115 replies to this topic

[Jairus]

Update: If anyone is interested, I got a few good bodies pulled yesterday. The first two are cut and on the paint bench getting lettered. When finished, they are heading out to Ralph in Germany first and I shall post finished pics here later. He has been soooo patient!
After that, one more will be painted for the Gilbert/Sundance build up #2.

8)

[Howmet TX]

Intersting to see your approach to this, Jairus.
I've done a few myself- currently working on a Div 3 spec Lola T70- and find the method that works by far the best, although it does sound like a lot of trouble- though it ain't really- is to take a first pull from your filled & epoxied master, and backpour it in fresh solid dental plaster, as TSRF suggests. You can grind the bumps off the new plaster mould easily while it's still fresh, and get a really good polish when it's fully hardened. Saves a lot of trouble in the long run. In fact, you don't have to bother too much about grinding back the filler in your original mould- cast it bumps and all, and concentrate on getting a good finish on the master mould. The important thing I think is to have the master perfectly homogenous- not made up with bits of 'foreign matter'- filler and primers and stuff that will almost ceratinly detach themselves later on.
Sometimes I prop the body up on a little aluminium frame, rather than go to the trouble of milling out a cavity underneath. I don't have a milling machine is one of the reasons. But normally the underside is rough enough that air flows through and across to all the little vent holes. I made a long skinny drill out of piano wire to sink the vent holes through deep moulds. It's just ground to a arrow head shape- cuts through soft plaster very easily and is disposable, not like the countless 0.5mm drill bits I broke, blunted or lost previously.
Now I'd welcome any more advice about avoiding that dratted webbing effect on square, undercut corners.
I've recently been making moulds out of high-temerature silicon rubber to enable me to pull really undercut shapes, like rolled sills and long tails and nose sections. Works great, but silicon is much more expensive than plaster.
My next project is a '59 Plymouth Fury. I would use silicon, but I don't think it would have the rigidity to hold the tailfins up in the vacformer. I thought of embedding metal stiffeners in the silicon, but the alternative plan is to have my first try at a multi-piece plaster mould.
I have it worked out in my head, but I can see all the pitfalls far too clearly.
Again- any advice welcome!
Sorry to take up space on your thread, Jairus.

[One_Track_Mind]

Now I'd welcome any more advice about avoiding that dratted webbing effect on square, undercut corners.

Hi John,
The webbing occurs on the corners because of too much plastic in that particular place.
when the plastic is hot it forms together,hence giving the webbing.What I've done is place another block of wood,just a few inches from the corners of the mold in where you know the webbing is gona take place.the heated plastic at this point has more to take up over the block of wood,and giving a nice crisp corner. Try it this way,trust me it works!

[Howmet TX]

Great! Thanks Brian- I'm going to try that right away. That's even more I owe you!
Trust me- payback is coming.....

[TSR]

Indeed this is the way to do it. According to Lloyd Asbury who has over 45 years of experience on the subject, the best shape to help eliminate web is a thimble. Lots of them. The conical shape helps to easily knock them off the plastic once molded. Of course those thimbles are cast in epoxy to keep temperatures even. He recommends that the tools be pre-heated in an oven at 200F, and that the plastic sheets be pre-dried in a special oven, a large flat plywood box with hangers for the plastic, with an affixed hot air gun blowing at moderate temps inside the box (don't forget to build an exhaust outlet!).
It really helps ease the pain...

[Ron Hershman]

Indeed this is the way to do it. According to Lloyd Asbury who has over 45 years of experience on the subject, the best shape to help eliminate web is a thimble. Lots of them. The conical shape helps to easily knock them off the plastic once molded. Of course those thimbles are cast in epoxy to keep temperatures even. He recommends that the tools be pre-heated in an oven at 200F, and that the plastic sheets be pre-dried in a special oven, a large flat plywood box with hangers for the plastic, with an affixed hot air gun blowing at moderate temps inside the box (don't forget to build an exhaust outlet!).
It really helps ease the pain...

