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Advice on gradients please

verno

Joined: 1-01-70

Topics: 1

Replies: 1

Posted: Tue 21st May 2013, 2:22pm
Advice on gradients please

Completely new to this and know nothing, but i'm keen to develop my own track. I have 4.5 acres of garden but with quite a slope to 3/4 of it. Clearly depending on what I end up running, is there an accepted formula for gradients?
Verno
 

Replies To This Post

Peter Beevers

Joined: 9-10-01

Topics: 3

Replies: 134

Posted: Tue 21st May 2013, 4:29pm

Do you mean recommendations as to what you should use??? If so, it depends a lot on the curvature that will go with the gradient - curves and gradients are not good together. It also depends how big locos you intend to use, and how much you intend to haul. As a simple rule of thumb (and many will argue against it) anything greater than 1 in 100 will seem a fair gradient to your locos. Anything greater than 1 in 50 will seem steep. Anything more than 1 in 30 will be hard to use (or just downright dangerous) with adhesion only working. And any gradient will be MUCH worse when damp. Over 1 in 100, I would suggest an automatic brake fitted to the whole train (being a steam man I'd prefer vacuum but that new fangled air thing will work just as well).

As I said, this is a very subjective issue, so others will probably differ - and you need to sit back and make your own choices.
 

John

Joined: 23-09-06

Topics: 0

Replies: 5

Posted: Wed 22nd May 2013, 7:32am

Afraid I can't lay my hands on the quote at present , but I think it was Heywood who came up with the simple rule that on 1 in 50 a loco can pull four times it's own weight on dry rail , only twice it's own weight on 1 in 25 . As for automatic braking , this is a must . I run on a railway where the ruling gradient is 1 in 25 and we have had two runaways , luckily with no one on the carriages . It is frightening the speed that is quickly picked up and the force of the impact when the end of the line is reached . Needless to say we now have continuous braking and a trap point downstream of the top station!
 

verno

Joined: 1-01-70

Topics: 1

Replies: 1

Posted: Wed 22nd May 2013, 8:28am

Thanks for the replies. Automatic braking, and runaways, not considered that, as I said I know nothing, I need to start learning. Are there any guides available?
 

johnnicholson

Joined: 1-01-77

Topics: 12

Replies: 69

Posted: Thu 23rd May 2013, 11:45am

I believe the comment I am making is also covered in the Miniature Railway guidance booklet HSG216. It is important to ascertain that you can stop within ( and be able to demonstrate this in the case of an accident) a suitable distance and that the brakes are effective. This comes back to gradients and being able to stop a train on a gradient. I would always advocate line braking down a train be it mechanical, air or vacuum brakes. The important point is that the train lengths and braking capabilities of any particular train should be considered to give suitable braking on the gradient on a respective railway.

John
 

Narrowgauge7.25

Joined: 1-01-94

Topics: 16

Replies: 107

Posted: Thu 13th Jun 2013, 5:13pm

I would agree with John, I well remember taking my nearly new Romulus to Millerbeck and tried to stop in the station with a couple of carriages behind, only to find the loco wheels locked up but train sailing on. Now I have air brakes on the driving truck and train, much safer for tracks with gradients.
 

colinedmondson

Joined: 9-08-09

Topics: 3

Replies: 82

Posted: Fri 14th Jun 2013, 4:20pm

My thought is to try to stick to a max of 1 in 50 for pulling a few coaches, 1 in 35 for a single coach, unless you have brakes on a guards van as well or throughout the train. Keep the curves generous on the steepest bits, 40' radius is about the limit for most commercial lines, 25' for garden use, although Beconscott run commercially on very tight radius curves.
I too have had issues with wheels locking up and sliding past the station, and that was on a nearly level track with a touch of drizzle to lubricate the rust that had built up during the week. My loco weighs over quarter of a ton and had 3 coaches behind. It is now fitted with sand boxes dribbling directly onto the track.
I have managed to find a table of gradient against load, taken from a Baguley catalogue, which confirms what John has said above. This is for a 10 hp loco weighing 2 tons, and assuming that adhesion is the limiting factor rather than power available the ratios should be the same. (A sit in loco using the driver as extra ballast is a good idea, rather than adding him to the hauled load).
Level 31 tons, 1 in 100 16 tons, 1 in 75 13 tons, 1 in 50 9 tons, 1 in 40 8 tons, 1 in 30 7 tons, 1 in 20 4 tons.
Gives you an idea how the gradient will affect the train you can pull, although stopping is probably more important!
Good luck
 
 
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