crank topic, more question?

I realy liked the adjustability of yours, Jim. I built mine to accomodate Norton cranks and Yamaha singles, but I have to move the stand to different bolt holes to set it up, and them use spacers on the bearings to get it just right. You can just slide yours until the width is right for whatever crank you are working on. Pretty clever.
Ken

So Ken, what do you think the chances of my new crank breaking are. It is offset ground up to 91mm stroke .100 undersize. Jim

comnoz said:

So Ken, what do you think the chances of my new crank breaking are. It is offset ground up to 91mm stroke .100 undersize. Jim

Click to expand...

If it was for a race bike, I'd worry about it. A long time back Axtell told me that they never ground a Norton crank more than .020" because of concerns about them breaking. But the flat track crowd was notoriously hard on the engines. It could be fine for a street bike. Only one way to find out. Not to worry you, but the only one I ever had crack at a rod journal was .020" under.

FWIW, the factory routinely ground the cranks for their flat track race bikes .010" from new, just to make sure they were indexed properly. When the factory quit racing, I bought one of the flat track bikes from Little John. Among the spares was a new short stroke crank. They had turned the journals .010", cut the radius into the main shaft junction, and shot peened it. It still had stock fasteners, and no heavy metal.

The only 91 mm crank I ever ran was a Nourish, and it was standard journal size, but I didn't have any problems with it.

What are you useing for rods?

Ken

lcrken said:

comnoz said:

So Ken, what do you think the chances of my new crank breaking are. It is offset ground up to 91mm stroke .100 undersize. Jim

Click to expand...

If it was for a race bike, I'd worry about it. A long time back Axtell told me that they never ground a Norton crank more than .020" because of concerns about them breaking. But the flat track crowd was notoriously hard on the engines. It could be fine for a street bike. Only one way to find out. Not to worry you, but the only one I ever had crack at a rod journal was .020" under.

FWIW, the factory routinely ground the cranks for their flat track race bikes .010" from new, just to make sure they were indexed properly. When the factory quit racing, I bought one of the flat track bikes from Little John. Among the spares was a new short stroke crank. They had turned the journals .010", cut the radius into the main shaft junction, and shot peened it. It still had stock fasteners, and no heavy metal.

The only 91 mm crank I ever ran was a Nourish, and it was standard journal size, but I didn't have any problems with it.

What are you useing for rods?

Ken

Click to expand...

Boy, Oh Boy I like it when you guys get to talking.

I am using a pair of long Carrillos from an old racebike motor along with some short JE pistons I had left. I plan on running a large bolt from one crank cheek to the other through the hollow journal to help re-enforce the crank. Actually it will be a piece 3/4 inch bar stock- narrowed in the center and drilled and tapped on the ends for 1/2-20 flathead torx drive bolts. I am hoping applying some compression to the journals may help keep them from cracking. It is also ground with 1/8 inch radius fillets so maybe it will hang. Jim

Might consider cryogenic tempering as its what solved the crankshaft and bearing race fracturing in Norton rotary as they pumped up the heat-power levels and finally what allowed Norton go into production.

Tested on chainsaws first to find 2-3 times longer use before slack to take up and even longer for edges to keep putting out chips instead of smoking dust. I feel I'm wasting money on non frooze chains I have to put a file too more often. Norton made me feel a haft fast mechanic but getting the skill down to sharpen a chipper blade, completed my sense of competence as tool using man, eventually.

I doubt any one has tested a crank to rpms of Peel stuck throttle, WOT for count of 5. Bent crank 1/16" DS, 1/32" TS, took out non cyro'd cam tensioner and oil pump snout and wiped out inside of alternator and a cam lobe, but still pulled great to 5000/110 mph before leveling off and found crank had self correct both ends my 50%. Ken said head just fine but for the only items not frozen first, the mushroom adjusters. I need some now.

Ill add some ageement to the cryo argument. I modified a few wrenches for special applications on the Pratt and Whitney PT-6 turboprop engine. Ground down for clearance. They would break due to their thinning. We had some liquid nitrogen left over after a large re-bushing of the tail of a Shorts SD-330. I threw all of my thinned wrenches in it, and let them sit in there for over an hour. I still have those wrenches, They have not broke. Had I not froze them they would have by now.

Cryro treatment is in my plans. Could have just set it outside a couple weeks ago. 23 below. :? Jim

Thin wrenches may be fine to toss in liq. Nitrogen BUT its a big No NO to do that to metals with some bulk to them d/t thermal shock distortions. Last few decades only slow vapor cooling of 1'F per min. is used. Its not a DIY process unless you can accomadate the control temp changes. There is also a 12 hr heating rise to 350'F then slow cool to room temp before done for use.

ONE warning you must dissassemble any dissimilar metals of the difference in thermal contraction can destroy stuff. I forgot about the steel valve seats in Al head - which got pushed clear out of head so new one needed - which delayed head beging used a year- which lead to me putting on standard head and scabbed on lipped and rough manifold to head port - which lead to surprise boost in power repsonse - which lead to me able to dice it up with hot sports bikes no problemo up to 90 mph acceleration which and almost unbellievable top end to me and my new riding players.

I do major fasteners too, and chain. May do spark plugs and tires and belts, brake rotors/pads to see what that does or don't. For sure axles. I even do Al even though its non ferric, the low temps really compresses the alloy short a like all over inside and out shot peening.