Why I'm Making My Own Brakes
- Thread starter lambertius
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lambertius
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lambertius
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First the wishbones and now the brakes, might as well remake the whole car.
Sure, I mean, why not?
lambertius
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Does this mean you have a rotor hanging around as well? If so and you have a spare moment to measure it up, it would be nice to compare my measurements to someone else's!
Thanks for this!
A didact responds:
I should have said "Because I drive like Miss Daisy I've managed to warp them so that they needed skimming"
Eb
lambertius
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I was a bit curious as to how strong brake hats really are, so I applied a basic model made of 6061-T6 (This is what Wilwood and DBA make their hats out of) and applied some forces and had a look at what happened.
Below the image has the PCD as fixtures and the rotor PCD as a force in a tangent direction to simulate braking. I went nuts and each of the 10 mounting holes is 1kN, so 10kN all up - about 10T per wheel is applied, with a minimum Factor of Safety of 9. So roughly 90T of braking force would be required to fail the hats... ****... Its not quite so simple as there are rotations involved, but a 1.8T car, so 900kg a side (so lets round up to 1T), so you'd need to stopping at something like 90g to break the hats... I'll try and work it out properly in the morning...
I also did a low effort topology study out of curiosity using 7075-T6, and got the mass down to 400g.
Speaking of mass - this is what the part would weigh if it were Chromoly Steel:
And what it would weigh if it were 6061-T6
Anyway, I'll keep at it - I'm determined to get something made for at least the front wheels this month.
Below the image has the PCD as fixtures and the rotor PCD as a force in a tangent direction to simulate braking. I went nuts and each of the 10 mounting holes is 1kN, so 10kN all up - about 10T per wheel is applied, with a minimum Factor of Safety of 9. So roughly 90T of braking force would be required to fail the hats... ****... Its not quite so simple as there are rotations involved, but a 1.8T car, so 900kg a side (so lets round up to 1T), so you'd need to stopping at something like 90g to break the hats... I'll try and work it out properly in the morning...
I also did a low effort topology study out of curiosity using 7075-T6, and got the mass down to 400g.
Speaking of mass - this is what the part would weigh if it were Chromoly Steel:
And what it would weigh if it were 6061-T6
Anyway, I'll keep at it - I'm determined to get something made for at least the front wheels this month.
Gp79
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Sorry can’t get that measurement at the moment, away at work for another month, but do have an old set of rotors in the garage if you can wait?
lambertius
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Cheers, I'll keep plugging along until it is time to hit the go button.
One of the good things about doing things like this as a hobby is that simple economics of production aren't quite the same level of concern. So instead of just making a mounting hat that can be turned out on a lathe of completed on a mill, I decided to unnecessarily optimise my the mass using the topology study I did earlier and some realising values.
I calculated the loads properly this time:
An F1 can slow down at 5g, so I used that as my starting point.
So for my car I rounded up to 2T, and then split that between the two front wheels assuming 100% of the braking force per wheel., so 1T=10kN per wheel.
That means that to slow down at 5g, each wheel experiences 50kN.
Using the rolling diameter of 0.6m the torque applied (and assuming zero slip) at each wheel is 30kNm.
At the 108mm PCD the force applied is now 3/0.108 = 280kN. I applied this across the 5 bolts, so 56kN at each bolt. I then fixed the rotor PCD so that the whole thing would be getting twisted as if the rotor is stationary and the force is being applied without any slip.
Using the scenario of a two wheel, 2T formula one car slowing down at 5g these hubs have a minimum factor safety of 1. So with a more realistic expectation of ~1g each hub has a FOS >5.
It also weighs in at 645g.
With the rotor I've selected, if the hub were steel the total mass would be ~10.8kg. With the aluminium hats, the total mass is lower than OEM at ~9kg. Due to the large rotor I've selected, the thermal mass is higher than OEM but the total mass is lower.
Is any of this necessary? No.
Are you likely to feel the difference using an unobtanium alloy saving you an extra 150g from something normal like 6061-T6 (which is used on race cars). Definitely not.
Am I getting them quote in 7075-T651 because I can and I'm doing this for fun and idgaf? Yes, yes I am.
I'm scared to see how much this monstrosity costs...
The rotors I've picked are directional, maintain the full 57mm swept area (they have a 61mm annulus) and were used by Holden Special Vehicles for silly cars like the Maloo, Coupe GTO and other things with 2T and 6.0L V8s. So there will be no silliness about using narrower pads, or needing to offset the caliper, no dogbones etc. There was also a suitable rotor by Wilwood, but I went with DBA just because of local supply and a significant reduction in shipping costs.
The rotors typically cost ~$300 AUD each, and the simple hats (I'm waiting to hear back on my monstrosity hats) cost ~$300 AUD each. So about $600AUD a corner (Currently about 300GBP). At least in AU, that will be comparable to the cost of the OEM rotors by the time you factor in shipping. I've been somewhat mindful of costs, looking at what aftermarket stuff exists and so far its still worth the exercise. Time to get onto the rears!
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Navcorr
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CatmanV2
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Navcorr
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At least the chicken wasn't frozen.
CatmanV2
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squeeky brakes
Eb
lambertius
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Well, that got a bit weird
Went to look at the rear brakes, and I remember why I got distracted with other things for a while...
