Vacuum forming

I have some one-piece vacuum-formed O scale bathtub gondolas that measure @12½ x 2½ x 2½ so the Marx size should not be an issue. They will need some internal strengthening.

@Forty Rod posted:

I have some old Marx domed passenger cars and the domes have discolored, sagged, and warped so badly that they are not usable.  I know nothing at all about vacuum forming, but from what I have read it seems this could be a source of new tops.

The only issue might be the sizes.  These are going to be about 1" high, 2 1/2" wide, and up to 9' long.

I need more info and would accept the cost if someone is already doing this sort of work.

Thanks.

Tom,

Could post a photo of what you have vs. what you need?

Thanks!

I'll try to get a couple of pictures.  If vacuum forming is too fragile would 3D printing be a better option?

My experience with vacuum forming is limited but I think it could work. I'm not sure how common it is for people to have vacuum forming machines but I guess I never asked around. I'm also imagining a vacuum former we used in a foundry for making signs. I don't know if that's the kind you're talking about.

3D printing is a likely candidate too but you'll need a drawing. I'm not sure if the dimensions you gave mean it's literally a simple dome or if it's a dome with little details and whatnot. A picture would be a good start here.

I think something can be done! Just a matter of some sorting out the details.

@Forty Rod posted:

The only issue might be the sizes.  These are going to be about 1" high, 2 1/2" wide, and up to 9' long.

@BillYo414 posted:

3D printing is a likely candidate too but you'll need a drawing. I'm not sure if the dimensions you gave mean it's literally a simple dome or if it's a dome with little details and whatnot. A picture would be a good start here.

I'd suspect that 3D printing is likely to be prohibitive in price for something that size.  Then there's the issue of how smooth the resultant product is unless you use a high quality SLA printer.

FDM printing on the left, SLA printing on the right.  Note the smoothness of the SLA prints.

It is pretty easy to make a vacuum form setup.  I made one years ago for some motorcycle parts.  It just used a shop vac and worked pretty well.  It think it would be a great option for your application.

You would need a good roof to make the mold, right?

@gunrunnerjohn posted:

I'd suspect that 3D printing is likely to be prohibitive in price for something that size.  Then there's the issue of how smooth the resultant product is unless you use a high quality SLA printer.

I most definitely read 9", not 9' haha 9' is going to be a stretch without the fancy new infinite z-axis printers. What's the minimum curve on that passenger car?

The part could be sanded if it's simple enough. That would alleviate FDM trouble. But I'm not sure I'm picturing what he's looking to replace. SLA will totally make a smoother print.

I just gotta praise the FDM because that's all I have at the moment

I just found three coaches without domes and think I'd rather go that way.  Domes are not quite right for my layout.

Thanks anyway.

Tom

Guess you have checked with the long time Marx source in Cleveland area?  He might be making or have made those?  I don't have info handy but he was on the web.

I would refer you to the Kenner toy company's "Vacu-Form", circa 1965.  Perhaps it would help.

I had one.

I can still remember that melted plastic smell on Christmas morn, and the second degree burn on my thumb, while my sister was busy making burnt brownies in her Easy Bake Oven.

The Great Garloo was much more fun.

Mannyrock