1/35 Gas Mechanical Bash

[marc_reusser]

Pat,

In a very basic nutshell; a vacuum form machine molds (forms) heated (softened) styrene, acrylic, buturate, etc., sheet over a mold-form/template/object. The softened material (which is mounted in a clamping frame) is dropped onto the form, and the air is sucked out from under it through small holes in a table/surface (not unlike the surface of an air-hocky table), this then forms/sucks the softened material tight against the form, and when cooled, it will retain that shape.

I am working on modifying one of the old Mattel machines that they sold in the 70's (?) [before all this overprotected child cr**], by removing the very basic, and somehwat inefficient hand pump, and attaching a shop-vac. This should give me strong & constant pressure (hopefully not too much, otherwise I will need to shift to a cheap houshold vac.)



When I get to the point of doing it I will post an SBS of the forming process and results. I first need to make the "postitive" form (the back of the cab) out of wood, over which to draw the styrene.  I also need to make/prep some .010 styrene sheet, so that it will fit into the Mattel clamp system.

Marc

[marc_reusser]

Franck...great pics....just what I needed! Thanks!!

BTW., in your photos, am I correct in assuming that the large hand-lever at the right side is for braking, and that the small lever on the front wall (bulkhead) is for speed control in forward and reverse?

...if not, could you clarify what these levers do?


Thanks

Marc

[Franck Tavernier]

BTW., in your photos, am I correct in assuming that the large hand-lever at the right side is for braking, and that the small lever on the front wall (bulkhead) is for speed control in forward and reverse?
Thanks
Marc

The large hand lever at the right is for braking, and the small lever on the front wall is only for speed control...The reverse lever is in front of the seat...

Franck

[marc_reusser]

Thanks Franck.

Marty, here is another good use I am putting the punch-sets to. This is the joint reinforcing on the underside of a 1/48 scale Tiger tank sponson.  By setting up a simple guide jig with two pieces of styrene attached with double stick tape, I am able to get the edge pattern and holes, by simply sliding a styrene strip through the jig, and punching at the needed locations. [The set on the left is the Waldron "Micro" set, the one on the right is the one from Micro-Mark].



Marc

[Belg]

guys, thank you for the info and I look forward to seeing your creation Marc, Franck thanks for the proto shot it really showed what you were going for and accomplished. Pat

[Chuck Doan]

I remember the Vac-U-Form. And the multi-shop woodworking thing. I used the disk sander from that for years in modelling.

[TRAINS1941]

Marc

Transmission is just a thing of beauty.  You always seem to amaze people with what you'll come up with in ways to do things and to the detail.  Just another outstanding job by you.

Jerry

[John McGuyer]

Marc,

I was the M in MAC Mfg. and we did things with vacuum formers that GE was trying to get in our back room to see how we did it, as they claimed it couldn't be done. If I might make a suggestion on your vacuum former. Make yourself a dump (vacuum) tank and pump that down with your pump. Then use that to form your plastic. When you set the plastic on your mold, you want to shock it into place as fast as possible before it starts to cool. This will allow you to use a weak supply and still get good molding. Also, play with your heat source to get the heat on the plastic as even as possible. You will probably find the emphasis should be toward the outside edge.

John

[lab-dad]

Marc,
Back to the model.
that "fill plug" is still bothering me.
The hex part should be larger than the other hardware and the washer should be almost the same size as the bolt head.
looking forward to the vac form SBS.
-Marty

[marc_reusser]

Very interesting John. Thanks for the info and input.

Make yourself a dump (vacuum) tank and pump that down with your pump. Then use that to form your plastic.

Not youte sure what you man by this.  I don't think I hvae many options, this is the most basic of set-ups. I removed the pump handle/lever and the disk with the seal attached to it (which when when pushing the lever downd created the Vacuum/suction...it was just a single stroke type of event)..that left the short section of tube in which the gasketed disk was located. It is to this tube, that I am planning to attach the shop-vac/vacuum cleaner hose.

Also, play with your heat source to get the heat on the plastic as even as possible. You will probably find the emphasis should be toward the outside edge.

The heating module on these is pretty basic. It is backwards from what I am used to using in the large (real-life) machines. Here the plastic, which is clamped/pinned into swinging/pivoting frame sits above a metal plate area (the herting element surface) wmen the plastic is soft enough (can be pretty well determined by the sag)...the frame is swung over and down onto the form and perforated vacuum platform/surface. Unfortunately as this is really justa kids"toy" there is really no way I can see to create any control over the equality of heat distribution, nor the temp, on the heating surface.

