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x-file
Samba Member
Joined: March 11, 2012
Posts: 50
Location: Vic. Australia
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 Posted: Tue Apr 22, 2014 5:06 pm Post subject: |
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| modok wrote: |
| Does he still think these are wiper rockers? |
Someone is totally missing the point,here.
I can see that we have an adjuster on the valve-tip,and it has a pivot at its ball-centre.
Again,I say that the angle of the adjuster at mid-swing of the rocker tells you nothing about valve-side geometry.Having the adjuster centred on the valve-tip at mid-swing also tell you nothing about valve-side geometry.Changing pushrod length will have an effect on these things,but still not change the errors in valve-side geometry.
Valve-side geometry is the relationship of the ball-centre to the rocker spindle centre.You don't even need to have a rocker fitted to the engine to establsh this,as long s you know valve-lift and the dimension from the flat on the adjuster to its ball-pivot.Get that wrong,and you get excessive side-thrust on the valve.Regardless of the angle of the adjuster,you will still get this side-thrust.
Can you see where I'm coming from?
Take a line through the centre of the ball-pivot,square to the valve stem,and see how it lines up with the rocker spindle centre at mid-lift.That will tell you a lot.When the rocker spindle is in the correct position,then you can play with pushrod length (which will have an effect on the angle of the adjuster,but won't mess up valve-side geometry.). |
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Quokka42
Samba Member
Joined: December 02, 2010
Posts: 3117
Location: Melbourne, Australia
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| Posted: Tue Apr 22, 2014 5:19 pm Post subject: |
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| x-file wrote: |
Can you see where I'm coming from?
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My guess is Nimbin - you really gotta stop smokin' that shit. The end of the adjuster is at right angles to the adjuster's axis, you just aren't getting the picture.
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x-file
Samba Member
Joined: March 11, 2012
Posts: 50
Location: Vic. Australia
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| Posted: Tue Apr 22, 2014 6:13 pm Post subject: |
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| Quokka42 wrote: |
| The end of the adjuster is at right angles to the adjuster's axis, you just aren't getting the picture. |
I can manage that,and still have terrible valve-side geometry.Thousands of people manage to have the adjuster parallel and inline/centred to the valve at mid-lift,and they still have terrible valve-side geometry.
Like I say,adjuster angle tells you nothing about valve-side geometry.I have explained what to measure,to get it right and avoid valve side-thrust. |
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Quokka42
Samba Member
Joined: December 02, 2010
Posts: 3117
Location: Melbourne, Australia
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| Posted: Tue Apr 22, 2014 6:44 pm Post subject: |
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You might as well give up and smoke some more - you're too far out of touch with reality. Setting the valve-side geometry where the adjuster is on the valve side will make the valve-side geometry correct. When the valve is at half lift, if the adjuster is in line with the valve the only thrust will be downwards. As the ball pivots, the centreline should be coincident with a right angle drawn through the centre of the shaft. The whole thing should be lubricated properly so there is no significant sideways thrust on the valve stem, instead the adjuster should slide along the top of it, though by a reduced amount from a stock adjuster.
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Matthew Tolbert
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Joined: March 27, 2004
Posts: 706
Location: Georgia
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| Posted: Tue Apr 22, 2014 9:08 pm Post subject: |
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Yes I believe I got my answer, Thanks to everyone. I have however in my opinion managed to improve on what I had previously by changing a few things. I no longer have the .120 shims but instead have reduced it to .085. Ive read about a million threads on setting up the geometry and feel I have a decent understanding of what to look for, but Im sure there is still a lot more to know. I had forgotten about a couple of things to look for and went back and started over. Im sure I have probably missed something else but for now this is what I am going with and will see how it lasts.
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Matthew Tolbert
1958 ragtop
1961 doublecab
1965 Notchback S |
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x-file
Samba Member
Joined: March 11, 2012
Posts: 50
Location: Vic. Australia
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| Posted: Wed Apr 23, 2014 5:58 am Post subject: |
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| Quokka42 wrote: |
| Setting the valve-side geometry where the adjuster is on the valve side will make the valve-side geometry correct. When the valve is at half lift, if the adjuster is in line with the valve the only thrust will be downwards. |
What you say is misleading and could cause many people to end up with excessive side-thrust,if they follow it.
I could bet you London to a brick (and I'd win a brick) that the force is not necessarily purely along the valve stem axis when the adjuster thread is pointing that way.You cannot prove this by any geometric or trigonometric logic,and I defy anyone to do so.
The only part of the adjuster that's thrusting against the elephant foot is 1/2 of the pivot ball.The direction of thrust depends on the path of the ball centre (which is part of an arc).That arc is not always or necessarily in the direction that the thread is pointing.
