Deformable Hinges in Suspensions

[LogicPro]

Hi all, I've just registered into this forum, even though I started reading your very interesting topics some time ago
I would like to know if somebody has some images, animations or simply explanations about the deformable hinges that are used in Formula 1 suspensions. Especially I would like to know which are the advantages and why they are preferred to ball joints...
Thanks in advance.

[spacer]

Try searching the forum for "flextures", I believe that's the term you're looking for .

[marcush.]

flexure to be precise .sorry for being nitpicky

for a start:
http://www.smpp.northwestern.edu/savedL ... 27p788.pdf

and closer to formula 1:

http://www.gef.es/Congresos/24/pdf/3-13.pdf
http://www.gef.es/congresos/21/PDF/7-14.pdf

[Greg Locock]

Marcush, great links. Basically the advantages are weight, especially once you consider designing abutments for threaded ball joints, and ease of integration into composite structures. There's a slight advantage in lack of stiction, and low friction and damping.

[Tommy Cookers]

part-spherical joints were introduced in race cars over 50 years ago to allow the greater and more adjustable suspension motion that had become fashionable/desirable (combined with good locational rigidity within this motion)
for 50 years before that suspension motion and location were less rigorous, and flexure functionality was used in millions of cars, for cost saving etc
it wasn't called flexure functionality, it was called a (clamped) leaf spring
eg Ford T and many others, or any quarter-elliptic does this

the Mk 1 AC Cobra and the WDC winning Maserati 250F also
(and hundreds of others with this 'single-wishbone' type of suspension that dominated the 1950s)
much or most of the wheel travel comes from the flexing at the 'root'/chassis end of the leaf spring
so the so-called spring was broadly acting as a (nominally rigid) wishbone type suspension arm with a flexure mounting

for 30 years now F1 has again had such small wheel travel that flexures were viable (even in metal, ie without needing CF)
(but flexures were banned for many years, to help F1 credibility by avoiding further departure from apparent road relevance ?)

30 years ago I designed metal flexure functionalities (in other fields)
engines (egTrojan car) have successfully used 1 piece piston/connecting rods to flex and so eliminate the gudgeon/wrist pin etc
an Asian cycle company tried to base rear suspension around flexures, but people were only happy with sliding, wearing joints

maybe designers need F1 to reinvent and legitimise flexural functionalities as new and high-tech ?

[flyboy2160]

flexure to be precise .sorry for being nitpicky

for a start:
http://www.smpp.northwestern.edu/savedL ... 27p788.pdf

and closer to formula 1:

http://www.gef.es/Congresos/24/pdf/3-13.pdf
http://www.gef.es/congresos/21/PDF/7-14.pdf

Marcush,

Thank you very much for the 2 interesting and informative papers. (The link to the first one doesn't work for me.)

The toughened resin paper is over 10 years old. The toughened epoxies and bismaleimides are now, and have been, virtually as good as the thermoplastics. At some point, F1 will get to the very expensive through-fiber reinforcements to improve the buckling, unless they are already banned for cost reasons.

As good as this forum is, I wish it had much more information like this and less technical posturing by people without real technical knowledge. (Ha, those with very high ratings will probably down vote me by -50000 for this.)

edit: bring on the ignore user function!

[LogicPro]

Thanks a lot Marcush for the documents you posted! (and also thanks to the other useful replies )

@flyboy2160: if you copy and paste the last part of the link (which doesn't copy automatically when clicking on it), the first document opens. Just copy ")TransASME127p788.pdf" at the end of the highlighted link.

[riff_raff]

Especially I would like to know which are the advantages and why they are preferred to ball joints..

There are a couple advantages to using flexures instead of spherical bearings on F1 A-arms.

First, flexures are lighter.

Second, flexures have fewer parts and are more reliable.

Third, flexures provide a more direct and efficient structural load transfer path.

Fourth, flexures have a smaller frontal area which reduces drag a bit.

Fifth, flexures don't have the sliding friction losses that spherical bearings do. The only significant variable that must be considered with flexures is their structural stiffness, which is very predictable and consistent. The friction losses of spherical bearings can vary greatly, due to factors such as wear or applied loads.

[Tommy Cookers]

regarding flexures made from metal, much the greatest design scope will be realisable using Copper-Beryllium alloy (2% Be)
this is F1 rule-compliant

being nearly as strong as super strength steels, but having a much lower elastic modulus
its elastic strain range is nearly 10000 ppm
(EDITED 16th about 25% better than any steel (except Maraging 350) and anything Titanium-based)
and it's a practical material (but heavy)
for decent fatigue life you might design for 5000 ppm of strain (that's a lot !)

[Jersey Tom]

regarding flexures made from metal, much the greatest design scope will be realisable using Copper-Beryllium alloy (2% Be)
this is F1 rule-compliant

being nearly as strong as super strength steels, but having a much lower elastic modulus
its elastic strain range is nearly 10000 ppm (about 50% better than any steel and much better than Titanium etc)
and it's a practical material
for decent fatigue life you might design for 5000 ppm of strain (that's a lot !)

Very interesting. Though I will say, I have a ChampCar control arm somewhere around here, with a steel flexure welded into it. It's amazing how flexible it is, even with the relatively high modulus. Particularly noticeable if you clamp the flexure bits in a vice and then move the wheel-side ball joint. Moves pretty easily though a reasonable travel range even with one finger! I'd go so far as to say the contribution to wheel rate is pretty negligible.

[Tommy Cookers]

I shall take your information as vindication !
IMO flexures should be no problem even with normal metals (in principle even in road cars)

the CuBe is the best in where a spring-type functionality is needed in a part than must be made by machining
unless the high density is a problem
(the main use is a lower grade used for relay/switch spring contacts etc)

[abw]

the CuBe is the best in where a spring-type functionality is needed in a part than must be made by machining unless the high density is a problem
(the main use is a lower grade used for relay/switch spring contacts etc)

Ah, CuBe. One of my favorite precipitation-hardened alloys. Interesting reasonably-high-tech application: Some of these louvered springs (http://www.multi-contact.com/) are made from CuBe. They are handy for ensuring electrical contact between vibrating parts that might be subject to a broad range of operating temperatures.

[riff_raff]

For flexures that are adhesively bonded into the A-arm, titanium alloys or maraging steel alloys might work best. Flexures would not be a good choice for road cars due to the limited amount of angular deflection they can tolerate without overstress, and that they would not have adequate fatigue life capability under the combined magnitude of reverse bending and high number of load cycles.

[Tommy Cookers]

having done a bit of checking (including your nominations), I'm sticking with my CuBe
in strain terms it's slightly ahead of even Maragimg 350/Vascomax 350 (well ahead of Maraging 300 and anything Titanium)
(350 has seemed rather unavailable or non-preferred ?)

agreed it's not as simple as just looking at useable strain

agreed all these materials would be useable if the application was right for flexures

[riff_raff]

One other thing we should consider if the flexure is bonded to composite is how well its tensile modulus matches that of the composite. If there is a large mismatch in modulus between the metal and composite at the bondline, then the difference in strain under load can cause a shear failure in the adhesive bond.