Printable View
i like the idea of about 9mm of factory disc safely stopping you, but even the factory discs have a wear tolerance, i have got a disc catalogue somewhere, but i haven't seen it for years... if i can find it, i'll try to find something the right size.
Thanks to Alan (I may not be thanking him before long!!), I have ended up buying those Pretech 6-pot calipers and discs off EBAY;Quote:
Originally Posted by AlanH
http://i285.photobucket.com/albums/l...o6YwcD1_35.jpg
http://i285.photobucket.com/albums/l...6ZJSCRQ_35.jpg
Next comes the small matter of trying to make them fit and work on Nova hubs.............
i bet they cost a pretty penny colin
Ebay link is in post, £225 +pp which for some 6pot brakes is a snip lolQuote:
Originally Posted by stupot89
Seemed cheap to me, and if they can't be fitted on the Nova I'll be forced to buy a Fireblade and put them on that.Quote:
Originally Posted by Ben
didnt see the link :roll:
there is a fireblade for sale on here iircQuote:
Originally Posted by novarally
Just got the brakes, and had a bit of a mock up. The discs are 320mm diameter, and weigh just 1.5kg each (compared to 4.2kg each for my current 247 x 20 discs).
One 6-pot caliper with the pads weighs in at 1.07kg - that is nearly 1kg EACH lighter than my Wilwoods which are 2.048kg.
So potentially if I could get these brakes to fit and work, I'd see a total saving of circa 7kg.
Some photos...........
No chance of fitting these discs with 13" wheels!!
http://i285.photobucket.com/albums/l...ort/002-21.jpg
But with 15" rims (which is what I normally use on the front), they will just about fit;
http://i285.photobucket.com/albums/l...ort/003-24.jpg
Disc mocked up on the Nova upright;
http://i285.photobucket.com/albums/l...ort/004-18.jpg
http://i285.photobucket.com/albums/l...ort/005-18.jpg
http://i285.photobucket.com/albums/l...ort/006-19.jpg
Could it work? Mounting the disc assembly directly to the drive flange? Or via a spacer/bell of some sort?
I can't see why it wouldn't, but I need to seek expert advice.
Do any of the existing holes in the disc overlap the nova 4x100 holes?
Didn't check that yet, but there are various solutions which could overcome that if it's an issue.Quote:
Originally Posted by Welsh Dan
i cant forsee too many fitting issues after all a lot of the off the shelf brake kits are not specific as you know.
My question is the effciency of them on a car, but suppose your car weighing in around 500kg's doing around 60-100mph flat out? compared to a bike about 200kg's doing 200mph is not far off!
That's the logic I'm working with, although whether it's sound physics I don't know.Quote:
Originally Posted by Ben
The larger diameter would have a greater mechanical advantage as well, but anyone who can do the maths or can put the question to someone who can (MK999?), please do!
from a few pages back, aimed at me.Quote:
Originally Posted by Paul
eat your words paul!
great work colin. keep it up :)
the brakes look good, and they should fit.
Actually a 500kg car doing 100mph has about 60% of the kinetic energy of a 200kg bike doing 200mph. :)Quote:
Originally Posted by Ben
http://www.wrc-cosworth.org/tech/bra...lculation.html
that might help you :)
I suppose the bigger question is whether the amount of heat generated by the greater mass of a car would be too much for them to handle.Quote:
Originally Posted by Welsh Dan
stock 236 solids skimmed to minimum thickness & either make caliper spacers or as previously said, cut down the pads will cut the weight, and keep the heat in the brakes. tbh you could probably machine them down further as they aren't expected to carry granny & her shopping & tow a trailer......
Colin, i think your on the money, about the larger mass of car putting to much heat into the discs.
also, another point, is if they were genius, magical answers to saving weight, surly the locost/westy boys would be all over them?
I'll bet a machined down/drilled 236mm solid won't be as low as 1.5kg though!Quote:
Originally Posted by mowgli
Off to the workshop to weigh one now........
It's true I've never seen them used on LoCaterFields.Quote:
Originally Posted by bmw156
I still haven't managed to find out what the Grasstrack cars are using for discs on the front. Some of them are definitely using bike calipers though.
it probably won't colin, but by the time you have a boss made to fit the disc to the hub face, it will weigh more. ps. it does need to be strong, as it does the majority of the braking.....
grass trackers don't exactly need to slow down in a race....Quote:
Originally Posted by novarally
Braking efficiency is massively complex as it depends on the weight, CoG and geometry of the vehicle and the tyres grip levels etc, I do know someone who made a spreadsheet to calculate it as a point of interest but he's now somewhat busy for a year with Force India... lolQuote:
Originally Posted by novarally
Even the spreadsheet was fairly rough though, and it was a good 2 pages or so of various measurements which would be hard to collect without modelling the car from scratch in it's entirety.
Your main 'foe' against them working is the heat buildup though imo, no large brakes have totally fallen over because they cant exert enough force to stop to my knowledge.
