camshaft balancing

[smeg]

Just for interest sake it would be interesting to map cam lobe loading, particularly on the opening side and see where the imbalance is positioned either end of the cam in relation to lobe load. The imbalance you are talking about is of course not going to cancel out lobe load but this is something I have often tought about but never done anything with.
It will be very interesting to see if balancing ends up helping the cam bearings. For the needles to be showing thrust in any direction there must be an alignment, journal taper or cam flex issue of some description.

I am not sure about a thrust issue it just seems to be the cage failing? I have balanced the cam with heavy metal on the rear and removing the fuel pump lobe alone brought the front down to 5 grams. Like I said, this is going to be interesting.

[smeg]

Curious in this case, is the camshaft being held from forward walk by a camshaft retainer plate? I think if a camshaft here can walk forward it would possibly tend to walk the needles forward on a roller bearing application. Not sure , just supposing?

This engine has a real nice brand name gear drive so no walking forward in this case. Don't get me going on gear drives/harmonics etc and what they do to valve trains. I once broke a new cam right behind the front cam journal and the cam company asked straight away, gear drive? Anyway this and it's sister engine have done alot of laps with the same gear drive with no problems like this before.
Maybe it was a bad batch of cam bearings??
We are changing brands of bearings to see if this helps but I am real interested in balancing cams. I am puting together a solid flat tappet high reving engine for myself and I am going to balance that cam as well, will let you guys know how far it is out before I do it.

[Dave Koehler]

Just a little tid bit. I found that a chevy cam with the 4-7 swap has considerably less imbalance.

[SchmidtMotorWorks]

EDIT! If the shaft is out of balance and it creates a vibration you don't think that would be transmitted to the valve train?

The vibration that cam imbalance causes is roughly perpendicular to the axis of rotation.
The natural frequency of the system in that axis is very low, not resonant with any valve train part.

The vibration of an imbalanced cam is compounded by the motion of the cam follower system, so if you wanted to actually balance that, you would need to balance the assembled system in the engine or similar device.

Balancing a cam alone is like balancing a 90 degree crank without bob weights; if you do it without considering the moving parts associated with it, you will make the balance of the system worse.

The vibration in a cam that needs to be worried about is torsional vibration (relative to rotation), cam balancing has nothing to do with that; as the oscilloscope test demonstrates.

[CamKing]

https://www.hotrod.com/articles/ctrp-06 ... balancing/

[In-Tech]

But but but, a magneto takes 40hp away, see how hard they are to turn? Ummmmmm my 1/4 hp distributor machine turns them 10,000 rpm

[CamKing]

EDIT! If the shaft is out of balance and it creates a vibration you don't think that would be transmitted to the valve train?

The vibration that cam imbalance causes is roughly perpendicular to the axis of rotation.
The natural frequency of the system in that axis is very low, not resonant with any valve train part.

The vibration of an imbalanced cam is compounded by the motion of the cam follower system, so if you wanted to actually balance that, you would need to balance the assembled system in the engine or similar device.

Balancing a cam alone is like balancing a 90 degree crank without bob weights; if you do it without considering the moving parts associated with it, you will make the balance of the system worse.

The vibration in a cam that needs to be worried about is torsional vibration (relative to rotation), cam balancing has nothing to do with that; as the oscilloscope test demonstrates.

I can't disagree with anything you say, but the Spin-Tron sure does.
We've been balancing cams for well over a decade now, and every time we take one to the Spin-Tron, we see improved valvetrain stability. Sometimes, not enough to matter, sometimes beyond the RPM range the engine will be running in, but it never hurts valvetrain stability.

[SchmidtMotorWorks]

For one mechanism to cause resonant vibration with another, they have to have similar frequency.
You can test this by trying to bounce a basketball with a motion that has a different frequency than the ball has, it doesn't work.

OK, let's look at vibration and the opportunity for vibration at the frequency of a rotating cam to have resonant vibration with any part in the valve train.

The part with the lowest frequency in the valve train is the valve spring, everything else is multiples higher.

Even the valve spring has a natural frequency multiples higher than cam rotation.

You can know this by watching a video of a valve spring, after valve close, the spring vibrates several cycles before it opens again. Good racing springs many more cycles.

[SchmidtMotorWorks]

I can't disagree with anything you say, but the Spin-Tron sure does.
We've been balancing cams for well over a decade now, and every time we take one to the Spin-Tron, we see improved valvetrain stability. Sometimes, not enough to matter, sometimes beyond the RPM range the engine will be running in, but it never hurts valvetrain stability.

In what measurement is stability improved? Rotational velocity?

[Walter R. Malik]

I have recently taken apart a "Yates" NASCAR cup engine from the 90's and the solid cam gear only had balance holes on one side of it and no fuel pump eccentric. This, of course was a 55mm flat tappet steel core cam.

I was going to use it again on the new roller cam but, now I am thinking it was done that way JUST for that camshaft.

[Kevin Johnson]

Components of the forces applied to a camshaft are perpendicular to the central axis causing bending (longitudinal vibration); other force components impart torsional or twisting forces along the central axis. The former would certainly be influenced by the corrections that Mike performs. Torsional forces affect the length of the torsion "spring" so there would be a coupling of the two general behaviors to a lessor or greater extent largely dependent on the surface morphology/dimensions of the camshaft.

[CamKing]

I can't disagree with anything you say, but the Spin-Tron sure does.
We've been balancing cams for well over a decade now, and every time we take one to the Spin-Tron, we see improved valvetrain stability. Sometimes, not enough to matter, sometimes beyond the RPM range the engine will be running in, but it never hurts valvetrain stability.

In what measurement is stability improved? Rotational velocity?

On the spintron, we see a reduction of valve loft and seat bounce, at high rpm's.

[SchmidtMotorWorks]

Components of the forces applied to a camshaft are perpendicular to the central axis causing bending (longitudinal vibration); other force components impart torsional or twisting forces along the central axis. The former would certainly be influenced by the corrections that Mike performs. Torsional forces affect the length of the torsion "spring" so there would be a coupling of the two general behaviors to a lessor or greater extent largely dependent on the surface morphology/dimensions of the camshaft.

Your argument that a perpendicular force (that could originate at any point along the length of the shaft) can be countered by a mass at the end of the shaft relies on the false premise that the shaft is a rigid body.

[SchmidtMotorWorks]

I can't disagree with anything you say, but the Spin-Tron sure does.
We've been balancing cams for well over a decade now, and every time we take one to the Spin-Tron, we see improved valvetrain stability. Sometimes, not enough to matter, sometimes beyond the RPM range the engine will be running in, but it never hurts valvetrain stability.

In what measurement is stability improved? Rotational velocity?

On the spintron, we see a reduction of valve loft and seat bounce, at high rpm's.

That could happen from any change in mass to the shaft.

[hoffman900]

In what measurement is stability improved? Rotational velocity?

On the spintron, we see a reduction of valve loft and seat bounce, at high rpm's.

That could happen from any change in mass to the shaft.

Jon,

Do you think a heavier shaft would reduce changes in angular velocity? I’ve read of some bandaid attempts at this via a heavier timing gear. I really don’t understand why cam quill drives haven’t caught on with the V8 stuff.