https://www.speed-talk.com/forum/viewtopic.p ... 3&start=15
265387V Large Solid Flat
Same curve as small solid flat, with more dwell at maximum velocity
25x41635 Typical Aggressive roller Short track bracket profile
2333367V Small Solid Flat typical dwell at max velocity
Mike on the little jog on Harold's flat tappet ramps:
dacaman12 wrote: ↑Thu Jul 31, 2008 7:52 amThat would be the opening lash point. Although the opening is considered "rampless", the lash point has specific values for velocity, acceleration, and jerk that Harold chooses. The jog, and even the reveral on the closing, is simply a result the choosen ramp values.SchmidtMotorWorks wrote:On the solid lifter profiles, there is a little jog before the angle changes about 80% up the first increase in acceleration, is that incidental or a feature that needs detailed control?
Here is the acceleration curve for an aggressive hyd. roller I just finished.
Jon,
All my curves are done by a 5-exponent polynomial equation, Dacaman12's cam done by an Excel spreadsheet he wrote himself.
The 'little blip' is the lash point. Later on, I have learned how to get rid of it.
Even with the'little blip', solids that I have designed have gone 100,000 miles on the street, and won all sorts of races.
I want to thank you for getting the pictures out. Let me know what I did incorrect in publishing them, so I can ease your work load next time.....
UDHarold
dacaman12 wrote: ↑Thu Jul 31, 2008 10:58 amSure!!!UDHarold wrote:How about a couple of 31* cams to show how different durations and lifts can all look alike????
Here are two accel. curves using the exact same ramp data, but very different lift and duration #s. The shorter one is 265@.050, 182@.200, and .675 lift w/ 1.7s. The longer one is 288@.050, 209@.200, and .825 lift w/ 1.7s.
I call this family the "race winning street cam" family. These are Harold's 24hrs@Daytona Ramps.
UDHarold wrote: ↑Sat Aug 02, 2008 9:20 pm Jon,
Some closing ramps do not have the acceleration reversal, but it is universally taught in various cam design courses, and as I understand it and use it, it is used to help absorb excess acceleration in the valve train on the closing side.
Remember, at the end of the closing ramp, the values are 0 lift, 0 velocity, 0 acceleration, and 0 jerk. So the closing ramp either has to be extremely long, or get rid of the Real Values somehow before closing.
The engine never notices that closing reversal in a bad way. I think many stock cams have it, or had it. I haven't looked at a stock cam for a decade or so.
Many cam designs used it also on the cam opening ramp, and the 'No-Pulse' ramp of Harvey's is a improved version of the reversal ramp.
UDHarold
UDHarold wrote: ↑Sun Aug 03, 2008 11:21 am Jon,
Revisit Harvey Crane's web-site. He recommends AGAINST using his "No-Pulse" ramp on the closing side, and he uses the acceleration-reversal closing ramp.
Constant-velocity opening or closing ramps are so "Old-School" that I have NEVER used them since I started designing in 1972. When Harvey saw my ramps in 1974, he asked me if I had been Cosworth's designer, as they used similarly-shaped opening and closing ramps, which involved constant-acceleration/constant-jerk curves.
My main curve, from the opening point to the closing point, was of the PolyDyne method, which I stopped using by 1977, when I discovered I could do everything I wanted with regular polynomial equations.
In the Spring of 1980, when I started UltraDyne, I 'invented' Multi-Segmented Polynomial' (MSP) equations, which I still use today, and they are what you call 'Spline-Fits', or 'Knots'.
All graphs shown by me are of MSP equations, or Spline-Fits........
UDHarold
It would be great if you could still see Mike Jones' curve he posted from that thread. From the conversation and looking at the acceleration curves, you can see Harold designed his ramps similarly to Harvey's "No Pulse" with very little / no ramp on the intake side and the ramp with a pulse on the closing side. Mike Jones has hinted at, and I've seen Mike Shoe confirm that this is mostly how Harold made his cams asymmetrical, and they were symmetrical from .200 on up.
Here is a profile to compare smoothing from an app Jon made vs. Blairs 4stHEAD. You can see the pulse on the opening side here: