- When it comes to getting the ultimate lap time out of any car, it really comes down
to the tyre contact patch between those four tyres and the racetrack that's going to
define how much grip is available.
Of course, optimising that comes down in a large part to the damper selection and the
damper tuning.
So we're here with Dejan from Tractive Suspension to find out a little bit more
about what goes into that.
Now Dejan for a start I really want to talk about the Tractive Suspension setup,
you're running this in the RP968, it's just become the second fastest car
ever to go around Eastern Creek with a 1:19.2.
Dangerously close to the outright lap record and of course the suspension plays a big
part in that.
So can you just talk us through the Tractive Suspension in terms of the damper
arrangement that you've got in this car?
- So Tractive Suspension has a proprietary valve, it's called a DDA valve and basically
they are electronically variable.
So the damping is not just like a normal construction, it has a valve inside which
helps vary the flow.
So if you looked at it from the outside, you wouldn't be able to tell that it's an
electronic shock because it looks the same.
Most of the construction is the same, we've got a piston, shim stack,
gas pressure, canister et cetera.
But behind the piston is a little solenoid and that solenoid can open and close
160 times a second and stop anywhere in between.
So we can vary the current which varies the damping rate anywhere,
every six milliseconds.
- OK so basically what you're talking about there is the ability to actively change the
bump and rebound damping on the fly as the car goes around the track.
Now let's just take it back a little bit, dumb it down a little bit and for those
who aren't really aware of how that valving plays a part in the motion of the damper,
can you sort of talk us through that?
- So the damper curve or the valving is speed dependent, so the force,
the resistance that the damper provides, it's ability to control both the wheel,
like a wheel control and the body.
In fact the damper is probably one of the most important elements on the car which
has lots of variable jobs.
So in the shape of the curve we have a bleed rate, we have a transition rate,
we have a high speed rate and so the damper then has to control various aspects
and the various forces that are coming through it.
- So in rough terms there we're talking about the fact that depending on the speed
the damper's moving, so for example as the driver turns the wheel and the car tends to
try and roll over, the damper is in charge of controlling that motion.
So relatively low speed and then you've got undulations in the road which are a higher
speed and then of course if the driver runs a ripple strip or something like that,
there's an instant shock and the damper needs to bleed off very quickly.
All of that is really, needs to be optimised in order to keep the contact patch of the tyre
optimised?
- Yeah that's correct and most basic dampers, most normal dampers these days have
special valves, they have special pistons, they have shim stacks that are pre loaded,
so internally their constructions are quite good and we can get, like you know you
see most of the cars around here get pretty good lap times.
But when it comes to maintaining and maximising the grip of the contact patch
and maximising the aero platform, having the variable damping means that
you can optimise different parts of the curve with different parts of the track.
- Alright so your Tractive dampers that are in the RP968, you've still got an external
reservoir with what looks on face value to be a conventional adjustment for bump
and rebound?
So that works in conjunction with the electronic valve?
- Exactly so the electronic valve is basically like an overall damper.
So you could buy Tractive shocks without the canisters and you just have the valve internally
and then it just operates just like a normal bypass valve but electronically.
We add the canisters so that we can get more bump and rebound variation.
So for example, if you have really bumpy circuits or road that you're running on,
you can then fine tune the compression resistance, the bump, the high speed and
low speed so that it's tailored to that.
However the valve, it predominantly will do a lot more to the body control but we also
know how to vary it so we can get better wheel control as well.
- So could we sort of break that down and consider the manual adjustment for bump
and rebound as a coarse adjustment to get in the ballpark and then the electronic
valving is fine tuning within that?
- It's like fine tuning, so here we're pretty much heaved into bump rubbers most
of the way around the circuit.
We tune our bump rubber stiffness in our packers but then we tune our high speed
and low speed compression so we can get the feed into those bump rubbers nice and smooth.
So you can do that with the valve but the best thing about it is that you can do it
externally too so that, you know as the car's coming along.
