Gradients and Helixes in TT

[Too Tall]

Ok so I have been delving into gradients and have come across a query ...

Given the generic given max "safe" gradient often is stated to be 2% for steel wheeled locos, it appears to me most helixes exceed this while also being a curve.

Working on the assumption helix kits often use R3 and R4 for a double track helix:  In TT I thought 40mm minimum clearance for a UK (non pantograph) loco + track height 5mm + underlay 2mm +baseboard thickness of 6mm+ a total height of 53mm using as thin baseboard material as you might want to use.

With the inside of a double track being R3 that would make that a 2.5% gradient (according to SCARM), that the loco would have to negotiate while pulling a load round a curve. 

With a more comfortable 60mm clearance, that would make it 2.8%.

Of course you could use flexi track and have larger radius curves, but generally I thought most modellers use set track for Helixes ?

So is using TT R3 and R4 set track for a Helix going to be too much for our Hornby TT120 Locos to haul a train of 5 or 5 coaches up comfortably ?

[Yelrow]

TT, hi, i have 2 helix, albeit, 00, but  both made with flexi track. You need as few joins as possible given each one a derailing hazard, usually in a hard to reach place. mine are both double track.  My gradient is 2.5. Originally it was one 7 tier rising 29 inches.  now have them linked by a bridge in continuous loop.

[Chris98]

May be useful, my personal expetience, I tried several different inclines all including curves of at least r3/4 and wider. I found anything over 2% was too much and loco's could not manage it. Even tried the dcc magnets and plates (power base) under the tracks but this did not make any difference.  I settled for 2% with no power base and not had any problems. 

Edited March 23 by Chris98

[Skelton Junction]

At Skelton Junction there are two gradients to the elevated section, 2% and mallard pulls 4 mk1s happily or a dozen trucks. 3% will climb but with less authority (think Henry, not Gordon). 
HST (both locos and three coaches) does both without blinking. 08 will do half a dozen trucks ok. any more and there’s a complaint. 
I’m expecting the 50s and 66s to emulate the HST and do both with ease. 
hope this helps in some way. 

[Moccasin]

"we can do it, we can do it, we know we can" - no TT120 Annie & Clarabel yet...

[Skelton Junction]

Though once the TT120 tank engine appears and pulls the 50 and 57 footers out of platform 3 down the Dyffryn Conwy branch line then that’ll be what the Reverend based it on (for me). 

[Too Tall]

But would mallard manage 6 mk1s on a 2% SJ?

So it does look like 2% is max , I think 00 would have a bit more grunt in the motors as well as being heavier, so that could why they manage Yelrow's 2.5% ?

TBH I hadn't considered that gronks and smaller tank engines wouldn't be as able ! but then they wouldn't be hauling as much prototypically anyways, but 6 wagons is quite a bit less than ideal 😃

To keep it at max 2% on the TT helix would mean the inner curve would need to be the equivalent of a Hornby R3 (radius 505mm) so  pretty much a 1.1m square required for  a twin track TT helix, That compares to using 3.0M of straight to rise to 60mm, food for thought indeed 🤔

Edited March 23 by Too Tall

[Iron Body]

That's why I'm planning on having two completely separate loops.  Lower loop for mainline expresses and an upper, smaller loop for goods traffic.  The upper loop is waiting for a suitable steam 0-6-0 or black 5.    I don't like seeing an A4 pulling wagons.   

[Rallymatt]

6 minutes ago, Iron Body said:

That's why I'm planning on having two completely separate loops.  Lower loop for mainline expresses and an upper, smaller loop for goods traffic.  The upper loop is waiting for a suitable steam 0-6-0 or black 5.    I don't like seeing an A4 pulling wagons.   

