Stock Model A frames ??

[Jon Haigwood]

Interested in building some early style Model A (&32?) track nose style Hot rods. Like the type that were built to "go" and not show. Most Kit frames are setup with newer rear suspension such as airbags or coils. Not counting the Revell 29 Ford P/U of which I have already robbed the back spring perch from, are there any body out there supplying frames and/or rear suspension  for "stock" A's ? 

[Ace-Garageguy]

This ancient Revell kit and the several that have been derived from it over the years have the best stock A frames and underpinnings going. You used to be able to get 'em really cheap, 'cause nobody wanted 'em.

        

  

 

The original AMT Ala Kart / Model A double kit and all the derivations over the years have the next best stock A frame and guts.

     

There are passable stock '32 frames in AMT's '32 Ford 5-window coupe and Phaeton (and I think the Vicky too). The frame in the AMT '32 roadster is more blobular with rear suspension molded in.

No kit has a good stock '32 Ford frame and guts. Pretty bizarre considering it is THE iconic hot-rod.

 

 

Edited May 15, 2019 by Ace-Garageguy

[Ace-Garageguy]

The tail end of this thread shows how to easily scratch a buggy-spring rear crossmember if you don't want to cut up good frames. R&M makes springs, and axles too, I believe.

 

[Jon Haigwood]

Thanks Ace, There are a lot of good tips and ideas there, I was considering making my own spring cross member by bending some channel styrene  but your way looks much better. 

Thanks for all the info and how-to's 

Jon

[Flat32]

I have plans to make a computer model of a bone stock 1932 frame.  Have some blueprint references, but will need actual measurements for the K member and the front and rear cross members.  The file is started and when finished will allow me to 3D print them in any scale.  However, 3D resin is not as structurally sound as styrene so eventually I'll attempt to do the frame rails in brass with dies for 1:25 scale.  Would be like American Stamping rails, but in 1:25.

[Jon Haigwood]

11 minutes ago, Flat32 said:

I have plans to make a computer model of a bone stock 1932 frame.  Have some blueprint references, but will need actual measurements for the K member and the front and rear cross members.  The file is started and when finished will allow me to 3D print them in any scale.  However, 3D resin is not as structurally sound as styrene so eventually I'll attempt to do the frame rails in brass with dies for 1:25 scale.  Would be like American Stamping rails, but in 1:25.

This may not have what you need but I will do some poking around tomorrow , I know I saw some somewhere'

[Mr. Metallic]

10 hours ago, Flat32 said:

I have plans to make a computer model of a bone stock 1932 frame.  Have some blueprint references, but will need actual measurements for the K member and the front and rear cross members.  The file is started and when finished will allow me to 3D print them in any scale.  However, 3D resin is not as structurally sound as styrene so eventually I'll attempt to do the frame rails in brass with dies for 1:25 scale.  Would be like American Stamping rails, but in 1:25.

This is a very intriguing project, and based on your recent examples of your 3d work, I'd be very interested if you made these commercially available. Especially if it integrates well with the body/fender parts from Revell. 

[my66s55]

Creating a 3d printable file and printing it out would be a breeze. The problem with 3d printed resin is that it is very brittle and can have small parts break off easily. That problem has been address. By mixing 80% Monocure rapid gray and 20% Monocure rapid flex resin, the part become less brittle and easier to work with. I just printed this 1935 LaSalle coupe frame Monday using this Monocure mix. The frame is 177 mm long. Note how thin the resin will print.

[Ace-Garageguy]

12 hours ago, Flat32 said:

I have plans to make a computer model of a bone stock 1932 frame.  Have some blueprint references, but will need actual measurements for the K member and the front and rear cross members.  The file is started and when finished will allow me to 3D print them in any scale.  However, 3D resin is not as structurally sound as styrene so eventually I'll attempt to do the frame rails in brass with dies for 1:25 scale.  Would be like American Stamping rails, but in 1:25.

Man oh man...a little set of pressed rails in 1/25 would be too cool.

I have a set of American Stamping rails waiting in the wings for a build after I move. A correct set in scale? Damm man. 

If you were to print a set, I know of a filled resin system that was developed specifically to cast press-tools from. It's adequate up to about 1/8" mild steel sheet, so .010" or thinner brass would be no problem. Sheet-wax to cast a matching press die properly spaced from the first one is also available.

Let me know if you want additional info.

[Flat32]

The need for these frames, 1932, Model A and Model T, for the construction of scale model Hot Rods is very apparent to me.  Producing them starts with computer files.  3D printed versions can be adequate, but scale compromises have to be made, mostly for wall thickness.  The actual frames were somewhat flexible  and could twist easily as part of their original design.  In the 1:1 Hot Rod world they usually got boxed in some way.  Getting to brass rails the way I envision them will require steel tooling which I would do with CNC.  That takes tool design work and I think I can do it so that the tool parts can be wire EDM cut with the forming contours electrode EDM cut.  Just takes time and money.

A shortcut might be simply 3D printing molds and finding a way to utilize carbon fiber pre-preg as the material.  The pre-preg would be linear strands only to facilitate loading it in what will be a closed mold open only at the ends.  Need to do a little research here as I don't remember how the pre-preg gets activated and cured.

[my66s55]

Sounds like a plan, Ray. Good luck. You certainly have the printer, skill and ability to make it happen,

[Ace-Garageguy]

52 minutes ago, Flat32 said:

...I don't remember how the pre-preg gets activated and cured.

Heat, while the parts are in the mold.

[mod3l Lover]

   This is great stuff guys, thanks for posting these

little nuggets of wisdom!  I have 6-8 kits in need of

some much nicer 32 rails and cross members, etc.!

