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Track Bed

Daniel Clark

Joined: 1-01-15

Topics: 1

Replies: 0

Posted: Tue 12th Jan 2016, 3:07pm
Track Bed

What track bed design does everybody use (e.g. how wide the bed is/how deep)?

Dan :)
 

Replies To This Post

Xz

Joined: 1-01-92

Topics: 17

Replies: 244

Posted: Wed 13th Jan 2016, 11:45am

There are many variables and what suits one may not suit another. Ground conditions, track section and material, expected weight to be carried such as loco sizes, and then the amount of traffic it will see, will all have a bearing on what the minimum spec should be. Quite obviously something that is taking full passenger trains every few minutes and another that is only running a light engine with the occasional truck behind have very different requirements. The stronger you make it the more the costs rise.

It is always a good idea to use a weed membrane under the track. Suitably sized ballast is also essential.
 

paulreed

Joined: 1-11-08

Topics: 0

Replies: 3

Posted: Tue 7th Feb 2017, 3:14am

Dan did you find any info on track bed design, I'm looking for the same info!
Paul
Norfolk
 

johnnicholson

Joined: 1-01-77

Topics: 12

Replies: 69

Posted: Wed 8th Feb 2017, 9:44am

I suggest you also have a look at the archive of the NEWS on here - issue 4 there is a long but superb article on trackbed and laying out.
 

colinedmondson

Joined: 9-08-09

Topics: 3

Replies: 82

Posted: Sun 18th Jun 2017, 5:52pm

The method we used at High Legh in Cheshire was as follows; cut through topsoil and any biodegradeable material down to top of the subsoil, add weed matting and French drains as required, build up to underside of sleeper height with 20mm sharp ballast and compact by walking up and down. Level off to previously surveyed levels and lay track panels, dress with top ballast and pack as required. Ballast thickness should ideally be getting on for half the gap between adjacent sleepers to spread the load and allow for packing. Embankments were built the same way, as planning restrictions didn't allow the use of 'crusher run' as it contained fine dust and might have altered the acidity levels in the soil. A good sharp ballast, tipped into a heap, can be walked up without sliding back at all. If the ballast is too small or at all rounded it will never pack together properly and will lead to a lot more maintenance in the long term. Just for reference we used 75mm wide sleepers at 250mm spacing, closer at the joints.
 

HauteSaoneFrance

Joined: 2-01-14

Topics: 27

Replies: 91

Posted: Sun 18th Jun 2017, 7:11pm

Adding on to this thread rather than start new, with the level crossings and turntable just about complete I'm ready to lay a whole lot of track,

I'm OK with the basic bed having had lots of experience with both bases for buildings and foundations as well as areas for running very heavy machines on and car parks etc, I also have the advantage of having a professional medium weight reversing wacker plate and a twin drum BOMAG roller, sheer luxury?

All my track is pre made up in the workshop on a jig including the curved sections, rail is mostly Cromar White medium steel rail welded to 50 X 5 flat bar at 250 mm centres and projecting 50 mm on each outer side of the rail, I'm proposing to use approx. 75 wide X 22mm thick Masaranduba (a very durable hardwood) for sleepers securing the track to them by trapping the ends of the transverse flat bar with a large square galvanised washer secured into the sleeper with a coarse thread coach screw. I was proposing to make all the track sections up including the sleepers in the workshop and simply lay them onto the pre prepared smooth, level and compacted track bed.

Next stage is to introduce the final ballast what size should that ballast be? I'm assuming it should be of sufficient quantity to end up level with the top of the sleepers and spilling out each side of the track by a margin and it will need to be perhaps laboriously tamped down with a hand tamper?

Have I missed anything?
 

HauteSaoneFrance

Joined: 2-01-14

Topics: 27

Replies: 91

Posted: Fri 28th Jul 2017, 10:50am

My previous post asked about the advisability of laying made up sections of track including the 22mm thick wooden sleepers directly onto an existing level well compacted gravel base then fill in up to sleeper surface height with the angular ballast. I'm aware that this ballast will be just sitting n top of the original base though as long as I make the overall width of the base wide enough I can compact it somewhat by running the wacker plate over. I'm very loath to dig up perfectly good level surfaces which have existed for 10 years, Opinions on this please.
 

Isambard

Joined: 21-09-17

Topics: 0

Replies: 2

Posted: Thu 21st Sep 2017, 11:17am

HauteSaoneFrance: It's very tempting to leave solid surfaces but they are not easy to get to again. Then, once you start digging with a machine it's very easy to go too deep, which increases fill costs. Topsoil should be removed along with tree roots. In my experience, tree roots grow and disturb the track. I always use geotextile, not least because my heavy clay would penetrate the ballast. I lay a minimum of 100mm of Type 1 (60mm to dust granite) then whacker this down. I then lay the track, add more ballast and pack the sleepers. I don't think I'd get the track and base to marry up without this step.
Regarding your other post I have gradients to 1:23 and min 15' radius curves.
 

HauteSaoneFrance

Joined: 2-01-14

Topics: 27

Replies: 91

Posted: Mon 25th Sep 2017, 3:14pm

Thanks Isambard I seem to spend all my time doing extensive work to get reasonable levels on my very challenging site a 21 m by 0.9 m wide X 30 ft radius level crossing, another straight at 4 m and yet another with twin straight tracks laid in at 16 m, Steepest gradient up to now is I in 53 but it's over a curved length (30 ft radius) of 38 m All level crossing have been engineered to take heavy ballast and ready mix concrete lorries, Embankments have been formed with heavy gravel laid up to 600 mm thick. I'm beginning to think the hobby is more about accomplishing civil engineering works than trains? Although I've had quite a bit of experience of heavier construction work including piling in the past I don't think I was prepared for how much this work has entailed when the workforce is just me and a little part time help from friends, I do however have my trusty 3 ton tracked excavator a 3 ton dumper, a reversing wacker plate, motor concrete screeding beam, poker, a pro laser, pencil, paper a calculator, rakes and shovels and a vision that sometimes gets tested to the limit? Sometimes to remind myself what the eventual goal is I drive the little petrol/hydraulic loco up and down the 12 m of track in the shed
 

Isambard

Joined: 21-09-17

Topics: 0

Replies: 2

Posted: Mon 25th Sep 2017, 9:32pm

HauteSaoneFrance: it really depends I guess on what sort of railway one wants. Much miniature infrastructure has been akin to full size standard gauge in terms of scaled radii and gradients, but with increasing numbers of narrow gauge locos running on it. That works well for public hauling, but for one's own plot a more minimal concept can work well, reduce earthworks and land take etc. If you are running a small PH loco do you really need 1:53 and 30' radius? Not a criticism just a talking point - I've been through a similar process. (For example, when I first started building the advice was for much more generous curves than I now know are acceptable with the right rolling stock).
 

HauteSaoneFrance

Joined: 2-01-14

Topics: 27

Replies: 91

Posted: Tue 26th Sep 2017, 5:48pm

Although I've had a long interest in small railways it's only recently that Iv'e started to realise the ambition so I'm learning all the time and grateful for your opinions and those of others. My loco's are a CMD Knight class 0-4-0 a Phoenix Vale of Festiniog electric and though 8 ft long it's a bogie loco, both these loco's will go round less than 30ft radius a third loco to be added soon is a Station Road Steam 0-6-0 Big Feldbhan. The lower loop layout is now just about cast in stone with the radius's and gradients I mentioned. When work starts on the higher level I will know a lot more about the capabilities of the loco's and rolling stock. There is no public running so I'm not constrained in any way by those requirements, My penchant is for minimal gauge hence the larger loco's and rolling stock will be to the same size
 
 
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