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Harmonic balancers (vibration dampers)
https://www.slantsix.org/forum/viewtopic.php?t=19559
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Author:  Bren67Cuda904 [ Thu Sep 07, 2006 7:16 pm ]
Post subject:  Harmonic balancers (vibration dampers)

Their suppose to reduce torsional vibrations in the crank. How do they work exactly. We have a heavy inner hub with a rubber wrapping it. Then theres a single v groved metal band pressed over the rubber. Is there more to the sience than "two peaces of metal separated by rubber"?
I'd like to remove the v grove band and press on one of the same weight but in the serpentine type. I though I might be able to turn one on my lathe.

Author:  slantzilla [ Thu Sep 07, 2006 9:46 pm ]
Post subject: 

The ring is not pressed on, it is bonded with the elastomer. Press the outside ring off and you have a piece of junk.

If you want an expert opinion and maybe some help with the project, call Damper Doctors. They rebuild dampers. :shock:

Author:  LUCKY13 [ Thu Sep 07, 2006 10:05 pm ]
Post subject: 

I wander just how close the Jeep 4.0 balancer would be, It has surp type groves and maybe so close it will would work with very little machining if any . They also have them in after market with crank sensor setup to remove the sensor from the flywheel. Would be nice for a IFE convertion if it could be made to fit.

I think if money was no problem you can send your balancer to ATI & they will make what you want. But the jeep balancer would be much easier & cheaper.


Jess

Author:  Joshie225 [ Thu Sep 07, 2006 11:10 pm ]
Post subject: 

Actually the easiest thing to do would be to cut down the snout of a big block Chrysler damper and groove the outer ring for a serpentine pulley. Slant 6s and big blocks share crankshaft snout dimentions. If you're going to turn high RPM and want to be safe about it then start with an SFI approved damper.

Author:  Charrlie_S [ Fri Sep 08, 2006 5:27 am ]
Post subject: 

I would be concerned about the strength of the of the elastomer bond. The stock slant six damper, only drives the alternator, from the outer diameter. All other acessories are driven from pulleys, which are bolted to the hub of the damper. Threre are aftermarket dampers, available for the 440 engine, which have a chevy bolt pattern. This would allow a large choice of pulleys, to be used, and as stated previously, the damper hub is the same size as the slant.

Author:  slantzilla [ Fri Sep 08, 2006 5:54 am ]
Post subject: 

The problem with a big block balancer is that it will stick out a lot farther forward. Add a pulley to the front and it becomes a bracketry nightmare.

Machine the belt groove off a Slant damper and make a bolt-on serpentine pulley that will go over it instead of sticking out. :shock:

Author:  Rob64GT [ Fri Sep 08, 2006 8:07 am ]
Post subject: 

I also seem remember that a few people that have used Big block balancers have broken cranks.

Author:  Super6 [ Fri Sep 08, 2006 8:16 am ]
Post subject: 

My friend and I just machined an adapter to mount a serpentine pulley to the front of the stock dampener.

Image

Image

Unfortunately, I have no idea what the crank pulley we used came from (the only piece in my serpentine setup I do not know what it was from :( ). It came from a box of pulleys at the junkyard. The pulley was virtually the same diameter as the original V-belt pulley, and was for a 6-rib belt.

We had to machine a waterpump pulley (with grooves...which is a royal pain) in order to keep the waterpump rotating the correct direction.

Image

Image

The remainder of the setup is a custom bracket for a tensioner (from a '90's dodge caravan) the alternator (from a '96 intrepid) and the power steering pump (factory pump, pulley from '96 intrepid. Press off factory V-belt pulley, pressed on serp pulley).

Image

Overall setup placed the mechanical fan in virtually the same location (fore/aft) as stock, which is the way we designed it.

