Radical SR8

Yes I am. I always thought I wanted to move from tintops to single seaters, but I fit much better in a sportscar. i'd still like a single seater at some point if i can find the right one. its a right mither to get ready for action, trailoring etc, but just unreal when you hit the sweet spot.

 

What sort of single seat you fancy ? Formula fords probably a bit tame for you now . My mates setting up a two car team for the northwest formula ford championship. He's trying to get it going for the coming season but not got the cars yet but he knows loads of people and once he gets going he'll be ok . I can't belive how a paying driver has to pay 40,000 for a seasons racing

 

not formula ford. something more like formula renaut 3.5. quite fancy a formula palmer audi but never see any for sale. would love to put a badger-5 20vt in one of those

 

That's what I thought you'd say . I'm sure Mrs T likes the Radical though .

 

For Sparrow: a solution for dry-break systems that means you dont have to cart around a big dump churn - funnel is Sealey F99240, about 8-10.

Silicone coupler came with my dump churn and is a petrol-resistant one - basically this funnel is a direct swap for the big churn.

 

Drained the fuel tank and weighed what came out. 60L went in so 36.5L used at Oulton. Wet in the morning so not much max throttle but probably 15 laps worth giving it some stick in the afternoon. So Radical estimate of about 0.75L/min pretty accurate.

 

So the car felt great at Oulton, good balance, not too snappy, great grip in pretty slimy conditions, but I was getting puffs of smoke off the front wheels in two braking zones and at the time I thought it was me locking the brakes. Anyhow, turns out that the front tyres were touching the underside of the arches:



So several options to stop this

1. Run narrower front tyres - not an option as they are not available in the right construction/compound
2. Increase ground clearance - not attractive as the aero will suffer and the body isnt actually hitting the ground (much)
3. Run more -ve camber to tuck the tyre inside the arch - not that attractive as tyre was working well, but maybe a little more could be added
4. Increase the spring rates....checked what is on the car with Radical and they say its on the soft-side of normal.

So plan is to increase spring rates front and rear to keep the same balance as is on the car now, and maybe add a sniff more -ve camber. And have all the damper characteristics recorded at the same time while they are off.

Nice dampers: (Intrax titanium bodied 3 ways (high/low speed compression, rebound) - and only 10mins to remove from car!!!

 

Rear dampers off so now all four can go to my damper man for measurement of current settings, and then upping of spring rates front and rear to stop the front tyres rubbing the arches on braking.

Rear dampers - 3 way titanium Intrax like the fronts



Good opportunity while the dampers are off to finally work out how the patented Radical Nik Link suspension works. Finally got my head round it - its very cleaver....



The bottom of the damper is fastened to the bottom wishbone, but instead of fastening the top of the damper to the chassis, its fastened to a bellcrank (Pic). Now there is also a solid link fastened to the lower wishbone that also goes to the bellcrank - this means that when the wishbone moves, the damper gets compressed from both ends....double the damper movement for a given wheel movement. WHY? well I think its because its easier to accurately damp suspension movement if the damper piston moves a greater distance. This achieves that when there might only be a very small wheel movement. So you dont need F1-spec dampers. Maybe.

So this happens on both sides of the car. Also fastened to both bellcranks is the ARB - a bar with a kink in it. Pic here (arb runs across the back of car under the exhaust):



So with this arrangement, if both wheels compress at same time, the bar just moves laterally across the car.

If however only one wheel moves, like in lean with a limited droop setup, the bar gets bent or straightened. Thats the anti-roll resistance. Different resistance with different thicknesses of bars.

Its all a bit odd and I still cannot understand why they have not used a regular torsion ARB, could be that it all works quite neatly with the damper movement amplification aim.

The ARBs are known to snap at the bend illustrating the forces involved:



http://www.pistonheads.com/gassing/topic.asp?h=2&t=771451&mid=0&nmt=+NIK+LINK+FAILURE

Splitter has gone to fibreglass shop for refurb, so soon we will be assembling again ready for next day out

Love working all this stuff out

this is good too, and thought provoking

https://sidepodcast.com/feature/tech-spec/in-a-state-of-suspense-peek-inside-f1-suspensions

 

Small update - couldnt work out how to calculate it theoretically so worked it out empirically by moving the wheel and measuring the differences between the damper mounting holes - front suspension motion ratio = 1. In the normal range of stroke, damper moves 10mm for 10mm movement in the wheel. This despite the damper attaching to the wishbone part way along, and being inclined. Smart stuff this.....the rocker arrangement makes it so.....effectively increases the damper stroke for a given wheel movement for better control.

Rear to do next.

 

I remember the 'string computers' (wood nails string) people used to use to analyse suspension
Jon

 

Rob, did you ever sort out the footage from Oulton ?

 

yep, got some from early sessions but then the camera battery ran out and i didnt realise, thought it was powered by cars electrics but seems not, seems the 12v feed is just a signal to turn on/off. got some though, just not the best stuff....typical. will go again soon though. nice data overlay on it a bit like your stuff.

