AMMO Posted January 24, 2003 Share Posted January 24, 2003 Ken I am now 47 years old. Last time I was in a fight was forty years ago. I was in primary school. I was (and still am) slightly built. The other kid was called Stephen Lucas. He was smaller than me. He also beat the living daylights out of me. Since then I have never fought. Maybe I come across wrong. I love to contribute to this forum and exchange opinions with other like minded people. Opiniated yes, but never to show I am better in any way. Only to exchange ideas, have a bit of fun and sometimes discuss serious views. Maybe I should use more smilies. 😬 AMMO Link to comment Share on other sites More sharing options...
EFA Posted January 24, 2003 Share Posted January 24, 2003 Go on , punch his lights out....... Link to comment Share on other sites More sharing options...
EFA Posted January 24, 2003 Share Posted January 24, 2003 Ken, I never said mass was good, but sadly it is required to provide an element of stable surface area. A better disc, as we all know would be of a lower mass material. Now I've got a carbon disc off DH's Jordan handing on my wall............. Arnie Webb The Fat Bloke back @ 512k Link to comment Share on other sites More sharing options...
AMMO Posted January 24, 2003 Share Posted January 24, 2003 Maurizio Ital Non rompere il cazzo. 😬 Senno' ti faccio un 🙆🏻 cosi'. Ciao AMMO Link to comment Share on other sites More sharing options...
scooby dooby doo Posted January 24, 2003 Share Posted January 24, 2003 Peter, if you claim that most of the heat is stored then the brakes would get hotter EVERY stop. cars do 24 hour races without the disks melting and dribbling away. I know you know that so I'm obviously still missing part of your point *confused* *confused* Forced convection sounds like a mass flow conduction type effect. but we're just arguing terminology there. my thoughts are that things will stabilise at some temperature unless the pads (or disks as you say) get too hot and their properties change so that they don't work. The question is if we can get a setup where everything stays within its limits. I claim that green stuff and 1144 pads get too hot well before the disk is damaged. RS14s will take a lot more heat - I don't know if they'll take disk damaging temps or not. My thoughts are that pads capable of taking a lot of heat (RS14) and solid disks will be a good experiment (in the AMMO way). If the disks cook then I've lost 20 quid a side when i bin them andI can put the vented back on. IF they don't cook then I reckon that skimming them won't cause a problem. if the heat isn't conducted withing the disk then the disks thickness surely becomes irrelevant (until 5 seconds of heat can condeuct through it or it fails mechanically or due to thermal stresses). Finding out that AP calipers in an unmodded state can run non-vented disks keeps the experiment cheap. I'd like to see some experiments to see what vented disks can do in terms of losing heat compared to solid, slotted, drilled etc. HOOPY 500 kg R706KGU Link to comment Share on other sites More sharing options...
EFA Posted January 24, 2003 Share Posted January 24, 2003 Hey AMMO che cosa è wromg con questo uomo di Hoopy? Ora è d'accordo con ognuno Link to comment Share on other sites More sharing options...
AMMO Posted January 24, 2003 Share Posted January 24, 2003 Questo Hoopy non sa' che cavolo dice. Soliti pazzi Inglesi ubriachi. Certe volte e' d'accordo, certe volte non ne vuol sapere e ha solo ragione lui. Potrebbe essere una donna ? Mia moglie anche si comporta cosi'. AMMO Link to comment Share on other sites More sharing options...
