Playing with dampers

[Invectivus]

I poked around and couldn't find much specific, and not recent.

I've been playing with dampers lately, looking at doing a serpentine build. I'm looking at everything from adapters to bolt a pully onto the face of a stock 200 1V damper or slip a Taurus pulley over it, using my Aussie PowerBond PB646 EF/EL balancer, or adapting a straight six damper off a BMW. But I wanted to check to see if my understandings were correct.

The lighter a damper, the faster the engine revs but the more vibration it has to endure. Also frees a hair more HP?
Heavier is the reverse, slows revving and lessens vibration, costs HP. (Maybe. Fluidampr says efficiency frees HP and torque).
It's important that the weight be malleable (Not sure of the term?), either via viscosity (Fluid dampers) or connected to the hub by rubber (Two Element damper). Just a solid weighted assembly with no kinetic 'give' wouldn't be able to store/dissipate the tortional vibrations, right? Also, a 9 pound damper with most of the weight in the outer ring would damp more than a 9 pound damper that has a 1 pound outer ring and 8 pounds of hub and hub mounted pulley?

I saw a post by Bob about milling down part of the damper V ring and the conversation was about safely lightening the damper and it's effects, but what about heavier? How heavy can/should you go?

My stock 1V damper weighs 3lbs, 2.25oz.
The Hub/Snout alone weighs 1Lbs, 5.41oz. (I have one I pulled apart using the wrong puller).
My PowerBond serpentine damper weighs a mighty 9lbs, .22oz.
My BMW damper is 8lbs, 1.31oz. with the bare Hub that would be 9lbs, 7.72oz, plus a little more for an adapter.
My slipover Taurus pully is an even 2Lbs, a little more for an adapter, so over 5-6lbs.
My aluminum face pully is almost a pound so with a stock damper and adapter, probably close to 5lbs.

Also, I notice the stock Taurus damper is 6lbs, 2.40oz, and the ID and keyway are the same as the 200, just thicker OD (1.875" vs 1.750") and longer (by .500"). It seems possible to chuck the hub in a lathe and slim/shorten the snout for the 200 cover, then with an adapter flip the pulley to be a slip over rather than face mount?

I'm just noodling options to ease the accessibility for a serpentine for the 200ci. The Aussie damper was 188.42 shipped, which isn't bad, but 88.42 shipping just feels like a lot. I'm using the opportunity to work on my Fusion 360 skills, hoping to design my own WP pully and Alt bracket/tensioner mount.

 

[aussie7mains]

Torsional vibration damper has to be "tuned" to the crankshaft of the engine, therefore I wouldn't go deviating too far from stock, a 200ci crank wont have a lot of TV so does not need to be huge. As to the effect of acceleration, given the diameter of the damper it would have very little effect. if you compare that to the diameter of the flywheel and where the mass is, right on the outside, you get the picture. There would be NO measurable difference to torque. Inertia varies with the mass times the radias squared, so the further its is from the centre increases inertia, the weight of the hub has almost NO effect. The EF/EL damper is tuned for the longer stroke engine which has a bigger main journal, its quite different to the 200ci. Getting the polyvee belt arrangement would be the only reason to use one, and why do you want that anyway? For lower accessory loads a vee belt should be sufficient. The main reason people change to aftermarket dampers to get approval from race authorities.

 

[Invectivus]

Thanks for the feedback, that's exactly what I was looking for. Heavy dampers just didn't seem right for a 200.

As for wanting one, just good old fashioned want of something you can't get off the shelf that looks cool, even if it provides no tangible benefit.

Heck, might even be sweeter if it doesn't, like finned valve covers, breathers, and carb covers. I was looking for something to focus on while learning Fusion 360, this seemed like less of a waste of time than other things I could think of.

 

[philford]

in a perfect world the clutch disk damper and crankhaft are balanced in unison. I don't know how close the factory made them.. pulling the crank, rods, pistons, flywheel etc to balance then only makes sense during rebuilding.

lightening the flywheel l or the damper will get you across the line faster in a short race. if that's the objective, but you loose inertia. a good driver, with a standard transmission knows how to use the inertia to his advantage.

if you pull out of a turn and upshift and get a push from the inertia, that's the weight working in your advantage, With an automatic there is less driver control.

I believe there is also some complicated math involved with regards to critical speed.

I think this page (link below) describes what it is but a full understanding of how changing your damper affects the engine's critical speed, you'd have to have a good grasp on the associated engineering. Engine designers would consider all that but most backyard mechanics wouldn't be able to understand it well enough for it to be of much use.

I think most of us here can understand a bit about what critical speed is in theory, it is basically about the mechanics of natural frequencies, and their interaction with each other. excessive resonation of mechanical parts generally happens at the part's critical speed. good engineering helps to avoid damage caused by vibration.

everything has a critical speed, it relates to it's natural resonation point and there may be more than one, multiples etc and they combine in mathematically predictable ways.

often a way this is explained is by noting that a branch on a tree which blows in the wind moves at a speed relative to its length weight etc. a tree branch has its own natural frequency, so do your engine parts. the tree's natural frequency is easy to see and observe, the crankshaft and internal parts of your engine, not so much.

https://en.wikipedia.org/wiki/Critical_speed


a field of study that is closely related is vibration analysis..

Vibration - Wikipedia

en.wikipedia.org

so if you actually read all that , Yes a lot of it will be confusing, I can't understand all the complex math myself , just the basic concepts.

My point is, even if you do not follow the math, what I take from it, is that there was a lot of engineering involved in designing how heavy the crankshaft dampener should be for the application.. The idea was to reduce fatigue by dampening the vibrations..

if you go changing that haphazardly without respect to the engineering you can land anywhere, it would basically be a crap shoot, because you likely wont be able to do all the associated calculations and testing , to the degree that a well trained and educated factory engineer may.

perhpps if it is a race application where you are changing the original design a lot there are gains to be had, but for me,

Id take it in layman's terms and say , Id keep it stock and just think , "ok they knew what they were doing, so stick with it."

Id be unlikely to make any actual improvement, and It may, for example just cause the journal bearings to wear out faster than they should, or something similar.