Pont y Gelli - A composite printed bridge

A place where discussions are about 3D printing.
Trevor Thompson
Trainee Driver
Trainee Driver
Posts: 977
Joined: Fri Oct 05, 2018 6:30 pm
Location: South West Wales

Re: Pont y Gelli - A composite printed bridge

Post by Trevor Thompson » Thu Mar 09, 2023 12:11 pm

Both sides are covered in the lattice work. I have some deck printed. The rail fits in the chairs and it the deck fits in place. Rolling stock flanges miss the chairs as well:
IMG_2824.JPG
IMG_2824.JPG (2.09 MiB) Viewed 3389 times
IMG_2825.JPG
IMG_2825.JPG (2.25 MiB) Viewed 3389 times
However. The gauge is a bit tight. 31.25mm instead of 32mm. I think the deck would be better if it were a bit thicker as well. So I have modified the design and will start printing again. It will take a while as each piece of deck takes 8 hours to print. I think I will wait until I have 4 lengths ready before fixing it into position.

Trevor

User avatar
philipy
Moderator
Moderator
Posts: 5079
Joined: Sun Jan 30, 2011 3:00 pm
Location: South Northants

Re: Pont y Gelli - A composite printed bridge

Post by philipy » Thu Mar 09, 2023 1:28 pm

Trevor Thompson wrote: Thu Mar 09, 2023 12:04 pm Oh matching screw threads - how did you do that?
I was doing some work for an acquaintance, just printing project boxes for him. Part of his work involves a small lens focussing onto a photodiode on a pcb and he asked if it would be possible to print some sort of screw focusing mechanism. I said I'm sure it's possible but no idea how to actually draw a screw thread, let alone how printable it would be.
Anyway, a quick search came up with this Youtube link:
https://www.youtube.com/watch?v=k8AC5LNMo-g

...and to my amazement, not only is the video really easy to follow but it actually works! Took me several goes to work through it and get the steps into my poor brain but the result is perfect for what I needed.

Basically I needed a 22mm ID tube with a screw thread on the outside face, and a 3mm thick plate with a matching internal threaded hole, and to get 2 or 3 threads on the inside of the plate hole.

I followed the video to get a solid screwed rod and then used the scale tool to push and pull it until I had the threads deep enough to get 3 in the 3mm plate i.e 1mm pitch. Then I drew a 22mm diam circle on the end and pushed it through to get the hollow cylinder.

I duplicated that and saved one copy, out of the way to avoid accidents.
I then constructed a box to completely enclose the hollow threaded cylinder and checked to ensure yhat the top and bottom faces were all coplaner ( had to use "intersect faces" to be sure). Then I deleted all the internal geometry and that left me with an internally threaded hole in a block. This thread of course exactly matches the original one so there is no way they would slide inside each other, so I scaled the block slightly in the horizontal plane to make it approx half the thread depth larger diameter.... hey presto!

Screw thread as constructed - compressed to the right pitch - matched threaded block
Screenshot 2023-03-09 13.15.28.png
Screenshot 2023-03-09 13.15.28.png (55.66 KiB) Viewed 3384 times
And this is the end result ( ignore the gap, I made this one too tight and had to cut it off :oops: ):
P1010019.jpg
P1010019.jpg (256.06 KiB) Viewed 3384 times
Philip

User avatar
SimonWood
Trainee Driver
Trainee Driver
Posts: 656
Joined: Tue Apr 07, 2015 9:46 pm
Location: West Wales
Contact:

Re: Pont y Gelli - A composite printed bridge

Post by SimonWood » Thu Mar 09, 2023 3:13 pm

Trevor Thompson wrote: Thu Mar 09, 2023 12:11 pm I have some deck printed.
That really looks the part!

Deck, sleepers and chairs all printed together?

It has inspired me to think that I could upgrade the look of my bridges, not to anything as impressive as you are printing, but with a deck and handrails it would be a big improvement in appearance.

Trevor Thompson
Trainee Driver
Trainee Driver
Posts: 977
Joined: Fri Oct 05, 2018 6:30 pm
Location: South West Wales

Re: Pont y Gelli - A composite printed bridge

Post by Trevor Thompson » Thu Mar 09, 2023 3:18 pm

SimonWood wrote: Thu Mar 09, 2023 3:13 pm
Trevor Thompson wrote: Thu Mar 09, 2023 12:11 pm I have some deck printed.
That really looks the part!

Deck, sleepers and chairs all printed together?

