Doubling etching for more depth, any current examples out there?

[wcfn100]

Jason, now I understand what you are trying to achieve, but are the entire walkways that thick or just the edges?  That car does look like the MT car (with Delrin walkways).

It the entire walkway.  Keep in mind that it doesn't have as many supports as a boxcar.  On this particular car they are about 7' apart so the walkway would need to be thicker.

As for it looking like the MTL car, if the 10' difference in length still looks the same to you, I won't judge. 


Jason

[wcfn100]

I won't say that's not possible, but that's not the way I've interpreted the drawing.  I'll take a closer look.

Jason

[DKS]

In looking closely at the reference image, I don't think the whole walkway is the thickness of the edges. To my eye, it looks like there's a frame that's nearly twice as thick as the treads themselves, judging by the pattern along the top edges--which appears to be the tread welded into notches. But... I could be wrong; I usually am.



EDIT: Sorry for the absense of the former post; I wanted to add the image blowup to illustrate my observations.

[wcfn100]

That smaller walkway could also be different.  Parts of the drawing a pretty faded around the dome but maybe I can see what's going on.

Jason

[tankcar]

N scale, sorry but I thought we were talking about real model trains. Remember, you can't spell Nothing with an N!

Warmest regards, Bobby

[wcfn100]

SO on the drawing the walkway isn't really detailed as it just calls out for an Apex Tri-Lock of a certain dimension.  But in thinking about it, it doesn't really change how I would try and get the correct thickness.  I'm certainly not going to try solder a wider edge on each side and I don't think I could bend something as part of the etch.


As luck (or the luck you make), would have it, I shot a smaller version of the same tank (16,000 gallon) in Texas a couple years ago.  You can judge for your self if it's all full depth.











Jason

[peteski]

It the entire walkway.  Keep in mind that it doesn't have as many supports as a boxcar.  On this particular car they are about 7' apart so the walkway would need to be thicker.

That makes sense (it clearly shows in the photo you provided).  But in the photo, only the lengthwise pieces are thick. The cross-pieces look to be made from steel rod.

I'll change the tune then: since this is 1:160 of the real thing, couldn't some creative compromise be taken here?    If you made it truly to scale, you would have to model what I described above. That would be tough.  How about making this etching a 2-piece sandwich affair:  the top piece a 0.005 walkway surface (with the grid pattern etched in it), then the bottom piece would be etched from thicker material, in a shape of the perimeter (with the center being totally open). Then solder those pieces together for the look you want.

The other problem I see with the sides of photo-etched material (whether you use a single piece or a sandwich) is that the sides of etched items are not straight - they are slightly curved due to the etching process.  With double-etched parts, there is also little raised rib in the center of the thickness. That will never look like the prototype (which is a perfectly flat surface).

As for it looking like the MTL car, if the 10' difference in length still looks the same to you, I won't judge. 

It is kind of hard to judge the car length from the photo you provided.  I was looking at the overall appearance.

[wcfn100]

The other problem I see with the sides of photo-etched material (whether you use a single piece or a sandwich) is that the sides of etched items are not straight - they are slightly curved due to the etching process.  With double-etched parts, there is also little raised rib in the center of the thickness. That will never look like the prototype (which is a perfectly flat surface).

Which comes back to the original questions that started this thread.  I still think the double etching is the best way to proceed for now.  I guess I'll just have to see how it all works.

It is kind of hard to judge the car length from the photo you provided. 

Exactly. 

Jason

[peteski]

Which comes back to the original questions that started this thread.  I still think the double etching is the best way to proceed for now.  I guess I'll just have to see how it all works.

Even double-etched, you still end up with the side wall looking like this:

[ednadolski]

You're not going to be able to fully replicate this kind of look in 1:160 scale from etching one or two layers.  Etching cannot create a line that is thinner than the metal thickness.

Assuming that the grabiron is 3/4" diameter, that scales to 0.0047 inches.  That would make the etched walkway grid about 0.002", which would be barely visible, not to mention quite delicate and hard to work with.  (Even if you could find an etcher that will do it. and then you would still have to try to paint it)

There was mention of "modelers license" in the other thread, this seems like a case where is dictated by practicality.  Even if you soldered multiple layers (which would be a real trick to do accurately at these sizes), you still would have the cusped edges detracting from the look.  Another side is, how well can you even see the results?   IF you really want that much accuracy,  N scale might not be the best fit.

Ed

[ednadolski]

Even double-etched, you still end up with the side wall looking like this:

Right, and that would be per-layer.   Remember, the etchent eats metal like water dissolves solidified sugar.

Ed

[wcfn100]

Yes I know all this which, again, is why I started the thread.

Before we all get too excited, that ridge in the illustration would only be .0016".


Jason

[Sokramiketes]

Good project.

Remember that the Tri-Lock isn't see through unless you're looking almost straight down on it.  So it gets simplified in N by just the pattern and not full depth holes and can look pretty good.

PPD's guidelines are the fool proof dimensions.  They get antsy with tighter tolerances, but always seem to be willing to give artwork a try once... and then send you the 4-5 attempts to get the timing right with the first batches ate all the way through...  You won't be able to hit scale, as Ed said, but going with fewer verticals would get you close.

[wcfn100]

Thanks Mike.  I had contacted them but the process is slow.  I'm going to send them two drawings, one with smaller holes to add an extra row and see what they say.

I think I'm close to having the project designed as far as how the pieces work together, now it's time to see what's actually doable.


Jason

[wcfn100]

So after a couple back an forths with PPD, I finished the walkway drawing with minimum holes and 'gap' (space between holes) lines of .206mm.  The 'un'-official minimums given we're 1x for holes and possibly down to to .9x for 'gaps', but there's no guarantee those will work.

Still a bunch of pieces to add to the drawing, but at least it's progress.

Jason