Too simple to be effective?

[greenpower dude reloaded]

OK, starting to look towards my next project (whilst developing the E-racer further expect an update soon)

Now before I start explaining this thought I feel I ought to mention I've done very little with suspension, and I am about to read competition car suspension.

So here's the concept..

[Mystery Steve]

So are you intending for this to work similar to a J-damper, which is only active during jounce and not during body roll? Or have I misinterpreted your drawing?

[greenpower dude reloaded]

In all honesty, I originally did it because I thought that it meant that I could package everything tighter and promote a clean through flow of air. I thought about rocker arm but this would place the shocks in a far more practical position.

I obviously don't want to persue this seemingly overly simple suspension method if it's going to be totally unsuitable for any vehicle.

It's a track car so I don't want to encorage roll, but natrually need to be able to soak up a little (very little) amount of road surface.

[wesley123]

What i seem to understand from it that in a turn the outside wheel will get pressed upwards, thus loading the spring. This energy the spring contains will be given to the right wheel pushing it on the ground thus having more contact patch.
Dont know if i understood it correctly, but in that case wouldnt the camber differ every time in a turn?

[greenpower dude reloaded]

Sorry it was just a quick thing I knocked up in flash of all progs.

The camber shouldn't change as the wishbones should maintain the correct angle, once designed correctly

[Ciro Pabón]

I remember that maybe 10 or 15 years ago they did something (with a linear generator instead of a hydraulic shock absorber) at Tufts University: it was suited to charge electric vehicles, so I guess it's a winner with you.

I'll check to see what I find: what I know is that one or two years ago the idea was recycled (ha, ha) and I read again about it.

We also had a thread where we estimated, crudely, the amount of energy disipated in the suspension during a race. I cannot find it, maldición. I'll have to ask the mods.

[Mystery Steve]

I remember that maybe 10 or 15 years ago they did something (with a linear generator instead of a hydraulic shock absorber) at Tufts University: it was suited to charge electric vehicles, so I guess it's a winner with you.

This is what I thought you were going for, green. Figured this was for an electric vehicle.

Not sure about the feasibility of this, as I am just thinking out loud here. But the J-damper works when the eyelets are pushed toward (or away from) each other, and when this happens the threaded portion causes the red area to rotate, which is surrounded by fluid, which resists the rotating motion. Perhaps instead of fluid, you could have the threaded part rotate a rotor inside a stator and act as a generator? Or maybe go the other way and use it as a semi-self-powered active suspension? I'm not a EE, and I'm not an expert in electrical control theory, so maybe this just a far fetched idea. Interesting to think about at least.

[greenpower dude reloaded]

Ahh I see, I like the thought of that.

To be honest, this is just a quick picture I knocked up a few weeks ago to show one of the people that has helped us out from time to time by contributing some of his own knowledge to previous projects.

I very nearly removed the KERS bit but for ease left it in.

This vehicle will indeed be electrically motivated and so a regenerative shock is definitely an option I'd like to consider. Your idea Mystery Steve sounds great, however I suspect it would take a lot of very careful designing so I'll probably aim to get an off the shelf system of which I remember reading about in the past and have also seen at the Autosport show. (I wish I'd hung around long enough to get a business card now)

But really the question is, Is the set up I have there, in principle, likely to be effective enough in circuit racing? How could/would a system like this compare to a J-damper or monoshock set up.

Also what are the major things needed to be considered when designing something like this?

I know this is all incredibly vague and probably not enough to make educated decisions but I want to know whether this method is worth pursuing OR whether trying to simplify things here is actually making it all far more complicated.

[stolenmojo]

once you begin iterating some potential motion ratios and stiffness values to the rockers and spring there I believe some trends will appear. if i consider the individual modes the wheels would move in (single wheel bump, roll, heave and warp if you consider the whole vehicle at some point) the single value for spring stiffness is going to be ideal in only one of the modes. i.e. its going to have great roll control but very harsh ride, or nice ride rate and nearly zero roll control. active damping could be some fix for this but to really control it you would be back to a full active hydraulic ram and servo valve so that a "stiffness" could be assigned based on vehicle accelerations.

single seater monoshock setups still separate the roll and ride modes because typically you need much different rates between those two. single wheel bump can be compromised unless the circuit is very rough.

[tok-tokkie]

On your diagram you have 'much like an anti-roll bar'. It is, in fact, quite the opposite to an anti roll bar. If the left wheel is lifted in roll then a conventional anti-roll bar tries to lift the right wheel also. Yours does just the opposite.

[Ciro Pabón]

... But really the question is, Is the set up I have there, in principle, likely to be effective enough in circuit racing?
...

Ok, Ok, we got it. There you go, I found the post I made, that includes a crude estimate of the energy you can get from a regenerative front suspension (trying to guess how much a shock absorber would heat in a race). Enjoy, and criticize, if you're so kind:

Sure, a damper or shock absorber (SA for short) is like a resistor. In all types of SA, energy is absorbed by friction forces and converted into heat. These friction forces are proportional to the velocity of friction elements.

That heat surely goes into the liquid or gas that is inside the SA, minus what it radiates. The amount of radiation, judging by the form factor most SA have, does not seem to be the main concern of the designer (no SA with cooling fins are popular, AFAIK).

F1 SA, I imagine, must generate low heat, compared with a normal damper. First, the "resistance" is limited, because the friction forces are limited, because the amplitude of movement is limited, because:

1. F1 cars have "hard" suspensions
2. F1 cars ride low

Second, the "current" you have, or load of the SA, is smaller than in a normal car:

3. F1 cars weigh less than most cars

Anyway, let's put some rough numbers to it, following a long tradition of amateurs in this site...

