# Should I grind off the flywheel counterweights?



## brian_ (Feb 7, 2017)

Absolutely yes, remove them, if they are really balance weights (which are different from a harmonic balancer). They may be easier to machine off on a lathe than to manually grind off, and after removal the flywheel will need to be checked and corrected for balance. The weights that balance the unbalanced engine will unbalance your nicely balanced motor. They may not look big, but keep them and you're building a paint shaker. Aside from discomfort, this can kill bearings.

Balance has nothing to do with combustion. An externally balanced engine has rotating parts which are not balanced by themselves, and would shake if turned whether there's any combustion going on or not.

A "harmonic balancer" (really a torsional damper) is a different thing, and is likely harmless, but that's usually mounted on the front of the engine and I assume that you're not talking about that.

I'm a little surprised that an Escape engine would be externally balanced - I believe you, I just wasn't familiar with that combination. Can you post a photo of the flywheel, showing the counterweights?


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## reiderM (Dec 30, 2020)

I believe the two copper-looking pieces are the balance weights.

If I were to just cut/grind/sand them off, what would be the best way to ensure it's balanced? Bring it to a shop?


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## brian_ (Feb 7, 2017)

Thanks for the photo.



reiderM said:


> I believe the two copper-looking pieces are the balance weights.


Those are definitely balancing weights to be removed. Some balancing weights are attached by screws, especially with aluminum flywheels, but I can't tell how these are held on; if they are spot-welded, it might work to chisel them off.



reiderM said:


> If I were to just cut/grind/sand them off, what would be the best way to ensure it's balanced? Bring it to a shop?


Yes, an automotive machine shop should have no problem balancing the de-weighted flywheel, and I doubt that it's practical to do yourself.


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## reiderM (Dec 30, 2020)

Thank you brian.

Calling around to a bunch of machine shops and it doesn't seem like any of them do flywheel balancing.

My alternative idea is this: I cut off the protruding counterweights gradually, and just do a test spin to high RPMs with the motor out of the car (and secured in place of course, there's a lot of rotational force) until there's no noticeable vibrations. 

How does this sound?


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## reiderM (Dec 30, 2020)

I still have the old flywheel around so I whipped out the angle grinder and oscillating saw and had some fun with it.








This above picture is using a sanding attachment. Went kind of fast so I shaved off a little of the rest of it accidentally. But I left a bit of the counterweight to maybe offset it (who knows?)









This one is with a oscillating saw. Also not pretty, but the only deep cuts are where they need to be. With the saw I cut under it and ended up with this piece of metal:









I'll have access to a scientific scale tomorrow so I'm going to weight it to get an idea of how heavy it is. Because another way I could do this is to weld a few more of these on and keep them evenly spaced apart to make it balanced by addition instead of subtraction.


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## electro wrks (Mar 5, 2012)

What engine does the flywheel come off of?.


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## reiderM (Dec 30, 2020)

electro wrks said:


> What engine does the flywheel come off of?.


2.5L Mazda Duratec inline 4 cylinder. 

From a 2010 Ford Escape XLS.


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## brian_ (Feb 7, 2017)

reiderM said:


> Calling around to a bunch of machine shops and it doesn't seem like any of them do flywheel balancing.


That's unfortunate; I guess people just buy factory-balanced flywheels now. You could just buy a new flywheel which would come balanced without counterweights, but that shouldn't be necessary.



reiderM said:


> My alternative idea is this: I cut off the protruding counterweights gradually, and just do a test spin to high RPMs with the motor out of the car (and secured in place of course, there's a lot of rotational force) until there's no noticeable vibrations.


The whole counterweights will need to come off. The usual way to adjust balance is to drill small shallow goes in the heavy side to remove a bit of mass. Although that's not trivial, the more difficult task is probably determining where the heavy point is and by how much; I can see judging if there is still vibration by just trying it, but that won't tell you _where_ mass needs to be added or removed.

The removal experiments show that there are no bolts, and suggest to me that they were spot-welded.


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## reiderM (Dec 30, 2020)

It all depends on if the only counterweights are the two pieces that are visual. I can grind those off and have it decently close to balanced if that's it. But if there's an internal imbalance as well I think it's safe to say I won't be able to balance the clutch on my own.

If that's the case, I'll probably go clutchless.

I'll do some more research but assuming I won't be able to find any definitive information I might just give it a shot. The weight is far from the center (more leverage), hence why it's so small. So it would make sense for those two weights to be all there is. 

Essentially I'm operating under the assumption that if those two counterweights were not welded on, it would be a balanced flywheel.


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## brian_ (Feb 7, 2017)

reiderM said:


> It all depends on if the only counterweights are the two pieces that are visual. I can grind those off and have it decently close to balanced if that's it. But if there's an internal imbalance as well I think it's safe to say I won't be able to balance the clutch on my own.
> ...
> The weight is far from the center (more leverage), hence why it's so small. So it would make sense for those two weights to be all there is.
> 
> Essentially I'm operating under the assumption that if those two counterweights were not welded on, it would be a balanced flywheel.