It has inspired me to think that I could upgrade the look of my bridges, not to anything as impressive as you are printing, but with a deck and handrails it would be a big improvement in appearance.
Yes printed in one piece. Had a bit of a problem with the printer - messed up the slicer settings and made the layer height too high, so the layers were not bonded properly on one section. The other section parted from the bed - part of the same problem. All sorted now. So starting the deck again wasn't really a problem. If you want the stl file for the chairs I can add it to the forum.

Trevor Thompson
Trainee Driver
Trainee Driver
Posts: 977
Joined: Fri Oct 05, 2018 6:30 pm
Location: South West Wales

Re: Pont y Gelli - A composite printed bridge

Post by Trevor Thompson » Wed Mar 15, 2023 5:47 pm

The deck is now printed and assembled with the rails inserted:
IMG_2851.JPG
IMG_2851.JPG (2.2 MiB) Viewed 3296 times
Excuse the different colours that I have used to print the deck, I wanted to use up what I had in stock before ordering more filament. It just needs the handrail added, and the first section of that is in place.

As an aside it is interesting what a difference the colour makes to the way the filament prints. The white filament seems to require a slightly higher temperature to print properly. I get consistent issues printing white - such as the sides of the chairs fall off readily and there are more stray bits of filament lying around when the print is finished.

Trevor

Trevor Thompson
Trainee Driver
Trainee Driver
Posts: 977
Joined: Fri Oct 05, 2018 6:30 pm
Location: South West Wales

Re: Pont y Gelli - A composite printed bridge

Post by Trevor Thompson » Thu Mar 16, 2023 9:24 am

philipy wrote: Thu Mar 09, 2023 1:28 pm
Trevor Thompson wrote: Thu Mar 09, 2023 12:04 pm Oh matching screw threads - how did you do that?
I was doing some work for an acquaintance, just printing project boxes for him. Part of his work involves a small lens focussing onto a photodiode on a pcb and he asked if it would be possible to print some sort of screw focusing mechanism. I said I'm sure it's possible but no idea how to actually draw a screw thread, let alone how printable it would be.
Anyway, a quick search came up with this Youtube link:
https://www.youtube.com/watch?v=k8AC5LNMo-g

...and to my amazement, not only is the video really easy to follow but it actually works! Took me several goes to work through it and get the steps into my poor brain but the result is perfect for what I needed.

Basically I needed a 22mm ID tube with a screw thread on the outside face, and a 3mm thick plate with a matching internal threaded hole, and to get 2 or 3 threads on the inside of the plate hole.

I followed the video to get a solid screwed rod and then used the scale tool to push and pull it until I had the threads deep enough to get 3 in the 3mm plate i.e 1mm pitch. Then I drew a 22mm diam circle on the end and pushed it through to get the hollow cylinder.

I duplicated that and saved one copy, out of the way to avoid accidents.
I then constructed a box to completely enclose the hollow threaded cylinder and checked to ensure yhat the top and bottom faces were all coplaner ( had to use "intersect faces" to be sure). Then I deleted all the internal geometry and that left me with an internally threaded hole in a block. This thread of course exactly matches the original one so there is no way they would slide inside each other, so I scaled the block slightly in the horizontal plane to make it approx half the thread depth larger diameter.... hey presto!

Screw thread as constructed - compressed to the right pitch - matched threaded block
Screenshot 2023-03-09 13.15.28.png

And this is the end result ( ignore the gap, I made this one too tight and had to cut it off :oops: ):
P1010019.jpg
Impressive and stored away for future use.

Trevor

Trevor Thompson
Trainee Driver
Trainee Driver
Posts: 977
Joined: Fri Oct 05, 2018 6:30 pm
Location: South West Wales

Re: Pont y Gelli - A composite printed bridge

Post by Trevor Thompson » Wed Mar 22, 2023 1:28 pm

The bridge is now complete, apart from painting:
IMG_2860.JPG
IMG_2860.JPG (1.77 MiB) Viewed 3162 times
So I can put it aside until the trackbed catches up!

Trevor

User avatar
Peter Butler
Driver
Driver
Posts: 5236
Joined: Sun Sep 09, 2012 10:33 pm
Location: West Wales

Re: Pont y Gelli - A composite printed bridge

Post by Peter Butler » Wed Mar 22, 2023 1:47 pm

It does look to be a magnificent structure Trevor, a complicated item to build by any other means.
The best things in life are free.... so why am I doing this?

User avatar
SimonWood
Trainee Driver
Trainee Driver
Posts: 656
Joined: Tue Apr 07, 2015 9:46 pm
Location: West Wales
Contact:

Re: Pont y Gelli - A composite printed bridge

Post by SimonWood » Wed Mar 22, 2023 6:32 pm

Superb! Looks wonderful with Linda giving a sense of scale.

Post Reply

Who is online

Users browsing this forum: No registered users and 5 guests