Repairing my 18 year old timber trestle

[gregh]

I notice that JR inTawa has been doing trestle repairs. http://www.gscalecentral.net/HampMGR-a-family-railway-in-NZ-m9330-p29
It must be the season in the southern hemisphere!

I built my big trestle back in 1995, from tomato stakes (good Aussie hardwood) hammered directly into the ground. It consists of 18 spans, about 1.2m high, on a 2.2m radius, and a 2% grade, with a total length of 8m. I remember thinking as I was building it, “I hope this lasts 10 years”. I didn’t paint the wood, and used plain steel bolts and screws – silly boy!

Well after about 10 years, the timber in the ground was rotting so I put concrete footings around most of them, using rapid set concrete.

Now after 18 years, the top plates are so rotten that the track is holding the bridge up, not the other way round! Most of the stringers are also showing signs of deterioration on the horizontal surfaces. So it’s time to repair. Shut the line. Busses replace trains!!

Before starting on the bridge, I rebuilt all the track – it’s my ‘old’ method of aluminium bar in slotted sleepers. Then with the track strong enough to move, I removed a 6’ panel at a time and started work.

I cut the bolts with an angle grinder to remove the top caps and corbels, filled the holes and cracks in the top of the piles with Builders Bog and painted them. Then I screwed new top caps onto the piles, painting where all surfaces meet. The new corbels (8mm treated pine) were screwed on and then the new stringers screwed to them, all using nickel plated screws.

Then I replaced the track panel and moved onto the next panel.
Only one of the trestles needed major work – it had been pushed out of alignment by a jacaranda tree root.

So I dug around the root, put lots of Styrofoam around it and poured a ‘bridging foundation’ across the root using rapid set concrete, with a few bits of scrap steel thrown in for reinforcing. Hopefully as the root grows it will just squeeze the Styrofoam. I rebuilt the trestle itself and installed it just resting on the new foundation. I included extra ‘spacers’ on the top cap which can be removed if the trestle is pushed up by the root. Fingers crossed!

So far I’ve finished about 2/3 of the work. ‘Then for the safety rails’

 

[tramcar trev]

Wow Greg what a project! maybe you should have got Bradfield to do a new design and then got Dorman Long to build it for you. That is a most impressive trestle.....
Have you told us how you mass produce the sleepers with the slots in them for the rails?

 

[Beddhist]

Thanks for sharing this, it's giving me some ideas...

I'm just devouring your web site. What a great layout you have built there.

(The last picture on your page "Sandstone cutting" is missing.)

Thanks,
Peter.

 

[gregh]

Thanks for sharing this, it's giving me some ideas...
I'm just devouring your web site. What a great layout you have built there.
(The last picture on your page "Sandstone cutting" is missing.)

Thanks for your comments. I've fixed that picture (but found lots of others missing.)

 

[gregh]

Wow Greg what a project! maybe you should have got Bradfield to do a new design and then got Dorman Long to build it for you. That is a most impressive trestle.....
Have you told us how you mass produce the sleepers with the slots in them for the rails?

Sandstone & Termite's Design and Construction teams are quite capable.
Re the slotted sleepers......

I made about 150 of the slotted sleepers last week but didn’t take pics. In the ‘good old days’, when the only power tool I owned was a drill, I cut all the slots by hand, with 3 hacksaw blades taped together to give the 3mm width. And a steel jig to give the gauge.
You can see some of this here….. about ½ way down the page.
http://www.members.optusnet.com.au/satr/track.htm

Now I use a router with a 1/8” bit. I’ve glued a spacer to the router so that I can cut slots 45mm apart along a length of wood. Then I cut the wood between every 2nd slot to give a 38mm width of ‘sleeper’ about 96mm long. Then put them in this jig to cut into thirds with a jigsaw, to give the finished sleeper about 11mm wide. The pics might make it clearer.

 

[CoggesRailway]

Out of interest, is this much cheaper than commercial track? Or more about the satisfaction?

 

[gregh]

Out of interest, is this much cheaper than commercial track? Or more about the satisfaction?

It's certainly not about satisfaction-just cost.
The 10x3mm Al bar costs about $2.60/m these days, so including sleeper wood, track would cost me around $A6.50/m. It must be cheaper than brass commercial track. ( I've never bought any.)
Making my own track using brass rail on timber sleepers costs about $A14/m

Generally, I'm replacing the Al bar track with 'normal' brass rail nailed to timber sleepers, on my mainlines. But I still use the Al bar track on sidings.

But this bridge was an exception - I couldn't afford new brass rail, so stayed with rebuilding the Al bar. I'm taking a lot of effort to ensure the track is all well screwed down to the stringers, so the sleepers can't work loose. This is the biggest problem with the slotted sleepers. But they work great if they can be screwed to a solid base.

 

[JRinTawa]

As you'd have guess I can sympathise with the need, though your trestle is far more impressive than mine!

 

[beavercreek]

Excellent bit of recovery work Greg. A darned fine trestle too!

 

[gregh]

I’ve finally finished the trestle repairs and relaid the track.


The trestle contains  75m of 25x25mm timber,  70 m of 8x10mm bracing and  150 kg of concrete in the foundations.

Here’s the first passenger train


Now I need to decide whether I need to fit safety rails.
When I originally built the trestle, it had no `safetyrails` and I had a few trains `take a dive` after derailing.  So I added these ugly 4” nails and twisted fishing line to catch misbehaving trains.  The lines are about 50mm above rail.



I also added ‘walkways’ to give a reason for the handrails, but these soon warped and fell off.


The most common derailment is a string-line accident where a rear wagon derails and ‘sticks’. The loco keeps pulling and all the intervening wagons string-line to the inside of the curve. (I use hook and chain coupling so they never come apart in a derailment !)
The fishing line has worked well, but I wondered if they need to be so high (and therefore so visible/out-of-scale/ugly).

