Exploring the legality of the Lotus anti dive system

Posted: January 22, 2012 in Formula 1, Technology
Tags: , , , , ,

Although the FIA has now found the device to be illegal, it is yet unclear on what grounds this decision was based on. There are a few possible reasons, and I would like to go through them with you. It’s an interesting exercise and, in a sense, reveals the ambiguity that is often embedded within the rules. It also serves to show how brilliant engineer minds can invent stuff that are well beyond anything the FIA technical rules can foresee.

Before we start, let’s get our basics straight. The Lotus device is a project that is being developed since, allegedly, January 2010. Bob Bell who recently switched from Lotus (Renault, at the time) to Mercedes apparently took the idea with him and the Brackley based team are said to be ready to run such a system in 2012. The same more or less applies to Ferrari who are reported to have developed a similar system. The rumours that go round, and which have not been verified at this stage, are that Red Bull have been in fact running such a system for at least a year and a half, which allowed them to run increased rake without fear of the endplates touching the ground, and possibly run softer suspension solutions. It’s not clear at the moment whether McLaren or any other team had plans to run the device in 2012. Judging by how stiff the McLaren was sprung at the front end, one would imagine that they didn’t have any such solution in 2011.

The device was a simple technical solution, and it’s a development of ideas that first appeared in motorbikes in the early 80s. It consists of a master hydraulic cylinder which is powered by the brake torque to raise the push rod of the suspension, thereby preventing the car from diving under braking. This apparently means that the pushrod will be of a telescopic design. The consequences of that will be examined later on.

Let’s see now on what basis the device may have been banned. We will refer to the 2012 Technical Rules, which is a good read anyway.

1. Paragraph 3.15 – “Aerodynamic influence”

“No part having an aerodynamic influence and no part of the bodywork, with the exception of the skid block in 3.13 above, may under any circumstances be located below the reference plane”

One would expect that the cylinders, located at the lower part of the brake ducts, would always be above the reference plane. However, it’s questionable whether this can be guaranteed for an entire race and under any circumstance. Imagine a scenario where a F1 car goes hard over a kerb. The suspension will compress and the wheel will rise dramatically in relation to the sprung part of the car. It would be hard to prove that every part of the device remains above the reference plane, unless (a) the limit of the suspension travel is such that the device remains above the reference plane or (b) they install proximity sensors which can provide data at the end of the race regarding the relative position of the lower part of the device to the ground. In any case, this rule was specifically written to prevent the teams from fitting any sort of flaps, turning vanes, etc below the reference plane, but if we accept that this device alters the aerodynamic characteristics of the car, then the rule should apply to it as well.

2. Paragraph 3.15 – “Aerodynamic Influence”

“Any device or construction that is designed to bridge the gap between the sprung part of the car and the ground is prohibited under all circumstances.”

As we have explored in previous blogs, the device does indeed contribute to manipulating the ride height of the car during braking. More specifically, the device is designed to increase the gap at the front (in comparison to what the gap would be if the device was not fitted) and, as a consequence, decrease the gap at the back.

It then all depends on how one interprets the term “bridge the gap”. Apparently this rule was written as such to prevent side skirts that completely connect the ground to the car, creating the notorious ground effect. Most engineers would translate “bridge the gap” as connecting the car to the ground. However, one may argue that this term can also refer to bringing the car closer to the ground artificially; it’s a matter of interpretation. One can say why such an argument may be a bit thin, but if the FIA want (for political reasons, or whatever) to ban the device, then it is a possibility.

3. Paragraph 3.15 – “Aerodynamic Influence”

“With the exception of the parts necessary for the adjustment described in Article 3.18, any car system, device or procedure which uses driver movement as a means of altering the aerodynamic characteristics of the car is prohibited.”

That’s a juicy one. There is no question that the car alters the aerodynamic characteristics of the car. That’s partly what it’s designed to do. A car that approaches the corners at the designed rake is aerodynamically more balanced and predictable than a car which exhibits dive characteristics. There is the counter-argument that every component of a car actually alters the aerodynamic characteristics of a car – from the brakes to the steering wheel. However, none of these parts’ purpose and design is to change the aero characteristics.

