52 replies to this topic

[Gene/ZR1]

TSR,

Do you have any info on blow-molding slot car bodies? Or could you do a thread on them?

Very interesting method of making a body.

Thanks.

[stevefzr]

TSR
Do you have any info. on Blow Mold Slot Car Bodies?

Bodies? Plural? The only one I know of is the MPC Manta-Ray. I'm interested to know what others there were.

Regards,

Steve C

[stoo23]

Gee,..one would have to surmise that blow molding, would Not be Cheap !!

Plus I am unsure whether one could use Poly-carbonate materials in a Blow Mold process.

Were Many Bodies actually Made this way ??

[endbelldrive]

I've seen the Tarantula DMX and Mako Shark that were blow molded by a company called Detail Models. A little look see at the 1966 1/2 Auto World catalogue shows them on the top right hand corner of this page at Steve Okeefe's website.
Link to: The Independent Scratchbuilder - 1966 1/2 Auto World Catalogue - page 111

[slotbaker]

Stoo,
Yep, wouldn't be cheap, but blow moulding can mould Polycarbonate (Lexan), Polypropylene, Polyurethane, Polystyrene, Polyethylene, PETG, plus others.

As an example, the comon moulded babybottles are usually made with Polycarb.

Steve, I'm surprised that the Manta Ray was blow moulded. I've got one here that is thinner around the edges, plus at each end, than it is on top. Blow Moulding usually makes the edges at each end of the moulding thicker than the middle. This is due to where the mould reduces in size and shuts off to pinch the tube of plastic prior to air being blown in. Of course, my example may not be a genuine either, so I'm interested to know.

Doc

[slotbaker]

I've seen the Tarantula DMX and Mako Shark that were blow molded by a company called Detail Models. A little look see at the 1966 1/2 Auto World catalogue shows them on the top right hand corner of this page at Steve Okeefe's website.
Link to: The Independent Scratchbuilder - 1966 1/2 Auto World Catalogue - page 111

Bob,
That article appears to be "Injection" moulded bodies.

This is quite different to Blow Moulding (Molding).

Blow Moulding is the process that makes the plastic soda bottle. You can have reasonable detail on the outside, but only wall thickness flow shape on the inside.

Injection mouldings are the same as the model kits where good detail can be made on both inside/outside of the part.

The parts that you have seen may have been clear (polycarb, acrylic, or ?) material injection moulded. The same as the clear parts in model kits.

[vsrn]

Bob,
That article appears to be "Injection" moulded bodies.

This is quite different to Blow Moulding (Molding).

Blow Moulding is the process that makes the plastic soda bottle. You can have reasonable detail on the outside, but only wall thickness flow shape on the inside.

Injection mouldings are the same as the model kits where good detail can be made on both inside/outside of the part.

The parts that you have seen may have been clear (polycarb, acrylic, or ?) material injection moulded. The same as the clear parts in model kits.

Gents -
I think the process used for these bodies was quite different than how plastic soda bottles are made.

I worked in a plant where bottles were blow molded. It involves a 2 part female mold. The halves open, a tube of hot plastic is extruded and hangs down between the molds. The 2 halves close, and air pressure is applied at the top of the plastic, and that blows the plastic into the shape of the bottle.

The blow molded slot bodies were made with air pressure instead of vacuum, forcing the plastic down into a female mold
rather than over the more traditional male mold.

vsrn

[endbelldrive]

Here are some shots of Detail Models' 1/32 Iso-Grifo courtesy of "manitouguy".over at SlotForum. The rest of the thread can be found here.

[TSR]

Steve, I'm surprised that the Manta Ray was blow molded.

It was, and Greg is 100% correct in his description of the process.
Detail Models also made a 1/32 scale Lola T70 and a 1/24 scale McLaren-Elva.

[Tex]

Seein' that Iso-Grifo with it's molded in "bottom" and everything made me realize I had what must have been a blow-molded Gull-Wing Mercedes back when I was probably 12-years old. I never did anything with the body; probably chunked it with the rest of my stuff when I was about 14 or so.

[tonyp]

PDL is this also the company that made a Thingie called the Tarantula? Please do not ask how I know about that body. LOL..

[slotbaker]

It was, and Greg is 100% correct in his description of the process.

Fair enough, as mentioned, my Manta Ray may not be original.
Any idea what material the Manta Ray was blow moulded in??

And yep, Greg is 100% correct with his description of the process.

That Iso-Griffo is a great body.

[TSR]

The MPC Manta Ray was indeed blow molded from white or gray styrene, then painted in gold/silver or metallic red/silver. They also made a few green ones, tough to find.

Detail Models made the Tarantula, a Mako Shark and a McLaren-Elva in the 1/24 scale, a Lola T70 and the ISO Grifo in the 1/32 scale. The Mako Shark body was used by Unique on their very rare slot car model, of which only one boxed example appears to have survived so far.
No other Detail Models bodies were used on known cars or kits. I believe that no other slot car bodies were blow molded.

[gascarnut]

I guess there's a difference between blow molding, where the finished product is like a bottle with plastic all around, and forming into a female mold rather than over a male mold?

