still confused about a arms..

[danilo]

Been reading my new Haynes book :-)
Been perusing the A Arm designs and have noticed, beyond the 'strange' offset of the lower shock mount (although explained somewhat by Talon.. thank you :-)
Or that the upper A Arm is suggested to have an 8 degree angle on the track rod tube.. erm Why? the angle would then be even less than optimum at actual use settings... besides it's a Ball joint :-)
I was marveling at the lay down angle of the shock /spring unit.. All literature claiming that such extreme angles deteriorate effectiveness.
Notably the lower arm is 17"~ !! ? long.
A Caterham SV (the large one :-) is 12"~ centre to centre. That particular 7 handles pretty well by most yardsticks.
My guess is that this 'extra' width was generated in attempt to accommodate the Sierra track dimension?
Silly observation: but it seems to my dim mind that widening the front chassis rather than the A Arms may have been the superior suspension design route? Certainly would have resulted in a more favourable angle for the coil units. Likely negated the need to hacksaw up the steering rack as well.
Yess the result would have been a wider nose section. Dunno if that's better or worse visually though.

[baz-r]

top arm angles to the draglink/balljoint as it stops it straining at its limit if the arm was stright it would break the joint

[twinturbo]

My guess is that this 'extra' width was generated in attempt to accommodate the Sierra track dimension?

Not sure how close it is to the sierra track at the front given it uses escort rack and extensions.

Likely negated the need to hacksaw up the steering rack as well.

No need to hack a rack, the escort one is used.



Sounds like you should set up and build a revised design

TT

[danilo]

The A Arms in Caterhams and even Locusts don't feature an angled upper balljoint fittment .

Without doubt a different chassis design is suggested :-)
I ...have... drawn an SV clone chassis as a .dwg, down to the last detail.
And the geometry works fine :-) ALL of it.
Using Caterham SV overall dims. And Cat A arms.. why not? they are of good proven quality/design, as well as easily available for similar to clone pricings.
No inordinately long A Arms, No lay down coil overs. No boiler plate shock mounts.. in the wrong place :-) No hacksawing a steering rack :-)
I've solved the design for my chassis build to my complete satisfaction :-) Anyone else can do it too, it's no longer rocket science, with the plethora of excellent programs available these days.

Was only wondering aloud about the design, being so out of step with proven practice, is all and why seeming adults presumably with a fair amount of life experiences, are so complacent/ accepting of it.
Is it just because it's printed on a piece of paper ?

[danilo]

The A Arms in Caterhams and even Locusts don't feature an angled upper balljoint fittment .

Without doubt a different chassis design is needed.:-)
I ...have... drawn an SV clone chassis as a .dwg, down to the last detail.
And the geometry works fine :-) ALL of it.
Using Caterham SV overall dims. AND Cat A arms.. why not? they are of good proven quality/design, as well as easily available for similar to clone pricings.
No inordinately long A Arms, No lay down coil overs. No hacksawing a steering rack :-)
I've solved the design for my chassis build to my complete satisfaction :-) Anyone else can do it too, it's no longer rocket science, with the plethora of excellent programs available these days.

Was only wondering aloud about the design, being so out of step with proven practice, is all and why seeming adults presumably with a fair amount of life experiences, are so complacent/ accepting of it.
Is it just because it's printed on a piece of paper ?

[minicountryman1961]

Originally Posted by danilo

Was only wondering aloud about the design, being so out of step with proven practice, is all and why seeming adults presumably with a fair amount of life experiences, are so complacent/ accepting of it.
Is it just because it's printed on a piece of paper ?

It is printed on paper, it is also true that many have been built and their owners are quite happy with them.. If you fancy yourself a chassis designer, build what you want. The thing is, building a proven moderately standardized design means we can buy parts from suppliers with a reasonable expectation that they will fit and work properly. It also means we can get good advice from others who have gone before us on this path. If you chose to go with your own design, you will make mistakes and it will be up to you to diagnose and solve them.

[spud69]

Chassis and mainly suspension design is a bit a black art and always a compromise between certain handling traits, it's a shame that Chris Gibbs is not available online to explain why certain decisions where made regarding the suspension design and setup. The main thing being that Martin Keenan formerly of MK Engineering had a large part to play in the design of the car and suspension, Martin has built a reputation in the Kit Car community for his design and car building skills - he is well respected in this area.

Certainly from my experience and other builders i have been involved with the handling of the roadster is not compromised in any way and handles, on road and track, in a balanced and very predictable way and definitely on a par with other brands of a similar nature.

The main thing is that the guide is intended exactly as that and if a builder is not comfortable with certain aspects then they can be changed to suit the builders preference, the philosophy of the self build concept which is why most of us are building to the guide so that we can have the satisfaction of a self built roadster at the end of the day not just a bolt together kit. I have seen most builders customise certain parts of their build for personal preference some more than others.

The above is not intended to defend the Haynes Roadster for the sake of Saturn but is plainly a personal opinion as to why the guide and roadster has been quite successful and we all love the self build approach to the car. A main reason why i put a lot of work into producing a guide to supplement the book for a change of donor car to the Mx-5, some people have amended this also to suit their own preferences, it certainly hasn't been done to generate lots of orders but to keep the self build culture alive.

Please don't take this the wrong way Dan, it's just my opinion that's all whether it be right or wrong.

Regards....AndyH

[MarkB]

The Sierra based Roadster handles like a shopping trolley and understeers for a past time but that is my opinion and no doubt will be frowned upon.....

[spud69]

Originally Posted by MarkB

The Sierra based Roadster handles like a shopping trolley and understeers for a past time but that is my opinion and no doubt will be frowned upon.....

I must be doing something wrong then cos mine and the ones i've put on the road dont and i'm sure the people i've taken out would agree......

[mark]

Originally Posted by MarkB

The Sierra based Roadster handles like a shopping trolley and understeers for a past time but that is my opinion and no doubt will be frowned upon.....

If only someone could design a fabricated upright and revised wishbones so my roadster could go around corners, ive been trying to get out of my street for the last 18months but this damn understeer wont let me!