Balance shaft broken question

[joesevo8]

A friend of mine bought a 95 GSX with the timing all out of whack, and when we took apart the front assembly we found that the balance shaft belt was broken. We are going to pull the motor and rebuild it in a few weeks or so, my question is, once we redo the timing correctly can the balance shaft belt be left off (we are removing the shafts when we rebuild) for the time being so he can drive the car, and not hurt anything?

 

[PieEyedPiper]

I'm really tempted to just mission up to my car all stealth-like and shank my balance belt.

I'm getting a complete timing overhaul anyway in 15kmiles I can just finish the blance removal then.

Edit: http://www.dsmtuners.com/forums/showthread.php?t=185842&highlight=cut+balance+shaft+belt
HMM..

 

[DSMunknown]

Edit: http://www.dsmtuners.com/forums/showthread.php?t=185842&highlight=cut+balance+shaft+belt
HMM..

Too bad the vast majority of the photos are annoying red Xs.

 

[tkelly27]

http://www.ecanfix.com/~mdhamilton/balanceshaft.html

There's that too. If you cut the one on the oil pump, then you don't have any spinning around at all.

My car's engine is a big piece of crap anyways, so I'll be just leaving the belt off. That is as long as I don't see flecks of aluminum in the oil...

Correct me if I'm wrong, but if each shaft is running on it's own set of bearings, then all of the forces in play on a balance shaft will be there no matter what it's orientation is. The engines internals "feel" the vibrations no matter what. I dunno why, but I think of it like cats in a cardboard box. If one hits one end, and the other hits the other, they're both hitting their heads, but the box stays still. If they both hit the same end, they are still both hitting their heads on the box, but it moves really far. All you feel or see is how far the box moves, and as far as a lot of people know, inside of an engine there really are kitties hitting their heads on things. Wish I woulda taken harmonics winter term

I'd check out the data on BS bearing failure before pinning it on the out of phase shafts. Additionally, out of phase is doubling the vibrations you'll recieve. When the engine goes down, the shafts go down, and the other way around. Like monster said, it's not possible to get out of phase when it's not spinning. It's interesting that the extra vibrations could potentially cause pieces to come loose, but it's impossible to retain 1 shaft in phase and get the same vibrations as an out of phase system, and like wret suggested, it's probably inbetween not having them, and having them.

It could potentially lower the oil pressure, but then you'd just have to turn it 180*. In the above link, it's not a big enough problem for them to note it.

What benefit is there? I don't have to worry about the balance shaft belt coming off ever again. Don't have to take off the oil pan. Slightly lower reciprocating weight. Sounds good enough for me, especially since it saves me $20 on a new belt.

Lol, I really like the timing belt tattoo...

 

[wret]

Correct me if I'm wrong, but if each shaft is running on it's own set of bearings, then all of the forces in play on a balance shaft will be there no matter what it's orientation is.

I'm with DSM-onster on that one too. At first look it would seem that stopping one shaft unbalances the other but the fact is they are both way off balance to start with and their only relationship is that they spin in synch. Stopping one does not start the other vibrating out of control. The spun bearings reported in the linked post are coincidence.

I'd still like to hear from someone that had oil pressure issues. It seems that anyone who has actually run without a belt, including me, has had none. Running out of phase shafts for over a year didn't hurt anything either.

 

[t25fury]

Running one bs and not the other will cause vibration and will be out of phase since they are designed for"in phase" rotational movement.These two shafts were designed to work together,hence 2 shafts.Mitsu designed these two shafts to cancell out other engine vibrations(rotating assembly,combustion process...ect.) My own personal experience with out of phase shafts was the hydraulic line from the collector to the slave cylinder breaking off at the fitting*twice I might add,and not my fault*(slave cylinder side)due to it shaking like a guitar string and shaking my flywheel bolts lose.

 

[dsm-onster]

Yea, they cancel out the engine vibrations. And that is very understandable for a car manufacturer to do considering the market at the time. (of course a better setup like small gears that toyota does would be better).

But the purposeful off balance of each shaft contribute to canceling the shock "waves" coming from the engine. They both still rotate off balance, right? If an out of phase BS assembly fails because it is out of balance, then why doesn't it fail regardless?

The counterweight of each shaft is biased completely to one side. It center of mass is NOT the shaft center of rotation. Therefore, there is inertia subtracted out of the rotational inertia and converted to translational inertia. If you spin one around in a block, you will see that they stop alot quicker than spinning something of equal weight but more balance. That is because the total inertia stays th same but are broken in to two vectors; one acting at a tangent to the rotation (rotational inertia) and one acting perpendicular to the rotation. Thus, this translational inertia is encouraging the shaft journal side w/ the weight bias to strike the bs bearing.

Because of this same tendency, an engine crank is built w/ counter weights. And is the reason we all spend so much money and time ensuring our rotating assemblies are balanced when we plan on taking our engines beyond the rev limit. But, these buggers are spinning at TWICE the rpms of the engine. And they are purposefully and severely unbalanced. . . Just to keep our butts still.

My wife doesn't like balance shafts .

 

[SlowChild3]

Finally got my timing cover off! Man that was a job. Well I get to checking things out and my BS belt is wedge behind my auto tensioner. Seems like I got lucky... I got photos if someone wants to host... Just wondering if this could contribute to an idle problem?

 

[PieEyedPiper]

So with the belt removed, which shafts still spin and is there any chance of having any of the still rotating shafts to be "out of phase"?

 

[DarkCobraMan]

your oil pump shaft should still be spinning...when you do the BS removal kit, you get a stubby little replacement for where the BS was...as for the front one, if i remember reading the directions right when i did the BS removal you can leave the front BS in...read through the directions first...

 

[wret]

So with the belt removed, which shafts still spin and is there any chance of having any of the still rotating shafts to be "out of phase"?

The "out of phase" condition typically occurs when the rear shaft is not lined up correctly during timing belt installation. It often ends up 180° from where it should be. So, instead of canceling engine vibration, it contributes to it. You could still have the front shaft (the one with the separate belt) not spinning and the rear shaft out of phase.

Part of the rear shaft is needed to drive the oil pump so it is not completely removed. As stated by DarkCobraMan, it is replaced with an abbreviated version without counter-weighted section. The front shaft is not needed at all but removing it leaves oil holes open. These holes can be plugged by removing the bearings and reinstalling them (or new ones) with the bearing holes out of alignment with the oil holes. This is where the controversy lies. One the one hand it would seem easier to leave the shaft in place, letting shaft itself cover the oil holes. On the other hand, it has been speculated that even when left in place, the non-spinning shaft may not sufficiently block the oil passage, allowing oil to escape and lowering overall oil pressure.