Pedal design

I've said from day one that I want to use as much of the donor as possible. The pedals were one place I wanted to keep the MX5 ones. Partly because it makes all the linkages easy to put together, but partly because I've seen multiple posts where the Haynes pedal box design has failed (or has been seriously compromised). That seems to be a bad thing in my book, considering the middle pedal is the one I rely on to avoid possible bumps.

So, I've done a quick drawing, and I can see that the pedals are too long. No matter, I already knew that. A bit of trimming, that's all. But then I realised a small design flaw. I've done my absolute utmost to have the steering wheel dead centre and absolutely square on (memories of my old Nova with wonky steering has made me completely over the top with it!). But it means I can't have both the steering wheel and the brake pedal in the middle, and measurements show that if the brake pedal isn't in the middle, I can't actually get my feet on the pedals!

This is based on the pedal hanging from above, which is the original MX5 layout. It occurred to me that the pedals themselves don't care which way is up, so I turned them round. If I do that though, I've got to shorten the gas pedal, which means I couldn't actually open the throttle fully.

Then I found a few drawings where the clutch and brake pedal are floor mounted, and the gas pedal is top mounted. And that looks like the solution. The brake and clutch do need to be cut down, but I can do that.

This drawing shows the original pedals (being too long), and the pedal layout once they've been cut down;

Note the gas pedal isn't being altered. I like the angle of the pedal, and the pivot point works well with the steering column (blue). Cutting down the brake pedal is straightforward, its slightly less leverage for my foot but the pushrod is the same distance from the pivot point which should maintain the MX5 brake 'feel'. However I might drill a second hole a bit further up to give an element of adjustment.

The clutch pedal changes shape as it's cut down, instead of the angled piece (designed to avoid the MX5 transmission tunnel) it's just straight down to the pivot point. As with the brake pedal, I'm not changing the pushrod point, but hopefully the hydraulic clutch doesn't need as much pressure.

All this means that;

1. I retain all the pivot points (bushes, return springs, etc).
2. The pivot point for the brake pedal can be easily reinforced (as can the associated master cylinder).
3. I maintain a top mounted gas pedal (my personal preference).

By the way, the drawing on the left is my shoe (just for height and width, rather than actual representative shape!) The pedals will end up on the ball of my foot (which is the inner rectangle of my 'shoe')

I did also consider the cut down. I had thought about just cutting the bar at the best position and then welding the two halves together. To me that seems to be just asking for trouble. So I'm going to cut the pedal faces off, shorten the bars by an appropriate amount, then weld the faces back on. That keeps joints under compressive forces rather than bending forces. I'll take some photos of that process, mainly to keep Mr IVA happy.