Tony C Posted January 24, 2003 Share Posted January 24, 2003 Sorry if this is late, my computer had an episode. I forget who said it now, I'm laughing too hard at "Go on, punch his lights out....." Everything usually turns out to be a compromise. In this case:- A robust disc that will not be damaged functionally by the HEAT it is subjected to. Pads that will provide the maximum friction when pressed against the rotating disc. Clearance around the disc to allow maximum heat transference to the atmosphere, by whatever means - radiation, convection or conduction. Some heat will inevitably be transfered to the calipers, hydraulic fluid, hub and what-not. You don't want the heat to get to the hydraulic fluid, but the other bits and pieces will help transfer heat to the atmosphere - good-oh I take my hat off to AMMO, what common sense I've been reading "Niki Lauda Formula 1" and his discussion of brakes includes the item that they used to have to partially blank-off the brake cooling duct inlets during cold weather for the first few laps of practice sessions otherwise the brakes were TOO COOL for efficient friction production. Lots of different pad materials are used to give different friction at different temperatures. Trial and error will ultimately determine which is the best for your application. Pagid (I forget the spec.) seem to satisfy lots of people because of their wide temperature range/good friction-ness. The speed thing is handled by the kinetic energy bit that needs transfering to heat in the brakes, then to the atmosphere. Kinetic energy is 1/2 the mass of the car multipled by its velocity squared. The "Speed Kills" ad. on TV is a good example, though this information would probably not go down too well with the soap opera fans. ROUGHLY: 35mph instead of 30mph is a 16 percent increase in velocity, but because of the speed squared function, gives a 34 percent increase in kinetic energy - that extra energy (more than you thought - huh?) must now be into heat by the brakes - bummer That will take more time with a given set of brakes (in the same conditions); read more distance. Result? Dummy child gets clobbered. 🙆🏻 All the time there is a difference in heat between the brakes and the atmosphere, there will be a disipation of heat, but is that disipation quick enough before the brakes (disks and pads) get too hot and "fade". 64 thousand dollar question, or what 😬 Ventilated discs must be better at transfering heat to the atmosphere because they have not only a greater surface area, but, I would immagine, a path for air to flow between the disc inner and outer face, maybe these multiple paths are even convergent (get smaller in the direction of flow) and thus speed-up the air flow. Air cooled engines use fins for the purpose of increasing the surface area of the cylinders and heads to increasing the rate of heat transference to the atmosphere - very small fins too. Rolls-Royce prefered liquid cooling. Pratt & Whitney went for air cooling. Both built REALLY powerful engines (3000 bhp+) . Which method was better? Now there's an idea. Liquid cooled brakes 😬 Waiting for my BRG SV kit. 😬 Is there any other colour? (Superior Version) - 10 weeks to go! Link to comment Share on other sites More sharing options...
scooby dooby doo Posted January 24, 2003 Share Posted January 24, 2003 Amm - babelfish reckoned that you were saying i was a cabbage, crazy, drunk and a woman. hmm... I think machine translation has someway to go ❗ Tony - liquid cooled brakes have been tried i think. some systems circulate the brake fluid as well... HOOPY 500 kg R706KGU Link to comment Share on other sites More sharing options...
Jeff Posted January 24, 2003 Share Posted January 24, 2003 I have completed the Rally Design Wilwood conversion. Some thoughts. 1. The weight saving was minimal as the weight of the ventilated discs offset the reduced weight of the caliper. 2. I had to machine my hubs for the system to fit properly. Of course they don't mention this in the catalog. 3. The system has performed well. The car is used primarily for track days. Has anyone had experience with the Wilwood polymatrix pads? Is there a disc with an alloy hat or bell? Wouldn't this help with the wight issue? Link to comment Share on other sites More sharing options...
Tony C Posted January 24, 2003 Share Posted January 24, 2003 Hoopy, The liquid cooled brakes was a tonge-in-cheek comment, not really practical in this context, sorry for my silliness Your rotating mass thingy is now up and LOOKING GOOD 😬 Cheers, Tony Waiting for my BRG SV kit. 😬 Is there any other colour? (Superior Version) - 10 weeks to go! Link to comment Share on other sites More sharing options...
EFA Posted January 24, 2003 Share Posted January 24, 2003 Ora sono molto confuso. Ma lascia giusto per denominarlo "il cavolo" .........Quanto tempo fino a che non scopra?? Link to comment Share on other sites More sharing options...
AMMO Posted January 25, 2003 Share Posted January 25, 2003 Maurice Scopra o scopa? Hoopy e' una brava persona e ovviamente molto in gamba. Dimmi un po' di te. Sei Inglese che vive in Italia? Probabilmnete Milano, lavorando per una banca? Oppure innammorato di una bellezza Italiana e ripigi ritratti in una mansarda? Ti piace pasta e fagioli? Breadhead or Artist? Hoopy That there Babel Fish seems spot on to me. Them there computers are fantastic. 😬 AMMO Link to comment Share on other sites More sharing options...
