Dimensions and Clearances for the TT:120 scale

[Invicta]

Hello, 

Re-entering the hobby for the first time since childhood and about to start putting together some of my track in a more permanent way. I'm wondering about whether there is any official information on some of the dimensions for the TT:120 scale.

So, I've seen page 30 of the recent paper catalogue which has the various curve radii and track centres, but I'm also looking for things like height clearance above the track and clearance widths, platform heights and overhang of long rolling stock on curves etc.  Couldn't see anything in a forum/internet search, Is there a document of the TT standard, or a measuring gauge tool or something like that that I'm missing?

Currently just using my 08 and some mk3 coaches, and measurements of a 3rd party TT:120 scale engine shed that I bought. But worried that when my 66 and container wagons show up, I'll be clipping things.

Any pointers appreciated.

[Hobby11]

Short answer is No there isn't anything. It's trial by error I'm afraid! If you have a Mk3 coach I suspect that anything else will fit if you use that for clearances. The Mk3 has a BR loading gauge classification of C3, other than tilting trains (C4) the rest are mainly C1, so, at the moment, a Mk3 is big as it gets. If you do get something bigger (such as a Continental coach!) then there's always the "sharp knife" solution!!

Edited April 25 by Hobby11

[Postman On The Rails]

Hight clearance minimum is 45mm from baseboard according to club magazine. If memory serves me correctly but that was also early on 

[dBerriff]

My understanding is that the Hornby track spacing is quite conservative as is usually the case with "set-track". Otherwise we are pioneers and perhaps could share information?

[ntpntpntp]

Things like coach overhang, platform height etc. are going to depend on factors such as the track system you use (and how you lay it), the curve radii, choice of stock you run etc.   I'd argue "standards" for that sort of thing are of little use and just go with what works and looks right. 

Edited April 25 by ntpntpntp

[Invicta]

2 hours ago, Postman On The Rails said:

Hight clearance minimum is 45mm from baseboard according to club magazine. If memory serves me correctly but that was also early on 

Ok, so I was going with 41mm from track height, but measuring my Hornby track it is 4mm high so that tallies if you have no underlay.

[ateshci]

@Invicta

Here are the relevant standards for clearance, and for the formation

Cheers, H.

Edited April 25 by ateshci

[Invicta]

1 hour ago, ateshci said:

@Invicta

Here are the relevant standards for clearance, and for the formation

Cheers, H.

Ah, that's the badger! Great.

[RB51]

@ateshci - good find there and a valuable resource. Unless and until a knowledge base [or similar] comes along could you put them both in either your album or the general album? R-

[ntpntpntp]

Not sure how many of the European MOROP standards cross over to British TT:120?  Loading gauges and clearance probably don't. 

I've seen that same track bed diagram referenced in it's N gauge form as part of the NCI modular standards I follow

[Hobby11]

2 hours ago, ateshci said:

Here are the relevant standards for clearance

Just be aware, as NTP says, that they are for the "Continental" loading gauge, not British, which would be slightly smaller on all but a few British railways. Though if you do use them there'll be plenty of space!

 

Incidentally for clearances on curves the old "taped pencil" method is the simplest and best: "For an outside curve tape the pencil to the inside corner of the coach, for an inside curve to the centre of the coach." Use one of your Mk3s for that as they will have the biggest overhang.

Edited April 25 by Hobby11

[Rallymatt]

As I have some continental Diesels on High Fell and the odd wagon I did allow an extra bit of clearance just in case Hornby TT:120 didn’t match expectations (its way exceeded it) something I allowed for which often gets overlooked was station platform clearances at the cross over for the run around. Even on the longer Peco points overhang is something to check. The rods on the 08 poke out quite a way and I had to trim a bit off my loading dock. 

[Kenneth-365689]

I bought a couple of continental coaches from Ebay to test clearances. It's not a very scientific way of doing things, but I can be pretty sure that if they don't crash into things as they go round, then my British railways stock should make it round too. 

[ntpntpntp]

Those look llke old "shorty" coaches. Modern Continental stock will often be longer than those and therefore more overhang.

[dBerriff]

In what way is not scientific? You have a hypothesis. You have an experimental method to try to disprove the hypothesis. It all looks good to me. Practical engineering in action. 👍

[Invicta]

6 hours ago, Kenneth-365689 said:

I bought a couple of continental coaches from Ebay to test clearances. It's not a very scientific way of doing things, but I can be pretty sure that if they don't crash into things as they go round, then my British railways stock should make it round too.

Plus, it's a great excuse to buy some continental coaches and go down that rabbit hole 😀

For anyone that has access to a 3D printer I've made a simple gauge with those NEM102 dimensions - there's also a 43mm track centre spacer.

STL files are here for £free https://www.thingiverse.com/thing:6595067

WARNING - I haven't added the catenary, so if you have those you'll need to add height if you don't want a haircut.

Edited April 26 by Invicta

[Kenneth-365689]

Thanks Derriff, feeling much brainier this morning 😊🚃🚃

[D9020 Nimbus]

Those TT coaches shown are East German DR "reko" (rebuilt) coaches — modern bodies built on the under frames of older stock — and are considerably shorter than newer coaches, many of which are — in the prototype — 26.4 m long. Indeed, they are so long that many HO coaches were made to a length of 1:100 with the other dimensions at the usual 1:87. Some current HO models may still be to such a scale.

Indeed, even in this country Hornby-Dublo made mark 1 coaches shorter than scale, while Triang emphasised their "scale length" mark 1s, although their full brake was the same length as the others so it was actually too long. The first Hornby mark 3s were also somewhat shorter than scale.

[ateshci]

Sure you can brew your own standards you adhere to on your layout and save a few millimeters ( or shall I say 1/32" ?), but if you want to take advantage of all available TT equipment, it is not a bad idea to adhere to the set standards