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Re: Rocker Geometry Measurements
[Re: HotRodDave]
#1524376
10/30/13 11:20 PM
10/30/13 11:20 PM
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Joined: Jan 2003
Posts: 31,045
Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 31,045
Oregon
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Quote:
Maybe some of you guys should look at that guys kit, it moves the shaft up to correct geometry and back to center the contact patch, the only compromise I see is the PR geometry will get worse, not a big deal on a BB but a SB is already bad. Of course a W2 is worstest yet and they can rev good so 
The CAD drawings I've done say the shaft has to move down to correct geometry with a high lift cam. Moving the shaft up makes things worse on every simulation that I've run.
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Re: Rocker Geometry Measurements
[Re: onig]
#1524379
10/31/13 12:16 PM
10/31/13 12:16 PM
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Joined: Nov 2003
Posts: 5,160
Texas
dannysbee
master
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master
Joined: Nov 2003
Posts: 5,160
Texas
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Andy I agree with you, with increased lift rocker shaft would have to be lowered assuming geometry is optimized before the additionial lift is added. I can also see how the rocker would need to be raised to compensate for the relocation of the contact point by adding the roller. This is what I have learned from these discussions Bottom line is there is only one location that is optimum for each type rocker, ratio and lift combination. The by product of your effort will be a rocker that is centered on the valve stem when the valve is on the seat and at full lift. What is acceptable other than being in this blue printed location I have no idea. Thanks to the OP for starting the discussion.
Getting old just means you were smarter than some and luckier than others.
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Re: Rocker Geometry Measurements
[Re: B G Racing]
#1524380
10/31/13 12:33 PM
10/31/13 12:33 PM
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Joined: Jan 2003
Posts: 32,394
Quicktree
I Win
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I Win
Joined: Jan 2003
Posts: 32,394
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Quote:
We think this post needs to start over and maybe this guy can provide us with more detailed information on how his kits can correct common issues, and after we understand how it works, then he won't have to do a sales pitch, we will be ringing his phone off the hook.
I know it would be of interest to us since we spend so much time on valvetrain corrections and end up with different fixes that are a priority for each build.
I hope he comes back and helps us and himself by educating us on his method and product.  
heck that makes to much sense
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Re: Rocker Geometry Measurements
[Re: Quicktree]
#1524381
10/31/13 01:50 PM
10/31/13 01:50 PM
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Joined: Mar 2006
Posts: 9,910
Eighty Four, PA
B G Racing
master
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master
Joined: Mar 2006
Posts: 9,910
Eighty Four, PA
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Quote:
Quote:
We think this post needs to start over and maybe this guy can provide us with more detailed information on how his kits can correct common issues, and after we understand how it works, then he won't have to do a sales pitch, we will be ringing his phone off the hook.
I know it would be of interest to us since we spend so much time on valvetrain corrections and end up with different fixes that are a priority for each build.
I hope he comes back and helps us and himself by educating us on his method and product.
heck that makes to much sense
Sorry ,Tony I was think out loud again.I keep my mind/mouth closed from now on. 
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Re: Rocker Geometry Measurements
[Re: AndyF]
#1524382
10/31/13 01:51 PM
10/31/13 01:51 PM
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Joined: Aug 2010
Posts: 40
Washington
SuperStock68Dart
member
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member
Joined: Aug 2010
Posts: 40
Washington
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Quote:
Quote:
Maybe some of you guys should look at that guys kit, it moves the shaft up to correct geometry and back to center the contact patch, the only compromise I see is the PR geometry will get worse, not a big deal on a BB but a SB is already bad. Of course a W2 is worstest yet and they can rev good so
The CAD drawings I've done say the shaft has to move down to correct geometry with a high lift cam. Moving the shaft up makes things worse on every simulation that I've run.
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Re: Rocker Geometry Measurements
[Re: AndyF]
#1524383
10/31/13 01:57 PM
10/31/13 01:57 PM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
Taking time off to work on my car
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Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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Quote:
Quote:
Maybe some of you guys should look at that guys kit, it moves the shaft up to correct geometry and back to center the contact patch, the only compromise I see is the PR geometry will get worse, not a big deal on a BB but a SB is already bad. Of course a W2 is worstest yet and they can rev good so
The CAD drawings I've done say the shaft has to move down to correct geometry with a high lift cam. Moving the shaft up makes things worse on every simulation that I've run.