Peter Carmichael Posted January 27, 2003 Share Posted January 27, 2003 Hoopy, you can use whatever bolx. made up term you like, but the correct engineering term is "forced convection". Do a web search, find the equations, work out how to apply them, come back when you are done. Heat transfer from a solid surface to a fluid phase is convection. It is not conduction. Sort out your conceits because you started with implied criticism of somebody telling them that convection couldn't happen. They were right, you were wrong. Sort out those conceits. Right terminology/wrong terminology. No argument. About the "most energy is stored" thing. Yes, I restate: most energy is stored "during the course of the stop". Did you not spot that last bit in my explanation? How tiresome it is explaining everything many times over because you don't read what is written. 5 seconds duration of the stop; where does the energy go?. (I made a mistake: I forgot to divide mV^2 by 2, so my 1.5 million jouls should have been 750,000 joules all along). Now, why not think a bit about braking recovery. 5 seconds to apply a big stop, 20 seconds to get back up to speed again before the next big stop. There, we have a duty cycle for the brakes and can design such that it is suitable. Our 750,000 joules need to be dissipated in 25 seconds. In the first 5 seconds we are applying the brakes and we might dissipate a bit over a fifth of the energy, but that means that a bit under four fifths needs to be stored: "most energy is stored" QED. Where are you going to put it? 600,000 joules. Five seconds. Where do they go? A: In the brake disks. Heavy brake disks are good at braking. I would quite like people to stop misquoting me. Cast iron is not brilliant and heat conduction but that does not mean that the material bulk doesn't come into play. It just means there are temperature gradients and hotspots. By the way, I am learning to by having to put some numbers into the equations. In order to dissipate more heat, we need more temperature. Interesting. Heavy brake disks will drop temperature less between brake applications, but will have lower peak temperatures. They might take longer to get up to temperature on initial application. Heavy brake disks make it easier to maintain a high average temperature (most heat dissipation) without hitting an unwelcome peak temperature that causes problems. Everything I have written has said that heavier brake disks make better brake disks. I have not addressed any issues of applicability to use in Caterhams. I just need to get as far as reckoning that losing a kilo out of standard disks is (by my gut instinct) much too much. Try it indeed, as Ammo suggests. And pray that the mode of failure is not... Eccessive heat (from the much higher than normal peak disk temperature) conducted into the caliper much more effectively (by using a more conductive, metallic based pad) to the point that the fluid boils, with the first indication being a lack of brakes when you need them at the end of a big bastard straight and you have 100 miles an hour to shed in a hurry. As Arnie has experienced. This results in trips to the tyre wall, barrel rolls and a hasty dice game with Mr Death. Are you sure? Link to comment Share on other sites More sharing options...
I reply to every thread Posted January 27, 2003 Share Posted January 27, 2003 & you could go to the gym a couple of times a week & lose the same amount of weight from your "Sprung weight" without the risk of brake problems. .......... Link to comment Share on other sites More sharing options...
Peter Carmichael Posted January 27, 2003 Share Posted January 27, 2003 Could swap to flared wings to reduce unsprung weight... Link to comment Share on other sites More sharing options...
AMMO Posted January 27, 2003 Share Posted January 27, 2003 I'm not so sure there is a kilo to come out of a disc. I'm not sure I would do it anyway. A bit of weight removal is OK but I wouldn't risk my life to save weight. I do believe in leaving some bulk in both the the caliper and disc. My experience with racing motorcycles has shown that in certain instances that a heavier (and cheap) Brembo cast caliper gave better results than the lightweight (and expensive) billet caliper. Sold the billet calipers and ran the cheap ones (until we could afford something better still, AP 6 pot). Did try three different brands of pads in loads of different compounds to get the result we wanted. Most of us don't go that fast or use the tyres that warrant super dooper brakes. I've managed to do around 118 mph on the back straight, two up at Snett abd still sort of stop on road pads and stock calipers. AMMO Link to comment Share on other sites More sharing options...
Mike Biddle Posted January 28, 2003 Share Posted January 28, 2003 AMMO, I run 13" Image wheels over the 280 MM Hispec set up. Jeff, My Hi Specs have aluminium bells. Link to comment Share on other sites More sharing options...
aph Posted January 28, 2003 Share Posted January 28, 2003 to be honest I'd probably agree with PC as the higher mass will in effect allow you to absorb more heat in the short period that your braking before disapating the heat to the atomosphere through the disk + wheels. The heat does have to be stored for a short time until it can be disapated. Link to comment Share on other sites More sharing options...
Graham Perry Posted January 28, 2003 Share Posted January 28, 2003 Does a thicker heavier disc take more time to disapate the heat than a thinner lighter one ? Link to comment Share on other sites More sharing options...
Fast Westie Posted January 28, 2003 Share Posted January 28, 2003 Has anyone had experience with the Wilwood polymatrix pads? I ran Polymatrix D on the front of my Westfield racer for two seasons! During that time at the rear I went through two sets of M1144s, one of Red Stuffs (one track day and 1 race day) and a set of DS3000s. Most, if not all, 7 type cars I race with use solid disks and AP or Wilwood calipers and I have not heard of anyone running out of brakes or cracking disks. I think some of the Caterhams use GT6 disks which are a bit thicker than the standard Herald ones. The car in front is a Westfie1d Link to comment Share on other sites More sharing options...
