Lexan molding tips and things

[Dr. Robotnik]

Hi all,

I am fingers crossed getting sent an original radio box lid for the Hobby Products nitro 1/8th car I found at the junk shop.



This came about because I asked the owner of one if he would take a mold for me and send me the mold so I could make a repro. He said he'd rather send it to me to mold!!!



The part is the clear lexan lid on the yellow box. My question is how can I make a mold from it and return it to him in the same pristine condition I receive it? Can you let me know the names of molding plasters (or whatever the correct term is) and release mechanisms so it'll be perfectly preserved.

Thanks a lot in advance.

Cheers

Ed

P.S. I have also found a 1/8th Porsche shell to suit this car and hope it'll be a fun restore with a little cleaning!

[Tadracket]

On a part that simple, I poor it with plaster of paris and let it dry for a while. Not a great mold for thin pieces as it is brittle. Make sure you mix it properly if you go that route for the best strength.

I am sure someone here has a better method. I tried fiberglass jelly with a driver figure an it was a pain trying to get it to release. But I did not use a release agent either. I am still learning stuff and need to get my garage cleaned so I can set everything back up and start making stuff.

Sorry I can't be more helpful. Good luck.

[templeofspeed]

Wow, glad you're going to give that beast some TLC... I figured you would've binned it by now...

[/sarcasm]

[Dr. Robotnik]

As for plaster of paris as suggested by Tad, I used it when I was a lad on a Hornet shell and couldn't get it to release so I'd need more info. on some sort of release agent before I try that again...

Hmm is the sarcasm thing going into rc10talks long running list of jokes along with Vera, 4000 white parts, etc, etc...at least I've finally made it I guess

I think if I replace the hardware on the car, a new shell and give it a clean you'll be surprised how good it will look. I am sorely tempted to run it in the end too (although I'll have to work out how a nitro engine works)!

[Tadracket]

There are several release waxes available on the market. Google it and you should get a bunch of stuff. I have never had a problem though with lexan releasing from P of P.

If you go with the wax, make sure it will not scratch the lexan. I have heard of people sprinkling the lexan with baby powder. Never tried it though.

[templeofspeed]

It's certainly been run before, I'd sure give it a rip around the yard.

[Halgar]

Interesting find and motor configuration. Curious to see if you'll be able to breath some life back into that thing (the motor, not the rc ).

[Dr. Robotnik]

Interesting find and motor configuration. Curious to see if you'll be able to breath some life back into that thing (the motor, not the rc ).

I am not sure whether the motor might be shot, the exhaust bolt mounts are cracked and stripped, but if it can run without a manifold I don't see why not...it's hard to say what is missing on this car though as I don't have a manual and haven't had a 1/8th nitro before...we'll see I guess.

[Tadracket]

.....but if it can run without a manifold I don't see why not...

Don't know if that will work or not. The back pressure created by a manifold helps the 2 cycle engines operate properly. I know with my old dirt bikes, they would not run without the exhaust connected.

If you can get it running, don't expect any real power as the pipe is what creates that lovely 2 stroke "Power Band". If you listen to Shodogs video of the 5B, you can here the car "getting on the pipe" when it reaches that optimal RPM where the exhaust creates the perfect back pressure for the motor.

I think I did a poor job of explaining this. Maybe someone with a more intelligent mind can do it .

I found a link that cover expansion chambers pretty good.

http://www.motorcycle.com/how-to/how-twostroke-expansion-chambers-work-and-why-you-should-care-3423.htm

[Dr. Robotnik]

The back pressure created by a manifold helps the 2 cycle engines operate properly. I know with my old dirt bikes, they would not run without the exhaust connected.

Yep that's what I thought to but never having run a nitro car I didn't know if they were the same or not...oh well I'll just ebay a new pipe I guess...

[templeofspeed]

Scale two-cycle nitro engines have been successfully run without manifolding for a looong time.
Loud=fast.

Old tether cars, airplanes, boats... No worries for a test.

I would strongly recommend a complete disassembly of the motor to inspect for corrosion and to degum the works, etc. Nitro fuel is largely alcohol based, which attracts water...and the nitromethane is corrosive...

Alternatively, if it came down to it I'm sure a period .19-.21 engine can be found in the usual places.

What engine is on that, OPS?

[Dr. Robotnik]

What is the best degumming thing to use on this car, engine and the alloy parts, I was just going to go for petrol and a soak then try scrubbing it off.

I think the engine is an OPS .13

I have been told to look at Webra Speed 20, OS Max 21, Enya car engines 19-21 if I can't get mine to work...

[templeofspeed]

Straight petrol or white spirit (lacquer thinner?). Clean, dry, spray with WD40.

[SoloGraphix]

Nitro Clean is what I use to clean all my nitro engines. It is readily available at any LHS and cuts thru nitro gunk with relative ease. I recently got a NitroDS with an OS .12 CV that was locked up solid from build-up. A quick disassembly and thorough cleaning with Nitro Clean had then engine screaming when it was put back together and started.

[Dr. Robotnik]

ooooooohhhhh Nitro clean huh? I'll have a look at my LHS asap

Thanks for the tip mate.