You can arrange the arc to be causing zero side-scrub at mid-lift (or any other amount of lift),but the angle of the adjuster thread is not what's controlling that arc.Actually mid-lift is not normally the ideal position to have zero side-scrub,and a slightly lower lift can be better at anything above 1/2 rpm.The rest of the world is quite happy with 1/3 lift or less,because of valve dynamics (acceleration rates on the opening/closing ramps of the cam).
I already contributed a 37 line post to the "Rocker Geometry" sticky,and I thought I'd explained this well enough.Many people seemed to understand it.
I think it's time to put some geometric drawings in that sticky,which might explain it better. |
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Quokka42
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Joined: December 02, 2010
Posts: 3117
Location: Melbourne, Australia
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| Posted: Wed Apr 23, 2014 2:45 pm Post subject: |
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| x-file wrote: |
You cannot prove this by any geometric or trigonometric logic,and I defy anyone to do so.
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Are you related to the person that goes by the name of VWCool by any chance?
So, we are not to accept any scientific or mathematical proof, but accept your ramblings instead?
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Matthew Tolbert
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Location: Georgia
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| Posted: Wed Apr 23, 2014 3:03 pm Post subject: |
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Wow this has went down hill fast. I just needed to know if the amount of shims I had been using was excessive or not. I have since changed that amount and feel I am on the right track with what I "think"is correct whether it is right or wrong I don't know for sure, but I think I am close.
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Matthew Tolbert
1958 ragtop
1961 doublecab
1965 Notchback S |
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Quokka42
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Joined: December 02, 2010
Posts: 3117
Location: Melbourne, Australia
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| Posted: Wed Apr 23, 2014 3:07 pm Post subject: |
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Sounds like you have it all worked out, ignore people who tell you to ignore all science, mathematics and logic and listen to them instead. About 85 thou sounds about right. If I recall correctly the flat of the ball is about 100 thou from the centre, but variations in manufacturing and where you set the adjuster end up about where you are.
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Danwvw
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Joined: July 31, 2012
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Location: Oregon Coast
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| Posted: Wed Apr 23, 2014 3:38 pm Post subject: |
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That makes sense to me X-file! Everytime I have bolted on rocker arm's I have just put enough shim under them so the valves could be adjusted. The adjustera always are very close to the full out position. When I add elephant feet or swivel feet adjusters sometimes I just grind a little off the inside of the rocker at the adjuster end if they won't back out enough.
When doing side alignment I just try to have the adjuster foot sightly off center I think it's to the left of the valve stem a little. Too much might make the valve spin too much too little might make the valve not turn enough or just turn back and forth.
I don't know though? Does this sound right?
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Quokka42
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Joined: December 02, 2010
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Location: Melbourne, Australia
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| Posted: Wed Apr 23, 2014 3:50 pm Post subject: |
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There you have it - xfile makes sense to a guy who forgets a piston and cylinder! 
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75smith
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Joined: July 09, 2011
Posts: 2275
Location: NH
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| Posted: Wed Apr 23, 2014 4:33 pm Post subject: |
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| Quokka42 wrote: |
| There you have it - xfile makes sense to a guy who forgets a piston and cylinder! |
actually what X-file is saying is correct(for the most part, his theory on thrust is a little misleading-and saying you cant solve with trig, is saying you can't solve geometry with trig)
what he is saying is the same as what I say in my third rule, but that cannot always work and must be pushed aside to ensure equal longevity of all the components
and the head looks awfully crooked to do any geometry on
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x-file
Samba Member
Joined: March 11, 2012
Posts: 50
Location: Vic. Australia
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| Posted: Wed Apr 23, 2014 7:39 pm Post subject: |
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| Quokka42 wrote: |
| So, we are not to accept any scientific or mathematical proof, but accept your ramblings instead? |
I'll accept any scientific,mathematical,geometric,trigonometric PROOF you can muster:but there is none.I've searched the internet for more than 10 years,trying to discover why people still hold onto this belief.
None of these people have applied ANY geometry or trigonometry to the path taken by an elephant foot adjuster.
Just as millions once declared the earth to be flat,thousands are claiming the force can only be in the direction of the thread (It's a cantilever,for God's sake,and it's not hinged at both ends).
Take it over to the "Rocker Geometry" sticky,and bring as much proof as you can muster.
Bring a brick,if you'd like to make a bet. |
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modok
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Joined: October 30, 2009
Posts: 26787
Location: Colorado Springs
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| Posted: Wed Apr 23, 2014 7:52 pm Post subject: |
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| ok |
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Quokka42
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Joined: December 02, 2010
Posts: 3117
Location: Melbourne, Australia
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| Posted: Wed Apr 23, 2014 7:56 pm Post subject: |
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It's not a cantilever, and if it is fixed to your valve stem or even has enough friction to rotate the valve you have gotten something horribly wrong and it's going to fail. If it is used correctly, lubrication will cause it to slide across the top of the valve, making the only significant force along the axis of the valve stem. The valve guide and spring are designed to cope with the forces induced by the offset either side of the middle.
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