 

   So Bill?  When you move, will your address be

something like- Down three, and then right.?

         David S.

 

[Flat32]

Found unidirectional prepreg and the sheet is only .006" thick, perfect.  Cures with 270 degree F heat and the supplier has mold casting resin for the purpose.  Got three planets lined up and only need one more named learning curve.  I'll order some of the prepreg and do a quick finish on my frame rails file.  Then print mold master patterns from which I'll make hydrocal plaster molds.  Just don't like messing with casting resin if I don't have to.

If this process proves successful I can imagine it being used to make the old car bodies in thicknesses much closer to scale sheetmetal than resin cast or injection molded body parts.  Would use open molds, woven prepreg and vacuum bagging method in this instance.

Finding it all here: Carbon fiber source

[Ace-Garageguy]

5 hours ago, Flat32 said:

...If this process proves successful I can imagine it being used to make the old car bodies in thicknesses much closer to scale sheetmetal than resin cast or injection molded body parts.  Would use open molds, woven prepreg and vacuum bagging method in this instance.

Finding it all here: Carbon fiber source

Couple things (I'm trying to help you out here, so you don't waste time and materials):

1) "Unidirectional" has carbon fibers running in one direction only. That's why it's called unidirectional, and why it's only .006" on the product TDS. A woven "bi-directional" fabric using the same tows would be about twice as thick (I'm assuming you're referring to #2114 in the FiberGlast line). It's not woven, but rather has a few knitted-in strands (on the Y axis) of a carrier thread to keep the tows oriented, as well as the sticky uncured resin. It has essentially zero strength in the off-axis. To keep your laminate from cracking along the primary axis almost immediately, you'd have to do another layer of the stuff at a 90^o angle, and you'd have a devil of a time making that happen. Carbon does not conform happily to small-radius curves or sharp corners...like what you'd have in typical model car parts...and its strength just isn't required for model parts anyway...unless you're making something like wing spars or wing skins for flying model aircraft.

RE: ABOVE reference to unidirectional vs. woven bi-directional. Here is a woven bi-directional cloth, equally strong in both axes, using smaller tows, and measuring .007" in thickness. This one is not pre-preg.   https://www.aircraftspruce.com/catalog/cmpages/bigraphite.php?recfer=23781

2) Vacuum-bagging is way overkill for anything on a static model. And with pre-preg, you'd have to keep vacuum on the mold all through the curing process, which requires heat. Bagging parts in an open mold with room-temperature cure resin is tough enough. You have to keep vacuum on the mold until the stuff kicks as hard as it's going to go on its own, overnight usually, and than kill the vacuum before you put the mold in an oven, hot box or autoclave. With pre-preg, you've got to have heat and vacuum simultaneously.

Just FYI, I've been designing and building carbon (and other composite) parts for real aircraft and 1:1 cars for decades, and vacuum bagging is a lot of work and materials. And the bagging materials simply will not easily follow the intricate shapes of the inside of a frame rail in 1/25 scale. Nor will carbon.

I've also been making close-to-scale thickness fiberglass parts for models for almost 10 years, using an aircraft-quality epoxy resin (MGS L285 with 285 or 287 hardener) and several 3/4 and 1/2oz. glass products in various weaves. Open molds, hand layup, no heat or vacuum-bagging required. The finished parts do develop more strength with an elevated temperature post-cure, but 24 hours at room temp is fine for model car parts.

The finished parts range in thickness from .010" to .030", depending on the glass and numbers of layers in the laminate. They are FAR stronger than injection-molded plastic parts of the same thickness, and can be handled and finished with no worries about breakage.

None of the parts shown are as high-quality as this technique can ultimately produce. They are all Q&D development parts experimenting with full-scale technology shrunk down for model use.

Upgrades in the mold-release agents, for instance, will yield an almost flawless surface finish, rather than the slight texture that's visible on the black part below.

 

Some of my results:

 

 

Edited May 16, 2019 by Ace-Garageguy

[Flat32]

The problem I see with the prepreg composite materials is cutting it.  Glass and carbon fiber can't be effectively cut with a razor blade. All things considered for making composite frame rails in a semi-closed mold I'm thinking maybe substituting a silk fabric impregnated with resin and roll sandwiched between PVA film.  This laminated concoction would get pushed into the lower form die with the top form punch and trimmed with a razor at the top of the form die before the resin cures.  While silk wouldn't have the strength of carbon or glass it should be strong enough for the purpose.

I don't think I want to do composite bodies, too difficult for me.

[Ace-Garageguy]

Wow...silk. I never thought of that. Genius.  

I don't know right off hand, but I'd suspect silk is right up there in strength with glass fiber, maybe stronger. Some spider silks exceed the strength of Kevlar, and work has been done to boost its availability by genetically modifying animals to produce the spider-silk protein in their milk (kinda scary really).

Anyway, silk is a great idea. Its finer weave would look much better on the back-side, more in scale, than even the lightest glass fabric I'm aware of, and it should fill entirely with very little primer. Of course, if you use matched molds, the weave wouldn't be visible anyway.

You're thinking right with the razor-blade trimming while the parts are still in the mold, too.

In the industry, it's called "green trimming", and is routinely done after the resin has gelled but not hardened. It's important to hit the sweet spot with the timing, as too early you'll pull the layup out of position on the mold edge, and too late, of course, you can't cut it with a blade and have to wait for full cure to cut it with rotary abrasives.

[Flat32]

Couldn't find PVA in sheet/film form, seems it only gets applied in a liquid form.  Did find .001" FEP film though and ordered some.  Silk turned out to be NOT a simple subject. Probably have to go to a fabric store so I can put my hands on the stuff.

[Greg Myers]

!/24th scale