I took note this hasn't been brought up .... how common are straight sided mid-supports ? I was always under the assumption that all four sides normally had an outwards taper from top to bottom on free standing piers (?)
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
You don't mention, but did you figure the height and notch the wood block for the bridge shoes? I will always use a 1x wood "sub" abutment and notch for the shoe shelf. Some portions of the wood are carved, scribed and treated as you are doing. The bulk of the face, sides or wings are done with dyed hydrocal castings.
This one is in the fitting stage in the pic. It has since been completed- No pic yet-
The upper face of the notch is fitted w/ a thin stripwood and brought up under the rails for a ballast stop.
The sub abutment and shoes can be seen better in this pic
The end cut of the wood spline will get the facing/ ballast stop also. The 1/4" Hydrocal castings will be horizontally scribed @ 24-30" forms. These can be laid into my form for the plaster pour.
These type of forms are easy to make. A sheet of acrylic w/ 1/4" styrene hot glued The dams are adjusted to any detail laid on the base. The stepping can be seen in the first pic. This was done this way.
Other abutments and piers have be built up with strips of plater to simulate cut stone. This pier was done this way, may treat one of the abutments the same.
The idea mentioned of denting those form lines is very good. If you need to a slight scribe at the dent line may make it more pronounced. Although the normal sizes of forming timber or actual forms (newer) would be 8-12" for timber and 24-30" for plywood, you generally have to use some modeler's license and make the form lines much larger as not to look too busy.
It would be rare that a full 4x8 panel wood be used on a huge pour such as an abutment. The force on the large panel from the pour could cause major blowouts. All the added wales and studding couldn't hold the form under that kind of pressure. Large modern pours are explained by concretelakey
Modeling B&O- Chessie Bob K. www.ssmrc.org
I agree with the others in the statement of "what era" AND also how true you wish to be to that era. I beleive that many early concrete forms were of a stacked plank design that would show a line about every 8" to 10".
Most modern abutments are done using stackable steel form available in 12" width increments (12"/24"/36"/48"/72"/96") and in lengths ranging 8' to 20'. They simply select the combination of widths needed to obtain the height needed and bolt them together.
In addition, depending on design criteria the pour lift (the height of each concrete pour) would most likely fall in the 3' to 5' range. So for this they would form to a height that corresponds with the designed lift, pour that section and let it reach its initail cure, build the next lift and pour, etc....
I think the forms used would have depended on the location, date, and availability of materials. I've seen some concrete abutments here in the wild west where plywood was not available when they were poured. Whatever the railroad had on hand would have been used, with most of it probably being rough cut lumber in the mid- to late 1800's.
Depends whether they used lumber or plywood to form the abutment. 2x8 would be a common framing size. You could even use a regangulr piece of steel and put some "dents" in the wood to simulate form boards. Take a steel mending plate, put the end on the abutment and push or gently rap the end of the plate into the wood.
Another material that can be used is sheetrock, put two pieces back to back, It can easily (if a bit messy) be tapered and can be chipped to reflect weathering and spalling.
It can also be carvedd to represent stone.
Dave H.
Dave H. Painted side goes up. My website : wnbranch.com
I am building a new HO layout (early-to-mid 1980's time period) and will be using an Atlas #593 through-truss bridge with an Atlas #590 Warren truss bridge to span an up-and-over segment. Since the two bridges needed to be joined on a stepped bridge pier and I can't find a viable commercial product, I decided to scratch-build the pier and two abutments. They are 3-1/2" high x 3-3/8" wide (25-1/2 x 24-3/4 scale feet). I made them from 1x4 pine, sanded them smooth, painted them with rattle-can gray auto primer, sanded them again to totally elminate any visible wood grain, and gave them a final coat of gray primer. To simulate poured concrete, I plan to spray them with Floquil concrete and dust them with a fine dusting of Ultracal for texture while the paint is still wet. I will then give them a final spray of Floquil concrete. Before I spray the final coat of paint I was thinking that I should scribe some lines to simulate the layers between concrete pours.
What would be the correct scale distance between scribed line? Is this even necessary?