Monday, 22 August 2016

The Girder Bridge

A scratch-build showing the way i am constructing a girder bridge out of odd scrap`s of leftover paper card. Spanning a river this bridge with a rounded top  needs to be tough enough to take the riggers of strains and stresses just like a real bridge would that is made of concrete and steel. Two rails will race across the span of this project that really is costing nothing at all. All i need is to hand and so i intend to use it.    i can well imagine the sound of rattling trains being pulled along by puffing Engines full of playful smiles.                                                                                                                          

My first job of work was to design a paper card box, a Pattern with a straight back wall and slopping front and side walls this will be used to make the two concrete end walls.                                                                                     


No rubber molds this time,just a box of  inexpensive wet sand.
                                                                                                                                      
The Box Pattern





Reinforced with angled card and stuffed with a couple of sheets of kitchen paper. Yes very crude but this will prevent the sides from being pushed in.   No ramming up needed.
Wet sand was placed into the oblong box and bumped up and down in rapid movement on my work table,and the Pattern that simple little box was wriggled to create a good flat bottom of sand. Next the wet sand was spooned into the odd plastic molding box,and bumped and thudded,thud thud upon my table top.



The wet kiln dried sand,is a very fine sand like that found upon the beach at the sea-side,and the work was very quick to do,and with the last of the sand compacted by hand.

 
"Wet & Dried ! A contradiction in a sentence that makes sense,
and that is in English an Oxymoron  BB."                                



                      "Smart Alec Bookworm`s been  munching on BB`s rare books again."




                                  The little paper card box needed taking out carefully.


                             A simple wriggle and the crude Pattern came  out easily.


The Plaster of Paris pour,and the first one of two needed was done but not dusted.



Now the sand will suck up a little of  the water in the plaster,causing the top to be drawn down.


This sagging was to be expected and it was refilled using the same mix of plaster. So the correct size was maintained.



 My old butter knife went into action 20 minutes later,and a very sanded casting was put aside to dry.



Soon, as easy as before,both sat side by side smiling at each other,and certainly the planned river will add reflection to them. They will take a few days to dry out.

"The camera makes them look huge."

So  now the design of the one foot long bridge was penned out upon paper card ,and once cut out,that became my Template.                                                                                                                                


"So no need to measure out again."   
                                                                 


Two more skirted around with a pen and there they are back to back upon a scrap piece of paper card.


Very soon all four needed were cut from the card,and the inner shapes within sliced carefully out.

When building anything like this think Engineering and reason each stage of construction out with a mindset question of ," how do i strengthen a paper card bridge,and make it fit for purpose?" 
This question also applies to metal,plastic or even wood models.                                                                                                         


This work is the same as constructing girders. both sides that will form the bridge and its shape  are laid face down while certain girders are reinforced with a center spine of same thin paper card.
So each side will thus be double sided,and with the concrete end walls set out they will span comfy like,strong and reliable.     More Reinforcing work to do later.

                                       As Work is Still Ongoing There Will Be an Update Soon

                                                 
                                                             Thanks for looking. BB

UPDATE!

With the inner reinforcements cut and stuck into place it was now painted before sticking the other side on.This is easier to do,rather than later because its a bit like painting trellis and having to get the brush into the tiny gaps that will be between both the sides.


     Only the inner side of both were painted,but not their other side. When closed and stuck together the black will well define a thin inner shadow line which will be more pleasing to the cameras eye and hopefully mine too.


                                                   

                                                 
                                                                 "It sure looks black."


                                                " Yip! BB,bought a few cans going cheap."
                                             
                                                              "Y were they going cheap?"

                                                     

                                                    "They had WHITE printed on the cans!"





                                                 PEELING OFF THE OUTER SIDES



This will leave a rough edge to the metal girders that will give good effect when dry brushing at a later stage. It also allows the paint to soak into the paper which stiffens when dry.

                                                        "Makes sense ta me Pards!"




                          " Ur,what if one did not wish to peel that stuff off,could it stay?"


                                                                      Comparision

"Of course the facing paper could and can stay on it`s a small matter of choice. "


"Ya, and even paint e`m white by buying BLACK cans!"




 Marked out with line and large bracket plates cut to size and facing paper peeled off.

                                     
                               


Plenty of glue where the glue should be.


"i`mmm that looks a lot."


 All the largest Bracket Plates have been placed on top of the glue and left for 10 minutes,before a heavy book is placed on top. This avoids parts skidding out of line. Thin lengths of reinforcement strips will eventually be stuck into place on the marked out lines,and will butt up against the Bracket Plates and not under them.
                                                             "Ya,that makes sense."

                                                              "i`mmm,it_____ does?"
                                                 

                                             Smaller Bracket Plates drawn out in ruff rough design.
                                         
                                                 
                                                                       
                                                                       


                         Thin reinforcements need the facing paper peeled and pulled off.


"BB`s ,sure going all out for that good decaying rust look."



Made longer than is required makes painting much more easier the case being the finger and thumb have their very own space.                                                                                                                



"i`mmm Mrs B,found a crystal ball on her dog walk." 

   Now there`s a first for me,a tidy mess upon my new table.  If i were to tidy mess all my larger work tables others would think us quite Posh,and me quite sane!                                                                            


                                               
The inner sides with the Facing Paper still attached of the other two bridge sides were painted,so now all the inside on each cutout is finished. When dry later they will be turned over and marked out
and the Bracket Plates will be stuck on in the same way seen as described above.


After marking out a strip,i put a new blade in my craft-knife,and cut out the other brackets one after the other. A very quick way.
                                                                                                     
                                           
                                                 
                                                         There will be another update soon.

