# New bridge pics



## dubthang (Apr 2, 2009)

Thought I'd share a new bridge that I finished today. It spans an area that usually has much more water under it than now. It was built using mostly hand saws, battery powered drill/screws, and hammer/nails. The thing is solid, and took about three day to create.

Compound image to show length.








View from other side.








One end of the bridge.








And the other.









It is very ridable, and flows nicely with the trail.


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## mrben0101 (Sep 16, 2008)

Is this wood something that you found or biked in?


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## Bob W (Jul 6, 2004)

*wow*

that look a little scary, should last what a month...


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## dubthang (Apr 2, 2009)

Thanks for the comments.

I am actually a well trained wood worker so the bridge is structurally sound. Everything that is round is notched into place, screwed and nailed. It is a very solid structure. The wood is a mix of biked in planks, and harvested timber. I left larger gaps (6" - 7") between the planks to raise the tech of riding the bridge.


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## fishbum (Aug 8, 2007)

man, I hate to burst your bubble, and I'm really not trying to be a jerk, but that bridge looks like it will last about two rides. Those skinny logs spanning that distance are sure to be bouncy, and that bounce will work all those nails/screws out in no time. I hate to see well intentioned effort go to waste, but we will see...


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## Bob W (Jul 6, 2004)

*Not the point*

Your wlecome. :madman: 
Its not the qualtity of the work I was commenting on. Its the material, specifically the diameter of the stringers used. And lack of support for them. Thats all, look a little lightweight if you ask me.

Bob W.


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## Jim Z in VT (Sep 9, 2007)

Looks like there's a couple diagonal braces at one end....maybe the old bridge can be sacrificed for a couple more. Mid span supports could be added when it starts sagging.

I think it's cool. I like scary bridges :thumbsup: 

JZ


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## cjohnson (Jul 14, 2004)

*wow.*

We'll have to take your word for it. Please post a monthly photo of it in this thread. Could be educational for us all.


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## Fattirewilly (Dec 10, 2001)

dubthang said:


> Thanks for the comments.
> 
> I am actually a well trained wood worker so the bridge is structurally sound. Everything that is round is notched into place, screwed and nailed. It is a very solid structure. The wood is a mix of biked in planks, and harvested timber. I left larger gaps (6" - 7") between the planks to raise the tech of riding the bridge.


Echoing what BOBW is saying. The stringers for that span look small. They also don't appear to be of rot resistant material. Then the spacing between the stringers on the deck boards (1 x 6 decking?) look to be too wide, ie they need more support in the middle. The stringers could be closer together to provide that.

Really 1 x 6 has little place on trail bridges. The life span is too short, a heavy jogger putting a foot through..... The decking should be 2" thick.

This trail is likely on your personal property. I'm guilty using what I have sitting around (ie 1 x 6 decking) on my own personal property. I just don't see this structure cutting the muster on something open to the public.

Heres a great link for a primer on bridge design

http://www.imba.com/resources/trail_building/index.html (scroll down to)
Standard Details of Pre-Engineered Bridges For Mountain Bike Trails 
-- Engineered by Jon Waldo, P. E. Jonesborough, TN


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## ajd245246 (Sep 1, 2008)

Usually pieces that are not touching the ground will tend to rot way more slowly, so in this case i think the bridge will last longer than everyone thinks....


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## dubthang (Apr 2, 2009)

The treads are reinforced underneath where needed. The bridge is quite triangulated too. It is also not for joggers. People on foot are more than welcome to cross it, but I feel that they will walk it or use the smaller bridge next to it. I do plan to add more treads on top of the current ones at some point. This area floods out in the Spring and during heavy Summer rains so it will need work from time to time. As for the branches, they have a minimum diameter of 3" at their smallest sections. Most are much bigger than this though. 

I do appreciate the feed back.

How is a spacing of 6" to great between treads? The average 26er has a contact patch of about 6" (depending on psi,) more when the tire curvature is considered. If all the treads are considered equal, the bike will apply the same force to each one regardless of their spacing. Too great of a space will allow for sideways forces to be applied, but they are not far enough apart for that. 