FWIW, my Stage VIs required raising the shafts to get the geometry straightened out + lash caps, along w/ test-fitting a variety of rocker arms to come up w/ a combination that actually worked correctly. From what I've heard, that wasn't typical for most Stage VIs, but it's what was required with my particular set.
I think the approach required depends on the application, the particular parts used, and the rocker geometry results (e.g. Jim Miller's Mid-Lift design vs. Jesel's theory) you're looking to achieve.
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Re: Rocker Geometry Measurements
[Re: B G Racing]
#1524385
10/31/13 02:27 PM
10/31/13 02:27 PM
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Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
Performance Only
top fuel
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top fuel
Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
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Then add some .100" length valves (or longer) in the mix and there's a whole host of geometry issues created. The actual geometry itself is pretty basic. achieving it is the hard part.
machine shop owner and engine builder
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Re: Rocker Geometry Measurements
[Re: Performance Only]
#1524386
10/31/13 02:45 PM
10/31/13 02:45 PM
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Joined: Nov 2003
Posts: 5,160
Texas
dannysbee
master
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master
Joined: Nov 2003
Posts: 5,160
Texas
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Brad I would like to see an engine with one theory applied on one head and the other theory on the other. Then check the lift at the valve to see which achieves the most lift at the valve. One thing for sure the set up that has the rocker 90 degrees in relation to the valve at mid lift will have the least amount of scrub.
Getting old just means you were smarter than some and luckier than others.
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Re: Rocker Geometry Measurements
[Re: cudaman1969]
#1524390
10/31/13 05:33 PM
10/31/13 05:33 PM
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Joined: Jul 2006
Posts: 4,179
California
mickm
master
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master
Joined: Jul 2006
Posts: 4,179
California
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Quote:
I wouldn't hesitate to say these last two posts are over the heads of 95% of the readers of this discussion. Oh yeah wher's my free stuff.
not sure why that's important.
are they over my head? more or less. but i still read them and learn from them, and even if i don't completely get it, it still either expands my knowledge of the subject or enables me to understand things in a little more detail the next time i read or discuss these concepts.
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Re: Rocker Geometry Measurements
[Re: cudaman1969]
#1524394
10/31/13 06:59 PM
10/31/13 06:59 PM
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Joined: Jan 2003
Posts: 31,045
Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 31,045
Oregon
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Quote:
I wouldn't hesitate to say these last two posts are over the heads of 95% of the readers of this discussion. Oh yeah wher's my free stuff.
The concept would be easier to communicate if I took the time to post a picture. Or better yet, a short video would fully explain it in just a few frames.
I first read about the low pivot concept in a GM engine book years ago. The author didn't explain it fully but it sounded interesting. Years later I finally sat down at the CAD terminal and figured it out. The math is too complex for me so I solved the equation graphically. What you're trying to do is to solve the smallest product of load and scrub. When the valve is closed the load is small so you allow a lot of scrub. When the valve is full lift you're at max load so that is when you want zero scrub.
When you solve the equation you end up with the rocker arm perpendicular to the valve stem at about 2/3 of lift. This is below the mid-point theory which is more popular. The mid-lift approach is a simple approach that works pretty well in most applications. But if you're setting up something with 800 or 900 lbs on the nose then you might want to minimize the scrub under load.
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Re: Rocker Geometry Measurements
[Re: AndyF]
#1524395
10/31/13 07:56 PM
10/31/13 07:56 PM
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Joined: Jul 2006
Posts: 4,179
California
mickm
master
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master
Joined: Jul 2006
Posts: 4,179
California
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Quote:
The concept would be easier to communicate if I took the time to post a picture. Or better yet, a short video would fully explain it in just a few frames.
I first read about the low pivot concept in a GM engine book years ago. The author didn't explain it fully but it sounded interesting. Years later I finally sat down at the CAD terminal and figured it out. The math is too complex for me so I solved the equation graphically. What you're trying to do is to solve the smallest product of load and scrub. When the valve is closed the load is small so you allow a lot of scrub. When the valve is full lift you're at max load so that is when you want zero scrub.
When you solve the equation you end up with the rocker arm perpendicular to the valve stem at about 2/3 of lift. This is below the mid-point theory which is more popular. The mid-lift approach is a simple approach that works pretty well in most applications. But if you're setting up something with 800 or 900 lbs on the nose then you might want to minimize the scrub under load.
yup, that makes it perfectly clear! thanks!
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