Vacuum forming clear Styrene?

[peteski]

But if that canopy had, for example, a recess in the shape, it would just span it, never forming into the depression.

That is when vacuum forming comes to the rescue. 

[peteski]

Craig, if the glass areas are either flat or simple curves then I really like Skibbe's idea of just using the window tint without any backing. It is very thin and it will look like true scale glass (Not like the distortion-causing coke-bottle-glasses type of windows often seen in factory-made N scale models).

[craigolio1]

I thought about that. It is a very good idea. Except that then I need to build a body shell that able to support the tint vs the body supporting the tint. In that case etching would be the best route and that's not something I can afford right now. As it stands I have everything needed for plan A.

Craig

[peteski]

As it stands I have everything needed for plan A.

Craig

Well then - go 4 it! 

[svedblen]

But if that canopy had, for example, a recess in the shape, it would just span it, never forming into the depression.

True, that is bound to happen. I guess I was just thinking about Craig's case, where there is no recess.

That is when vacuum forming comes to the rescue. 

Is it not a risk that the recess would just be spanned in this case also, the access to the vacuum being blocked as the plastic forms arond the rest of the body? And that you would need one or several small holes at the bottom of the recess, through the forming body, to where the vacuum is created? Just wondering?

[peteski]

True, that is bound to happen. I guess I was just thinking about Craig's case, where there is no recess.

Is it not a risk that the recess would just be spanned in this case also, the access to the vacuum being blocked as the plastic forms arond the rest of the body? And that you would need one or several small holes at the bottom of the recess, through the forming body, to where the vacuum is created? Just wondering?

Yes, the vacuum-forming dies have small holes allowing the air to be sucked out from recesses or sharp undercuts. You san sometimes see shallow "ghost" impressions of those holes in vacuum-formed nests for N-scale cars.

[craigolio1]

Well then - go 4 it! 

I'm going to!!  ....try. Now to figure out this Silhouette cuter.

[svedblen]

Yes, the vacuum-forming dies have small holes allowing the air to be sucked out from recesses or sharp undercuts. You san sometimes see shallow "ghost" impressions of those holes in vacuum-formed nests for N-scale cars.

Thanks Peteski. Eagerly awaiting Craig's next move 

[CNR5529]

Does anyone know of an appropriately Budd shade of green tinted plastic sheet, preferably .010 think? Pikestuff used to make some sort plastic material, but it was too thick IIRC. I thought about movie industry 'gels', but my guess is probably too thin and poor likely hood of finding the correct colour.

I have used theatrical gels for tinted windows in the past, and it works very well. The gels are available in every possible colour and level of diffusion, so you can model anything from nearly black tinted windows, blueish-green windows, windows that you can see clearly through, windows that are nearly impossible to see through, etc. They are very thin and flexible, and can easily be laminated to existing glass, or used directly as the glass itself (even laminating a few layers together to get a bit more rigidity).

This tool may help you find the right gel number, http://us.rosco.com/en/mycolor. The side/roof windows of park/skyline car domes which are only curved along one axis will not be a problem with gels, just like the black/grey tint on the Rocky Mountaineer Ultradomes. I don't know how well they will work at the front and back of the dome section though, because of the compound curved glass panes.

The other thing to consider is that gels are designed to take the intense heat from stage lighting fixtures, so forget trying to shape them using heat. They just burn at a certain point.

[craigolio1]

I did some experimentation today and I'm not sure it was a success but I learned alot.

Materials:

Pop bottle
Blow torch (don't have a heat gun just yet)
wooden form I have been inserting into the Ultradome model for strength while sanding
5/8 wooden dowel made to fit neck of bottle with electrical tape
piece of 2x4 I'd drilled a hole in for the dowel to got through and support the wooden form.

First off I had two things going against me.  I have a blow torch which is too hot and doesn't heat enough of the area at once, and it's -17c outside in my garage (I figured melting plastic was best done out doors).

Observations:

 With a rectangular form, vs the smooth curved form of the aircraft canopy, the ends are a problem.  Getting the plastic to shrink down on all four surfaces at the end (end, roof, and two sides) didn't really work.

