Gradients: How steep in the model world can they be?

[JST]

Another vote for the suck it and see method. I needed my Bachmann Panniers and Prairies to haul 5 coaches up my branch line bank without failing. By trial and error I discovered that 1:100 over 14 metres was the answer.

[rogerzilla]

As in the real world, having all axles driven will make the most of the tractive effort, so an 0-6-0 will do better than an 0-4-2 of the same weight, and big diesels with all axles driven will do better than big steam models.  1 in 50 is the usual rule of thumb without magnets or other tricks.

[AndyID]

On 15/12/2019 at 12:21, rogerzilla said:

As in the real world, having all axles driven will make the most of the tractive effort, so an 0-6-0 will do better than an 0-4-2 of the same weight,

 

It might if the 0-4-2's trailing wheels are supporting any weight as they would if it were a real locomotive, but if they are cosmetic it will produce just as much traction as an 0-6-0 of the same weight.

 

You can convert a model 2-8-0 into an 2-4-0 by removing the middle driven wheels and it won't make any difference to the traction. ME's had no love of additional driven wheels but as locomotives became larger they had to add more wheels to keep the civil engineering departments happy by limiting axle loads.

[DCB]

On 15/12/2019 at 15:24, JST said:

Another vote for the suck it and see method. I needed my Bachmann Panniers and Prairies to haul 5 coaches up my branch line bank without failing. By trial and error I discovered that 1:100 over 14 metres was the answer.

My Bachmann Prairies are fine with 4 suburbans up a 1 in 36 ish.  One of the Panniers is DCC ready and won't pull the skin off but the others are also OK with 4 suburbans up the 1 in 36. Just wondering if the 1 in 100 id from Horizontal or from the baseboard surface?

5 minutes ago, AndyID said:

 

It might if the 0-4-2's trailing wheels are supporting any weight as they would if it were a real locomotive, but if they are cosmetic it will produce just as much traction as an 0-6-0 of the same weight.

 

You can convert a model 2-8-0 into an 2-4-0 by removing the middle driven wheels and it won't make any difference to the traction. ME's had no love of additional driven wheels but as locomotives became larger they had to add more wheels to keep the civil engineering departments happy by limiting axle loads.

The old Dapol /Hornby 14XX pulls much better minus its trailing wheels but looks a bit daft without them. However I have found the Bachmann 2-8-0s with sprung centre drivers are four or five wagons better than those without, though nowhere near the power of the Wrenn 8F which has only 4 driving wheels on the track. Also I have found reducing the weight on the front driving axle of a GWR 4-6-0 can improve the traction as with too much lead in the smokebox the rear wheels barely take any weight.  The old Hornby Dublo Duchess wouldn't pull more than three coaches but  noticed the Wrenn ones had the tender drawbar the other way up, simply altering the H/D one to wrenn style just about doubled the traction as the loco tried to lift the tender when pulling hard instead of the weight pressing down on the pony truck.  Drawbar dead in line with couplings seems to be optimum.

[AndyID]

48 minutes ago, DavidCBroad said:

The old Dapol /Hornby 14XX pulls much better minus its trailing wheels but looks a bit daft without them. However I have found the Bachmann 2-8-0s with sprung centre drivers are four or five wagons better than those without, though nowhere near the power of the Wrenn 8F which has only 4 driving wheels on the track. Also I have found reducing the weight on the front driving axle of a GWR 4-6-0 can improve the traction as with too much lead in the smokebox the rear wheels barely take any weight.  The old Hornby Dublo Duchess wouldn't pull more than three coaches but  noticed the Wrenn ones had the tender drawbar the other way up, simply altering the H/D one to wrenn style just about doubled the traction as the loco tried to lift the tender when pulling hard instead of the weight pressing down on the pony truck.  Drawbar dead in line with couplings seems to be optimum.

 

You can definitely transfer some of the train load to the drivers which is why 4-6-0's tended to slip a bit less than 4-6-2's on starting (and a FWD car will also climb an icy road backwards better than frontwards) but the the biggest factor (for us modellers) is simply the total weight on the driven axles. My point is it doesn't really matter how many axles are driven. Contrary to popular belief, adding more axles on models does not make any difference. It also doesn't make any difference whether they are sprung or not.

 

I'm not making this up. It's just basic Physics that I learned from a great teacher in Scotland 53 years ago.

[rogerzilla]

It's not the number of axles, it's the percentage of weight on driven axles as opposed to carrying axles (and I take the point that carrying axles on steam models often only carry their own weight).  In the real 1:1 world there are complex things going on at the wheel-rail interface due to significant deflection under the weight, which mean wheel diameter has an effect.

 

At its simplest, an old diesel model with one power bogie will struggle for grip compared to one with two power bogies.  The latter has roughly twice the adhesion because it's using all its weight.