The IRI (I've mentioned it before, it's the International Roughness Index) tells you how many millimeters moves up and down the body of a car when it moves through 1 meter of road. I repost the IRI model car, Mikey_s knows it better than me, I'll say only that Ms is the body mass, Mus is the suspension's and that xs is the movement of the body:

IRI model of a "quarter-car": just one wheel with one spring and one shock absorber


I suppose F1 tracks have an IRI of, let's say 2 mm/m (it could be 3, maybe, but I do not want to open the calculator, so I'll round a lot from now on).

Take in account this "quarter car" used as reference has springs, weights and SA that are different from the ones an F1 car has, which means more "travel" of the body.

Anyway, let's imagine a car on a track of 5 km with 75 laps. Without calculator I round that to 400 km. The car must move up and down 800 m through the entire race (at 2 mm per meter of track).

Of course, this is the "throughtput" of energy through the resistor, not the energy damped (on the contrary, it represents the energy NOT damped, but let's assume they are of the same order of magnitude). With a gravity of 10 m/s2 I get:

Energy = m*g*h = 600 kg * 10 m/s2 * 800 m = 5 Mjoules

If the race takes 1.5 hours, which is like 5.000 seconds, give or take, you have:

Power = 5.000.000 Joules / 5.000 seconds = 1 Kwatt

This is more like 500 watts if you take in account that half of the energy (at least, if no more) goes to the rear shock absorbers.

Now, there are other things, beside SA, that adsorb energy, that is, wheels and springs, shown on the posted picture as "kt" and "ks". Let's assume that wheels and springs dissipate only half of the energy, even if that's probably conservative for an F1 car, famous for relying on wheels to provide shock absorbing power.

We arrive to a power around 250 watts, which is like three light bulbs. That's enough to keep your legs a tad warmer than my taste. Anyway, part of this heat surely can be managed by simple cooling systems.

As far as I remember, there have been posted in this site some pictures showing air vents on top of the frontal part of the cockpit, surely for cooling. I suppose the energy of the body inside a fire suit is larger than the numbers I got.

Surely I must have made some mistakes, I appreciate if somebody has the time or the interest to point them out.

I apologize for quoting myself. Conclusion: you get around 250 watts. Please, take in a account that a road where your fanny moves up and down only 2 mm per meter is a extremely smooth road (a new one). If the road is bumpier, you'll get more energy, of course. A very rough road (dirt road, full of potholes) can give you an IRI of 12 to 15 tops (mm per meter, that is).

About how effective the system is, well: I find the idea exciting. Following stolenmojo line of thought, you can modulate the energy adsorbed by changing the "friction" of the magnetically dampened flying wheel, isn't it? There are many devices that use that principle, like the flywheel KERS systems used in computer uninterrupted energy systems (Pentadyne, for example), so the circuitry and the algorithms already exist, you might buy them (yeah, sure, you need to work harder or earn more, I know ).

Modulated electronic KERS flywheel (Williams is not there yet! )



That is forbidden in F1, but you (or better yet, your sister) is not racing in F1... for the moment.

[manchild]

Ciro, you have an energy of MIT nerdiest nerd. When I look at your analytic posts, it makes me think "Where he gets the optimism, strength, stamina... for such exhausting posts?"

[Mystery Steve]

Sorry for derailing your thread there. You know how it is when you get an interesting idea in your head... and yeah, it would definitely take some work. It hasn't even made it to the paper napkin sketch stage yet.

To answer you original question: Yes. I do think it is too simple to work, assuming I've interpreted what you've drawn of course. I'm interpreting it as something like this, only both sides are connected to a single spring/damper. If that is the case, then you have essentially the same setup as the J-damper. The problem with that is it doesn't work in roll (the "J" stands for jounce), as it only works when the wheels are moving in the same direction.

[greenpower dude reloaded]

Wow, Ok then guys plenty there to think about there. I met someone at the Cleaner Racing Conference (pre-autosport) who appeared to be a very helpful young graduate who'd just joined Williams Hybird. Maybe, I ought to ask his advice in due course.

OK OK Lets open this up. The cats well and truly out the bag as is. I'm not going to say where this vehicle will compete but we are now working on the initial, conceptual designs for a fully functioning electric racing car. The next(MASSIVE) step up from greenpower. Which we still intend on competing in for many years to come, as it provides a fantastic training ground/test bed for this new thing.

As I previously mention one of my passions is the aero side of things so I want to try and keep things squeaky clean. Suspension is the first major area I am seriously lacking the know how in. Most other areas are purely a development from my electric car.

So back to suspension. I want nothing more than two wishbones supporting either wheel. How does rocker arm suspension compare with most other modern methods?

Notes
Manchild - yes I quite agree, but would we want him any other way??
tok-tokkie - Yeah, you are right, I had a worry about that last night after posting but thought it shouldd put more load which (with my knowledge) could go either way.

[mep]

Hey I just saw your first picture and heard something like saving energy and initially got the idea of producing some electrical energy with the dampers.
Especially with the simple J damper layout this could get a really good design.

I think there is a quite simple solution for making roll and ride independent.
The problem is more that the spindle tries to move the rotating wheel in both directions while moving in and out. For producing energy its better when the wheel just gets moved in one direction.
Nevertheless I would really like to develop such a system because I think it’s a really smart idea.