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#1
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How much HP is too much for a 14" Bandsaw?
Recently acquired a decent 2 hp 110/220a motor, and am now wondering if
it would be too much for my little BS. Has anyone had any experience with big motors on small bandsaws? Would this be the funny car of the woodshop? Regards, H |
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Tim Allen would't be pleased with your question.
Shame! Go for it! Grrrooowwerrrr! |
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wrote in message oups.com... Recently acquired a decent 2 hp 110/220a motor, and am now wondering if it would be too much for my little BS. Has anyone had any experience with big motors on small bandsaws? Would this be the funny car of the woodshop? Regards, H I have a cheap 12" Crapsman, aluminum framed bandsaw. It came with a 1/3 HP motor. It was not enough! I had a 1-1/2 HP motor laying around that I slapped into it! Works much better now! I don't think you can have too much HP! Greg |
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"Greg O" wrote in message I don't think you can have too much HP! Greg If all the lights on your block dim when you turn on the saw, you have too much horsepower. |
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"Edwin Pawlowski" wrote in message m... "Greg O" wrote in message I don't think you can have too much HP! Greg If all the lights on your block dim when you turn on the saw, you have too much horsepower. If all the lights go out, maybe, but just dim? No problem! Greg |
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wrote in message oups.com... Recently acquired a decent 2 hp 110/220a motor, and am now wondering if it would be too much for my little BS. Has anyone had any experience with big motors on small bandsaws? Would this be the funny car of the woodshop? An electric motor HP rating is what its capable of putting out. If you do not stress it, it does not produce any more HP than your existing motor. The only way to make it produce the full 2HP is to really load it up. So you are in control. Go for it. Bob |
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"Bob" wrote in message nk.net... wrote in message oups.com... Recently acquired a decent 2 hp 110/220a motor, and am now wondering if it would be too much for my little BS. Has anyone had any experience with big motors on small bandsaws? Would this be the funny car of the woodshop? An electric motor HP rating is what its capable of putting out. If you do not stress it, it does not produce any more HP than your existing motor. The only way to make it produce the full 2HP is to really load it up. So you are in control. Go for it. Two horse 110 is stretching things, which make me wonder if it's not one of those 3450 cap start cap run types. If so, remember to change the pulleys. The belt effectively limits the power available to the tool, but with a bandsaw's low torque requirements, shouldn't be a problem, just overkill. |
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Bob wrote:
An electric motor HP rating is what its capable of putting out. If you do not stress it, it does not produce any more HP than your existing motor. The only way to make it produce the full 2HP is to really load it up. I wish my electric meter believed that. -- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply) |
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Nova wrote:
Bob wrote: An electric motor HP rating is what its capable of putting out. If you do not stress it, it does not produce any more HP than your existing motor. The only way to make it produce the full 2HP is to really load it up. I wish my electric meter believed that. What a testament to the failure of science education in the general populace (Bob, not you Nova)... |
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Nova wrote:
Bob wrote: An electric motor HP rating is what its capable of putting out. If you do not stress it, it does not produce any more HP than your existing motor. The only way to make it produce the full 2HP is to really load it up. I wish my electric meter believed that. Have you checked it with an ammeter? -- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply) -- --John Reply to jclarke at ae tee tee global dot net (was jclarke at eye bee em dot net) |
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"Nova" wrote in message ... I wish my electric meter believed that. It does. You just don't believe its telling you the truth. Bob |
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"Duane Bozarth" wrote in message ... What a testament to the failure of science education in the general populace (Bob, not you Nova)... Are you saying my statement was wrong? Bob |
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On Wed, 22 Dec 2004 04:13:56 GMT, "BillyBob"
vaguely proposed a theory .......and in reply I say!: remove ns from my header address to reply via email "Duane Bozarth" wrote in message ... What a testament to the failure of science education in the general populace (Bob, not you Nova)... Are you saying my statement was wrong? I feel that the quote below is because of two factors (rusty memories struggle up through the ooze): - The motor is not running at synchronous spped eve with no load, so a larger HP motor wil draw fractioannly more. - The motor will run at near-synchronous until it stall, then it will start to draw the (much) heavier "starting" current, although it's failing to do the job. Because it;s running at near-synchronous while it's working properly, the correctly-matched motor will use less power even when fully loaded. Less wastage. However, if I had the choice as a hobbyist between a free 2HP motor and a $100 1 hp one, I woud use the free one for sure! G http://www.eng-tips.com/gviewthread..../237/qid/18465 "4.2.2. Efficiency at Low Load When a motor has a greater rating than the unit it is driving requires, the motor operates at only partial load. In this state, the efficiency of the motor is reduced (see Figure 4.2 ). The use of oversized motors is fairly common because of the following conditions:" "Replacement of underloaded motors with smaller motors will allow a fully loaded smaller motor to operate at a higher efficiency. This arrangement is generally most economical for larger motors, and only when they are operating at less than one-third to one-half capacity, depending on their size" |
