So I'm upgrading the brakes on my '84. I already replaced the knuckles to use the larger 14mm bolts used on the '85-'87 setups and CNC plasma'd the following pieces;



The two outside holes can be run through for the C5 brackets. The inside holes need to be tapped to connect to the C4 spindle. They'll be M14 grade 10.9 (+) bolts.

Question I have, the material I used for the upgrade was A50 plate steel (50ksi min yield). Grade 10.9 is 136ksi min yield. Obviously this is a huge difference in FOS. I was thinking I could either tap the thread into the hole or weld in a nut. Welding will obviously change the material properties so I'm pretty much against that option. Another option is coming from the other end and throwing a nut on the back but I'll have to check clearances etc; this may not be a viable solution.

I looked online and no-one says the material they're using for their brackets. My guess is they're mostly using the cheapest stuff they can get their hands on (A36=36ksi yield).

So for those of you that have done this route, making you own brackets, what material did you use? I'm going to run some of the numbers and check it out in ansys to see what sort of numbers/deflection/stress I should be seeing. This car will be on the track with some aggressive pads so last thing I want is a "Oh crap your brakes exploded" moment.

 

So updating this for someone else who may stumble across it:

I took to analyze this design during my lunch. I was extremely conservative in the approach. First, getting some numbers:

Basic Kinematics:
v_f=v_0+at
F=MA

Going to http://en.wikipedia.org/wiki/Chevrolet_Corvette_C5_Z06, a 2004 Z06 weighs in at 3115lbs (1413kg) and does 100-0 in 4.365s. [(zero to a hundred to zero time) - (zero to a hundred time)]

Basic conversion:
100mph = 44.704m/s.

Using the math, that requires 14.47kN of force to get it down to speed. Since this is going on a race car, I redid a couple of the numbers. I assumed with more aggressive pads in an absolute panic, we could do it in 3.25s. I also assumed that our stripped out C4 managed to come in heavier than a Z06 at 1475kg (3250lbs).

I get an acceleration value of 13.755m/s^2 and a resultant force of 20.288kN. I assumed the fronts would do 90% of the braking. Designating 18.259kN of force exerted by the front brakes.

I assumed an absolute worse case scenario; that only ONE of the brakes would be offering this force. Since the brakes consist of two bolts, this load would be split on the bolts (9.129kN).

With all these assumptions, I ran it through ANSYS 14 under A36 steel. This is the cheapest you can get and probably what most vendors use. With bearing loads and fixing the model at the two inner holes where the bolt attaches to the knuckle, I got the following result:



Max stress is 1.69e8 Pa or 24.656kpsi, which is under the yield stress of A36 steel. (I'm using A50 which has a minimum yield strength of 50kpsi or double what we would see.)

That counts for half of it; this is considering a single static loading. Seeing how the brakes will be used multiple times, I took a look at the endurance limit as well.

Assuming the lowest tensile strength of A36 steel is = 58kpsi
Using Lipson Noll criteria:
Surface Condition (Machined): k_a=a(S_ut)^b = (2.7)58kpsi^(-0.265) = 0.920566
Size modification: k_b=1
Load modification: k_c=0.85
Temp modification (assuming these brackets would get HOT): k_d@800f= 0.872
Reliability modification: k_e@99.99% = 0.7
Misc effects: k_f=1.15

Se = (k_a)(k_b)(k_c)(k_d)(k_e)(k_f)Se'

Se = (0.920566)(1)(0.85)(0.872)(0.7)(1.15)(36 kpsi) = 19.77kpsi
Since my load (24.656kpsi) is greater, this will ultimately fail after some cycles. I plugged in my value for A50 steel (having a minimum yield strength of 50kpsi) I achieved an endurance limit of 27.464kpsi which is under the max load. Seeing how I previously took some pretty conservative assumptions (one wheel doing 90% of the braking) I feel comfortable in this number.

So for future people, if you want to make these brackets for track abuse, to be on the safe side, use ASTM A50 steel or stronger. A36 may be cheaper and could work since I was really really conservative in my analysis, but it may eventually fail!

If you don't want to listen to me, you can do the math to 'predict' the service life, N=(24.656kpsi/a)^(1/b) where a = [(0.95*(S_ut)^2)/Se] and b = [-1/3*log(0.95*Sut/Se)] where N is the predicted number of cycles. Anything over 10^6 cycles is considered a lifetime component.

Feel free to correct my math and I hope this helps someone down the road!

Cheers,

 

Those that advertise the material used always mention ATSM A50 or greater. Those that don't advertise? Who knows!

 

dammmmmm, you either slept in a holiday inn last night or you're a calculus professor. i doubt my kid could figure that out and he's going to be a junior at aggieland. the c4 has an aluminum caliper mated to an aluminum knuckle held together with a cast bracket. the c5 i believe has an aluminum caliper bolted to an aluminum knuckle. i think you will have an issue with the caliper destroying itself before either of those brackets will give.

 

For what I could find (ebay) they don't list the material. Example:
http://www.ebay.com/itm/84-to-87-C4-Corvette-to-C5-C6-brake-adapter-or-conversion-brackets-/131188024707?pt=Motors_Car_Truck_Parts_Accessories&hash=item1e8b6a6583&vxp=mtr
This vendor also chooses to weld the material. Welding introduces internal stresses which can further weaken the material. So if this vendor utilized A36 steel and welded it, it could be ripe for failure.

Even if these were A50, the only way I would trust them is if the vendor had them heat treated after welding them. I'll try to cheap out/take shortcuts if it will help me go fast. I won't cheap out if I need it to stop

This thread is hopefully to serve on future lookers to make sure that you get a quality part. Suffering brake failure because you opted for someones cheaper kit could be fatal.

 

Even though he's an aggie, I'm sure he could figure it out, albeit with more pain than learned from other establishments . Pretty much the basics of engineering if that's his curriculum.

 

If it's bridging aluminum parts together I wouldn't worry too much about it. First those aren't made out of the best aluminum out there (like what you find in aerospace apps) and second heat takes its toll on aluminum quicker than steel so you should be safe there as well. Bolt it on and let it eat....

 

Still trying to figure out what you said.
It is nice to see that some new blood has ME background.

 

reading this got mah li'l ole haid just a'swimmin' . . . reminds me of the Turbo Entabulator explanation: