I need to fit my willwood handbrake callipers to the rear hubs which I intend to do with aluminium plate.
What would be the best thickness for weight / strength, is there any other metal that would be better, and where is the best place to purchase? I will
be having them water cut.
Regards, John
Steel would be a much better choice - less chance of fatigue cracking over time.
Steel plate at 6mm thick would be enough for the braking forces.
But I'd aim for at least 1.5 x thread diameter for thread engagement of any bolts that tighten into a thread in this bracket.
If you have a 10mm diameter bolt then I would allow 15mm thread depth.
Thanks for the reply. I will look at some steel plate. I was not intending to tap a thread in to the plate, just use nuts and bolts to hold the
calliper on.
John
I'd go for steel plate as well for the long term strength of it. You could get the parts laser or water cut from a dimensioned drawing, which would make it easy to fit.
As it's only a handbrake caliper you probably would be fine with alloy, unless you intend doing loads of handbrake turns of course
Well the callipers are alloy.....why is it assumed that aluminium will crack earlier? Why is it assumed that if designed properly it will crack at all?
The issue is designing it properly.
I am assuming you don't have access to the right Finite Element Analysis tools nor have the expertise to use them. Like most on here 
If you had access to these things then you could design an Aluminium bracket where the overall stress levels would remain below the materials fatigue
threshold. Then the Aluminium part wouldn't crack and would be strong enough to resist all the caliper loads. Which is what the caliper
manufacturer has done.
If you don't have those tools/skills then you have to over Engineer the bracket and the best way is to use Steel 
quote:
Originally posted by JAG
The issue is designing it properly.
I am assuming you don't have access to the right Finite Element Analysis tools nor have the expertise to use them. Like most on here
If you had access to these things then you could design an Aluminium bracket where the overall stress levels would remain below the materials fatigue threshold. Then the Aluminium part wouldn't crack and would be strong enough to resist all the caliper loads. Which is what the caliper manufacturer has done.
If you don't have those tools/skills then you have to over Engineer the bracket and the best way is to use Steel
http://www.rallydesign.co.uk/product_info.php?cPath=562_579&
products_id=4023 
RD have over Engineered in Aluminium.
I say it's easier and safer to over Engineer in Steel.
The OP can make his own decision in which he prefers - if you buy from RD at least you can get them replaced if anything goes wrong
Easier for a home builder to over engineer in steel and sleep tight at night.
Calipers are ali but they are forged and designed with all the forces taken into consideration.
RD brackets may be ali but who knows what thought/development has gone into these? Or what grade of Ali they are??
I used aluminium for my rear caliper mounts, similar in design to most radial mounted caliper brackets.
I'd suggest 6082 T6 as the material grade to use.
You can get a basic idea of what I did here https://jpsc.org.uk/forum/viewtopic.php?f=4&t=1209&start=10
Keith.