Harmonic Dampers...Which one?

[elacruze]

I have two dampers to choose from; a genuine Fluidamper and an SFI-approved rubber ring damper.

Any opinions on which is more suitable to the 505" wedge, for long-term street driving?

[Ghoste]

The SFI rubber ring one.  Making it perfectly clear from the start that I have no experience with the fluid ones whatsoever, my secondhand anecdotal experience has been that of people telling me the fluid filled dampers slip under regular street use.  The rubber ones are frequently shot as 40 year old originals but how many years did they work fine prior to the rubber finally succumbing to age?  For the money difference, I like the rubber.

[elacruze]

Ghoste,

I'm leaning hard towards the rubber for exactly the reason you think so. The durability is unquestioned. However, two considerations; I've used Fluidampers on everything since they first became available. They always make a noticeable improvement in smoothness. I put one on my 6.2 Diesel pickup because the stock one went south, and I was awestruck at the difference. Of course, the stock one wasn't doing anything so a new-stock to Fluidamper comparison may have been less impressive.
I've not heard of Genuine Fluidampers failing, but they are 2-3 times more expensive than other brand fluid dampers and I have no input on what happens after 20,000 miles. 

My question is really kinda a shot in the dark to see if anyone has any idea about the torsional vibration characteristics of a 4.25" stroke crank vs. stock 3.75".

[Ghoste]

Around this place I wouldn't too surprised if your shot in the dark lands on target.  I'm no scientist myself but being the curious sort I'll be watching to see if someone provides an answer to your real question.

[firefighter3931]

Not a fan of fluid dampers, personally. The fluid has been known to gel up and create a severe imbalance.....my buddy has seen a few that went bad and tore up the bottom end. If you can't staticly balance it would you trust it to your engine ?

I like the Romac elastomer sfi balancers....made in Australia and carried under the Summit house brand. I'm on my second one and so far so good. The stock pullies bolt up fine with no shimming  or alignment issues like other brands.

http://www.summitracing.com/parts/SUM-B64279/




Ron

[elacruze]

I'll have to check the brand, if it's marked...doesn't look like anything I see online. It's pretty thin and has a big internal snap ring retaining the guts to the hub.

As for balancing, the concept of the fluid damper is that there is no balance required, the damper is 'theoretically' perfectly balanced and contributes only to torsional vibration damping, not to actual rotating balance. Certainly if the fluid becomes hard and can't move, both the radial balance and torsional damping would suffer.

Hm. I guess I'll just run the rubber one, the engine was built with it and ran fine and smooth. Plus I won't have to pull the other one off the other engine.

Thanks, all.

[firefighter3931]

With an internal balance build the damper is just  a harmonic "tuner" not really a "balancer" 

The thing i don't like about the fluid dampers is that their neutral balance cannot be verified due to the liquid filled center. The fluid has been known to solidify and create some issues....buddy of mine has seen this firsthand. In theory it's a great idea....cetrifugal force pushes the fluid to the outside perimeter to crate a nice even balance/harmonics damper. The only intangible is the integrity of said fluid at any given point in time. 



Ron

[greenpigs]

So Ron what do you think makes the fluid gel up? I have no plans on getting one just curious.

[firefighter3931]

So Ron what do you think makes the fluid gel up?

Not sure...heat, cold.... maybe a combination of the two through several heating/cooling cycles ? 

Extreme cold can't be good for them i would think 



Ron

[elacruze]

Here's the non-Fluidamper, made by PowerBond? Never heard of them, but it seems to be quality stuff.
http://powerbondparts.com/ SFI Race.

[inc4203]

My question is really kinda a shot in the dark to see if anyone has any idea about the torsional vibration characteristics of a 4.25" stroke crank vs. stock 3.75".
[/quote]

The longer stroke of the crankshaft will provide a larger moment arm and create more torque on the crankshaft.  This does give you more engine power, but it also creates higher torsional vibration twist amplitudes. The material of the crank also will play a factor in this.

