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Learning how to build Lotus Seven replicas...together!
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PostPosted: Thu May 13, 2010 3:15 pm 
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Posts: 82
arbalest wrote:
I would like to have 3D model of a Miata spindle, if anyone is so inclined.

Mike Lydon

Me too!
I got some ruff measurements done and the spindles made in solidworks. If someone that has the spindles will take more measurements for me I'll make it. and post them up.
luke


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PostPosted: Thu May 13, 2010 3:58 pm 
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dhempy wrote:
Yep. I'm a slacker. Sorry 'bout that. ;-)

Sometime soon I'm going to pull everything off the frame for paint. I'll jig it up and take extensive measurements and post them. The WILL NOT be a recommended solution, as I don't have the experience in life or with this car to make an intelligent recommendation to others. But if it gives folks something to compare their own designs to, so much the better.

-dave


Hows this going? :D I have a VERY similar setup to yours (442, miata uprights, kinetic control arms), and would love to know what your specs are. Thanks!


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 Post subject: Re:
PostPosted: Thu Aug 04, 2011 11:26 pm 
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Location: central Arkansas
chetcpo wrote:
The lower ball joint should always lead the upper. I'm no expert, but I can't think of any exceptions to that rule.


Puhn's "How to Make Your Car Handle" has a caster chart. Bearing in mind the book is 30 years old, he lists:

-2 Olds Toronado
-1.5 68-72 Pontiac intermediates
-1 75-79 Buick p/s, 75-80 Nova m/s, 71-72 Eldorado, 73-74 Camaro Z-28
-3/4 75-80 Monza, Skyhawk, Sunbird, 71-80 Vega
-1/2 74-77 Valiant, Dart, Barracuda, Challenger m/s, 75-80 Versailles, Comet, Maverick, Monarch
-1/3 70-73 Toyota pickup

Granted none of those cars are much in the handling department.

At the other extreme:

+7 70-71 MGB
+9 Fiat 850 Spyder

I've driven both of those and wasn't much impressed either.

Most of the cars on the chart range from 0 to +3.

My '71 Capri was theoretically +1.75; I got it close to 0 by moving the sway bar (which doubled as strut rods) back with some custom brackets. Self-centering pretty much went away, but steering effort was very light and my lap times improved slightly at the autocross. My wife liked the feel after she got used to it, but it drove some other drivers nuts, particularly the ones who were used to releasing the steering wheel and letting it unwind by itself.


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PostPosted: Thu Aug 04, 2011 11:34 pm 
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The voice of reason
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I wonder if the cars with little or no positive caster have trail instead? I prefer light steering to heavy, the steering is very heavy on my FF - perhaps I should take a shot at removing some castor...

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SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


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PostPosted: Mon Sep 19, 2011 12:35 am 
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Location: Melbourne, Australia.
With my four wheel drive hot rod project, I went around in ever decreasing circles with the front suspension design for ages. It becomes vastly more complicated with drive shafts, front diff, and steering, with very little room to fit it all.

Anyhow, I put the front to one side for a while, and started on the rear suspension.
After a good look around, a Porsche 928 rear suspension was perfect for this project and the 928 geometry used exactly as Porsche designed it.

But that led me to a curious discovery.
The Porsche 928 has exactly the same track, wheelbase and weight distribution (50/50) I am aiming for. So I started to take a very keen interest in what Porsche did at the front, and the whole concept of the 928 suspension as a whole.

I have all the original Porsche suspension design figures. Camber gain, roll centre heights, roll stiffness, spring rates and all the rest. It all slowly started to make a great deal of sense as I reverse engineered the whole design. Some things Porsche did seemed at first a bit odd (WTF?), but then I started to understand why they did it like that, and the true cleverness of the thing became more apparent.

Bear in mind the 928 is now a very old car, but in it's day it was an absolute sensation as a good handling good riding GT car, and it won many technical awards and huge praise from the motoring writers around the world. It still stacks up well in both ride and handling with current models, which says rather a lot for the original.

