Structures for South Pelaw Junction

CornCrake
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Re: Structures for South Pelaw Junction

Postby CornCrake » Thu Aug 23, 2018 2:59 pm

A Nut & Bolt can be undone (& re-used) much more easily than a rivet?

It is probably easier to do a nut & bolt up to a desired torque force, thus stretching the bolt by the desired amount in a more precise way than a rivet?

Rivets are quicker?

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Simon_S
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Re: Structures for South Pelaw Junction

Postby Simon_S » Fri Aug 24, 2018 12:02 pm

I'm not sure, I just happened to come across this article on riveted structures that mentions the hole clearance in the 20 August comment by 'p'. Perhaps a rivet can achieve a higher tension than a bolt. After all, you don't see many bolted together ship's hulls or boilers. Coincidentally, I am in a small way responsible for the handsome bridge pictured in the article as it is on my patch as a Sustrans cycle route volunteer.

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Le Corbusier
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Re: Structures for South Pelaw Junction

Postby Le Corbusier » Fri Aug 24, 2018 5:12 pm

I asked a structural engineer friend of mine (one of whose areas of expertise is bridges) about rivets and bolts.....

Following comments are on steel structural rivets bolts etc.

A rivet is driven into a hole red hot and is then hammered so that it fills the hole completely and the protruding shank is blacksmithed into a head. As the rivet cools it shrinks pulling the two mating surfaces together. It is a very good fixing but difficult especially regards H&S.

A black bolt ( an ordinary bolt) goes into a hole bigger than its diameter (typically 2mm for a 20 dia bolt). It resists shear by moving a bit so the bolt is bearing on some of the edge of the hole in each plate. It can fail by the bolt shearing or the edge of the plate crushing.

A close tolerance bolt is somewhere between the two above with minimal capacity to move and bigger bearing area on the plate edges. It still will shear like a black bolt.

A friction grip bolt works on the basis of pulling the two surfaces together with friction resisting the shear. It is tightened to a particular torque and care is taken in preparing the mating surfaces. It does not move at all.

The above stuff is about resisting shear. Tension in a bolt,rivet and anything else depends on the cross-sectional area and the material strength.

There are also hydraulically stretched rivets ( they have no thread just serrations). They work like friction grip bolts.


On the question of rivets in cast iron his view was that the percussive application would carry with it the inherent danger of cracking the casting.
Tim Lee

Terry Bendall
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Re: Structures for South Pelaw Junction

Postby Terry Bendall » Fri Aug 24, 2018 7:48 pm

CornCrake wrote:A Nut & Bolt can be undone (& re-used) much more easily than a rivet?


Correct. A riveted joint is generally considered to be permanent although the application of a cold chisel to a snap head (rounded head) rivet will remove the head and the rest can be drilled or punched out.

CornCrake wrote:Rivets are quicker?


Not really. Both need a hole drilled. The bolt is put in and tightened. Job done! A rivet needs to be cut to the correct length to either fill a countersink (For a smooth surface) or to form a snap head. Then it needs to be peined over with a hammer to either fill the countersink or form the snap head. For this type a rivet snap then needs to be used to form the smooth rounded head. For a countersunk river the excess material then need to be filed away and the surface smoothed using emery cloth. With care a countersunk rivet should not be visible once the process is complete.

Here ends the metalwork lesson.

Terry Bendall

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John Donnelly
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Re: Structures for South Pelaw Junction

Postby John Donnelly » Sun Mar 24, 2019 8:39 pm

The model of the bridge was finished a couple of weeks ago.

Fully painted and weathered but awaiting capping stones for the piers:

Image

Capping stones added:

Image

The centre and right hand spans had cable supports for the colour light signal that controlled access to the junction from the ECML - these have been added using signal ladders which have had every other rung removed:

Image


Image

So, that's the first structure for the layout finished and I'm pretty pleased with it. Looking at it with a critical eye, the bolts are a little too large but I can live with it.

pete55
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Re: Structures for South Pelaw Junction

Postby pete55 » Sun Mar 24, 2019 9:04 pm

Well done John, looks very good.

So, baseboards next then!!!

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John Donnelly
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Re: Structures for South Pelaw Junction

Postby John Donnelly » Sun Mar 24, 2019 9:08 pm

Cheers Pete.

Yes, baseboards next, going to concentrate on the section between this bridge and the Pelton Lane one first...


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