Pedal alterations

Time for surgery on the clutch and brake pedals. The originals are designed to fit around a brake servo, hydraulic clutch and a small footwell. There are various angles on the metal that just aren't needed. They're also a fair bit too long.

First thing, chop everything up. Here's the pedals in bits;

The gas pedal will stay as it is, so that is put aside for now. I'm working off the same measurement as for the Sierra brake pedal. The Sierra clutch pedal is cable operated so is lifted off the floor, but with both clutch and brake being hydraulic here it means the hinge is at the base (hence both being the same length as the Sierra brake pedal). So both pedals will be 191 mm from the edge of the outer bush to the centre of the pedal plate. A decent cut on both to keep the profile tidy, nice and simple. I also screwed both the plates on to a piece of wood, to keep the angle correct and have them at the same length. It made it easy to measure from the bush to the wood, and to keep everything at right angles.

A bit of welding leaves me with this;

The metal used for the pedals is quite beefy, but with the welder turned up high I'm happy I got penetration. It certainly took long enough to cool down (as evidenced by a very sore thumb).

Once things were cool enough to take apart, I was left with this;

A quick boot measurement had the pedals at just right place, which is fantastic. One last trial was to replace the aluminium faces;

Unfortunately they can't stay as they are because the IVA requires a permanent non-slip surface, either rubber or skateboard tape. Tape will be cheaper.

The holes for the pushrods are in the same place as before so hopefully things should still work well. 

Tomorrow will be the brackets and holes for the master cylinders. 

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.

Steering

Now the seats are in, I can put the steering wheel where I want. The MX5 design is very similar to the Sierra one, but the MX5 column isn't adjustable. So it has to be put in the right place.

A few sitting sessions got me a good position, then excessive use of metal and clamps got it locked in place. Then it was a case of cutting up and welding the three bars that make the front mount, a couple of flat plates for bolts, and lots more welding. Which got me this;

It's a steering wheel in the right place!! However, I had to consider IVA at this point. The brackets are designed to fail in an accident. The upper bolt fixings use the MX5 column slots, so the column can deform with enough force. The lower fixing is a u clamp, again it should allow things to collapse.

The top RHS piece is the same size as the Sierra one, but the left and right pieces are very different (a couple of inches longer on both sides). It did get me a bit worried, but the set up looks like other MX5 columns so I'm happy with the outcome. And I can get my legs underneath.

Next job will be the pedal box. Since I'm going way off the beaten track and using the standard pedals, I'm expecting a lot of design issues. First issue, which box of donor parts contains the pedals?!!!

Seats

Time for a big update I think. It's been some time since I last updated this blog, and rather unsurprisingly I've not actually done that much. A big push in the last couple of weeks have got me two big chunks though.

First off, the seats. Fairly easy one this, first a couple of cross bars;

The holes have got welded in crush tubes, and they're actually quite large. It was to match the holes in the seat runners, but I think the standard bolts have a shoulder on a smaller diameter bolt. Ah well, no danger of it failing IVA due to the size of the fixing!

Seat rails are bolted in;

The ends of the rails are actually bent to fit the MX5, they do straighten out to suit a flat mounting but I had to shave a few edges off for the sliders to work.

Passenger seat base in first;

Then the drivers seat, and job done;

The seat bases are compressed on the side, but not excessively. I could leave them, or I could take the leather off, 'rearrange' the base and re-cover them. I might do that anyway as I'd not realised how tall these seats are! I think it's called a 'foamectomy'...

So now the seats are in, I can fit the steering wheel. Next post.