Help/advice with gradients

[Dan6470]

Hello and Happy New Year

 

I have some concerns with regard to gradients. I'm trying to plan a layout in 00 that requires changes in levels, in the region of approx 4ins. I have recently obtain a book by C.J. Freezer "The Model Railway Design Manual" but have become a little confused with the description about gradients, well actually the confusion is with the table. Does anybody have this book and is able to explain the table to me. For example, assume a gradient of 1 : 50 what does the 3.50, 4.2 and 4.85 refer to? I thought maybe it's the distance in meters required to rise 1inch including transitions but surely they won't mix imperial and metric units will they? I'm sure that I am being a little daft here, can anybody help.

 

Also how do you workout what the transition should be?

 

Table is as follows;

 

 

 

One further point, since the gradient will be on a minimum 4ft curve, should the curve also have a cant and if so how much, or how do I work that out?

 

Thanks and best regards

Dan

[Neal Ball]

Good luck Dan, I tried two levels when planning my current layout, but had to give up as it would have menat something like a fall / rise over about 12ft.

 

Not sure you will be able to do a 4 inch rise/fall over 4ft and round a curve at the same time.

 

Let me know how you get on, maybe I will then rip up the current fiddle yard!

 

Regards,

[Dan6470]

 

Not sure you will be able to do a 4 inch rise/fall over 4ft and round a curve at the same time.

 

Hi, It seems that I wasn't so clear, the 4ft rad curve will be within the gradient but the total run would be somewhere in the region of 22ft.

 

Dan

[Kenton]

A gradient of 1:12 (4in in 4ft) is a hopeless ask nothing will manage that.

Gradients on curves are more difficult to negotiate as there are other forces to overcome (side rail friction) and will need to be a shallower gradient. A cant may help a bit.

Gradients must be formed with a lead in and lead out shallower gradient as a sudden change from flat to say 1:50 will cause wheels to be lifted off the rails (problem with power pickups) (full springing may help educe this)

Not all locos have the same traction on gradients and some will struggle (even modern ones) to even drag themselves up a 1:100 slope. (test before fixing anything down.

 

I have no idea what CJF was on about in that table.

[WestCountry]

A gradient of 1:12 (4in in 4ft) is a hopeless ask nothing will manage that.

Actually, I've got one of them - no problems with magnadhesion (Triang) or some traction-tyred locos. It looks stupid though, and I wouldn't do it again.

4" in 22ft is 1:66 isn't it?

[Dan6470]

A gradient of 1:12 (4in in 4ft) is a hopeless ask nothing will manage that.

 

 

I'm not wanting to do that, seems I wasn't so clear in my original post. The 4ft rad curve is within the gradient but the gradient continues after coming out of the curve.

 

Gradients on curves are more difficult to negotiate as there are other forces to overcome (side rail friction) and will need to be a shallower gradient. A cant may help a bit.

 

 

But how much of a cant and which way to cant, surely it could make the problem of side rail friction worse - does anybody have a maths formula for this or is it all down to trial and error? Could be expensive in both time and money

 

Gradients must be formed with a lead in and lead out shallower gradient as a sudden change from flat to say 1:50 will cause wheels to be lifted off the rails (problem with power pickups) (full springing may help educe this)

 

 

I can understand that a sudden change can cause wheel lift so how much of a transition is required, is it a % of the gradient or perhaps down to the length of the longest vehicle?

 

no problems with magnadhesion (Triang)

 

For the Tri-ang you would need steel rail though I don't think magnadhesion works too well on N/S

 

4" in 22ft is 1:66 isn't it?

 

That's what I get it to but 12.5 foot is in the 180° 4ft curve and then say 6ft maybe 7ft of straight before going back into a 45° 4ft curve

[Dan6470]

I've looked at the table a bit more and decided to input (divide) the ratio into the numbers and they all come out at either 70, 84 or 97 and if we consider the following loading gauge (for a better term) diagram and table, you will see that item 'J' in 00/4mm is 60mm.

 

 

 

If a consideration for baseboard material is included (*) then perhaps table 2d: Gradients for 00/EM/P4 Gauge could be presented thus:

 

 

But even if this is accepted it still leaves a problem of the length on the transition from the horizontal to diagonal/slope at the top and bottom of the gradient and also the cant on the curve.

 

Any ideas?

 

Dan

 

(*) Should also include ballast, sleeper and rail height.

[HLT 0109]

If you put a curve into the gradient, it will naturally cant on the curve and, when the track emerges onto the straight, the straight will also be canted unless you twist the track to remove it. Much has been written on this forum in the last two years on the subject of inclines and I can vouch for the fact that, with Hornby track and two 3rd-radius, 90 degree curves within a 1:20 gradient, my Bachmann diesel locos will haul six coaches up the incline. In fact the top 9' straight is 1:15 which does cause difficulty. Steam locos do not do as well. As already stated, the transitions from and to level must be very gentle. I do not know whether different track increases the problems but I have to say I have not seen any signs of extra friction on the curves. In my opinion, if you need an incline to achieve what you want and can do no worse than 1:20 then go for it - making the incline and curves as gentle as possible. The sight of a train climbing 1:20 (or worse) is far from prototypical but, as we cannot scale distance accurately, a compromise has to be made somewhere and I am very glad I installed mine.

[Kenton]

I applaud your, and other's, attempt to fine tune these measurements down to a mathematical formula ... but, in the end I still think there is only one way with gradients - make them bigger than you first thought, test them with as much of the loco and stock you have, and never forget that access may be required where you didn't think about it (this being especially important in dual layer layouts)

[HLT 0109]

I entirely agree, Kenton. In order to get below the upper level, there is a minimum clearance (in my case 7" because I had a dropped section in my baseboard) and, usually, a maximum distance (in my case 9'). Having achieved that, there is usually more space to continue the gradient to give better clearance.