                                                                             
                                                                              BB

 Time for having sticky black hands is near over as i finish this last little piece.
It is enamel paint,but does a perfect job of stiffening paper card. Messy smelly but the best.



The following morning it was time to glue the sides together with a good measure of glue.


                                   "Ha Ha! To much Glue."_____ " NO,theres Not!
                                               "Yes There IS!" _____ " BB,Said Theres just Enough!
                                    "i Don`t CareWhat BB ,Said!"____ "Righty O`, i`m Off Home!"


"i`mmmm.It is aloud to laugh or even smile at least for such a little small while."


           All worked out fine and the double sided girder bridge will dry out a treat,it being very strong.


It will be even be stronger still after the bottom and the top outside edge has had a girder
strip added upon its entire length.
                                                            "BB,Believes in Strong!"


The very thin reinforcement stripes i glued up inside have made each side much stronger and all the Plate Brackets just like a real bridge have given each girder upright or angled extra strength. There will a fixing Bracket for the bridge to sit a rest upon which in turn is bolted to the End Walls which were the very first things cast up especially for this railway bridge to span.

 
"Yah, Whoo!We are working on the rail road all the live long day,We are__"

Now`s the time to turn attention to the river base that those end walls will rest upon with their feet cooling off in the water.
                                                     
                                                   "Perhaps we could have a paddle too."


Here it is the very deep but dry riverbed the old rustic bridge will lump its heavy iron across with that very first thud upon its very first day.

                                                   "It sure it`s going to be deep so no paddling!"


Here we are with the castings drying out nice in the late summers warmth,and so its time to open the sluice gates of old Hellesden Water Mill, two mile or more upriver,and wash along a good strong streaming flow enough to fill this river bed up. Well at least try to make it pop with a certain kind of Mod Podge wetness with a few marginal plants.


Hellesden Mill 1910

"The Old Mill is nearly three miles away if one measure out well the bends in the River Wensum ."
                                                 
                                                               "Gee Thanks Bookworm."
                                                       
                                    "Slurp! Slurp!There Will Be Another Mod Podge Update Soon BB"



                                  A Simple Way to Mark Out Thin Width Strips Of Card

i must just mention that i having been doing this for many years.
No not making bridges but marking out the edge of card for thin width strips,like for houses and boats or whatever else i needed at one particular time.


Holding my finger against the back of the board ,while holding the pen to the width of the card i have my measurement i wish to mark out.


Then still holding the pen set in that place ,i allow my finger to be the guide  along the edge of the board and simply run my hand finger thumb and pen along the edge which easily gets my mark. Thin strips can get awfully tedious marking and cutting out always using the ruler. However i enjoy doing it quickly but methodically this old way. Because i am working with paper card i brush p v a glue onto the edge of the card before cutting out. This prevents the paper layers splitting and coming apart. So i mark out, glue,and then cut out in that order. Once i have strip i brush glue along the edge i just cut off. Then mark out the next strip needed.



Well this is just a tip that works for me,and took the boredom out of marking out the 12 i needed for reinforcement strips on the outside of the bridge.  Did it save much time? Not really that much ,but folks its my fun way of enjoying doing repetitive stuff over and over.                                                                                                               

                                       Thanks for looking BB                           

UPDATE

A Change of Plans

The good thing about scratch building stuff is if things look odd out of place clumsy one can easily go on to Plan B. In this case  i wanted to slim down the end walls of this girder bridge,and reduce their height, and so i dumped the first ones into the landfill bin,and then designed another pattern by using some scraps of styrene.                                                                                                             
As i hardly throw anything away  it was easy to find a 7"x 6"  board and i traced out the required shapes,and cut them, out.                                                                                                                   
   i then pinned the four sides together with dress makers pins put in at differing angles which soon locked tight the little box and made it square enough to proceed.                                                      
These pins are very cheap and well worth having in any model makers stash of useful things,along with the good old tried and tested sellotape which in this case was stuck and wound around the little open ended core box pattern.                                                                                                                     
     
Then i placed it upon glass and gently packed fairly loose sand around it just make double sure the     pressure of filling it with Plaster of Paris did not  bow the sides out under pressure of pouring it.          
So the sand was not pushed in to hard because that would push the sides in.  It was just gently fingered into place,and then the thing that took all of 2 minutes to make was ready for its first pour.
So yes carefully taken apart later ment i couuld use it again.   That was Plan B.                                                                                       


The little box filled up nicely with no more trouble than spilling a couple of drops on the sand.
Sand i find to be most useful too,to have in ones modeling stash! This is Kiln Dried Sand whitch was still damp from making my first castings a few weeks ago.So it was perfect to use.





The End Walls came out fine,and being now reduced by third  in width,and shorter by three quarters of an inch they will look much better when fixed into place on the section of the  River Wensum below.i`m more than satisfied how the, (1mm thick) ,water turned out,a something way out of my comfort zone a few weeks ago. Now i can work on the river banks,  as well as working on the bridge itself. Riveting to do next,then reinforcement strip to fix into place,then the odds and ends leading to the final finish.


                                         What with doing extra work and now on plan B,
                                          i`m quite pleased that common sense prevailed once more,
Relieved that it turned out well,                            
i sat down to a nice Sunday Tea,with my Mrs B.    
                           
                                                                 Thanks for Looking BB
   

2 comments:

  1. Fantastic and creative...Well done BB!

    ReplyDelete
  2. Hi Phil,thank you for commenting. There is ongoing work to finish and bring this topic to an end. BB

    ReplyDelete