Rubber dampers only work at a specific frequency and unless they are specifically tuned to your engine there is a risk that ANY modifications to the engine (i.e. increasing the crank stroke) will generate harmful vibration frequencies that are not the same ones the damper is tuned to for a stock engine application. viscous type dampers (fluidampr) are able to combat harmful vibrations with every engine stroke.

the silicone used in Fluidampr products is 45,000 times thicker than 30 weight motor oil.  Also, silicone is an excellant damping medium because of its tensile strength, density, and low friction properties. From the engineers at Fluidampr this silicone is able to withstand temps down to -20 degrees farenheit. Im not convinced when poeple say it gels or thickens, i beleive this is part of the engineering that makes the damper do its job.

Another important note, not to be forgotten, Fluidampr is one of few companies still 100% manufactured in the USA! 

[elacruze]

The longer stroke of the crankshaft will provide a larger moment arm and create more torque on the crankshaft.  This does give you more engine power, but it also creates higher torsional vibration twist amplitudes. The material of the crank also will play a factor in this.

Rubber dampers only work at a specific frequency and unless they are specifically tuned to your engine there is a risk that ANY modifications to the engine (i.e. increasing the crank stroke) will generate harmful vibration frequencies that are not the same ones the damper is tuned to for a stock engine application. viscous type dampers (fluidampr) are able to combat harmful vibrations with every engine stroke.

the silicone used in Fluidampr products is 45,000 times thicker than 30 weight motor oil.  Also, silicone is an excellant damping medium because of its tensile strength, density, and low friction properties. From the engineers at Fluidampr this silicone is able to withstand temps down to -20 degrees farenheit. Im not convinced when poeple say it gels or thickens, i beleive this is part of the engineering that makes the damper do its job.

Another important note, not to be forgotten, Fluidampr is one of few companies still 100% manufactured in the USA! 

That's all as I remember. I've had a Fluidamper on my 6.2 diesel pickup for about 15,000 miles and there is no sign of trouble...
But, with a good steel crank and 6200 RPM limit, what's the possibility that either one will ever lead to problems? Maybe I'm overanalysing again.

I'll have a look to see which one is easier to attach a trigger wheel to. Maybe that will give a differentiator.

[CHARGERIII]

Not sure what the rubber one has, but the fluidamper one I have sitting here has a 4 bolt pattern in it for the stock pulleys, might be able to get a trigger wheel for that pattern.  I've dealt with them in the past, if you call them up they could probably give you the bolt pattern and thread size right over the phone. 

Three reasons why I like fluidamper:

1.  Made in the USA!
2.  Nothing but quick and pleasant customer service!
3.  They WORK!

A friend of mine has an early hemi in his 48 Plymouth coupe.  He documented his first rebuild of the engine very well, even down to the bearing wear.  Ran a fluidamper on it ever since the rebuild.  16 years later, and many more harsh miles than the engine had originally, the bearings still looked almost new! 

[Troy]

Just FYI - for those of you who like to keep track of these things, inc4203 is obviously employed/affiliated with Fluidamper but, less obviously, so is CHARGERIII. Full disclosure and all that...

Posing as a "fan" has backfired on more than one vendor in the past. Honest and open discussions typically go a lot farther towards building customer loyalty. That's my free advice for the day.

Troy

[elacruze]

Just FYI - for those of you who like to keep track of these things, inc4203 is obviously employed/affiliated with Fluidamper but, less obviously, so is CHARGERIII. Full disclosure and all that...

Posing as a "fan" has backfired on more than one vendor in the past. Honest and open discussions typically go a lot farther towards building customer loyalty. That's my free advice for the day.

Troy

OK, how about it guys? Are you on the inside at Fluidamper? If so, let's get to the skinny. I'd like to know some deeper engineering (mostly about the rubber ring style, actually) such as how the amplitude affects durability/mass/moment and how stroke relates to these and frequency.

[bill440rt]

Not a fan of fluid dampers, personally. The fluid has been known to gel up and create a severe imbalance.....my buddy has seen a few that went bad and tore up the bottom end. If you can't staticly balance it would you trust it to your engine ?

I like the Romac elastomer sfi balancers....made in Australia and carried under the Summit house brand. I'm on my second one and so far so good. The stock pullies bolt up fine with no shimming  or alignment issues like other brands.

http://www.summitracing.com/parts/SUM-B64279/


Ron

I have one very similar to the one Ron has suggested. It works very well, on an engine that pulled just under 520hp on the dyno.
My  .  And thanks, Ron!