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Messin' With Resin - 3D printed track

Martin Wynne

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I've been mucking around with TurboCAD (Platinum unfortunately) and I was able to create this in less than an hour.
Hi Andy,

Very good -- so far. :)

Chair screws have a tapered square head. Below that is a pan flange, which is larger than the tapered oak ferrule which locates in the tapered hole in the casting:
chair_screw_400x742.png

The ferrule provides a precise location on the timber without needing a close tolerance hole in the casting. The ferrule stands proud of the casting to be effective. If frequent tightening cause the screw to contact the casting, the ferrule must be replaced. Different sizes of ferrule are available for maintenance purposes. Modern ferrules are no longer oak, but a tough plastic polymer.

This is Templot's generated geometrical version of that, I think the flange could be beefed up a bit.:

dxf_screw_head_860x646.png


cheers,

Martin.
 
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AndyB

Member
Thank you for that Martin.

I guessed the square heads were 1.125" so I was not too far off. I can easily taper them and fillet the corners too. Probably a waste of time for 1:76.2 but I'm drawing it actual size so it can be scaled.

My base plate might be a bit too thick. It's currently 5/8" but looking at some photos I think it should be a bit thinner.

How high are the tops of the screws relative to the timbers typically? (There's not too much bullhead track in North Idaho for me to measure :D)

This started off as a bit of an exercise to see how well TurboCAD produces fillets. So far I'm quite impressed. BTW, this is a solid model rather than a surface. I only applied the fillets after all the basic geometric shapes had been added together. It will be interesting to see if there are any holes in the STL. This version also has some 3D print tools but I have not investigated them yet.

The big snag is it is not cheap but it's nowhere near as expensive as the likes of Autocad. I decided it wasn't too bad if I amortized the cost over the number of years I'm likely to be able to use it. There are also annual subscription versions but I don't care for that approach. The 2020 download actually includes the code for all the versions including Platinum. You buy license keys that unlock the various features.

Like all things "you pays your money and you gets what you pays for" (in theory) and I concluded the resolution of the resin printer justified some decent CAD software. I suppose I could even defray some of the cost by producing highly detailed STL files and I'd at least be able to validate them by printing test pieces here.

Cheers,
Andy
 
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Martin Wynne

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Hi Andy,

Answering for REA chairs (other chairs are available):

My base plate might be a bit too thick. It's currently 5/8" but looking at some photos I think it should be a bit thinner.

Chair base is 1/4" thick at edge.

Seat for rail is 1.3/4" thick.

How high are the tops of the screws relative to the timbers typically? (There's not too much bullhead track in North Idaho for me to measure :D)

Before tightening: about 3". After fully tightening: 2.3/4" min, say 2.7/8" in new track.


The standard REA chair drawings are available here:

http://www.lmssociety.org.uk/assets/pdfs/permanentWay1928.pdf

Unfortunately the scan quality is rather poor and some dimensions are difficult to read. Chair screws and ferrules are on page 1.
The ordinary S1 chair is on page 4.

Extracting some dimensions from more readable scans:

Screw head top. 1.1/16" sq.

Screw head at flange: 1.1/8" sq.

Screw head height above flange: 7/8" at side, 15/16" at corner.

Flange thickness: 3/8" at side of head.

Overall height of screw head and flange: 1.1/4"

Flange diameter 1.7/8"

Ferrule diameter at top (before compression): 1.35/64"


Boss on casting: overall height: 1.1/2"

Boss on casting: top diameter: 2"

Pictures of some chairs. Notice how prominent the screws can be. The screws are galvanised, the chair castings are raw, which is why the screws stand out in photos, especially when new:

bullhead_crossing_detail1.jpg


long_check3.jpg


pw_heap.png


p.s. I have copied the above into the Resources section, to keep the info easier to find, and allow it to be tagged.

cheers,

Martin.
 
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Martin Wynne

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Location
West of the Severn UK
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Please do not send requests for help direct to me via email.

Post your questions on the forum where everyone can see them and add helpful replies.
The big snag is it is not cheap but it's nowhere near as expensive as the likes of Autocad.

Hi Andy,

TurboCAD pricing is impossible to pin down, at least here in the UK. My version is TurboCAD Deluxe 2D/3D which cost me all of £9.99 as a special offer only a few years ago. I assumed others would be able to find it at a similar price. But searching comes up with £179.99 as the current price. The disparity between these two costs is difficult to fathom.

Autodesk's Fusion 360 is free for personal use. I believe it is popular with modellers for 3D printing. But it's online only, and involves jumping through several registration and login hoops to get there. I assumed that being from Autodesk it would support 3D DXFs from Templot -- it is after all their file format. But sadly no. :(

But I have now implemented a direct export in STL from Templot, so no-one now needs an expensive 3D CAD just to convert Templot's DXF output to STL for 3D printing.

cheers,

Martin.
 
