Now for the Howe truss structure…

There are several types of covered bridge super structures used in railroad covered bridges and vehicle covered bridges. The most common railroad trusses in the New England area, in no particular order, are the Howe Truss (Clark/Pinsley), The Burr Arch Truss, Town's lattice truss, and the Pratt truss. There is a GREAT article about the many truss structures at the Wikipedia site (for Wikipedia): http://en.wikipedia.org/wiki/Truss_bridge


Why is this important? The trusses are all unique in how they transfer weight and their construction, how much they can hold, and the max useful length. Yes there is the tension and compression and all the formulas and scientific engineering degree talk stuff… But more that that, each one has a remarkable structure of it’s own! It will also dictate how your diagonal members are set up and look.

Check out the few different ones in this picture posted here:



www.uvm.edu/coveredbridges/conference/2003.html


Anyway here is how I set up the superstructure.

Remember the width of the 1/2” runners on the floor? Well that comes into play now as they are the base of your diagonal members. With a Howe Truss all the main beams lean towards the center of the bridge with minor supports leaning opposite. So I made an X with 2 1/8 x 1/4 as support beams and 1 1/4 x 1/4” stick as main beams, which sets perfectly on your runners. You use a WAG to figure out how many trusses you’ll need for your entire structure. The inside of mine is 16” so I divided that by 4 and that’s how I came up with the 4 4" trusses that I have.

This is where my Geometry teacher would be proud of me.[:-graduate]

To get your angles remember all angles of a triangle add up to 180 degrees.



So if you find an angle you can get all the rest of the angles from there… And remember there are 180 degrees in a line.

Then measure the length of the truss from there, remember to account for the size of the stick you are using.

Now for the hard part...[xx(]

Cut your timbers. If you did your measurements right both the support beams and main beams will be the exact same size. I was cutting all of these with an X-acto saw blade (time consuming!) Get an adjustable miter saw it will save you hours!

[:-bulb]Hint: to save me time and get these as close to the exact same size as I could I cut the first beam and got it to fit exactly how it needed to be. Then I simply copied that one, angles and length.




Set the length of your craftsman’s square to the length of your timber. Then I use the craftsman’s square to find center on the outside beam. At the same time I cleaned up my angles and made them the same size with my Dremel and a sanding bit.





Next set up beams as they will be in the truss, drill a pilot hole into the center of the support beams and insert a nail. You should be able to open them up and make a perfect X.





[:-bulb]Hint: Place a piece of 1/4 x 1/4 stick in between the support beams and secure with a cloths pin. This will make it FAR easier to place your truss into the runners.



Install all of your trusses onto your runners getting as close to the marks as possible.

Once your Elmer’s dries, drill your truss rod holes and insert music wire through top and bottom runners.

[:-bulb]Hint: here I used a 5/64 drill bit for the .078 music wire. I still had to tap it into place with a hammer.

And there you have a Howe truss. Here is what mine looks like when finished:



If you have kids you could slide this on past the wife as a school science project. Sorry I was kidding about this being the hard part!

Thanks Mike! It sounds like your friend has more patients than most!!! I thought folks would like to see my screw-up's as well as my successes on the way to my outcome, that I feel proud of. Maybe it will keep them from getting too frustrated when things do turn out like they'd like... :erm:

I read on this forum some where that you have to be willing to experiment and fail to get things the way you want them. And that is exactly how I muttled through my first building.

:erm:

Great tutorial, Dan. Thanks so much for the hints. I had a friend leave some wood outdoors for over a year just so that it would weather nicely and achieve the effect he wanted. I surprised him by attaining the same effect in just a few minutes at the workbench!

Something I thought I would point out before moving on: When I was doing the weathering I used well thinned out Testors Model Master’s flat white. No recipe, just so that the white covers the wood lightly. This made it go further for one and I also found that in brought out more of the wood grain and flaws. It helped make it look more like rough cut wood than engineered wood.

I then did several coats of the alcohol with black India ink until it had the appearance I liked… When it was dry.

