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Will this crank clean up at 10/10?
https://www.ausmini.com/forums/viewtopic.php?f=2&t=60343		 Page 1 of 2
Author:  1018cc [ Sat Jan 16, 2010 10:01 am ]
Post subject:  Will this crank clean up at 10/10?
Hi knowledgeable mini experts,

I have a crank that I would like another (or multiple!) opinions on. I think it will clean up ok at 10/10 but would like a more informed opinion. The crank is a large journal 1100S crank (12G1505).

The following measurements are averages (from 3 measurments) from around the jounals / mains and are as follows:

Front main: 1.991"
Centre main: 1.992"
Rear main: 1.992"

Journal cyl numbers:
#4: 1.741"
#3: 1.742"
#2: 1.740"
#1: 1.740"

The reason I ask is this is the better of the two cranks I have.

Cheers, Nick
Author:  drmini in aust [ Sat Jan 16, 2010 10:29 am ]
Post subject: 
I doubt it will clean up at -.010", as the wear on the mains won't be even when it's put between centres. And 2 crankpins are at -.010" already.
You can get the machinist to try for it, but I reckon it'll be a -.020"/-.020".

<edit> you could grind the crankpins down to 1.625" (std S), and use S rods.
This gives you the option to stroke or destroke it if you want.
Author:  1018cc [ Sat Jan 16, 2010 10:36 am ]
Post subject: 
Thanks Kev :wink:
Author:  850man [ Sat Jan 16, 2010 10:40 am ]
Post subject: 
Std mains 2.005/2.001
Std B/E 1.7504/1.7509

Your crank is allready 0.10 undersize on the B/E and mains. You will need to go to 0.20. If the journals are badly scored you may need to go more, Let the crank grinder decide. You also have the option to grind the B/E down to 1.625 and use S rods, that way you can stroke/destroke to suit your requirements. But you may find that the crank is cracked and then you can use it to hold the shed door open! :lol:
Author:  drmini in aust [ Sat Jan 16, 2010 10:43 am ]
Post subject: 
Many of these old cranks are cracked, so check that first before spending time and $$.
Author:  1018cc [ Sat Jan 16, 2010 10:43 am ]
Post subject: 
On monday it is off to get crack tested so I know, at worst I've only wasted a small amount of money on a door stop :lol:

I hit one of the webs with a hammer and it rings like a bell. I have heard off of someone that it is more likely to be a good'un if it does that. I might just have to go to plan B and use the other crank if this one is stuffed :(
Author:  850man [ Sat Jan 16, 2010 10:46 am ]
Post subject: 
Yes, giving a crank a tap is a good way to tell if there cracked, if they ring there usually ok, if the "thud" then you may have a crack, but allways get them tested, along with the rods (as rods crack too!)
And it seems Kev can type faster than me!
Author:  Morris 1100 [ Sat Jan 16, 2010 12:02 pm ]
Post subject: 
850man wrote:
And it seems Kev can type faster than me!
He has had more practice. :D
Author:  1018cc [ Sat Jan 16, 2010 5:16 pm ]
Post subject: 
I've been thinking about this...can any of you give me a price on how much extra it costs to stroke one of these cranks. I'm already planning on getting it wedged as well as getting the journals and mains ground 0.020" under.
Author:  drmini in aust [ Sat Jan 16, 2010 5:52 pm ]
Post subject: 
1018cc wrote:
I've been thinking about this...can any of you give me a price on how much extra it costs to stroke one of these cranks. I'm already planning on getting it wedged as well as getting the journals and mains ground 0.020" under.

When I got mine done 12 months ago by St George Crankshafts, it was $100 extra to stroke it.
A straight regrind to next size under was $140.
To also stroke it the cost was $240 total.
Author:  gafmo [ Sat Jan 16, 2010 8:43 pm ]
Post subject: 
You just can't fault Spiro :wink: and close to home 8)
Author:  1018cc [ Sat Jan 16, 2010 9:31 pm ]
Post subject: 
Thanks guys. If it's only that much extra why not, even if it is only a couple of mm extra.

Just have to track down some S rods before I start the rebuild.
Author:  justminis [ Sun Jan 17, 2010 8:19 am ]
Post subject: 
Kev, when Spiro strokes these cranks, does he widen the journal to take the S rod or leave it std width?
Author:  drmini in aust [ Sun Jan 17, 2010 8:37 am ]
Post subject: 
Usually Spiro leaves the journal width stock, and GR narrows the S rods.
IMO widening the journal will thin the webs and could weaken the crank. But I know some have done this......
Author:  TheMiniMan [ Sun Jan 17, 2010 11:44 am ]
Post subject: 
i would also get the crank hardened if i were you

we have them ground to just "above" what we actually want to end up with, (maybe 2 or 3 thou above)

then balance them to take off any large chunks (if there is in fact any large chunks needed to come off it)

then we harden them,,, this process can bend them a tad (sometimes,,,sometimes not) & they also grow bigger in the process... we make sure the crank gets placed in the middle of the tank & leave it in there all weekend for most fullest hardening

then we grind them true to the sizes we want (often only taking a wisker off them)

& then we balance them again

so,,, all up the process is a bit lengthy,,,, & a tad more expensive then the "Average" way of doing them,,, but none of our cranks have broken doing things this way since 1969

& of course now that i`ve said that we will have a bout of broken cranks happen yeah? :-)

There is also a "Cryo" hardening treatment out now,,, i believe it doesn`t bend the cranks as much as Nitriding

& yes just narrow the "S" rods 15thou per side is fine
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