Radical SR8

Would you feel the difference in the lighter wheels?

 

I would think it would be the best place on the car to loose weight. Its unsprung weight which the books tell you is critical as the mass is in motion, moving up and down with suspension movement, and spinning backwards and forewards with brake amd acceleration. Dont know if this will be detectable by feel....yet...

 

Yea that's what I meant, the clock would show it, but curious as to if you would notice it.

 

Theres a chap in South America who makes ali uprights for radicals which are a bit lighter then the fabricated steel items fitted as std - so these might be worth a go at some point. Also carbon brakes are available but not allowed in sprinting.

 

Update time: not a lot being happening tbh. Have rebuilt the billet wheels and get them working now on the front with adequate brake clearance. So they are ready for a new set of supersoft Avons maybe for the season finale.

Going to drop the floor off for a check about and take LHS sidepod off to investigate moving to Lithium batteries.

Have started a discussion with Simpsons to maybe make some better exhaust manifolds which would match up with a set of stage 2 billet cams. It would probably be wise to put a set of arrow rods in too if raising the rev limit. Dont especially want more low down torque, but a bit more top end would be useful.

 

good job i checked the car....alternator bracket cracked in two.....apparently a known issue.......damn race cars

 

Ally or steel?

 

cast ali

got a photo if only i could host it these days

radical say the failures are known but not common. others say its well known and even billet mounts exist before they were stopped being made due to cost. radical parts say they have never made billet mounts. go figure.

 

If you're a paid member you can upload directly to forum makes life easier for less than 3p a day

Loving the blow by blow hassles and fun of an ultimate sprint car

 

Twin lithium batteries now fitted in place of the old Red Top 30s. Weight saving 18kg. Fitted two , in parallel so still 12V, as was easy to use the existing Radical battery boxes and wiring. Also added a 175A easy to get to Anderson plug to plug in one of old Red Tops when warming engine up first thing of race day.

Batteries used are twin YTX14s from Allen MacDonald http://www.aandgmotorcycles.co.uk/batteries.html

Allen is a long time British Hillclimb competitor these days in a sports libre Mini Evo (mitsubishi evo derived).

Job done apart from battery securing straps waiting to arrive....from a Vespa

Treated myself to a new charger from Allen also that has lithium charging program. My ctek one was probably ok as it was voltage limited and didnt do desulfation modes so likely ok for lithium, but for 35 cannot be too careful with these things.

http://www.aandgmotorcycles.co.uk/charger.html

I reckon that takes us under 700kg....time to get the scales out!

 

18kg isn't to be sniffed at!

 

I looked at lithium for the MK5 but it also meant i needed a new charger so it wasnt worth the weight saving. You just have to keep on top of them and try not to crank the engine over for too long.

 

So, after removing double seat plus associated passenger bits and bobs, battery replacement, new wheels, bits of wiring and a few odds and ends, we have gone from 723kg (water and oil but no fuel and no driver) to 677kg. Saving 46kg.....

Thats gotta be worth doing.

Starting to get hard to see where more can be saved now without re-manufacturing parts from lighter materials or compromising functionality / safety capacity.

 

That's some saving!

 

it is. well pleased. it gets tough from here on though....the whole chassis is panelled in steel sheets over steel tube. I see no reason why a lot of it couldnt be ali but thats a 'back to chassis' job. The front splitter and rear diffuser might have 10kg saved if rethought in exotic materials. The rear wing support could be ali. Maybe, just maybe, a 650kg fully big track useable SR8 is doable....

 

Had to miss Aintree sprint due to leaking radiator. Got the car ready before going on holidays, warmed it up, checked all levels etc and everything seemed fine. Tues before the sprint went in garage and for some reason looked under car, think I dropped something on floor, but anyhow there was a big pool of water underneath. Crap. Busy at work after being on hols so worked late and got the rad out which really needs whole sidepod taking off on SR8. Pressure tested it in bath of water and there was 2 holes apparent, one looked like a stone hole and the other was a small area where the fine cross tubes enter the end tank, looked like the braze or whatever they use had given up as it was fizzing fine bubbles round the tube/end tank join. So I called a couple places and there was no way it was going to get repaired and back together by Sat am.....gutted.....so reluctantly withdrew from Aintree event and concentrated on getting it sorted for next outing.

So it turns out its quite hard to repair aluminium rads. The tubes are so thin they are hard to weld and the end tanks are fused to the cross tubes in some automated oven process. Spoke to Applied Radiators in Hanley and they said they would take a look and give it a go. Well not only have they fixed both leaks but the rad looks brand new! fixed with some special epoxy resin and baked in an oven. Pressure tested and all ok, good to go. Great service, and open Sat am!



800 for a new one from Radical but you could get one made for less than half that, but that takes time, 3-4 weeks lead time from the couple places I called.

Car back together today

 

Brand new slicks, ready for the race meet! I assume you run new tyres for every race?

 

New slicks for season finale, British Sprint Champs round at Anglesey. They have to last a year as they are 1400 a set.....these are properly newly made and came straight from Avon. Only to be used if conditions are favourable else will run last set, or probably wets given its entering autumn and its Anglesey LOL

 

Those set of tyres are as expensive as a year worth of karting slicks. I run brand new regulation slicks for every race at ~ 140 quid a per set.

 

At 140 a set I would run new ones for each race too lol, but those Avons are expensive and there is nothing else that's the right size and as soft - Michelin S5 is a cracking compound but they don't do the size, and they are just as dear, Hankook do the size but the slicks aren't soft enough, and Dunlop are expensive AND too hard.

So Avon have the hillclimb/sprint market sown up and can charge what they like and if you don't have them you might as well not turn up.

Hankooks by comparison are 700 a set.....

Dunlop were experimenting with a nice soft compound called HC100 but that's disappeared. That would have been ace for sprinting as it was made for longer hillclimbs.

So I try and make them last a year - the fronts get some proper hammer on the wear front as they are quite narrow at 205 section, and the backs get torn up with stones as the compound is so soft.

Avon A15 compound will just about last 120 secs on my car before it overheats - on a double lap at Anglesey the front grip disappears in the last hairpin - but that's the trade off for having good instant grip in the early corners. I keep meaning to try A53 which is one step harder on the front, especially on a hot day, but I doubt it would give the confidence in the early corners. I've used A53 for 20 min sessions on trackdays so its got much more heat capability than A15, and as circuit racers use it, its a lot cheaper.