The big question is whether it uses driver movement as a means to alter the characteristics or not. As we now know, the device is primarily activated by the brake torque (using a floating-type caliper), which means that it is, actually, not activated by the driver. However, the brake torque comes as a consequence of a driver putting his foot on the brake pedal. Although the device’s primary activating force is the brake torque, it would never become active if the driver hadn’t moved to press the brake pedal. One can see why some tend to argue that it is a driver-operated device. Let’s take this extreme scenario: Instead of the cylinders raising the push rod, they actually raise a winglet that is hidden in the car’s nose-cone (using the same brake torque as a means of power). In such a case, the winglet emerges and adds downforce at the front end at a crucial stage (during braking and cornering), i.e. at the time when more downforce and drag is actually needed. Wouldn’t that be a case of a driver-operated aerodynamic device?

I think it would be.

4. Paragraph 3.15 – “Aerodynamic Influence”

“With the exception of the driver adjustable bodywork described in Article 3.18 (in addition to minimal parts solely associated with its actuation) and the ducts described in Article 11.4, any specific part of the car influencing its aerodynamic performance: (…)

(…) – Must be rigidly secured to the entirely sprung part of the car (rigidly secured means not having any degree of freedom).”

If we accept that this device influences the aerodynamic performance of the car (which it does), then it possibly breaches that rule as well, since it is housed inside the brake ducts, it is therefore not rigidly secured on any part of the sprung part of the car. On the contrary, it enjoys the same degrees of freedom that the brake duct does. One could argue that this device is part of the duct, therefore it should be exempt according to the first sentence, however this is highly debatable. Although they are mounted inside the ducts, they are not part of the duct nor do they contribute in its operation / scope. They are there for entirely different reason than brake cooling.

5. Paragraph 10.3.4 – “Suspension members”

“Non-structural parts of suspension members are considered bodywork.”

I post this rule because I’ve seen several people arguing that the device cannot be considered “bodywork”, because it’s part of the suspension. Actually, the above rule makes it quite clear that, since it’s not part of the suspension members’ structure, it should be considered as bodywork, just like the brake ducts are considered bodywork (and not suspension) and fall under the bodywork rules in terms of dimensions.

6. Paragraph 10.3.5 – “Suspension members”

“Redundant suspension members are not allowed.”

If this device is considered to be part of the suspension, then it can be regarded as “redundant” because it doesn’t contribute in the suspension of the car. I remain of the opinion though that this device should be considered as bodywork, and therefore it’s hard to see anybody referring to this rule.

7. Paragraph 10.2.2 – “Suspension geometry”

“Any powered device which is capable of altering the configuration or affecting the performance of any part of the suspension system is forbidden.”

Another juicy one and it comes down to how you define “powered”. If by “powered” they mean externally powered by a source such as a battery or the car’s engine, then this device would not fall foul of this rule. If however the term “powered” is more general (which can be interpreted as such), then one can argue that the device is indeed powered by the brake torque and it’s not self-actuating (i.e. it’s not a rigid structure reacting to external forces such as a wing providing downforce, but it’s a mechanical device using moving parts who require some form of external power to operate).

In such a scenario, this device clearly alters the configuration of the suspension, since it raises the push rod (by extending its length), and it falls foul of the rule.

8. Paragraph 10.2.3 – “Suspension geometry”

“No adjustment may be made to the suspension system while the car is in motion.”

If you recall at the beginning of this post we talked about the pushrod being of telescopic design. This is necessary to allow the push rod to “raise” and thereby increase the ride height under braking. However, this is a clear adjustment of the suspension system which is being done while the car is in motion.

I’ve seen people argue that the suspension adjusts all the time (springs compressing, dampers going up and down, etc) but this is entirely different, because it’s not a result of the suspension reacting to the forces from the ground and the car; it’s rather an induced adjustment that includes the alteration of a suspension member’s length. It’s hard to see how one can argue that this device is not in breach of that specific rule.

As a brief conclusion, I am not amazed that the device was eventually banned. With so many rules in probable / possible breach of, it’s a small miracle it was allowed in the first place.

  1. TC3000 says:

    I appreciate your work Abu, so please don´t feel offended, let me just ask some questions in regard to some of your statements and interpretations.

    The suspension will compress and the wheel will rise dramatically in relation to the sprung part of the car. It would be hard to prove that every part of the device remains above the reference plane,
    the above rule makes it quite clear that, since it’s not part of the suspension members’ structure, it should be considered as bodywork,
    If this device is considered to be part of the suspension, then it can be regarded as “redundant” because it doesn’t contribute in the suspension of the car.
    I’ve seen people argue that the suspension adjusts all the time (springs compressing, dampers going up and down, etc) but this is entirely different, because it’s not a result of the suspension reacting to the forces from the ground and the car; it’s rather an induced adjustment that includes the alteration of a suspension member’s length.
    but this is entirely different, because it’s not a result of the suspension reacting to the forces from the ground and the car
    So a damper or spring compressing, changing it´s length as an result, is not due to forces from the ground and/or the car?
    Why is the spring then compressing, if there is no force?

