Lift up bridge questions

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GAP
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Re: Lift up bridge questions

Post by GAP » Mon May 25, 2020 10:43 pm

Pictures of the mounting block made from "C" Purlins and the new more robust hinge.

Type of Purlin pieces used
C purlin pieces.JPG
C purlin pieces.JPG (149.63 KiB) Viewed 6189 times
The mounting block
C Purlin Mounting Block.JPG
C Purlin Mounting Block.JPG (99.7 KiB) Viewed 6189 times
New hinge
Second Hinge.JPG
Second Hinge.JPG (42.27 KiB) Viewed 6189 times
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Re: Lift up bridge questions

Post by GAP » Wed May 27, 2020 12:31 am

I built the bridge supports out of aluminium box section to reduce the weight so SWMBO can open it, if I made it out of hardwood it would be to heavy for her.
The whole bridge will be made out of aluminium.
Some pictures of the supports an hinges also showing mounting block attaching bolts.

Bridge Supports.jpg
Bridge Supports.jpg (170.12 KiB) Viewed 6163 times
Bridge Support Open Position.jpg
Bridge Support Open Position.jpg (156 KiB) Viewed 6163 times
Hinge with Support.jpg
Hinge with Support.jpg (75.9 KiB) Viewed 6163 times
Hinge with Support (Open).jpg
Hinge with Support (Open).jpg (106.38 KiB) Viewed 6163 times
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Re: Lift up bridge questions

Post by GAP » Wed May 27, 2020 10:30 am

After some testing of the track alignment, the supports will have to be re aligned but that is all OK as it is just a simple re-drill of 2 of the 3 hinge mount holes and re attach.
This will allow the track to run straight across the opening with curves either side.
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Re: Lift up bridge questions

Post by GAP » Thu May 28, 2020 8:51 am

A question was asked on another forum about the pivot height and when I revisited it I found that when track is attached to the supports there is a yawning gap that just does not work.
I have built a proof of concept jig to test the opening method and so far it appears that the secrets to having the hinge below the track is the angle of the cut made to the track, 45 degrees as opposed to vertical seems to work the best with no fouling.
So it is back to the drawing board for this little project.
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Re: Lift up bridge questions

Post by GAP » Fri May 29, 2020 1:18 am

Bridge Design MkIII proof of concept jig has been built and the design has been tested with positive results.
As previously stated the secret of the opening is the 45 Degree cuts in the rail which allows the moving rail to drop away from the fixed rail without fouling.
The moving arm of the hinge is level with the baseboard and the gap that the rail folds into is not real wide.
The error I made with the MkII was that I put the bridge support on top of the hinge and when the rail was added the gap was just unworkable as the support folded into it, the bridge support will now be level with the top of the hinge and will not fold into the gap.

So now the bridge construction can now begin following the concept principles.
Closed
Proof of Concept Jig (Closed).jpg
Proof of Concept Jig (Closed).jpg (97.21 KiB) Viewed 6084 times
Open
Proof of Concept Jig (Open).jpg
Proof of Concept Jig (Open).jpg (90.58 KiB) Viewed 6084 times
Close up (closed)
Proof of Concept Jig (Rails Close Close Up).jpg
Proof of Concept Jig (Rails Close Close Up).jpg (66.25 KiB) Viewed 6084 times
Close up (Semi Open)
Attachments
Proof of Concept Jig (Rails Semi Open Close up).jpg
Proof of Concept Jig (Rails Semi Open Close up).jpg (68.63 KiB) Viewed 6084 times
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Re: Lift up bridge questions

Post by GAP » Fri May 29, 2020 10:00 am

The new mounting block has been made from wood and work on the first hinge has started.
Unfortunately I used some hardwood from the $2 per 1.2M rack and it is cut crooked i.e. 32mm on one side and 30mm on the other.
Luckily I have 2 different sized mounting bolts and the longer one just happens to bring the hinge top level with the baseboard.
I have used a couple of shims to get the hinge top level with the approach baseboard.
Opening showing Block and Hinge.jpg
Opening showing Block and Hinge.jpg (140.74 KiB) Viewed 5378 times
Mounting Block Front.jpg
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Re: Lift up bridge questions

Post by GAP » Thu Jun 18, 2020 9:28 am

The lift up bridge is finished!!!

From a concept put forth by a modeller Korm Kormsen who frequents a US forum of putting the hinge under the track, as opposed to the convention of having the hinge joint above the track, to the finished thing has been a Ben Hur type production.

Trains can now cross the entrance to the firepit area with no problems.

Bridge non hinge end is located by using "Hillmans" lift out bridge clamps.

All that need to be done is to design and manufacture a safety device that stops trains from running off the edge when the bridge is open, I use battery power so breaking the track circuit does not apply, some form of physical barrier will be required possibly even a catch point.

