Harmonic dampener to crank snout fit

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Re: Harmonic dampener to crank snout fit

Post by modok » Mon Jan 15, 2018 9:22 am

I agree. Splines would have to be a very tight fit, so you'd need a puller anyway, and it would be far more expensive.
Taper or press fit is really the way to go when you want no play at all. There is also these things
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Re: Harmonic dampener to crank snout fit

Post by induction apprentice » Mon Jan 15, 2018 6:14 pm

I'm probably wrong. But this is going to be the first time so far in years on this site I respectfully partly disagree with Modok. It may not transfer harmonics as well. and would be a problem with a 'loose fit". But if it was .0000 to .0010" I am sure it would not be any kind of a problem. I have seen this used in import crank snouts as well as aircraft applications.

With that said. I am fully prepared to be corrected as I am confident Modok trumps my knowledge.

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Re: Harmonic dampener to crank snout fit

Post by peejay » Mon Jan 15, 2018 7:09 pm

A taper fit would be awful IMO. You'd be tightening it down against the taper, not a flange. Getting the correct depth would be a serious pain.

Mazda rotary flywheels are a taper fit. The nut that holds it on is a fine thread fastener torqued to 290-360ft-lb. Makes an LS crank bolt look loose in comparison!

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Re: Harmonic dampener to crank snout fit

Post by modok » Mon Jan 15, 2018 9:21 pm

induction apprentice wrote:
Mon Jan 15, 2018 6:14 pm
I'm probably wrong. But this is going to be the first time so far in years on this site I respectfully partly disagree with Modok. It may not transfer harmonics as well. and would be a problem with a 'loose fit". But if it was .0000 to .0010" I am sure it would not be any kind of a problem. I have seen this used in import crank snouts as well as aircraft applications.

With that said. I am fully prepared to be corrected as I am confident Modok trumps my knowledge.
Depending on the actual application you may be right that splines would do well. I was imagining mainly a harmonic dampener that does not transmit more than a few HP as accessory drive, and LONG term service.
Affixing a hub to a shaft is actually a very LARGE subject.
While I don't think I am an expert in this field, just deciding where to begin I realize I could spend hours at it. How deep do we want to go?
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Re: Harmonic dampener to crank snout fit

Post by peejay » Mon Jan 15, 2018 9:43 pm

I would think that the amount of "drive" force caused by the belts is far overshadowed by the amount of torsional vibration that the damper is supposed to be absorbing.

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Re: Harmonic dampener to crank snout fit

Post by modok » Mon Jan 15, 2018 9:52 pm

Exactly. In many cases the force from trying to be a flywheel on a shaft that isn't going a constant speed will be GREATER than the force of driving the belts.
Would it rattle if it was loose? This is easy to find out.
Most cases, it will rattle.....
however lets say you had a key AND a big bolt.
a key or splines can be used to handle the shock and occasional overloads, driving forces, which might even only be in one direction, while the friction of the back of the hub forced against the timing gear with the bolt can be sufficient to keep it at zero lash for the normal loads of being a flywheel or dampener.

A loose flywheel on any reciprocating machine is a TEMPORARY condition. Even slightly loose will evolve into destruction eventually, so if this thing is acting as a flywheel I think it needs to have zero play one way or another. If one way is rusting or seizing solid, that IS a way, however for servicing that's not better. Splines can get stuck just as bad as tapers and press-fits. Maybe if you did have a splined crank it would be good to ventilate the hub with some grooves or holes on the wet end, to let oil into the splines.

The problem with a press-fit is it can only be removed and installed a few times. Each time it loses a bit of press.
Tapers largely overcome this. So can split collars. You don't have to DRAG the whole thing off the shaft.

Some things you would put on a shaft, like a pump, a fan, propeller? a long input shaft, offer more load than they do act as flywheels, or they have enough flex compared to momentum that force never reverses, so they won't rattle AND maybe even act as dampening.
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Re: Harmonic dampener to crank snout fit

Post by inline6 » Tue Jan 16, 2018 10:42 am

When I had Moldex build me a crank for a Oliver puller we did a taper nose. I copied the taper off a snowmobile crank, figured if you can transfer 130+hp through the clutches on that we can drive a fuel and oil pump without problems. Also hopefully eliminate the gulling issues we had with our past hubs using a ATI balancer during installs and tear downs.
Tractor Puller, 1959 IH 460 with 430cid NA Alcohol Inline 6 started its life as a D282

The only replacement for displacement is RPM!

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Re: Harmonic dampener to crank snout fit

Post by swampbuggy » Tue Jan 16, 2018 11:44 am

The only replacement for displacement is RPM's-------- I LOVE IT. Mark H. =D>

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