Pre Season Testing At Snetterton and it's broken again

So with the car together, well in advance of the season for once it looked like I was going to make the first race of the season.  I even had time for some pre season testing at Snetterton In Late February

I took along Dave Turner who is a pretty damn good chassis dynamicist (his blog is at http://dynamicist.blogspot.com/)  to help me setup the car.

Dave was determined to help me sort out my handling problems with the car... indeed I span at 20 MPH in the Russell Chicane on the day's warm up lap :-( .  We ran a couple of damper cycles... This is basically a process where I go out and do a couple of laps with the dampers turned off... and then come in and tell him how the car felt... we'd add two clicks front or back and then go out again and report any changes.  After a couple of seasons my arse is now calibrated well enough to be able to correctly report what was happening in the car and Dave used his not inconsiderable expertise to interpret this into suspension changes.

Well when I say "We" I mean Duncan and Dave did the adjusting I just sat in the car and then went out and did two more laps.... Repeat process until car feels good... then when

 it starts to go off again  back off the last two clicks.....

I felt somewhat like a proper race driver, come in ... report to engineer.. pit crew swarm on car... retest & adjust appropriately Its a great way to setup a car and worked like a charm... the thing is now just so chuckable.  Thanks Dave :-)  

The front rear balance is now as near perfect as I think I'm going to get without investing in some new dampers.

As a result I was now leaning quite heavily on the car... but still the absolute performance wasn't there and power delivery was a bit crap.  it was juddering all over the place in the midrange and this was shaking the whole car and ruining the balance.  I was doing 1:29-1:31 which is 10-12 seconds off pole and last on the grid by a full 3 seconds.  By contrast a mate, in a car with notionally less power that he had never driven before went 5 seconds a lap quicker.  All pretty disheartening stuff really as I felt I was being brave enough and getting the lines and driving pretty well... Not Banzai  but it felt way better than 1:30s. 

The acceleration traces on my 

data logger looked "lazy"...especiallyy in the higher gears... so we wondered if the diff ratio was too tall for the new motor... se set about swapping the drive cogs around over lunch.

Unfortunately we think we got the adjusting shims mis aligned and three laps into the afternoon session this happened

Basically we think the rear sprocket was misaligned and the chain jumped and then started machining everything in touching distance.  This happened when I was flat just after the Richies apex ... I thought I'd blown the engine judging by all the rattling

So I was then faced with rebuilding the drive train in two weeks flat to get ready for the first race of the Season at Snett.ARSE!

So What's been going on this winter?

After some gentle reminding, and indeed some firm poking with a sharp stick from various readers of this blog I thought I'd do an update and answer the question "What has been going on?".  Indeed even Tim has been poked on his Blog to get me to update mine ... perhaps some people do pay attention after all :-)

So here's a fairly hefty update that will cover (at least in some degree) what has been going on for the last 8 months.

I seem to have spent most of the winter working at the back of the car.  Basically the new diff arrangement has taken a fair bit of time and energy to get right.  But it is finished now.

A rough sequence of activities is:

1. I tried and tried to use the new starter motor that I had left over from the White Van as the motive power for the reverse system.  Unfortunately the motor span in the opposite direction to that required and didn't have enough clearance around the main drive pinion to give me enough adjustment for when the diff moved as the chain tension was adjusted.
2. I then spent a large amount of time drawing up and making  a split sprocket adapter... this worked fine until I weighed it.  nearly 5Kg of additional rotating mass was just too much to carry. So I dumped that idea.
3. Duncan and I spent a long time staring at the arrangement and have now come up with a setup which is just as simple as it can get.   Two bearings a quaffe diff in between and a chain sprocket bolted to that. In fact this is quite an old photo as I now have some new lightened sprockets with lots of holes in them to further reduce the rotating mass.  The chain is tensioned by using aluminum shims between the uprights and the bearing carriers.
4. Reverse is enacted by the winch motor being pulled up into the chain by a tension cable... this is pretty chattery and now is sporting a block of beech above the chain to stop the chin and winch sprocket from bouncing apart. I think I may need to make the actuation a bit more positive b some sort of Cam action in the future.
5. The other major thing we did before the season was to tidy up the bodywork around the roll cage and throw some lovely metallic British Racing Green  paint at the beast.  At the moment only the side pods are done so the car is an interesting two tone red/green.  In fact its been likened to an old Ford Cortina with each wing a different colour.  But hey at least it is distinctive!