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"Old Nick" wrote in message ... - The motor is not running at synchronous spped eve with no load, so a larger HP motor wil draw fractioannly more. The difference is not that great at no load speed. - The motor will run at near-synchronous until it stall, then it will start to draw the (much) heavier "starting" current, Typical loaded speed is 95% of synchronous speed. I don't know if that's what you meant by "near-synchronous". However when it gets near stall (break-down torque), the speed will be significantly slower. Breakdown torque might typically occurs at 70% of synchronous speed - quite a bit slower. "4.2.2. Efficiency at Low Load Your discussion of efficiency is accurate, but I don't think its relavent to the context of the OP's question - concern for damage ("too much for my little band saw"). Basically I was just saying that motor characteristics are such that it won't hurt the saw, if you don't force the saw to do things its not designed to withstand. Bob |
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On Wed, 22 Dec 2004 04:13:56 GMT, "BillyBob"
vaguely proposed a theory .......and in reply I say!: remove ns from my header address to reply via email hmmmm...having said that I have found a site that shows that motor efficiency peaks at around 30% of full load. It shows a significant blip there, then drops off steadily to 100% load / 80% efficiency. Given that high efficiency motors are now being built using larger conductors than necessary, Bob may have a point. ???????? "Duane Bozarth" wrote in message ... What a testament to the failure of science education in the general populace (Bob, not you Nova)... Are you saying my statement was wrong? Bob |
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"J. Clarke" wrote in message ... wrote: Until it's big enough to break expensive things if something gets hung up bigger is better with motors. Now if you were talking 200 horsepower, which is enough to sling the whole saw through the roof if something goes awry, then I'd say maybe it was too much motor, but 2 should be fine on a 14". If it was one of the little bitty miniature hobbyist jobs I'd be worried about twisting off the drive axle or slipping the pulley, but a 14" unless it's a real piece of garbage should have no trouble with 2 HP. Congratulations J. You clearly stated the case in way that anyone will understand and my hat is off to you. While some of us are getting tangled up in engineering design theory, you are came out and said what needs to be said. Bob |
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"Old Nick" wrote in message ... Bob may have a point. ???????? One of the best writeups on motors I have seen on the internet is from our very own rec.woodworking FAQ: http://www.faqs.org/faqs/woodworking/motors/ Another good writeup is http://www.engin.umich.edu/labs/csdl.../ac/induction/ Bob |
#20
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No problem. 2horspower is still pretty weenie.
wrote in message oups.com... Recently acquired a decent 2 hp 110/220a motor, and am now wondering if it would be too much for my little BS. Has anyone had any experience with big motors on small bandsaws? Would this be the funny car of the woodshop? Regards, H |
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Yes.
"BillyBob" wrote in message ink.net... "Duane Bozarth" wrote in message ... What a testament to the failure of science education in the general populace (Bob, not you Nova)... Are you saying my statement was wrong? Bob |
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CW wrote:
No problem. 2horspower is still pretty weenie. It depends. Most 14" bandsaw have a problem providing enough tension for a 3/4" blade without the frame flexing. Given a situation where a 2 HP motor would be beneficial, unless the saw was designed to handle that size motor, the frame of the saw would most likely flex, dropping the tension on the blade and result in a barreled cut. Hopefully that's the worse that would happen. Grizzly's tech support was iffy on a 1.5 HP on my G1019 and had a definite "no" on a 2 HP. -- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply) |
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In article ,
Nova wrote: CW wrote: No problem. 2horspower is still pretty weenie. It depends. Most 14" bandsaw have a problem providing enough tension for a 3/4" blade without the frame flexing. Given a situation where a 2 HP motor would be beneficial, unless the saw was designed to handle that size motor, the frame of the saw would most likely flex, dropping the tension on the blade and result in a barreled cut. Hopefully that's the worse that would happen. Grizzly's tech support was iffy on a 1.5 HP on my G1019 and had a definite "no" on a 2 HP. -- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply) The only time you really need the power and tension is when you're resawing, and when you're resawing, there's usually very little material on one side of the blade. So, it seems to me you could solve the frame flexing problem by having a removable strut which could be fitted as a compression member between the upper frame and the table when resawing. I've never seen such a thing on a bandsaw, but I find it hard to believe nobody else has thought of it before me. Does such a thing exist? |
