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3 Coilover Pushrod Suspension?

04/10/2018 8:46 PM

What is the purpose of the 3rd coilover and associated linkage in this suspension:

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#1

Re: 3 coilover pushrod suspension?

04/10/2018 9:17 PM

I'd say, just because it looks cool; because nobody's done it before; if two springs are good, three must be better; Betcha don't know why I did this?

Or, maybe it goes up Pikes Peak really fast.

PRI 2015: Lovefab Enviate Pikes Peak Hill Climber

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#2

Re: 3 coilover pushrod suspension?

04/10/2018 9:20 PM

This explains it.

"A pushrod setup allows designers to stick the dampers, springs, and any ancillary components in the center of the car. The more the suspension is moved towards the center of the car, and the lower the center of gravity, the less body roll and more efficiently the suspension moves. Finally, the geometry of levers and pivot points permits maximum movements to be transmitted into minimally sized equipment, which further reduces overall weight."

http://www.turnology.com/tech-stories/brakes-suspension/appeal-pushrod-suspension/

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#3

Re: 3 coilover pushrod suspension?

04/10/2018 9:43 PM

The 2 rearmost assemblies act as normal, a rising wheel on either side compresses the spring and shocker on that side, the front assembly then comes into play with the linkages (that you can see on either side of the front unit) causing the opposite unit to extend, thus enabling double damping and also keeping the other wheel firmly planted by forcing it downward.

The front spring and shocker enable the front linkage set to allow for both wheels to rise together as required whilst still providing the fore-mentioned effects.

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#4
In reply to #3

Re: 3 coilover pushrod suspension?

04/10/2018 10:02 PM

Um, this is the rear of the car.

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#6
In reply to #4

Re: 3 coilover pushrod suspension?

04/10/2018 10:31 PM

I was actually looking at your pic when I posted, my mistake.

Just substitute front for rear and vice versa in my comments and the same effects will still apply.

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#5

Re: 3 coilover pushrod suspension?

04/10/2018 10:13 PM

Looking at it from the standpoint of an electrical engineer, the third coil-over is analogous to an analog adder with a gain of one-half. I would say that under common-mode displacement of the wheels, each wheel sees the forces from it's own coil-over and one-half of the forces from the shared coil-over so it adds to the spring rate/damping under these conditions.

However, if one wheel is displaced up by some distance, and the other wheel is displaced down by the same distance, the rocking couple at the aft end of the shared coil-over would not cause the shared coil-over to change its length and hence there is no net increase in spring rate/damping for equal differential movements.

So it appears to actually act the opposite of a sway bar interestingly enough. Maybe it helps keep rubber on the road through turns?

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#7

Re: 3 coilover pushrod suspension?

04/10/2018 10:31 PM

It's a downforce shock....

..."The suspension for this single-seater is derived from the ultra high-performance arrangements of Formula 1 and IndyCar contemporaries. Pushrod-actuated QA1 coilovers are mounted cleverly to provide independent damping and roll control.

“Each wheel has it’s own shock, and the black vertical bar is the actual sway bar. When both shocks activate it compresses the third (center) shock, which is a down-force shock. The car is going to make three to four tons of downforce,” boasted Loveland."....

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#8
In reply to #7

Re: 3 coilover pushrod suspension?

04/10/2018 11:01 PM

I call BS. One step was left out.

"When both shocks activate it compresses the third (center) shock, which is a down-force shock. [Then a miracle happens] and the car is going to make three to four tons of downforce.”

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#9
In reply to #8

Re: 3 coilover pushrod suspension?

04/11/2018 12:27 AM

The downforce is supplied by the wing at speed plus the weight of the car and road surface bumps....my take is that all the forces together make 3 to 4 tons at max, so the shock acts as a 2nd tier suspension damper...The primary shocks probably are tuned for less weight, being that the car only weighs about 1800 lbs...

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#10
In reply to #9

Re: 3 coilover pushrod suspension?

04/11/2018 12:35 PM

Unless the angle of attack of the wing, or the speed of the vehicle, increases, just how can you put "more down force" on the tires?

Like I said, a miracle must happen!

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#11
In reply to #10

Re: 3 coilover pushrod suspension?

04/11/2018 2:23 PM

Well if you hit a bump in the road at high speed, this dampers the recoil of the tires...keeps them from bouncing, thus giving more control and surefootedness to the vehicle...at least that's my take....I don't think they put them on there because it "looks cool", although in truth, it does...It's the 'Flux Capacitor' of suspension systems...

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#12
In reply to #11

Re: 3 coilover pushrod suspension?

04/11/2018 4:35 PM

That decreases the rebound of the tire, it does not increase the down force on it, except for the added spring resistance. That energy must be accounted for somewhere within the system, usually in the form of heat in the shock oil. At no time does it add down force to the tires or the vehicle.

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#13
In reply to #12

Re: 3 coilover pushrod suspension?

04/11/2018 5:53 PM

The middle shock uses the down force of the wing to push down on the tires when severe road conditions cause excessive up force...

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#14
In reply to #13

Re: 3 coilover pushrod suspension?

04/11/2018 6:10 PM

"The middle shock uses the down force of the wing to push down on the tires when severe road conditions cause excessive up force"

So what happens to the down force of the wing when severe road conditions don't cause excessive up force?

