Right then, thought I'd best update this as it's been a while, unfortunately I've literally not touched the car since around Christmas,
So there's no real update as such, just some more waffle from me about plans and designs, but I'll fill you in anyway.
I've got a new job sorted for when I finish college in a week and a bits time. The new job's 4 days a week, and involves a 4 figure increase in monthly pay compared to my current part time job at Halfords, as well as a 1000 mile a month shorted commute, and access to lots of CNC milling machines and lathes
. This all means that there should be some progress before too long, I just need to find a unit locally and nothing will be able to stop me ;D In fact I'm rather optimistically aiming to get it to the gathering for 2012 in a very near complete state. (I don't think there's any hope of it being IVA'd and road legal that soon though
) I should be able to manage this financially, as I reckon there's about 4-5k needed to get it there, but it's just a case of having the time to do it. Still, working 4 day weeks means I should get at least 1 day a week in on it as long as the enthusiasm holds out.
This also means that with a lack of college work to get on with at home, I'm able to write much more detailed explanations of what I'm doing with the car, and hopefully put across why I'm doing what I'm doing, as I'm hoping this thought that's going into it is what's going to make the difference between a pretty show car, and usable, reliable, fast, fun, drivers car.
Anyway, although there's been no change in the car in real life, the plans have moved on somewhat. The front subframe's pretty much designed, including most importantly the front suspension geometry. I'm determined that this thing's going to go round corners at least reasonably, so I've been putting a fair bit of thought into this. I've decided to ditch the standard mini subframe I'm using at the moment, as well as the bulkhead, this'll gain me some leg room, as well as letting me improve the front suspension geometry. It also means that no part of the bodywork will be structural, meaning that any future body mods after the IVA won't need another IVA
.
Angles wise I've settled on 7 deg castor and a 12 degree king pin inclination. These are both fairly steep, but the 12deg KPI is necessary to keep the scrub radius down on low offset wheels (there's still a noticeable scrub radius), and I think the car's going to be naturally a bit light and twitchy up front, so I don't see a high castor angle as an issue. This has all been designed around 2.5 degrees of static camber.
The next consideration is the wishbone length's and mounting points. I'm planning to use Mk2 Golf GTI hubs as the uprights, with the strut mount cut off and the top of them drilled and tapped to allow a rose joint to be bolted to the top of them to form the top ball joint. So that's my outer mounting points sorted, or at least narrowed down.
Now the focus becomes camber gain and roll centres. These are dictated by how unequal the wishbone lengths are, and how far off parallel they are.
The idea of camber gain is pretty straightforward, as the cars body rolls in cornering, you want the wheels to stay square to the road surface to keep a decent, evenly loaded contact patch.
Roll centres are a little trickier, but not too complex. This is basically the point which the cars body rotates around when the body rolls. On a double wishbone suspension set up like I'll be using, it's dictated by the suspensions 'instantaneous centre' - The point at which a line drawn through each wishbone meets. If you draw a line from this point, to the centre of the tyres contact patch, then repeat for the other side of the car, the roll centre is the crossing point of these last lines. Sounds complicated, but a drawing it clears things up a lot, do this for both sides and the roll centre's where the red lines cross:
The aim is to keep this as static as possible during body roll.
It's height is also a consideration; the distance between this roll centre and the vehicles centre of gravity is what causes body roll. Now body roll's not necessarily a bad thing, and it's generally thought that the best location for the roll centre is a few inch's off the road surface. The other thing you can do is use different heights front and rear to alter weight transfer during roll.
This is where it starts getting a little harder to understand, but bear with me. Reducing the distance between both roll centres and the centre of gravity will reduce roll, but
not lateral weight transfer. (So there's not much point in moving both up to reduce roll, as it won't necessarily help you go round corners). However, if you reduce this distance at just one end of the car, then you will alter the cars pitch during roll, altering the front-rear weight transfer during cornering.
Due to this I've settled on my suspension design aiming for as static as is practical roll centres, with the front one an inch or 2 from the road surface, and the rear one an inch or 2 higher than the front one. This should create some forward load transfer during roll, helping deal with the inevitably rear heavy lay-out of the car.
These are the designs I've settled on (top picture showing it level, with the bottom picture showing in under pretty extreme body-roll:
Front:
Rear:
As you can see, the roll centres stay pretty central and stationary, and the outside wheels camber changes to keep it pretty much at 90deg to the road surface. Good times
This has led me on to draw up this front subframe design. (There's still a bit of bracing to add, as well as needing to add some coilover mounts):
The other thing I've done is just to check that a decent driving position's going to be achievable
To check this out I drew this little chap, he'd more or less the same size and proportions as me, and he likes his new car
:
Anyway, once you stick him in the drivers seat it reveals that all's good, and he's got plenty of space
OK, headroom's not great, but I do have a long torso for my height, and there's a good few inch's of space to lye the seat back more than it is at the moment:
So that brings us up to date, and now I have to leave for work. Any questions regarding any of this fire away, any criticism (of the constructive kind) is as always more than welcome.
So there's no real update as such, just some more waffle from me about plans and designs, but I'll fill you in anyway. 
. This all means that there should be some progress before too long, I just need to find a unit locally and nothing will be able to stop me ;D In fact I'm rather optimistically aiming to get it to the gathering for 2012 in a very near complete state. (I don't think there's any hope of it being IVA'd and road legal that soon though 
) I should be able to manage this financially, as I reckon there's about 4-5k needed to get it there, but it's just a case of having the time to do it. Still, working 4 day weeks means I should get at least 1 day a week in on it as long as the enthusiasm holds out.
.
OK, headroom's not great, but I do have a long torso for my height, and there's a good few inch's of space to lye the seat back more than it is at the moment:
