The Lotus Cars Community banner

1 - 20 of 25 Posts

·
Registered
Joined
·
99 Posts
Discussion Starter #1
Hey

Ok, so to start of my story, I just purchased a unfinished project. The guy started building what could be considered a Ariel atom replica and never really finished it.

Basicly everything still needs work, but thats ok. My biggest problem is the suspension. I'm an engineer, but i'm no suspension designer. The car has suspension...but it looks like something that was made with the "this fits here...weld" mentality. I know the suspension will make or break this car. So I got thinking...what would compare, the lotus came to mind first, I had a Elise 2 years ago, so I figures I would come back. This would be the best place for help.

At this point i'm wondering if I should just try to get the dimensions off a Elise/exige and copy them exacly. I know the overall weight and everything will be off a little, but this would be a VERY good start. Unless someone here had a better idea? I'm basicly looking for suggestion. What would be my best options for a proper street/track suspension.

Any help would be greatly appreciated.
Thanks for your time guys.
 

·
Registered
Joined
·
935 Posts
re: Suspension

Copying one car's suspension to another may not do the trick. It is not the weight but the geometry that is the most important.

The location of suspension pick-up (mounting) points and the width of the car is key. Also the location of the steering and toe rods in the back.

You can get parts and weld your own suspension from most racing shops e.g. HRPWorld, Howe, SCP, etc. This is not hard at all, but the geometry has to be right. The development work that goes into that is worth a lot of $$. A little difference may result in a very badly handling car.

I would pick-up a suspension book, as well.

Anton
 

·
Registered
Joined
·
99 Posts
Discussion Starter #3
Thats exacly what i'm talking about...I would like to maybe copy the lotus suspension...as in EVERYTHING, controle arm mounting points and angles, spindle angles, shock mounting point and angle...everything would have to be a exact match for this to work.
 

·
Banned
Joined
·
3,239 Posts
Since the Arial Atom is such an excellent handling car, I would copy that suspension. If it was a very good replica, the actual Arial suspension could fit. I’d look into buying the actual Arial suspension components and installing them. Since you are asking your question in the way that you have, you will be miles ahead faster and cheaper is you just purchased those parts.
 

·
Registered
Joined
·
99 Posts
Discussion Starter #5
Thanks.

I did think about that to. I'm not convinced that the replica is all that good at this point. But I'll do the frame mods that are needed to make a suspension work.

The reason I was thinking of the lotus suspension was that it would probably be easier to get dimensions...since there are alot more lotus then ariel atoms.
 

·
Banned
Joined
·
3,239 Posts
Not that good of an idea…if the wheels and tires are not the same size…
Chassis stiffness is a big factor to…and I would guess that the Arial is so much torsionaly stiffer than the Lotus…
 

·
Registered
Joined
·
297 Posts
I know Sh!te about suspension!

But I'm not that dumb to know it's very complicated. Different arcs on top and bottom arms create camber changes as the suspension moves up and down. Also there is anti dive systems, castor adjustment, track changes, wieght distribution, Centre of gravity settings, etc. Then there is fitting the coilovers. Where do you attach them. How much dampening/spring rate, progression of units, etc.

I would go to an expert and get it designed right.
 

·
Registered
Joined
·
99 Posts
Discussion Starter #9
I realise there are a LOT of different think to do on a suspension...a lot of stuff to consider. That is why i`m thinking of simpy using the lotus suspension and geometry. ALL those items would be taken care of. It might not be perfect for this car, since it`s not exactly the same as a Elise/exige. but it would be as close as I can ever get it. Basicly just a lighter, stiffer lotus.
 

·
Registered
Joined
·
2,709 Posts
There's a thread here somewhere where a guy adapted Elise suspension to his 914. He could probably give you some good info.
 

·
Registered
Joined
·
1,182 Posts
I realise there are a LOT of different think to do on a suspension...a lot of stuff to consider. That is why i`m thinking of simpy using the lotus suspension and geometry. ALL those items would be taken care of. It might not be perfect for this car, since it`s not exactly the same as a Elise/exige. but it would be as close as I can ever get it. Basicly just a lighter, stiffer lotus.
It's not all just "taken care of" by using an Elise suspension as is.

The suspension depends A LOT on the chassis, not just on the component relationship to each other.

The Elise/Exige suspension was designed around it's chassis including weight, weight distribution, track width, wheelbase, etc.

Why not buy a book on chassis dynamics and suspension and do some digging before just assuming an Elise suspension is the best way to go?
 

·
Banned
Joined
·
3,239 Posts
There's a thread here somewhere where a guy adapted Elise suspension to his 914. He could probably give you some good info.
He took the Elise suspension whole... he cutup a crashed Elise chassis and made a jig to pick up the original suspension points. Then transfered the jig over to the 914 and built structure to pick up those points. The wheel base and track were close enough so that worked. My guess is that the Ariel is not as wide...
 

·
Registered
Joined
·
99 Posts
Discussion Starter #13
Well see thats the thing, The frame and suspension on this homemade setup right now are no where near my standards. So a good portion of the frame will be cut out, and the suspension will be re done from scratch. So I can set the wheelbase, track and mounting point to basicly exactly where they have to be.

As far as how do I know the lotus suspension design is right for this car, thats simple...I don`t. But since i`m no suspension designer, and i`m not planning on making 10 prototypes to get it right. Even with buying a book and reading up about it, i`m sure I could learn alot, and probably make something work. But with having no experience, do you really think I can come up with something better then what Lotus did with years of experience? I agree that is might not be perfect, but unless someone can design me something better for next to nothing price it might be the best I can do.