Pop bottles aren't long enough for an 85ft passenger car.  You have to jam the form so far in that it's starting to go into the neck of the bottle.  There is a ton of tension on the plastic at the neck end of the bottle, and almost none at the cut off end.  Also there isn't really enough material to cover the end of the model at the open end of the bottle.  Because nothing is pulling down on it.  When it shrinks it pulls back, instead of laying down over the end.

Conclusion:

I need heat gun and a heated garage.  As far as the model goes, I need a longer bottle and a way to pull down on the open end of the bottle.  I'll head down to the Portuguese bakery.  They have taller 1.5L soda bottles.   As far as the issue of the open end and getting it to shrink over those 90 degree corners on the ends? I'm not sure.  I'm thinking vacuum forming could be the best option here. 

Craig

[Lemosteam]

@craigolio1 , yours would be my plan except for the two sided tape.

As for forming the ends, I think you will run into issues using either process because the material will try to "gather" at the corners of the form, just like when drawing metal (or tear at the top because the material becomes too thin).  Maybe RP ends with a recess for the "glass" form which would be cut straight at the ends.  Then wrap the styrene past the entire length and trim off excess using the edge of the RP end as a guide (instead of trying to perfectly align the wrap).  Or trim close and on a flat surface with sandpaper, remove the overlap until flush.  Pencil marks in the exact center of the wrap and the ends would help center the wrap to the model centerline.

[peteski]

First off I had two things going against me.  I have a blow torch which is too hot and doesn't heat enough of the area at once, and it's -17c outside in my garage (I figured melting plastic was best done out doors).

I wouldn't worry too much about the fumes.  Fumes are really a factor when burning plastic.  There might be some fumes present when the plastic is in a liquid state (melted). But you are just softening plastic (it is not even melted), so if there are any fumes, it is very little.  If you are worried, I think you would be still ok working indoors with some active ventilation (like in a bathroom or kitchen with an exhaust fan on, or in a room with a fan in a window.

But those recommendations are for using heat gun. With a torch I think doing it outdoors is a good idea - the probability of ignition is high.

[craigolio1]

@craigolio1 , yours would be my plan except for the two sided tape.

As for forming the ends, I think you will run into issues using either process because the material will try to "gather" at the corners of the form, just like when drawing metal (or tear at the top because the material becomes too thin).  Maybe RP ends with a recess for the "glass" form which would be cut straight at the ends.  Then wrap the styrene past the entire length and trim off excess using the edge of the RP end as a guide (instead of trying to perfectly align the wrap).  Or trim close and on a flat surface with sandpaper, remove the overlap until flush.  Pencil marks in the exact center of the wrap and the ends would help center the wrap to the model centerline.

That's a good point about the corners at the ends. The ends on this model need to be scratch built anyway. They are not part that of the wrap and one has a balcony. They will be pretty simple to make out of styrene. I was planning to glue them into the ends of the vacuum formed glass and overlap the sides as you suggested. It might be better to make my form a little long, then cut off the distorted ends leaving the useable sides and roof.

Marking the center is a good idea too. I was out for run this aft (I do my best problem solving while running) and I was thinking if I'm pre paint the sides it's very important that I get laid on right otherwise the stripes on the side will be crooked.

I wondered if it might be better to do the sides as two sides meeting in the middle of the roof. This way I can line them up starting at the bottom making sure I get them nice and straight. There will be a joint on the roof which can be dressed, filled and sanded. Then I mask the windows and spray just the roof.

Craig

[craigolio1]

I wouldn't worry too much about the fumes.  Fumes are really a factor when burning plastic.  There might be some fumes present when the plastic is in a liquid state (melted). But you are just softening plastic (it is not even melted), so if there are any fumes, it is very little.  If you are worried, I think you would be still ok working indoors with some active ventilation (like in a bathroom or kitchen with an exhaust fan on, or in a room with a fan in a window.

But those recommendations are for using heat gun. With a torch I think doing it outdoors is a good idea - the probability of ignition is high.

Good to know. I am well aware the torch is probably the worst way to do this. It's what I had and I wanted to play.

I'm currently canvassing friends to find out who has a heat gun.

[craigolio1]

Oh, and what is the problem with using two sided tape to attach the sides? Obviously I've never done this. I'm interested in learning from my mistakes by obviously avoiding them is much better!