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PostPosted: February 1, 2020, 1:40 am 
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So it looks like I will probably be getting an old Kelmark Doh!, sorry BRADLEY GT on the cheap.
Unfortunately the original doors were "Gull-Wing" type in plexiglass.
Door and side window in one part, with a strong bend. Think of an inverted L
After a few decades they turn to dust.
I plan to put the 1.0 3-Cyl from my Geo Metro into it.
The Metro is a pile, the GT is not a lot better, but with some paint will be decent with a very vintage kit car style.
Primary use is commuter car.
So for winter I will need doors, and some sort of heater, which a water cooled engine should provide better than an air-cooled VW ever did.

I know the basics of forming Plexiglass/Polycarbonate, a form and heat.
Fine, but I need a bit more.
Must the form be stainless or aluminum sheet?
How much heat, will a strong heat-gun work, or must it be done in an oven, IR light?
Cut to final shape before forming?

Lack of good doors is a primary reason why even very nice running GT's can be bought all day long for under $3K, often less than $1,500.

With this engine conversion experience sorted I plan to put a 1.3 DOHC into my Tatum project. :D

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Last edited by RichardSIA on February 1, 2020, 2:54 am, edited 1 time in total.

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PostPosted: February 1, 2020, 2:24 am 
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Did someone say Kelmark?

https://grassrootsmotorsports.com/forum/grm/adding-an-oil-pump-to-a-corvairkelmark-transaxle/162866/page1/

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PostPosted: February 1, 2020, 6:43 am 
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I had a Bradley GT in my teens. I liked the headlight door system but you have to lay down in it because the roof is so low. Uses a full length vw pan.

I don’t think you will have room and access to G10, even with a short back glass. Here is a pic of a hyabusa engine version. I’d look at a rotary or Goldwing with a standard diff and mod the nose to fit a rad where the headlights are like this one.

I’d make doors like these with what looks like .050 sheet steel skin over a ½ inch steel tube frame and glue the sunroof panel in and use universal rubber seals for the sides with the ends at the bottom for drainage.
https://www.youtube.com/watch?v=LlLtnGT6BRo


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PostPosted: February 1, 2020, 6:44 am 
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A few more pics. A jeep cherokee is a great choice for a wide, thick, low profile radiator with high capacity and flow rate. It looks like he may have used glass over wood at the hinge for the doors. The more cross section, the stiffer the door will be.

I didn't answer your question though. You need an oven big enough for the area. I'd build an oven to use inconel wire and a rhestotat oven controls to adjust temp. The oven would be an element the length of the bend area, 3 or 4 inches wide, and located over the 90 deg wood form where the legs are 45 from vertical. The element is heated to the minimum listed temp for the plexi and monitored with a non-contact temp gun, then as the heat penetrates, the sheet begins to sag toward the form. When it lays correctly on it's own, cut off the element and let it sit for 15 minutes to cool. Don't force cool. Let time do the work. The process is similar for aircraft bubble canopies except they apply a few psi to shape them once the plastic sags then hold the minimum pressure as it cools. A flat glass or plastic insert is a lot easier and quicker to replace than molding.

The gauge of the doors has to be very thick. I think mine were 3/8". Acrylic (plexi) can be shaped at a lower temp than poycarb (lexan) and is much cheaper, more scratch resistant, and tolerates oil contamination without failure.


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PostPosted: February 1, 2020, 1:08 pm 
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I'm fairly certain that the G10 3 is not any longer than a VW and muffler can.
Height should also be OK, and the exhaust will go to the side, then back.
Required radiator is so small I hope to be able to rear-mount it.
I do expect to modify the rear deck for access.
Might convert to a tilt rear.

On subject, yes that is basically what I recalled for bending.
Too bad an IR light will not work.
If I'm understanding correctly the oven need only enclose the area being bent.
There had to be a reasonably cheap way to do this as Bradley sold a lot of them.
Might be simpler to make Fiberglass doors with a window, as I see no need of the "Moon-Roof" feature.

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PostPosted: February 1, 2020, 2:22 pm 
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IIRC, the guys at work used to bend 1/16" Lexan (polycarb) in a press brake. No heating involved. they kept the whit plastic on until the end. These were used for demo products where they replaced formed sheet metal enclosures with the clear Lexan. I think plexi is better for long term exposure to UV.

My feeling is that the top in the red "Sports Car Market" GT above looks better and slightly more modern than the original see thru doors. It could easily be made using common fiberglass methods, leaving only the side window of plexi with no bends. It could also be insulated.

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PostPosted: February 1, 2020, 3:11 pm 
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RichardSIA wrote:
I'm fairly certain that the G10 3 is not any longer than a VW and muffler can.
Height should also be OK, and the exhaust will go to the side, then back.
Required radiator is so small I hope to be able to rear-mount it.
I do expect to modify the rear deck for access.
Might convert to a tilt rear.

