Do we need suspension?

[DaveW]

We can change tire size and compounds, camber, toe, weight distribution, and any number of aero tools.

True enough, though "aero tools" might not be a good solution (balance will vary with airspeed), compound & size changes might not be permitted, & toe & camber changes affect performance in other ways.

p.s. I know nothing about karts, but I thought balance adjustments were made in that case by rims & front/rear track changes. Ciro?

Does load transfer in response to lateral force (g) in a instantaneous fashion.

Forgive me, but my copy is some distance away right now (85 miles as it happens). However, the vertical loads acting on individual tyres at an axle can always be decomposed into symmetrical & anti-symmetrical components. I presume that "load transfer" is the anti-symmetrical component of vertical load. That will (in steady conditions) balance the roll moment caused by lateral acceleration, but will also play a part in reacting any roll oscillations. The latter will be present when a turn is initiated & will normally decay quickly, but not always.

If you watch tin-top vehicles racing you might observe that some occasionally oscillate with a relatively stable amplitude as they go through a corner. The oscillation is usually a combination of pitch & roll & is sustained (when it happens) by the tyres' reaction to an oscillating vertical force at the limit of adhesion. Lateral acceleration will vary during such an event, but will not reflect entirely the variations in roll moment (that is part of the reason the oscillations are sustained).

[hardingfv32]

The most common form of balance adjustment in karts is a modification of the load level of the inside rear wheel. You have adjustable chassis flex as one tool. Caster is another. Caster in the turn will cause a diagonal form of load redistribution. The caster angle is fixed so you modify this effect by changing the track dimension. Wider tracks both front and rear increase the effect. As there is a max track dimension which the rear axle is usually up against, most adjustments are made in the front. The normal benefits of a wide track still apply so their are some compromises going on.

The driver has some input to this situation with his efforts to cause load transfer with his upper body and arms applying force through the steering column. Also ballast location which is located at varying heights on the seat.

Brian

[Jersey Tom]

Suspension? Nah, just run everything rigid. No worries.

[Belatti]

Let me add some comments (in bold) inside your writing.

The most common form of balance adjustment in karts is a modification of the load level of the inside rear wheel. You have adjustable chassis flex as one tool (THIS IS SUSPENSION ADJUSTMENT). Caster is another. Caster in the turn will cause a diagonal form of load redistribution. The caster angle is fixed so you modify this effect by changing the track dimension. Wider tracks both front and rear increase the effect (THIS IS SUSPENSION ADJUSTMENT). As there is a max track dimension which the rear axle is usually up against, most adjustments are made in the front. The normal benefits of a wide track still apply so their are some compromises going on.

The driver has some input to this situation with his efforts to cause load transfer with his upper body and arms applying force through the steering column. Also ballast location which is located at varying heights on the seat.

Brian

[Nowhereman]

Finally, I've found an F1 site that has intelligent members talking engineering.
It is refreshing.
I'm going to throw out a question to you all about braking and weight transfer.
Could a person design in hydraulic lock up in dampers so that when an electric signal is sent via the brake pedal, it would prevent anymore compressive loading.
This would in fact hold the car at a set ride height during braking allowing a much better / stable car during braking.
Under a no braking environment, the damper would act as normal functioning in both directions.
I would allow the engineers to have superior balance over others in hard braking.
Or would the FIA see this as "active suspension".

[hardingfv32]

Is it your hope that locking up the shocks during braking will reduce weight transfer?

Brian

[DaveW]

Could a person design in hydraulic lock up in dampers so that when an electric signal is sent via the brake pedal, it would prevent anymore compressive loading.

The FIA would react if activation was electrical, but that is unnecessary. "G-sensitive" dampers have been around for over 10 years & are used widely, even in F1 I believe, although some teams refrain, claiming they might/should be banned explicitly. Their legality in F1 depends upon an interpretation of the relevant regulation, which reads something like: "dampers shall respond only to vertical wheel inputs". Arguably, changing the effective damper setting does not, by itself, make the damper move. However, if the regulation is interpreted (or changed) to include sensitivity changes, then all dampers would be illegal because their sensitivity changes with temperature.

A g-sensitive damper incorporates a mechanical accelerometer to increase low speed rebound damping whenever the longitudinal deceleration is greater than a threshold value. An alternative solution, activated by brake fluid pressure directly, also exists, but would probably be easier to ban.

[ubrben]

A g-sensitive damper incorporates a mechanical accelerometer to increase low speed rebound damping whenever the longitudinal deceleration is greater than a threshold value. An alternative solution, activated by brake fluid pressure directly, also exists, but would probably be easier to ban.

Presumably this is to hold the rear down to prevent CoP migration, but reduces the rebound for grip reasons once in the corner, and on exit?

Ben

[DaveW]

Presumably this is to hold the rear down to prevent CoP migration, but reduces the rebound for grip reasons once in the corner, and on exit?

