96 replies to this topic

[edscars]

While this might be a lot more difficult than it's worth, the primer for polypropylene should be based on chlorinated polyolefin (polypropylene) such as this one:

 

https://www.eastman....olids in xylene

 

If you're tempted to try this, I'd suggest contacting Eastman first to make sure this particular grade will work well with polypropylene, since I've forgotten if this is the right grade or not. You could also ask them if baking on the coating is necessary with this grade, but I think it is.  I worked with some of their products in the '90s.

 

Basically you'd use a spray gun in a well ventilated area and apply a thin layer to your plastic part and let it air dry to flash off most of the solvent, and then bake it at around 180F for 30 min. to get adhesion.  Then you can apply a regular paint over that. When it's done right, such a coating will pass the tape crosshatch test, which is making a crosshatch grid with an x-acto knife with about 1/8" squares on your test part, then firmly pressing on a piece of masking tape and then pulling off the tape quickly. A success is when none of the coating is removed by the tape.  Any other paint over polypropylene will come off in sheets with this test.

[Martin]

Thanks for that Ed, a bit too involved for me. I have 2 other Spitfires that have been painted decades ago and the paint is still there just fine. Can I scrape it off? Yes. How do I fix that? Dont scrape it off.

 

If I like all the mods I plan to do, maybe I will make a rubber mold so I can make them in a more paintable material. Maybe this is the better approach?

 

Front air dam or not that's the question I have now?

 

Here are the painted cars (one painted yellow the other gold)

The photo shop car below of a proposed front end, comments welcome.

Remember this last pic is just photo shop the front mod has not happened.

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[olskoolslotz]

Since this GRC post popped back up here's an article that I found dating to 1966 on the GRC Spitfire. Interestingly the slot car originates from California and this article is from clear across the country in Florida.

I also located an article from April 1965 stating that at that time GRC was the supplier of tires to K&B.

[Martin]

Its a revolution I tell you, unbreakable slot cars.... and the track owner says " hang on just a minute, maybe just for rental cars?''

 

Great find Dave, thanks for finding and sharing this.

 

How about this for a grid, Thanks Don for finding this pic.

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[Bill from NH]

Modifying an original body & using it to make a silicone mold sounds like a good idea with fewer problems. You should be able to cast 30-40 bodies before the mold deteriorates & casting resin is very paintable. 1/32 guys do a lot of casting, 1/24 not much.

[Martin]

I agree Bill, one thing I will loose is the integral chassis design. But I can't have both.

 

I have some more testing on scraps. Hopeful that I can use a combination of CA glue and Tamiya putty to get a paintable surface. 

 

Give me your thoughts on whether to do a front nose job, something like the photo shop pic?

[Bill from NH]

I like the nose job because it makes the overall body look updated & less of a cut & paste project. It certainly isn't mandatory. Your photo of stock Spitfires with simple paint jobs, logos, & numbers is a big improvement.

[Martin]

Playing around a little more.

 

The square radiator outlet did not look correct to me so I melted some scrap GRC onto the back edge to make it rounder.

 

I laid a some masking tape across the nose to simulate the wider nose, very Harvey Aluminum ish.

 

Moving to the back, I would like to soften the rear box, more aero.  

 

BTW the brown stain is PVC primer, just seeing if that helps the bond.  If it does help,it will be PVC primer then CA then putty then Primer then color.

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[olescratch]

Thanks for that Ed, a bit too involved for me. I have 2 other Spitfires that have been painted decades ago and the paint is still there just fine. Can I scrape it off? Yes. How do I fix that? Dont scrape it off.

 

If I like all the mods I plan to do, maybe I will make a rubber mold so I can make them in a more paintable material. Maybe this is the better approach?

 

Front air dam or not that's the question I have now?

 

Here are the painted cars (one painted yellow the other gold)

The photo shop car below of a proposed front end, comments welcome.

Remember this last pic is just photo shop the front mod has not happened.

   The photo-shopped image reminds me of a hammerhead shark! 

[edscars]

I see from Dave's posted article that the Spitfire plastic is something called Celcon acetal, which is somewhat related to delrin like some slot car gears are made of, so that's what any paint or glue would have to stick to.

[Bill from NH]

Some motor endbells were made of that plastic too. 

[Martin]

   The photo-shopped image reminds me of a hammerhead shark! 

It did me too John, that's why I scaled it down and imagined it more rounded and less blocky,see pic below.

 

At least I did not put eyes at the ends of the hammer.

 

That's the stuff, Celcon acetyl, love it or hate. It does melt nice with a wax pen. So I am practiced with that.  I can add, subtract  and move it around at will.

 

Having fun with it.

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[Eddie Fleming]

I prefer the hammerhead version only without the half moon cutout in the rear fin.

 

Just my opinion and it is not my project. Carry on have fun.

[Martin]

Your thoughts are always welcome. One of the limitations (unless I cut up another body) I have no Celcon material to add. So I am moving it around, relocating the parts.

 

I did try to melt Styrene to the Celcon. It looked good for a minute, then I tried the flex test, and it snapped with ease

 

What I can do with the front fin is cut a vertical, in-front of the front axle then warm at the hinge point and bend out to form a wing-let.

 

Working on the back first to see if I can narrow the rear, should be good for a few more MPH.

[Martin]

A bit of progress today. Got the rear end rounded and the front wing-lets mocked up as if I were to use the material available.

 

 

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[Martin]

A bit more progress.

I used the material that was there to create the wing-lets but had to find some more material. So I cut the rear panel, I will add exhaust and screen later. I do like that I was able to narrow the front intake while adding the wing-lets.

 

I do not have a windshield for this car, and was considering a modern F1 halo? What do you guys think? 

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[Martin]

While waiting for a friends broken body to arrive so I can salvage some of this type of plastic to make more mods.

 

I jumped ahead to make a brass motor mount.

 

lots of advantages to this new design. see details here Post 35...http://slotblog.net/...chniques/page-2

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[Martin]

I know we have discussed the factory colors but then I saw these. A black and a baby puke brown. (goldish tone)?

 

P mentioned he had seen " white, yellow, blue, red, yellow with gray marbleized, green, black, purple and a gold-ish tone."

 

These were rental cars, as a many were. Pismo Raceways is where these lived there working life.

Funny little detail, they all 3 have a nut and bolt with a wire soldered to it. Not sure what it's purpose could be. Any guesses ?  

 

 

 

[edscars]

The middle body might be the standard common yellow one that has somehow darkened unevenly over time. On the screws, maybe an unsuccessful attempt to secure the windshields, but that wouldn't explain the wire you mention.

[Martin]

yea Ed,  I thought a it could be a yellow that lived in a toxic environment, but that would have effected the white also you would think?

 

My main interest was the black one, as I had never seen that color. Pretty rare I would say.

 

As for the nut and bolt with the wire soldered to it. Could it be a way to power some kind of light?  Somebody had a reason to add the wire, and all 3 have been soldered on.

It would be great to hear from someone that drove these at Pismo Raceways.  

[Mad Mark]

Perhaps a primitive drop arm down stop since there doesn’t seem to be much metal to solder anything to? or maybe the drop arms where wired solid just using old lead wire laying around?

[Martin]

That's a good guess Mark. I will look on a complete car as do not recall the arm falling. Just remembered the drop arm has a built in down stop behind the pivot.

 

I just check a complete car and the drop arm will only drop about 3/4" then it hits a stop just behind the pivot. Not to say they may have wanted to be less drop. Maybe to stop it getting torn off in a wreck?