chain chatter/jump on trailing edge of bar

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stihl_lyfe

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Hey folks, been running a couple of different bar and chain setups for the slabs I've been cutting with the 660. 1x 32" sugi hara with 3/8" E&S skip chain (10deg) that runs and cuts like a dream, the other a 42" sugi hara with .404 Oregon skip (10deg) that has been workable but a chore to run by comparison. Obviously the bigger bar and chain take a lot more to drive but not convinced power is the issue, as despite trying a range of tensions on the 42" the chain on the trailing side always wants to lift and jump out of the bar groove mid bar when the RPMs come up. This means I can never really run the 660 in its powerband with that combo - again it has the power to do it but the chain starts jumping at the same speed that the 3/8" setup is just getting started.

Anyway, thinking I will ditch the .404 setup and put a 3/8 sprocket on the long bar, but interested to know what is not going right here. Slabs so far have mostly been macrocarpa (softwood cypress), pic for your viewing pleasure

IMG_20200127_152603.jpg
 
Does it chatter at higher rpms even before you start your cut, or only when the chain is actually working? Also at the very beginning of a cut , before the trailing edge enters the kerf, does it chatter or not? If it doesn't chatter under those conditions, try increasing your filing angle slightly to increase the width of the kerf.
 
Beautiful wood, but I want to know about your truck! It looks like a FJ40 Land Cruiser but with a shorter cab and a longer frame for the flatbed...is that custom, or a Toyota version we didn’t see in the US, or what? That is one of the coolest flatbeds I’ve ever seen! What a killer wood hauler!
 
Does it chatter at higher rpms even before you start your cut, or only when the chain is actually working? Also at the very beginning of a cut , before the trailing edge enters the kerf, does it chatter or not? If it doesn't chatter under those conditions, try increasing your filing angle slightly to increase the width of the kerf.

It doesn't do it free revving, and can't recall when it only has the leading edge in the cut but I suspect not. So filing for less of a flat tooth might help? If so could give that a crack...

Beautiful wood, but I want to know about your truck! It looks like a FJ40 Land Cruiser but with a shorter cab and a longer frame for the flatbed...is that custom, or a Toyota version we didn’t see in the US, or what? That is one of the coolest flatbeds I’ve ever seen! What a killer wood hauler!

It is a BJ45, which I believe you guys got but only in wellside form (and minus the diesel B motor of course). Most 45 series trucks here are flat decks, as most were bought for doing work on farms etc. Is pretty versatile for sure, not very fast on the open road but can haul all sorts of stuff - and gets lots of thumbs up! Was a bit of fun yesterday actually doing those blackwoods, trees were at the bottom of a gully on a farm so after a rain it was quite tricky winding back up the clay track at the end of the day - many modern trucks would have been stuck down there I think

v4PgZVp.jpg
 
It doesn't do it free revving, and can't recall when it only has the leading edge in the cut but I suspect not. So filing for less of a flat tooth might help? If so could give that a crack...



It is a BJ45, which I believe you guys got but only in wellside form (and minus the diesel B motor of course). Most 45 series trucks here are flat decks, as most were bought for doing work on farms etc. Is pretty versatile for sure, not very fast on the open road but can haul all sorts of stuff - and gets lots of thumbs up! Was a bit of fun yesterday actually doing those blackwoods, trees were at the bottom of a gully on a farm so after a rain it was quite tricky winding back up the clay track at the end of the day - many modern trucks would have been stuck down there I think

View attachment 830464
The greater the angle the farther the tooth gets into the wood before braking the chip out, which makes the kerf wider. When ripping it may take a little more change to get a wider kerf than it does in a cross cut because the tooth doesn't go very deep before breaking out under any conditions when ripping.
That is certainly beautiful wood. You've done a really nice job with your milling. Very cool truck!
 
Agreed, thanks for the extra truck info. So what kind of diesel is in there? My understanding is that the FJ40 we had in the US used a carbureted inline six that evolved from a design licensed from Chevy sixes...?

I will now stop derailing your milling
thread with truck questions!
 
Nah truck questions are cool, enjoy a good cruiser chat. The diesel is the 3.4L 3B - is a 4 cylinder also used in later model landcruisers, often in turboed form. It's very slow, but have been rumoured to turn over a million kms without a rebuild and mine needs no topups between 10k km oil changes which is saying something at 40yrs old. I do want for a bit more power though, may swap out the driveline for something later model one day when I can get other car projects off my plate...
 
So a bit of an update here in case I can help some other ms660 owner wondering whether to go 3/8s or .404...

So I got gifted a redwood to mill and needed the 42" bar to get it done - which finally meant I got around to changing the nose sprocket to 3/8 and I bought some new Stihl 3653 36rmx ripping chain to suit. Wow what a difference - bar is now performing like it should, no jumping/labouring in the cut and easily sits in the powerband. Admittedly the sequoia is very soft but still plenty of power to spare and I think would perform happily in hardwood also. So my advice given the rpm characteristics of the 660 the .404 is not worth contemplating at that length, at least with the sugi hara bars that aren't very fat in the belly and thus seem to struggle to hold on to the .404 at higher rpm (and inability to really crank the tension on the 660 probably contributes also).

Pic of beautiful redwood for yer viewing pleasure

IMG_20200905_211738.jpg
IMG_20200905_211622.jpg
 
Hey folks, been running a couple of different bar and chain setups for the slabs I've been cutting with the 660. 1x 32" sugi hara with 3/8" E&S skip chain (10deg) that runs and cuts like a dream, the other a 42" sugi hara with .404 Oregon skip (10deg) that has been workable but a chore to run by comparison. Obviously the bigger bar and chain take a lot more to drive but not convinced power is the issue, as despite trying a range of tensions on the 42" the chain on the trailing side always wants to lift and jump out of the bar groove mid bar when the RPMs come up. This means I can never really run the 660 in its powerband with that combo - again it has the power to do it but the chain starts jumping at the same speed that the 3/8" setup is just getting started. Anyway, thinking I will ditch the .404 setup and put a 3/8 sprocket on the long bar, but interested to know what is not going right here. Slabs so far have mostly been macrocarpa (softwood cypress), pic for your viewing pleasure View attachment 827352

As Philbert puts it you are looking for the sweet spot which you do not have. My two pennies see an obvious solution and cause. For most part the 404 does not work on a 660. This is for several reasons. The 404 is a bigger longer chain than a 3/8'' so it will take quite a bit more torque. The 660 was designed around a 3/8'' thus it has more chain speed than a 075. I already went this route and concluded if you want to use the 660 which has quite a bit of power OP must slow the chain down as much as possible. As I remember a 6 or 7 tooth sprocket must be used. Do not quote me on this because I went through this several years ago. A muffler mod needs to take place because noise is not an issue and letting a little more exhaust flow will result in better cooling. I also found a 063 3/8'' chain works a little better because it is slightly more stable. Hope this helps a little and you will be happy with your live cuts. Thanks
 
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