re-send if i can, but luckily Tom's said everything I've said anyway, only without the waffle! OK, I'll try again...

I agree that the old advice to go for as large a radius as you can still holds good - probably better than the really old advice which seemed to be that if your minimum radius has to drop below about 5' you might as well give up and retreat to the spare room with a box of Hornby OO set track...

I've found that whilst tight curves don't prevent smooth running, they don't help. The tightest on my current line is 3'6", which can slow trains down - not that there's anything wrong with slow running, of course, but I'd like it to be consistently slow (or slow-ish). There's the risk of "bow-string" effect too, long vehicles in the middle of a train being dragged over on sharp curves by the weight of the ones either side of it - it can be mitigated against, but I found it could happen with even short bogie vehicles on the 2'6" curves on my old line, and I still need to modify my WHR Summer Car to run properly on the current line. I'd have thought that could be a risk with W&L bogie stock on very tight curves, although chopper couplings of a consistent height should help...

I guess it really is a "courses for horses" thing - if I was modelling a freelance line in a small space I might be tempted by Peco's 38" curves (which match the points) but would keep all my rolling stock short-ish...

Another option for smooth curves is to invest in (or make) a rail-bender - I've got a GRS one which I've found to be fantastic...

Cheers,

Andrew.

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Re: Radii

Post by SpudUk » Wed Oct 03, 2018 2:35 pm

That's helpful, thanks guys! 3' radius did seem too small (although apparently the Accucraft Manning Wardle can take it!), so I'll get into the garden and see what the largest radius it could fit would be (and that the wife would allow)

Thanks guys!
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Re: Radii

Post by tom_tom_go » Wed Oct 03, 2018 2:42 pm

www.anyrail.com is your friend in planning (allows you to create custom radius curves).

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Re: Radii

Post by Andrew » Wed Oct 03, 2018 2:54 pm

SpudUk wrote: Wed Oct 03, 2018 2:35 pm I'll get into the garden and see what the largest radius it could fit would be (and that the wife would allow)
I'd recommend taking the line that larger radius curves can be more sinuous and natural looking and so blend better with the garden, whereas tight curves can look very artificial... Larger radius curves leave more room for planting too, because they've got bigger spaces behind them...

My wife now knows exactly what's going on when I cast my eye over a friend or neighbour's garden. "What radius curves are we having then?" she'll ask wearily...

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Re: Radii

Post by IrishPeter » Thu Oct 04, 2018 2:49 pm

"As big as tha can mek 'em" is the doctrine on radii. Occasionally there are constraints, such has hills and flower beds, but the general rule is to keep them as wide as you can. My indoor line is struck with some 3'6" radii but that is because of the space (or lack of it) in the basement. The outdoor line is being engineer to what will hopefully be a 5' minimum.

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Peter in Va
Traffic Pattern? What pattern? Spuds out; grain in, but cattle, sheep and passengers are a lot less predictable.

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Re: Radii

Post by SpudUk » Tue Jan 08, 2019 2:20 pm

So we've finally moved in. Just been out on the garden to measure (there is concern from her Ladyship on railway impact) to see if it's feasible or if I should just back up now and put some 009 in the loft. The garden is about 40ft long-ish and about 25ft wide, with a garage in one corner and a patio area. I can get 3' 6" radius curves in but I'm worried that'll be vetoed as taking up too much space
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Re: Radii

Post by tom_tom_go » Tue Jan 08, 2019 2:26 pm

Hi Chris,

Have a look at two of my recent videos that show the 2ft 6" loop I have in front of my garage:




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Re: Radii

Post by SpudUk » Tue Jan 08, 2019 2:37 pm

tom_tom_go wrote: Tue Jan 08, 2019 2:26 pm Hi Chris,

Have a look at two of my recent videos that show the 2ft 6" loop I have in front of my garage:



Does it cause you problems?

Also - oh my, that Russell has done something I thought only my wife could!
Chris Auckland

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Re: Radii

Post by tom_tom_go » Tue Jan 08, 2019 2:53 pm

Hi Chris,

It doesn't cause me problems but it limits you to what you can run although as you can see in the video Russell didn't have any issues.

I don't have the space or permission to put in a larger loop but if I could I certainly would so if you can do it!

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Re: Radii

Post by philipy » Tue Jan 08, 2019 3:14 pm

Chris, going back to your original query about a curved bridge, I'm not sure that is a good first project, it gives very little room for any error. However, the other point about using settrack curves, of whatever radius, is that you will get better running if you lead in with transition curves, and to do that you would need to use flexible track, so you may as well use it all the way through.
There was recently a fairly lengthy discussion about the need for a rail bender, with various views on the subject. It would be worth taking a look.
https://gardenrails.org/forum/viewtopic ... ail+bender
Philip

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Re: Radii

Post by IrishPeter » Tue Jan 08, 2019 3:33 pm

From Calthrop 'Light Railway Construction'

2' gauge minimum radius open country 150'
In sidings and in difficult country 60'

(So about 8' and 3'1.5" respectively in 16mm)

The 60 foot minimum radius comes from the Darjeeling Himalayan Railway, and their longest vehicles are a couple of 32' flat wagons. Where I tend to hit trouble with tight bends is with the coupling geometry. Accucraft Norwegian chopper coupling are relatively long, and can be a pain on tight bends when headstock mounted, so with tight bends I tend to go with some sort of buffer and chain, or bumper and chain arrangement so that the couplings have the maximum amount of yaw.

Peter in VA
Traffic Pattern? What pattern? Spuds out; grain in, but cattle, sheep and passengers are a lot less predictable.

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Re: Radii

Post by BorisSpencer » Tue Jan 08, 2019 3:57 pm

I still stand by the general rule of keep your radii as wide as you can manage.

But to put this into context, on my indoor test track I have a couple of sections of 14" radius curves, albeit by necessity rather than choice.
All my four wheel battery locos negotiate these sections successfully and so far I've tested my Mamod Brunel. I thought I may need to lengthen the coupling chains but all my 4-wheel stock copes well with no binding of the hook and chain centre buffers.
Take a look at the work of Jon Rogers (Pig Sty Hill) and Brian Dominic (google "Slugs Crossing") for inspiration.

This hopefully gives you plenty of scope for creating that shunting puzzle in an otherwise unusable corner.

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Re: Radii

Post by Andrew » Tue Jan 08, 2019 6:13 pm

I'm a flexible track and rail bender kind of chap myself, but a tip I've picked up from set track users is to create a similar effect to a transition curve by using a larger radius curve at each end of a tighter bend. Haven't tried it, but it makes sense...

You definitely need to get outside and play in the garden if you can - compromise in the great outdoors has got to be better than a sprawling empire in a dusty loft...

Good luck with it,

Andrew

PS Rather concerned about this dubious connection between my Russell and your wife!!!'

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Re: Radii

Post by SpudUk » Tue Jan 08, 2019 10:35 pm

Sorry Andrew, had forgotten that was your Russell!

I've done proper measurements of the garden so I'll try and do a scale drawing and see what I can make fit, then run it my the good lady for authorisation
Chris Auckland

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