 

At least electric models don't have to cope with the varying torque from steam cylinders, which promotes slip even when the factor of adhesion is above the usual design standard of 4. 3-cylinder locos and Lord Nelson 4-cylinders are better for even torque.

Edited December 17, 2019 by rogerzilla

[Colin_McLeod]

All these very steep gradients on the prototype are associated with operational restrictions so I personally would not design my layout round them.

 

If you have a continuous run I would suggest trying to keep that level, and if it must have a gradient then keep it as gentle as possible.  Remember if there are steep gradients on your continuous run, every uphill has a corresponding downhill and you will have to "drive" every train round as constant speed controllers have their limits.  That can get really tricky on a double track main line.

 

I have designed my layout with a maximum main line gradient of 1 in 100 and this is on the approaches from the storage sidings and not the continuous run.  I am fortunate enough to have the space to do this.  If I hadn't, then the maximum I would like would be 1 in 60.

[JST]

On 17/12/2019 at 04:24, DavidCBroad said:

My Bachmann Prairies are fine with 4 suburbans up a 1 in 36 ish.  One of the Panniers is DCC ready and won't pull the skin off but the others are also OK with 4 suburbans up the 1 in 36. Just wondering if the 1 in 100 id from Horizontal or from the baseboard surface?

 

 

Just checked with a spirit level - it appears to be dead horizontal! How did that happen?

[gordon s]

That's one of the problems I've had with gradients. You need a datum level from which all measurements are taken. It's hopeless taking a measurement from the baseboard, if the baseboard itself isn't level. Then it's no good taking an individual baseboard and setting that level as the other end of the gradient could be 15' away on another board and they may both be level, but not sitting on the same plane across the room.

 

I played around for ages using a laser level on a tripod to get all the baseboards level and in the same plane across the room because you are quite right, a supposed 1:100 gradient can easily be level or 1:50 if you are not starting from the same datum level right around the layout.

[RAF96]

Good point about the datum plane.

I use 2% (1 in 50) as my fleet usable max gradient but if you are restricted on length to achieve this and the layout accommodates the plan (say one line simply over-bridging another) then you can half the gradient by dropping the ‘flat’ track by the same half slope i.e. half up slope and half down slope at 1% (1 in 100).

[Junctionmad]

Gordon in his Eastwood town thread , suggested 1:100 for main line steam model  locos and at the very worst 1:50 for diesel 

 

 

[gordon s]

My latest version of ET means I have to use a 1:85 gradient from a low level traverser. Hopefully in a few months I’ll have some idea how RTR steam loco’s will cope with seven coaches. I know others may disagree, but 1:100 is ideal if you have the length of run. Any curves on the gradient will certainly make it tougher.

 

Diesel loco’s have much more tractive effort. Generally speaking they are heavier and have more driven wheels. There have been times when I’ve considered pensioning off my steam loco’s.....

[Sol]

On 23/12/2019 at 02:59, gordon s said:

 

 

Diesel loco’s have much more tractive effort. Generally speaking they are heavier and have more driven wheels. There have been times when I’ve considered pensioning off my steam loco’s.....

 I did pension off my steam locos when rebuilding  my layout - diesels don't need turntables generally compared to large steam locos..

[Tallpaul69]

11 hours ago, Sol said:

 I did pension off my steam locos when rebuilding  my layout - diesels don't need turntables generally compared to large steam locos..

You can manage without turntables with steam-just keep half your tender locos facing one way and the other half facing the other!

And tank locos don't need turntables at all!

Yes, diesels have a lot going for them, but even when running modern image, I still have a couple of steam specials running.

Happy New Year All

Cheers

Paul

[imt]

On 26/12/2019 at 16:24, Tallpaul69 said:

I did pension off my steam locos when rebuilding  my layout - diesels don't need turntables generally compared to large steam locos..

 

Buy a PECO Locolift - it fits over the track so you can run locos on to it, pick it up, turn it and put it down again.  I HAVE seen this done on scenic sections, but most people have a short siding in their fiddle yard and run locos from the station to an invisible shed for servicing and return.

[Tallpaul69]

Sorry imt, I didn't say that at all, Sol said it! My steam loco fleet is very well and set for a long future.

 

So Sol needs to read your comment about Peco Locolifts.

 

I agree with you its a possibility, but I don't need one!

 

Cheers

Paul

[67A]

Hi David,

 

Only just seen your post and 'Peach-James' has provided a link to my 'DENT' thread. I would just like to add although in principle the spirals which worked out at 1:75 when elongated continued to give rise to problems such as the inability of some loco's to tackle the gradient unassisted, I converted two BG full brakes with the REPLICA RAILWAYS powered chassis which allowed heavy trains to perform quite well so that seemed to work on the uphill struggle, the downhill presented its own dilemmas due to the supposedly universal tension lock couplings over-running and causing bufferlock resulting in derailments more often than I could tolerate, it was at this point I took the decision to abandon the system and revert to initially an end to end format followed by a roundy-roundy due to lack of play value.

