7mm Pencarrow - Cornish BR(S)

[Pencarrow]

Up early this morning, so decided to do a bit more on the bridge.

The second layer of 20thou was laminated on to the underside of the arch. But first strategic holes added in the existing ring to enable the solvent to be added.


I also finished off the bracing to the abutment faces. This will give something hard to press against when detailing the abutment stonework, plus it has really firmed up the rigidity of the structure.


Once the arch lamination was fixed and trimmed back, thoughts turned to the arch ring. The SEF brick sheets I'll be using for this are significantly thinner than the Wills stonework, so the arch ring needs building up a good 60thou first from two layers of 30thou (easier to cut).

Arch shapes are extremely wasteful in the sheet they are cut from, so instead I cut them out in smaller segments. The intention was just over 45deg but it appears they are just under 60deg...

The circle cutter came into its own again.


Starting to release the segments.


Very little waste.


Adding the first layer, with the second ready to go.


Bridge back in place with my current thoughts on curving the approaches shown on the wingwall.


(Bless car batteries and cold weather)

 

[Lyndhurstman]

That's some lovely work, Chris. I seem to battle with my Oleo cutter. I'm probably doing it wrong! #whatdoyoumeanprobablyjan?

Cheers

Jan

 

[Dan Randall]

Hi Chris

It’s great to see you making further progress on “Pencarrow”.

Much as I’ve enjoyed seeing the buildings you’ve made outside the railway fence come together, I’m really looking forward to seeing the bridge taking shape. I look forward to seeing the finished article on your demo stand at Guildex in September…


Regards

Dan

 

[Pencarrow]

Hi Chris

It’s great to see you making further progress on “Pencarrow”.

Much as I’ve enjoyed seeing the buildings you’ve made outside the railway fence come together, I’m really looking forward to seeing the bridge taking shape. I look forward to seeing the finished article on your demo stand at Guildex in September…


Regards

Dan

Thanks Dan, I've been putting off the bridge of a while but have reached the point that I need to firm up on the bridge size and location as that affects other elements on the board.

I'm in a significant quandary about the girder bridge deck, particularly all the bolt heads and ribs etc. I'm wandering if brass or 3D print might be a more suitable solution than plastic.

Would welcome peoples thoughts...

 

[Pencarrow]

Oh and @Dan Randall, no invite from G0G yet for 2025...

 

[Alan]

I'm always fascinated and in awe of your building skills.

 

[Pencarrow]

That's some lovely work, Chris. I seem to battle with my Oleo cutter. I'm probably doing it wrong! #whatdoyoumeanprobablyjan?

Cheers

Jan

Thanks Jan, the compass curve cutter is great, but quite basic. It can be a bit imprecise and wander a bit if you try and do too deep a cut in one go, but multiple passes seems to do the trick.

 

[Dan Randall]

Oh and @Dan Randall, no invite from G0G yet for 2025...

It’s almost 9 months away, so fingers crossed...


Regards

Dan

 

[daifly]

This was posted on 10th Jan on the Guild forum by Jackie K.:
"Steve Robinson, Guildex Manager has asked me to post this message

"I would like to apologise to all layouts and demos expecting to hear about Guildex 2025.
Due to family commitments and holidays I am running behind with confirmations and bookings.
I will contact all those provisionally approached for this years Guildex by the end of January"."

 

[simond]

"the girder bridge deck, particularly all the bolt heads and ribs."

There is a danger that, when the only tool you have is a hammer, that everything begins to look like a nail...

Resin 3DP would certainly work to provide details probably as overlays - the printing is relatively easy, but the time is in the 3D CAD
Brass with embossed rivets - I think @dibateg & @mickoo have proven that works - again time in the CAD, but time in the rivet press too. (and I built a Metalsmiths turntable which is a similar structure - lots of overlays, lots to assemble)
And @Jon Nazareth has also shown the way in drilling and inserting rivets.

A brass bridge would undoubtedly be strong enough - but I think I would take the easy way out and 3DP the overlays and stick them to something solid like PCB or ally angle.

 

[Dan Randall]

I'm in a significant quandary about the girder bridge deck, particularly all the bolt heads and ribs etc. I'm wandering if brass or 3D print might be a more suitable solution than plastic.

Would welcome peoples thoughts...

Personally, I’d opt for etched brass or nickel silver (drawn with CAD), thus ensuring the rivets will be evenly spaced and in straight lines, where they need to be.

Obviously, this can be achieved with 3D printing too, but there’s always the prospect of the girders warping if they’re too thin (and you don’t want them so thick, they look like they’re made from concrete!) and/or displaying layer lines, which may be difficult to remove, without losing rivets too.

