bolts

Bamboo bolts, why didn't I think of that. If you made the frame out of bamboo you could have a bike bong. :silly: Gives a new meaning to Kawi green. :sick:

Ok I found a solution use 18-8 stainless. In the sizes that you need it's comparable in tensile strength to grade 5. That seems like a good compromise. www.k-tbolt.com/bolt_chart.html Still gonna be more expensive, but definitely better looking.

Personally I don't like fancy pants stainless bolts and such. All the bolts in my engine are now black oxide allen cap screws.

I don't understand how super high tensile strength can matter for bolts in any application, even though I am sure it does matter. I'm not being wise-guy, I am genuinely confused by the following: By definition, tensile strength is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract. In order to stretch a bolt that is attached with a nut I would think the stress would be pushing outward against the bolt head on one end and against the nut on the other end. Assuming this is so, I am surprised that the threads between the nut and bolt wouldn't deform and strip out under that extreme pressure before the bolt (which has more cross section than the threads) stretches. It just seems counter-intuitive to me that the threads can take more stress than the bolt, although I'm sure this has been proven many times. Ed

You're right ed, but the main reason we go around talking about tensile strength is that its the main way of testing a metal. So when comparing bolts it's a decent way to compare them.

There are generally two categories of bolted joints. One where the joint is being pulled apart in the axis of the bolt(axial), and one where you are pulling the two parts of the joint apart perpendicular to the bolt. In both these scenarios the tensile strength is important, as you will tighten the bolt to a certain percentage of the bolt's "proof strength" which is itself a percentage of the tensile strength.

In the axial case you design a joint so that the load in the bolt compresses the joint to the point where the joint load will not separate the two halves.

In the perpendicular case, the tension in the bolt causes friction between the two joint surfaces. This is what prevents the joint from being pulled apart. Most people think it is the shear strength of the bolt which keeps it together, but in a properly designed joint of this type the applied force will never overcome the friction force between the surfaces that the joint creates.

I hope that was clear enough.

Heres a picture for clarification. The Fs is the force I'm talking about in the perpendicular case, and the Ft is the applied force in the axial case. The Fp is the force in the bolt, caused by torquing the bolt. The Fc is Fp minus the reaction force from the material, because the joint itself acts like a compression spring and pushes back. As long as Fc is greater than Ft, the joint will not separate in the axial case.

stainless will shear /brittle/the heads strip easier in most applications than other fastners used in the same applications.......i aint no engineer..and i aint no welder...but i twisted the heads off of more than few A325 3/4 bolts as an ironworker and the fact that they twist and stretch a great deal before shearing and breaking tells me something......

for what that is worth


as far as selling sats of motor mounta or brace kits for that matter...even when just seeing if folks would be game for said products...it imo helps greatly to have said items displayed on a bike or a mock up so folks can gauge their interst level...i think if someone were to put a few sets on display it would generate a GREAT deal of interest

I think go with some nicely coated carbon steel grade 8 bolts. Black oxide is my favorite.

testarossa wrote: Ok, are you going to have ARP make your mount bolts using their special alloy stainless? If not then regular 304 ss is more like 75,000psi and 316 ss is closer to 84,000psi. Both less than grade 5 fasteners. Aside from that, you cannot compare the tensile strength of a fastener to a mild steel frame. They experience different types of loads. Yes the bolts are in tension, so tensile strength is an apt measure of their performance. However, the frame is not simply in tension. Tensile strength is not the only qualification for material selection. Heck, bamboo can have a tensile strength approaching 72,000psi, should we make our bolts from bamboo? It's an apples to oranges comparison. Different materials fit different applications. In my opinion, yes, the ARP stainless bolts, if tested to 170,000psi are a superior fastener, but regular stainless is inferior to even grade 5 fasteners, and more expensive to manufacture.

they also have regular grade 5 rated stainless steel bolts which are still over rated compared to rest of materials/fasteners on the bike.
would you weld the frame together with welding rod rated at 100,000 plus psi? :laugh:
apples to apples?everybody keeps talking about the lowest end of the stainless steel food chain like its the only bolt you can get,they make steel bolts that are lower than grade 5 also.
What grade do you think those studs on the bottem of fork leg caps are rated at?
heres a clue,theyre the same stud used for kz1000 exhuast studs and they snap off pretty easy with a 3/8 ratchet! :laugh:

Are you guys speaking of KZ bolts or NASA for the space shuttle?

Damn, I guess my KZ is under rated on torques and such... whoa...

EDIT: typed at work by special ED

one other thing that i have been thinking about on items such as exposed motor mounts(trick racer stuff/bling)oil cooler fittings,block off plates..ect....but lemme stick to exposed bolts/motor mounts...is that i am at the stage on my project where i am gonna have something pretty close to "special" imo...as well as many others here who already have their build completed or say some of the builds close now on the forums.....

and being that the main design/themes are already close....the little things like porsches steering nut or the like need to be of the kind of quality and finish that they will be able to stand the test of time on the project...sounds simple but already some items that were once trick have begun to fade or discolor.....

my goal if i spend 300-400 to mount a trick earls oil cooler and fittings ,is to have the execution at the top level...ie ...like the race teams turn out stuff, super tight and sano and not tie wired on ...not a second rate finish or in a year have it start to fade or rust....

what good is a trick aluminum motor mount triangle if the heads of the fasteners only stay nice a season or two...or what good are block off plates if the bolt heads rust...makes the whole thing look crappy....

aim super high on the stuff imo..it cant be too good...price on these items really is set by the final bottom line of what makes the cut imo

Comparing the material in the bolts to the material in the frame is certainly comparing apples to oranges. One is a tube and one is a bolt. Different application, different material. The reason why the exhaust studs break off is most likely down to the normalization that happens to them over the years, any heat treatment they underwent during manufacture is probably moot after they run up to around 3-400*C for a few minutes.

Any M8 bolt will snap off with a 3/8 ratchet, doesn't matter what you have. Tensile strength is one thing, but as soon as you start twisting it you go into a torque regime, and the stress induced by torque is magnitudes higher than an axial force, which the bolt is designed for. Thats why bolts have a toque rating that might seem low, but in the case of something like engine bolts, they are usually designed to go up to 90% of the proof strength when torqued, thats why sometimes when you overtorque it seems like the bolt snaps off really easy.