I've been following your rear disk brake solutions with great interest. I'm particularly intested in the custom bracket you posted a while back and have a few questions.
First, excuse me in that I am not very familiar with stock rear disk setups, but from what I have seen from crusing other's sites is that the stock backing plates seem a little thinner than the 3/8" for the custom brackets, is this so and if yes is the additional thickness simply to properly align the brake caliper??? What is the approx thickness of the stock ones just out of curiosity?
Also, I have noticed that the stock backing plates are always attached to the axel housing with four bolts where as the custom ones use only three. Is this so that you do not have to pull the axels to install??? Is there any other reason?? Think that the three bolts are really sufficient when the general always used four??
I guess that both of my questions are to reasure myself that the design is sufficiently strong. Anyone have any opinions???
Also I was at the machine shop today and mentioned making this bracket and asked if they had any suitable steel in stock, he asked what I considered suitable and I went :confused: Any ideas? 1010, 1012, 1018 ??? Or if it is really well overdesigned anyhow I suppose that any standard steel will do.
And finally, should I look for a dust shield too?? Was that a stock item?
I'd also be intested to hear from 72SSAbody (Joe) on this one too? or anyone who wants to chime in.
Thanks guys.

Originally posted by the walrus:
Any ideas? 1010, 1012, 1018 ??? Or if it is really well overdesigned anyhow I suppose that any standard steel will do.

I'd also be intested to hear from 72SSAbody (Joe) on this one too? This is where it gets really tricky. In reality, you steel supply store will have A36 structural steel in flat stock and tell you that 1018 flat stock is rated the same as the A36.

Sure some metals are, but with today's world that's not the case and the guy behind the counter (I'm betting) knows very little about stress/strain diagrams or for that matter of fact has probably never seen an instron machine or could tell you the difference between a Rockwell hardness scale of B or C in his life.

I remember the post that 454 had the diagram in and can tell you the bracket and how it is mounting is not the 'weak link' in the system. What you really should be worried about is those wheel studs breaking before you worry about the flat stock for the caliper brackets folding over like pancakes. But that's another story!

Tell your machinist you want to use 1018 steel over an A36, A500 or A992 structural steel. Could you use those structural steels? Yes, but 1018 is about 50% stronger at its yield point than A36 and according to the 'Max Shear Stress Theory' will help you out in the end with increasing the factor of safety designed into these brackets without spending a boat load of more $$$.

Is it over engineered? Yes, but does it cost you more weight or decrease the performance? No.

One more thing. If he recommends a 1045 and you have to weld on these brackets than politely turn him down. There is a special annealing process you will have to go through for the welds as they will be brittle and fail without it.

Good luck with the swap!

Joe

Damn Joe... And to think, I actually understood what you said!! Damn that engineering degree !

One quick question that you bought up on the 1018 steel... do you have to do anything special to weld on it?

Thanks,
Bill C. :eek: :D

Originally posted by BC:


One quick question that you bought up on the 1018 steel... do you have to do anything special to weld on it?

You shouldn't, but again...there is a catch! If you ask anyone who has worked in a material science environment you will get the question, "What are you using it for and what is your process you are putting it through."

Add on top of that the many various forms of 1018 steel and you'll quickly see why that's not an easy question to answer. For the average Joe out there, no you won't have to go through an annealing process for the 1018 welds.

Take care guys and good luck on the swap!

Joe

New Idea:
While giving it a closer look on the car I seem to have answered some of my own questions.

For those who are unaware, this is a link to the original post which contains the bracket for which I posed the original question:
original rear disk post (http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=7;t=006601)

First I was concerned about the bracket thickness and strength. After looking at the stock drum backing plate (which I am aware is subject to different forces yet similar to a disk setup) I have decided that 3/8" should be more than enough material for the new bracket. The stock drum one is only about 1/8", although it is stamped in a pattern which may, or may not give it more strength, I'm pretty confident that 3/8" for the new one should be more than enough even using a lower grade steel ie. 1010.

This leads to my next concern which was the use of only three bolts to attach the bracket to the axel. I thought that perhaps this was to facilitate the installation of the bracket without having to pull the axel shaftss themselves. Then when looking today, I realized that you have to pull the axel shafts to get the old backing plates off anyhow graemlins/clonk.gif So why not just use a four bolt pattern anyhow. By this point I had also convinced myslef that this was the weak point in the system anyhow as the wheel studs use five bolts and at a larger moment arm than the four at a smaller moment arm for the brakes.

So here is my plan, using the originally posted bracket as a guide I will modify it to include four bolt mouting to the axel housing. I will do this by using the drum brake backing plate as a template, lining up the first three holes on the bracket diagram and trasfering the fouth hole from the existing backing plate to the new brakcet drawing. I will also attempt to maintain a constant width to close in the existing now open side of the bracket on the axel mounting side. Wish I had a digital drawing to post but I will probably just endup doing it by hand and I'm sure that you get the idea.

Is all this really necessary? Probably not. But will it give me more piece of mind? Yup. And does it take much more effort or make it that much heavier?? Not enough to out weigh the extra reassurance it will give me.

The only thing that I'm still curious about is to know if the 3/8" width will propererly align the caliper over the rotor and if the is a factory dust shield that I should consider.

Still open to opinions and comments. graemlins/thumbsup.gif

thanks for handeling that Joe. :D
walrus, if it makes you feel better do it, but i can assure you it is not necessary. you just need the 3 fine thread grade 8 bolts. actually you can just cut your old backing plates off, you dont have to pull your axles if you did not want to. but the open end allows you to mount the plate on either side of the rear flange. i cant remember which side of the rear flange they go on. you will have to test fit it all up. in one case when i installed new moser axles i had to make an adapter plate to allow the caliper bracket to center the caliper. cant help withthe dust shield concern. http://hometown.aol.com/smartasreality/page11.html

YOU CAN BUY THE BRACKETS FROM THIS GUY RIGHT HERE.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=42605&item=2435443931