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Topic: Sierra B6 lock - adjustment problem |
mickd
From:
london,england
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Posted 26 Mar 2003 10:25 am |
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Whenever I adjust the LKR (which lowers 4& on my Sierra Session U12, I have trouble readjusting the B6 "lock" so that it holds tight and doesn't let 4&8 go sharp. Here's a picture of my lock.
Can anyone tell me what the mystery bolts do ?
Does anyone ever adjust the nut ?
My cam is contacting the post off-centre. How do I get the cam to hit the post full square ?
How do you go about adjusting the cam so that it holds the change tight ?
[This message was edited by mickd on 26 March 2003 at 10:26 AM.] |
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Michael Johnstone
From:
Sylmar,Ca. USA
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Posted 27 Mar 2003 9:37 am
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OK here goes....The mystery bolts are just set screws to keep the large nut from turning on the large bolt it is threaded onto. What you want to do is make sure that large nut is tightened down enough so that the whole unit is snug to the mounting plate and turns without wobbling but is not too tight so as to impede the turning motion of the locking lever.One of the set screws also does double duty as a stop.I suspect that unless someone has messed with it,the large nut and its set screws are probably set correctly since once set up at the factory they tend to stay put. As far as getting the delrin cam into the right position elliptically,there is an allen socket screw pinning the cam to the end of the large bolt which can be loosened and the cam can be rotated to the correct angle. This will take some fiddling(but quite possibly the ONLY fiddling you'll need to do)but what you want is for the cam to be ever so slightly past top dead center when it comes to a stop.The problem you will find is once it's IN the right position,tightening down the screw that holds it in position will actually tend to turn it OUT of the correct position - this can be maddening but you will finally get it right.The other adjustment you have available is that the entire unit can be slid back and forth along the large slot across the back of the guitar by loosening the 2 screws that pin the two plates together that hold it in the slot.What I do when adjusting my unit is (in this order)1. Make sure the large nut is snug and not wobbly as mentioned above. 2. adjust the cam to stop at slightly past top dead center. and 3. Move(only if nessesary)the entire unit(usually only a miniscule amount)to get the knee lever mechanism to bottom out at exactly Eb. At the end of the day,what you want is to be able to hold the E-Eb lever firmly in,lock the lever and not hear the Eb go flatter and/or not hear the Eb drift sharp as you release knee pressure letting the lock take over. I spent a whole evening fiddling with mine then played a couple gigs - wasen't satisfied with it - fiddled for another long evening and finally got it right and haven't touched it now in over 5 years. Hope ths technical diatribe makes sense. Good luck in your fiddling! You've got a fine guitar there.
-MJ- |
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mickd
From:
london,england
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Posted 27 Mar 2003 11:30 am
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Michael
thanks for the reply.
You've confirmed pretty much what my experience up to now has told me - that its a bit hit & miss to get it right but once its ok it stays that way. I hadn't realised the 'double duty' function of the bolt - don't understand that but I'll take another look underneath & maybe the penny will drop.
Mick |
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mickd
From:
london,england
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Posted 29 Mar 2003 5:38 pm
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Michael
I see what you mean now about the stop.
I have just spent hours trying to adjust the lock & still can't get it right 
Could you explain what you mean by "adjust the cam to stop at slightly past top dead center" ?
Is this adjustment made when the lock is in 'locked' position ? If I'm sitting under the guitar looking up at the cam from the 'inside', what position is the allen-key socket 'hole' in at this point ? (if 12 oclock is the hole at the top of the guitar next to the rail, for example).
I know I'm being thick here, but I am lost
Mick |
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Michael Johnstone
From:
Sylmar,Ca. USA
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Posted 29 Mar 2003 8:10 pm
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| No you can't make the adjustment when it is locked.You have to adjust it in its relaxed(unlocked)position and then try it - if it's not right,you have to unlock it,re-adust it a little,tighten it down and try locking it etc,etc. What I meant by top dead center was an analogy to adjusting overhead cams and valve clearances on a car - anybody remember those days?Anyhow,the delrin cam is actually a round part with an off center hole in it thru which it is mounted to the large bolt that acts as tha axel to the whole device.Loosening,swiveling and re-tightening the cam is the key adjustment to this device.Look at how the whole thing works: By turning the locking lever,the cam comes in contact with a post that pushes the knee lever to its limit.If it gets to its stop and the cam is adjusted shy of top dead center,it's not gonna stay locked.If it's too far past top dead center when the set screw gets to its stop,the cam will have traveled past its high point and will have started receding back down as the elipse of the cam passes its zenith (top dead center). So adjust the cam so that when the locking lever is activated and the set screw reaches its stop,the cam is ever so slightly past fully extended and engaged against the post.That way,you will pick up just enough friction between the cam and the post to stay locked. |
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mickd
From:
london,england
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Posted 30 Mar 2003 12:01 pm
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| thanks - I'll try again .. |
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