From: ericrhays <eric.r.hays@...>
Subject: [Tilting] Re: Wheel Diameter as Speed Calculator Problem for Rounded Leaning Tires
To: tilting@yahoogroups.com
Date: Wednesday, July 8, 2009, 3:18 PM

FYI, there is in fact one production example of a 3 wheeler that features ABS.  It is the BRP CanAm Spyder.  It uses a brake system designed by Hayes Brakes and Bosch.  So, it's a problem that has been overcome and put in production.  And, if it's true that the rounded tire profile will have little influence on the system, then there isn't any reason why a similar ABS system couldn't be fitted to a tilter. 

Eric Hays

--- In tilting@yahoogroups.com, "nsampson58" <nikal58@...> wrote:
>
> Hi all
>
> Stop bothereing about this point; ABS, if needed, will easily cope with these differances.
>
> Firstly the distance travelled per rev is calculated from diameter times Pi so the total effect is reduced.  The differance in diameter between upright and tilted will not be much so the total effect will be hardly noticed. As pointed out it is speed differance that matters so if they are all tilted it does not matter. ABS also checks that 1 wheel is stopped whilst others are still moving quite fast so it is not small differances that matter.
>
> Secondly these effects are far less than the differances that ABS has to allow for in a 4 wheel vehicle going around a simple corner.  The distance traveled by each wheel in say going round a simple 90 deg corner, at a constant vehicle speed, will vary quite a bit. 
>
> This is not the issue with ABS the main difficulty is that there is no such thing as an Off-The-Shelf ABS.  They all need setting and tuning, lots of engineers playing around on frozen lakes, not cheap...!  The other issue is that so far they have only been designed for 2, 4 or more wheels.. not 3, perhaps we can fit 2 sensors to the single wheel and make the system think there are 4 wheels... mmm perhaps not that easy.
>
> Regards
> Nick Sampson
>
> PS anyone found that illusive rich investor...? or are you keeping it to yourselves.
>
>
> --- In tilting@yahoogroups.com, Alan Braggins <alan.braggins@> wrote:
> >
> > Mitch Casto wrote:
> > > I was just thinking that there is a problem using Rounded Leaning Tires
> > > as a factor in speed calculations. When the wheel(s) are vertical the
> > > diameter is considerably larger and when leaning. The higher the tire
> > > sidewall height and the greater the roundness, the more apparent this
> > > becomes. Can this cause a diameter variation of 10 percent or more ?
> >
> > It would have to be quite a small fat tyre for that much, surely?
> >
> >
> > > Front and Rear Wheels have different overall heights, widths and curve
> > > shapes which makes things even more complicated. At Full Lean, the bike
> > > ( or tilting 3 or 4 wheeler ) has quite a different set of wheels than
> > > when not tilted. This would change basic factors for math modeling and
> > > practical applications such as Anti-Lock Braking ( ABS ). AntiLock
> > > Braking depends on the wheel diameter to determine the bikes actual
> > > speed, but the wheel diameter is smaller when the vehicle is leaning.
> >
> > Surely the significant thing to ABS is the difference between wheel
> > speeds, not the absolute speeds? Unless you do something like compare
> > wheel speeds with a Doppler radar road speed in order to detect a four
> > wheel skid, but I thought normal practice was to detect a wheel which
> > was rotating less fast than the others. So long as all the wheels are
> > changed by the same factor, it will still work.
> >
> > I suppose if you use an extreme camber angle like the Milliken MX1, and
> > then tilt as well, then one side of your vehicle will have upright wheels
> > while the other side has leaning wheels, but is that a likely setup?
> >
> > Hmm - maybe it would cause a problem if you have something like one fat
> > back tyre and two skinnier front ones, so you move different amounts
> > round the tyres for the same lean, then you will detect a false differential
> > speed between the front and rear tyres when leaning.
> >
> > And more so if not all three wheels lean - I'd forgotten that as a
> > possibility. Okay, I think that might be a potential problem for an
> > off-the-shelf ABS unit.
> >
>




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