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On Thu, 23 Dec 2004 19:27:06 -0500, Nova
calmly ranted: CW wrote: No problem. 2horspower is still pretty weenie. It depends. Most 14" bandsaw have a problem providing enough tension for a 3/4" blade without the frame flexing. Given a situation where a 2 HP motor would be beneficial, unless the saw was designed to handle that size motor, the frame of the saw would most likely flex, dropping the tension on the blade and result in a barreled cut. Hopefully that's the worse that would happen. The motor horsepower shouldn't be of any concern (unless too small.) I'd think the size of blade and the resultant tension required would be the limiting factors. Grizzly's tech support was iffy on a 1.5 HP on my G1019 and had a definite "no" on a 2 HP. Did they say why? Were they saying no to the combo or to the larger motor? My guess is the former, not the latter. -- "Most Folks Are As Happy As They Make Up Their Minds To Be" -Abraham Lincoln ----------------------------------------------------------- www.diversify.com - Happy Website Development |
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Larry Jaques wrote:
On Thu, 23 Dec 2004 19:27:06 -0500, Nova calmly ranted: CW wrote: No problem. 2horspower is still pretty weenie. It depends. Most 14" bandsaw have a problem providing enough tension for a 3/4" blade without the frame flexing. Given a situation where a 2 HP motor would be beneficial, unless the saw was designed to handle that size motor, the frame of the saw would most likely flex, dropping the tension on the blade and result in a barreled cut. Hopefully that's the worse that would happen. The motor horsepower shouldn't be of any concern (unless too small.) I'd think the size of blade and the resultant tension required would be the limiting factors. Blade friction. When you start resawing lumber where the power is needed a larger motor, say 2 HP will torque the frame. It will still pull the blade through the wood but with the flex the blade will "bunch up" above the drag. A smaller motor will stall before this happens. With my G1019 with the riser i got the distinct impression from Grizzly's tech support it would be risking snapping the frame with a 2 HP motor. Grizzly's tech support was iffy on a 1.5 HP on my G1019 and had a definite "no" on a 2 HP. Did they say why? Were they saying no to the combo or to the larger motor? My guess is the former, not the latter. If you mean the combo of the G1019 and a 2 HP motor, yes the saw was designed for a 3/4 HP motor. I don't know if the riser kit figured in, but I imagine it would. The tech says a 1 HP wouldn't be a problem, 1.5 was questionable and 2 HP was out. -- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply) |
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On Thu, 23 Dec 2004 20:36:43 -0500, Nova
calmly ranted: Larry Jaques wrote: On Thu, 23 Dec 2004 19:27:06 -0500, Nova calmly ranted: CW wrote: No problem. 2horspower is still pretty weenie. It depends. Most 14" bandsaw have a problem providing enough tension for a 3/4" blade without the frame flexing. Given a situation where a 2 HP motor would be beneficial, unless the saw was designed to handle that size motor, the frame of the saw would most likely flex, dropping the tension on the blade and result in a barreled cut. Hopefully that's the worse that would happen. The motor horsepower shouldn't be of any concern (unless too small.) I'd think the size of blade and the resultant tension required would be the limiting factors. Blade friction. When you start resawing lumber where the power is needed a larger motor, say 2 HP will torque the frame. It will still pull the blade through the wood but with the flex the blade will "bunch up" above the drag. A smaller motor will stall before this happens. With my G1019 with the riser i got the distinct impression from Grizzly's tech support it would be risking snapping the frame with a 2 HP motor. Blade friction?!? The motor drives the lower wheel which drives the blade and the upper wheel goes along for the ride. Whether you have a 0.5 or a 5.0 hp motor should make little difference, since the weight of the blade and upper wheel will be the same mass no matter what motor. Grizzly's tech support was iffy on a 1.5 HP on my G1019 and had a definite "no" on a 2 HP. Did they say why? Were they saying no to the combo or to the larger motor? My guess is the former, not the latter. If you mean the combo of the G1019 and a 2 HP motor, yes the saw was designed for a 3/4 HP motor. I don't know if the riser kit figured in, but I imagine it would. The tech says a 1 HP wouldn't be a problem, 1.5 was questionable and 2 HP was out. No, I meant the wider blade and higher tension. But did you tell him you'd be using low-tension Suffolk Timberwolfs? (Or were you?) How much difference in mass could the longer/wider blade make? 8 ounces? That slim margin would easily be quintupled by extra tension on the original bandsaw with the original spring. Inertial mass _can't_ be it. -- "Most Folks Are As Happy As They Make Up Their Minds To Be" -Abraham Lincoln ----------------------------------------------------------- www.diversify.com - Happy Website Development |
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Duane Bozarth wrote:
