[Technique] Suspension Smith

BRUNEAU (sur un autre sujet) a écrit:

Le freinage sur une moto est limité par le mouvement de bascule à moins d'1 g (hors aéro) alors que la limite d'adhérence est du double.

Intéressants les tests de Suspension Smith à ce sujet qui mettent en évidence que cette limite peut être significativement dépassée lors des freinages sur l'angle en profitant de l'apport sur l'arrière de la force latérale engendrée par la prise du virage. C'est donc à ce moment la limite d'adhérence de l'avant (dans une autre direction) qui entre en jeu.

Suspension Smith a écrit:

Heres some testing I did about a year ago with the Hossack blade....the idea was to test the braking capabilitys of the bike.....I had a basic data logger fitted for speed...lean angle and braking deceleration.
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The video shows a max upright braking effort achieving just over 1G of deceleration with the rear coming off the ground and becoming unstable .....then onto the straight and into turn one where most of the braking is done at some degree of lean angle through turn one and running out wide setting up for the entry into turn 2....here a peak of just over 1G is done at a lean of 35 degrees....here the bike is stable and the bike still has great rear traction ....refer to the first Data trace with a vertical line indicating peak braking deceleration and lean angle through turn 1.
When braking upright max braking is limited by the point at which the rear starts to lift.
This shows how cornering force can increase braking potential because some of the Lateral cornering force is pushing down on the rear wheel...the ultimate limit being the amount of grip the front tire has for braking and cornering together.
The second Data trace shows a later lap in which I tried hard to reach the maximum braking potential of the bike at lean.
This shows a max brake deceleration of 1.1G at a lean of 30 degrees with the back just starting to drift slightly....that was enough for me.

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Extrêmement intéressant et pour tout dire, inattendu !

I'm not sure if it's been explained above but the brake on the lateral suspension system is plumbed in to the front brake master cylinder so the lateral suspension is locked solid when the rider is braking upright in a straight line. As the rider enters the corner and begins to release the brake the lateral suspension gradually unlocks.
Also notice that in this design the lateral suspension only works one way. The next revision incorporates 2 dampers to control lateral movement.

Hi everybody....thought I might update this thread with my latest developments.

This project is basically about testing to see if the concept of a lateral front suspension  system is viable and useful.
Now I am not yet making any claims as to its efficacy...but its starting to look promising.

I have recently fitted a 2D data acquisition system to the bike and recently did a trackday and now I am in the process of learning to analyse the data from it....its quite interesting.

So just a quick explanation about the bike....its a 2010 Honda CBR1000rr which has had a Hossack conversion done to the front....I raced it in 2015 to developed and prove the Hossack front suspension...then I started work on the Lateral suspension which i incorporated into the Hossack front...the Hossack front and the lateral suspension were originally designed as one but I thought it prudent to develop the Hossack front first and then incorporate the Lateral suspension.

The two biggest issues I have had with this design is how to configure high quality dampers and springs and the need to lock the lateral suspension when braking.

The dampers and springs now consist of a pair of Canecreek mountain bike air shocks...these are of very high quality being the same working principle as the ohlins TTX dampers.
These have externally adjustable high and low speed Comp and Reb damping.
I have modified them internally so that they both extend and compress...being mounted at half stroke when the Lateral suspension is centred and converted them to a steel coil spring.
The springs I have had custom made to suit the installation.
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I have also developed a magnetic/electromagnetic locking system which with a simple button on the left handle bar allows me to unlock the Lateral suspension on demand...such as when midcorner and about to ride over some midcorner bumps.
The system also has the ability to increase its locking power when braking...ensuring no Lateral movement when braking.

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So far all this has worked very well and now allows me to explore the possibilities of Lateral suspension with safety and control.
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Now heres the interesting bit....this is a data trace from the 2D data logging system.
This shows four lines.
The top light blue line is the rear suspension trace
The pink mostly flat  next lower line is the Lateral suspension trace....when in its centred and locked position it is a flat/straight line.
The next lower orange line is the front Hossack suspension.
The bottom dark blue line is throttle position.

Now in the centre of the picture is showing the bike cornering through turn 3 which is very bumpy at its apex...its ideal for testing the ability of the Lateral suspension to absorb mid corner bumps.

Now the pink Lateral suspension trace is flat before the corner but at some stage I have pushed the button on the left bar and released the Lateral suspension...allowing it to move...then see the pink trace start to move as the Lateral suspension hits those midcorner bumps....you can also see immediately below the orange front suspension trace also rapidly moving as it also hits those same bumps......this taking place at a lean angle of between 50 and 55 degrees and the Lateral suspension movement is around 5mm at the tire........could be that Lateral suspension has something to it....

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We do have some crazy stuff on plb nice job!

Do you have the same graphics when you reach the bumps without releasing you lateral suspension, so we could see the difference between the two situations (front/rear movments)?