And the benefit of that is that we've also got shim stack blow off, we've got the
canister and we can adjust the gas pressure as well, so there's a lot of variations
that we can do.
For a lot of the people that play with shock absorbers, they probably don't
even know what high speed and low speed can do for them.
For those people that do see the benefits of having canisters and then on top of that
now you can put an electronic valve, so you've got a whole range that you're just
basically pushing the damper to a bigger and bigger window.
- Now I just want to go back in unpack something you just mentioned there, you said about
running down onto the bump rubbers.
And this is a problem we see with cars with a lot of downforce.
Basically at very high speeds, they're producing so much downforce that the
car is physically being pushed down onto the ground.
So you compromise, either you run a very high spring rate so that the car
doesn't do that but that then compromises the low speed cornering performance
so the bump rubber is a decision you make to compromise that, that whole setup?
- Yeah so a normal spring arrangement, your resistance is a linear function of your
displacement.
So what we do now with these cars, and a lot of people do, it's not new
technology, is that we run some preload on the springs and that lifts the curve up,
then we have a linear spring which is quite firm still because we don't keep them
sloppy because if you have it soft then the unloaded side lifts.
So you need to manage the inside as well as the outside.
And then you introduce your bump rubbers and they have to be quite progressive,
so you have this curve which is now, used to be a straight line but now it's
got a step, a ramp and a curve and we want to operated in that window so our energy
absorption is managed, we get the right amount of energy absorption,
the right end point, so that the balance then comes, the shock is basically holding the
car but not disturbing it and causing it to bump.
- Alright so getting down a little deeper into the electronic valving as well.
So you've got some quite flash functionality around this in terms of the way the driver
can then control or adjust the damping on the fly to suit his preferences.
So you've got, I think you said, five stages of adjustment for that?
- In the basic setup of the TCU, we can provide a driver with five adjustments.
That's the most basic, and we can pre program those five with a range of input variables.
We can also have, especially for street car uses 'cause we do have a street car range,
a touch screen display.
And then they can choose roll and pitch and heave independently.
So in a racecar application we tend to like to put just five modes for the driver and
something like a MoTeC dash can do this where it can send via CAN a signal and say
select mode one and the driver can do that.
Or it could say OK select mode two.
And so the benefit then is that we can have an external device that can also
select the modes for us so it's not just a driver selection.
Currently we're just doing a driver selection, today that's all we've been doing.
'Cause we've been fine tuning bits and pieces of it but you can have an electronic
device like a MoTeC that will look at variables like lap distance,
like vertical Gs in the chassis or GPS, whatever you want.
- So that leads me to that next part which is really quite an exciting aspect of it.
Because of course depending on the particular area of the track, the speed,
whether the track's bumpy or smooth in that area, you may actually get better
performance with a particular damping profile.
So as you just mentioned there, you're looking at something like lap distance,
you could then use the lap distance output from the MoTeC dash or any dash for that
matter, to then alter the damping profile for different parts of the track?
- Yeah and we were running that last year, we had, we knew what we wanted turn one,
we knew what we wanted so when lap distance was 600 metres and then
700 and 800 and we were switching between modes it sort of gets a little bit confusing
for the driver and then it gets a little bit confusing for the engineer as well 'cause
you have to look back and say where were we.
And especially if you transition from one mode to another.
- Alright look Dejan it's a really interesting technology and obviously working
incredibly well here on the RP968.
Thanks for the chat and if our viewers do want to find out more about Tractive
Suspension, where can they go to?
- So obviously they can go to tractivesuspension.com and us as the
Australian and New Zealand distributor, they can go to ttsuspension.com.
- Perfect thanks a lot.
- Yeah thanks a lot.
- If you liked that video make sure you give it a thumbs up
and if you're not already a subscriber, make sure you're subscribed.
We release a new video every week.
And if you like free stuff, we've got a great deal for you.
Click the link in the description to claim your free spot to our next live lesson.