On subject, yes that is basically what I recalled for bending.
Too bad an IR light will not work.
If I'm understanding correctly the oven need only enclose the area being bent.
There had to be a reasonably cheap way to do this as Bradley sold a lot of them.
Might be simpler to make Fiberglass doors with a window, as I see no need of the "Moon-Roof" feature.


The g10 distributor needs about a foot of clearance forward of the bell, and the bell is very close to the firewall so either a box inside or crank trigger edis. The access to the engine is what I am referring to. I'm sure it will fit though you will loose a couple inches with an adapter.

The radiator needs airflow. It is much better to put it where the wind blows. The body is styled to mimic a front rad. However an expensive high output fan and a alternator that can keep up will probably work ok.

The bending is expensive due to the cost of large, thick sheets of acrylic. You make the oven from isolators, special wire, some tin, an electric stove control, wood and tin. Then you should keep all that around in case you ever need to do it again. Flat windows common thickness and size are much less work and $$. Yes, the oven only heats the area to be softened. I'm sure acrylic was cheaper when Bradley made them.

If you go with glass, a curve in the top can provide a little more head room. Consider dropping the floor and shimming the body an inch off the pan for more interior space.

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PostPosted: February 1, 2020, 4:37 pm 
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Dropped floors seem to be common with these.
"Gurney Bubble" is a maybe.
If plexi is too hard to make work well, maybe just a set of side-curtains?
Fabric/Perspex over a tube frame, simple, light, and cheap.
Only needed in winter.
I kind of like the soft rear window pictured on the Sports Car Market pic.
I suppose a Firebird rear glass would be too wide, prefer the fast-back look.

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PostPosted: February 7, 2020, 8:21 pm 
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A couple things to keep in mind when choosing the material. Plexiglass (acrylic) has much better optical properties, is easily polished, and is much easier to bend and shape nicely. But, it doesn't have the impact resistance that Lexan does. Also, Lexan (polycarbonate) absorbs moisture from the air, so if you don't kiln dry it before heating and bending, it is very likely you will end up with bubbles in the plastic.


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PostPosted: February 8, 2020, 12:51 am 
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Couple of points.

Side windows, so impact is less of an issue. :D

Today I learned that some versions of these engines used an angle drive at the distributor to keep the engine shorter. 8)

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PostPosted: February 8, 2020, 11:56 am 
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You need to dry the plastic before heating and bending. Plexi has something like %1 water in it, something to do with its manufacture process.

To bend it it should be baked at something near boiling for "awhile" to dry it out. Use a little piece to test this. When it is hot enough to bend easily, it is also near a point where it will start shrinking.

The bending temperature is not far from boiling water temp., maybe 250?

The need to dry it makes a simple oven probably what you need. It may be available without water in it for industrial manufacturing or something but not easily available to us...

The windshield for my formula car was about 8 inches tall and 5 feet long so I was not very successful in trying to build a tinfoil extension to my kitchen oven.

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PostPosted: March 24, 2021, 9:03 pm 
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Youtube vids reveal that the oven is made from a discarded Barbecue.
I have one of those.
Not worrying about G10 or doors at the moment as summer is near.
Heard back from CA DMV today, another $42.00 and I will receive a title. :D

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PostPosted: May 23, 2021, 10:18 pm 
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Diy powder coat oven setup would suffice. (Plus you can run the thing out in the driveway for the sake of ventilation) Plenty of walkthroughs out there.

No hands on experience with acrylic but I do remember the folks on Tanked from Discovery building a lot of forms and baking 2-4" thick acrylic for aquariums. Light duty version of their style mould setup would probably be plenty for what you'd be doing.

Curious if a holster/sheath style mould and foam press block setup for kydex would work without screwing with the optics. Kydex is really straightforward with some practice.

I'd go a bit larger than final trim. Trimming seems like less work than trying for a clear weld joint to add a bit.


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PostPosted: May 23, 2021, 10:41 pm 
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After getting in and out of the Bradley I find I really do not fit.
Seems the trick is to cut and drop the floors for headroom.
Would still be more awkward than my Lotus Europa.
Now thinking that when the title finally shows up I may just put a buggy body on the pan.
Yes, I know the pan has to be shortened but at least getting in and out is easier.
Plus Buggies are more valuable than Bradleys.

Oh, and the GEO engine may end up in a Sprite.

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PostPosted: June 5, 2021, 1:03 am 
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Both acrylic and polycarbonate are hygroscopic (they suck in water vapor). I do "high-temp" (350F very soft) vacuum forming so I need my plastic very dry. I use a homebuilt electric drying oven and I dry .080" PC for 24 hours at around 180-200F. The thicker the sheet the longer it needs to dry. The sheets need to be used within 12-24 hours of drying or they will absorb the water again.

I think you can do "low-temp" bending of PC without drying, maybe around 250-300F.

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