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Learning how to build Lotus Seven replicas...together!
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PostPosted: June 19, 2020, 5:58 am 
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Joined: June 19, 2020, 3:31 am
Posts: 5
Hi all, long time lurker first time poster.

I am working on a chassis design for a new build. It is a little unusual and a world away from a "7" but this website seems to be a pretty good resource for builders of all shapes and sizes.

First, I am from the UK and so everything is right hand drive. most dimensions are also metric but I will ry and convert where I remember.

The car uses components from a Citroen 2CV including the engine, gearbox, steering as well as some components from the suspension system although front and rear arms will be bespoke. For those that are unaware of how a 2CV suspension works I would have a quick google as it is quite interesting, but briefly the springs and shocks sit horizontally along the chassis, and the shocks work in extension rather than compression. This means the strength of the chassis is entirely in the horizontal plane. (image below)

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A 2CV is front engine, front wheel drive. however the front and rear suspension arms use the same pickups, so you can put the front arms on the rear and the rear on the front. or you can put a second pair of fronts on the rear and make either a 2 engined 4wd car (which Citroen did, the Sahara) or you can make a rear or mid-engined car. This was my thought process anyway.

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That was about 6 months ago. With this idea I started to work out the details for example where do I sit? where will the engine go exactly? To cut a long story short a lot of stuff happened including building a wooden package buck.

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changing the design from a 2 seater to a single seater. This was because of my desire to lower the H-point, to lower the roll hoop height or "roofline" and with this as a goal you need to avoid sitting ontop of the suspension springs which either means a really wide car or sit between them, meaning only 1 seat. I then mocked up what this would look like in CAD - because I could.

Image

I was quite happy with this design. It is a shame to not take others with me on a journey but it was minimal fabrication as I could modify the original chassis keeping the suspension mounts original and should result in a quick-ish build.

However

There was no space for a fuel tank. at all. without compromising the aesthetic which I had already compromised for by making it a single seater. I wasn't going to compromise again. So I took the buck measurements as the minimum package space for 1 CB11ACD (it was a tight fit) - drew it in CAD and the played around with the different components.

Which leads me to the current day, where I have thrown caution to the wind and I will manufacture my own chassis inspired by the locost/haynes chassis. It uses a mix of 25x25x1.5mm (1"x1"x16g) and 25x50x1.5mm (1"x2"x16g) profiles. The low H-point sitting on suspension issue is resolved by moving the rear spring outboard of the occupant with a new "axle" and the front spring which uses the original axle is kept where it is but the occupants feet sit above (so not a flat floor)

I will dump a load of CAD images here, and I have also uploaded the chassis and rear arms to Sketchfab so you can spin it around and have a proper look.

https://skfb.ly/6T9VI

A few notes on the current model – it isn’t finished.
    I am still working on the front leading arms and so have not finished off the bracing especially the ones going to the front hoop.
    The chassis will be panelled in aluminium bonded and riveted for strength over the 2 front hoops as well as down the sides on the interior and exterior.
    Things like seatbelt mounts, engine mounts etc are not there, neither is the suspension linkages.
    For the colour coding. BLUE = 25x50mm box, ORANGE = 25x25mm box, PINK = 25x25mm angle, PURPLE = 25mm strip. LIGHT BLUE = suspension springs.
    It will have a headrest and upper back support. The seat may be built into the chassis, that is undecided.
    The engine power will be low. intially with an uprated 2CV engine at around 50hp but eventually up to 120hp

Sorry for the long post. Here are some pictures.

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I also don't have a name for this yet (as I keep changing what it is...) any sugestions?

I can go into more detail in a future post, but I htink for now this is enough of an introduction.


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PostPosted: June 20, 2020, 8:02 am 
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Joined: July 17, 2008, 9:11 am
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Location: West Chicago,IL
This design is way outside of the box. I'll be interested in seeing how things progress. I'm not sure exactly how sporty the suspension in a Citroen is. But since you are building a new chassis, nothing I see prevents using 4 individual coilovers mounted horizontally if needed.

As for a name, how about CitLo 7CV? Named from Citroen Locost. Also a play in "Sit Low"

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766


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PostPosted: June 21, 2020, 2:03 pm 
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Joined: September 22, 2005, 10:29 am
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I like it. Outside the box in a good way.


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PostPosted: June 21, 2020, 4:34 pm 
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Joined: September 30, 2005, 1:28 am
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Location: Sunny-Okanagan, Canada, eh?!
"Citroenella?"

This looks interesting!

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PostPosted: June 21, 2020, 8:47 pm 
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Joined: April 23, 2019, 4:30 am
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Location: New Zealand
I like "deux poings" = two fists :boxing: Since it's a twin cylinder and this car will be a little fighter!


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PostPosted: June 22, 2020, 9:24 am 
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Joined: June 19, 2020, 3:31 am
Posts: 5
"outside the box" is what I tend to lean towards so I am not suprised by those comments.

Names are all good, hadn't thought of any of those before!

I have thrown some surfaces onto it this morning to show you what I am thinking bodywork wise. It is very rough but wil give you an idea of the design.

The middle portion the body will be structural as it will be a stressed skin construction over the steel frame.

Image

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The rear bodywork is a bit rubbish at the moment. I want the closed in wheels (inspired by the Citroen Dyane + 2CV) but the rest I am not sure. The engine and gearbox will be covered mostly but I want to be able to see the gearbox, inoard brakes and driveshafts from the rear similar to old race cars.

The front design is quite Germanic, almost Porsche like but I am a big air-cooled Porsche fan so no suprise there.


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PostPosted: June 22, 2020, 9:17 pm 
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And here I was thinking the front had a bit of TR-3 and Bugeye (or do you say Frogeye?) Sprite inspiration.

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766


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PostPosted: June 22, 2020, 11:19 pm 
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Joined: September 30, 2005, 1:28 am
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Location: Sunny-Okanagan, Canada, eh?!
CB11ACD wrote:
"outside the box"


"hors du cadre"

or

"être innovant"

I do not speak French.

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