Normal service resumed

I’m still working on the car with an eye to the next race, at Brands, and the upcoming rolling road visit.

I’ve added a small stay to the airbox. At snetterton a scrutineer leaned on the airbox and the throttle bodies came adrift from the rubbers that attach them to the cylinder head. This stay should stop this happening. I am, though, probably going to move the bottom end of so that it attaches to the engine mounting, rather than the top of the pedal box.

One thing that’s been annoying me for ages is that the Coke bottle catch tank always got all distorted due to the heat. So, I bought an aluminium one from Rally Design and fitted it, as seen here. The only problem with this is that the see-through tube that allows you to see if there’s any quantity of gunk in the tank is round the far side of the tank. It’ll probably be easier to stick some sort of dipstick in the tank.

I’ve been fiddling around with all sorts of things on the car and I noticed that there was a very small leak of oil coming from the bottom of the clutch cover. This is probably because one of the things that we, fruitlessly, changed at Snetterton was the crank position sensor which is mounted on the inside of this cover. Mind you, I was pretty sure at the time that it wouldn’t help, I should perhaps have thought about it all rather harder.

It seemed sensible to take the cover off again and replace the sealant. (It doesn’t use a gasket.) This is what’s behind the cover when you take it off. It’s interesting to note how much bigger the clutch basket is than the one on the 919 engine. You can also see the starter idler gears behind the clutch and also the little teeth on the crankshaft off which the crankshaft position sensor triggers.

Here it is back again. You can see the blue sealant that’s leaked out slightly.

With that I think I’ve done the engine stuff, at least after I’ve moved the airbox stay and I’ve found another problem as a result of the next track visit.

Next thing was to look at the towing eye. Although it worked fine, the experience of being towed back after pulling off the track at Snetterton was that the ring on the front of the towing gadget was bent. In fact, it made lifting the bonnet a bit tricky. As a result I decided to replace the solid towing eye with a strap, the like of which is becoming popular on account of the ever-increasing diameter that the MSA requires them to be.

I ground off the current rod and welded a new length of tubing back onto the chassis. The towing strap that I bought, that rather iridescently red thing, just bolts into the front of this tubing although I’m thinking that I might weld it on.

One of the recent problems has been that the corner weight gauges that I, and a bunch of other locals like Adrian, use are broken. One of the pads has taken to reading negatively and it seems to be a problem in the bowels of the load cell itself. This is inconvenient but the scales themselves are inconvenient because you need to set things up with a lot of wires and ramps and so on. It’s nice to be accurate but there’s a bit of a disincentive to try things as it takes such a time to set them up.

So, I did something I’ve been thinking about for a while and bought one of these things. This essentially allows you to measure the weight of the car corners individually. It does need calibrating (at the moment it essentially reads in bar, or psi, which are unconventional units of weight). If nothing else, though, it’ll allow comparisons of weight to be made which is real thing about setting the corner weights.

Mind you, it’s yet more crap to pile into the motorhome before each circuit outing…

Another bit of suspension setup that I’ve been meaning to check for a long time is bump steer. In the past I’ve measured this by putting a straight edge on the floor and squinting. However, that doesn’t seem that accurate. So, I made this contraption here following the advice given by the estimable Staniforth and Puhn.

With that I spent a happy hour or two jacking the suspension up and down and writing down dial gauge readings.

The resultant graph of toe change as the suspension went from full droop (left) to full bump is shown as the “initial” line on this graph which shows millimetres or toe change.

This shows about 2mm of toe change, on a single wheel, throughout it’s movement. As that amounts to 4mm for the whole axle (assuming the other wheel is the same) that sounds worthy of attention. Interesting to note the shape of the graph which appears to be a combination of two curves. I did wonder if this was because of the change in instant centre position. I worked out a while ago that the instant centre moved from one side of the wheel to the other as it moved throughout its full range.

The first step in trying to address this was to insert a small washer under the left hand rack mounting. That produced the other line shown on the graph which is quite a large change. What’s more, in the direction expected from musing about it and staring at the ceiling. I’ll try some more tweaking next, and look at the other side, to see if this pattern is  repeated. It does sound, though, as if the suspension changes I discussed a while ago would appear to make sense.

And, a while later…

Hmm, ok, I found the problem in that a bit of the gauge was binding. Hence, I’ve not measured the bump steer and ended up doing a bunch of small modifications. The graphs on the right should tell the story. (Note that I put a bit of trig into  the calculations and the vertical axis here is the toe angle, in degrees. Note that the left hand wheel isn’t too good, but the right hand one seems to have come out about right. Whether, of course, this leaves me driving in a calm, collected, Jenson Button-ish style remains to be seen.