Sam's build thread

[metalhead]

Did you see the message from Geoff on the website?

[sambb]

CAMS NSW Hillclimb Championship >> NEWS: A message for all

yep. surprised his family will let him out again.

[sambb]

Some things I think I've discovered about 1 way damping adjustments on my car: When I had my thicker 22mm whiteline FARB I was running the front dampers 5/12 clicks out from full hard. The dampers had originally come with 8kg/mm front springs and a recommendation to run them 4 clicks out from full hard, but when I swapped in the 7kg/mm fronts 5 clicks seemed to do it. After going for less anti roll and going back to the stock 20mm FARB, I found that the front felt way softer than I'd anticipated and seemed to have too little rebound. So after going both ways on the 1 way damping I have ended up all the way up at only 2 clicks out from full hard to get the thing steering nicely.
I'm thinking this could be for two reasons. The stiffer front bar 'cross talked' more across both sides so that the left sides damping had an additive affect to the right sides via the bar?...….when I went to the softer bar and each front wheel became more independent, then each damper had to work a little harder? open to thoughts on that
The other thing could be that the dampers have a 3:1 ratio of rebound to bump. So as you add rebound in gross amounts a 1/3 portion of bump damping goes in with it. It could be that previously the car didn't tolerate too much rebound in the front because I already had plenty of anti roll ie the bump damping creeping up at the front wasn't needed and had an adverse affect. But by going to the softer front bar, the car was asking for a bit more rebound and the bump that came with it was welcome too because the front anti roll had been lessened ie any bump that was added in with the rebound adjustment had a positive effect.
Could all be in my head but I'm getting through my test corner now much quicker than before, with comparatively minimal protest from the tyres from my first settings, yet the big pay off is that power down traction out of corners is better with the softer bar.

[simon k]

sooo..... good thing?

and yeah, it works in my head that a thick bar has an additive effect so long as the wheels aren't hitting the same bump at the same time...

[sambb]

The change to the softer FARB? initially I thought not, but happier with it now. Remains to be seen on the track.

[Sydneykid]

Softening the swaybar (less anti roll) effectively reduces the spring rate in roll, where the lighter swaybar "transfers" less of the spring compression from the outside (loaded) wheel to the inside (unloaded) wheel. As a result I would expect it to feel as if I had fitted softer springs, but only in roll, not in other spring compression events, such as under braking for example, where it should feel the same.

You may well find that with the softer front swaybar the 8 kg springs may be more acceptable than previous (with the heavier front swaybar). Of course the LSD will change everything especially power down and then the heavier swaybar may be the better answer.

Adding bump damping is somewhat similar to adding spring, but only over a shorter timespan. Eventually it will "push" through the damping, whereas with a spring rate it's forever.

I think we have had this conversation before, shock absorbers are timing change devices, they slow things down. Add more damping and things happen slower, eventually they still happen, but it just takes longer. As a result changing damping has a different effect in a short duration corner (change of direction) when compared to a longer duration one (sweeping bend). So in shot duration corners with short time lateral G force we can substitute more bump damping for a higher spring rate. But in long duration corner with prolonged lateral G force we need a higher spring rate.

It's rather difficult to have too much rebound, of course it's possible to have so much rebound that it slows down the spring recoil such that the car eventually "jacks down". As you drive down the road it gets lower and lower until it sits on the bump stops. But like too much spring it is easier to have too much bump damping and lose traction as a result. Hence the 3 (rebound) to 1 (bump) adjustment ratio.

The spring, damping, swaybar triumvirate is a big circle, there is often more than one answer that works.


Cheers
Gary

[sambb]

So if I understand this correctly I'm imagining the Bathurst hillclimbs. On day 1 going up the Esses (rapid direction changes) I imagine that if it is the case that 7kg/mm front spings are now too a bit too soft with the stock FARB, that I could maybe compensate with the dampers by getting more bump into the front due to the car being thrown around. But doing Mountain Straight coming over the crest at Suliman Park into those long compressive G's though Reid Park or up Griffins bend are where I could be front anti roll deficient and needing either my 22mm FARB back or the 8kg/mm springs, as extra bump damping can only really find the time to have an effect in the corner entry phase - after that its back to the elastic anti roll hardware to do the job. Is that kid of it?
So of my two bodgy theories as to why the car on a stock FARB feels more balanced close to full hard on the damping settings, it seems that it could be that the extra bump is aiding corner entry by temporarily compensating for the softer front end. I guess I've got to consider also that on the track the car runs 30+kg lighter in the rear, making the rear end stiffer in relative terms which will be a whole different kettle of fish.

[Sydneykid]

In simple terms, yes, 7 kg/mm up the Esses and 8 kg/mm up Mountain Straight. Or 7 kg/mm at Wakefield and 8 kg/mm at Eastern Creek. Or when the track layout is better for the 8's use the larger front swaybar. That's why adj swaybars are so useful.

On the 30 kgs I assume that's spare wheel, tools etc in the boot?. In which case, being located low in the chassis, I doubt that it will make much difference.

My suggestion would be to wait until you have the LSD in, drive it a bit and then make the call.

Cheers
Gary

[simon k]

What scope is there for making the stock front bar adjustable? IE Will it bugger up the metal (for the stock 'soft' position) if we grind flats on it and drill holes to give it a 'hard' position? how about making a sleeve with a plate underneath that can slip over the stock bar and clamp around it?

I don't know how much true, real world impact it has, but there's also the length of the links and the angle they are against the bar changing how much leverage they have over it. The way it works in my head as far as links go is that 'soft' is where the link is at 90° to the bar and the bar is horizontal, but 'hard' is where the link is at an obtuse angle and the bar is slightly below horizontal - though that may just destroy the link balljoints

[sambb]

Simon, go back to page 33 I think, post #326 and # 324. I ran whiteline thicker whiteline drop links after running the stock ones on the whiteline front bar and noticed no difference. I then ran even shorter super pro drop links that I needed when I went to the MCA's and noticed no difference. I think you'd have to go to the system in post #326 where its just the u shaped links direct from bar to control arm to erase any give in the links and avoid the steering lock applying pre load issue. I've been thinking about going to the horse shoe shaped direct links like a mk4 Golf gti but only if I could get the bracing welded to the control arms on a hoist with the control arms in situ. In short I found drop link stiffness impossible to tell, but moving a hole position on the whiteline bar was un mistakedly different. The hole position shift on the bar makes a big difference, but on the stock bar there's not really available room for another hole hey, which is why I was thinking of going to the super short direct links and trying that out.