Friday, March 26, 2010

#001 07 Clear Creek Timber Howe Truss Bridge - The Drawings

As I'm doing this one I thought I'd blog about HOW I do a project, from beginning to end.  Magazine articles generally can't cover 100% of a project because it would turn into a book.  Since I'm still sick with bronchitis the only thing I can do is write... here we go.

Step 1.  What do I want to build? 

I know I want to build a bridge.  While I need it for my AP Structures list, I also like wooden bridges and have always wanted to build one.  So this project is a wooden bridge.

Step 2.  What kind of bridge?

The bridge has to be something interesting and challenging, otherwise I'll lose interest and it will never be completed.  It also has to be able of scoring 87.5 points for an AP Merit Award in an NMRA judging.  This means it has to be rather complex.  A trestle might accomplish this, but I've built lots of trestles.  I need something more difficult.

Step 3.  Search for a prototype.

All modeling should start with the prototype.  Many models that I have seen have been built from seeing other models!  While I'm all for freelancing and imagination, to really score Merit Award points you should pick a good prototype.  To me, reproducing something that exists (existed) is the most challenging of all.

Having a good home library of railroad books is a blessing.  I have a library room with four large bookcases fill with train books, a comfy leather chair and a good light.  A large stack of books will be pulled off the shelf and I'll start looking at pictures.  For a bridge with a lot of character I often turn to the narrow gauge railroads who often had to build with what they had.  One of my favorite books is Up Clear Creek on the Narrow Gauge by Harry Brunk, a professional illustrator and artist.  His sketches are fantastic and he is a model builder, so the information for modeling is usually all there.

While browsing through the book (it is actually a lengthy collection of his famous magazine articles) I found just the bridge I'm looking for.  The Colorado & Southern Railroad had a wooden (timber) Howe truss bridge spanning Clear Creek in the Clear Creek Canyon.  See the picture below.

Step 4.  Evaluate the Prototype as a Model

Now that I might have a prototype I give it the acid test, which is a battery of questions in order to decide if I'm going to build it or not.

A.  Do I like it enough to spend hours constructing it?  Yes.  While it is complex looking, it is more repetitive than difficult.  It is attractive and interesting.

B.  Can I use it on my layout?  Yes.  Generally I don't build things that I can't use on my layout.  I used to build structures for pay and put myself through school doing it, but no longer.  Each piece that I construct has to be either for the layout or to build my skills for a bigger project in the near future.

C.  Can I build it?  Yes.  This is the real test.  Is my ego bigger than my skills?  In this case no, so I have a good chance at success.  There are a lot of pieces, but not anything requiring skills I don't have.  I did find on line other modelers that successfully built this bridge, which is another indicator of success.

D.  Do I have enough information?  Yes.  This is something I always ask.  Sometimes one photo is enough.  This one is a little more difficult.  While Harry gave us some nice drawings, they are NOT plans, which is different.  Some of the key dimensions are unknown, such as the length and height of the bridge.  Harry even admits that if you want a more accurate bridge, you may have to go back to the photos.  My next step is to jump on the computer.  A few hours later I had more photographs and several shots of models of the bridge.  I even conversed with a fellow in the UK that built one and got some pointers from him.  The last step is to send off a request to the NMRA's Kalmbach Library for which I was rewarded with five pages of photos.  Yes, we can make drawings from this.

E.  Can I make a good set of construction drawings?  Yes.  I'm not talking magazine drawings but construction drawings.  These will allow me to cut materials accurately and assemble them in the proper fashion.  They can be as simple as graph paper sketchs or as complex as 3-D cad drawings.  In this case I need the extra points and will produce a set of 2-D Cad drawings.

F.  Are the materials needed readily available?  Yes.  Simple wood timbers and nut-bolt-washer castings, along with turnbuckles and wire.  All available by scratch or the local hobby shop, which is Trainmaster Models.

G.  Can I afford to build it?  Yes.  This is a VERY important question.  When you look at a kit vs. a stractbuilt project you often THINK that scratchbuilding is cheaper.  This is not the case in most projects.  A buck here, a buck there really adds up.  In this case I ran the numbers and don't believe that the cost will exceed $30.  Details are what you have to watch!

H.  How much time will it take?  20 hours.  Wow!  Really?  Actually it will take more than that.  For instance, just doing the research I've spent 5 hours and haven't even gotten a good start on the drawings.  Do I care?  No, but there are opportunity costs.  If I'm building this, I'm not building something else.

I.  What skills will I develop or learn?  Precision.  This is always good to ask yourself.  Every model should be a challenge in some way or other.  For this one I am trying to develop a higher level of precision.  Attention to the fine details is important as I progress on to more and more difficult projects.  The drilling of holes and making the angled supports uniformly straight is tricky, and may require the use of jigs for a higher level of precision.

With all those questions answered in a positive light, time to move on to the next step.

Step 5. Analyze the Prototype.  I've gotten the photos, sketches and documents related to the bridge.  I'm still missing some precise measurements, but we'll extrapolate them from the photos.  With large printouts of each document I carefully scan the model.  Using MS Word I've started a document to capture information.  That board is crooked, that board is broken, there are four bolts on this side, etc.  One thing I really noticed was the bridge foundation as one side is concrete and the other is build of crossties.  One of the tricky things is NOT looking at someone else's model for prototype information.  Wolfgang built a nice model, but he did it from sketches, not drawings, and some things don't look right.  I'd like a more precise model so I'm going to have to throw Harry's beautiful sketches out the window and draw a set of plans.

Step 6.  Determine how to build the model.  This is the step where we sit back and go "if I were going to provide this to the public as a kit, what would the kit look like and how would I build it?"  This is a very important step as a mistake here can cost you time and materials.  Still, no matter how well you do, you won't be able to do this perfectly, so do wait for perfection.

For the bridge, I see it as several components.  Each side is a component, the bottom is a component, and the track and ties are one component.  So we are looking at four sub-assemblies.  If I build the bridge supports, that is five.  Great!  This tells us how to build it.  The sides are identical, so we can build them in tandem.  The ties/rail can be built separately and then added to the model at the end.  The toughest part will be the bridge base, which can't be done until the sides are ready.  Ok, so we build the sides, then the base, then the supports and then add the track.  

Step 7.  Evaluate Drawings.  What drawings do I need?  Well, they should match the components listed above.  We'll need a side drawing (top and side), a bridge base, a track drawing and then the supports (two since they are different).  We'll do these in Cad since we'll want to get AP Points and because I'd like to share them with people who might want other scales.

Step 8.  Begin the Drawings.  This is where we lose people.  The armchair guys never get past this point.  But we are.  I've begun the drawings on 3rd Plan It Cad.  Not the best in the world, but what I happen to have and know.  Like other things, there are several steps here.

A.  Determine the overall dimensions of the model.  This is a problem right off the bat as I don't have a full length or height dimension.  Will have to extrapolate it.  Harry Brunk's drawing appears to be roughly 1/8" to the foot.  That makes the bridge 66'.  I have a picture with a man standing on the bridge.  It scales out to about 50'.  Big difference.  I'll have to work on this.  I'm also having trouble determining the angle of the supports.


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