Aluminium alternator bracket + tensioner?

[Sam_Q]

I am making a batch of alternator brackets up and they are a simple F-type shape that uses two bolts to hold on, a simple design really. Vaugley simular to this:





I want to make it and the tensioner out of aluminium, probably 5083 grade. I had in mind to use a 6mm thick strap for the tensioner.

Anyone have any idea if making it out of aluminium will fatigue on me and fail? The design will be more like the top picture except it will have a thicker base.

[SHEPPO3930]

the bottom bracket won't be a problem.

do you have a design for the top bracket/tensioner? i assume it'd be a simple design with 2 bolts holding it to the front of the motor, and a slot (curved to follow the path of the alternator's sweep) that you put a bolt in? if that's the case, and the bracket was under 200mm long, i can't see it being a problem. i've half designed an alternator top bracket for my motor, it will be made from 6mm 5083 (use this at work), and cut on a CNC router.

[Sam_Q]

yes it's pretty much as you describe- an arc with a slot in it and a straight section to connect to extend to the block. From there a simple metal bracket or something as a pivot.

[LeeRoy]

I'd probably go steel for the tentioner bracket as the weight different on something like that is negligable. However, 6mm would probably be fine in alloy.

[Sam_Q]

If it was for weight I would definetly not bother with Aluminium because your absolutely right the difference would be very trivial. However it's very practical for me to get it profile cut where I get all my other parts done, they have the material and work well with me. That said it's probably overdue that I make an account with a steel profile cutter.

[thechuckster]

If the pivot bolt holes allow for any radial movement, an alloy tensioner bracket will undergo some bending when you tighten things up. If you profiled an alloy tensioner arm with a stiffening (correct term?) rib behind one side of the arc, you'd be able to deal with that?

[punkture]

I can test it for you on solid works with the required force etc from different types of loading, send me your prints champ

[Sam_Q]

thanks but I don't know about the forces to give you the right information. Having it handle the stresses is easy, but it was the vibrations that bothered me. I have had things fail before just because of the vibtations. I would of hoped though this being a one piece design that it would be immune form it.

[Supra967]

Honestly... sounds like you're overthinking it a bit. You're average tensioner and alternator brackets aren't anything special. You won't be the first to use thick al plate for engine bracketry. Probably a fair few alts bolted straight to an al block from factory too.

[Sam_Q]

I am but it's because it's not for me. When I sell parts I don't want them to break in one, two or even in five years time. I want everything I make to be as tough and reliable as OEM.