The machines I am/was used to using were the ones that held a large sheet of material in a frame over the forming table, with the heating element being above the material.....then when the material was ready, you tripped the release, and the frame/material snapped quickly, straight down, onto the forming surface. Those had both rehostat control for the heat, and vacuum/suction control.

Marc

[marc_reusser]

Marty,

Give it a chance......I think part of the issue is just the color, which makes it stand out moer prominently. If it still looks bad after paint, I'll replace it.


Marc

[shropshire lad]

 Pedants Corner .

As a complete mechanical ignoramouse I would have thought that if you are going to have the transmission fluid plug at the top there ought to be some sort of dip stick as well so that it is possible to know how much fluid is in there .Making it less likely to be overfilled .
  All the gearboxes on the cars that I have owned have had the plug on the side of the housing making it impossible to overfill .  Of course , on your loco access would be a problem if the fluid plug was on the side of the housing, so it has to be at the top .Don't get rid of it , no matter what Mr.Jones says !
  Just a thought to make your life even more complicated.

  Nick

[Franck Tavernier]

Nick, I have original gearboxes drawings from Plymouth and Whitcomb and the tramission fluid plug is always at the top of the gearboxes...

[marc_reusser]

Sunday I set to work trying to Vacuum-form the rear cab bulkhead....so here is the long & drawn-out process.

First step was to make the perforated .010 styrene sheets that would fit the VF's frame. To do this I used an original sheet of .020 that had come with it when i purchased it.




Next I made the "positive", over which the styrene would be formed, and attached it to the VF's surface using some double stick tape. This was made/milled on the X/Y table, to make sure all sides were parallel and square to eachother. (I made the positive out of 1/4" Poplar sanded to a 600 finish; I would have preferred a wood like Jelutong but used what I had handy.) Extra "suction holes" were drilled along the base of the "positive" to ensure tight and proper forming.



The positive and the styrene were placed into the VF, and the the styrene was heated by the heating element......



....it pretty quickly became evident that the heating element was not going to generate enough heat to do what I needed (IE. soften the plastic enough)....but after a while I went ahead and swung the sheet down over the "positive" anyway.



....The styrene was not having any of it....it refused to pull down more than the slightest bit before it cooled....so I decided to give it a little help using a heat gun......which helped a bit.... but not enough as you can see.



The piece above clearly pointed out some problems with what I was trying to do.

A. The heating element did not get hot enough.
B. The "positive" was too deep and long for the size of the plastic sheet and forming surface.
C. The heat gun needed to be used with care, or it would cause the styrene to curl/deform incorrectly.

This is evidenced by the stress tenting at the corners, and even after help with the heat gun....which caused holes at the corners, and unwelcome "thinning" of the styrene at the bend/edge/

Since my time was running out with this, I devised a veryt quick and improvised sollution.  I merely duct taped the entire VF surface insert with the positive, tirectly onto the shop vac nozzle.....



....I then simply laid a piece of styrene over it, and blasted it with the heat gun....ooooops.....




.....the next sheet was angle cut at the corners (to alleviate an "stress tenting").....and loosly held in place over the VF bed, with some photographic tape.




....this resulted in the three remaining pieces giving me usable formed blanks (shown here after most of the excess has been trimmed)




These blanks were then cut to size and shape, using the "positive" as a backing to hold them true and ridgid during cutting and drilling.




And here is the final rear bulkead with some of the additional detailing.






In the end, aside from the bulkead....which I feel was a sucess....out of this also came some good ideas/info, on how I can quickly and easily make future basic vacuum form shapes, and my own forming surface. I hope to try this some more on future projects.


Marc

[marc_reusser]

Ok...I need some input please from you guys that are familiar these types of locos....what duy you think about this seat option. It is based on the ones found in some of the Jenbachs (I have also seen sim in other locos) the seat is about 18" (45cm) wide x 16" (40cm) deep. There is a piano hinge detail at the back, where the lid/seat top would flip up to access the tool/storage box. [If I use this style seet does it require some kind of bracing underneath...like a diagonal support?] The other seat option I am considering is sim, but without the toolbox, underneath where the seat flips up against the wall if the engineer wants to stand rather than sit.






Marc