scooby dooby doo Posted January 28, 2003 Share Posted January 28, 2003 I think you got out of bed the wrong side this morning *wink* I wasn't saying your term is wrong - merely that what I thought of as (simple) convection didn't seem to be happening. But that heat was obviously getting lost by some process which you called "forced convection". fine, i don't mind what its called... About the "most energy is stored" thing. Yes, I restate: most energy is stored "during the course of the stop". Did you not spot that last bit in my explanation? How tiresome it is explaining everything many times over because you don't read what is written. I didn't say it wasn't stored. I asked you to show/work out/explain your views on whether the disk is a good enough conductor to take heat from the surface and into the bulk OR a sufficiently poor conductor that most of the energy ended up as surface heat. You mentioned both points - which dominates? If its the former then big heavy disks have merit. If its the latter they don't. I can happily accept either answer but haven't done the calculations to work it out. It sounded like you had, hence my question. Where do they go? A: In the brake disks. Heavy brake disks are good at braking.but where in the disk 🤔 If the disk was made of a perfect insulator it could still store all the energy by the surface getting fantastically hot and the centre remaining cool. This is what I'm getting at. By the way, I am learning to by having to put some numbers into the equations.please do - my education in this area stopped in the second year at uni... Heavy brake disks will drop temperature less between brake applicationsagreed but will have lower peak temperatures. They might take longer to get up to temperature on initial application. I think (again, gut instinct) that this takes effect over several applications, not just the first one. but when warmed it does seem reasonable that they'll maintain the surface temperature better and lose heat better. Everything I have written has said that heavier brake disks make better brake disks. I want to see some numbers before i entirely endorse that. also heavier may (or may not) have some negative effect on how long it takes to get upto temp. I just need to get as far as reckoning that losing a kilo out of standard disks is (by my gut instinct) much too much. Try it indeed, as Ammo suggests. And pray that the mode of failure is not...Are you sure? Any play with brakes would be accompanied by much playing with temperature strips. if we know hot how the pads / disk can survive (peak local temps) and we can measure those peaks then going out and doing half a lap, check values, a lap, check, 2 laps etc etc is a safe way to progress. combining this with testing somewhere safe and breaking very early is safe. trying it at a race meeting isn't. HOOPY 500 kg R706KGU Edited by - hoopy on 28 Jan 2003 23:09:14 - mismatched [ quote ] marks... Edited by - hoopy on 28 Jan 2003 23:09:56 Link to comment Share on other sites More sharing options...
I reply to every thread Posted January 29, 2003 Share Posted January 29, 2003 Or you could just stick with the AP brakes that may be marginally heavier but are a tried , tested, and developed design. Link to comment Share on other sites More sharing options...
V7 SLR Posted January 29, 2003 Share Posted January 29, 2003 Apologies if I've missed this bit, but what are the merits of a larger diameter disk? I would imagine greater leverage, yes, but at higher circumferential speeds. Essentially the brake (disk, pad and calliper) has to dissipate the same energy regardless of disk diameter, so I would imagine the benefits are in pedal feel?... or is it the fact that you are able to use a larger pad thus increasing the friction area? Also, in the context of heat dissipation, am I right that the hotter a disk gets, the more efficiently (quicker) it transfers its heat to the air passing across its surfaces? I'm just thinking along the lines of Chelspeed's front disks which are solid, but large. There's still a reasonable (to my untrained eye) amount of mass there, aided by their increase in diameter, but he is using the same AP callipers (albeit "thinned") so the potential benefits of larger pads cannot apply. Although my AP front brakes work very well, I cannot help but think that there's a lot of weight there for such a light car and wonder if there are potential weight saving to be had. When assembling the car the uprights, hub and disk came as a single unit and felt rediculously heavy. I'm not sure which part was to blame most though. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Peter Carmichael Posted January 29, 2003 Share Posted January 29, 2003 Large diameter discs need lower clamping forces to achieve the same braking. This can be reflected in the pedal effort/pedal travel. So, yes the advantages are in pedal feel. Yes. The hotter a disc is, the quicker it loses energy to ambient. Hoopy, Glad you took the robust argument so well. Lets move on. Surface or bulk temperature? Bit of a red herring, that one. A surface is just that. It has no bulk; no thickness. It has no mass. It can have a temperature, but it doesn't have a capacity to absorb heat. The heat *is* entering at the surface and through a mechanism of temperature gradients it is heating the bulk of the disc. Not evenly, that is certain. The conduction of heat into the thickness of the disk will have something close to an exponential distribution. This link has a thermal image of cast iron vs. aluminium metal matrix brake discs after a braking cycle: Have a look at figure 2 I have dodged the question, because I haven't got the numbersfor the conduction of heat in the disc, but it does suggest that excessive thickness can be removed without problem. Still don't reckon there is excessive thickness to remove. Still reckon the smartest move for weight reduction is use of an exotic material. Lotus seemed to think the approach had merit. Link to comment Share on other sites More sharing options...
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