Don Terrill’s Speed-Talk

Can someone enlighten me on the pros and cons of aluminum outer-ring harmonic balancers?

Yeah i would like to know if there is a down side to using one ?? Mark H.

I've never seen one.
besides being twice the size it should work ok.

cant say as im an expert on them, but have run an ATI super dampener with the aluminum shell for a lot of years. have yet to see a downside. the pro's are it weighs less, so a little less weight in the car, and a little less rotational weight bolted to the end of the crankshaft.

Some years back, David Vizard did extensive (steel) damper dyno tests on a 400 HP SBC at a high rate of acceleration. Despite having the highest inertia, the heaviest 8" one made the most power, ~ 12 HP more than the lightest one.

I'm sure lots of units are just copied from O.E.M.s or other mfgrs. dimensions but the better ones test extensively. I believe ATi will even come to your dyno, instrument the engine and build a custom unit just for your combination.

There’s aluminum hubs available too, isn’t it?

It is my understanding that the mass doing the job of dampening the harmonics is in the outer ring, not the hub?

If saving weight, maybe aluminum hub + steel shell eill do a better job rhan the other way around?

Common saying is the balancer gotta be heavy to do a better job. Circle track guys often run eithout any damper. At what level or type of racing will the L/W alu damper have it’s place?

The one I'm looking at is a Romac 6.25 with steel hub/alum ring......I'm surprised this subject hasn't come up before....

https://www.engineeringtoolbox.com/emis ... d_447.html

The heat generated needs to be rejected. Anodized aluminum has better emissivity than many common surface finishes of steel, save rust.

https://www.engineeringtoolbox.com/ther ... d_858.html

The greater thermal conductivity will transmit the heat to the surface of the aluminum more rapidly as well.

Drag race versus road race?

I have never used and aluminum hub with a steel ring. I could be way off but it seems to me the outer ring has to move left and right by some amount to do it's job. I would think that would eventually hammer out the key slot. Yes, no, maybe?

I have used aluminum hubs with no movable out ring. No harmonic capabilities though.

just thinking out loud......could the aluminum ringed balancers have been invented as a type of stopgap between full-steel versus none at all for the dirt track/sprintcar community?

The was a bunch of solid alum dampers being run in the 1980s at OCIR in fairly stout drag race engines. This was quickly followed by failed timing chains, bent valves and piston orders. They disappeared in a hurry.!!!

DCal wrote: ↑Mon Nov 04, 2019 5:41 pm The was a bunch of solid alum dampers being run in the 1980s at OCIR in fairly stout drag race engines. This was quickly followed by failed timing chains, bent valves and piston orders. They disappeared in a hurry.!!!

Yup. Moroso was one of the companies that released that junk when the rules changed and they should have been sued for all the broken junk that junk caused.

I refuse, regardless of what name is on the damper to use a damper that works off of rubber. I don't care who is using them. They have several issues. And if you can't afford for ATI to come out and custome tune a damper for you, your better off with something else.

any chance you can educate me on how ATI "tune" a damper?

shoedoos wrote: ↑Mon Nov 04, 2019 6:01 pm any chance you can educate me on how ATI "tune" a damper?

Typically with encoders on the crank measuring twist.
By varying o ring design, number and durometer, along with diameter for a given application and rpm.

^^^^^ is this done at time of balancing?