It used to happen on a more regular basis than at first we would imagine. A4s were even known to do local freight and shunting, not that often but fun to know it happened 😁

[96RAF]

See here https://images.app.goo.gl/tG84S52ZNaSfwkMB9

[Iron Body]

3 hours ago, Rallymatt said:

It used to happen on a more regular basis than at first we would imagine. A4s were even known to do local freight and shunting, not that often but fun to know it happened 😁

OK, and thanks for the pictures.  But I don't think Mallard will pulling my 4 coal wagons.

[ateshci]

I just learned that the 50mph-scheduled "266 down" was almost exclusively run by A4s. Interesting to note that those short wagons, if handled properly, could achieve that speed.

[Rallymatt]

Do share any info pics 😁👍

[ateshci]

@Rallymat
Matthew 7 as cited by Google: Ask, and it will be given to you, seek, and you will find -

Text , picture1 and picture2

Edited March 25 by ateshci

[ateshci]

Here's a picture of an A3 doing the same.

[Rallymatt]

The A3 is doing an impersonation of Trigo on High Fell 🤣. Thanks for sharing @ateshci 😁👍

[ateshci]

Now back to topic -how can you get an A3/A4 model to pull a rake of say 10-15 ( roughly 1m long ) wagons over the grades model railway space restrictions dictate?

[Rallymatt]

I have heard of people ‘painting on’ a traction tyre, using a rubber solution paint. If it’s done thin enough it shouldn’t affect ride height too much 

[Hobby11]

It's called Bullfrog Snot(!), but it's used to replace an old traction tyre where it'd be impossible to get the wheel off without major surgery or they don't make the tyres any more. I'm not sure it would work on a wheel without the slot, though, surely it would leave the chassis out of true? Never tried it so don't know!

http://www.bullfrogsnot.com/howtoinstall.asp

[ntpntpntp]

Not a fan of Bullfrog Snot nor using Copydex for this purpose.  If the wheel isn't made with a groove to accommodate a traction tyre then adding snot to it just increases the diameter and lifts the chassis so it's not riding properly.
I've yet to be in a situation where I cannot replace a traction tyre, even if it's with a 3rd party tyre.   Tyres should last a long time, but can be affected by some of the track cleaning or continuity improver potions some folk like to use.  I don't allow any of the those on my trackwork 🙂
I'd love to get hold of a spare set of driving wheels for a Pacific and machine out a groove for a tyre.

Edited March 25 by ntpntpntp

[Rallymatt]

Nick, Inox MX3 will absolutely destroy traction tyres so you are wise to avoid. I tested it to prove it to myself… only when I had a stock of spare traction tyres to call upon. 😁

[Too Tall]

TBH I think I am just as confused now as I was before on this subject !

I have been trawling YouTube and notice many American layouts (and some European) quite often have 3 or 4% gradients. I know some European locos have tyres, but do American loco's have them too ?

Then I watched one of Chadwick's (not a fan TBH, but I was just looking for relevant stuff) 00 steam loco's on his (albeit 2.8 ish percent) spiral, were really struggling. The diesel locos were taking it in their stride.

Thoughts of a second layout have been buzzing in my head, when I have finished up Millwood, and 2 levels appeals, but only if ALL locos could manage inclines with something approaching protoypical loads 🤔

 

[Yelrow]

They won’t. Modern locos have insufficient grunt to pull loads up a helix. I have sufficient space to give my trains a 4 foot run to start of helix, meaning they hit it  on the run. All my locos are DC, on helix, so at least 25 years old.  There is a lot of nonsense and claims of locos running on a helix. I doubt one would be totally successful in TT. I run Triang ,TT, and built a raised track  2 years ago. It took  a 12 foot run , before loco would manage the height.

[Skelton Junction]

I’m considering returning the elevated section to baseboard level and moving the branch line turn out to the other side of the layout thus providing the additional length to just go up to the fiddle yard/halt rather than the loop having gone up and down in the space. 

[Skelton Junction]

Any passing resemblance to Skelton Junction is but a memory from January last year and I can see why folks give their layouts fictional names. Still, as @Too Tallsaid, prototypical running is important. Also, rule #1 😊.