 

Harold.

[cobbjn]

If you want 1:50, I would certainly test it out with your stock first. Diesels will probably be fine, but many steam engines won't cope. I have a 1:60 gradient for my branch line and it is fine with a pannier and a couple of coaches, but some of the bigger engines slip when attempting it.

 

I made the transition around 2 times the length of my longest engine, not for any particular reason, but because that felt right. I kept the curves flat to avoid the issue with cant, but with 4ft radius curves, I can't see it being a big issue.

 

Don't worry about that table - just make the gradient as flat as the can fit in.

 

Jim.

[Dan6470]

Thank you to everybody for your comments and suggestions.

 

I propose to, hopefully tomorrow, cut some strips of board that I have in the garage to test the proposed gradient. I'm hoping to cut enough for a 40ft test track say 8ft totally flat then a transition then the gradient before another transition on to and 8 ft flat at some 97mm above the base. Will test with an assortment of Bachmann loco's, a couple of V2s a B1 and a couple of class 4s each pulling a rake of 8 Bachmann mk1. I'll report back on my findings, if it works then I'll look at repeating the test with a new test rig incorporating a 180° curve

 

Dan

[Dan6470]

Okay, I made my test track as proposed and can confirm that all but one of the loco's were able to pull the 8 coach train. Although it has to be noted that some of the loco's struggled more than others with wheel slip. I think I should investigate whether it is possible to add some additional weights within the body of the locomotives, to date they are totally unmodified. With regard to the one that refused point blank with the train, a class 4 tank engine, it was able to pull a six coach train and I probably wouldn't ask more than that of it.

 

I did find that some of the coaches produced more drag than others which I was surprised at since all the coaches are new out of the box, I've only just purchased them, they've never been run before, I must look at this!

 

Having now seen the amount of clearance under the baseboard at the top of the gradient I am of the opinion that I could drop the height by 12 maybe even 17mm which will result in a shallower gradient. At the moment I'm working with a rise of 97mm over 6.6m = 1/68 if I'm able to reduce the height to say 85mm then the gradient will be 1/77, 80mm would be better still at 1/82 which I think is a 17% reduction in gradient. I will see how it goes.

 

Dan

[Kris]

Are the coaches from different manufactures or do they have different designs of bogies? Either of these could cause the reason for differences in drag. I know that some of my kit built coaches are about 4 times as heavy as the RTR coaches, despite this some are of these kit built coaches have far less rolling resistance than the RTR ones, simply down to the bogies.

[Dan6470]

Are the coaches from different manufactures or do they have different designs of bogies? Either of these could cause the reason for differences in drag. I know that some of my kit built coaches are about 4 times as heavy as the RTR coaches, despite this some are of these kit built coaches have far less rolling resistance than the RTR ones, simply down to the bogies.

 

Hi Kris,

 

The coaches are all Bachmann Mk1s. One of them has a definite problem in that one set of wheels are very stiff, it's not at all free wheeling when you run your thumb against it. I think I shall have to take it back to the shop and have them replace it. With the other coaches, 15 of them, perhaps 8 or 9 of them will free wheel, down the test gradient that I have built, from a standing start. The others will just sit there unless I give them some encouragement .... a small push!

 

With regard to my tests with the gradient, now that I have reduced it to, say a 1/82, all my loco's are able to pull an eight coach train. There is still a little bit of wheel skid but this is now with the class 4 tank engine which I don't envisage pulling that size of train. At some point I will still look at adding some weight within the body of the loco's to assist with traction but I think I'm reasonably confident to progress with the design of my MR.

 

Dan

[gordon s]

Thanks for doing those tests Dan. They're pretty much in line with my own findings that diesels are reasonably OK with most gradients, but steam will grind to a halt with seven coaches on all but the shallowest gradients.

 

I feel confident now that the 1:100 minimum gradient on Eastwood will comfortably take steam locos with seven up. Just a shame I had to scrap a large part of the layout with 1:50 to discover that...B)

[Lord Castellan Creed]

Is the slope going to be scenic or non scenic? If the second one, then have a switchback climb, will save space. Hide it in a tunnel.

Thanks,

Lucas,

[Dan6470]

Thanks for doing those tests Dan. They're pretty much in line with my own findings that diesels are reasonably OK with most gradients, but steam will grind to a halt with seven coaches on all but the shallowest gradients.

 

I feel confident now that the 1:100 minimum gradient on Eastwood will comfortably take steam locos with seven up. Just a shame I had to scrap a large part of the layout with 1:50 to discover that...B)

 

Hi Gordon,

 

It was pretty much your experiences with Eastwood Town that caused me to undertake the test. Most of the books that I have read on the subject seem to point at a 1/50 as a nominal gradient and I would happily have gone along with that but your comments caused doubt to flourish. I'm so very very pleased that you choose to documented and share your experiences. Eastwood Town is a superb project. For those, if there is anybody, that haven't yet come across Gordons' Eastwood Town here's the link;

 

http://www.rmweb.co....od-town-update/

 

Dan

[Dan6470]

Is the slope going to be scenic or non scenic? If the second one, then have a switchback climb, will save space. Hide it in a tunnel.

Thanks,

Lucas,

 

Hi Lucas,

 

Unfortunately most of the gradients are scenic with exception to the one for accessing the fiddle yard but thanks for your comments.

 

Dan