Have PR6... now a bunch of questions

[kartaphilos]

Picked up the PR6 yesterdays and can't wait to drive it! Before I do I have a few basic questions that I'm hoping you wise people here can help me with.

1. Gearing. Does anyone have a gearing spreadsheet for the PR6? I'm trying to figure out what gearing to run for different tracks.

2. Chain. What section chain does radical use? 525, 530? How many links will I need?

3. Centrelocks: Can these be undone with a breaker bar or will I need a rattle gun. Tried a breaker bar today but not enough friction on the wheel to hold it.

4. Pip Pins: Front bodywork has 4 of these....bloody expensive little things it turns out. Would like to have a spare or two. Is there a good source for these?

Cheers,
Matt

[SportsLibre]

kartaphilos said:

1. Gearing. Does anyone have a gearing spreadsheet for the PR6? I'm trying to figure out what gearing to run for different tracks.
Use the spreadsheet from http://www.westgarage.co.uk/calculators/calculator... and put in your chosen sprocket combination and rear wheel diameter.

2. Chain. What section chain does radical use? 525, 530? How many links will I need?
530 , it will probably be written on the side of the chain links

3. Centrelocks: Can these be undone with a breaker bar or will I need a rattle gun. Tried a breaker bar today but not enough friction on the wheel to hold it.
You will probably need someone to sit in and press the brakes to get them off, as LCM says 200 Tourques on and a lot more to get off. A rattle gun may do the job? (luckily I only have to deal with the time taken to to do 16 wheel nuts).

[LCM]

1 - use Angus' link
2 - 530. When you buy a new chain make sure to get yourself a few extra split links so you can re-make it when you change ratios. If you are doing speed events regularly then you probably want to explore drag bike chains - they have lower elasticity than GP chains, the yield point is therefore much higher but (there always has to be a but) is closer to the fail point than with GP fellas.
3 - you can try! I've broken breaker bars trying to shift them and got white finger syndrome with rattle guns! I've found that the only reliable answer to getting them off is a BIG torque wrench! By BIG I mean one from the Norbar industrial range with a suitable adapter and socket http://www.norbar.com/Industrials-TorqueWrenches-5... For what they are you may be pleasantly surprised at the price. Plus you will need a glamorous assistant stamping on the brake pedal.
4 - I only know of BIG R as a source (but they must buy them in mustn't they). Might be worth trying Nick Skidmore as he does all sorts of odd fasteners (you'll find him on Uphill Racers or PM me for his details). With my SR8 I adopt the strategy of not losing them

[splitpin]

On 3, with someone holding the brakes, we've never had a failure (or anything approaching it) releasing the C/Ls by simply using a professional quality 3/4" (I think - will check) breaker bar direct into/onto the huge wheel socket plus the handle of the quicklift slipped over to provide leverage of not far off 2m! - has worked each and everytime and firstime. Extremely cheap, stupidly simple and very effective - I like that!

All courtesy of a tip from DD, couple of years or so ago - Thanks David.

Will try and post up picture later.

HTH

[Simon T]

4. Merlin or Demon

[gaxor]

Concur with Simon, and the Demon ones have a positive lock, much better than the ones from the big R

[kartaphilos]

Thanks for the spreadsheet link. Perfect! I had found something similar but only works online - http://www.gearingcommander.com/ It does produce a nice table of speeds for different F&R sprocket combinations. I've used 570mm diameter of the rear tyre as an input. I've assumed tyre growth at speed offsets the reduction from load on the tyre? Or does the aero really squash it down a lot. I'm only using it for rough gearing choices and after I've grabbed some data from some runs I can calculate a correction if its way out.

4-bolt wheels would have been preferable over centerlocks. I've got a nice strong jack handle that I've used over my breaker bar for doing hub nuts in the past so I will break this out and have a go today.

Will get a few spare split links for the chain. LCM - Any links to drag chain info?

Gaffa tape on the pip pins it will definitely be! Might even tether them on...

[kartaphilos]

Next newbie question...

Are the Dunlop slicks unidirectional? I can't find any markings on them for rotation. Does that mean I can put them on either side? I know the Avons are directional (but not obvious, recall reading on BMTR how to figure it out)

[LCM]

kartaphilos said:

Will get a few spare split links for the chain. LCM - Any links to drag chain info?

I've always bought my chains from Mark @ http://www.powerlinks.co.uk/

Very helpful especially when I was experiencing Death by Chain Stretch in Betty's early days.....................

[LCM]

kartaphilos said:

Next newbie question...

Are the Dunlop slicks unidirectional? I can't find any markings on them for rotation. Does that mean I can put them on either side? I know the Avons are directional (but not obvious, recall reading on BMTR how to figure it out)

Don't forget that they're not really interchangeable as they require different static chassis settings to work well.

[kartaphilos]

LCM said:

Don't forget that they're not really interchangeable as they require different static chassis settings to work well.