So I decided to do a few static tests.  First I tried to find how high above rail a wagon’s centre-of-mass is.  For my lightest boxcar, it seems to be about 70mm above rail.  Heavier wagons, with more weight lower down have lower CoM.  Now how high does the safetyrail need to be to stop the wagon tipping right over the rail, and how far out from the rails ?
Theoretically, if the safetyrail is more than 70mm from the rail and level with the rail top, the CoM will never be outside, it so the wagon can’t fall. But that is the static case, and if the wagon is being pulled, it would probably slide ‘over the edge’ anyhow.

It turns out that on the 2m radius trestle, I need the safetyrail to be a min 60mm from rail for vehicle clearance.
Conclusion:  I’ve decided to make the safetyrails 25mm above rail top and 65 mm out. The static case will then look like this:



I’ll do a couple of trestle bents and then TEST.

Now I need some ideas on a better looking safetyrail system.  Are there any pictures of timber trestles with safetyrails out there?  I guess that once I need a safetyrail system, then I logically need a walkway for the safetyrail to `protect`.  Here is the solution I like best so far. It uses plastic mesh gutter guard and styrene walkway on the inner side of the curve only.  The outer side would be just fishing line with no walkway.


The trestle is under big trees, so I need something that can at least withstand say 2" dia branches falling on it. ( the trestle itself is much stronger.)  And Kookaburras like to sit on the safetyrail watching for their next worm.

Any comments on whether I should have different height walkways/safetyrails on each side of the track?

 

[Beddhist]

With the wagons tilted like in your diagram, are the couplers above to top of the hand rail? If they are the wagons could be pulled over the top, even if the CG is lower.

You could accommodate the birds by making the hand rail strong enough, or deter them by putting up some obstacles, like a telegraph line. In fact, even this could be part of your safety system, if strong enough. Make the masts strong and somehow have some give in the lines, then branches won't damage them and I guess the birds won't like settling on them, either.

I would worry about those nails damaging my rolling stock when they get dragged past...

 

[gregh]

With the wagons tilted like in your diagram, are the couplers above to top of the hand rail? If they are the wagons could be pulled over the top, even if the CG is lower.

You could accommodate the birds by making the hand rail strong enough, or deter them by putting up some obstacles, like a telegraph line. In fact, even this could be part of your safety system, if strong enough. Make the masts strong and somehow have some give in the lines, then branches won't damage them and I guess the birds won't like settling on them, either.

I would worry about those nails damaging my rolling stock when they get dragged past...

Good point about the coupler heights. The hooks on the wagons are at about the nail height or a bit higher I'd say - will check it during my testing.
Good idea about making the fence into telegraph lines - I've used 8mm garden irrigation pipe fpr poles previously, so could try that cheaply.

The (higher) nails have been in place for years - trains don't get dragged past too far - they hit the nails and stop. And less damage than falling a metre!

I'm am making up a 2m section of fence now. Will then see how game I am to deliberately derail some older wagons at speed. Hopefully get a few friends over in a position to catch them, or the loco at least.

 

[dunnyrail]

Greg, personally I don't think that the nails look too bad. What I think would improve things with them would be a second line to give more indication of the Safety Rail. Then of course you would need to think about the walkway again. Perhaps as you did them but with a couple of extra cross supports for each length may work fine. Going to look in my Books to see if I can find a Trestle Safety Rail for you.
JonD

 

[dunnyrail]

Greg as promised I found this picture, pretty hefty amount of work but at least it is a Real Picture.  I guess with your timberwork skills this should not be too much of a problem. But I would think about pinning it all up with Veneer Pins.

Sorry about the quality, but it should give you the concept.
JonD

 

[beavercreek]

Greg as promised I found this picture, pretty hefty amount of work but at least it is a Real Picture. I guess with your timberwork skills this should not be [attachimg=1]too much of a problem. But I would think about pinning it all up with Veneer Pins.

Sorry about the quality, but it should give you the concept.
JonD

Is this one in the Antipodes ?.....

 

[dunnyrail]

Yes it is Down Under, however I have seen similar in a book that I have of Jugoslavian NG that is somewhat similar. I have not seen any similar in USA as yet, but then I have not been looking. Surprisingly most Countries appear to end up with similar ideas, presumably due to many Engineers doing work worldwide.
JonD

 

[Andrew]

Looking good Greg. Always a great wealth of information. I like the pics of the sleeper grooves for rail.
Cheers from Andrew
Sandbar & Mudcrab Railway

 

[gregh]

Greg, personally I don't think that the nails look too bad. What I think would improve things with them would be a second line to give more indication of the Safety Rail. Then of course you would need to think about the walkway again. Perhaps as you did them but with a couple of extra cross supports for each length may work fine. Going to look in my Books to see if I can find a Trestle Safety Rail for you.
JonD

I'm coming round to the idea of sticking with the fishing line too. And adding a second 'string' and some intermediate posts is a good idea. I'll be trying that with the telegraph poles idea over the weekend. I'm going away from the mesh idea. And will probably have a walkway on one side.
Thanks for the pic, but those wooden handrails sure would be a lot of work to make and then be broken by the first branch that falls. I did like the big diagonal supports though - I could have used that instead of replacing the bent and foundation over the tree root.

 

[Beddhist]

Is this one in the Antipodes ?.....

Nooo, this is a safety rail for a suspended railway!

 

[tramcar trev]

A chap I know used clear perspex as a "safety device" to stop his very expensive live steam locos falling to destruction but I think the "fence idea" is more realistic and would do a better job. I'ts sure a structure with "presence".