More thought on the safety device is required, any suggestions folks???

Blog will be updated shortly.
Bridge Side View toward house.jpg
Bridge Side View toward house.jpg (142.15 KiB) Viewed 5265 times
Bridge Lenghtwise.jpg
Bridge Lenghtwise.jpg (151 KiB) Viewed 5265 times
Train on bridge.jpg
Train on bridge.jpg (154.78 KiB) Viewed 5265 times
Hillmans clamps close up 1.jpg
Hillmans clamps close up 1.jpg (99.86 KiB) Viewed 5265 times
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Re: Lift up bridge questions

Post by Peter Butler » Thu Jun 18, 2020 10:07 am

Well done for persevering to a most satisfactory conclusion, it looks great.
I have never had the need for a lift bridge myself so not able to give advice on a temporary stop device, however, the idea of catch points seems to create another problem in that your battery locos will continue to travel on a flat surface even if derailed. You would also have to remember to switch them (two points, both ways) so that would be just another activity to remember every time you, and others, use the bridge.
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Re: Lift up bridge questions

Post by philipy » Thu Jun 18, 2020 10:19 am

Well done, looks good.
GAP wrote: Thu Jun 18, 2020 9:28 am
All that need to be done is to design and manufacture a safety device that stops trains from running off the edge when the bridge is open, I use battery power so breaking the track circuit does not apply, some form of physical barrier will be required possibly even a catch point.

More thought on the safety device is required, any suggestions folks???
You presumably don't need anything at the hinge side, since the bridge itself would be in the way of a runaway?
As for the open side, could you have a spring loaded plate which is held down by the weight of the bridge when closed but springs up automatically as it is opened? A suitably positioned hook/latch could then hold it up in position.
Depending on the actual design it might be possible to have the plate counterbalanced rather than spring loaded?

just a few thoughts.
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Re: Lift up bridge questions

Post by ge_rik » Thu Jun 18, 2020 10:50 am

Looks good, Graeme. Very elegant!

Philip's idea sounds good, but I tend to go for the simplest solutions. I'd just have a piece of wood with a couple of dowels that slot into a couple of holes either side of the track. Of course, being non automatic, you'd have to remember to slot it in when you raise the bridge.

I have a couple of lift out bridges on the PLR, and so far I've never forgotten to install them when running. However, neither is on a main thoroughfare so there's very little pedestrian traffic through them when trains are running.

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Re: Lift up bridge questions

Post by Peter Butler » Thu Jun 18, 2020 11:54 am

A slot-in barrier would probably be the simplest way to solve the issue and be perfectly adequate for the situation if it was for one person to control. In this case though, especially with the fire pit in the centre as an entertainment area, it looks as though other people, family members and guests, might have to be considered for access and each would need to be advised on the method, and importance, of ensuring the system was employed at all times. Children would almost certainly forget and adults might not appreciate the idea of being 'told' what to do.
An automatic system would be my own preference.
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Re: Lift up bridge questions

Post by Jimmyb » Thu Jun 18, 2020 5:44 pm

Graham, if you have another "bridge" hinged at the opposite side to the train bridge hinge, slightly lower, when the bridge is lifted, to get past you would then need to lift this other section up, creating a physical barrier.

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Re: Lift up bridge questions

Post by GAP » Thu Jun 18, 2020 10:03 pm

My thought at the moment is a lever with the pivot offset that the bridge pushes on when closed, so the end under the bridge is down and the other end is up.
This connects via a simple linkage to another lever under the base board again with an offset pivot so that the linkage end is also up and the other end is down.
On the down end of the second lever there is a bar at 90 degrees across it that has 2 rods pointing up.
These rods slide in a tube and protrude between the sleepers when the the second lever moves up ie when the bridge is open and will be in the path of a loco.
The loco will hopefully stop at the protruding rods and not derail but just sit there with wheels slipping, unless of course it is one with a traction tyre which adds a different dimension to the solution. :shock:
I would need a fence along one track as it is close the the edge of the baseboard but that is easily doable and would fit in with the theme easily.

I have considered putting some sort of barrier between the rods that slips into a slot cut in the base board but that involves cutting rail and adds an alignment issue.

Hopefully I have explained the idea clear enough. :roll:

More though may be required :study:

Edit;
Just had a thought instead of rods just sticking up the could operate boom gates that cross the track, they would look a bit more elegant.
Its amazing what a cuppa can do for the thought process.
Graeme
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Re: Lift up bridge questions

Post by GAP » Fri Jun 19, 2020 1:33 am

I have updated my blog about the construction of the railway so that it now reflects where it is at.
https://ringbalin-light-railway.blogspo ... st%20Posts
Graeme
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