Lift up bridge questions

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GAP
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Lift up bridge questions

Post by GAP » Sun May 10, 2020 10:14 pm

I am installing a lift up (as opposed to lift out) bridge to allow access to the centre of the loop.
It will be hinged at one end and aligned at the non hinged end with lift out rail clamps.
I am concerned that at the hinged end the rail on the bridge will foul the rail on the base when the bridge is lifted.
Has anybody done something like this and are there any tips/suggestions that could be passed on?

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philipy
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Re: Lift up bridge questions

Post by philipy » Mon May 11, 2020 6:56 am

There are various types/shapes of cranked or offset hinges available which do exactly what you need. Mainly intended for things like windows to allow the to swing back fluch into the frame but work equally well horizontally as vertically. I used them for railway flaps in front of doors and windows many years ago, when we built a railway line round their bedroom for my young sons, many years ago.
It's too long agao for me to remember exactly what I used but a search on ebay and/or amazon should find plenty of options.

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Re: Lift up bridge questions

Post by Nojahoda » Mon May 11, 2020 6:57 am

I haven't done it, but if you have the hinge axis above the railhead then there will be no issue with the bridge rails fouling the fixed rails.

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Re: Lift up bridge questions

Post by gregh » Mon May 11, 2020 6:57 am

You have seen my bridges.
The 'trick' is to have the hinge pivot ABOVE the top of the rails.

These pics are of my alum bar rail, but I did have a bridge with normal rails at Ti-tree, (now demolished and no pics.)
My 'hinge' is just a few bits of steel with 1/4" bolts - rough and ready but been there for 25 years!
hinge3.JPG
hinge combined 2.jpg

Note that I used 'outriggers' to align the rails as the rough hinge had a lot of play. Easy with the alum bar, but it's not hard to do with normal rails - I just ground the foot down to the width of the head and soldered some 2mm brass on.
I used the same method at the 'lifting' end to align the rails automatically.
Greg from downunder.
The Sandstone & Termite's website: http://www.members.optusnet.com.au/satr/satr.htm

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Re: Lift up bridge questions

Post by RylstonLight » Mon May 11, 2020 9:23 am

The Rylston Light Mark 1 had a complicated aluminium through-truss lift-bridge, but the mechanics were simple as per the previous posts with the hinge pivot just above the rail top level, the only thing I would add would be to think about expansion and contraction. I fitted mine on a cold day and then couldn’t close the bridge when I wanted to run it on the first nice sunny day! :oops:

Newbie mistake, I then worried (after trimming the rails) that the gap would be too great on cold days, but suprisingly that seemed to be ok. I have no science/maths to offer but a tight fit on a hot day seemed to be just right; but the bridge was under the shade of a Leylandi weed.

Other may offer better advice about the optimum gap but it can be an issue if not planned for. It might be worse in a sunny spot.

The bridge worked well, but as time went on It bothered me that such a grand design was out of keeping of the RLR, so was scrapped and has not been reserved for mark 2.

Andy
Andy S. at the Rylston Light Railway

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Jimmyb
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Re: Lift up bridge questions

Post by Jimmyb » Mon May 11, 2020 2:34 pm

Never done a lift up bridge for the garden, but similar to the above, it hinged portable layouts, the hinges are higher that the highest fixed point to allow the items to "swing" away from each other, your bridge should be no different.
Keep the rubber-side down

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Re: Lift up bridge questions

Post by GAP » Mon May 11, 2020 10:27 pm

Thank you all for the suggestions.

I have 2 options;
1. hinges on top of the bridge seems to be the norm
2. and one suggestion where the hinge is below the bridge.
Korms Bridge.jpg
Bit more thinking/planning to be carried out

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Re: Lift up bridge questions

Post by philipy » Tue May 12, 2020 6:24 am

Either should work. The 'below' option will be potentially less visually obtrusive but more complicated to implement, I think.

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Re: Lift up bridge questions

Post by Jimmyb » Tue May 12, 2020 9:37 am

I agree with Philip, the hinge below does look good, but could be complicated, but if you have the skill *and i am sure you have) go for it.
Keep the rubber-side down

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Re: Lift up bridge questions

Post by RylstonLight » Wed May 13, 2020 10:48 am

Like the under-bridge solution, would like to see the development of this bridge. Looks like it would work.

Andy
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Re: Lift up bridge questions

Post by GAP » Wed May 13, 2020 11:26 am

This will be no problem for Ben Hur constructions. :shock: :shock:

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Re: Lift up bridge questions

Post by GAP » Wed May 20, 2020 9:23 am

I went with a hinges under the bridge option using this suggestion.
Korms Bridge.jpg
I have started building the hinge area and it is working out well so far.
I am using gate hinges
P1050743.JPG
P1050744.JPG
The gap needed to allow opening is not really that wide it is slightly wider than the thickness of the board.
P1050745.JPG
The bridge will be made out of hardwood reinforced with steel angle.
To get a level, the hinges will be recessed into the mounting block.
The lower part of the hinges will be cut off to remove the piece protruding into the walkway.
P1050741.JPG
This is part of Stage 2 of the build and details will be put on my blog in due course.

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Re: Lift up bridge questions

Post by Jimmyb » Wed May 20, 2020 6:05 pm

This certainly looks a robust build :)
Keep the rubber-side down

JimmyB

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Re: Lift up bridge questions

Post by GAP » Mon May 25, 2020 10:35 am

Jimmyb wrote:
Wed May 20, 2020 6:05 pm
This certainly looks a robust build :)
Wait till you see the MkII version it is getting bigger than the Sydney Harbour Bridge.
Wood goes and steel is a replacement

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Re: Lift up bridge questions

Post by Jimmyb » Mon May 25, 2020 10:26 pm

GAP wrote:
Mon May 25, 2020 10:35 am
Jimmyb wrote:
Wed May 20, 2020 6:05 pm
This certainly looks a robust build :)
Wait till you see the MkII version it is getting bigger than the Sydney Harbour Bridge.
Wood goes and steel is a replacement
WOW can’t wait to see that.
Keep the rubber-side down

JimmyB

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