Bill G
ArboristSite King
Rule of thumb.
No matter the length don't dip your tip where your tip don't belong ya dipstick
I got a 16'' bar for my MS 261 C-M
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No matter the length don't dip your tip where your tip don't belong ya dipstick
How many of you guys have actually cut up a bunch of wood with a hot rod 50cc saw with a 8 pin, .325 15-16 inch bar?
9/10 times it just cuts into whatever the tip hits lol.
I always hang onto the saw and expect it to kick back when the tip goes through the log im cutting and hits the next one but it just cuts it. The extra power/rpm makes it kick back less if anything. The only way I can get it to kick back is when I let off the gas and it's not revving high.
3/8 chain is a different story, it kicks back way more, there's a reason 16 inch bars have .325 chain.
9/10 times it just cuts into whatever the tip hits lol.
I always hang onto the saw and expect it to kick back when the tip goes through the log im cutting and hits the next one but it just cuts it. The extra power/rpm makes it kick back less if anything. The only way I can get it to kick back is when I let off the gas and it's not revving high.
3/8 chain is a different story, it kicks back way more, there's a reason 16 inch bars have .325 chain.
Bill G
ArboristSite King
You seem to forget 3/8LP
Actually physics would state that the mechanical advantage of a longer lever gives more force…….
I kinda did.
I tried 3/8lp on my 50cc saws, when they were stock it was great, once modded it didnt load them enough they just screamed while cutting unless you really dogged it in. If I end up with another 50cc saw that's nice but not real fast I'll put my 3/8lp set up on it.
The 3/8lp also doesnt kick back much at all if you keep the revs up.
There is enough content in Oliver's pictures and videos to make a nice Stihl based calendar, at least half the months for sure.
As to the physics. Are we taking all the energy in the crankshaft and flywheel assembly and putting it into motion or are we just making the tip of the bar to start to rotate at chain speed around an average of the center of mass, and the two handles? I would expect the inertia chain brake to activate in the scenarios envisioned in this wandering of the thread. A lever analysis wasn't what I expected.
Since a situation where kickback is likely to occur is not dogged in on a full bar length cut the chain is moving the same speed around the tip of the bar regardless of bar length, the mechanical advantage of a longer lever will make the force of the bar coming up rotate the whole assembly with less effort. Just like adding a cheater bar to a wrench lets you exert more force on what you are trying to turn. I suspect that the larger mass of the longer bar and chain may negate some of this force so it might be a toss up on which length makes for more kick back. A chain brake is only operated by inertia in the fact that the saw being forced to rotate upward will make your arm operate the brake if the saw rotates far enough. If you don’t have your hand on top of the handle in the path of the brake lever for whatever reason the brake is not going to operate.
I would also speculate that the OP being “inexperienced” might be an advantage to some extent. While not having experience can let you do things incorrectly is may also make him not complacent to the dangers faced to the point of being more prepared for those dangers. Safety records in the industrial world show this. The new and the experienced people are the ones that get hurt the most while the moderately experienced people have less injuries.
Blaa blaa blaa I got sucked into this argument.
While I used to like the shorter bars being easier to keep the tip out of places it shouldn’t be, I have come to like longer bars for not having to stoop as much to make cuts. This also leads to using the tip of the bar more thus leading to increased likelihood of kickback.
I would also speculate that the OP being “inexperienced” might be an advantage to some extent. While not having experience can let you do things incorrectly is may also make him not complacent to the dangers faced to the point of being more prepared for those dangers. Safety records in the industrial world show this. The new and the experienced people are the ones that get hurt the most while the moderately experienced people have less injuries.
Blaa blaa blaa I got sucked into this argument.
While I used to like the shorter bars being easier to keep the tip out of places it shouldn’t be, I have come to like longer bars for not having to stoop as much to make cuts. This also leads to using the tip of the bar more thus leading to increased likelihood of kickback.
So, the chain speed is the same, the diameter or arc of the rotation of the saw is greater, and that makes it easier to turn ? Don't think so.
It is slower because of more weight and drag.
And the radius of the nose in relation to the length of the arc.
False, hold the saw horizontally above a stump or block of firewood and let the nose drop. Experiment on how far it needs to fall to activate the inertia chain brake. This procedure is in some owners manuals. The weight that makes this happen is perhaps a square inch by half or 3/8 of an inch just from memory.
SteveSr
Addicted to ArboristSite
I think that the concept that everyone has been dancing around but not quite nailed is the physical property of inertia. Inertia is the resistance of a mass to movement caused by an external force.
When this concept is carried over to saws in a kickback situation larger saws and longer bars have more inertia keeping them from moving as violently in a kickback situation as smaller, lighter saws which will have less inertia.
This gets to be really important when you start talking about top handle saws with short bars. They have much less inertia and will react much faster in a kickback situation. This is compounded by the close hand placement making it more difficult, if not impossible to control any kickback movement.
In fact, the USFS chainsaw program does not recognize top handle saws and does not permit them. They designate them as "special purpose" arborists saws.
When this concept is carried over to saws in a kickback situation larger saws and longer bars have more inertia keeping them from moving as violently in a kickback situation as smaller, lighter saws which will have less inertia.
This gets to be really important when you start talking about top handle saws with short bars. They have much less inertia and will react much faster in a kickback situation. This is compounded by the close hand placement making it more difficult, if not impossible to control any kickback movement.
In fact, the USFS chainsaw program does not recognize top handle saws and does not permit them. They designate them as "special purpose" arborists saws.
The engineering jargon is "mass moment of inertia." And the effect of a given mass is proportional to the square of its distance from the center of rotation. In other words, a given mass at a radius of 20" will resist the rotational acceleration of a kickback much more than the same mass at 16".
There. Settled.
Pjohnson
ArboristSite Operative
Thank god...now we can get back to debating oil
Bill G
ArboristSite King
At least then folks will not try to tell a 14 year old kid how unsafe he is.......
3...2...1...go!
StihlPotlicker
ArboristSite Operative
doesn't even need to be short and fast, I will never forget the story my old supervisor told me about his bil (logger) who got the new 064 when they first came out, and he was so impressed with it, he stuck it in a log pile, and that sucker kicked back and cut is neck and shoulder, bad enough He needed staples and stiches and was off work for a long time. always always keep track of the tip of your bar. and you should learn about kick back.
Yes, like real kick back, not the little kicks lots of folks think is kick back...
Over the years I met two guys with scars from forehead to chin and one with the other telltale scar on his shoulder/neck. All were professional saw hands. Nasty, nasty cuts from real kickback.
Over the years I met two guys with scars from forehead to chin and one with the other telltale scar on his shoulder/neck. All were professional saw hands. Nasty, nasty cuts from real kickback.
