camshaft balancing

[smeg]

I know this has been talked about before and there are differing theories on it but I have just had a problem that might have something to do with this.

358 cube 700 hp dirt engine, solid roller, roller bearing camshaft, back for the yearly freshen. Noticed that the bearing needles look like they have been pushing forward and damaged the front cage washer/spacer in the bearing. No damage to the cam journals at all, but the bearings have nearly failed.
The bearings were installed square in the bore with a tool that pulls them in square, so alighnment was not an issue. All the other parts in the engine are fine as per normal for the freshen, we always replace lifters, cam bearings etc each season and springs every 2 seasons if they test ok, no other problems at all.
I thought about camshaft balance, so I put in the machine and guess what, @ .700" radius, 34 grams out at the front and 29 grams at the rear journal.
I was shocked at how much it was out, I am thinking that it cannot be helping anything so I am going to balance it.
It needs the fuel pump lobe ground off at the front and we are putting heavy metal in the rear journal.
We have dynoed this engine multiple times so it will be interesting to see if there are any changes in the engine when we test again. If there are any I will let you all know.

[xanadu]

I have always been curious about balancing camshafts with heavy metal, I have never found any literature about it other than Mike Jones method
on a counterweight on the front of the camshaft? Would you make Mallory thread in slugs and scew into the camshaft where necessary?
Very interested in this.

[cjperformance]

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.

[Newold1]

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?

[midnightbluS10]

I have always been curious about balancing camshafts with heavy metal, I have never found any literature about it other than Mike Jones method
on a counterweight on the front of the camshaft? Would you make Mallory thread in slugs and scew into the camshaft where necessary?
Very interested in this.

There's a couple of articles online. One from Ted Eaton and another from Randy Neal in the first 3 or 4 results on Google. Give them a read, as they address things other than the external balancing that Mike does.


https://theshopmag.com/features/camshaf ... ing-part-1

http://www.eatonbalancing.com/2012/12/0 ... balancing/

[modok]

Calculate the force of the imbalance at redline
how does that compare to the force the lifters are exerting on it?

Usually, the imbalance is trivial

[digger]

Calculate the force of the imbalance at redline
how does that compare to the force the lifters are exerting on it?

Usually, the imbalance is trivial

About 20lb at 3500rpm cam speed

[GARY C]

If it reduces valve train harmonics it can't be a bad thing... I think.

[SchmidtMotorWorks]

If it reduces valve train harmonics it can't be a bad thing... I think.

What does adding a pendulum to do valve train harmonics that would differ from adding a cylindrical mass in the same place?

Hint, to have an affect on valve train harmonics, the mass would have to accelerate and decelerate the cam at a frequency that coincidences with a vibration frequency in the system.

Does the mass on the end of a cam cause it to accelerate or decelerate with a frequency?

[xanadu]

I have always been curious about balancing camshafts with heavy metal, I have never found any literature about it other than Mike Jones method
on a counterweight on the front of the camshaft? Would you make Mallory thread in slugs and scew into the camshaft where necessary?
Very interested in this.

There's a couple of articles online. One from Ted Eaton and another from Randy Neal in the first 3 or 4 results on Google. Give them a read, as they address things other than the external balancing that Mike does.


https://theshopmag.com/features/camshaf ... ing-part-1

http://www.eatonbalancing.com/2012/12/0 ... balancing/

Thank you for that.

[SchmidtMotorWorks]

There's a couple of articles online. One from Ted Eaton and another from Randy Neal in the first 3 or 4 results on Google. Give them a read, as they address things other than the external balancing that Mike does.

https://theshopmag.com/features/camshaf ... ing-part-1

http://www.eatonbalancing.com/2012/12/0 ... balancing/

Unfortunately they are full of nonsense.

[GARY C]

If it reduces valve train harmonics it can't be a bad thing... I think.

What does adding a pendulum to do valve train harmonics that would differ from adding a cylindrical mass in the same place?

Hint, to have an affect on valve train harmonics, the mass would have to accelerate and decelerate the cam at a frequency that coincidences with a vibration frequency in the system.

Does the mass on the end of a cam cause it to accelerate or decelerate with a frequency?

Note the opening word... "If"

[SchmidtMotorWorks]

If it reduces valve train harmonics it can't be a bad thing... I think.

What does adding a pendulum to do valve train harmonics that would differ from adding a cylindrical mass in the same place?

Hint, to have an affect on valve train harmonics, the mass would have to accelerate and decelerate the cam at a frequency that coincidences with a vibration frequency in the system.

Does the mass on the end of a cam cause it to accelerate or decelerate with a frequency?

Note the opening word... "If"

I did, you are correct to wonder.

The question is easily answered by driving a shaft with a DC motor and using an oscilloscope to measure the voltage change as a measure of resistance (or acceleration/deceleration).
Touch it with a toothpick while it is spinning and adjust the scope until it can pick-up that fine resistance.

Now, stop it and attach a mass that puts it out of balance and run the test again.
The scope reading will still be stable because an imbalance does not accelerate or decelerate the rotation of the shaft.
Without acceleration in cycles, there is no vibration.

[GARY C]

What does adding a pendulum to do valve train harmonics that would differ from adding a cylindrical mass in the same place?

Hint, to have an affect on valve train harmonics, the mass would have to accelerate and decelerate the cam at a frequency that coincidences with a vibration frequency in the system.

Does the mass on the end of a cam cause it to accelerate or decelerate with a frequency?

Note the opening word... "If"

I did, you are correct to wonder.

The question is easily answered by driving a shaft with a DC motor and using an oscilloscope to measure the voltage change as a measure of resistance (or acceleration/deceleration).
Touch it with a toothpick while it is spinning and adjust the scope until it can pick-up that fine resistance.

Now, stop it and attach a mass that puts it out of balance and run the test again.
The scope reading will still be stable because an imbalance does not accelerate or decelerate the rotation of the shaft.
Without acceleration in cycles, there is no vibration.

I personally would not take the time to do it although if there is a good way to test the effects then someone needs to do it.

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?

[midnightbluS10]

There's a couple of articles online. One from Ted Eaton and another from Randy Neal in the first 3 or 4 results on Google. Give them a read, as they address things other than the external balancing that Mike does.

https://theshopmag.com/features/camshaf ... ing-part-1

http://www.eatonbalancing.com/2012/12/0 ... balancing/

Unfortunately they are full of nonsense.

NEVER claimed they weren't. I just reposted the links.


So you've done camshaft balancing? Enlighten us.