While I respect Lloyd's expertise..... there is no need or advantage to "drying" lexan material that is .020" or thinner.

[TSR]

Happy bubbles!

[Ron Hershman]

Happy bubbles!

No bubbles here. Don Ho had them all.

[Howmet TX]

Great info here!
Perhaps TSRF would ask the legendary Lloyd how he achieved those deeeeeeep
undercuts and still managed to pull the lexan off the mould.....
Flexible moulds? Multi-part moulds? And what were the Lancer moulds made from? I hope they were cast in some neat metal rather than the crude old plaster I'm messing with.

[Ron Hershman]

Great info here!
And what were the Lancer moulds made from? I hope they were cast in some neat metal rather than the crude old plaster I'm messing with.

Aluminum filled epoxy. Some were two and three piece molds.

[Ron Hershman]

No bubbles here. Don Ho had them all.

I thought Lawrence Welk was the guy with all the bubbles!

Don Ho had all the "Tiny Bubbles"

[TSR]

Perhaps TSRF would ask the legendary Lloyd how he achieved those deeeeeeep
undercuts and still managed to pull the lexan off the mould.....
Flexible moulds? Multi-part moulds? And what were the Lancer moulds made from? I hope they were cast in some neat metal rather than the crude old plaster I'm messing with.

The molds are generally made of Hapex epoxy with a large percentage of aluminum powder filling, plus metal (brass) inserts for fins, spoilers, intake stacks... Multi-piece molds are also necessary to obtain proper and web-free undercuts, but it takes a lot more than all that to produce a decent body. it still is a bit of a black art as soon as the molds have negative draft anywhere. And if the plastic is thick, it gets harder...
And Howmet, green dental plaster is great for small quantities...

[Jairus]

Update:
2 of the vacuum formed bodies were painted today. Unfortunately, like all good things worth working hard for, there are set backs! One of the bodies got a spot of black paint on it (near the number seven on the left body) and will require me to paint another one to replace it.

Oh (h)well!
:|

[Howmet TX]

Thanks Ron and Doc. Very helpful indeed. And Jairus, if you were going to throw that 'spoiled' body away, throw it in a post box with my name & address on it. You know it'll make you feel better.

All the best,
Howmet

[Jairus]

John,
I am honored you still want this even after I screwed it up. I will consider it but my own collection is sooooo small as even this will be a great addition, damaged as it is.

Here I have posted finished pictures of the one good car. This morning I cut and trimmed another body and painted the hand lettering. Tomorrow, the paint goes on. Hopefully by Friday afternoon I can send the two out to Ralph in Germany!
Hey Ralph!







And now for something completely different.....
The motor for the actual Gilbert/Sundance replica:
Adam gave me this antique piece a while back and I have finally turned my attention to it. Turns out it is a perfect choice to power this replica.
The first thing to notice is that this must be an early "C" can motor due to it's lack of rear axle cutout and the ill fitting end bell.




The end bell as it turns out is a narrowed "B" can piece without the upper and lower shims that Lee used. I can fix that!
Also, once taken apart a set of Arco blue dot magnets are revealed to the light, as is a Certus arm! Koooolllll!!!


The arm is unmarked, but compairing it to a 27 double wind I am going out on a limb and guessing that this one is a 27 Single CCW wind. Any other suggestions?

8)

[Larry LS]

That's looking great Jairus. It really does dance in the Sun.

Going back to some vac mold work. I like to see some bodies that have some decent looking stacks molded in, most you see are just some bumps they show as stacks and you paint the top black to look like a hole is in it.

Or others resort to the eyelet treatment by buying some from some where or other. These do look very nice. But many don't want to do that to a car that may get creamed in it's first race and there go the stack works.

So on the bodies I make for ToyTech I make up these brass tube and .062 circuit board inserts. They are not attached to the body. They just sit down in a small depression milled into the body where the engine would be located. The depression has many vent holes to supply vacuum to the stacks.

When the body is pulled they come of the mold with the body as it would be difficult to remove the body other wise. Then you just easily pull the insert out of the body and re-insert it back in the mold again for the next one. The brass tubes are a press fit into the circuit board and do hold up very well for many bodies so far.

