Circle saw friction question

[woodbowl]

You know how a circle saw throws those long chips on a shallow cut and short chips on a deep cut?

I've been wondering if there is a power difference between the two. Of course there is more blade in the wood on a deep cut, but to put it in to a different perspective, say you had two different diameter blades, but they cut at the same depth. Because the large blade is bigger in diameter, it covers a longer stroke and the angle is shallow, therefore slicing off long slivers. The smaller blade covers a shorter distance and the angle is more abrupt on both the entry and the exit. This arrangement bucks short chips to begin with upon entry, then long slivers in the bottem of the cut, then back to shorter chips again as it exits the cut.

Another perspective would be a saw with one blade doing all the work, and cutting 4" deep VS another saw with two blades arranged in tandum configuration. The first blade runs ahead and cuts only 2" deep and the second blade follows at a depth of 4", however it is only cutting 2" of wood because it rides in the groove cut from the first blade. The first example throws short chips and the 2nd example throws long chips.

The question is, which configuration would have the least amount of friction, thus the least amount of power needed?

[UNCLEBUCK]

I throw the same size chip no matter what size the log is, big logs take more power as my feed rate does not change . That is all I know and not a thing more  :D

[Ianab]

Yes I find that shallow cuts use MUCH less power than a full 8" pass.

Swingblade is different from a conventional circle mill because a shallow cut uses the outside edge of the blade and a very shallow angle, you cut long slivers. With a conventional circle mill the shallow cut is still made close to the hub at a steep angle.

I find I can often make 2 4" passes in less time than one 8" cut, including the backup and adjustment time. With more power it might not be so noticable. A 1 or 2" pass the engine hardly knows the wood is there 

Cheers

Ian

[NZJake]

I think your right, three large diameter blades offset slightly from each other, taking only 2" bites each to make a 6" combined theoretically will cut with less friction than having only one blade of the same diameter.

Less deflection and more of a ripping effect.

Which would cut faster after installing all the extra bearings and pulleys I dunno? You could balance the teeth timing of the three blades to help it along though.

[NZJake]

Well while in Aus last weekend (woodshow) I got to cut up a load of Iron bark, they said that this particular type of iron bark was one of the hardest timbers in Aus. I believed them, taking 3" passes at a time to make a 10" cut, I think people were amazed at how well the ASM ate it up.

The finish was absolutely perfect, I think taking smaller bites like this atributes to a much smoother cut in hard timbers, the first and second cut actually leaves a guide for the blade to follow for the next, just like band guides (tracks the blade perfectly).

[Captain]

Woodbowl, there is also a difference in the choice of kerf vs plate thickness to consider.  When sawing softwood with the normal chip expansion, it is actually easier to saw with a tip that has more side clearance.  I'm beginning to prefer a blade that has a full 1/4" kerf in softwood, and using the normal 3/16" kerf for hardwood.  Similar to what you band mill folks do with your set for sawing each species.

Hey Jake, you gotta change your signature before YOUR WIFE (not girlfriend any longer) reads it...

Captain

[Part_Timer]

That Captain  always looking out for the other guy. :D :D

[NZJake]

LIFESAVER!
Cheers Captain.

[woodbowl]

......  three large diameter blades offset slightly from each other, taking only 2" bites each to make a 6" combined theoretically will cut with less friction than having only one blade of the same diameter.

You could balance the teeth timing of the three blades to help it along though.

Jake, how do you mean, balance the teeth timming?

[NZJake]

Picture 3 blades with 4 teeth each, timed so that each tooth from each three blades are cutting equally in relationship around the circumferance. Picture 3 blades on top of each other, showing each tip equal in relation to each other around the circ. Combined with a non slip belt.

Clear as mud? Hope I explained right.

[woodbowl]

Hmmmm ........ That would mean 4 teeth per blade X 3 blades = tooth spacing the same as 12 station points on the clock. Or 360°  / 12 = 36° spacing. I wonder if there would be much of a difference, considering the fly wheel effect, if the teeth occasionally grouped in the cut.

[Ianab]

Or it could just be too complicated and heavy and bulky....

And it's probably simpler to just put a bigger engine on there   ;)

Ian

[customsawyer]

I have a question. What is a band sawyer doing asking circle blade questions? I think he is trying to throw some of you off his trail but don't let it throw ya. :D

[NZJake]

Ian, probably...

When you can do the same principle on a swinger. Fast as lightning too on the ASM .

[woodbowl]

What is a band sawyer doing asking circle blade questions?

customsawyer, I've got a few ideas up my sleeve. If a swinger can cut faster in two shallow passes than it can in one, why not mount several blades in tandem, put some power on that rascal, turn the wick up and fly through the wood.

[DanG]

I don't think "friction" is the right term for it.  Running a multi-blade dimension saw gives you lots of opportunities to study the behavior of blades in different situations.  I think it has more to do with the angle the blade attacks the wood, in relation to the grain.  In a shallow cut, you are cutting more parallel to the grain, while a deep cut is more perpendicular.  Liken it to cutting with an axe.  If you hit a log perpendicular, you'll be lucky to get past the bark, but if you put a bit of angle on your blow, you'll remove quite a chunk of wood.

I think Woodbowl's idea would work just fine, but I just ain't sure it would be worth all the engineering it would take.

[NZJake]

When you change your hook you either get a chunky chip or a fine dust like chip in the deep cut. Peelings come from a very slight radial cut. In my opinion more friction is created when you are cross cutting multiple layers of growth rings.

Maybe resistance would be the correct term?

[Fla._Deadheader]

How ya gonna allow for tension moving the log with multi blades ???

[woodbowl]

I don't think "friction" is the right term for it.  ....... I think it has more to do with the angle the blade attacks the wood, in relation to the grain. 

Maybe resistance would be the correct term?

Yea, .........  It's all of those and more. What ever it's called, it's about the relationship between the two extremes.....  The traditional hogging of a one pass deep cut   Vs   multiple shallow passes.  The difference is the attack angle of the blade in relationship to the wood. The visual results are the short chips   VS   the long shavings. The primary desired goal is to cut faster. Secondary goals are to use less power, reduce wear rates on the blades, reduce heat, reduce other wearing pressure points associated with heavy, one blade cuts and hopefully be able to get away with using thin kerf blades to achieve a deep cut which takes even less of the above.

Blade angle induced friction and resistance. ...... ??  ??  ??