A different assembly method?

[Phil G]

It's rather wasteful of resin because it is simply a straight export from the templates without any bunching or bulk printing. For each chair I added the matching loose jaws alongside it by shifting the template by one timber-width and changing the chair settingsroertype

Hi Martin,
Thanks for posting the STL file I have been looking at it for the last thirty min or so mainly around the comment you made above. Not so much the wasteful but the "it's simple a straight export," which it is, it's also the most accurate way of correctly spacing the chairs to the Templot work in hand. This got me thinking the raft is in fact a sort of automatically generated brick for chair spacing.

Which then got me thinking is there a way to link rafts in the same way your linking bricks to correctly space them.

Then it really struck me. Our current thinking is build plug track the same way as the , prototype. IE timbers first, then the chairs which plug into the timbers and the the rails which clip into the rails.
This is great idea, because like the prototype it uses the length of the timber via the plug hole to accurately gauge the track.
What if we thought about this a little left field!!

To try and explain this I will use this analogy, though clearly not always total correct.
if we assume a straight road with a simple turnout, and we try to turn this into basic X,Y Z cartesian terminology, we could say the X axis is represented by the direction of the train, therefore the Y axis is representing the track gauge and doing the job of the gauge spacing via the timbers, the Z axis is creating the height of the rail above the timber. So the issue is what to use to create the correct X spacing of the timbers!
Typically the timbers have had a dummy connection between them to do this job IE your FDM timber brick.
What if we though about this from another angle, the timbers still create the Y axis spacing for the gauging, but we then use the 3D resin raft to correctly space the chairs in the X axis. Next and this is the change in though process. we use the rails to locate the chairs
by sliding the rail along the raft before the chairs are cut free, Here the raft also becomes the Z height reference. I would propose at this stage a mixture of lose and fixed jaws is the correct way to go, fixed jaws where its as simple as slide the rail along the still rafted chairs. Then lose where any bends or knuckles make this in practical. Clearly this can't be the width of the track and it does not have to be, only the length, At the vee the width of the raft can be set by what is practical, but your STL file is close to being right.
So now we have a sub assembly of chairs correctly spaced apart and held in the right place by the rails,
maybe a few small blobs of cyno, or your old paint idea on a few chairs holds it all in place. Next we cut the raft free, which means we now have full access to the underside of the rails if required. next we position the timbers over the template to get them roughly right and then slowly from one end to the other start to push the plug of the chaired sub assembly into the timber sockets, on the other side we simply repeat the process. This idea would also work very well for switch rails and check rails.

The plus sides are no need to space the timbers in the X direction, quite easy to hold and slide the rails on the chairs, meaning both lose and fixed jaws are easy to consider. you can access the understand of the rails with ease. The downside is slightly wasteful resin use, but not wasting either FDM or plywood as there is no no need to keep the timbers spaced at all.

The trick will be finding a practical way to join rafts together. My first though was a sort of a part chain link idea, where the two rollers would be simple pins the spacing was the pitch of the chain and the rafts would need nothing more then a register hole to allow the pin to engage in, two separate pin links at each end of each raft this would allow for connection and factor in curved turnouts. this idea would allow the rafts to float in the Z axis and the rail would do the job of correctly positioning that axis as you pass the rail though.
Thoughts?
Phil

 

[Martin Wynne]

next we position the timbers over the template to get them roughly right

@Phil G

Hi Phil,

Where do these loose socketed timbers come from? How "roughly" positioned? How are the timbers subsequently fixed in place, if they are free to move as the chaired rail is attached to them? How does this process create accurate curve radii, transition curves, angles and alignments across template boundaries? How would it work in the middle of an outside slip, say?

It's great to have fresh thinking, but I'm struggling to see what advantage this process would offer over existing methods? It seems very fiddly to handle if nothing is actually fixed down apart from the paper template.

You can do it all now if you want to try it. Just switch off the webs and flanges in the FDM export, or the nibs and snibs on the 2D export for laser:

it's also the most accurate way of correctly spacing the chairs

Not after the raft has curled up it isn't. The ones I made yesterday are now nicely curved, and will be more so tomorrow. Looking back through my stock of rafts over the months, I can't find any that are still flat.

cheers,

Martin.

 

[Phil G]

Hi Martin,
On reflection your quite right, I had assumed the rails where fixed and not flexible, but they are. So we do need the timbers to be rigidly held in the correct place and can't rely on the rails to do that job. It may still work as a sort of assembly Jig for Vee crossing but as you say may also be fiddly than advantageous.
Good thing I ask
phil