    What do you make of Ferrari´s "dual rate ARB" ? (see here. http://scarbsf1.wordpress.com/2011/06/10/ferrari-rear-dual-rate-anti-roll-bar/)
    A spring loaded link between the rocker and the ARB, which changes it´s length during operation. Why this is not illegal? if a suspension member cannot change it´s length now?

    Looking forward to you answers & keep up the good work
    best regards

    • abu says:

      Hey!!! Great to see you here mate, I really appreciate your taking the time…

      Don’t worry about offending me; usually that takes a lot more than arguing about the various technical aspects of F1. Besides I am just an F1 fan; you know, the annoying type. This blog is not of the high technical calibre of scarbs or about breaking news and inside info; it’s just my way of sharing thoughts about my favourite sport and discussing – nothing more. I am an engineer too, although I don’t work in F1 (or cars; I am a marine engineer), and I find the technical aspect by far the most fascinating. I am always up for a good discussion.

      So, to the point: Maybe me English is poor and my explanation didn’t come across well. I am suggesting that a damper or a spring compressing do indeed change their length as a result of forces being exerted on them, either from the car (aero pushing down, rolling, pitching, diving under braking, squat) or the road (bumps, cambers, kerbs, etc) or a combination of both. The same applies to Ferrari’s dual rate ARB. As the car rolls, it’s the softer spring that compresses first (and changes its length as a result). With more roll, the hard spring kicks in, which provides a sort of solid link between the ARB and the suspension rocker. All the above (spings, dampers, dual-rate ARBs, etc) are members who alter their length by reacting to forces.

      I am suggesting that the adjustment of length of the push rod in Lotus’ system does not come as a result of reacting to forces from the car or the grounds (as is the case in all the above examples), but as a result of an indirect order from the driver; the driver pushes the brake pedal, and that “activates” the hydraulic cylinders (via the mechanism that we all know) who raise the pushrod, thereby extending its length. My argument is that that spirit of the rule suggests that any chance in any suspension member’s length should be “passive”, i.e. a result of reacting to extrenal forces, and not a result of a driver’s order, however indirect this may be.

      Again, it comes down to an interpretation of the rules; I guess one could argue (like you do) that since other suspension members change their length why shouldn’t the pushrod be also allowed to?

      Thanks again mate.


  2. TC3000 says:

    you are welcome,
    I don´t know what happened, looks like that your blog has “eaten” all the other comments I made.
    Maybe it did not like the use of >> and < braking force in longitudinal direction at the wheel contact patch, this force multiplied by the radius of the tyre, gives the “brake toque” everybody is talking about.
    If the car would be not in contact with the road, or driving on ice, the system would do nothing or very little, does not matter how hard the driver brakes (how much brake pressure we have).
    This system at the rear of the car, would not need any brake pressure at all, because it would act on engine braking &/or KERS charging as well.
    It´s function is not direct proportional to brake pressure –> driver input.

    Anyway, it´s banned now.
    But what about a car which runs more then 100% anti-dive (let´s say 130%) at the front ??
    Would this car lift the front wing/nose under braking?
    And if yes, would this be a direct result of braking force?
    Think about it for a moment.

  3. TC3000 says:

    sorry something is really strange, half my post is missing again – apologize.
    Just mind about the last questions for a bit,

    • abu says:

      Yeah – it probably has to do with the symbols you inserted (I don’t dare use them in case the blog eats up my comments as well).

      Oh well, to the point: I see what you mean that the function is not directly proportional to brake pressure. However, given fixed and consistant friction coefficients, it should be, shouldn’t it?

      Of course we also have to consider how the car unloads aerodynamically at the front as the speed goes down… I would expect that the nose would lift (or, if you prefer, doesn’t drop as much) as the speed goes down, simply because the aero isn’t pushing down anymore, so the amount that the nose raises (or doesn’t drop) would be a function of both the device acting on it and the aero decreasing…

      As for the 130% anti-dive, I would assume that teams would run with fixed telescopic lengths for their pushrods, so as not to allow the nose to raise beyond a certain pre-determined point. They would have to factor in the aero effect on that, but it can be done?