Thanks for the input.


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## nickcarll (Sep 4, 2007)

so man im gonna be honest we rode this today and on our way out it was quite scary but we manned up and rode it on our way out and it is really sweet! great work buddy


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## ajd245246 (Sep 1, 2008)

Fattirewilly said:


> Echoing what BOBW is saying. The stringers for that span look small. They also don't appear to be of rot resistant material. Then the spacing between the stringers on the deck boards (1 x 6 decking?) look to be too wide, ie they need more support in the middle. The stringers could be closer together to provide that.
> 
> Really 1 x 6 has little place on trail bridges. The life span is too short, a heavy jogger putting a foot through..... The decking should be 2" thick.
> 
> ...


Haha that link was already in my favorites


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## OGJON (Apr 15, 2009)

If it was me who had built this bridge I would have used 3 stringers for that width & had vertical supports 1 meter apart for the whole span of the bridge


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## dubthang (Apr 2, 2009)

OGJON said:



> If it was me who had built this bridge I would have used 3 stringers for that width & had vertical supports 1 meter apart for the whole span of the bridge


It's hard to build a three stringer using trunks because the treads won't lay perfectly flat across all three. I had to chisel in places to get the treads to lay flat in some places as it was. The bridge spans a water crossing so there can't be any more vertical supports because there isn't any firm ground to anchor them in.


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## dubthang (Apr 2, 2009)

nickcarll said:


> so man im gonna be honest we rode this today and on our way out it was quite scary but we manned up and rode it on our way out and it is really sweet! great work buddy


Thanks. It is really easy to ride once you just go for it. I have ridden it a bunch of times already. Just don't try to stop on it.


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## RussoJ (Jun 20, 2008)

dubthang said:


> Thanks. It is really easy to ride once you just go for it. I have ridden it a bunch of times already. Just don't try to stop on it.
> 
> Bridge was sweet today! Can't wait to get back out and ride it again.:thumbsup: You gonna be down for a ride this weekend?


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## zrm (Oct 11, 2006)

Looks very sketchy. Long span for those small diameter stringers. Can't tell from the photos what kind of foundation or sills the ends are anchored on, but if the stringers are just sitting in the dirt, they will shift and rot pretty quick depending on the local soil and climate.


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## ebxtreme (Jan 6, 2004)

Hey man....if this isn't seeing much traffic, then it should be fine. Granted, the size of the stringers are too small, IMO, and the rungs are spaced too far apart, but it's your call.

I'm in the PNW, so we're lucky that we've got tons of blowdown cedar laying around to use. As such, that's all we use in our laddering projects and every post and stringer is stripped of the bark. We also only use galvanized 8-12" spikes and I use 6" galvanized spirals for securing rungs.

My rule of thumb is to not use a stringer less than 6" in diameter at one end - 8" if it's longer than 12 feet long. My rungs tend to be 1.5 - 2" thick for durability/strength and spaces between 3/4 - 1". That gives them plenty of space to shed mud, leaves, debris, etc but enough space for doggies to walk on them and/or folks to put a food down without putting a foot through the rungs and breaking an ankle or leg.

A recent bridge we built. Span is about 50+ feet and it goes over a seasonal creek.

posts and stringers:









Post, cross beam and stringer close up:









Done:


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## bweide (Dec 27, 2004)

*1st Bridge Comment, 2nd Bridge Question*

First Bridge - Think about stripping the bark off all of the limbs before using them. Bark traps water which increases the rot factor.

Second Bridge - How deep do those posts go into the ground and how did you sink the holes, posthole digger? If it was a post hole digger, how did you transport it?


