Home built Arete Supercar

Post here information about your own engineering projects, including but not limited to building your own car or designing a virtual car through CAD.
Zynerji
Zynerji
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Joined: Wed Jan 27, 2016 3:14 pm

Home built Arete Supercar

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Sorry if already posted. Great video!

Very interested in a discussion about attaching a chrome moly front/rear sub frame to a fiberglass chassis. It makes me cringe a tiny bit when I think about its strength. Wouldnt a tubular space frame be needed for the front to rear torsional stiffness requirements?

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variante
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Joined: Mon Apr 09, 2012 10:36 am
Location: Monza

Re: Home built Arete Supercar

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Super awesome project!
Bus yes, it doesn't seem like the builder intends to respect any strict parameter. In one video he even says that he made the lower sides of the chassis thin so that his wife can get in without troubles even with a cocktail dress... And, boy, they are thin!
The SLS style roof line is worrying as well.
Can't comment on the tubular chassis, as it looks like he isn't done with it yet.

Zynerji
Zynerji
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Joined: Wed Jan 27, 2016 3:14 pm

Re: Home built Arete Supercar

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variante wrote:
Mon Nov 09, 2020 6:22 am
Super awesome project!
Bus yes, it doesn't seem like the builder intends to respect any strict parameter. In one video he even says that he made the lower sides of the chassis thin so that his wife can get in without troubles even with a cocktail dress... And, boy, they are thin!
The SLS style roof line is worrying as well.
Can't comment on the tubular chassis, as it looks like he isn't done with it yet.
I mean, he laid up the monocoque in the mold shell, but didn't have any bracing on the shell to ensure it was perfectly square...

Hes obviously done a ton of work on this project, im just worried that the execution is not going to deliver what his design time should.

Rodak
Rodak
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Joined: Wed Oct 04, 2017 2:02 am

Re: Home built Arete Supercar

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Pretty amazing work, but as an ex aircraft composites guy I'm cringing at his use of glass and wet layup method. A couple of observations:

There is no control of the resin/cloth ratio; excess resin, which he certainly has, greatly reduces strength. The resin needs to be weighted vs cloth and he definitely should be using a vacuum bag and bleed cloth to compact the layup and suck out excess resin. For strength it would be better to use S-glass or carbon fiber and nomex with an epoxy resin; it looks like he's using polyester boat resin, which has no strength. If he plans to bolt the engine sub-frame to the rear bulkhead I see enormous problems. A far superior method would be vacuum bag pre-preg or wet layup and an oven; for a car you could probably get away with not using an autoclave. I also notice that he has not reinforced his molds and there is a lot of flexing going on. It appears he is laying all the cloth parallel; 0°, -45°, 90°, +45° type of orientation will reduce warpage potential, and some sort of directional cloth can be used for load paths. His use of honeycomb is good, but depth with a tapered edge equals strength

There's much more, with lots of tricks like pulling plastic faced plaster male/female molds and removing only high spots, which saves an enormous amount of sanding time, etc. Unfortunately I have huge doubts this will be strong enough, especially with the center section design.

Cool project, I hope it works

Zynerji
Zynerji
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Re: Home built Arete Supercar

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Rodak
Rodak
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Re: Home built Arete Supercar

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This is all good and well, but I do NOT see how the A pillar and roof structure connecting to the rear bulkhead is going to provide any strength to the central chassis, either in deflection or twist, especially if it is made of glass and polyester resin. This looks very nice but damn, there is no strength there. The lower chassis section looks to be too shallow to provide needed bending and torque resistance. There need to be hard points molded into the composite structure to take loads from the rear sub-frame and using foam for the bulkheads is easy but .... There seems to be no thought to load paths and the use of unidirectional fabric to transfer loads to the structure, such as it is. I would not drive this thing above 50 mph, let alone 200 mph or whatever. Which brings up the thought of crash structures......

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Stu
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Joined: Sat Nov 02, 2019 9:05 am
Location: Norfolk, UK

Re: Home built Arete Supercar

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I am finding this a very interesting project to follow; I do have reservations about how usable the finished car will be, but he does keep pushing that it is a prototype (which in my head translates as ‘conceptual exercise’). In the early episodes he does talk about how it would benefit from composite construction.
I cannot see how it will be usable as a performance vehicle without some interior tubular structure joining the two subframes through the floor, sill and roof. Old-tech, but aluminium-skinned honeycomb panels for bulkheads, floor and sills would do that job; leaving only tubular bracing through the roof-line.
Maybe that will be in V2.0....
He has mentioned building more than one.
Common sense is not as common as stupidity, but it is better to be uninformed than to be mis-informed...

Greg Locock
Greg Locock
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Joined: Fri Jun 29, 2012 11:48 pm

Re: Home built Arete Supercar

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The original Lotus Elite (1959) had a stressed GF body. However that resulted in various problems even Chapman couldn't ignore and that's when he switched to the metal backbone chassis and unstressed body for production cars. For the X180 I sneakily introduced a pair of braces at the front of the chassis that increased the understeer a lot (a happy accident, not actually my direct intent) so to some extent the body is now load bearing.
Last edited by Greg Locock on Fri Nov 13, 2020 6:47 am, edited 1 time in total.

Just_a_fan
Just_a_fan
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Re: Home built Arete Supercar

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Greg Locock wrote:
Tue Nov 10, 2020 11:10 pm
For the X180
The Esprit refresh? Cool. 8)
Turbo says "Dumpster sounds so much more classy. It's the diamond of the cesspools." oh, and "The Dutch fans are drunk. Maybe"

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coaster
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Joined: Sat Jun 30, 2012 4:10 am

Re: Home built Arete Supercar

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Looks like a widow maker, he should strip an old lotus elise and analyze the methods used as a benchmark.

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Tim.Wright
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Re: Home built Arete Supercar

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Far out, what a mess
Not the engineer at Force India

AngusF1
AngusF1
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Re: Home built Arete Supercar

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A torsional stiffness test would be... interesting.

AngusF1
AngusF1
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Re: Home built Arete Supercar

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This looks like a case of building something without understanding the design requirements first. It doesn’t seem like he’s established targets for stiffness and strength, nor done any work to determine that his design will be strong enough.

Maybe it’s just a rolling styling demonstrator / chassis mock-up?

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hUirEYExbN
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Joined: Tue Aug 25, 2020 1:30 pm

Re: Home built Arete Supercar

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There was a series on ... Motors TV (or something like that) back in the UK a couple of decades ago. A guy with limited knowledge attempted to built a sportscar, it never really worked out. I'm getting similar vibes from this.

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coaster
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Joined: Sat Jun 30, 2012 4:10 am

Re: Home built Arete Supercar

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Edit, saw the update on youtube, he's building it right, lost me a little with plaster and drop saw trick but i get the feeling this is not a cad build, going totally by intuition and hand skills.
Hats off to him.