My build - MX5 Donor

[Airhead]

Having got the diff mounted up and the engine sitting in the correct alignment it has become apparent that I have made my first real mistake as the gearstick now sits about 2" lower than I originally thought. Also the engine mounts that I chose are no way man enough and I predict problems there, the fix will be posted shortly and it doesn't affect the work done to date as the plates stay in the same position it just means a bit more fabrication. Anyway back to the tunnel mods.

I was never really happy with the roadster tranny tunnel as it is quite high, I measured up on my friends locost made to the old book dims and it appears that his is about 50mm lower. To this end I have cut a section off the base of each upright and remaounted it - the dimension from the top of the lower railto the top of the metalwork is now 220mm which fits the MX5 gearbox more snugly and gives the ocupants of the car a little less claustaphobic existence...


The tunnel as originally planned.

And modified:

[CTWV50]

This might be a stupid question but are you going to keep the PPF frame or does the roadster chassis act as an effective PPF (Power Plant Frame)? Oh and does the propshaft need to be shortened?

[Airhead]

Not a stupid question at all. I have opted to not keep the PPF as I am using a rigid bracket on the nose of the diff and the rear of the gearbox and yes the propshaft will need to be shortened by a fair bit.

[Airhead]

OK, onto the next problem. Actaually before we do a small comment maybe verging on a disclaimer; I am following other peoples thinking here, collating information I have found in a variety of sources. I am NOT an automotive designer and cannot offer any opinion to the validity of what I am doing here. My car is for road use, not racing, not track days etc so please - if you are an automotive designer don't be offended by my lack of knowlwdge.

The MX5 steering rack is way too long, about 140mm or so. I qualify that statement by applying some basic steering setup instruction that I read somewhere once that is that goes along these lines:

The length of the steering rack is determined by the distance between a line drawn from center to center on the inner mounting point of the swing arms. A good way of seeing this is simply to put a rubber band between the holes on the brackets which quickly makes a visual reference - thanks to Keith Tanner for that little gem.

It follows that as the MX5 conversion front frame is the same as the Chris Gibbs offering the Escort MK2 rack is the perfect item for this. In order to make the MX5 rack fit the 140 odd mm need to be cut out of the cylinder and bore - the center section of the rack. If you trust yourself to do this then go ahead but there is no way I would mess with the steering rack internals like that esp. when the escort offering is perfectly good and readily available.

[CTWV50]

Originally Posted by Airhead

Not a stupid question at all. I have opted to not keep the PPF as I am using a rigid bracket on the nose of the diff and the rear of the gearbox and yes the propshaft will need to be shortened by a fair bit.

Hmm interesting, I'll look forward to see how you do this.

[Airhead]

If you PM me an email address I'll send you some pictures etc.