Front Pulleys / Torsional Vibration Dampers

[driftin jo]

Thank f&&k for a moment there i thought i ordered the wrong one!

Oh and this is what £398+VAT of Audis finest looks like (i did'nt pay that)



So if the front pulleys are a 2 part system then i take it the bottom pulleys themselves need to be balanced too otherwise the vibration damper might as well not be fitted ?

I,m sure that all the parts Audi make are balanced to a good standard to start with,but if you read all the information in this thread ie the links at in the first post you will understand that the damper HAS NOTHING TO DO WITH BALANCING, so suggesting that if it is not balanced you might as well not be fit it is just daft.
Wile getting any of the parts in you engine balanced better than they are now is hallways a good thing for you engine, even if the hole bottom end was not assembly was very well balanced it would make no difference to the function of the damper, it is a torsional vibration damper.

[HPmuirt]

So if the front pulleys are a 2 part system then i take it the bottom pulleys themselves need to be balanced too otherwise the vibration damper might as well not be fitted ?

I may have got this wrong as I am not a mechanical engineer, but from my reading of the above posts and the links articles, the reason for fitting this damper has nothing to do with smoothing vibrations caused by an imbalance of the rotating parts (crank, FW etc) but only to relieve torsional (i.e. twisting) forces and vibrations generated in the crank itself.

Calling it a vibration damper is really the problem here as everyone always assumes that the vibration is caused by a balancing issue so let's just call it a 'torsional damper' to keep reminding ourselves of its actual purpose.

It therefore sounds to me that you can bolt up what you like in terms of flywheels and clutches etc and get it all balanced, just remember to bolt on your torsional damper as well

Cheers n

Si

[driftin jo]

Si,
You understand it perfectly and have it spot on .

[Rusty]

Oh and this is what £398+VAT of Audis finest looks like (i did'nt pay that)

£398+VAT

Do we know the differences between ABY and 3B pulleys? I know that the 3B item is lighter, just wondering what was different? I would make the logical assumption that it is best to keep the pulley with the correct crank based on the information above.

Do we also have details on the 2 parts of the front pulley as there might be an option for weight reduction in the pulleys whilst retaining the the torsional damper...

Final question, does anyone knnow if there is a max RPM on the TD?

[Flat on my back]

.

Main diffs are ABY is ribbed aux belts, 3B/7A is 'V' aux belts.

HTH.

[mcandmar]

3B vs ABY pics here http://www.s2forum.com/forum/showthr...ight=3b+pulley, only difference is the alt drive belt and less weight.

[Rusty]

ABY one is a monster isn't it!!!

[Ross]

My thoughts on this... read a little into Pulley's myself, and have read the links posted at the start of the thread. I'd go down the route of lightening the stock pulley if I wanted to lose some rotational weight, I'm sure there's a pic of someone who took about 1kg off it on the forum somewhere? And change out the alternator pulley.

That said, from the experiences of others with the I5 it would appear that the crank is strong enough to take any torsional stress given to it at stock power levels. I'd imagine if it's going to break, it would do so very quickly.

Each to their own I guess, these items look damn impressive and I'd be tempted to change the alternator but I'm sticking with my dampener! Excessive torsional oscillations in my shaft sounds painful anyone seen that vid of the bridge that shakes itself to pieces when it starts oscillating at its natural frequency??

[S2central.net]

Tacoma Narrows......

http://www.youtube.com/watch?v=j-zczJXSxnw&feature=related

[Rusty]

Tacoma Narrows, one of the first things you get in any vibration based education module

[Jamo]

Tacoma Narrows, one of the first things you get in any vibration based education module

The first Tacoma Narrows Bridge opened to traffic on July 1, 1940. It collapsed four months later on November 7, 1940, at 11:00 AM (Pacific time) due to a physical phenomenon known as aeroelastic flutter caused by a 67 kilometres per hour (42 mph) wind. The bridge collapse had lasting effects on science and engineering. In many undergraduate physics texts the event is presented as an example of elementary forced resonance with the wind providing an external periodic frequency that matched the natural structural frequency (even though the real cause of the bridge's failure was aeroelastic flutter[1]). Its failure also boosted research in the field of bridge aerodynamics/aeroelastics which have themselves influenced the designs of all the world's great long-span bridges built since 1940

Does the S2 suffer aeroelastic flutter?

[Rusty]

Does the S2 suffer aeroelastic flutter?

They do, ask Doug about his experiences on a French Autoroute

[Jamo]

They do, ask Doug about his experiences on a French Autoroute

haha haven't spoken to Doug in ages!!!

[saltinot]

Calling it a vibration damper is really the problem here as everyone always assumes that the vibration is caused by a balancing issue so let's just call it a 'torsional damper' to keep reminding ourselves of its actual purpose.

The "shade tree" mechanics here in Georgia refer to them as the 'harmonic balancer' which I always thought was goofy, but it actually better defines them.

[driftin jo]

The "shade tree" mechanics here in Georgia refer to them as the 'harmonic balancer' which I always thought was goofy, but it actually better defines them.

No it doesn't as they don't actually balance anything ! They absorb torsional vibrations of the cranks resonant frequencies. Hence the proper name “Torsional vibration damper”