Also the KE might not be huge, but the inertia you're fighting will be considerably larger than a bike.
short runs, maybe 10 braking efforts per run, only a couple of them will be full on.. as a guess.. keeping heat in might be more of an issue...
Standard 236mm solid disc is 2.9kg.Quote:
Originally Posted by mowgli
Yes, I think the bike disc would need some sort of mounting bell, which will add weight.
the discs are heated at the surface, and this is not a problem where you have some sort of thickness to it, the outside of the disc may well be hot, but it dissipates into the discs, the bike discs are just over 1.3rd of the weight and higher diameter, so they are considerably thinner, and imo you're going to get the heat from both sides combining in the middle of the disc instead of dissipating effectively through it's thickness, and from there the heat issue is going to be rough.
and if during braking in competition only 8 out of 10 are at full effort something is going wrong somewhere...
i mean, just slowing slightly, setting up for a corner as opposed to slowing to a full stop. i know each braking movement will be hard, but the effort to scrub 10mph off is a lot less than scrubbing off 100mph.
Ah ok, but still I think heat is gonna be an issue, for your example of slowing down 10mph, assuming a total conversion from KE to heat energy (i.e ignoring any that gets converted to sound etc) you heat the discs by about 40c, now I'm not sure what kind of temperature brake fade kicks in but brake fluid boils at around 300, after its travelled into the brake system, so assuming your 10 runs you haven't got any room for any high speed to low braking runs.
edit: and that's assuming the heat is dissipated perfectly.
the discs can get as hot as you like.... its the pads and fluid that will suffer if you dont get the right compounds.
The mass of the vehicle is mostly irrelevant as said the KE is what you are dumping as heat, and then the interia of the drive train (that might be a problem).
I reckon, give it a go with some high end pads and see how it goes
I would have thought it's the heat of the discs that largely decides how much the pads break down into the gas that iirc, causes brake fade? Kinda like touching water with a heated paperclip, or a lump of steel, both still bubble at their surfaces, granted the paperclip cools faster as well though.Quote:
Originally Posted by Stuart
The mass (as a function of velocity) decides the KE though and also I meant the inertia of the vehicle more than the rotating inertia, so that's 2 direct relationships to mass that effect braking, calling it irrelevant is a bit extreme imo, it's one of the main factors that effect braking requirements!
It may not have come across in my posts, but I'm all for giving it a go, but my prediction is heat is an issue, and either extra cooling needs to be employed, or a beefier disc used.
Colin
How about mocking up some fitting then trialing them on a breaker you have in on a long straight at lower speeds to start with, if it ccould handle say the speed/stopping of an xe nova weighing around 80kg's then it will cope with your lightweight model.
I wouldnt fancy trialing it in a competition!
making the mounting bell out of ally will help dissipating a bit of heat. i really cant see heat beaing a huge problem though. you have got a much bigger surface area than a standard disk to heat up first
More weight saving measures..........
Front towing eye removed (weight 230g) and will be replaced by an alloy one at 90g;
http://i285.photobucket.com/albums/l...ort/002-22.jpg
http://i285.photobucket.com/albums/l...sub3030-rd.jpg
And I'm now in the process of removing the double skinned bit in the boot which normally houses the tailgate lock etc. First time using a spot weld drill, so a few blunders so far where I've drilled right through!;
http://i285.photobucket.com/albums/l...ort/003-25.jpg
http://i285.photobucket.com/albums/l...ort/004-19.jpg
good idea batman
have the supports in the roof gone?
and the floor supports? like below
http://i285.photobucket.com/albums/l...cort/007-3.jpg
He has to leave the seat rails in mate. IIRC he reinstated the rest of them after someone complained/commented on them being absent.
Looks great as usual Colin, and as Tesco says 'Every little helps'!
You may have wanted to practice on a scrap shell before attacking your favourite toy (assumes Escort is sold) with the spot weld drill bit though! I hope it's came out OK.
Liam.
I actually did have a practice first!Quote:
Originally Posted by L14MNP
But I'm still finding it hard to drill through enough to cut the weld, but not through the second skin. It's no great worry though, more holes = more lightness.
Very true about the holes. I done similar when removing side impact bars from a door skin. I had to go right through one side of the skin to free the bar (obviously). The holes look good and as you say add lightness, which on your car is essential. I just accepted it as pretty good fortune. lol
Are you using a flat ended spot weld drill or one of the hole cutter affairs mate?
I've got both types.Quote:
Originally Posted by L14MNP
The one that looks like a miniature hole cutter is pointless, you might as well just put an ordinary drill through both skins.
The flat ended one is a bit better, you seem to have more control with that type, but it's not easy to get right every time.
I agree the flat ended normal drillbit style one is pretty good, I found drilling spotwelds quite fun when it goes right.
You can save over 500g by drilling off the seatbelt spreader plates in the B and C pillars, if they haven't already been removed.
He can't touch anything between the wheel centres.Quote:
Originally Posted by iainel
Oh, didn't realise. C pillar ones should be ok though?