Anti pitch/squat bar.. bizzare question!

[Zico]

Ok, dont laugh...

My friend was showing me his very impressive RC Racing set-up and we got talking about vehicle dynamics.
He told me that some guys at his club had been testing Anti Pitch and squat bars on their RC cars. My understanding of that was either 1 bar connected to the front-rear suspension that worked just like an anti- roll bar except longitudally for pitch and squat (weight transfer) of course... OR maybe 2 diagonal bars going to each opposing corner of the RC car.

He asked if the WRC cars used them.. and why not?

He went on to tell me that braking distances are much improved, that the cars corner far flatter and faster and that with an active centre diff, a WRC car would be the perfect platform.

Although I'd never heard of them before other than the hydraulic systems in road cars.. I dismissed the idea as stupid and explained that longitudal weight transfer is a very important dynamic to have in rally cars as they need this high adjustability at the expense of outright grip.... as opposed to a circuit car where the track has been lapped many times, the lines and the braking points are very well known.

He argued that they could use a squeezable variable brake balance control lever (or handbrake) on the steering wheel.. and had good thought provoking answers for everthing I countered with.

Imo.. On imagining the dynamics and what would be required to make it work its simply too complicated, with questions on how the car would react on jumps, rough ground and a totally unnatural driving style would be required, the very opposite direction rally should be headed imo... but I told him Id ask others opinions on here..

So?

[MrJan]

I'd have thought that it'd play havoc with the Scadinavian flick which is pretty much used by everyone.

The brake balance thing is probably viable but it would make something like a hairpin very tricky as the driver would be a tad busy.

Ultimately there is a penalty for a vehicle being too stiff and I've have thought that at fast, flowing events like NZ and the 1000 Lakes it would be more of a penalty as it would actually hamper the way that the car can shift from corner to corner.

Obviously with my very, very limited technical and racing knowledge this is all just armchair supposition but my first impression is that it's something for toys (eh, bet that's drive him nuts) and could be altered for a full size car.

[Buzz Lightyear]

i think ford uses a system to control anti-dive/pitch via their reiger dampers.

[Rani]

I read a bit on the subject and it seems that the aforementioned bars aren't needed because anti squat/dive can be managed by simply changing suspension geometry on each independent wheel. Also, hi tech shock absorbers which can differentiate between hitting a bump (fast harsh hit) and braking/cornering/acceleration forces (slower loading) are commonly used. These can be set up to resist diving/squating while still able to soak up bumps. This is probably what Buzz is referring to.

[RS]

I would have thought this kind of system would be more important on tarmac rallies.

And I don't know when I last saw a scandinavian flick in WRC, lol!

[Zico]

I read a bit on the subject and it seems that the aforementioned bars aren't needed because anti squat/dive can be managed by simply changing suspension geometry on each independent wheel. Also, hi tech shock absorbers which can differentiate between hitting a bump (fast harsh hit) and braking/cornering/acceleration forces (slower loading) are commonly used. These can be set up to resist diving/squating while still able to soak up bumps. This is probably what Buzz is referring to.

Thanks Rani, that explains it very well, I imagine a RC cars tiny damper would be extremely difficult to cheaply manufacture and accurately tune within the equipment capacity of your average RC racer, hence this alternative solution.

[mickiedaniels]

we were having this discussion as well yesterday. glad i read RAni's reply so i would have a good answer.