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Learning how to build Lotus Seven replicas...together!
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 Post subject: WBs Fauxtus 7
PostPosted: May 26, 2023, 4:22 pm 
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I've been gleaning here for a long time, so time to start a build log. (Semi-parallel thread at usa7s.net)
Some quick history. My dad raced a Turner 950S in the late 60s early 70s, from when I was around 2 to 12 years old. The Turner was awesome (sadly, it came to an untimely demise), but even as a kid, I couldn't help noticing these weird cars, always lurking in the background, that I couldn't quite figure out. To my young eyes they kind of looked like a formula car, kind of like a squished Model A, and they seemed to be everywhere! I knew I would have to have one someday...
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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 28, 2023, 3:46 am 
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Intending a somewhat traditional build. Similar to a Series 2/3 Seven from the mid to late 60s.

Engine: Cortina pre crossflow, tuned as budget allows. Mainly want to get it on the road!
Transmission: Cortina or Pinto 4 speed, standard ratios. Have both, not sure which I'll use yet.
Front Suspension: Spitfire uprights, Lotus lower wishbones, custom upper wishbones, 3/4" anti-roll bar.
Rear Suspension: Cortina axle, trailing arms, Panhard bar.
Wheels/Tires: Cortina GT, steel, 13 x 4.5, 175/70-13.

Frame is closer to a Lotus than a book frame. Design is a hybrid of the plans, mods, and specs floating around online. Stretched a little so I can fit "comfortably."

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F7_CHASSIS_Side.png


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F7_CHASSIS_Upper.png


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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 28, 2023, 9:39 am 
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Always look forward to watching another 7 build! My first Super 7 ride was powered by a Pinto drive train, I was hooked.
Good luck :cheers:

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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 28, 2023, 9:44 am 
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I see the ifs is canted for caster. Otherwise spitfire lcap and ucap geometry but no anti-ackermann rack position and eliminating the trunion?

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Lotus7:115x39x7.25
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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 28, 2023, 12:07 pm 
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If you already have those parts on-hand, it'll be fine. But, since it typically takes 5-10 years to complete a car, there's a small risk of ending up with something with no spares available. If possible, consider using newer parts, either fabricated or domestically sourced so that they're easy to find in any car parts store or wrecking yard.

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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 28, 2023, 12:49 pm 
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Miatav8,MstrASE,A&P,F wrote:
I see the ifs is canted for caster. Otherwise spitfire lcap and ucap geometry but no anti-ackermann rack position and eliminating the trunion?


(lcap/ucap = upper/lower control arm position?)

I haven't positioned the rack yet, I figured I'd deal with Ackerman and bump-steer by mock-up and measurement once the control arms are in place. What I don't know is what I'm aiming for in terms of Ackerman. Like most suspension questions, probably a matter of compromise? I'm sure it's been discussed at length here but I haven't delved into it yet. Any recommendations for a starting point?

By eliminating the trunion, do you mean converting the Triumph uprights to a lower ball or heim joint?

I used vsusp.com starting with the lower control arm and upright as constants. With the components I'm using, I'll have an adjustable upper control arm for camber but everything else will basically be as-built. Caster is 5°, camber -1°. With vsusp, I was able to get a pretty stable roll-center, but with Lotus type geometry, the caster is achieved by the difference between front and rear control arm mounting points (as you noted), and I don't really know what effect that has on everything else.

All that said, I know the original Lotus setup is not ideal, but it's kind of what I'm going for for now, optimized a bit. I figure I can upgrade to fully adjustable control arms in the future.

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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 28, 2023, 12:56 pm 
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KB58 wrote:
If you already have those parts on-hand, it'll be fine. But, since it typically takes 5-10 years to complete a car, there's a small risk of ending up with something with no spares available. If possible, consider using newer parts, either fabricated or domestically sourced so that they're easy to find in any car parts store or wrecking yard.

You're completely right on components. Well chosen newer components can be better, stronger, serviceable, replaceable, cheaper, etc., but where's the fun in that? Just kidding, you're right, that would be the logical route, but this isn't really a logical build. I'm wanting to build something vintage-ish, and sourcing parts has been half the fun.


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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 28, 2023, 3:36 pm 
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Yes, replacing the spitfire trunion with a spherical. The low weight of the spitfire ifs is impressive.This being a nostalgia build and I'd probably use the the same thing. If it were a clean sheet, miata is hard to beat.

I've seen a recommendation of 1.5-2.5 degrees toe out with 10 degrees at the outside wheel for dwarfs. We have some topics on ackermann and turning circle and it isn't fresh on my brain, but some, is better than none, is better than anti. Placing the rack aft of a centerline between the tierod eye on the spindles will be positive.

I expect the effective vsusp X and Y values for the split dim lcaps and ucaps would be to split the difference (i.e. lcapx1 plus lcapx2 over 2 equals effective lcap x). I don't see a downside (or anti-dive benefit) since the instant center of the IFS in the side view is still infinite, but I've not done the math. I would not waste too much time thinking about it versus building.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 28, 2023, 4:18 pm 
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I would not waste too much time thinking about it versus building.


Quote of the day. Good advice!


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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 29, 2023, 11:15 am 
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Great historical photos & explanation of your motivation. I'm looking forward to your build.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 29, 2023, 12:49 pm 
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In the time it will take to complete your car those "Newer" and "More available" parts will become NLA too.
On the other hand, classic LBC parts have a dedicated network of suppliers that will still be around after the here today-gone tomorrow crowd have abandoned us.

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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 29, 2023, 3:04 pm 
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After I'd already gone down the British parts route, my son totaled his NB Miata. Suspension bits and drivetrain were undamaged. It was definitely tempting to change course and use the Miata as a donor, but again, what's the fun in having good, serviceable, easy to find parts all in one place?? In the end, I stuck with the Brits. Long live the King!


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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 30, 2023, 2:34 pm 
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I don't seem to be able to attach anymore images. I get the upload progress window, but it never completes. Any tips? Is there a file or size limit? I'm just uploading typical photos, nothing big.

Thanks


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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 30, 2023, 3:57 pm 
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Yes, there is a file limit size. I've found images with a maximum of 750+/- pixels in either dimension works best.

My cell phone records images over 2000 pixels on a side and they don't load and are really to big for viewing on the website anyway. I mostly use an old Sony digital camera I've had for years for my build photos. It goes as small as 640x480 (old VGA), which are actually not bad if you're filming details. Otherwise load your photos into MS Paint (or equal) and resize them before posting.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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 Post subject: Re: WBs Fauxtus 7
PostPosted: May 30, 2023, 4:39 pm 
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I use postimage to host my photos & direct link them from there
https://postimages.org/

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