If the speed, or attack angle, don't change the down force exerted on the top of the wing can't change.

Are you suggesting that the down force moves from side to side as a tire moves upward because of the middle shock?

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#15
In reply to #14

Re: 3 coilover pushrod suspension?

04/11/2018 7:48 PM

It might to some degree.....but instead of downforce let's use resistance, that seems more appropriate....

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#16
In reply to #15

Re: 3 coilover pushrod suspension?

04/11/2018 11:06 PM

Newton's third law is at work here. Down force is being applied by a compressible fluid, air.

The tire hits a bump, car goes up.

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#17
In reply to #16

Re: 3 coilover pushrod suspension?

04/12/2018 2:40 AM

Yes but that's the whole idea, to keep the up to a minimum...ideally the car stays straight and level and just the tires ride up...

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#20
In reply to #17

Re: 3 coilover pushrod suspension?

04/12/2018 11:01 AM

Gentlemen and others,

The suspension is designed to keep the tires in contact with the road for as much of the time as possible with enough force to ensure control and power transmission. The suspension is designed to continually float somewhere around or slightly less than mid stroke and the damping set just high enough to prevent the spring/mass network from going into oscillation.

In this case someone split the rear end vertical travel into two parallel spring/dampers in series with a single spring/damper. I can see that doing so makes the system a little easier to tune for single tire perturbation and for dual tire perturbation, but the same thing could be done in any number of ways with any number of spring/damper combinations.

This is just one that seems to work with the appropriate sound bites to make it seem plausible that it is better than something else already out in the market. No different than any other workable engineering solution.

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#18

Re: 3 Coilover Pushrod Suspension?

04/12/2018 10:04 AM

The main advantage I see of setting it up this way is to allow for easier adjustments. The center coil-over could be easily changed to compensate for more or less downforce due to different wing configurations, speeds, track conditions etc. without changing the roll couple.

In a conventional setup changing spring rates also changes roll couple.

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#19

Re: 3 Coilover Pushrod Suspension?

04/12/2018 10:59 AM

Well, there's more to this than meets the eye:

The third coilover comes into play when the chassis moves vertically (called "heave") with the wheels on either side in phase. It's purpose is to control pitching and nose dive on braking. But there is also a vertical torque bar from the pivot to the frame, which provides anti-roll. Crews can change the coilover settings and torque bar selection for different tracks and conditions.

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#21

Re: 3 Coilover Pushrod Suspension?

04/12/2018 12:19 PM

The point is, and always has been that down force is only equal to the weight of the vehicle and the amount of downward force created by the wing/wings moving through the air. This clever looking suspension contraption cannot generate any down force on its own. It can redistribute it to some degree.

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#22
In reply to #21

Re: 3 Coilover Pushrod Suspension?

04/12/2018 2:16 PM

It's strictly distribution. which is the point of the thing.

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#23
In reply to #22

Re: 3 Coilover Pushrod Suspension?

04/12/2018 2:41 PM

This statement would indicate otherwise:

"When both shocks activate it compresses the third (center) shock, which is a down-force shock. The car is going to make three to four tons of downforce,” boasted Loveland."....

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#24
In reply to #23

Re: 3 Coilover Pushrod Suspension?

04/12/2018 3:48 PM

Not really. If the car mass and vertical acceleration plus airfoil equals 3 to 4 tons, then the suspension will distribute that 3 to 4 tons. Imagine the car going around a tight turn on a high bank at high speed, perhaps pulling 4+g's plus airfoil effect and you get to that loading.

Otherwise, boastful fluff by a salesman. I've heard similar fluff from backpack blower manufacturers where there is an advertised maximum flow volume (with a large outlet - not mentioned) and a maximum nozzle velocity (with a small nozzle - not mentioned). What isn't stated is that you can't have both at the same time.

More likely, the suspension is designed to bottom out at 3 to 4 tons loading.

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#25
In reply to #24

Re: 3 Coilover Pushrod Suspension?

04/13/2018 12:57 PM

I don't know about you, but I've driven to the summit of Pikes Peak and there's just not much road that isn't curvy and flat. That wing won't be providing much down force when it's most needed.

The car weighs 1,800# so the wing needs to do a lot of pushing down.

Maybe it's worth the added cost and complexity and opportunity for additional mechanical failure. After seeing some of the things they do to NASCAR cars to gain an extra .1 second, who knows, it may give them the winning edge?

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#26
In reply to #25

Re: 3 Coilover Pushrod Suspension?

04/13/2018 4:17 PM

looking at the original photo, that sure isn't a NASCAR vehicle. I suspect it's intended for a banked course where you can pull a couple of g's.

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#27
In reply to #26

Re: 3 Coilover Pushrod Suspension?

04/13/2018 4:48 PM

No, not NASCAR. Pikes Peak hill climber. PRI 2015: Lovefab Enviate Pikes Peak Hill Climber Turnology

NASCAR racers look like this, after they hit the wall.

And yes, it did leave a mark.

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#28
In reply to #27

Re: 3 Coilover Pushrod Suspension?

04/13/2018 5:05 PM

OK, so not banking turns, but doing a lot of up and down launch and land. Per the article it's based on formula 1 and Indy and the previous iteration of the suspension broke. That explains the expanded force capacity. So how far do you have to fall to generate 3 g's?

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