JPSC Forum

Hi there,

Just thought I'd share a bit of woodwork that I have been playing at.
Basically I've been wondering about the MIRA windtunnel results that indicated front end lift for a while and a bit of plywood seemed like a good way to go.

It is very solid and survives the local speed humps and in my mind (at least) it seems to make the steering firmer at speed (only local dual carriageway so not properly fast).








Ignore that bit of aluminium!

More spurious details on my blog ( http://matt-phoenix.blogspot.co.uk/ )

Matt

Interesting stuff. I may have to get you to make me a new bonnet hinge and spitter. I wonder about two things with your initial design....

1. Should the splitter not extend to cover the outer edge of the tyre (viewed from the front)
2. You may find you need brake ducts on track as there will be reduced airflow over them

Jeff,

Thanks for your thoughts on the Mk1.

1. You will notice that the splitter is 1220mm wide, which is the same width as standard plywood sheet (bigger would have required me to put the roof-rack on to get it home).
2. Definitely something to look out for. I definitely need to get out onto the track.

It is only a Mk1

Looks good, Matt. How does it effect bonnet opening?

I think version 2 needs to be wider.You really want to block off the air hitting the front face of the wheels/tyres. That air travelling up and over into the wheel arch is slowed by the tyre rotating towards it, raising the presure and gives lift (sorry not trying to teach you to suck eggs but for others benefit).

The little corner splitters I fitted were to do that and had a huge effect; I'm considering fitting air dams in front of the rear tyres where the sill wraps under.

Good thoughts Adi,

The effect on bonnet opening is shown below.



With no interference at the front (I can slide a bit of paper through the gap with nothing touching), the front of the splitter can be moved up or down as I used a couple of 'rose' joints on the upper struts.




But to get all this to work I had to change the pivot on the bonnet, as previously described. I copied Rob's design which was simple and effective.

Here is a little picture of the mechanism, nothing too complicated, and good practice for my dodgy welding skills. The square section is the bonnet hinge mechanism, the round tube with the rose joint screwed into the top (hidden by inlet pipe) is the splitter support.



Regarding the width, I am sure you are correct. I'd like to say that I CFD modelled it and retaining the lift from the edges of the tyre was calculated to give the right amount of balance between front and rear. Unfortunately (and as mentioned earlier) it was based on the selection of a 4ft sheet of ply! I didn't think about the effect of the wheel rotation at all. If maximum downforce was the target then I guess longer, wider and lower would all help, but I'm already concerned about its "max poweriness".

I didn't want to spend too much time on Mk1, as I wasn't 100% sure it wouldn't get wiped off on the first speed hump or have some other 'interesting' design problem. Replacing the actual sheet is very easy (sheet + jigsaw + drill + 1hour), although the asymmetry of the bonnet and vertical sections are messier (glue and hence waiting time, although bolt on CF might be a nice solution).

My next project will be a rear diffuser before I get back to the front again, although I have just realised that there is a "proper job" due in August, have you got any content?

Matt

The key point is where you've located the pivot as we discussed Matt , plus of course needing to cut out some fibreglass underneath to allow it to open upright ----- the hinge design itself is then not so important and simply has to work around whatever your own car has mounted up front . Looks a good job and such a boon when working on the car
My own opens totally upright without the need of a support rod ---- well , unless it's windy

"... just realised that there is a "proper job" due in August, have you got any content?..."

When's the deadline? I'll try and find time to do something about this years trip but don't rely on it too much.

Must admit to having bonnet pivot envy....need to look at mine again.