-S/6

Author:  Bren67Cuda904 [ Fri Sep 08, 2006 2:01 pm ]
Post subject: 

Super6- Your system moves the altenator and moves it forward. I want to drive it from it stock loctation. This means I need a serpentine pulley in the same location as the harmonic balancers V-grove.
I could make a pulley to back wrap the V-grove which will increase its diameter and hit the timing mark. Timing mark could be moved. I could send out the balancer and have it redone in the serpentine type. This is probably not the best way do to loads on the rubber.
Maybe the grove could be machined down to gain clearance to back wrap the balancer, but this also concerns me. Doesn't there need to be a certain amount of weight in the outer band to do the dampening? Cutting it down removes alot of its weight.

Author:  rcumba [ Wed Dec 28, 2011 10:33 am ]
Post subject: 

I have a question. Does the bolt on the damper have left handed threads? It is a 66 or 67 block.

Author:  slantzilla [ Wed Dec 28, 2011 2:20 pm ]
Post subject: 

No. All right hand. :D

Author:  raycycled [ Thu Dec 29, 2011 7:09 am ]
Post subject: 

You cant swap harmonic balances willy nilly, they are set specifically to each style of 6 cylinder and one from a different 6 or 8 cylinder wont cut it, 6 cylinders area a little off balance by default, any 4 cylinder will pretty much run with no harmonic balance what so ever, you look at a 4cyl from my 1928 chev to a small 4cyl Toyota there is only a pully on the front of the motor to drive the water pump etc, but when you add 2 more cylinders it is adding half the thrown weight again, so the rotation is off set, like chopping 1 arm off a 2 blade fan it will spin to a point but eventually the wobbly will cause something to break, you can add a heavy weight to the base of the fan shaft to off set this and it will be OK, a harmonic balancer is like this. A 4 cly fires 1324 (usually) so one cylinder is firing as one is exhausting and the other 2 are half way between a compression stroke and an exhaust stroke nice and balanced, with the 6 cyl the extra 2 cylinders are approx 1/3 between strokes and there is no off set for this like the missing fan blade, so you need to counter this, hence the harmonic balancer, And as the SL6 by design is a long stroke engine a harmonic balancer from a different 6 Cyl or and 8 will not match. Sorry if this is a bit confusing not and easy thing to explain. RAY

Author:  Brussell [ Thu Dec 29, 2011 7:49 am ]
Post subject: 

Makes me think of straight 8's!

An inline 6 engine has perfect mechanical balance (primary and secondary) as the front three and rear three cylinders are in a mirror image. The crankshaft has 6 crank throws arranged 120degrees apart, this means that differences in piston speed can be neglected at any point.

And yes the dampers are supposed to reduce torsional vibration!

Primary engine balance is controlled by changing the mass on the crank shaft (at each end) and the correct radius an angle. Because of this I agree with Ray and would suggest that you should not swap balancers etc.


Bren67cuda904 - In response to your original question I believe you could make one on your lathe of correct weight etc and press it on. As long as the piece you press on is the same total weight, and the centre of mass is the same then I don't think you would have a problem.

However I am no professional, I would suggest you have someone check it out.

2cents

Author:  DusterIdiot [ Thu Dec 29, 2011 7:54 am ]
Post subject:  ??

Not sure why we are commenting on a 5 year old thread.
Quote:
You cant swap harmonic balances willy nilly, they are set specifically to each style of 6 cylinder and one from a different 6 or 8 cylinder wont cut it
Within the slant family you can swap any of the dampers willy nilly, the engine is neutrally balanced, the only drawback is the timing mark will be different depending on the year, and the cast crank balancer is slightly heavier. That being said, for a while since slants did not have SFI balancers available there once was a time when racers would have to buy a 440 balancer and live with the belt groove not lining up. (This does not work for all 440's since the 440 six pack and late cast crank big blocks were externally balanced.) Too bad the 5.2 and 5.9 magnum engines are also externally balanced otherwise that might allow for a quick cheap junkyard swap to a serpentine belt system for the slant.

-D.Idiot

Author:  Joshie225 [ Thu Dec 29, 2011 8:00 am ]
Post subject: 

Actually 5.2 Magnum truck V8s are internally balanced.

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