New Idea!

[BimmerToad]

This might be a bit dry (got my Deformation and Fracture Mechanics book out):

"when a sample is thin, and the degrees of plastic constraint acting at the crack-tip minimal, plane-stress conditions prevail and the material exhibits maximum toughness"

likewise,

"Alternatively, when the thickness is increased to bring about plastic constaint and plane-strain conditions at the crack tip, the toughness drops sharply to a level that maybe one-third (or less) that of the plane-stress value."

Look at most aluminum parts, they are relatively thin, so that the material fractures in plane-stress conditions, which allow for easily detected cracks, and a greater toughness. This part should be designed tougher than stronger. The brace doesn't support all that much. I don't think the brace needs to be made of solid billet.

The strain-hardening coefficient of aluminum is 1/3rd of stainless steel, so it will respond to work hardening, but not as well as steel. Work hardening makes the material stronger, but also more brittle, so I think it would be a waste of time.

Put the design up in Solidworks and run some FEA analysis. I'm sure what is designed will be overbuilt regardless

Never thought I'd post information from my materials class on r3v ;)

[02stu]

I'm pretty sure that decreaseing the wall thinkness will only significatly lower the chance of fracture in polymers. As far as extruding the mount for strength goes, I can't remember for sure but I don't think aluminum responds all that well to work hardening. Sounds like Brandon would definitly know. Can someone send me how long this thing needs to be, and any other dimensions you have? Thanks
-Stu

[joshh]

What do you guys mean by filleting the edges or corners? Would this be adding "ribs" to the inside corners?

[Beej '86 325es]

Yes, what Stu said about the filleting the internal corners is important. I'm an aircraft structural design engineer, so I work with aluminum constantly. I work in SolidWorks as well and can help out with this type of stuff too. If you want a second eye looking at this, send me a copy of what you've got.

thnx

[Addissimo]

check your pm stu

[rede30]

If it comes down to needed more people to buy i might buy two, hell i might buy two and sell one for some money if a year or two

[e30sd]

i'll buy 2, one for me, and one to throw at todd.

100 bucks is fair imo, anything cheaper is sweet.

[BimmerToad]

Filleting the edges is a must, and having a much thinner bracket would be nice. Most applications that use aluminum use it with a much thinner wall. From what I remember from an engineering materials class I took, the materials resistance to fracture increases when you decrease the thickness. (I'll re-read that stuff after finals week)

Did you modify the right mount geometry too, or just the left side?

Good initial design. Hopefully a final product will come out of it :D

[02stu]

That design looks good to me, but if you want I can draw up any changes you had in mind. I've never used there program but I could draw up a brace on a more widley used program like solidworks that I know they would accept. PM me what you had in mind, it wouldn't take me long. I'm not sure how it would effect the cost but if we filleted the edges we could get rid of the stress concentrations and have a much stronger part with less material.

[Addissimo]

It'll look like this:



its 1.45" thick.

This is basically the only design I can really come up with that makes sence. We could make one that is extruded like the stock brace, but I'd have no clue how to go about designing that. I think this will give us the most strength and lightest weight.

[BimmerToad]

What material and thickness is the brace going to be made of? 1/4" billet AL?

Regardless, I'm interested in a brace

[02stu]

Wow, thats all I can say. Addissimo do you have a paypal account? If so I'll send you the money now, and when ever you get the parts is fine, no rush. Just send me a total and if its ends up being more I'll send you more. If they are being sent to you I'll send you a prepaid package. Thanks again Addissimo!

-Stu

[Kilomph]

Addissimo, you're the man. I'm in for the IE poly as well.

[bmws50b30]

It doesn't come with tranny bushings-

If we can get 10 or more people to order poly bushings from ireland, we get 15% off of $80 for a set, so about $70.

Keep in mind this will require drilling and tapping a hole for which ever mounts you decide to use.

If we get a group buy going on the mounts, I'm willing to do the labor on this for a small fee (probably like $5 or something)

-Addis

poly bushings would be nice but my priority right now is to have the correct bracket. drilling the holes bigger should be easy. the brackets have the mounting holes pre-drilled, correct? when would you start production of these?

[erik325i]

I'm in if we can get it in the ~$60 range. I won't be installing my motor untill mid January, so that's no problem for me.
-Erik