Plastic girders are also doable, festooned with 3D printed rivet transfers (which could work out expensive), or embossed by hand, which sounds like long, hard work especially keeping them evenly spaced and straight, but again, how thin can you go before warping becomes a distinct possibility?

Edit: Simon posted, while I was still typing.


Regards

Dan

 

[mickoo]

Thanks Dan, I've been putting off the bridge of a while but have reached the point that I need to firm up on the bridge size and location as that affects other elements on the board.

I'm in a significant quandary about the girder bridge deck, particularly all the bolt heads and ribs etc. I'm wandering if brass or 3D print might be a more suitable solution than plastic.

Would welcome peoples thoughts...

Brass, do not consider anything else....please.....

Do not add 3D overlays to simplified brass structure, it'll look and the overlays will need to be thin and run the risk of warping during print, curing and at any time afterward.

3DP is not the right medium for this at all, it's far better suited to blocky objects or if you're doing panels etc, making them overly thick.

It's a simple single span bridge, you don't need to punch ut all the rivets, just add detailed overlays with half etched rivets. Even if you went for punched rivets I'd wager there's less on there than an engine tender or tank engine sides etc.

The CAD isn't hard, monkey see, monkey do work, couple of hours maybe.

 

[Pencarrow]

I'm always fascinated and in awe of your building skills.

Thank you Alan, much appreciated.

 

[Pencarrow]

For them at the back who has missed a previous post, the prototype inspiration for the girder bridge on the layout is as below...



The top vertical web stiffeners are triangular.

 

[Pencarrow]

Brass, do not consider anything else....please.....

Do not add 3D overlays to simplified brass structure, it'll look and the overlays will need to be thin and run the risk of warping during print, curing and at any time afterward.

3DP is not the right medium for this at all, it's far better suited to blocky objects or if you're doing panels etc, making them overly thick.

It's a simple single span bridge, you don't need to punch ut all the rivets, just add detailed overlays with half etched rivets. Even if you went for punched rivets I'd wager there's less on there than an engine tender or tank engine sides etc.

The CAD isn't hard, monkey see, monkey do work, couple of hours maybe.

Thanks Mick for your thoughts. In my mind I think that I'd already discounted 3D printing, more down to the potential for damage in such an exposed area. I can see the bottom and top flanges getting knocked during track cleaning etc. I'm a firm believer in Sod's Law - in this case, a more delicate item will attract damage causing incidents. Brass can be bent back.

 

[BrushType4]

That’s a job for a laser cutter and a rivet machine.

 

[Pencarrow]

Personally, I’d opt for etched brass or nickel silver (drawn with CAD), thus ensuring the rivets will be evenly spaced and in straight lines, where they need to be.

Obviously, this can be achieved with 3D printing too, but there’s always the prospect of the girders warping if they’re too thin (and you don’t want them so thick, they look like they’re made from concrete!) and/or displaying layer lines, which may be difficult to remove, without losing rivets too.

Plastic girders are also doable, festooned with 3D printed rivet transfers (which could work out expensive), or embossed by hand, which sounds like long, hard work especially keeping them evenly spaced and straight, but again, how thin can you go before warping becomes a distinct possibility?

Edit: Simon posted, while I was still typing.


Regards

Dan

Obviously my default option, as I tend to work in the material, is plastic and with rivet transfers. Done that before and yes the rivet transfers do add up to quite a cost.

I do fancy trying something else this time though.

I do have a rivet press, but not one of the fancy ones that enable you to regulate spacing. I don't have a cad package, can't install one on my work laptop, and other laptops are either with young people at university or are so old they hardly manage to turn on. That's been an ongoing issue with trying to use my secondhand portrait cutter.

I've had a good long look for brass kits but, and I'm not surprised, there's nothing close to what I want. The search did however show that Jim S-W of Birmingham New Street has produced quite a few lovely looking bridge decks from bespoke etchings in 4mm.

Going to need more thought and research.

 

[Pencarrow]

That’s a job for a laser cutter and a rivet machine.

Hi Phil, what material would you suggest cutting it from?

 

[BrushType4]

Hi Phil, what material would you suggest cutting it from?

Plastic. Some call it Rowmark but that is a brand name.

A couple of methods. Use CAD or get a friendly person to do that for you

Engrave away all the excess plastic leaving the rivet detail. Very similar to etching method. No rivet press required. The engraved areas will not be super smooth, but could represent aged iron work quite well.

Or if you do have a rivet press, engrave rivet locations on the reverse side. These make useful location points for the sharp end of the rivet press to lock into for your consistent spacing.

 

[Pencarrow]

And we're back in the room...

One of the reasons I've left the section in place between the abutments is so that I can still use the centre point of the arch to trim and mark out the curved parts.

Here I'm using the compass cutter to trim back the arch ring to be (hopefully) a perfect curve.



This means I'll avoid flat spots that I might have got using a file.