Wanted: online metallurgist

[livewire]

My Kat ( the statue that goes like fuck, but is a high maintenance cunt of a thing - it's a love/hate thing) is proving to be pretty hard on starter motors/ gears/ clutches.(amongst other things)
It's just sheared the 3 bolts that hold the starter clutch assembly to the alternator rotor, again.
First it sheared the OEM bolts, now it sheared the 12.9 tensile SHCS that I replaced them with.
Question is: What should I replace them with? Is tensile stronger laterally, or is it 'brittle' and shears easier?
My bolt man sez 6 of one, .5 dozen the other.
Cheers,
G

G'day G,

Get in touch with Steve Hooker. He's a fair-dinkum metallurgist with a pile of degrees and is an ex-dragbike racer. I classify him as 'A genuine good bloke'.

His website is mtce.com.au
Phone: 0419 498 115

Blame me when you call him.

Have fun,
Mick

[ralph]

Be a real man and fit a kick starter on it lol

[Large]

Why aren't you bumpstarting the cunt of a thing?

Fit glow plugs and change the fuel, haha

[livewire]

Q:"Why aren't you bumpstarting the cunt of a thing?"
A: Have done, but my short-arse little legs are flat out running quick enough for the 3rd gear dump to stop it locking up and dragging.
And the next trick will be throwing the cunt on the ground in the process. Not a good look.

Kickstart? - I'm a gimpy legged fucked out old biker that wears a skirt ( tangled up skirt and leg also makes bumpstarting hard, too)

"Fit glow plugs and change the fuel, haha"
- Has been known to run like a tractor

And the answer is, a la Steve Hooker (thanks Mick):
Bolt man right, 6 one/ .5 dozen other, but try and get shank of bolt to go all the way to the thread, and then bolt it up,
and drill some holes in assembly and pin it.
May need diamond or cobalt drill to do so.

This thing is obviously female, my high class hooker ride. (high dollar to ride time ratio, but fucken wild ride)
Nickname for my probike was 'the filthy ho'. As in 'the filthy ho that lives in the shed and eats all my time and money'
Figured out it used to cost about $500 every time I threw a leg over it. 'Allegedly' hookers only cost $320 to do the same.
I can't be too smart, cos I used the filthy ho's motor. Silly boy.

[Hagarr]

Thats why I went Gixxer and haven't looked back.

My Kat went like fuck but Alternators, clutches etc etc too much maintenance!!

[loosebruce]

http://www.thegsresources.com/_forum/showthread.php?t=123877
Haven't tried it on my GS yet , but the logic is good.

[fimpBIKES]

how much torque is going into the bolts when you install them?
prestressing with torquing it up might be robbing you of shear strength
http://www.disc-lock.com/standard-washer

is there space to perhaps put in a pair of disclock washers under the head of the bolts?

also, is the bolt's threaded section lining up with the connection plane?
got a pic of the failed parts?

[Tony OW31]

I would imagine the shear plane would be on the threaded part of the bolt? if so is it possible to counterbore the female thread a few mill to allow the unthreaded shank of the bolt to enter? This will move the shear plane away from the threaded section of the bolt and on to the strongest part. In shear the thread acts as a stress raiser, and makes the threaded section weaker than a straight piece of bar equal to the rood diameter of the thread.
Here is a pic of what I mean.
http://www.asfphotos.com/upload/1288367029.jpg

[pappas]

A 4.6 grade bolt has a rating of 400MPa of Ultimate Tensile strength (the number 4 in the 4.6). The number 6 in the 4.6 means that the bolt will reach it's plastic point (will not go back to it's original shape) at 60% of the maximum load.

Ultimate Shear stress is about 60% of the ultimate tensile strength. So your 12.9 bolts should have 1200MPA x 0.6 = 720Mpa. But 12.9 bolts are rarely used and have to be torqued up fucking tight to work properly basically right up to it's 90% limit. You also should not re use them. I would use 8.8 bolts. Do the bolts up tight enough to not allow the full tourque of the starter motor to go through the bolts. So the majority of the tourque is counter-acted by the friction between the two surfaces in contact rather than the bolt. (if that makes sense).

[livewire]

Thank you.
I'll replace/ clean up all the nibbled on bits.
Make sure it's all clean and flat so it bolts up nice.
Think I'll use OEM, they 10.9, and tension them.
Not enough metal to use shank as dowel, and have thread
Can remember the rotor being a hard gadget to grab a hold of, whilst tensioning.
Cheers
G