I agree that the frame stiffness is not the same, and the it will be lighter with the distribution being a little different. But really, if you take the lotus, stiffen it up and take out 500lbs would it make it handle like crap? Probably not. Am I missing something?
 

·
Registered
Joined
·
1,182 Posts
I'm just pointing out that you are willing to spend potentially thousands of dollars on suspension pieces, not to mention willing to hack a frame to allow for whatever wheelbase/track that you want... but you won't go buy a good book (maybe what $100?) and do some reading.

The book will likely be a far better "suspension guru" than any of us will be.

I'm not saying the Elise suspension won't work... Of course it will function in *some* manner. Personally I would just do more research and way my options between any number of OE suspension setups (not just Elise - How do you know the Atom, Miata, etc isn't more well suited) as well as a custom setup.
 

·
Registered
Joined
·
99 Posts
Discussion Starter #15
I agree with you. My concern is that no book will tell you exactly what to do. it all depends on what you want. The book will probably give a range of angles for stuff like anti dive, if you want more go one way, if you want less go the other way. (same with all the option, caster, camber, toe, skawt...I don`t know what I need. I have no idea how much I want of each and a trial and error method is not good on the pocket book. All the car companies come out with suspension updates every couple years, that are way better then the old setup, why didn`t they see that at first? I`ll have the same problem. There is no magic angle that will garanty I get what I want. But if I can at least get close. If the car ends up with to much over steer or under steer what will have to be fixed, but if I designed it, it probably would have the same problem.

As to why the lotus...well this is a very small, very light car with rear engine. There aren`t to many examples of such cars. As far as why the lotus vs the ariel atom. Well first off I need someone to get me accurate mounting point dimensions. I figured that would be easier with the lotus then a atom. Buying control arms will also be easier for the lotus. Finaly I figured lotus probably put alot more testing and tweeking in the suspension setup then atom did, just looking at there possible design budgets.

But I might be seeing this wrong.
 

·
Registered
Joined
·
3,311 Posts
bad bad bad idea

I guarantee you that if you just drop the Elise/Exige suspension in that frame without understanding how things work, it will handle and ride like crap. It will not be "Close enough". I went though an ordeal just figuring out spring rates on a coilover conversion in my Mustang. And it was not even to the degree of completely swapping suspension parts. Never mind kinematics and geometry, if the wheel base, width, and weight and distribution is different, it'll have a different natural frequency that require drastically different spring and shock rates.
 

·
Registered
Joined
·
99 Posts
Discussion Starter #17
Thanks for your imput. I completly agree with you. That this could be way off. I`m just worried that creating my own won`t be any better. And it might be best to try to tune it a little. It might be a complete head ache, but could it be worst then a full on custom?

for the shock setting...i`m new to this. I`m use to racing quad suspension. You send it off to a shop, they valve it and spring it properly on a shock dyno then you just bolt up and ride...with some minor changes to compression and rebound. Can this not be done for cars? Get Lotus geometry, bang on with the tires in the exact same locations. Then get a set of aftermarket coil overs sent off somewheres to get revalved for the exact same geometry, but for a light overall weight. (would check actual distrubution front to back)?

I`m really not trying to be complicated here. Just trying to get the facts figured out, and the why (good or bad, not just I thinks)

Do you seriously think that me buying a book can come up with something better then an exact lotus copy with proper shock tunning?...basicly that is the big question i`m trying to ask??

thanks everyone for your help...keep the comments going.
 

·
Inactive
Joined
·
831 Posts
The ariel atoms I've driven have had horrible suspension.

Try designing suspension that gives no track change on bump, a constant roll center (both in height and side to side), no roll camber change, no bump steer, all at different steering angles. It's pretty difficult. Then add in bushing compliance and toe changes. If you duplicate the Lotus suspension 100% it will be better than 99% of the kit cars out there.
 

·
Registered
Joined
·
99 Posts
Discussion Starter #20
The ariel atoms I've driven have had horrible suspension.

Try designing suspension that gives no track change on bump, a constant roll center (both in height and side to side), no roll camber change, no bump steer, all at different steering angles. It's pretty difficult. Then add in bushing compliance and toe changes. If you duplicate the Lotus suspension 100% it will be better than 99% of the kit cars out there.
This is pretty much what i`m thinking.


I agree with the rest of you that getting a proper suspension designed for this car, and then testing it and changing it 4-5 times like manufactures do to get it perfect would be the proper thing to do. But there are so many options and possibility. And even reading all the books in the world, there is no perfect angle / dimension / mounting point. It all depends what you want...honestly, I don`t know what I want or what I need. And I don`t have 20 000$ to get a kit design, that may or may not be any better then just swapping in the lotus parts.

My question to you guys now, and I want you to think about this in a serious manner. If you take a exige. And do the typical track mods. Drop it a little, take out say 300 lbs. Add wider tires, wider wheels, more power and stiffen up the chassis / suspension with aftermarket shocks, and stut bars. Will it make the car handle like complete crap? NO it probably doesn`t. It should make it into a wikid track car. But really it should make it almost undrivable. According to what you guys are saying. The lotus suspension was designed to work with the car stock. Now you are dropping the center of gravity, and making it lighter. So you are changing the roll centers, and loads on the wheels. Making it have a wider contact patch with a suspension that is not designed for it. So why doesn`t a track car handle like complete crap when it`s modified? The suspension is tuned, but the mounting points are not changed, the new rolls centers are not changed, the weight transfer is different center of gravity is way off. They should just leave the cars stock they would track better....Think about it guys. I might be completely out to lunch on that. But I don`t think so.
 
1 - 20 of 25 Posts
Top