crank locking bolt and crank twist

Enginehardware · Feb 3, 2009

Krisbrumm said:
bushmechanic said:

I didn't know I had a crank locking bolt so I made a tool to hold the flywheel 3" pipe ( i think) with 2 tangs to go in the holes in the flywheel.

[/quote

I've got similar tool to hold the flywheel.Cause I'm lucky to upgrade my shop with precision lathe, I made such like ring which comes into the flywheel, around inside there are lots of "dowels".They lock my flywheel.I'm using them when tighten with torqe wrenh.To undo the nut, I use air gun and holding the flywheel with hand.It doesn't spin with that way.That sound quite safe,Itn't it?]

Click to expand...

Why dont you just place a screwdriver between the sprockets on transmission side, the nut is not welded in place so it isnt that hard. This works also.

I like the tool, but i dont see the use, just send a drawing so i can make one...........

//Thomas

on-one-wheel · Feb 3, 2009

a bit off topic but i used an oil filter wrench from halfords once to undo the crank nut on the flywheel of my old 916. wrapped some rubber around it and placed metal strap filter wrench on it. When it came to put the nut back on we used same method and we hit 180Nm before the wrench snapped in half haha. i love cowboy work

bushmechanic · Feb 3, 2009

Why dont you just place a screwdriver between the sprockets on transmission side, the nut is not welded in place so it isnt that hard. This works also.

I like the tool, but i dont see the use, just send a drawing so i can make one...........

thomas if the pin is not welded then the possibility exsists that the crank will twist on the pin if you lock one side and give tourque to the other

based on one 550 crank I tested its true

dunno if that is a good experiment only one test.

I got my crank to 0.0025mm maximum runout so not real keen on stuffing that up if its at all possible.

regards
Bushie

Enginehardware · Feb 4, 2009

bushmechanic said:
Why dont you just place a screwdriver between the sprockets on transmission side, the nut is not welded in place so it isnt that hard. This works also.

I like the tool, but i dont see the use, just send a drawing so i can make one...........

Click to expand...

thomas if the pin is not welded then the possibility exsists that the crank will twist on the pin if you lock one side and give tourque to the other

based on one 550 crank I tested its true dunno if that is a good experiment only one test.

I got my crank to 0.0025mm maximum runout so not real keen on stuffing that up if its at all possible.

regards
Bushie

Well iÃ‚Â´m not sure you will get the crank to twist when you apply force in one end and lock the other, its in the same line and supported by the bearings.
Yes if you lock the piston and apply force on either tranmission side or flywheel then it will maybee twist easier.
Reason is that the main bearings should hold against this twist, but there is always a bit of freeplay in all these parts.
But its alot of force to press the big end together and sometimes i think how can this twist, but it does.

//Thomas

Neil_E. · Feb 6, 2009

Bushie is correct on his crank twisting comments. You need to support each side independently when torquing up the respective nuts. Thus a gear segment piece for the left side and a flywheel holder for the right side. All this care in assembly is academic though because the crank wheels move so easily on the crankpin. Welding is great if the pin doesn't creep during welding. The extra crank width needed for the balancer moves the bearings out enough that crank ridgidity is critical. The small diameter crank pin is the biggest flaw in the Berg engine.

Taffy · Feb 6, 2009

you can't have a bigger big end pin and a shorter stroke half the time because the pin is touching the crank journal when pressing it in. have you seen the 450 big end pin? it's on the journal.

if the journal didn't have a 360d circle the inner race of the main would feel the difference straight away and the bearing would collapse....!

regards

Taffy

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