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Picture of Custom Car Bubble Top
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Final McFarland cover art_12-28-2015.jpg

One of my bucket list projects has always been to build a reproduction of Ed Roth's magnificent Mysterion show car. To make a short story long, he built it in 1962, showed it for a couple years, sold it to fellow custom car guy Ray Farhner in about 1966. Ray showed it for a year or so but the car was so poorly built the frame kept breaking just hauling on a trailer to shows. It was mercifully destroyed in 1967, never to be seen again. Revell made a model kit of the car and Mattel made a Hot Wheels version. It is undoubtedly the least documented, most famous car of the golden era of car customizing. Above is the magazine cover that made me fall in love with the car and the second photo is of the reproduction I built, finishing it in 2016. I even wrote a book about the car and my project!

This instructable is on how a bubble top is made for one of these show cars.

Step 1: Designing the Top

Picture of Designing the Top
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Of course the first step is to design the top. There is very little information in the literature on the car. Fortunately Revell produed a plastic model kit of the car. Under close scrutiny, the model is not very accurate in key details but it is a very good reference for scaling major parts of the car. It is an accurate 1/25th scale. The top base outline is very accurate from my investigation so I used it to draw that shape. I did scrounge some very useful photos of the real car. The photo above shows how I was able to get a very accurate profile design by extracting a couple key dimensions from the model kit, transfer those to the photograph, then scale the rest of the critical dimensions.

Dumbphone1 month ago
Fantastic job on the bubble tops. This is a cool tutorial. Thanks for sharing.
OldMoparGuy10 months ago
Most cities have a big sign company that will often have a vacuum forming machine. Vac forming machines already have heating coils in the top, allowing the correct heating to be easily seen when the plastic sags down the correct amount. You don't need to use fabric or blow cold air on the part that may be alot easier to deal with the end product. The issues with polycarbonate (Lexan) or acrylic (Plexiglass or Perspex) plastic are true, no matter what technique is employed. The secret to reduce brittleness is tempering by reheating it in an oven, at a lower temperature, for a few hours. Makes all of the difference in the world! I have used this on dozens of 12" x 30" polycarb and other plastics, that I added holes and trimming after. Flame smoothing the edges is a good trick for stress relieving on all edges.
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spectre_man10 months ago
I'm totally inexperienced with this but curious--and a few poeple who've commented here might be able to clarify, in addition to the original poster. If you have a positive and negative mold, why can't the plastic just be pressed into shape? And how does the blowing work--does it just seal around the edge and then "inflate" the canopy to the shape of a (negative) mold? It seems like the application of compressed air would cool the canopy, making any shape-forming difficult if the molds and pressure hadn't completed the job by themselves.
Willys36 (author)  spectre_man10 months ago
The problem with positive molds is that the surface must be absolutely perfect to achieve the required optical quality. A 'blown' bubble achieves the necessary perfect optics automatically. The cold air impingement could be problematic but as I mention in the Instructable, the bed of the tool is covered with felt which serves to stop the jet effect and spread out the air so it uniformly fills the bubble with no differential cooling.
BigAndRed10 months ago
You don't need the 2ton press to make this. Used to make helicopter screens back in the 80's with similar technique, compound curves in perspex. Hughes 300 and 500 and Bell Jet-ranger. Pitts special biplane and Corby Starlet home built aircraft as well.
Heat the perspex in the oven and remove when rubbery, then its stretched by 4 people each holding a corner.
Sandwich the heated perspex between the male and female parts of the 2 part wooden frame. Clamp the frame with spring clamps and turn on the compressed air.
When the plastic has cooled it was trimmed and edged with a thin layer of fiberglass woven cloth for strength.
Technology hasn't changed much since then.
Willys36 (author)  BigAndRed10 months ago
That is definitely a got t make a top but requires a very accurate male and female mold for an optically pure result. My tops didn't have a mold the shape of the final bubble. All it had was the profile hole of the base of the bubble in a flat sheet of plywood. It needed the press to hold that plane onto the hot plastic then air pressure is blown under the plastic which literally blows a bubble.
Willys36 (author)  Willys3610 months ago
OOPS! Just re-read your comment and see that you did actually blow your bubble, just had a 2-part wood profile pattern. There are guys in the hot rodding community who do it that way but I have only had this experience with the commercial press guys. I still like using the press since the clamping method takes considerably more time from the oven to the air compressor and you only have in the range of a minute or two before the plastic cools too much to blow. You want to blow the bubble with the plastic as hot as possible so there aren't extra internal stresses introduced by stretching cool plastic that wants to be set. You obviously had a system where you got your bubble blown quickly avoiding the induced stresses. The last one I had blown with the press method was not as good as the first two. The guys doing the work were obviously new to the job and took forever blowing the bubble. I was watching and could tell near the end that the plastic was beginning to set while stretching. Sure enough, when I was assembling it into my fiberglass car body, everywhere the fiberglass resin touched the plastic it immediately crazed.
starphire10 months ago
Thank you for teaching me that plastic domes can be made with pressurized air, not just vacuum forming. I always wondered how they did that with thick sheets of plexiglass. Also, I am amazed that the super glue didn't fog the edge of your dome! Usually methacrylate fumes turn clear acrylic powdery white in minutes.
Willys36 (author)  starphire10 months ago
I am absolutely sure the glue would have done a number on the plastic if it got onto a visible spot. I took precautions; first placed the rubber exactly where it was to be on the top then outlined it with blue painters tape on both edges; used the heavy-bodied glue so it wouldn't run; ran a thin bead of glue down the exact center of the 1 1/8" wide rubber section so the glue would squish to the edge but no further. I had to end up making 3 tops before I got my final one so had lots of practice! The glue was never a problem.
ragtoptruck110 months ago
Grew up loving Ed Roth's work and had several of his "T" shirts....I was in Reno NV last year and made a stop at the auto museum.... http://www.automuseum.org/ ...just to see his cars on display there. Anyone with a love for cars should see the museum. Glad to see someone else has the same love for his work, great job....thanks. I do hope you made the frame for the car a bit heavier
Willys36 (author)  ragtoptruck110 months ago
I built a 2x4 steel tubing frame. The chrome side rails are just bolt-on decorations, no structural contribution.
stever_sl10 months ago
I'm powerfully curious - what did it cost to have the 2 clear tops made?
Willys36 (author)  stever_sl10 months ago
I ended up having 3 made. The first two were $446 each. The third one was done several months later and they charged over $700 for it. I should have negotiated better on that one!
BearGFR10 months ago
So the Mysterion was destroyed huh? I didn't know. Small wonder it kept breaking the frame, what with those two Ford 406's and that swiss cheese frame. I actually met Ed "Big Daddy" Roth at a car show when I was a kid. Then a couple years ago, I met his son at the Dallas Autorama.
Willys36 (author)  BearGFR10 months ago
Yes, it was a sad thing. And of course the engines were 390s, not 406s, that was just Roth hype. He soon hollowed out the internals in the engines and trannys to make it lighter but to no avail. And I believe from my studies that it was the little spring perches that kept breaking not the frame rails themselves, although they were poorly braced and probably contributed to over stressing the perches.
Andrews-Design10 months ago
Fantastic work! Ed Roth was a true visionary in the hot rod community! I'm partial to the Mega Cycle myself
Willys36 (author)  Andrews-Design10 months ago
Thanx. Yes every gearhead kid has that one car that hit him square in the psyche and ruined him from ever having a normal life again!
Toxictom10 months ago
Be sure to enter this in the plastics contest.
Willys36 (author)  Toxictom10 months ago

should be there. That's why I posted it!!