Roll Bar Adjuster

[itdontgo]

Hi,

My Mondiale M89S has a cockpit rear roll bar adjuster which is a bit knackered. The cable is very stiff and the knob is broken. If I change this to an electronic adjustment would this still comply with all regulations? I suppose specifically for events like the BRSCC Kent championships and Wlater Hayes etc...

Thanks

[grumpyf14d]

The rules state that you can have cockpit adjustment of the roll bars but do not state that it has to be mechanical in nature just that you can do it. Something electric I would imagine would take a system that would add some weight if you cared.

[itdontgo]

Thanks. It won't add weight it will reduce it as those linear actuators are lighters than the current cable mechanism.

[chris bailey]

Originally Posted by itdontgo

Thanks. It won't add weight it will reduce it as those linear actuators are lighters than the current cable mechanism.

What a brilliant idea! I think I need this solution for my Sports 2000 rear bar. Can you get actuators that will position wherever you want to allow for complete adjustability? How much power will it need? What sort of control unit?

[itdontgo]

Is you bar a blade type? My car has a mechanical cable at the moment so it's easy to swap this with a linear actuator. It will take power when changing position only.

I could design some custom controller to store various positions... which I suppose you could change corner by corner although you'd never rotate one of those blade whilst the car is rolling (i.e. leaning and stressing the bar). For example it would be good to go a little softer at the rear for the start of a lap on the Silverstone National and a bit stiffer for the latter part I'd imagine.

[chris bailey]

The Swift uses a blade at one end only, adjusted by cable as you'd expect. The blade solution is not the best, given that it's an undamped spring which only works reliably in the full-stiff position. Your actuator solution would tempt me into designing a slider system on a conventional anti-roll bar arm. My query was about how you control the positioning function at intermediate stages between full soft and full hard.

[itdontgo]

Originally Posted by chris bailey

The Swift uses a blade at one end only, adjusted by cable as you'd expect. The blade solution is not the best, given that it's an undamped spring which only works reliably in the full-stiff position. Your actuator solution would tempt me into designing a slider system on a conventional anti-roll bar arm. My query was about how you control the positioning function at intermediate stages between full soft and full hard.

What so it's like stiff or no bar? The Mondiale has buckled the static blade so it must be possible to overload it when in the stiff position.

The positioning would have to be done with a closed loop control system so there would be a linear position sensor as well as the linear actuator controlled with a microcontroller. That's the plan anyway! I have an electronics company http://www.adventcontrols.co.uk so it shouldn't be a problem to get it built up.

[chris bailey]

[QUOTE=itdontgo;3336708]What so it's like stiff or no bar? The Mondiale has buckled the static blade so it must be possible to overload it when in the stiff position.

The blade is full stiff in the vertical mode, and is much stronger than the fixed arm at the other end, which is why that will always fail first. Mind you, the roll bar itself would normally twist and "take a set" before the arm gives up!? The blade, in its full soft setting, is a floppy old thing which doesn't do a good job of transmitting load without deflecting significantly. That's where you get your undamped spring effect. As you progress towards full stiff, the deflection reduces. Thus the bar is more effective as you increase the stiffness position of the blade, but not in a linear sense. A conventional twin-arm anti-roll bar, with a slider mechanism to adjust the drop-link position (on either or both arms) is a better solution, but harder to engineer, due in the main to stiction issues. Your actuator, assuming it has enough power, would probably overcome this, hence my excitement!!

[itdontgo]

I don't think the load will be the issue:

http://www.ebay.co.uk/itm/12v-dc-Linear-Actuator-6000N-600kg-push-pull-load-/170931096239?pt=UK_BOI_Industrial_Automation_Control_ET&var=&hash=item27cc498aaf

First one I came to!

[itdontgo]

Actually it's a bit big that one!

[chris bailey]

Originally Posted by itdontgo

Actually it's a bit big that one!

They say that size matters! You are obviously in a good position to prototype this solution, given your day job is broadly in the same area of technology. If you can prove it works effectively and package the hardware at reasonable cost, then you could have a very marketable product. I'd join the queue to buy it!