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Active suspension?


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#1 NRoshier

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Posted 20 January 2020 - 08:58

With current technology available for a home enthusiast what would be required for active suspension? I've been told of a local car running some and I'm curious as to what is required - I'm assuming this is active in the sense for ride height, thus 'spring' rate and roll control.



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#2 HP

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Posted 20 January 2020 - 13:58

Albeit a racing car, I think that what they do is feasible for a road car.

 



#3 Greg Locock

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Posted 20 January 2020 - 19:38

Usual approach is to use gas springs for ride height control and fancy pants electronically controllable shocks. The gas springs would have a pretty slow response time, I don't think you'd be able to fake an active sta bar with them. As to that, you could motorize the rotating blade type the SAE use, or put a ballscrew into a drop link, or do something clever at the D block (imagine having D block bolts that you could adjust in length). Or you could replace a droplink with a hydraulic cylinder. Slightly more elegant is to use Kinetik's cross coupled shock absorbers, which can be used as a full authority active system.

 

Thinking about it you can probably get almost everything you need from these, if you can drive them https://en.wikipedia.../wiki/MagneRide .


Edited by Greg Locock, 20 January 2020 - 19:40.


#4 NRoshier

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Posted 20 January 2020 - 20:54

I have a feeling from what I have seen that the cross linked suspension is what is being used. I have seen very little though - the car is usually kept in a locked garage between races. I imagine the time attack cars have started to use this, though I have not been paying attention to them.



#5 Greg Locock

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Posted 21 January 2020 - 06:26

UWA ran the Kinetik system in their FSAE-A car a few years back so I'd guess anyone involved with that would be happy with crosslinking the shocks, and adding valves in any future car.



#6 NRoshier

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Posted 21 January 2020 - 07:51

From memory the F1 systems were high pressure. What I have seen has a combination of springs and plumbing. I assume the springs keep things off the ground if the system fails or could you use the springs as part of the system to reduce the amount of pressures involved?



#7 Greg Locock

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Posted 22 January 2020 - 07:54

Yes that was one trick Lotus missed (or decided against) on their 1987 era active. Also the Lotus system had a very high bandwidth and so needed to be able to exert large dynamic forces. I can't remember the pump size but it was several kW.

 

A system that uses conventional, but automatically adjusted, shocks can self energise, it doesn't need a pump, and to some extent it could even jack the ride height, rather less reliably.



#8 NRoshier

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Posted 23 January 2020 - 05:06

It would be interesting to know the reasons for the decisions made by Lotus. I'll follow up the system some more when I can - it's not easy as the owner won't talk about it. Part of me gets excited by the potential, but then I have to remind myself that I find conventional dampers and springs challenging enough.



#9 Greg Locock

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Posted 23 January 2020 - 05:44

I was talking to an FSAE team and they fitted various fancy pants adjustable gizmos to improve handling, but of course ran out of time to tune them and set them to default.



#10 NRoshier

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Posted 23 January 2020 - 14:04

Many FSAE teams forget to finish in time and familiarize the driver with the car and driving tasks. This is where teams like Monash, do very well. I recently passed on my 4-way adjustable Sachs dampers for the very reason that I was never going to get to use them well enough to make a difference.