It is true that they are to be found most commonly on aero cars, but I believe that some non-aero cars have also found them beneficial. On the other hand, one of my customers with a (mildly) aero vehicle has them fitted, but rarely uses them. Hence, it would be logical to conclude that they help to keep aero under control, but can also work as a "fix" to hide other (probably geometry) issues. The satisfying feature is that they work when required, but don't interfere otherwise.

[munks]

That's why I have to mention that hardingfv's "one molecule thick tyres" would suffer severe degradation through the race: they would go from one molecule thick to zero molecule thick in zero seconds, as you also cannot have grip without spending some rubber, by definition of what grip is.

Sorry to go off on a tangent here, but I have a quibble with this statement. While tearing rubber does generate quite a bit of grip, rubber can produce grip in at least two other ways. What definition of grip are you using that requires rubber to be lost? If I'm not mistaken, even if rubber is torn, the long tangled molecule strands can still be connected or can re-connect themselves to the tire (I'm talking about normal tires here, perhaps not one molecule thick tires!)

[RacingManiac]

Presumably this is to hold the rear down to prevent CoP migration, but reduces the rebound for grip reasons once in the corner, and on exit?

It is true that they are to be found most commonly on aero cars, but I believe that some non-aero cars have also found them beneficial. On the other hand, one of my customers with a (mildly) aero vehicle has them fitted, but rarely uses them. Hence, it would be logical to conclude that they help to keep aero under control, but can also work as a "fix" to hide other (probably geometry) issues. The satisfying feature is that they work when required, but don't interfere otherwise.

Would this function somewhat similarly to the hydraulically linked system like the Kinetic systems?

[DaveW]

Would this function somewhat similarly to the hydraulically linked system like the Kinetic systems?

If you mean this http://en.wikipedia.org/wiki/Kinetic_Dy ... ion_System, or Alex Moulton's Hydragas, http://en.wikipedia.org/wiki/Hydrolastic, then I don't think so. A g-sensitive damper has no effect statically, it simply changes the rate of response of the suspension to a disturbance whilst an acceleration (or deceleration) condition is satisfied. Suspension elements are not cross-linked.

[747heavy]

Could a person design in hydraulic lock up in dampers so that when an electric signal is sent via the brake pedal, it would prevent anymore compressive loading.
This would in fact hold the car at a set ride height during braking allowing a much better / stable car during braking.

As a general technical answer, yes it is possible and has been done (perhaps not in Formula 1-DUNNO) before.
During the mid 80´s you will find systems, working along your idea, on a couple of motorcycles.
Yamaha had a system called BASS (Brake Assisted Suspension System) and Suzuki had their NEAS (New Electrically Activated Suspension)and PDF (Posi Damp Fork) systems.

All these systems used the input of the front brakes, to lock out or increase the low speed damping, in the front fork, trying to avoid or limiting dive under braking.

It was done either by an electrical or via an hydraulic valve which was activated by the front brake pressure.

a principal schematic of such an system you can see here:





If you consider this an advantage or not, will depend on the application (type of car - aero vs. non aero) and the track (smooth vs. bumpy braking zones), and I don´t want to give a blanket statement about this.

[Belatti]

If you consider this an advantage or not, will depend on the application (type of car - aero vs. non aero) and the track (smooth vs. bumpy braking zones), and I don´t want to give a blanket statement about this.

This is very important. A bad setup and you will find yourself jumping in a braking area...

Is it your hope that locking up the shocks during braking will reduce weight transfer?

Brian

May I ask why do you conduct all your posts to these kind of riddles? We all know that the only thing that reduces weight transfer are the ones in the formula you mention its in the literature and you dont seem to accept the fact that, even if the total amount of weight transferred is a fixed value for a given acceleration, you can manage its distribution. 10 will always be 10, but 5+5, too. The same applies with 8+2...

Dead smooth track, infinitely rigid tyres = no suspension nedeed. (instantly weight transferred, intantly vertical force appears in the rigid wheel, instantly generated grip F = "mu" *N )

Dead smooth track, rubber tyres = a suspension needed to increase performance. (this doesnt need and explanation, just the imperfect suspension a tyre is is the reason to improve it)

[DaveW]

If you consider this an advantage or not, will depend on the application (type of car - aero vs. non aero) and the track (smooth vs. bumpy braking zones), and I don´t want to give a blanket statement about this.

This is very important. A bad setup and you will find yourself jumping in a braking area...

You are both correct, of course.

A pressure-actuated damper is probably more relevant for a bike than it is for an F1 vehicle.

Making an acceleration-controlled damper operate accurately & reliably on an F1 vehicle can be difficult, because the operating environment is not exactly "friendly". The peculiar signature of an F1 braking event makes it worth solving those problems, however. To simplify (both the event & the numbers), if brakes are applied for 5 seconds, then deceleration will greater than 2 gn for rather less than 1 second. Hence, if 2 gn is chosen as a threshold, then excess rebound damping will be applied for less than a second per event. That implies, I think, that there is a good chance of controlling centre of pressure migration without compromising mechanical "grip" significantly, regardless of surface irregularities.