59 replies to this topic

[David Beard]

Difficult to make the twisting blade system anything but either full-stiff (blade vertical) or full-soft (blade horizontal). The McLaren design, using a rubular ARB, is fully adjustable with precise levels of stiffness all the way.

Surely it would need a driver well versed in kidology techniques to convince his race engineer that he could feel effects between the full stiff, full soft, extremes?

[Tony Matthews]

Difficult to make the twisting blade system anything but either full-stiff (blade vertical) or full-soft (blade horizontal).

So how does it react at 45°?

[Nigel Beresford]

Surely it would need a driver well versed in kidology techniques to convince his race engineer that he could feel effects between the full stiff, full soft, extremes?

Not at all - the driver can most definitely feel the change. The thing to be aware of is that you don't get pro rata changes of stiffness with changes in angle, so when designing the adjuster quadrant (that holds the blade in the desired orientation) you need to make the positions of the blade produce near equal step changes in stiffness, not angle. Typically you'll have full stiff, full soft and three intermediate steps.

I would think the problem with the original McLaren system was excessive friction hindering ease of adjustment, then hysteresis & loss of stiffness due to the play required to overcome this problem, plus packaging difficulties (i.e. cable routing). The beauty of the rotating blade is that you can support the blades in decent bearings and get fairly compact adjustment linkages.

Edited by Nigel Beresford, 14 September 2011 - 20:33.

[David Beard]

Not at all - the driver can most definitely feel the change. The thing to be aware of is that you don't get pro rata changes of stiffness with changes in angle, so when designing the adjuster quadrant (that holds the blade in the desired orientation) you need to make the positions of the blade produce near equal step changes in stiffness, not angle.

Wouldn't the driver's ability to feel the difference be heavily influenced by the main suspension spring stiffness?

[Nigel Beresford]

Wouldn't the driver's ability to feel the difference be heavily influenced by the main suspension spring stiffness?

Not really - you have to have your relative stiffnesses outside of a desirable range for that to happen. The principal function of an ARB is to affect the roll stiffness distribution of the car and thus the loads seen by each tyre, thereby optimising the grip generated by the tyres. Therefore the driver, whilst he may perceive more or less platform movement due to an ARB change, is more likely to perceive a change in traction or balance.

Edited by Nigel Beresford, 14 September 2011 - 20:43.

[D-Type]

Stirling Moss refers to the oil injectors on the Mercedes 300SLR in My cars, my career when writing of the Buenos Aires Formule Libre race (where they ran W196 single seaters with the 300SLR engine) he says:

We had some trouble with a locking front drum brake - inboard of course on those early-season long-wheelbase cars - and since there was no time to dtrip it between the heats, its linings were simply squirted with oil. Obviously braking was diminished, but at least it cured the locking, There was a servo in the system anyway, so very high pressuyres could be applied, which would wear down the high-spots in both the brake lining and the drum liner as as the heat burned the oil away. From this Argentine expedient Mercedes rapidly developed the push-button brake-oiling system which subsequently handled locking brakes on the 300SLRs.

Then in the section on the 300SLR at Le Mans he says:

Another Tweak - developed from the temporary expedient in the Argentinian Libre race at the beginning of the year - was a row of four cockpit plungers to squirt oil into locking drum brakes, on the basis that no brake at all was better than one locked up.

As this comes under Le Mans, it implies that these were not fitted for the Mille Miglia. This is borne out by Denis Jenkinson who says in A story of Formula 1 that by the end of the race the car's brake linings had worn away to the extent that the front brakes were metal to metal and the alloy of the shoes had worn measurably. He refers to a front brake tending to grab which spun the car into a ditch. This suggests that the oil plungers weren't fitted.
My apologies for wandering away from the central topic of driver-adjustable brake balance.

[petersracing]

So how does it react at 45°?

The non perpendicular settings produce lots of side loads on the bar and then they deflect all over the place. It introduces all sorts of non linearity. Some of the manufacturers produced double blades, double blades with opposite rotation and all sorts of wacky variations but as Carroll Smith would say it remained an "unnatural act". We ran our RT4 with the bodywork off one day when I was perplexed and when I saw what was happening we reverted to changing bars and set the blades at full hard from that day on.

[Tony Matthews]

As I suspected! I asked for two reasons, 1) because there must be a difference somewhere between full-soft and full-hard, and 2) the 'little' end, without lateral constraints, probably wanders about the place! So, thanks for the explanation. However, as Nigel Beresford pointed out:-

" The thing to be aware of is that you don't get pro rata changes of stiffness with changes in angle, so when designing the adjuster quadrant (that holds the blade in the desired orientation) you need to make the positions of the blade produce near equal step changes in stiffness, not angle. Typically you'll have full stiff, full soft and three intermediate steps."

Apart from the simpler, lighter (?) system that you adopted, there is no facility for anti-roll bar adjustment during the race, but perhaps that is not a great concern. Thanks.

[petersracing]

As I suspected! I asked for two reasons, 1) because there must be a difference somewhere between full-soft and full-hard, and 2) the 'little' end, without lateral constraints, probably wanders about the place! So, thanks for the explanation. However, as Nigel Beresford pointed out:-

" The thing to be aware of is that you don't get pro rata changes of stiffness with changes in angle, so when designing the adjuster quadrant (that holds the blade in the desired orientation) you need to make the positions of the blade produce near equal step changes in stiffness, not angle. Typically you'll have full stiff, full soft and three intermediate steps."

Apart from the simpler, lighter (?) system that you adopted, there is no facility for anti-roll bar adjustment during the race, but perhaps that is not a great concern. Thanks.

It's even worse than Nigel describes. As the bar deflects laterally all the angles go far enough from 90 degrees that it becomes massively non linear. At different roll angles and ride heights it has different effects. Smarter people than me might have been able to deal with it, I just ended up confused and with a car that handled badly all the time. Luckily for me my next car was later and the use of bars had largely abated.

Adjusters were really necessary for long races and changing fuel loads which we weren't doing so it was just a matter of getting enough parts and time to get the thing right before race day rather than trying to play with it in camera.

Edited by petersracing, 20 September 2011 - 06:19.

[Nigel Beresford]

It's even worse than Nigel describes. As the bar deflects laterally all the angles go far enough from 90 degrees that it becomes massively non linear. At different roll angles and ride heights it has different effects. Smarter people than me might have been able to deal with it, I just ended up confused and with a car that handled badly all the time. Luckily for me my next car was later and the use of bars had largely abated.

Adjusters were really necessary for long races and changing fuel loads which we weren't doing so it was just a matter of getting enough parts and time to get the thing right before race day rather than trying to play with it in camera.

Blimey, this really is going back in to my dim, distant past. I remember when I was at Ralt in '86 that Ron incorporated some U section tracks and put bearings at the tip of the blades to run in these tracks, in order to stop this. That's the only time I recall seeing such things. Nowadays the blades typically aren't so long and the problem is less.