I agree - the rest of the flywheel will be axially symmetric and thus balanced; any imbalance would only be the effects of removing the counterweights (grinding too far, etc) and manufacturing imperfections. The other imbalance in the engine (which these weights existed to counteract) was in the crankshaft.


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## reiderM (Dec 30, 2020)

Yep. I think as long as I take my time I can get it pretty precise, within a few grams. It won't be perfect, but it's a diy project-- nothing of the sort is.

I'm gonna sand the counterweights down the next time I get a chance. I'll keep this thread updated with some nice before and after pics. 

If when I finally get around to spinning the motor it vibrates like hell I'll probably ditch the clutch entirely like I was saying earlier. It would be nice to have as long as it works.


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## electro wrks (Mar 5, 2012)

reiderM said:


> 2.5L Mazda Duratec inline 4 cylinder.
> 
> From a 2010 Ford Escape XLS.


I recall that all inline engines are internally balanced. Only some V engines are externally balanced. Is your FW some kind of dual mass unit? If it is, with a smooth running electric motor, maybe a simple, single mass Fw would be a more reliable choice.


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## reiderM (Dec 30, 2020)

Yep it's dual mass. If there was a single mass version available for my car, I would've bought it. But I couldn't find one. The first gen escape had a single mass flywheel, but I'm not sure it would work with the 2nd gen. 

I believe that a number of Ford engines are externally balanced.


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## brian_ (Feb 7, 2017)

electro wrks said:


> I recall that all inline engines are internally balanced. Only some V engines are externally balanced.


But that's clearly not true, as this is an inline-4 which is externally balanced. I note from other online discussions that it may be externally balanced only in some applications, particularly the transverse installations (and not the longitudinal rear-drive applications). 

I agree that it is normally vee engines which are externally balanced (although the Mazda rotary is as well). I don't know why the variations in the Duratec, or why anyone would not internally balance an inline engine, since there should be lots of room for crankshaft counterweights; however, I will note that this is the largest-displacement variant of this engine family.



electro wrks said:


> Is your FW some kind of dual mass unit? If it is, with a smooth running electric motor, maybe a simple, single mass Fw would be a more reliable choice.





reiderM said:


> Yep it's dual mass. If there was a single mass version available for my car, I would've bought it. But I couldn't find one. The first gen escape had a single mass flywheel, but I'm not sure it would work with the 2nd gen.


reiderM, I'm not sure that you understand what a "dual mass flywheel" is. You have a simple single-mass flywheel; it just has some counterweights on it.

With a synchronous or brushed DC electric motor, there would be no purpose for a dual-mass flywheel (or harmonic damper, which is usually mounted on the other end of the crankshaft). Even with the cogging of a switched relucatance motor I doubt anyone uses these devices.


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## electro wrks (Mar 5, 2012)

brian_ said:


> But that's clearly not true, as this is an inline-4 which is externally balanced. I note from other online discussions that it may be externally balanced only in some applications, particularly the transverse installations (and not the longitudinal rear-drive applications).


NIce bit of circular reasoning there, brian. The stock FW appears to be a DM unit. Because of the combination of unmachined cast, forged, or other formed parts in the DM, I'm guessing balancing this FW requires the spotweld-on weights that reiderM unfortunatly ground off. The aftermarket FWs for RWD conversion appear mostly to be single mass and made to fit different starter locations, ring gear size or other changes to adapt to RWD transmissions. None appear to have weights attached, or cast-in, as would be associated with an externally balanced engine. They only have a few drilled balancing holes to balance the FW by itself.


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## reiderM (Dec 30, 2020)

brian_ said:


> reiderM, I'm not sure that you understand what a "dual mass flywheel" is. You have a simple single-mass flywheel; it just has some counterweights on it.
> 
> With a synchronous or brushed DC electric motor, there would be no purpose for a dual-mass flywheel (or harmonic damper, which is usually mounted on the other end of the crankshaft). Even with the cogging of a switched relucatance motor I doubt anyone uses these devices.


I do actually have a dual mass flywheel. The OEM flywheel was dual mass, and I bought an OEM replacement. It's frustrating, because a DMF is both less efficient and more expensive than a SMF. But I wasn't able to find a single mass replacement that I know will fit right, so I ended up just buying an OEM one.


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## reiderM (Dec 30, 2020)

electro wrks said:


> NIce bit of circular reasoning there, brian. The stock FW appears to be a DM unit. Because of the combination of unmachined cast, forged, or other formed parts in the DM, I'm guessing balancing this FW requires the spotweld-on weights that reiderM unfortunatly ground off. The aftermarket FWs for RWD conversion appear mostly to be single mass and made to fit different starter locations, ring gear size or other changes to adapt to RWD transmissions. None appear to have weights attached, or cast-in, as would be associated with an externally balanced engine. They only have a few drilled balancing holes to balance the FW by itself.