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## dubthang (Apr 2, 2009)

ebxtreme said:


> Hey man....if this isn't seeing much traffic, then it should be fine. Granted, the size of the stringers are too small, IMO, and the rungs are spaced too far apart, but it's your call.
> 
> I'm in the PNW, so we're lucky that we've got tons of blowdown cedar laying around to use. As such, that's all we use in our laddering projects and every post and stringer is stripped of the bark. We also only use galvanized 8-12" spikes and I use 6" galvanized spirals for securing rungs.
> 
> My rule of thumb is to not use a stringer less than 6" in diameter at one end - 8" if it's longer than 12 feet long. My rungs tend to be 1.5 - 2" thick for durability/strength and spaces between 3/4 - 1". That gives them plenty of space to shed mud, leaves, debris, etc but enough space for doggies to walk on them and/or folks to put a food down without putting a foot through the rungs and breaking an ankle or leg.


Nice pics, and good info. My stringers are all over 9" at their large ends. They do taper down though. Having tons of nice wood to choose from must be great. Unfortunately, I live in Maine. I think that I might try to throw up some pics of the other bridges/tech features on this trail because they are all made from small stock, and they have been around a long time. It'd be interesting to get outsiders' views on stuff that we ride everyday and deem 'safe.'


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## ajd245246 (Sep 1, 2008)

dubthang said:


> Nice pics, and good info. My stringers are all over 9" at their large ends. They do taper down though. Having tons of nice wood to choose from must be great. Unfortunately, I live in Maine. I think that I might try to throw up some pics of the other bridges/tech features on this trail because they are all made from small stock, and they have been around a long time. It'd be interesting to get outsiders' views on stuff that we ride everyday and deem 'safe.'


good idea, i'd love to see em' :thumbsup:


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## willtsmith_nwi (Jan 1, 1970)

OGJON said:


> If it was me who had built this bridge I would have used 3 stringers for that width & had vertical supports 1 meter apart for the whole span of the bridge


For decking boards .... 3 stringers would have been better. My group doesn't use decking boards. They've proved too unreliable. Our favorites for decking bridges are 2x8s and 2x12s.


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## hayseed (Sep 18, 2009)

Lucky Dawg! Cedar! Everywhere! And Big Cedar! Dont' go to Lowes or the sawmill, just pick up some huge, extremely rot resitant blow down and build away! I'm glad someone has it easy! LOL!


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## woodway (Dec 27, 2005)

Heres a bridge we built last February in cooperation with a local County Parks Department - it spans a flat area that is covered with about a foot of water in the winter time. *EBxtreme* knows where this is, as we are in the same neighborhood.

We salvaged downed fir for stringers, and peeled the bark off them to make them last longer. For bridge support, we elected to haul in concrete blocks, because if we used sleepers they would be sitting in water for half the year and we were worried about rot.










For decking, we found downed cedar and rough split it. It makes a great decking surface - it's grippy even when wet and lasts a long time.










The stringers and cross members are screwed together with 6" and 8" galvanized wood bolts. The decking is nailed with galvanized spiral nails.

This bridge get's a LOT of traffic - I just inspected it the other day and it's holding up very well. With the twists and rolls we put into it, it's a lot of fun to ride.


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## Joel. (Aug 16, 2009)

Wow, what a bridge! Fantastic work guys.


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## dubthang (Apr 2, 2009)

Woodway- nice bridge. How do you go about hauling in the stuff you need?


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## woodway (Dec 27, 2005)

dubthang said:


> Woodway- nice bridge. How do you go about hauling in the stuff you need?


We received permission from the Parks Department to use a ATV with a small cart attached to it to haul the concrete blocks (65lbs each) about a half-mile from the parking area up a main trail (wide, no problem getting an ATV up it) to the foot of the singletrack trail that the bridge was going onto. From there the blocks were moved onto wheelbarrows for a half-mile push to the bridge site. WOOF! Hard work.

The stringers were all salvaged from downed fir trees from the area maybe .5 miles around the bridge site, cut to rough length where they were found and hand (shoulder) carried to the bridge site where they were peeled and cut to final length.