I hadn't measured the annulus of the rear rotor and I kept meaning to when I got home, but the car keeps ending up somewhere else while I fix something else... Also, it definitely won't be as straight forward getting something to accommodate the hand brake which was why I was thinking of deleting it altogether and using an aftermarket hand brake.
The blue line is supposed to be some distance between the hat and the braking surface. If someone can get that for me I can start selecting parts.
Went to look at the rear brakes, and I remember why I got distracted with other things for a while...
I hadn't measured the annulus of the rear rotor and I kept meaning to when I got home, but the car keeps ending up somewhere else while I fix something else... Also, it definitely won't be as straight forward getting something to accommodate the hand brake which was why I was thinking of deleting it altogether and using an aftermarket hand brake.
The blue line is supposed to be some distance between the hat and the braking surface. If someone can get that for me I can start selecting parts.
dunnah01
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Have you dropped a 0 there? 1T is roughly 10kN
lambertius
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Reviewing my notes just now, there were actually a bunch of issues with the rear rotor, even deleting the handbrake. The front rotor was easy, Wilwood and DBA both have rotors that are a straight fit, even for the unusually large annulus.
If anyone can help confirm/answer the following it would be super helpful:
1 - What is the diameter of the rear rotor? I measured 312mm but that is an incredibly uncommon size. If it is 312mm, then I'll almost certainly need to pick a rotor of a different size, probably 308mm or 316mm, so it would help to have an idea of the rotor/caliper clearance as well (this is the gap between the top of the rotor and anything it will hit inside the caliper if it were bigger). When I inspected the car initially I took some photos and it looks like there may be a bit of clearance to go slightly larger. It is pretty unusual for the pads to run right up on the edge of the rotor which indicates that the rotor may be undersized for the caliper.
2 - The swept area of the pad. Sometimes you can get it from pad drawings, but the pads in my car don't have a detailed enough drawing when I look it up. Knowing this will help me size the annulus of the rotor if required. The easiest way to work .this out is to measure the wear surface on a rotor, since that is where the pad is sweeping! I used a drawing from Hawk to infer the swept area as ~59mm, which is pretty hefty for rear calipers!
3 - Anyone who has changed the rear rotor/pads with any regularity, if you could comment on how snug the fit was? 30mm thick rotors are far more common than 28mm and I'd be far more likely to fit the OEM hand brake if I can squeeze a fatter rotor in. The line in red dictates the maximum fitment the caliper will allow, yellow the maximum pad width. I looked up the part number of the pad that was in there, DB1356SP, which is a pad used on HSV vehicles. Coincidentally it was the pad that would've been specced for the rotor that I've selected for the front! Anyway, the pad is 16.5mm thick when new, which matches with the thickness of the the Porsche 911 (964) pads which also fit.
Everything is odd in the braking setup of this car, I wish I knew what was going on at the time. They're used front calipers as rear calipers that are effectively the same size (functionally) as the front, which leads me to think the only reason they ran a different caliper was cosmetic.... any help would be appreciated.
If anyone can help confirm/answer the following it would be super helpful:
1 - What is the diameter of the rear rotor? I measured 312mm but that is an incredibly uncommon size. If it is 312mm, then I'll almost certainly need to pick a rotor of a different size, probably 308mm or 316mm, so it would help to have an idea of the rotor/caliper clearance as well (this is the gap between the top of the rotor and anything it will hit inside the caliper if it were bigger). When I inspected the car initially I took some photos and it looks like there may be a bit of clearance to go slightly larger. It is pretty unusual for the pads to run right up on the edge of the rotor which indicates that the rotor may be undersized for the caliper.
2 - The swept area of the pad. Sometimes you can get it from pad drawings, but the pads in my car don't have a detailed enough drawing when I look it up. Knowing this will help me size the annulus of the rotor if required. The easiest way to work .this out is to measure the wear surface on a rotor, since that is where the pad is sweeping! I used a drawing from Hawk to infer the swept area as ~59mm, which is pretty hefty for rear calipers!
3 - Anyone who has changed the rear rotor/pads with any regularity, if you could comment on how snug the fit was? 30mm thick rotors are far more common than 28mm and I'd be far more likely to fit the OEM hand brake if I can squeeze a fatter rotor in. The line in red dictates the maximum fitment the caliper will allow, yellow the maximum pad width. I looked up the part number of the pad that was in there, DB1356SP, which is a pad used on HSV vehicles. Coincidentally it was the pad that would've been specced for the rotor that I've selected for the front! Anyway, the pad is 16.5mm thick when new, which matches with the thickness of the the Porsche 911 (964) pads which also fit.
Everything is odd in the braking setup of this car, I wish I knew what was going on at the time. They're used front calipers as rear calipers that are effectively the same size (functionally) as the front, which leads me to think the only reason they ran a different caliper was cosmetic.... any help would be appreciated.
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lambertius
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You are correct! I went through and corrected the values!
Masser50
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I’m fascinated by all of this and albeit I don’t understand most of it I almost just want to buy some (even though I don’t own a 4200), it’s simply because it can prove Masser parts can be supplied in Australia in AUD!
I’ll grant you none of the above makes sense but then I gave that up on page 2 of this topic....
I’ll grant you none of the above makes sense but then I gave that up on page 2 of this topic....