Camshaft lobe design by Billy Godbold

[hoffman900]

I always thought a graphic style program where you can manipulate the acceleration curve (or any of the curves) at any point would be the most powerful, and obviously it would integrate or derive the other curves, and then have to work backwards. Obviously you would have to know your limits for a given valvetrain and grinding set up, but it would give you the most control over the curve. I would be looking at some of the very powerful graphics programs that high end graphic designers and 3d modelers use.

[digger]

Anyone that’s been on these forums a long while would not have learnt anything from this video as less tech in it than on threads here gone past. The target audience is the less technically minded.

[1980RS]

Best guy ever was Scooter Brothers at Comp Cams. One of most helpful people I have ever dealt with.

[David Redszus]

Here you go.

https://www.physicscurriculum.com/inter ... %20screen.

Nice! Thanks,


IMG-20211130-WA0025.jpeg

The cam measurement set up shown in the pix is incorrect. It will produce false readings and will not reflect the proper lift profile.

The dial indicator cannot be a point; it must be either a roller tip, curved tip (mushroom shape), or a flat surface.

[SchmidtMotorWorks]

I think the Blair program tried to be an all in one program and does this as well. I suspect the GT packages to be beyond that.

I wanted to buy the Blair software to see how well it works, but I was told it's no longer for sale.

It operates on the principle of shaping the acceleration curve, then the software adjusts the shape to make the velocity and lift equal 0.0 at the end.
The method is really the only way to go if you want precise control of every detail of the acceleration curve.

The only thing I see negative about it is the curve math they used to model the acceleration curve is some kind of spline, but not a B-spline so the shaping control is not as nice as a good CAD system is. Still, you can make it do what you want for sure.
The computer power of a PC when that software was written could not have found the t of x fast enough to be interactive so they had to make use of some kind of spline that was not parametric (the x input is the same as a the x output). None of those spline codes are pleasant to design with, but they do eventually work.

[SchmidtMotorWorks]

I think the Blair program tried to be an all in one program and does this as well. I suspect the GT packages to be beyond that.

I wanted to buy the Blair software to see how well it works, but I was told it's no longer for sale.

Mike,
About 4 or 5 years ago I had a thread on here about trying to generate a cam for a Pontiac to match Blair's STA targets. Some one on here was able to generate some S96 files and sent them to me. When I have sometime I will see if I can find the thread and who it was. I am not sure but I believe they used Blair's software.

Stan

The point many seem to have missed on that thread was it is the principle of benchmarking dimensions that worked.
Of course it would not make sense to follow the values that Blair had because he compiled them from a strange collection of examples.

[SchmidtMotorWorks]

As Mike said, what we really care about is the valve lift curve, not the cam lift curve. In direct acting tappet valve trains (1 to 1 ratio), they are the same. With rocker followers, they are not. Neither are rocker ratios constant with lift.

In some applications, we can obtain all the information we need from cam data. In other systems, the cams must be installed with push rods, rockers, etc, in order to measure valve lift.

But even then, we only have static valve motion data. The dynamic conditions of a running engine can produce an unexpected valve lift curve; including float and bounce.

Both lobe and motion data are needed.
The lobe data enables computation of contact stress and tribology.

[SchmidtMotorWorks]

The most important thing to know about specing a cam though is 128.

[bob460]

The most important thing to know about specing a cam though is 128.

Another youtube video coming................

[SchmidtMotorWorks]

Billy does make a valid point about soft entry to the acceleration pulse (paraphrasing).
Especially on pushrod engines with modern/stiffer valvetrains.

[hoffman900]

Billy does make a valid point about soft entry to the acceleration pulse (paraphrasing).
Especially on pushrod engines with modern/stiffer valvetrains.

I’ll have to find it, but he has said elsewhere that this came about when they flipped an old cam designer’s lobe around and found it worked better. He also referred to that cam designer as the “John Daly” of designers in terms of his designs. You can take a guess who he is talking about.

https://youtu.be/whmOxK4XDYQ 39:30 he’s been on a few podcasts and this was the first one he was on and he gave up some of the best info in this one as well. Billy is a smart guy, but he’s only going to give up as much as the interviewers are capable of understanding, and most of them aren’t very sophisticated. I want to say somewhere else he let up it was one of the Gliddens they figured this out with.

[SchmidtMotorWorks]

I’ll have to find it, but he has said elsewhere that this came about when they flipped an old cam designer’s lobe around and found it worked better. He also referred to that cam designer as the “John Daly” of designers in terms of his designs. You can take a guess who he is talking about.

I have heard that story many times from other people too.

The reasoning applies to any mechanism with flexible components.

Elevators are one of the places where well engineered motion can be felt.
In some building, you can go 20 floors and it feels like going 2 floors in another building.

Another fitting analogy is the difference between tapping something with a hard or soft hammer.

[juuhanaa]

I’ll have to find it, but he has said elsewhere that this came about when they flipped an old cam designer’s lobe around and found it worked better. He also referred to that cam designer as the “John Daly” of designers in terms of his designs. You can take a guess who he is talking about.

I have heard that story many times from other people too.

The reasoning applies to any mechanism with flexible components.

Elevators are one of the places where well engineered motion can be felt.
In some building, you can go 20 floors and it feels like going 2 floors in another building.

Another fitting analogy is the difference between tapping something with a hard or soft hammer.

I dont understand why we have plastic hammers in my daily job. I often take a copper one, and i hold it from end of the stem. My colleagues think im nut.

[Tom68]

Anyone that’s been on these forums a long while would not have learnt anything from this video as less tech in it than on threads here gone past. The target audience is the less technically minded.

It's more a history of Horsepower gain evolving, it's not just smarter head valve combustion chamber flow, it's also availability of components to do the job. Back in the day Isky gold stripe springs were a godsend for endurance motors. People like Grumpy Jenkins had decades before been working their own miracles, but not many could buy into that excellent engineering, we just read it and dreamed.

A suspension equivalent was deCarbon dampers, once Bilstein offered the technology things moved forward in leaps and bounds.

[englertracing]

NASCAR was the most valve spring challenging racing series of the world. The world leading valve spring companies (PAC, PSI, COMP, ...) refined here there knowhow and material. We have no racing series here in Europe which was more challenging as that application: huge valvetrain mass, lacking stiffness, amazing lift values and still 10,000 rpm covered by a spring for very challenging application with a lot of redline near operation, where 250 rpm more could change the field.

Well excluding durability NHRA pro stocks were using something like 1.1"-1.2" valve lift and turning over 11000rpm, limited to 10500 now.