Anti Dive/Squat bar

[Rozza]

Came up with an idea to control dive/squat, works very similar to a arb but connects the front and rear rather than either side. Had a look around the internet can't find and information on any similar device. Basically my question is could this be an idea which would be beneficial? could be made adjustable like an arb?

Quick mock up-

http://img840.imageshack.us/img840/8239/adbk.jpg


Mark

[Caito]

I get the idea. You can control anti dive/squat with suspension geometry. Racing-wise this would add weight, solving something you could solve changing wishbone inclination(in case of double a arm). Anti dive-squat generally generates instant weight transfer, your system wouldn't.

You'd need one for the left and another one for the right.

I don't know if dive generates as much trouble as roll does. Nor I know dive/squat angles to justify such a design. There users that really know in this forum and will be more able to help you.


Is it too complicated to try your design? Is it specifically for R/C?

PS: forgot to add, in current f1 cars there's a 3rd spring in the rear to control rear height.

[RH1300S]

What would happen is that a front wheel bump would try to lift the rear wheel at the same time. Also you get the same effect in dive/squat - whichever end is going down will try and lift the wheels at the opposite end - surely a recipe for corner entry oversteer and corner exit understeer. Also, an undamped spring in the equation.

Packaging would be fun (probably much easier in the RC that a real life car).

The third spring route is tunable, easier to package and lighter (a bar of that length would need to be pretty stout to have much spring rate).

Nice idea though....

[mep]

If I ever had to connect the front with the rear I would probably do it with hydraulics.

-It offers you many possible ways to solve your problem and you can build in lots of smart gimmicks like flow valves, springs, dampers...

-The density of oil is many times lower than that of steel so you save weight.

-It's much easier to route a flexible tube from front to rear than a solid bar.

-You can also make it driver activated. You could switch it of or change its characteristics during the drive. Try this with an ordinary suspension.

Before you take that step you should make the antirolbar linkage hydraulically operated. In an advanced step you put in a spring and a damper in the circuit. Then you move all the stuff together including all dampers, springs, flow valves etc. in a single housing. By this you save lots of space and can therefore improve your packaging. A company (damper producer) could sell this as black box to the teams.

[747heavy]

you will find mentioning of such systems in most chassis/suspension books
here an example:



http://www.1956packardpanther.com/Panth ... Level.html



Mep is correct, that in recent times, most people attempt to do an "interconnected suspension" via hydraulics or pneumatics.
Most notably is the KINETIC system, which is used in the McLaren MP4-12C sports car, and which was used in Citroen WRC and Rally Raid cars, before such systems got banned.

Here some links to interconnected suspensions:

http://www.creuat.com/Technology.html
http://members.tripod.com/austin_america/id48.html

You will find more info´s about such systems in the McLaren MP4-12C thread and if you search for interconnected suspension on the web.

I´m not sure a hydraulic system is feasible for an RC-Car (weight) but perhaps an pneumatic system, taking the main springs into consideration could be worth a test.

On another note:
a third spring layout will control pitch/squat, but will also influence heave and ride heigth (which for an aero race car is the main consideration), where the proposed system of the poster will only affect pitch/squat but not heave.
Similar to an anti-roll bar (sway bar) will only affect roll but not heave or pitch.

So a 3rd spring layout is not the best substitude for the proposed system - IMHO.

Good luck !!!

[mep]

Ahh there you have it again, you are never the first one that comes up with a idea. I think a RC or FSAE car is a nice playground to test out such technologies. The problem with pneumatics is that air is compressible and therefore it can be hard to optimize the setup with a compressible fluid. Well it can also be advantageous when you want to use it as antirolbar conection. You then have this little spring effect. Adjustment can be done by increasing the pressure of the system.
A simple hydraulical connection must not be very complicated to build. I would not start with connecting front to rear but with replacing the antirollbar with a hydraulical connection. You just connect the damper of one side with the other one by a tube. Then you can build in a flow valve as damper. To get the spring effect is little bit harder to achieve but for sure also possible.

[Ciro Pabón]

Well, I think that the first car to have a suspension similar to the one you propose was the Citroen 2CV, whose suspension was designed by Alphonse Forceau, back in 1937...

Here is a picture of this famous suspension. There was a thread on this, where someone posted the 2CV famous 1950 advertisement, carrying a crate of eggs through a field.

This design has a large advantage over mep's proposal: it's not only an anti squat mechanism, it is also the whole suspension (except for the dampers located on each wheel) AND gives you four wheel independent suspension, IF you wish. Conclusion: there is always a better way.

These cylinders were located on both sides of the car. Each spring was connected to the front or rear wheel in their respective side.


This Citroën was the avatar of our (lost) member Tom, the guy from Scotland, who passed his driving test while being part of our esteemed fellowship at F1Tech. He could have give you some lessons about the system.

This is another picture of a real 2CV suspension:



And here is another diagram that (I expect) will make VERY clear how it works. Notice how the springs connected to the front/rear wheels can work against each other inside the main cylinder. The threads allowed you to adjust the height of each corner, btw:



This particular suspension was comically soft. You could rock the car side to side with one hand... OR (in case you were racing Midgets, I guess) you could use the thread in each push bar to incline the car as much as you wished. Ain't it cool, cousin Billy Joe?



I remember once when I was in high school that a group of friends (and myself) pushed and lifted one of these cars, that belonged to the school Principal, by hand, up four floors, from the parking lot to the library...

Thank heavens the stairs of our school were really wide. Somehow during this feat, still remembered in our school after 35 years, the front left wheel passed over my foot. No harm done. So, it wasn't only anti squat: it was also anti squash. Ha, ha, how funny I am.

The Principal had to hire some guys to bring this car down again to the parking lot. I still chuckle remembering THAT.

We were never caught, so I, sincerely, hope my old Principal doesn't read this post. I still help him when one of "his" poor communities needs a road or a bridge, gratis. It must be the guilty feeling I still have. Mwahahahaha.

Oh, youth, divine treasure...

Sorry, I have to post a last picture of this radical car:

1937 prototype. No, the one light on the right side of the picture is all it had. Notice the design of the body: it doubled as an structural part.



And, finally, a picture of Boulanger, the guy that designed this car to give you 78 mpg. Famously, he raised the roof of his "umbrella on four wheels" (his words, not mine) to be able to wear a hat while driving. The car could accelerate from 0 to 100 kph in one day, give or take... or so people said. The seats were hammocks, suspended by wires from the roof if you wish to calibrate the incredible coolness factor of this car.



So, Rozza, your idea is a good one, or at least I think so.

As Caito remarks, at least in NASCAR, anti squat is achieved through a different mechanism, one that involves twisting the A-arms to achieve essentially the same feat. You use the A-arms in torsion to get the same result. Of course, there was a very long thread on this, a couple of years ago, or maybe more. Perhaps someone would be so kind as to disinter it.

[Formula None]

Oh yeah. Inboard brakes and mass dampers as well!

And if it breaks down, you can cut it in half and make a motorcycle with .

http://jalopnik.com/5343163/stuck-in-de ... itroen-2cv



Direct drum to tire transmission baby!

Here's one converted, it seems, to independent suspension, but you can clearly see the leading/trailing arm suspension actuation:

[Rozza]

Thanks for the replys!, its not for any particular vehicle or rc car it's just an idea I had whilst playing on a rally game, couldn't get the old 037 set up how I wanted!. Some interesting stuff you guys know! just another thought I had, if the anti dive bar I suggested was used as well as conventional arbs front and rear what effect would this have? over bumps I can see it being horrible, as all four corners would be connected. I like the hydraulic solution, do they use accumulators as dampers?

Mark

[747heavy]

if you would like to add roll control to your "Squat Bars", you would need to connect the wheels diagonal ( e.g. the front left with the rear right) via your torsion bars.

Sometimes, these layouts where called Z-bar or X-bar suspensions.

Some other interconnected suspension systems/ideas



this is maybe a good read, to cover some basics and different ideas for implementation.

http://www.freepatentsonline.com/6702265.pdf

for a hydraulic system

http://www.freepatentsonline.com/7168720.pdf