DohNut Posted January 29, 2003 Share Posted January 29, 2003 Looking at the brake disk thermal immage - apart from the obvious differences in spot temps and average temps, on both disks the center is massivly cooler than the edges. This does give an indication to volume of heat soak into the hub. -although disc velocity will be greater at the outer edge of the pad. Then thinking of the comparison between one solid disk with integral cast iron mounting identical disk but with an alloy bell identical disk supported on an alloy spider (motorcycle style) The motorcycle disks are supported indirectly on the spider (also allowing for differing thermal expansion) I am guessing that this method provides the smallest heat soak. The all solid disk next and the alloy spider (with full circumference mounting) giving the most heat soak (I am assuming that alloy has a significantly higher thermal conductivity). From the pictures of Knackered brakes at the front of all Haynes manuals I recall that the cracked disks through excess heat cracked radially (as opposed to round the circumference) This would tie in with the hotter outside of the disk expanding more than the cooler inside of the disk. So is it best to encourage heat soak to the hub with a full contact alloy bell and hope the differences in thermal expansion is not a problem or "insulate" the disk from the hub with a spot mounting alloy spider. *confused* Nick Link to comment Share on other sites More sharing options...
Rob Walker Posted January 29, 2003 Share Posted January 29, 2003 For those interested the Pagid RS14 pads have a working range 400 to 700C and have a friction level of .45 when cold rising to .50 at 100C and on to .55 up to 700C. If you compare this with the well known and used Mintex 1144 this has .45 at cold but this falls away as the temp rises above 400C and the pad wear rate increases significantly above 300C. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted January 29, 2003 Share Posted January 29, 2003 Certain knowledgable brake suppliers have commented that the Mintex mu values are optimistic... or he might just have been trying to sell me Pagids Link to comment Share on other sites More sharing options...
AMMO Posted January 29, 2003 Share Posted January 29, 2003 There seems to be a reluctance to experiment and always go for the tried and tested route. Nothing wrong with that. But stop and think a minute. When you change a brake pad make or compound, tyres or go to a more powerful engine, are you not experimenting? So what is the difference in changing a dics or caliper to see what happens? If you have made a made a change it would be foolish to give the vehicle maximum stick into a corner with no run-off first time out. I have been around braking systems for a long time. I used to work for the Brembo importers in the early 80's. I have seen how brakes have evolved over the years and tend to know what works and what doesn't. In 1985 I went to Le Mans for the first time for the motorcycle 24 hour endurance races. I witnessed a fatal crash which was due to a brake failure. The year after I was working for a team and made up all the hoses and pip pin arrangements for quick releasing the calipers and pads. Needless to say I paid a lot of attention to what I was doing. I could tell of a load of brake failures I have witnessed over the years. Some have resulted in fixable injuries but in worse cases paralysis or death. I know a lot of dead people and I am sure I have been very deeply traumatised by their demise. I remember all the young men's faces and think about them often. I remember all their anniversaries. Motorcycles are less forgiving than cars so you have to pay 110% attention all the time. I find it a bit upsetting that Peter should say if you try the Ammo method that you should pray you don't have a major failure. I'm sure that he was only trying to make a point. I have to point out that the Ammo method of systematic trial and error has served Ammo and the people Ammo has looked after over the years very well indeed (touch wood). I am lucky that I have never done anything that has injured anybody and I don't want to start now. Maybe my luck is due to the fact that I am over-cautious. As far as I know I haven't advised anyone to do anything that would endanger their lives. It is only common sense that if you fit something to your vehicle that if you can't make it work that you should take it off and bin it. Even the AP factory approved brakes if not properly setup or looked after have the potential to kill you. Lets be careful and live long to enjoy our common passion. AMMO Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted January 29, 2003 Share Posted January 29, 2003 Lots of maths is fine but unless it resolves the issue of the ideal disk mass/ thickness for our application or a range of ideals for given applications are we not just chasing our tails. What is the optimum for a 7 after taking in all that has been said? Did Caterham do this maths when they chose the AP vented Disk or was it just a handy size See My Zetec Power 7 Here Link to comment Share on other sites More sharing options...
scooby dooby doo Posted January 30, 2003 Share Posted January 30, 2003 >Glad you took the robust argument so well. Lets move on. i was happy - i wasn't sure if you p***ed off or just being robust >The heat *is* entering at the surface and through a mechanism of temperature gradients it is heating the bulk >of the disc. how deep though 🤔 >Still don't reckon there is excessive thickness to remove. This is where we need the calcs to get an idea then we can experiment around that point. >Still reckon the smartest move for weight reduction is use of an exotic material. >Lotus seemed to think the approach had merit. cost is (is it?) a problem surely? Lotus stopped selling them after a while - why 🤔 (honest question - not rhetorical..) Ferrari worked VERY hard to get the F50 brakes to work ok from cold to hot consistantly - its not an easy task. I'm STRONGLY in the AMMO camp but would like the maths in place to get a rough idea of a starting point. Offical Caterham development can be a bit hit and miss. i don't trust them enough to believe that they didn't just ask AP for the biggest most expensive setup to fit in a 13" wheel... HOOPY 500 kg R706KGU Link to comment Share on other sites More sharing options...
scooby dooby doo Posted January 30, 2003 Share Posted January 30, 2003 forgot to comment on the picture. its VERY variable isn't it 🤔 suggests to me conduction is VERY poor and the heat doesn't penetrate very far DURING THE FEW SECS OF BRAKE APPLICATION. so i still sit on the thinner disk side of the fence OTOH the MMC disk looks to be behaving VERY nicely.... cost 🤔 HOOPY 500 kg R706KGU Link to comment Share on other sites More sharing options...
Lee Mabee Posted January 31, 2003 Share Posted January 31, 2003 Have to again let my ignorance hang out ........when you use a single (drilled) solid rotor is there a source for the "hat" to connect to the hub and how do you allow for the offset........then how does one get the correct radius (caliper)..positioning..?? Currently have the "big-brake" option and desire to seriously reduce the unsprung wt...would like to use 10" drilled rotors.......and smaller lighter alloy calipers.....thank you..........Lee Link to comment Share on other sites More sharing options...
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