What is the difference of feeling (rider feeling is also important, if it allows you more confidence when hitting the bumps!) between using or not using the lateral suspension system? Could you feel a more "loose" bike under your arms, sort of a "cadillac" effect?

Hers a graphic of the same corner but with the Lateral suspension locked...

Notice there is some small Lateral movement of around 1 to 1.5mm so the Lateral  lockout is breaking away...the breakaway force is something in the region of 50kg at the tire so the forces are not small....under brakes this breakaway force is about doubled to around 100kg and I have not experienced any Lateral movement whilst braking....which is good yes.
Notice that the lower data trace of the Hossack suspension appears a little more spikey and maybe because more of the bump force is being transmitted into it rather than being absorbed by the Lateral suspension


On some sections of the track I am now experiencing some breakaway whilst the Lateral suspension is locked during fast changes of direction from left to right etc and this is sometimes felt as a minor movement in the bike...noticeable but not problematic so far.....Frits Overmars has mentioned to me the possibility of this kind of Lateral movement when changing direction as possibly helping in much the same way as counter steering does in shifting the CofG over the line of the wheelbase....so this will be interesting to investigate in the future.

The feel of the Lateral suspension working over those bumps in turn 3 is it does seem to take the edge off the bumps...the data seems to be telling me that the Lateral suspension is presently over damped in Comp and Reb so further adjustment here might see some further improvement...the Lateral spring rate appears to be close.


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Hers another graph of a big moment I had whilst exiting turn 9......I was chasing a much quicker rider and was trying hard to stick with him so was pushing very hard through this corner...there is a bump on the inside of the corner exit and I just glanced it whilst under hard acceleration at a lean angle of around 42 degrees....the tire let go and the rear stepped out and the front broke out into a massive tank slapper as the bike jumped around.....the front gave about three big slaps and then very quickly settled and the bike quickly regained its composure.....the graph shows the Lateral suspension deflecting left to right by up to 27mm at the tire as the front and rear simultaneously compress and extend.
I think that maybe the Lateral suspension in absorbing and dissipating these forces helped save my arse from being thrown down the road...whew!!

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Laurence Smith a écrit:

Notice that the lower data trace of the Hossack suspension appears a little more spikey and maybe because more of the bump force is being transmitted into it rather than being absorbed by the Lateral suspension

What I have also noticed is that the rear suspension data trace is more spikey when lateral suspension is released.
Is it due to the a faster cornering (throttle position data trace seems to indicate a wider opening) or a consequence of the lateral suspension?

MANETON a écrit:

Laurence Smith a écrit:

Notice that the lower data trace of the Hossack suspension appears a little more spikey and maybe because more of the bump force is being transmitted into it rather than being absorbed by the Lateral suspension

What I have also noticed is that the rear suspension data trace is more spikey when lateral suspension is released.
Is it due to the a faster cornering (throttle position data trace seems to indicate a wider opening) or a consequence of the lateral suspension?

Hard to say at this stage....I am still coming to grips with this kind of data analysis...there is loads of information waiting to be deciphered from this kind of thing....I just have to learn the language :-)

I am really looking foreward to the next test day as I feel with some further setup time the Lateral suspension can be made to work much better....its still in a crude state of setup.

Due to the fact that a swigarm has more ability to move in the length of the bike and so can move a lot more with more lean angle, the fact that the front can "flex" better could explain that the rear suspension is also moving a lot more, potentially adapting better with the surface of the track, according to what is happening on the front of the bike, too

Do you record the lean angle of the bike, too? Just to see if your suspension allow more lean angle at a defined point

I still wonder if you're not mistaken in the colors displayed? Couldn't it be the rear suspension in orange and the front suspension in blue?
Just because front suspension normaly have more lenght of travel that the read shock and your graphics show more travel on the back that on the front... Or is it due to the hossack suspension?

crazytoon a écrit:

Do you record the lean angle of the bike, too? Just to see if your suspension allow more lean angle at a defined point

I still wonder if you're not mistaken in the colors displayed? Couldn't it be the rear suspension in orange and the front suspension in blue?
Just because front suspension normaly have more lenght of travel that the read shock and your graphics show more travel on the back that on the front... Or is it due to the hossack suspension?

The lean angle is a work in progress....its too inaccurate at the moment being calculated from the GPS positional data...I am looking at using a single axis Giro sensor to measure lean angle more accurately.....

Colours are definitely correct.........theres a couple of reasons why the rear appears to be using more travel than the rear....one is as you mentioned is the Hossack front suspension....it has a total wheel travel of 100mm and due to its Kinematics it has a much more efficient use of its wheel travel than a telescopic fork.....

The rear suspension uses a Linear rate linkage so it doesn't build as much spring force through its stroke....the track I am riding it on is quite bumpy so this allows more give in the suspension at lean......as a rider I seem to prefer a compliant rear.....

Hers a Vid of the Hossack front in action...as you can see the suspension is quite active and the track quite bumpy.....perfect for testing a Lateral suspension system.....

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