So what sort of changes are we talking? Is it geometry, stiffness, or both. I've got a standard Radical setup on it at the moment and need to wait till I have some seat time before I start playing with it. I'm assuming a set of new A15's will be much better than used circuit slicks even without the correct setup.

I do have a full set of Nik links so I can play with roll stiffness (hard at front soft at rear is the basic idea for tighter speed events??). Should I be investing in another set of springs?

[splitpin]

I'm guessing mostly the empirical considerably greater camber for Dunlops compared to Avons, but that's one for Lindsay .........

Anyway, DR dry slicks aren't directional but obviously the latest/current pattern wets are. And although it's probably a very personal thing, once we've run the dries more than a couple of scrubbing laps, I won't simply swap them from one side to contra-rotate; in other words to change sides to balance out wear (if it makes sense for some reason), I have the tyres removed and remounted so they never contra-rotate after they've been 'load-bedded'.

[LCM]

kartaphilos said:

So what sort of changes are we talking? Is it geometry, stiffness, or both. I've got a standard Radical setup on it at the moment and need to wait till I have some seat time before I start playing with it. I'm assuming a set of new A15's will be much better than used circuit slicks even without the correct setup.

I do have a full set of Nik links so I can play with roll stiffness (hard at front soft at rear is the basic idea for tighter speed events??). Should I be investing in another set of springs?

Basic geometry!

Avons work with a LOT less camber (and most other things) than Dunlops. A15 is fabulous stuff for speed events but is so soft that if you run it on Dunlop settings you're likely to shag the tyres and so chuck £1k in the bin. Depending on ambient temp it is good for only a few k of balls out driving.

Circuit racing compounds will simply not work on speed events. If you want an Avon for track driving then speak to BMTR about A53.

If you PM me then I'll send you some suggested set up data for Avons which will give you a starting point from which to fine tune it.

[gixermark]

on the centrelocks... once you get em off.. i suggest you use some VERY light wet/dry on the mating surfaces on nuts and face in the wheel... you will probably find they are pitted.. and the actual friction is probably debris/material 'welding' themselves between the two materials

with that done.. and maintained... i found the 200ft/lb easy to get on off...

i bought a halfords professional 1/2" drive torque wrench for roughly 60quid !! MUCH cheaper than the massive ones that other guys use - and dead easy to use.. also smaller and lighter too ! :-)

[kartaphilos]

Thanks all. Have got the rear wheels changed. Can't do fronts until the right quick lift jack arrives.

Managed to try taking rear bodywork off single-handed which was easier than expected. I've been told the front is definitely a two man job.

Adjusted the seat as far back as it will go but need a little more leg room, will see if I can adjust the pedals forward a bit. figured out how to pump out the fuel via the sampler so can measure fuel usage. Almost ready to drive it now! Just need to figure out how to use the AIM datalogger

FYI 1: Looking at the setup sheet from Radical. Total weight was 547kg. This included 80kg of driver ballast (about 10kg too light) and 11L of fuel (pumped it out today). So rough half-dry weight is <460kg.... Fully wet would be around 505kg?

FYI 2: Weighed the wheels & tyre combo's I have. All Image wheels.
Front wheel + new Avon A15: 12.2kg
Rear wheel + new Avon A15: 14.6kg
Front wheel + used Dunlop slick: 11.7kg
Rear wheel + used Dunlop slick: 13.4kg

Front wheel + new Dunlop wet: ?? kg (can't get off car yet)
Rear wheel + new Dunlop wet: 13.3kg

Matt

[splitpin]

As it seems to be down your way Matt, what are you doing on 27 June 2013?

Maybe a great chance to get intimate with your car including tips - like how to get the front off solo; I can so you can; your Big R Set Up weights look to be less bodywork; they usually are.

Cheers

Trev

[kartaphilos]

splitpin said:

As it seems to be down your way Matt, what are you doing on 27 June 2013?

Maybe a great chance to get intimate with your car including tips - like how to get the front off solo; I can so you can; your Big R Set Up weights look to be less bodywork; they usually are.

Cheers

Trev

Trev, What's happening on the 27th?

Less bodywork makes sense. How much does the bodywork with carbon wing weigh?

[splitpin]

kartaphilos said:

Trev, What's happening on the 27th?

Less bodywork makes sense. How much does the bodywork with carbon wing weigh?

Fingers crossed, ROCTD @ BHGP. Ping me your email and I'll send you the details.

Using my most trustworthy figures, the bodywork on our 2012 PR6 (all OEM including the carbon plane and flap) weighs approx 37KG.

Cheers

[mabbott]

The Radical quoted figure sounds right. We were weighed at Snett post race at 565kg car and driver combined which is just over the minimum. I was quite surprised by this as early PR6s were very light, the last ones less so.

[SportsLibre]

splitpin said:

Using my most trustworthy figures, the bodywork on our 2012 PR6 (all OEM including the carbon plane and flap) weighs approx 37KG.

Cheers

WOW, the bodywork on my 1998 clubsport weights nearly 80Kg, never weighed the sidepods but front and rear clamshell each weigh over 20Kg and the sidepods are pretty solid lumps.