Hint 1: If you lightly scrub the white coat with your brush and your India Ink mixture on it, it will pull up the white and helps make a randomness to the weathering and gets more black soaked into the wood.

Hint 2: Until you get used to the shades of the ink when you are putting them on; remember that it looks WAY darker when it is wet. You should always go with the grain too. You will leave streaks otherwise. If you have a dark spot you can lighten it up a bit if you re-wet it with some alcohol and your brush. This wont perform miracles but you may fix an oops! Without sanding.

After the floor/rails I constructed the inside roof structure. I decided to go this way so that it would help give reference to make sure the walls were square.

Before I had found a picture of the inside of the Clark/Pinsley Bridge:



I went off of memory and pictures of other bridges, for what it looked like. So I used 1/2 X 1/4” stick for the sides. This will come into play later when you build the wall structure. I used 1/4 X 1/4” stick for the joists. I then used safety wire to run across them like this:



Well as you can see it didn’t come out as well as I’d hoped!

Then I found the above picture… So I removed the joists and gave them a 45 degree cut and two short ones to complete the cross members. Then used some .078 music wire found at the local hobby store to run across between the cross members.



This what it ended up looking like:

Thanks Mike

I have poured over this forum for a few months in my spare time and haven't seen anyone doing a covered bridge. So I thought that showing my work may help someone else who wanted to.

I grew up in New England area and my Grandparents were the owners of the Williamstown Vermont Railroad depot when the Central Vermont closed the branch line in around 1936. This is going to be my next structure, as it was between 1888 and 1936 to include the turntable. I have been interrogating my Mom for what she remembers of playing on the abandoned turntable pit. And what was still there when she was a kid to help me get a visual of what time is slowly erasing.

Hi Dan, First of all, welcome to the forum and it's great to see you diving in already! I've always loved looking at pictures of that bridge. It appears in many of the New England books and magazines I own. One of my friends up here in Ottawa models the C&C. I have a 44-tonner that my friend painted in Pinsley colours for me. Thanks for creating this thread. :up: :up:

Thanks Jerry!

I am going to make granite abutments for it next. I have some ideas on the granite abutments but I want to test my theorys before I post them incase they absolutely don't work.

Welcome Dan great looking bridge.

Jerry

I apologize for the backtracking and my confusion… I used the wrong link for posting

Here is a background on my first scratch built model structure. As I am new to model railroading I used this forum a lot for how-too’s and ideas. I thought that I would give back to those that gave me all the help and I wanted to say thank you!


My structure is the Clark/Pinsley Covered Bridge. It was built in 1904 on the Barre Chelsea Railroad over the Winooski River, between Barre and Montpellier Vermont. It was then moved to Clark’s Trading Post in Woodstock New Hampshire where it is still used as a tourist railroad.

Here is the a reference web page : http://www.vermontbridges.com/cbmail.bag.htm


The actual bridge is The bridge is 116'0" long with a clear span of 107'0". It has an overall width of 21'6" and a railway width of 14'8" and a maximum vertical clearance of 20'6" However I didn’t want the bridge being my layout so I scaled it back to 17” O scale or 68’.

http://www.nh.gov/nhdhr/bridges/p107.html

As I went along I took pictures to help you out with Ideas. But as time started to mount I forgot to take them. So if there is a spot that you’d like me to recreate and take some I’d be happy to.

Here is the original bridge:



And here is my bridge:

Sorry Dutchman I got your email but somehow deleated your post and my original Post... I'll get this program down I guess It'll just take some getting used to.

Thanks for the help... I just over wrote my original I think.

Welcome to Railroad-Line, Dan. We'd love to see your bridge. Unfortunately, your photo cannot be viewed because of the parentheses in the file name. If you rename the file to eliminate the ( ) marks and upload it again, everything should be okay. For future reference, the forum software allows only alphanumeric characters in file names uploaded to the server. Punctuation marks, symbols, and other 'characters' are considered "illegal' by the software.