Forum Options

« Back to Engines and Rolling Stock Topics

Sign In above to begin adding replies.
 

How to calculate a minimum radius from the wheelbase of stock.

workwright

Joined: 10-12-17

Topics: 4

Replies: 6

Posted: Sun 6th May 2018, 11:25pm
How to calculate a minimum radius from the wheelbase of stock.

Hi, I am sure there must be a formula for linking the possible minimum radius of track to the wheelbase of the locos and stock. If there is, will somebody enlighten me? Thanks, Malcolm.
 

Replies To This Post

Xz

Joined: 1-01-92

Topics: 26

Replies: 328

Posted: Mon 7th May 2018, 10:02am

Hmm. I'm not sure what you wish is out there, but then I'm no mathematician, perhaps someone better versed may be able to help. There are a lot of variables such as gauge widening to consider.
Certainly radius can be derived for a curve, using two points(wheel centres?), and the offset to the rail, but that is an existing radius. Angle of attack of the flanges must play a part, so therefore so must flange depth/shape/wear. Driven wheels, trailed or pushed, may well also behave differently.

Trial and error is the most usual way, and usually they do a lot better than thought. Romulus at 16" wheel centres is claimed to negotiate a 10 ft Rad. I have to admit to not having tried it.
 

MartynRedfearn

Joined: 1-01-94

Topics: 24

Replies: 172

Posted: Mon 7th May 2018, 3:39pm

The formula is on SMEX website and all you have to do is input values. http://www.smex.net.au/reference/MinRadius02.php
 

workwright

Joined: 10-12-17

Topics: 4

Replies: 6

Posted: Mon 7th May 2018, 6:57pm

Thank you both. The loco is a Lilla with axle centres of 16". I I put the details into the Australian formula and it comes out at just over 12.2 feet. So I will call that 12 feet 6 inches- this can be the unused absolute minimum and I will use 15 feet for turnouts. I am going to use 30 x 12mm bar for the rail. Luckly I have been given the loan of a motorised rail bender. Thank again.
 

Xz

Joined: 1-01-92

Topics: 26

Replies: 328

Posted: Mon 7th May 2018, 8:44pm

I don't see wheel diameter in that formula. Smaller wheels definately have an easier time on tight curves. I'd say your 12ft 6" is pretty close on a 16" centre.
 

HauteSaoneFrance

Joined: 2-01-14

Topics: 35

Replies: 141

Posted: Mon 7th May 2018, 10:31pm

I'm doing some rolling stock with a 2 ft 6 in wheelbase for my standard 30ft radius with 3 mm gauge widening mostly on Cromar White 27 mm medium steel rail, the formula is WB X 12 = minimum radius, Hope it works? 16 in WB on that formula would work out at over 15 ft radius
 

Railrose

Joined: 25-06-07

Topics: 4

Replies: 52

Posted: Tue 8th May 2018, 6:38pm

This is the basis of my portable track system, 15x15 box steel profile, 6 feet radius, 1 meter length

I did some trial and error, and went down to ridiculously tight radiusus.
After trying about 4 1/2 meters (= about 15 ft) some 30 years ago, I went down to 6 feet radius on my portable track system, including switches. I use a 2mm gauge widening, on all the portable track panels, curved as well as straight. So a standard 30 degree switch is only one meter long and weighs 10 kg. This is in regular use since the first trials in 2001. Most of my rolling stock has a 44 cm, about 17 inch wheelbase with 4 inch wheel diameter, standard society geometry. My petrol mechanic has 50 cm, 20 inch wheelbase and 5 inch diameter wheels.

However, a little bit of grease is necessary, especially when the rails are a bit rusty or dry after rain.
On the Maasoever club track our 7 metres (21 feet) radius loop also requires regular greasing. How often depends on weather conditions and traffic intensity.

My own stock negotiates the 3 feet radius at home, with nearly 1/4 inch widening, so radius is twice the wheelbase, I once took a friend as passenger on a wagon with 2 feet wheelbase through, surprisingly no problem. 5 inch wheel diameter..
This is the basis of my portable track system, 15x15 box steel profile, 6 feet radius, 1 meter length

I did some trial and error, and went down to ridiculously tight radiusus.
After trying about 4 1/2 meters (= about 15 ft) some 30 years ago, I went down to 6 feet radius on my portable track system, including switches. I use a 2mm gauge widening, on all the portable track panels, curved as well as straight. So a standard 30 degree switch is only one meter long and weighs 10 kg. This is in regular use since the first trials in 2001. Most of my rolling stock has a 44 cm, about 17 inch wheelbase with 4 inch wheel diameter, standard society geometry. My petrol mechanic has 50 cm, 20 inch wheelbase and 5 inch diameter wheels.

However, a little bit of grease is necessary, especially when the rails are a bit rusty or dry after rain.
On the Maasoever club track our 7 metres (21 feet) radius loop also requires regular greasing. How often depends on weather conditions and traffic intensity.

My own stock negotiates the 3 feet radius at home, with nearly 1/4 inch widening, so radius is twice the wheelbase, I once took a friend as passenger on a wagon with 2 feet wheelbase through, surprisingly no problem. 5 inch wheel diameter..
 

Railrose

Joined: 25-06-07

Topics: 4

Replies: 52

Posted: Tue 8th May 2018, 7:31pm

This is the first switch I made, 20x20 mm box profile, approx 15 ft radius
This is the first switch I made, 20x20 mm box profile, approx 15 ft radius
 

Railrose

Joined: 25-06-07

Topics: 4

Replies: 52

Posted: Tue 8th May 2018, 7:35pm

With smaller and lighter switches, from 15x15 mm box steel interesting layouts can be made without having to hire a HGV
With smaller and lighter switches, from 15x15 mm box steel interesting layouts can be made without having to hire a HGV
 

workwright

Joined: 10-12-17

Topics: 4

Replies: 6

Posted: Tue 8th May 2018, 9:18pm

Thanks again for more inspiration. Railrose I like your approach. Your sissors crossover reminds me of a lovely photo of a 2 foot system on a dock in South America that was used in an old Decauville catalogue. I am just about to order the first 120m of bar stock for the rail. I will report progress on the infrastructure topic. Thank you all for your help and inspiration. Regards.
 
 
« Back to Engines and Rolling Stock Topics

Web design by Slingshot