When I learned sawing logs (eastern white pine), it was from an old timer who was using a circular saw.
He would try and square up a cant and then cut boards so when they left the saw they were done.
But he would only saw to the heart/pith and then roll the log/cant over and saw in from the other side, thus reducing the stress in the log hopefully, evenly. And if the log did have stress in it, the last board, known as the dog board as it was the one dogged to the mill carriage, maybe be out of shape. Such as hour glass shaped, thin in the middle thick at the ends or the other way around. And if this board was out of shape it didn't matter much as it was the lowest grade board in the log due to the pith/heart being in it.
If the boards coming off the log did have some round edge to it, he wouldn't completely saw them off the log, he'd saw them until just about to drop off the log, and "gig" back and drag the board back to the log deck. I'd be standing at the tail end of the mill, and he'd grab the board and twist it up from the bottom, breaking the holding grain off the log, with my help. And we'd stack the round edge boards up on the log deck.
Then after he had finished sawing the second side of the cant and the carriage was empty, we'd stack the round edge boards up on carriage in line with the saw so that he could run them down past the saw and cut off the round edge on one side.
Then we'd flip them over and run the other side to a set width.
If he did, by accident, cut off a round edge board and it went down the conveyor belt to the board pit, the pit man would set it aside and it would be brought back to the log deck by the fork lift and re-processed to create square edged boards.
When I saw logs here at my mill, I try and square up a cant that will produce finished boards at the end of the cut. And following the cut to the pith/heart method and then flip over and come in from the other side, as I was taught.
But in doing this, you have to "read" the log and watch for stress. And if you see the boards shifting as you're sawing them you have to adjust your sawing plan based on what you see. Especially sawing hardwoods.
Jim, this is what we do today, was a different approach applied in the muley days? I believe that is NH's question/quiz. I do think it was approached differently, how different I am not sure. We will see.
Centripetal force is the new term applied to what we used to call centrifugal force. Centrifugal force is not found in todays high school Physics book, it has been so since the late 1990's.
Centripetal force is as you said a force toward the center, and I like the "violent" you through in there. It is attached to the center by a string, chain or gravity, these are the connections to the center hence the force. This is Newtons second law F=ma. If this connection is severed or released the object will travel in a direction away from the center in a straight line, it will no longer circle the center, there for no centrifugal force exist, it is now just accelerating. The force is connected to the center, centripetal.
I knew you would try your best to come on with an answer Jim and thanks for the information and a look at your sawing technique.
Timbeal also thanks for coming on board and your remarks on the centifugal versus the centripetal forces. I had to look it up in the dictionary because I wasn't familiar with the term myself, but then again I am only an old farm boy with a one room school house education.
I am sorry Jim I mistakenly thought you were familiar with the workings of a Mulley Mill, to this end and for the sake of others that drop by I will quickly review the basic workings of such a mill.
I believe that everyone knows now that the Mulley Mills were basically driven by water, used a vertcal 6 foot blade, and in some cases 7 foot blades, these blades were stiff enough to withstand the upper thrust of a pitman revolving under the floor level, or in the area adjacent to the water barrel.
The saw frame was on the second floor and was usually mounted on wooden v shaped hardwood slides imbedded into the soft pine beams of the saw frame and slid back and forth passing by the blade on other v shaped hardwood blocks imbedded in the floor timbers.
I had mentioned that there were no modern methods used to roll the timbers on the saw frame, just cant hooks and pointed bars.
Once loaded on the saw frame the log is positioned in front of the blade in such a way that the best use of the log can be realized. The log is held in position for the cut by pounding in heavy cast iron dogs on each end of the log.
What I had eluded to was once a sufficient flat surface was cut on one face of the log, (usually 2 cuts). the log was rolled 1\4 turn on this face and then lined up for the second series of cuts.
Now the first 2 boards had both edges round and these boards were laid aside. The next set of boards all have one flat side, and if you cut right across the log all the boards would have one flat side and some of the centre boards would be quite wide and have some nice outside material in them. In a maximum centre cuts you could obtain a few 25 or 26 inch boards from a large pine log
This was the fastest way of cutting up a log with a Mulley saw, but edging the boards was tricky because there were no centre supports in a mulley saw frame only end supports, only one being moveable to accomodate different length of logs.
We normally squared our timbers getting as much good lumber from around the heart and as Jim mentioned as you neared the centre during the final cuts at times the final piece would be a little out of square or varied in dimension from end to end.
We used to vie with one another to see who could saw out the truest lumber and finish up with the centre cut true end to end, not an easy feat on these old saw frames, but quite possible if you took care in set up.
These blades had 2 inch teeth at about 2.25" spacings, and the teeth were bent slightly alternating to create a cerf.
The blade was also slightly out of perpendicular so that on the up stroke the teeth would lift away from the face of the cut, and gave the log enough room to move ahead before the blade descended for the next cut
I hope this helps explain the workings of a mulley mill, they could be very temperamental and each cut had to be monitored to be able to compensate its wanderings on each succeding cut.
Nice to hear from you guys your questions help to expand on this conversation for the benefit of others.
We have to clarify one technical aspect of this type of mill A Mulley Mill operates with a free standing blade, which is an improvement on the earlier style of what was referred to as a sash saw, or a rather thinner blade which had to be restrained in a wooden sash, and the whole sash had to be lifted and lowered to move the blade up or down so the cutting action could be done.
The Mulley blade was about 3\16 " in thickness and as I mention earlier the teeth are about 2" in length at 2.25" spacings and the configuration is almost identical to a rip tooth on a small hand saw. The bottom edge of the tooth is almost square out from the blade (not quite) and sharpened square across and slightly beveled on the other remaining angled edge.
There were two methods of preparing the tooth for the cutting action the first was to slightly bend the tip of each alternating tooth slightly to create a kerf, or swedge the tooth tip to also create a kerf.
We always slightly bent the tooth tip which seemed to work well, so I cannot speak for the other method. I do feel though that it would work well used by an experienced mill operator.
Anoter thing that we always did was to peel a slight channel in the bark ahead of the blade on the initial cut to ensure that removal of any hidden debris was effected cleanly for the blade.
These blades dulled easily and if the teeth became damaged on one side the blade would then begin to wander and heating problems would develop and poor quality lumber with uneven thicknesses would be noticed
Jim: Look back in earlier posts, you will find views of the water barrel being restored, also you will see views of the 12" diameter oak shaft being turned and prepared for the insertion and the eventual leading in of the cast iron crank on the pitman end, as well as the cast iron bearing on the running ends of the shaft.
You will also see the 2 large cast iron disks that have the buckets casted into them and that also are mounted on turnings on the shaft, one on each side of the water barrel (box). These cast disks are what give propulsion to the shaft as the water hits them from inside the pressurized box during start up.
You will also see views of the saw blade in the sawing area, and the large 20 foot saw frame with the (2) bunks , one solidly mounted and the other that can slide along on the frame to accomodate different length of logs.
These pictures should be rather close to the beginning of this thread, but not right at the beginning.
Ken: The crank has an offset of 9" giving the saw an 18" stroke. Now on large logs (say logs over 18" and up to 36") during the cutting process the saw dust has to work its way out from along side of the blade and in the cavities between the teeth, so on large cuts you need to take your time to allow this to take place.
here's one for you northern hewer: i mentioned a finish-canadian style of hewing, standing on the log. it's not a replacement for standing beside, but sometimes it's a way to zing through the wood. and you get the balance game.