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Trevor

Member
Location
Morecambe
This afternoon's entertainment was to get the chair plugs into the 2D:

View attachment 716

I have put a 1/2" break across the plug corners for a clear fit in the sockets. For the bridge chairs I have increased the base overlap, so that the sockets do not get too close to the edge of the timber.

The plugs and screw centres aren't really needed in 2D, but the only way to check that the code is putting every one in the right place is to draw them on the screen.

One more tiny step on what is going to be a long journey.

Martin.
Hello Martin,
Is there a particular reason why you are using square/rectangular sockets for chair location? Would a round socket allowing them to rotate not enable one to adjust a chairs position indefinitely without restriction? Or am I missing something really obvious?
Trevor :)
 
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Martin Wynne

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Please do not send requests for help direct to me via email.

Post your questions on the forum where everyone can see them and add helpful replies.
Hello Martin,
Is there a particular reason why you are using square/rectangular sockets for chair location? Would a round socket allowing them to rotate not enable one to adjust a chairs position indefinitely without restriction? Or am I missing something really obvious?

Hi Trevor,

The angle of a chair on a timber is determined by the turnout geometry, there isn't any option for it to be at some other angle.

The idea is that the timber base is 3D printed, or laser cut from plywood, and the chairs plug straight in to the exact position, requiring no gauges or other adjustments.

But I'm not printing the bases or the chairs -- you are. :)

If you want to edit the DXF or STL files to use round plugs and sockets that's up to you. There will also be options in Templot to change the size of the plugs, or have no plugs, or change the chairs to some other design, or flat-bottom baseplates, or whatever you want.

But don't hold your breath. I have a long way to go, and I'm distracted by other things. It's high time I got the 227a update finished and released, it's got a lot of new stuff in it which some folks are waiting for. On top of that I still have the migration to the new server unfinished, and no archive of the old forum yet ready. Strictly speaking getting the Elegoo printer was a mistake, as it's a fresh distraction and has now added a re-write of the 3D output to the pile of other unfinished stuff I have waiting. Templot is supposed to be my hobby, it's not supposed to feel like work. :) But I will get round to everything in the end.

cheers,

Martin.
 
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AndyB

Member
Hi Martin,

Many thanks for all the great information.

If I might ask, how are you eliminating the rail inclination? Are you leaving the bottom of the rail in the same position and pushing the top out, pushing the bottom in or rotating the rail so the bottom moves in and the top moves out?

Also, are you leaving the base full size or are you reducing its length at all?

Cheers,
Andy
 
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Martin Wynne

Admin
Location
West of the Severn UK
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Please do not send requests for help direct to me via email.

Post your questions on the forum where everyone can see them and add helpful replies.
If I might ask, how are you eliminating the rail inclination? Are you leaving the bottom of the rail in the same position and pushing the top out, pushing the bottom in or rotating the rail so the bottom moves in and the top moves out?

Also, are you leaving the base full size or are you reducing its length at all?

Hi Andy,

The rail gauge-face is the datum, and all the chair dimensions have been referenced to scale from there. So I guess that means I have moved the rail foot inwards to bring the rail vertical.

It's a stylised geometrical design, with some intentional changes. For example the key is tapered at both ends for easier threading, and contacts the web fully in its centre only (the prototype key should be wedge shaped). The base edge thickness is increased to avoid damage in handling and allow at least two 0.05mm slicer layers (the scale thickness would be only 0.08mm or 3 thou).

The chair base dimensions are as the drawing, I'm not clear why you think I might have reduced the length?

cheers,

Martin.
 
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AndyB

Member
Thank you Martin.

Re. the length question; if you kick the foot inwards you could make a case that says everything on the outer part of the the chair should move inwards too. It's only about a third of an inch so it's probably better not mess with it and leave the base and screw holes as the prototype dimensions.

Thanks for the swift response. You are either up very late or very early :)

Andy
 
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Martin Wynne

Admin
Location
West of the Severn UK
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Please do not send requests for help direct to me via email.

Post your questions on the forum where everyone can see them and add helpful replies.
You are either up very late or very early :)

I've no idea. During lockdown life doesn't fall into 24-hour chunks any more. I've just had my main meal of the day. I also like to watch your CNN news these days, so that puts me 5 hours behind the UK.

cheers,

Martin.
 
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AndyB

Member
The foundry finally got around to casting a sample for me.

Screenshot (11).png


I'm still not entirely happy with it but I think I now know how to get the best out of the tool. Of course a lot of this is completely academic. Much of this detail is beyond the resolution of the printer at 1:76.2 scale but it's interesting to see what the tool can do. This is built from five quite basic sub-components and the tool does most of the hard work to combine them into something that looks like a casting. (The surface was about as close as I could get to rusty cast iron in an hour or so.)
 
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