Both will put the detail on the outside of the plastic, but using a female mold still uses vacuum rather than pressure, right?

[TSR]

Indeed, but I do not know of a single slot car company that used female molds for forming bodies... because it would not be possible to form undercuts too easily I guess.

[Horsepower]

I have the Detail Models 1/32nd Lola and one of the interesting things about blow molding is the body comes out nearly as hard as styrene. At least, the one I have is.......

[Howmet TX]

I've done a few 'female' vacforms. The problems with undercuts can be resolved in precisely the same way as with a male mould, using multi-part or flexible moulds. The main difficulties I found are that female moulds are necessarily much larger- which is a significant one for my little home-made vacformer- and the positioning of vent holes.
There have to be strategically placed vent holes in the vac mould in order to draw the sheet down into low areas where trapped air would otherwise form bubbles. On a male mould, these can be placed discreetly on panel lines and in vents and intakes. On a female mould, they have to be on the high, exposed parts of the finished shell- roofs, wheel fenders etc.

This is what intrigues me about this interesting thread- how does the entrapped air escape in this blow-moulding process? I can't see any evidence of vent holes in the Iso Grifo shell. Is the whole process carried out in a vacuum? If so, this has to be an industrial scale installation!

In practice, at least in my amateur workshop, I find the detail finish of a conventional male mould is as good as you get with the more problematic female mould, which is still a little blurry, but just 'inside out'. The only use I have for it now is moulding screens and minor parts for use in resin shells and repros, where they have to fit flush with the exterior surface of the shell. Using a male mould you get a slightly oversized screen.

[TSR]

John,
From what I have seen in bottle making, it is just a puff of compressed air, then as the material cools on the mold, the air is let out the same way it came in. There are tiny air holes in the bodies.

[BWA]

Indeed, but I do not know of a single slot car company that used female molds for forming bodies

Eau contrair my good doktooor. ALL the Russkit Styrene early kit bodies in both 1/32 and 1/24 scale were indeed reverse vac formed into female molds.

The Porsche RSK, Lotus 25, Lister Jag etc were all done this way.

OK, what did I win??????

Next question, just ask me anything Eh!

Also, I believe the blow molded 1/24 McLaren was the first MKI organ pipe thingy, and, not an Elva(unless of course they were the same????). I have one, still uncut.

[TSR]

Indeed. I was thinking about clear plastic bodies and completely forgot about the Russkit styrene jobs!
You win nothing but I slap myself silly to get me yet another concussion...

The Detail Models McLaren-Elva is not the "organ-pipe thingie", that one was the ex-Zerex/Penske Cooper-Olds that Bruce purchased from John Mecom and raced until the new McLaren MK1, AKA McLaren-Elva because they were produced by the Elva/Trojan company, came out. The "organ-pipe" car was dark green with a white, then silver stripe, while the MK1 driven by Bruce was black with a silver stripe and an entirely different animal altogether.

Lancer made a body of the original 1962 Zerex-Cooper (to be painted in red as a center-cockpit car), then they made the widened cockpit 1963 version with the Climax engine (metallic blue and white), then the 1964 Cooper-Olds (green). All and the same car, basically a re-bodied 1961 Cooper T53 F1 car.
Lancer and Russkit made the McLaren MK1 but it is seemingly always called "McLaren-Elva" on the body tags.

[ravajack]

Bodies? Plural? The only one I know of is the MPC Manta-Ray. I'm interested to know what others there were.

Detail Models made the Tarantula, a Mako Shark and a McLaren-Elva in the 1/24 scale, a Lola T70 and the ISO Grifo in the 1/32 scale. The Mako Shark body was used by Unique on their very rare slot car model, of which only one boxed example appears to have survived so far.
No other Detail Models bodies were used on known cars or kits. I believe that no other slot car bodies were blow molded.

Ads from late 1965. A complete (?) line of Detail Models bodies:
Four in 1/32 (Chaparral, Hussein, Iso Grifo, Lola) and four in 1/24 (Alfa, Mako, Elva, Tarantula).

MC&T october 1965:


MC&T november 1965:


MC&T december 1965:

[TSR]

I have never seen the Hussein and Chaparral in the 1/32 scale and am not so sure they were ever issued... anyone seen them?

[Ecurie Martini]

I have one of the Detail Models injection-blow molded T 70s and, for comparison, a traditional vac-form example (? Dubro). The injection blow mold has slightly better surface detail than the vac-form but nothing like a typical injection-molded hard body. I don't know if this reflects the quality of the mold or a limitation of the ability of the process to capture fine surface detail.

EM

[Prof. Fate]

Hi

Philippe, I did have one of the Husseins in the day. I still have a T70 somewhere unpainted.

I ran the crap out of the Hussein, but it was too heavy to compete with my normal vac club cars. It was just for amusement.

Fate

[TSR]

Someone shows me a Hussein and a Chaparral and I will believe it.
I have seen all the others and actually there is at least one of each at the LASCM.
The most commonly found are the 1/32 scale T70 and the 1/24 scale McLaren-Elva.