Just to clarify, I cut off the weights on the OLD flywheel which was destined for the dump. I haven't touched the new flywheel yet. 

I am a little lost on what you're suggesting though. Are you saying that if I were to cut off the balancing weights it would still not be balanced? I know that my engine is externally balanced (did some research). 

By the way, if you do manage to find a direct replacement SMF, I'll 100% jump on that. A DMF is silly for an electric motor, but it's all I could get.


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## electro wrks (Mar 5, 2012)

reiderM said:


> Just to clarify, I cut off the weights on the OLD flywheel which was destined for the dump. I haven't touched the new flywheel yet.
> 
> I am a little lost on what you're suggesting though. Are you saying that if I were to cut off the balancing weights it would still not be balanced? I know that my engine is externally balanced (did some research).
> 
> By the way, if you do manage to find a direct replacement SMF, I'll 100% jump on that. A DMF is silly for an electric motor, but it's all I could get.


Can you reference the source for the externally balanced part? I could be wrong on newer engines.


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## electro wrks (Mar 5, 2012)

Get one of these Lawn mower blade balancers at Amazon, Napa, True Value, etc.to test both FWs. Put a dab of grease on the pivot pin to minimize friction. It may be sensitive enough to show some imbalance if you can fit the FW center hole close enough to one of the diameter steps on the tool.


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## reiderM (Dec 30, 2020)

Thanks for the suggestion, I'll look into that.

Upon further research, it seems that the engine might be both internally *and *externally balanced. This is my exact engine, and the article lists it as having two internal balance shafts. It also says that the engine has a "cassette type balancer". Do you have any idea what that is? 








Here's the image of my flywheel again. You can see the two copper-like strips. Looking online at other LuK flywheels, many of them seem to have varying numbers of this exact piece welded on. Others have no visible weight. This leads me to believe that the flywheel is _not _zero balanced currently, but without the welded on weights it would be perfectly balanced. Thoughts?


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## electro wrks (Mar 5, 2012)

The cassette type balancer is a bolt-on, two shaft unit driven at twice crankshaft speed to help cancel out torsional vibration.Torsional vibrations result from the lack of power stroke overlap of less than 6(5?) cylinder engines. These engine, even if perfectly balance rotationally, still would move around from torsional vibration. For your engine, there are kits available to operate it without this unit. Balance shafts eat power and slow down acceleration. The kits are probably is just plates to block off the lubrication passages for the balance shaft bearings. The trade-off for removing the balance shafts is slightly more engine torsional vibration.

CORRECTION: The part about the power stroke overlap is correct. The balance shafts, however, are used to reduce secondary imbalances from the number of cylinders and crankshaft layout. This is explained in this video among the presenters other great videos: 



 
Just as you are convinced the copper colored weights are part of an external engine balancing system, I am convinced that they are there just to balance the flywheel alone, and not part of a external balance system! It sounds like you need more opinions on this or do a balance and/or spin test of the FWs yourself.

After market, single mass FWs are available it looks like from a quick Google search.


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## reiderM (Dec 30, 2020)

electro wrks said:


> The cassette type balancer is a bolt-on, two shaft unit driven at twice crankshaft speed to help cancel out torsional vibration.Torsional vibrations result from the lack of power stroke overlap of less than 6(5?) cylinder engines. These engine, even if perfectly balance rotationally, still would move around from torsional vibration. For your engine, there are kits available to operate it without this unit. Balance shafts eat power and slow down acceleration. The kits are probably is just plates to block off the lubrication passages for the balance shaft bearings. The trade-off for removing the balance shafts is slightly more engine torsional vibration.
> 
> Just as you are convinced the copper colored weights are part of an external engine balancing system, I am convinced that they are there just to balance the flywheel alone, and not part of a external balance system! It sounds like you need more opinions on this or do a balance and/or spin test of the FWs yourself.
> 
> After market, single mass FWs are available it looks like from a quick Google search.


Thank you. I'll have to figure out if there's any issues by just spinning it. The weights are so small (I weighed the one I cut off and it was about 8 grams, so 16 grams total) that you're probably right, and at worst any vibration should be pretty minimal.

As for the single mass flywheels, there's loads that are for the older, 1st generation Escape, since that's what they used from the factory. 2nd gen Escapes (2008-2012) use DMFs. I'm not sure if a 1st gen SMF would work in a 2nd gen.


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## electro wrks (Mar 5, 2012)

Somebody needs to confirm my math, but I get 131.5N (25.5lbf) of centripetal force with an online formula estimating 10g mass, 75 mm radius, and at 4000 RPM: Centripetal Force Calculator


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## reiderM (Dec 30, 2020)

Sounds reasonable. Would that make a noticeable vibration or oscillation? I can't imagine it would, considering the whole flywheel is 25lbs. 

But again I really don't know. Would be interested in hearing what you would expect with 25 or so lb-ft of uneven force.


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