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Ron Heggs

Points Bridge, Hagg Bank, Wylam, Northumberland

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This build is a personal challenge, and in part a nod to George Stephenson who was born at Wylam in 1781

 

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The bridge is 240ft in length, and in 4mm scale will be 960mm long, and construction will be in styrene - What else :scratchhead:

 

A quick CAD drawing

post-10633-0-03651500-1332457509_thumb.png

 

- now no guessing how many cans it will support :nono:

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Our friends, Jan and Gordon, used to live at Hagg Bank in the 1980s- this bridge was the shortest cycling and walking route to Wylam from the hamlet, so we used to cross it quite often. Good luck with building it- I'll be interested to see how it turns out.

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Thanks Brian for your input

 

A section through the bridge deck - 110.4mm overall width

 

post-10633-0-37835500-1332523077_thumb.png

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The deck bridge support beams completed - 20 x 110.4mm long x 9mm deep

 

post-10633-0-82122700-1332542293_thumb.jpg

 

post-10633-0-15037400-1332542314_thumb.jpg

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Uh oh - another masterclass in styrene-bashing! Think I'll go home now!

 

Go for it Ron, looking forward to the finished model.

 

Regs

 

Ian

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Uh oh - another masterclass in styrene-bashing! Think I'll go home now!

 

Go for it Ron, looking forward to the finished model.

 

Regs

 

Ian

Hi, Ian

 

Thanks for your motivating comments

 

A scratchbuilding challenge is just what I need to keep my main long-running constructions on track - we all need alternative subjects to keep the tedium of main tasks from stalling

 

The real challenge in this build is to ensure the bridge deck can be properly supported from the bridge arches by the relatively thin suspension hangers

 

Cheers

 

Ron

Edited by Ron Heggs
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20 of 22 deck support beams

post-10633-0-38860300-1332612806_thumb.jpg

 

First six beams fixed to bottom flange of rail support beams

post-10633-0-25591200-1332612821_thumb.jpg

 

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All 22 beams fixed to bottom flanges

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Placed right way up

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Total length 966mm + 50mm at each end for deck support on stone built abutments at river banks

 

Rail support beam webs and top flanges next -

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- a photo to show how flexible the construction is so far -

post-10633-0-65942500-1332629182_thumb.jpg

 

Rail support beam webs and top flanges fitted -

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Full length shot - on same supports as first photo above

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The flexibility has almost gone

post-10633-0-43385300-1332629590_thumb.jpg

 

Deck plating and its supports next -

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This is a nice looking project. The prototype is a spectacular bridge. I wish you all the best, what you have done looks very neat.

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This is a nice looking project. The prototype is a spectacular bridge. I wish you all the best, what you have done looks very neat.

Hi,

 

Thanks for your comments

 

Ron

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The decking side plating in place -

 

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- next the curved inter-rail plating

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Guest Max Stafford

Ron, your work rate is staggering!

 

The deck's looking great too - this is almost an illustrated demonstration of how the full size article is constructed. Quite educational.

 

Dave.

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Ron, your work rate is staggering!

 

The deck's looking great too - this is almost an illustrated demonstration of how the full size article is constructed. Quite educational.

 

Dave.

 

Hi, Dave

 

Thanks for your compliments - photos of the inter-rail curved plating will be posted tonight

 

Cheers

 

Ron

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Hagg Bank

What a delightful name!

 

Great work, as ever, Ron - the climate is certainly conducive to railway modelling!

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The denizens of Hagg Bank (about 50 souls, mostly related apart from a handful of incomers like Jan and Gordon) used to claim that the bridge served as a prototype for two, somewhat larger, bridges of similar design- the Tyne Bridge and Sydney Harbour Bridge. I wonder if there is any truth in this?

The entire settlement- about fifteen to twenty houses- appears to have been built to serve the railway; there was a junction between the Newcastle and Carlisle line and the line which ran via Newburn to Newcastle, along with extensive sidings on the Prudhoe side serving a chemical plant (Kimberly-Clark's plant is on this site) and a colliery.

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What a delightful name!

 

Great work, as ever, Ron - the climate is certainly conducive to railway modelling!

Thanks

 

Just have to tear myself away from the villa reform, and lazing in the sun, to do a bit of modelling :sungum:

 

Ron

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The denizens of Hagg Bank (about 50 souls, mostly related apart from a handful of incomers like Jan and Gordon) used to claim that the bridge served as a prototype for two, somewhat larger, bridges of similar design- the Tyne Bridge and Sydney Harbour Bridge. I wonder if there is any truth in this?

The entire settlement- about fifteen to twenty houses- appears to have been built to serve the railway; there was a junction between the Newcastle and Carlisle line and the line which ran via Newburn to Newcastle, along with extensive sidings on the Prudhoe side serving a chemical plant (Kimberly-Clark's plant is on this site) and a colliery.

Thanks Brain

 

I had heard about the bridge prototype story, and visited Kimberly Clark at Prudhoe a number of times during the 1970's & 80's on engineering projects

 

Ron

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Thanks Andy Y, hope you will enjoy another plastic bending project

 

Ron

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Only managed to fix one inter-rail curved plating section tonight -

 

post-10633-0-78580700-1332794633_thumb.jpg

 

You may ask, why ?

 

Was thinking about the deck support/hanger strength today, and having to prove their load limits before assembly

 

Checking the clear space between the rows of support/hangers and also between adjacent support/hangers, shows dimensions of 52mm and 43mm respectively

 

Test loads usually comprise cans which are 67mm diameter, and could not be accommodated

 

The alternative is to test the support/hanger itself and the attachment methods

 

A stress test for the bridge deck suspension support/hangers

 

The bridge deck is suspended from 48 hangers – 16 per arch

 

The hanger is made from 20thou x 100thou (0.5mm x 2.5mm) plastic strip

 

The anchor pads fitted either side of each end of the hanger are also made from the same strip. The lower end being 14mm long, and the upper end 15mm long

 

On the model the pads will be fixed to the ends of the deck support beams (contact area 9mm x 2.5mm), and the lower arch member (contact area 4mm x 2.5mm)

 

For this test the pads are fixed to scrap 40thou pieces to enable the upper end of the hanger to be fixed to a suitable support, and also enable a test load to be suspended from the lower end

 

The test is not only to test the ductile strength of the styrene, but also the shear strength of the fixing area of the pads

 

Hanger with pads attached - the hole at the upper end is for the S hook -

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Upper end detail -

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Lower end detail -

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Test load - 2 x 440ml (2 x 0.4kg)

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Test -

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Result -

No stretching of support/hanger

No separation or distortion of pads or attachments

 

Conclusion -

The total load using the test load on each of 48 supports/hangers would be 0.8kg x 48 = 38.4kg (84.5 lbs)

 

This is well in excess of any load expected to be placed on the bridge

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The second inter-rail curved plating completed -

post-10633-0-55496400-1332963521_thumb.jpg

 

End views to show the curved plating -

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The deck centre plating can only be fixed when the middle of the three arches is completed with the support/hangers fixed to the deck beam

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The template for the three arches has been printed and fixed to the building board -

 

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- construction of the arches is about to commence

 

Detail build process has still to be finalised - due to the numerous cross-bracings - Topside of lower arch/Both sides of top & bottom arches including the internal cross-bracings to the outer bracings - All in an arch cross-section just 10mm wide x 32mm high

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