Would you trust 16 aluminum fasteners (m10x1.25 30mm long) to hold a rubber mounted (with poly inserts) 400hp engine moving a 2000lb car on race tires? These bolts hold the engine mount to the body. Titanium is WAY more expensive so I'd rather only use it for the single bolt that goes through the eyelet part of the mount.
The commute attack mr2 spyder is on a big ol diet ;)
I wouldn't trust an aluminum bolt to retain the motor to my lawnmower, but I just broke a pair of aluminum Skunk 2 control arms in less than 16 hours at a Chumpcars race. There are places where steel is the answer.
I fully admit to a distrust of aluminum in many applications.
BMW uses aluminum bolts, I do believe M10 but quite possibly M8, to hold the engine mount brackets to their magnesium-blocked engines. Four per side, and the mounts are not close in to the engine in the least. The brackets have maybe 6 inches of overhang and the bolts are spaced maybe 3-4" apart on the block.
They do break on occasion. They're torque to yield in a very real sense. They start to deform almost immediately after the base torque.
I am with Streetwiseguy on this one. No way on aluminum bolts. Steel!
A Lot of people (myself included ) including porsche run aluminum lugnuts (7075 alloy) with good results.
Seems like a math problem, figure out the force and moment, and then decide if you are comfortable with the safety factor.
You could also stick with steel and look at reducing weight by cutting bolts to minimize the protrusion past the female threads, Center drilling the bolts to remove material (with minimal impact on shear and torque), and/or turning down portions not used to located the brackets or mate with female fasteners to the minor diameter of the thread.
Use 12 aluminum and 4 steel.
What's the benefit of aluminum? Weight savings?
Have you calculated the approximate weight difference between steel and aluminum fasteners? I'm guessing it's probably less than a pound difference and in my mind that's not worth the potential trade off in the factor of safety. There's also the hassle of galvanic corrosion and having to replace bolts for service as they are often torque to yield. If it is worth the added hassle, cost and weight savings, then you need to do the math to confirm and more information is needed than what you've supplied.
Biggest issue with aluminum in a lot of applications is limited fatigue life. It very well may be strong enough, but you also may need to replace the bolts every 10k miles or something to avoid them weakening and failing.
I would worry about galvanic corrosion, a lot. Aluminum against steel results in a lot of sticking, and a dozen aluminum bolt threads that break off in your body as you try to remove them would suck to have to extract. Sure it drills easily but that would be a pain!
But I have no experience with it, so my advice isn't worth a lot. ;-)
No.
I do have experience. and if you used enough rivets in the Proper order it would be OK but I wouldn't take the Time to do the Math. Some aluminum Bolts would be much better than Rivets but if using 2 steel frame mount bolts and 3 engine (avg.) your weight savings is Ounces Not Pounds, saftey factor is likely 10 times of rivets
Aluminum, it may be half as strong, but at least it only weighs half as much!
Master's Degree in Mechanical Engineering here, and 17 years experience in the field, plus a class specifically in bolted joint technology. I have never used an aluminum bolt in any critical joint. I look at it this way: if I wouldn't be comfortable using a nylon fastener in a joint, I won't consider aluminum.
In reply to volvoclearinghouse :
Agreed. Steel for bolting unless something wacky is going on. You almost never lose actual weight without losing safety factor.
400hp in an MR-S with r-compound tires will put more stress on the stock engine mounting than it was originally designed for, presumably with steel.
You are already eating into whatever margin of overbuild is designed into the stock mounts. Not a place I would look to save weight. You may find yourself adding some back as it is?
Sticking with the 1ZZ?
volvoclearinghouse said:Aluminum, it may be half as strong, but at least it only weighs half as much!
Master's Degree in Mechanical Engineering here, and 17 years experience in the field, plus a class specifically in bolted joint technology. I have never used an aluminum bolt in any critical joint. I look at it this way: if I wouldn't be comfortable using a nylon fastener in a joint, I won't consider aluminum.
+1
http://www.jegs.com/i/ARP/070/763-1002/10002/-1?CAWELAID=1710808729&CAGPSPN=pla&CAAGID=44693592161&CATCI=pla-192430937831&CATARGETID=230006180039217645&cadevice=c&gclid=Cj0KCQjwsZHPBRClARIsAC-VMPAnbDxAkl2SFbt0va5UvdfARGfwvYsBlejeqjTdQmn8yyeNdkXdxI8aAt3hEALw_wcB
Should be ~4$ or so a bolt.
No. Race motor is something you want to stay where you bolted it. Aluminum is going to give it way more opportunities to migrate in a violent fashion, and the motor will take it.
Aluminum is very strong in certain applications, like bicycle frames and engine castings. It’s lousy at maintaining its strength under torsion...
Just out of curiosity, I looked up aluminum bolts in the McMaster catalog, which gives the tensile strength the bolts are rated for. They listed aluminum bolts with a 30,000 psi tensile strength. That's half the strength of a Grade 2, and a mere 20% of the strength of a Grade 8 bolt.
This is an application that calls for ventiseiesimo elemento .
In reply to tuna55 :
Agreed. For example, the Tunachucker LTD has two engine mounts supporting an engine of similar power output (400HP) and weighing approximately 700 pounds. This is moving a 4000 pound car on race tires in an endurance race. Approximately 40 race hours have been put on this setup, and the bolts have proven 100% reliable.
Number of 3/8"-16 Grade 8 fasteners used in this application, connecting the engine to the mounts: Two (2). One per side.
Find some other place to save weight.
MadScientistMatt said:This is an application that calls for ventiseiesimo elemento .
I love that. Once I learn how to pronounce it reliably, I am going to start dropping that into my daily conversations.
Tyler H said:400hp in an MR-S with r-compound tires will put more stress on the stock engine mounting than it was originally designed for, presumably with steel.
You are already eating into whatever margin of overbuild is designed into the stock mounts. Not a place I would look to save weight. You may find yourself adding some back as it is?
Sticking with the 1ZZ?
Nope, boosted 2zzge.
I'm doing aluminum for all non essential fasteners and ti for the rest, just trying to minimize the cost. (Ti is pretty crazy). My thought process was that the bolts are going into aluminum, and there are a E36 M3load of em. I might do it just for the sake of research but we'll see.
I'm shooting for Very light weight for this evolution of the car, remaking a bunch of components, deleted a/c, doing some more Swiss cheesing, some carbon panels, yknow the usual street car stuff ;)
In reply to sesto elemento :
The thing is that steel makes an excellent bolt.
Nothing else really does, for lots of good reasons other than cost.
sesto elemento said:My thought process was that the bolts are going into aluminum, and there are a E36 M3load of em. I might do it just for the sake of research but we'll see.
Yeah, it doesn't quite work that way. Aluminum is great for some things, but being a fastener isn't one of them. Plus, bolting aluminum to aluminum with aluminum can actually encourage galvanic corrosion. Then the whole mess won't come apart. Although, when that happens, at least the aluminum is easy to drill out. :-P
The "proper" way to bolt into aluminum is to use steel fasteners, with a threaded insert into the aluminum base metal, and antiseize on the threads of the bolt. You know, like a spark plug in an aluminum head. 
Or bolt through, with a nut and washers.
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