Composite wishbones

[xpensive]

Based on all the properties I listed above, I would go for Al 7075 hands down and throw the parts away after every race.

- F1 suspension-parts are not subjected to bending, why stiffness (modulus) matters very little.
- Aircraft-aluminium such as 7075-T6 has a yield/tensile strength almost equal to Ti Gr.4.
- Density is only 60% of Ti's, elongation sucks but I trust my Boeing 777 taking me to Montreal this summer.
- Price is a fraction of Ti's. You pay for Ti's corrossion- and heat-resistance, things you have no need for here.

[DaveW]

Titanium will have lower mass than steel at equal design strenght. This is why it is the preferred metal for helicopters and aircraft over steel. In this application it reduces the unsprung mass which pushes performance.

u/s mass certainly will be reduced after the links have buckled & then failed. [Apologies, WB, couldn't resist sharing the image that flashed through my mind when re-reading your post...]

More seriously, F1 suspension links (specifically) appear to be complex components incorporating both metallic & carbon elements that have an aerodynamic function, contain wheel tethers and carry more than the obvious loads - I have seen a vehicle remain supported by its wheels with springs removed, for example.

I'm sure Ti is used in helicopters when that is an efficient solution. However, maraging steel is used where brute strength is required, and Al alloy is also used, particularly when robustness is a consideration (fuselage skins, for example).

[marcush.]

the ti fabrication is very hard on the tools you have to use .with modern high speed
milling and CAD -CAM you will not have to to much in terms of saw ,file or hole drilling anymore .cold working of Ti is also feasible in fact it work hardens in those areas of maximum bend so maybe if you are not taking this into account the end product may prove dangerous .
To me the flawed fabricated parts like Brakepedals are rather obviously a product of doing things in your workshop a bit too seat of the pants style and the Ti parts will weld not look too bad but they will not be of good quality but without a proper inspection this will not be obvious until the part fails..
so welding chamber with argon filling is what is needed ...then Ti welding is no more difficult or dangerous then welding mild steel

[DaveW]

..so welding chamber with argon filling is what is needed ...then Ti welding is no more difficult or dangerous then welding mild steel

My recollection is somewhat hazy at this distance (& I am not a metallurgist), but I recall that the Lotus brake pedal was fabricated by welding together several parts formed from 26 swg Ti sheet. When Elio hit the brake pedal, the assembly "unzipped", not along the welds, but along lines parallel to the welds. It was concluded that the temperature gradient occurring during the welding process had caused high stresses to be locked into the material, & that post-fabrication heat treatment would have dissipated those stresses. Chapman was unwilling to risk a repeat incident, so the theory was never tested.

[marcush.]

welding ti without the use of an inertgas argon chamber can be tricky especially if you forget to purge the backside of the weld (fabricated hollow(?) brakepedal.also purging is necessary until the ti has cooled down well down .Also maybe back then Argon in 99.999% purity was not avaialble .a very big point to notice is that you have while working the ti to keep temps as low a spossible to avoid scaling and only use carbide grinding as sanding papers contain aluminiumoxide that may get embedded into the ti.

[conni]

Based on all the properties I listed above, I would go for Al 7075 hands down and throw the parts away after every race.

- F1 suspension-parts are not subjected to bending, why stiffness (modulus) matters very little.
- Aircraft-aluminium such as 7075-T6 has a yield/tensile strength almost equal to Ti Gr.4.
- Density is only 60% of Ti's, elongation sucks but I trust my Boeing 777 taking me to Montreal this summer.
- Price is a fraction of Ti's. You pay for Ti's corrossion- and heat-resistance, things you have no need for here.

To say that the wishbones arnt subjected to bending is as far from the truth as you could get! the rear wisbones are fitted directly to the gearbox with no hinge and the wishbone itself does all the flexing with a spring and damper to control it

conni

[Jersey Tom]

7068 makes 7075 look like a joke

[Scotracer]

7068 makes 7075 look like a joke

Indeed it does

[xpensive]

7068 makes 7075 look like a joke

Please share, don't be shy?

[Scotracer]

7068 makes 7075 look like a joke

Please share, don't be shy?

Just look up the data for the two alloys - the only thing 7075 is better at, as far as I can see at a fairly quick glance is a higher melting range (which might be useful in a wishbone given high-performance brakes in the vicinity). The yield stress is massively greater in the 7068.

[xpensive]

So, why don't you enlighten us with some engineering-worthy data then?

[DaveW]

So, why don't you enlighten us with some engineering-worthy data then?

This might work for you.

[riff_raff]

xpensive,

"Based on all the properties I listed above, I would go for Al 7075 hands down..."

While aluminum alloys have a specific stiffness value (MoE/density) that compares favorably with alloy steels or titanium, it unfortunately does not like to endure the fully reversing (tension/compression) fatigue load conditions that a wishbone experiences. Once you apply a sensible knockdown factor for stress ratio when analyzing for fatigue in your aluminum wishbone, you'll find that aluminum is not a good choice. Plus, 7075 aluminum is not weldable.

Titanium is also not a good choice for a wishbone, since it is very notch sensitive. Which would likely result in a structural failure if the wishbone was scratched or dinged due to an impact. Titanium is also very difficult to fabricate.

Suspension members want to be as stiff and light as possible, in order to optimize suspension performance and provide consistency in chassis set-ups. Carbon/epoxy gives the best structural performance in this regard. The only drawback is that CRE composites are very expensive, and they don't have any appreciable elongation at failure, which means they tend to shatter during a crash as opposed to crumpling, like a steel wishbone would.

Regards,
Terry

[xpensive]

So, why don't you enlighten us with some engineering-worthy data then?

This might work for you.

I'm just kidding, I know 7068 is about 30% stronger than 7075 in both yield and tensile, why it has replaced a lot of Carbon-fibre on the Saab "Griffin" fighter they are about to give away to Brazil. But I hear it's a bitch to machine.

There's a world of xperience of working on 7075 ever since the Japanese invented it for the "Zero" fighter during WWII, basically every aircraft has been built from it since, why I'm certain it will hold up for an F1 race or two?

I don't think the carbon-fibre wishbone had ever been considered in a design-office populated by at least
some individuals other than aerospece-engineers, with no concept of "value over cost" or budget-limits.

[marcush.]

xpensive,

"Based on all the properties I listed above, I would go for Al 7075 hands down..."

While aluminum alloys have a specific stiffness value (MoE/density) that compares favorably with alloy steels or titanium, it unfortunately does not like to endure the fully reversing (tension/compression) fatigue load conditions that a wishbone experiences. Once you apply a sensible knockdown factor for stress ratio when analyzing for fatigue in your aluminum wishbone, you'll find that aluminum is not a good choice. Plus, 7075 aluminum is not weldable.

Titanium is also not a good choice for a wishbone, since it is very notch sensitive. Which would likely result in a structural failure if the wishbone was scratched or dinged due to an impact. Titanium is also very difficult to fabricate.

Suspension members want to be as stiff and light as possible, in order to optimize suspension performance and provide consistency in chassis set-ups. Carbon/epoxy gives the best structural performance in this regard. The only drawback is that CRE composites are very expensive, and they don't have any appreciable elongation at failure, which means they tend to shatter during a crash as opposed to crumpling, like a steel wishbone would.

Regards,
Terry

BUT: the same is even more true for carbon fibre,isn´t it?And this does not stop F1 making CF wishbones..