A little paint work and they look better I think than the lumps and are durable. They have more of a true stack look than those flat things. YMMV!

[Jairus]

UPDATE:
Victor at True Scale just happened to have a back pour of an actual Kirby 312P! At that point he was unsure what to do with the mold and my begging and pleading has resulted in a PERFECT replica of the Kirby 312P now in my hot little hands!!!
(I cannot believe it!)
The bodies he sent me are of the highest quality I have ever seen vacuum formed! Flawless and in two different thicknesses, .015 and .020.

The next step was to start building the frame. The center section is now complete and this time using the correct 3/32” axles, even though it will require sheeving the wheels. (Lee used a Cobra 32t 48 pitch ring gear and showed how to sleeve it in the 6 part article)


Looks like a kit doesn’t it!


Keep your eyes on this thread for further updates!

[Jairus]

I spent 4 hours last night pouring over issues of Car Model magazine and making drop arm pivots. Got a couple made but nothing else to report and no pictures.... sorry.

[Jairus]

Update time!

Spent the last three hours building up this motor. Aligned brush hoods, broke in under water.... blah, blah, blah, everything by the book!
The arm is a Certus 26 single and the magnets are blue dots.




Complexity compounded by the fact that I built two of these animals at the same time..... second one powered by a Certus 27 double wind, also shod with blue dot magnets, gold dust brushes, shunt wires and insulated springs. Both seem to scream at only 3.5v but have slightly different tones for some strange reason. Didn't expect that... but they both run quite cool so I'm pretty sure there won't be any problems.

Tomorrow I gott'a get back on the iron!

[MarcusPHagen]

The arm is a Certus 26 single... ...second one powered by a Certus 27 double wind... ...Both seem to scream at only 3.5v but have slightly different tones for some strange reason. Didn't expect that...

Nice looking work, Jairus!

The double 27 is similar in resistance to a single 24, so that probably accounts for the difference in tone. It should be revving higher than the single 26, as long as your break-in power supply has the amps to drive it.

Marcus

[Jairus]

Marcus, thanks for the info. That really helps me untangle some the wire size myth...

UPDATE:

The chassis is done! Scrubbed clean with kitchen cleanser and a toothbrush but not polished yet. This way you can see the solder joints just as they are with no sanding or cleaning. I think I am truly getting better each time! But, that maybe just me…








This closeup of the drop arm hinge shows that I finally figured out how Lee did it. I have all the articles except December ’72. That issue showed how to mount the drop arm and bat pans. I have had to study the pictures in later articles and try to figure out the wire size and placement of all the parts. Took some time but I think I worked it out!

[TSR]

Hi Jairus,
Very nice job. Now you need to tie the front axle tubing with thin copper wire (lead wire stuff really) and cut down the axle tubing with the Dremel disk. I am not sure and cannot remember right now if Gilbert did this on that particular car or not.
Generally speaking, the Gilbert chassis were never polished. They were cleaned as you did, then a criss-cross pattern was ground on their bottom with rough (280) wet paper on a block, then the whole thing was buffed with a Brillo-Pad, rinsed and dried, then the hinges lubed.
If you want the exacting look, you need to use machine screws on the motor, a white-color end bell and the can painted in light wrinkle green. I will send you the exact screws with the Shinoda decals tomorrow.

[dc-65x]

Hi Jairus and Philippe,

Are you building your motor as a tribute to the Lee Gilbert CM article? I'm looking at the Blog at work during lunch and the firewall won't let me see your pictures:

[TSR]

Well, I was all wet and was thinking of another motor-building article in... Miniature Auto Racing. Indeed the end bell is black and there are pin tabs on this Car Model-story motor. My error! This leaves the can color as unknown. You see, I did the MAR article with Lee and Bob Green, taking the pictures and making the drawings. I had no participation to the Car model article and my memory failed to register the diff.
So Jairus, the can color can be anything you fancy because no one will ever remember, certainly not... Lee!