So now I am using the entire Porsche 928 suspension design as the template of my hot rod.
Even down to using a pair of the original 928 antiroll bars at each end, hehehe.

So what, I hear some of you guys thinking...............

But why not use something already very well developed that works, such as a Lotus Elise (for example) as a basis for a complete new Locost suspension design?
The standard Miata is good, because Mazda poured a fortune into it's testing and development.
Cars such as these are much raced, and much discussed on the internet, and all the suspension design figures, quirks, and tweaks are more or less available with a bit of patient research.

Copy all the suspension settings and geometry from your chosen sports/racing car, and I bet your Locost will ride, steer and handle pretty darn well right from the start.

It is all very well to have long philosophical discussions on internet forums about king pin inclination, Ackerman, toe in, caster, or front scrub.
But it is not just one feature or one angle that determines what it feels like on the road to steer.
It is the complex mix of design features that have to all work together in harmony.

If a huge design team with a massive budget come up with a vehicle that works well enough to win praise, and it's fair share of racing success, it is probably better than any of us here could achieve with a first effort done by himself at home in isolation.

So my hot tip would be, talk enough, and read enough books to understand what the whole thing is all about, then find a real proven successful winner to copy.
Something that is as close in concept, size, and usage to the type of vehicle you are building yourself.
Use that as a design example, and you cannot go too far wrong.


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PostPosted: Mon Sep 19, 2011 2:16 am 
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The voice of reason
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Quote:
If a huge design team with a massive budget come up with a vehicle that works well enough to win praise, and it's fair share of racing success, it is probably better than any of us here could achieve with a first effort done by himself at home in isolation.


So why doesn't Porsche do this? A 928 is setup differently then their other models...

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SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


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PostPosted: Mon Sep 19, 2011 2:46 am 
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Location: Melbourne, Australia.
horizenjob wrote:
So why doesn't Porsche do this? A 928 is setup differently then their other models...

The 928 is a fairly heavy front engined V8 with very even weight distribution and designed for a very soft ride. It is more a GT than a sports car.
A 911 has a very strong rear weight bias, is smaller and lighter and is a very different car in a great many respects.
A Porsche Cayenne four wheel drive has a high ground clearance and large suspension travel and is designed for a totally different purpose again.

So there is no "standard" Porsche suspension across all models. Each vehicle suspension is optimised for its particular role and purpose.

I just stumbled across the fact that the 928 is an extremely close fit to what I am trying to do here, and their suspension solution seems to work very well for that type and size of vehicle. Not everyone's cup of tea though.

But it has given me the idea that there are some other pretty well developed and successful vehicles out there that have a much closer resemblance to a Locost in size and function. Something that may have suspension geometry and suspension design worth more than a passing look.

I remember the very first time I leaned down on a Ferrari, I was extremely surprised how soft the suspension was.
I always believed very fast good handling cars needed to be sprung as hard as a rock.
Definitely not so....
That was quite a revelation.


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PostPosted: Thu Jul 12, 2012 6:34 am 
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About to start my clubman build using a Mazda MX5 as the donor,based on a Chris Gibbs plan. First issue I have to find a solution to is finding possible alternatives to the Ford transit tie rod as the top ball joint and an Austin Maxi ball joint for the lower. I know a Mazda B2200 ball joint for the bottom works, all options at the moment require reaming and some machining. Has anyone found an easier alternative?


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PostPosted: Mon Aug 06, 2012 1:54 am 
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Joined: Thu Mar 18, 2010 5:20 am
Posts: 86
Location: New Zealand
Hi
I found a tie rod end that works, it has an m16 thread and was the tie rod end from a small mazda truck. I could give you the part no but it may not be much use to you and besides I don't have it with me. I just rocked up to a suspension dealer and we went through the various boxes until we found something that fitted. The original can be used on the bottom.

Bruce


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