Cutting bridge decking with Lucas 618, I need advice.

[fishpharmer]

I have a fella that wants me to cut the decking for a twenty foot long bridge made of treated (former RR bridge timbers).   He plans on cutting the logs nearby the bridge.  Therefore the Lucas 618 mill is the only practical option.   He asked me what would be best species for decking.  I recommended black locust or white oak.  He tells me he has  an abundance of white oak. 

The bridge will be used for anything from a four wheelers to a small dozer.   He wants it to be ten or twelve feet wide.  He gave me the impression the large cross timbers were in place already.   

1. With the limitation of six inch cut of the Lucas (I suppose turning the carriage is an option for wider material) what dimensions would you use for decking?

2. How much space would you put between the decking?

I would appreciate any input.
Fish

[KnotBB]

Disclaimer:  I don't anything! ;D ;D

Small dozer?  Hmmmmmmmmmm?  What does that mean?

I'd say 3" minimum thickness and 4" would be better.  A lot depends on the span between supports.

I don't know about your white oak for rot resistance but with our white oak (gary oak), the sap wood is prone to rot.  Boat builder won't use sap wood for construction.  They want all heart wood.  Just a thought to consider.

[Coon]

What span will the supports be at?  How many supports going across?  I would cut them at either 3 or 4 inches thick and no more than 6 inches in width because of the weight of each piece.  1- 1.5 inches between your decking will allow the moisture and mud to escape. 

[Ianab]

Thickness of the decking is what determines the strength. 2" would be plenty for an ATV, but a "small" bulldozer is a bit heavier. So the 3-4" is more sensible. Also consider the bridge design. If the main beams are under the wheel track of any large vehicle, then the decking is just a spacer, so a brave bulldozer driver could just drive across the beams with no decking. Also a bulldozer is not as bad as it sounds, the tracks spread the load along their length, so a 5 ton dozer probably puts less stress on each board than a 1 ton car. Of course the bridge beams have to support the whole 5 tons.

If you are placing the decking green, then you can probably butt them up and let them shrink as they dry, that will open a sensible gap for drainage.

Another trick that I have seen used is to install your cross ways decking, then run another layer as "wheel tracks" lengthway across the bridge. That spreads the point weight of any wheels across multiple decking boards. Instead of the wheel sitting on one 6 x 3, the load is spread across 4 or so.  That means the 6" wide boards are not an issue.

Ian

[customsawyer]

Another trick that I have seen used is to install your cross ways decking, then run another layer as "wheel tracks" lengthway across the bridge. That spreads the point weight of any wheels across multiple decking boards. Instead of the wheel sitting on one 6 x 3, the load is spread across 4 or so.  That means the 6" wide boards are not an issue.

I would go along with this idea that way when the track of the dozer chews up the runners they are easy to replace.

[ladylake]

 If the tracks on the dozer line up with the supprt beams 2" should be plenty thick. No big knots.   Steve

[Meadows Miller]

Gday

James ive cut abit of bridge decking one job when i was about 17yo was for bridges for the army on their Pucka base about 15mi from home it was Ironbark 6x6 by 12's that was going on 3 18" deep I beams with 1 bolt per beam through the timber they where running 80 ton tanks over them at speed  ;) apparently they are holding up well from what ive heard as one of my mates dad's does maint out there  Mate  ;D

For that bridge it depends where your beams are placed but you should get away with a 6x4" easy i reckon aslong as the main beams are under the load points which i think should be around the 7' apart Mate

Regards Chris

[ladylake]

I've sold a lot of white oak to a trailer manufactor, 95% was 1-5/8 " thick, if they were going to be hauling a D8 cat they wanted it 2" thick. For a small dozer if the support beams are near where the tracks are over 2" is just a waste.   Steve

[Magicman]

James, on my bridges, the decking is 2" thick and 3" apart.  My widths vary from 6"-12".  All of my bridges are 10' wide.  In this case, I would add runners on top of the decking for the dozer tracks.  I have no runners, because anytime you "sandwich" lumber you provide a place for moisture to hide which contributes to rot.

White Oak is the logical species choice.  Don't worry about stickering and drying.  It'll dry quite well after it's nailed down.



Full cut 2X6, 2X8, 2X10, & 2X12 White Oak bridge decking.

[metalspinner]

I've read that Chestnut Oak (one kind of white oak) is not rot resistant.  It has open pores similar to red oak.  Thus, cooper barrel makers will not use this species.  Just another consideration in choosing your logs.

Please correct my second hand knowledge if warrented. ;)

[fishpharmer]

I knew I could count on some great input from my fellow FF members.  Thank you.  Great info by all.

Guess I should have defined a "small" dozer.    I had a JD 450 or smaller in mind when I wrote that, maybe a definite weight would be a better paramater, so lets say 15,000 lbs max.

CS, great idea about the "wheel tracks" for tracked machines.

MM, are you talking about something like this....

Look familiar? ;)
The picture makes me want to recommend spacing that won't allow an average human foot to slip between during an early morning hiking to the tree stand.

Thanks everyone.  Anyother ideas would be great. 

[Magicman]

That looks like live edged Black Locust that has been down about 4 years.

[ljmathias]

Well, Magic, you can't need that "rebuild" too badly if you can still recognize your own bridge right off the bat like that.  And if you didn't, who'd know? As they say about us older people with memories that are more "porous and leaky:" everyday is a new adventure, especially if it's your own land and family.

Lj

[Magicman]

if you can still recognize your own bridge Lj 

Not only the bridge, but the exact boards.  They all had to be pre-drilled before they could be spiked down.