 

Hope this helps.

[The Black Hat]

Hello all,

 

I've purchased a Woodland scenic's 3% gradient profile set that allows me to construct a gradient based on their profile. Will update how useful this all is in due course as layout is still in planning stages but coming together nicely. There's a lot of information here that I think many reading this will find useful especially if searching for information in the future.

 

Thanks all.

[ColHut]

FWIW I second all those comments regarding keeping gradients to a minimum.  Curve friction and gradients together are a real killer.  Powerbase is not the answer for steep curving gradients either (I use it on 60'  of underboard dogbone loop about on a 1 in 35).  There are issues with where you can place the magnets, how visible they are, how close to the rails they need to be, striking slight obstacles and uncoupling points, having to remove brake gear, brass etch magnet holders very flimsy and retaing screws magnetic &c. 

 

Strongly suggest you do your own tests with various gradients, curves and loads, and take the worse case!

 

Only you will know if you are content with the results.

 

good luck.

 

 

[MikeTr]

I'd be interested to know if the rules of thumb quoted for OO gauge also apply to N gauge. 

 

I'm builiding my first layout for donkey's years and space limitations pushed me to N gauge.  Some gradient tests early on with a Graham Farish 2-6-4 'Fairburn' tank (my first, and at the time, only loco) showed it could climb 4% with 4 coaches so I went ahead and started building a 2 level layout with 4% gradients (nearer 3.3% now that I've measured them).  Now I find that the Fairburn must have been a cracking climber because nothing else apart from a DMU can get up the slopes!  An oldish GF Mallard fails miserably and a more recent GF Castle class is even worse!  Is this typical or have I got a couple of duff locos? 

 

I've even tried roughing up the tracks (Peco code 80 flex) with coarse sandpaper to try and improve traction but all (so far) to no avail.  Just thought I'd seek some wisdom here before I rip up the layout and start again.

Edited February 3, 2020 by MikeTr
typo

[Dungrange]

17 hours ago, MikeTr said:

I'd be interested to know if the rules of thumb quoted for OO gauge also apply to N gauge. 

 

I've no experience of N gauge, but being smaller and the stock being lighter, I'd expect locomotives to have less adhesion than a similar 00 gauge model and therefore I'd think that the gradients should be flatter in N gauge than in 00.  4% is 1:25 and 3.3% is 1:30, which are both very much at the steep end of the spectrum - the recommendation would be for a flatter gradient, even in 00.  My first 00 layout (back when I was a teenager) used these sort of gradients and two coach trains were pretty much the maximum and my Hornby 0-4-0T really struggled with that.  As I didn't want to run one coach trains, that layout was quickly scrapped and the idea of gradients abandoned.

Edited February 3, 2020 by Dungrange

[mdvle]

11 hours ago, MikeTr said:

I'd be interested to know if the rules of thumb quoted for OO gauge also apply to N gauge.

 

The underlying physics doesn't change simply by changing from OO to N to O to etc.

 

Each model behaves differently depending on the available weight and where the weight is centred, and in general diesel/electric will deal with it better than steam.

 

 

[Sprintex]

13 hours ago, MikeTr said:

 

I've even tried roughing up the tracks (Peco code 80 flex) with coarse sandpaper to try and improve traction but all (so far) to no avail.

 

 

I'd replace ALL that track you "roughed up" if I were you as you've now created the perfect rail surface full of scratches to hold dirt and grime, which will transfer regularly to the wheels of your locos and stock causing endless running problems for ever more.

 

Paul

[NIK]

Hi,

 

There is tremendous variation in grip between different locos.

 

My Heljan OO  Class 128 single car parcels unit will go up a 1 in 5 gradient (no DCC Concepts Powerbase or talcum powder or roughened rail tops).

 

I haven't done any gradient tests on N gauge stock but it might not be entirely proportional to scale.

 

A plastic bodied loco might not have proportionately thinner walls than its 4mm/foot equivalent so the weight of the chassis may be lower than expected from the scale. The rolling stock may not be as light as expected (to make sure it stays on the rails?). The friction of the rolling stock chassis may be a bit higher than expected.

 

Regards

 

Nick

[MikeTr]

On 03/02/2020 at 13:46, Sprintex said:

 

 

I'd replace ALL that track you "roughed up" if I were you as you've now created the perfect rail surface full of scratches to hold dirt and grime, which will transfer regularly to the wheels of your locos and stock causing endless running problems for ever more.

 

Paul

 

Hmm - good point - I hadn't thought of that.  I think I'll start looking into a new layout - and keep it flat this time!  Thanks for your input chaps.