Bonnet lifting, again.....

[browrz]

This problem just wont go away….I've got new rubber things to receive the locking rods and all seems secure before you set off. But over a certain speed (nothing outrageous) I can see the bonnet straining to go. It seems to flex and lift to the point of then popping free from the rods before levitating in front of me. I've even felt the open/close wheel under the dash start to turn as it goes (mine doesn’t seem to have the ball bearing locking 'click' that I have heard some mention…maybe that’s needed here?

I hear that the mysterious chin spoiler blade (that I don’t have) is supposed to cut down airflow under the car which is claimed to be partly responsible for pressure build up under the bonnet? But I'd imagine its mostly air into the radiator opening getting into the engine bay. Either way there is quite a force at work here and I'm wondering if some kind of airflow control is the more clever way to solve this vs just modification of the locking mechanism?

I am sure im not the first to have this issue but welcome thoughts….
thx

[Tanguero]

A chin spoiler helps to some extent, but I think you will need the 'click' on the locking mechanism as well. Also check to see if you can adjust the locking pins outward.

[Greeny]

Replace the chin spoiler.

[FUBAR]

Have you adjusted the rods (well, the end bit)? I say that as mine did as you describe on a trip to the Ring a few years back until one of our esteemed brothers pointed out I could adjust them . Never been a problem since.

[FarmyardPants]

FUBAR said:

Have you adjusted the rods (well, the end bit)? I say that as mine did as you describe on a trip to the Ring a few years back until one of our esteemed brothers pointed out I could adjust them . Never been a problem since.

Don't have them too tight though as the rods can bend or snap. You defo need the ball bearing as Tangoman says. The blade will help as well.

[browrz]

Thanks for the help! Any pointers on the specifics;

-- Source of a new spoiler?

-- The 'click' function on the opening know...is that just a case of rebuilding the mechanism, or any tips on that?

-- Advice on how to get to the rods to extend?

thx!

[FarmyardPants]

browrz said:

Thanks for the help! Any pointers on the specifics;

-- Source of a new spoiler?
Try SimonKD on here

-- The 'click' function on the opening know...is that just a case of rebuilding the mechanism, or any tips on that?
I think the ball bearing runs in a groove on the shaft, and at the point of locking goes into a deeper indentation at the end of the groove, giving the click which stops the shaft turning further and offers resistance to it turning back, if that makes sense. You need to check that the ball and spring is there (Mr Cerbera posted a pic on another thread recently)

-- Advice on how to get to the rods to extend?
The white plastic bits unscrew, which moves them outwards

thx!

[neal1980]

I had this problem on the chimaera the bonnet flew up at 140mph. After that I decided flush fit bonnet pins were the only way I would trust. Now fine forever.

Neal

[Greeny]

Simon has the chin spoilers for sale in the classifieds

[browrz]

Thanks again guys.
Will investigate!

Still find it quite hard to fathom the airflow thats going on here. I'd imagine a high pressure zone above the bonnet and in front of the windscreen. But what I hadn't considered was the impact of the airflow in and under the car.

Is the consensus that its mostly airflow under the car that feeds up inside the engine bay? Or air in via the radiator opening? Given the F1 plate and the relative lack of space around the AJP I find the latter more likely? But then the spoiler wouldn’t have any effect?

…where I'm getting to here is that this could all indicate a poor aero setup of the Cerb design in general and hence something that could be improved to avoid the car being lifted slightly at speed?

[browrz]

neal1980 said:

I had this problem on the chimaera the bonnet flew up at 140mph. After that I decided flush fit bonnet pins were the only way I would trust. Now fine forever.

Neal

Do you have a picture?