Wills varigirder bridge

[Ray H]

I need a bridge to span three tracks on the skew and have to add another three plain panels - to make eleven in total - to the Wills varigirder bridge to facilitate this.

 

The instructions with the kit show the top and bottom flanges covered by splice plates. I presume that the splice plates go in the centre of the bridge with the standard (8 panel) bridge. What happens with the splice plate with a version of the bridge extended by about 40%? Is the splice plate lengthened or are there two (or even a top splice plate that holds the two splice plates in the layer below together in much the same way that the single splice plate holds the two flange plates together.

 

The bridge carries an access road. The few bridges that I've looked at, either in pictures or on site, appear to have a form of ribbed steel under belly. Is there anything readily available to simulate this or is it simply a case of fixing strips of plastic to the underside of the bridge deck to represent the ribs? Does any know what width the ribs are and the size of the gap between each rib (if there's such thing as a standard set of sizes?

 

Presumably the deck effectively rests on the lip at the bottom of each plate.

[PhilJ W]

On my layout I have a bridge spanning 5 tracks made from the Wills vari-girder. I have not used the splice plates as I have used  a piece of 12 mm ply for the bridge deck and have placed the top of the girders flush with the top of the deck and topped it with the Wills brick walling (the walling the same as that over the Wills brick arches) the effect is of the bridge structure being hidden by the girder plates.

[allan downes]

Google - plate girder bridge construction.

 

Girder bridges on steroids.

 

Allan.

[Neilgue]

Google - plate girder bridge construction.

 

Girder bridges on steroids.

 

Allan.

When you clock the image tag, half the pictures are of models...

[Ray H]

Many thanks.

 

Interestingly using the same search terminology (cut and past from the above post) I got two substantially different search results a couple of days apart.

 

Equally interesting is the apparently different positions of the bridge floor relative to the sides. Luckily there's one picture of a British (railway) bridge over water that to my untrained eye looks very similar to the Wills kit sides and the base appears to be at the bottom of the sides. As my bridge is only a (road) track access to a lightly used goods yard I think I can get away with what I'm planning.

 

I'm currently aiming to have the bridge surface wide enough for two lorries to pass on the bridge but wonder whether given the length of the span that is otherwise unsupported, it might be better to limit the width to just allow a single vehicle on the bridge at a time or to narrow it just slightly, still allowing two cars to pass but not two lorries. Thoughts please.

[rovex]

My only concern with the wills kits, is that modellers do tend to use them to make a bridges of very long length without any kind of intermediate support.

 

After a certain length, given the limited depth of the sections the bridge would collapse under its own weight, unless some kind of intermediate support was used.

 

Dean

[Ray H]

I must admit that I did wonder about that. I've had to add three panels to the bridge in order to span the three tracks and as there is a three way point underneath there's no room for any additional support.

 

The only thing I can think of is to add a beam below the panels but I don't want to increase the bridge height too much as that would impact up the access to the goods yard.

 

 

The hastily knocked up picture shows the problem. The left most rail track in the foreground leads to the goods yard and the road/track from the left hand side of the bridge, which is only there to provide access to the yard, turns and drops down to baseboard level which it reaches within about 45ft. At present the underside of the bridge is about 18ft above rail level so could be lowered perhaps to 16ft to ease the angle of the slope.

 

I can't straighten the alignment of the bridge to reduce its length because the signal box is immediately the other side of the bridge on the left hand side and moving the right hand side of the bridge squarer will defeat the object as the right most track curves further right as shown.

 

The bridge is probably at the narrowest part of the layout as it is.

[rovex]

As you've mocked it up you've got plenty of head room below the bridge.

 

You could add a beam below, set back a little with little pieces of plasticard cut into triangles to tie the beam to the wills girders.

 

The whole resting on slightly lower abutments. I did a similar thing with the Peco girder bridge like this

 

[Pete 75C]

Ray - it looks fine to me. But the important question (and the only one that really matters) is does it look alright to you? Maybe an engineer will tell you the bridge span is a little wide to be unsupported, but compromise is something railway modellers should be used to. Again, I think it looks great.

[Ray H]

As you've mocked it up you've got plenty of head room below the bridge.

 

You could add a beam below, set back a little with little pieces of plasticard cut into triangles to tie the beam to the wills girders.

 

The whole resting on slightly lower abutments. I did a similar thing with the Peco girder bridge like this

 

model1 (11).JPG

 

That was something along the lines of what I was thinking about save that my thought was for a solid I beam beneath the panels. However, what you've done has a bit more class to it!

[andytrains]

Here are a couple of pictures of my bridge on my layout Yoker.

The first shows the support I made in the middle of the bridge. Made out of some plastic pillars that I think were originally Hornby or Triang bridge supports, (grey plastic), with diaganal girders from L section plasticard and larger I section above, (white plastic).

The second picture shows the girder made from the Wills Vari-girder in place.

Hope this helps.

 

Here is a picture of the real bridge actually had five tracks below and two centre supports. I have not got room to model the whole bridge so have only done the track on the right and the next one to it.

 

Edited February 4, 2014 by andytrains

[bécasse]

Judging by the depth of the main girders in the bridge at Yoker, it was probably built without any intermediate supports (as a very rough guide, the depth of the girders has to increase in proportion to the length of the unsupported span). The addition of the supports probably reflects the need for the bridge to carry heavier loads than it was designed for, but may have been a reaction to some weakness that was detected in the girders. With the space under the bridge little used these days, providing the supports would have been much the cheapest way of strengthening the bridge other than filling it in.

[Sasquatch]

Two Wills vari girder packs came in very handy when making the three track skew bridge over Eller Beck on Goathland. 

The 2 middle spans were cut in half as the under side isn't visible.

The wider the span the deeper the H girders is the general rule. For a road over bridge of say16' the Knightwing H girders should have what you are looking for. 

 

 

[simonmcp]

Hi Guys,

 

Is the quoted length of 352mm for the entire length of girders, back to back, or for each side of a bridge with the girders back to back? Will it make a bridge 352 with both bridge sides having detail on both sides?

 

I am thinking of using these for both the sides of a traverser which is 289mm wide.

 

Simon

[Ray H]

Each panel is approximately 22mm sq. and there are 16 panels in each pack.

 

They suggest that the panels are glued back to back so you can either have 2 lengths x 4 pieces (on each side of the length) or 1 piece of 8 pieces.

[simonmcp]

_{Hello Ray,}

 

_{Thanks for the information. Looks like I will have to make up 'welded' sides instead.}

 

_{I got a  Walthers Cornerstone traverser on that well known auction site but the traverser deck is very narrow and not very prototypical for Swiss, which is where the layout will be based.}

 

_Simon

[Sasquatch]

32 panels per pack, 8 of which  are end panels with the half brace!

[trainman6555]

Hi, a little bump here!

Just a note, the skew bridge 100 yards from my house in Derby, on Stenson Road, if you want to google it, has 20 panels per side, used to cross 4 tracks and has NO additional support. It has large stone butresses. It carries 32 ton trucks on their way to the local supermarket and has no weight limit!

My new Wills bridges won't be that long and I figure will not need support either.