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Learning how to build Lotus Seven replicas...together!
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PostPosted: April 17, 2017, 3:23 am 
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This is an old design from back before they became so famou$ and started getting $30K for a Chevy pro-street chassis. :shock: :roll:
Too large to scan here, I will see what I can do.
If you have Costin and Phipps Racing and Sports Car Design look at page 11.
It is somewhat similar to the Cooper Monaco chassis but with a bit more reinforcement.

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PostPosted: April 20, 2017, 3:15 am 
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Okay, I had the AM drawing blown up, then traced over it for legibility as it was badly faded.
Also made it "Color" instead of just black & white.
Then took a pic of the main drawing.
Body profile in red, suspension links in blue.
Currently a multi-tube frame but I'm thinking of trying to make it more of a space-frame.
In any case I doubt a few more diagonals would really hurt.
Is it just me, or is it a bit odd that so many tubes do not join at common points?
Suggestions for improvement welcomed!

Image

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PostPosted: April 20, 2017, 9:41 am 
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There's a lot you can do.

It doesn't look like you need the 180 degree bends to be made in one piece or even be part of the main chassis. That could save you money on bender and dies. The 180 bend could be replaced by a semi circle of plywood-fiberglass bonded to the bodywork, or other ideas.

I think you want a more continuous upper rail. I'm traveling today so I'll check in tonight and see if people have more ideas...

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PostPosted: April 20, 2017, 10:13 am 
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An amazing lack of triangulation - it's almost like the design effort stopped short of completion. Basically, each bay needs a diagonal, which doesn't have to be large tubing, just something to keep the whole effort from "lossanging", as the Brits are fond to say.

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PostPosted: April 20, 2017, 12:40 pm 
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I will be doing some mods for my own build due to using an Alfa four and factory suspension in place of the V8/M-II this chassis was designed for.
The V8 cars using this chassis do very well, perhaps the large diameter tube makes up for the lack of triangulation.
In many of the Locost chassis renderings I've viewed here the designs seem a bit overly complex but I do realize they are using small thin tube.
I will be adding some diagonals but hopefully not enough to increase the weight too much.
Still thinking some tweaks to bring more of the tubes together at common points would help.
If that is impractical, gussets?

My lower frame kick-up at the front will be much less.
I will be using the four-link at the rear, and R&P steering.
Alfa Spider front suspension reversed side to side.
Engine off-set 1" to the passenger side so that the oil pan clears the frame.
Main body mounts via Dzus fasteners with tilt front and rear.

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PostPosted: April 20, 2017, 2:33 pm 
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Yes this design is early on. In the move from ladder frame (two major "beams" with bracing) to Multi tube (usually 4 main tubes) then to true space frame (small size tubes with triangulation of bays). The cobras ( coupe "Daytona" & roadster) and the Cooper Monaco were early examples of success with the multi tube design. There are many improvements that can be made in these "archaic" designs. But still remaining in general "period" design. Depends on what you're trying to do with it. Create a true reproduction? Or an upgrade but staying with the looks of the period. Mainly relying on the body for the looks. Much of the bend designs proved weak. Because as was said at the time "pre-bent" is just that PRE_BENT" Meaning tubes that have been bent, tend to be weak at that point & when stressed continue to bend at those points. Looking at your plans it shows the front susp. Take a look at the Triumph Spitfire/GT6 front. The whole susp. comes off the frame & can be incorporated in it's entirety in a tube frame. Each side comes off as a unit including the shock tower & upper & lower A arms. If you can keep the track width the same. You can use the rack & pinion as is too. A very slick & easy transplant of the complete front suspension & brakes etc.
Some good books to read on the subject of design:

Racing Car Design & Development
By Len Terry (a designer during this time)

The Sports Car it's design & development
By Colin Cambell

Chassis Engineering
By Herb Adams

Race Car Chassis design & construction
By Forbs Aird

Also Lotus Sports Racers
A Brooklands Portfolio
Is very good for looking at & understanding the development of the space frame in Sports Racers. Lotus was a leader at the time in both Sports Racers & Formula one. There are a lot of period articles & photographs of chassis developments.


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PostPosted: April 20, 2017, 5:15 pm 
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Two main goals here.

1. A modified and improved light chassis for my own build.
Already bought the 1-5/8 DOM main lower tubes but no reason the rest of it cannot become much more of a space-frame.

2. Updated version of this chassis to be used by other Dio Tipo builders, most of whom will probably use V8's.
I think at least some added triangulation will be a must in any case.

Not really trying to keep the chassis an "In Period" design.
The original Special's were built on ladder frame TR3's.
The additional upper chassis members probably made them much stiffer than original but nowhere near what is done today.
What IS to be retained is the classic sports-racer look, much like the many Cobra replicas.

Once I have this sorted out I know where to get several other vintage style bodies. :wink:

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PostPosted: April 24, 2017, 11:10 pm 
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Got measurements I needed for the Alfa front suspension mounting points.
Unfortunately they require that I make the frame significantly narrower at the lower A arm mounts.
Which probably forces me to use the alternate Alfetta oil pan and pump instead of the current Spider pan.
Or, I can use the AM design front $u$pen$ion and $peedway hub$.
Alfa would be much more Locost.
Probably time to do some cutting and welding to mock-up the Alfa suspension to get a real look.

Still a fairly simple bend in the frame rails, but now I would have to calculate and make the bend in two planes.

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