  4. TC3000 says:

    well I think, Article 10.2.1 in the technical reglement will “kill” it quite nicely, without any need to
    “bend” / freely interpret other rules, or use the “catch all” aerodynamic influence one.

    Yes, given a constant CoF of friction on the tire, the brake force/torque would be proportional to brake pressure, if we assume the CoF at the brake pad/disc does not change (which it does with temperature).

    But the CoF of the tire is a direct function of the vertical load on the tire, and any disturbance (bumps) will affect it (as I tried to show, with the graphs I posted on the autosport forum).

    Anyway – you could run more then 100% anti-dive and the nose would lift under braking (at least theoretical), practical people will not run this amount of anti- dive, as the drivers will complain, and the car would be complete crap on a bumpy track.
    Nevertheless, you could achieve the same effect as with this system, but with other drawbacks.

    as for the other comment, yes, the nose/front wing will lift, as the speed goes down.
    The main advantage of the system, would have been, that it could compensate for the “tire squash” – deflection of the front tires, due to the load transfer during braking. As the tire is much softer then the front suspension under these conditions, “locking out” the front suspension will not help much, as most of the deflection is in the tires anyway.
    So you could have keeped your rake/front ride height at the designed level, while still being able to ride the bumps with an compliant (softer) suspension. Best of two worlds if you like, but for now
    it looks like, that it is dead in the water.

    • abu says:

      Hadn’t though about the brake temperatures, yeah. So, let’s see if I get this: The load from the aero and the “diving” effect is still loading the tyre, therefore the tyre squash remains, the only difference being that the nose doesn’t dive, which allows for increased rake (at zero loads) and a softer suspension. That’s a shame. Such a brilliant idea. I understand that you work in other categories of motorsport; do you have anything similar to the Lotus system?

      Oh, and one more thing: Just imagine how fantastically this device would have worked with McLaren’s third brake pedal. You could use the third brake pedal to activate the cylinders on one side during turning, and that would elliminate the rolling…

  5. TC3000 says:

    in simple terms, try to picture in your mind two springs on top of each other and a weight (load).
    the first spring (standing on your table/ground) is the “tire” , the second spring on top of the first one, is your suspension spring. Then you put a weight/load on top of both springs. (this load is the weight of the car+downforce+loadtransfer effects from braking).
    What will happen? Both springs will compress, according to there spring rates and the weight you put on the top, will move closer to the table/ground. [the two springs in series are forming a combined spring of K combined = 1/(1/K suspension + 1/K tire)]
    Even, if you replace the spring on top with a solid (infinite spring stiffness), the lower spring, the tire, will still compress under the load, and your weight will come closer to the table/ground.
    In numerical terms, the fist spring (suspension) would need to extend under load, to compensate for the deflection of the other spring (tire), if you wanted to keep the weight/load at the same height about the table/ground – negative spring stiffness on one spring if you like.
    This system would do something like this, picture that you would “automatically” put a spacer between your two springs, which is exactly the same length as what both springs would compress under the applied load.

    In the series I work in, such systems would be not allowed, as we have restrictions as which brakes etc. we can use. As I said in the autosport thread, so find similar systems on some downhill mountain bikes, and some Off road /MX motorcycles, but there it is normally used at the rear, in the opposite direction (not to push up the front, but to pull down the rear).
    I have seen this done on some FWD Touring Cars during the mid 90´s, on the rear as well.
    With a similar system, as on the bikes (mechanical linkage between the brake caliper and the chassis), to reduce the rear lift of the car under braking.
    It did work, and some teams used it for a while.
    But it is heavier then a standard layout, so over time, it became “out of fashion” again,

    There is rarely any “free cheese”, so at some point, there is a price to pay, for the advantage a system (in general) offers.
    The question is, if you see the “price” as worth it compared to the benefit or not.
    And sometimes, the “price” you need to pay, is just “too high” so you will do without the benefit.

    Have fun
    Good luck & all the best with your blog

    • abu says:

      Your comments have increased my understanding at least as much as several years of following so called “experts”‘ websites and articles.

      Thank you.

      And thanks for taking the time off your schedule to reply – I just wish more people were reading your comments here.

      Perhaps I may post something, now that it’s all clear in my head, making reference to your comments, if that’s fine with you.

      See you around 🙂

  6. TC3000 says:

    yes – all good
    good luck

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