The cedar was found all around the park, cut to width and split where we found it, then loaded onto wheelbarrows and pushed up the trails to the bridge site. Some of the cedar was wheeled from over a mile away.

Overall, a LOT of manual labor was involved, but the results were worth it!


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## dubthang (Apr 2, 2009)

Are the concrete blocks the typical open 'squared 8' ones, or are they a different style? I ask because concrete blocks are very weak, and are prone to failure from simple impacts. They gain their strength when they are filled with concrete, mortar, etc. If they were open, did you fill them?


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## woodway (Dec 27, 2005)

dubthang said:


> Are the concrete blocks the typical open 'squared 8' ones, or are they a different style? I ask because concrete blocks are very weak, and are prone to failure from simple impacts. They gain their strength when they are filled with concrete, mortar, etc. If they were open, did you fill them?


They look like this:










The bracket is galvanized. The block is solid concrete (which is why it weighs 65lbs). You could hit it with a sledgehammer and it would not break. I am willing to bet money that the wood will rot before the pier blocks crack or crumble  :thumbsup:


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## dubthang (Apr 2, 2009)

Nice blocks. They look pretty solid.


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## dubthang (Apr 2, 2009)

Shot a video of the trail bridges that this bridge is on. It is the first major bridge crossing. If you look closely, you can see that there is water right up to it unlike in the original photos. Some of the bridges are built a little better than the others, but we ride them all.

http://forums.mtbr.com/showthread.php?p=6212839#post6212839


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## Trail Ninja (Sep 25, 2008)

dubthang said:


> Shot a video of the trail bridges that this bridge is on. It is the first major bridge crossing. If you look closely, you can see that there is water right up to it unlike in the original photos. Some of the bridges are built a little better than the others, but we ride them all.
> 
> http://forums.mtbr.com/showthread.php?p=6212839#post6212839


OK, That settles it. I have to outweigh you by 40 pounds and my bike is probably 20 pounds heavier than yours. I'd never ride that bridge. I'll walk through the creek.


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## dubthang (Apr 2, 2009)

Trail Ninja said:


> OK, That settles it. I have to outweigh you by 40 pounds and my bike is probably 20 pounds heavier than yours. I'd never ride that bridge. I'll walk through the creek.


You ride a 49# bike? Seriously though, that's cool if you wouldn't try it, it's your choice. The 'creek' is currently neck deep with super cold water (this is Maine) so I wouldn't want to take a swim myself. There is an older gent that probably weighs in at 190 who rides an old Huffy over this thing several times a week.


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## Trail Ninja (Sep 25, 2008)

No offense intended. I was actually impressed with how well the bridge worked. 

I guessed your bike at about 25#. All together I'm about 270# when I ride if I'm not carrying building tools. Light weight bridges scare me.

I have the luxury of having big red cedar trees to build with so I'm kind of spoiled in that regard. I'm on Vancouver Island. The water here is cold too. It's all glacier fed.


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## dubthang (Apr 2, 2009)

No offense was taken. My bike is around 29# so total weight is generally around 185. I completely understand the differences between here (New England) and the PNW. We have small trees to work with, and generally build for tight single track type trails. I'd love to build larger, more robust structures, but it can be hard getting volunteers and funds. I think the video is a cool way to show the differences between New England and other parts of the country, and I love feedback, positive or negative.


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## jdog (Oct 7, 2005)

*NJ Bridge*

After I got permission from my land manager, I worked this week on replacing a low, bouncy bridge.

I used 2 red cedar logs to span the gap.

At the downhill end I sunk 2 4x4 posts into the ground and cemented them in place.

At the high end I used the stumps of the trees that I took down to secure the runners.

I used 1/2" galvanized hardware to fasten the whole thing together.

It bounced just a tiny bit so I added two angular support braces at the high side to solidify the span.

The decking is treated 2 x 6.


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## jkmacman (Mar 5, 2009)

hey jersey:

nice work on the bridge, where's the trail at? i want to check it out.

btw: helmets are cool


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