 

OK - a bit of a suspension update. Car was previously running 95 N/mm front and 110 N/mm rear springs. Had determined empirically that front and rear motion ratios were equal 1.0 (a very cool bit of chassis design IMO) so these spring rates equate to 4.86Hz front and 4.15Hz rear wheel frequencies (delta 0.71Hz / 17.1%). So I need to go up on spring rates to stop the tyre fouling issue but not upset the balance. Hence have moved to 110 N/mm front and 140 N/mm rear springs. Had to go for Eibachs as the Intrax dampers take 60mm ID springs. This now equates to 5.22Hz front and 4.50Hz rear wheel frequencies (delta 0.72Hz / 16.0%). Near enough - somewhat governed by available spring weights.



So as a guide to those who might be interested, ballpark wheel frequencies for different types of cars:
comfortable road car - 60-80 CPM (1.00-1.33Hz)
sports road car 80-100 CPM (1.33-1.66Hz)
race cars without downforce 100-125 CPM (1.66-2.08Hz)
current race cars with downforce 200-350 CPM (3.33-5.83Hz)
ground effect era race cars >500 CPM (>8.33Hz)
(CPM = cycles/min - X/60=Hz)

So we are still in the right ballpark.

Dampers have been off for dyno checking so hopefully will pick them up this week. Then rebuild.

Are going to take a bit of camber off the front tyres to make them work a bit better, and also increase the front tyre spring rate - this is higher if the tyre is flat to the road compared to running lots of negative. Are also going to move to slight toe in on fronts from slight toe out - it was a bit fidgety at Oulton so will settle that down a bit and also get some better initial turn in grip.

Have made a 'string square' to set the wheel geometry using axle stands and a 4M length of aluminium scaffold pole that I happened to have lying around - its spot on for the job and heavy enough to stay put for measurements. Cut it in half and have cut some grooves into each end 1900mm apart to take the fishing line (cut carefully/slowly with a hacksaw). Fishing line is 0.32mm 40lb blue 'super power'.





Going to use the guidance laid out in the Watkins Smart Strings user guide:

http://www.smartracingproducts.com/smartstrings.html

Cheers

Rob

 

Rob, just seeing this thread now - bit behind with the whole forum thing atm. Congrats on a very nice buy - you did well indeed.

On the suspension, you are correct about the damper motion from the wheel movement point of view - far easier damp a small movement at wheel if you have a larger stroke at the damper. Also, something that is not as obvious is stiction resistance that is present between the damper piston seal and damper bore - If you have a suspension system that uses a lesser ratio, meaning the damper travels far less than wheel does then the damper/full system spends a lot of time trying to accelerate out of, or trying to over come this stiction zone at the start of the plungers direction change. In fact, the stiction zone can thus represent what should be the travel zone and compromise fine wheel movements. By upping the ratio with methods we see here, the stiction zone has less of a knock on effect on fine wheel movements as the piston spends less time in that zone.

If ever you pressed hard on a trolley jack to put it down you will notice it requires a fair push at the start compared to the pressure required to keep it moving - this is stiction also at the piston seal/bore wall interface.

I did a fair bit of stiction research when looking at the F1 pneumatic valvetrains - stiction is a major performance killer here too. A lot of internal bore coatings on the cylinder bore walls inside the valve trains share similar coatings with the damper bores on the suspensions on the same car - so it clearly is an important 'thing'
In a lot of cases the coatings are top secret, but, they 'could be' PVD chromium nitride coating, or teflon impregnated hard anodizing, and some other stuff.

Anyways, bit of a rant there but its an interesting design and topic - sadly, the patent end was a bit daft - obviously the assessor hand'nt a clue what he was looking at since this compound layout has been around for yonks - if you Google a guy called Andy Thorby (Van Diemen)you will find he was the man that came up with it originally - it was just called 'a different sort of suspension' back then though. Maybe having a catch phrase is the secret to a patent grant...

Again, best of luck Rob, would love to see it sometime perhaps,

Brian,

 

Splitter back from fibreglass shop so as it was a sunny day, gave it a quick rub down and paint - looks miles better and isn't cracked along the front seam any more. While its off, will stick some kevlar on the jabroc pads to give a bit more wear protection.





Also had a small wiring issue on the rear lights to sort, nearside indicator not working traced to broken terminal in a plug to rear bodywork, so bought some of these heat-shrink solder butt connectors to splice some wires together



[video=youtube;24FjjIVpk9U]https://www.youtube.com/watch?v=24FjjIVpk9U[/video]

Small white ones are about right for automotive wiring. Damn these are good! Heat with a hot air gun and the low temp solder joins the wires and then the heat shrink and glue rings holds it all together. Result is very strong joint in no time at all, and takes up almost no space. VERY good recent addition to my bits box.

 

Oooh, I like those connectors. Where'd you get them?

 

saw them in tweeks catologue (p295) but they are in ebay and amazon for much less

search solder butt heat shrink and you'll find them

 

I bought some years ago but never used them as there were issues with higher current applications, still have the packets of them in my box

 

these power a light bulb. should be ok.

 

Cheers.

(Tweeks Motorsport catalogue is top of the pile in the [strikethrough]Man Library[/strikethrough] downstairs loo.)