Nova wrote: Bob wrote: An electric motor HP rating is what its capable of putting out. If you do not stress it, it does not produce any more HP than your existing motor. The only way to make it produce the full 2HP is to really load it up. I wish my electric meter believed that. What a testament to the failure of science education in the general populace (Bob, not you Nova)... Well...... ;-) I made it 2/3 rds of the way to a mechanical engineering degree before switching to computer science. As an "inganeering" student I lernt alot about "conservation of energy" and the like. ;-) If you hook up a 1 HP motor and it turns the band saw at "X" FPM, and then you hook up a 2 HP (or 10 HP or 100 HP or 10M HP) motor and it also turns the saw at "X" FPM, what is the larger motor doing to consume more electrons? Radiating heat? Shooting arcs in the air? Writing its congressperson? It takes the same amount of power to spin the same machine at the same speed, so if there is a difference in electrons sacrificed by the different sized motors it has to be due to efficiency differences in the motors and/or the motors sending the electrons off to do other things. When my 14" Jet BS is running but not actually cutting wood, I haven't noticed the motor housing glowing red, or sparks jumping out of the motor, or letters to congresscritters coming out of the motor. Therefore I have to conclude that the motor is consuming only enough electrons to keep the the band saw mechanisms turning at a constanst speed against the forces of friction in the bearings, the unwillingness of the band saw blade to be bent and unbent, and the link belt groaning and complaining as it is bent and straightened. If you ignore internal differences in motors and hook up a 100 HP motor to the same Jet 14" band saw and it also drives the BS at the same speed, it is impossible for the difference of a single electron to flow through my electric meter -- unless the larger motor is shunting additional electrons elsewhere. When idling at a stoplight, I'll bet a Chevette and a Corvette are *producing* basically the same HP, even though there is a substantial difference in their maximum HP. ;-) -- Mark P.S. Those who finished engineering degrees are invited to correct my mis/mal understandings. ;-) |
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Roy Smith wrote:
The only time you really need the power and tension is when you're resawing, and when you're resawing, there's usually very little material on one side of the blade. So, it seems to me you could solve the frame flexing problem by having a removable strut which could be fitted as a compression member between the upper frame and the table when resawing. I've never seen such a thing on a bandsaw, but I find it hard to believe nobody else has thought of it before me. Does such a thing exist? File the patent. This looks like one of those "Why didn't I think of that???" things. ;-) -- Mark |
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Mark Jerde wrote:
Duane Bozarth wrote: Nova wrote: Bob wrote: An electric motor HP rating is what its capable of putting out. If you do not stress it, it does not produce any more HP than your existing motor. The only way to make it produce the full 2HP is to really load it up. I wish my electric meter believed that. What a testament to the failure of science education in the general populace (Bob, not you Nova)... Well...... ;-) I made it 2/3 rds of the way to a mechanical engineering degree before switching to computer science. As an "inganeering" student I lernt alot about "conservation of energy" and the like. ;-) If you hook up a 1 HP motor and it turns the band saw at "X" FPM, and then you hook up a 2 HP (or 10 HP or 100 HP or 10M HP) motor and it also turns the saw at "X" FPM, what is the larger motor doing to consume more electrons? Radiating heat? Shooting arcs in the air? Writing its congressperson? It takes the same amount of power to spin the same machine at the same speed, so if there is a difference in electrons sacrificed by the different sized motors it has to be due to efficiency differences in the motors and/or the motors sending the electrons off to do other things. When my 14" Jet BS is running but not actually cutting wood, I haven't noticed the motor housing glowing red, or sparks jumping out of the motor, or letters to congresscritters coming out of the motor. Therefore I have to conclude that the motor is consuming only enough electrons to keep the the band saw mechanisms turning at a constanst speed against the forces of friction in the bearings, the unwillingness of the band saw blade to be bent and unbent, and the link belt groaning and complaining as it is bent and straightened. If you ignore internal differences in motors and hook up a 100 HP motor to the same Jet 14" band saw and it also drives the BS at the same speed, it is impossible for the difference of a single electron to flow through my electric meter -- unless the larger motor is shunting additional electrons elsewhere. When idling at a stoplight, I'll bet a Chevette and a Corvette are *producing* basically the same HP, even though there is a substantial difference in their maximum HP. ;-) Just picking nits, the Corvette will be consuming more fuel because the larger engine has more and larger bits rubbing together and thus more friction. The difference will be small though. -- Mark P.S. Those who finished engineering degrees are invited to correct my mis/mal understandings. ;-) -- --John Reply to jclarke at ae tee tee global dot net (was jclarke at eye bee em dot net) |
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Mark Jerde wrote:
Well...... ;-) I made it 2/3 rds of the way to a mechanical engineering degree before switching to computer science. As an "inganeering" student I lernt alot about "conservation of energy" and the like. ;-) If you hook up a 1 HP motor and it turns the band saw at "X" FPM, and then you hook up a 2 HP (or 10 HP or 100 HP or 10M HP) motor and it also turns the saw at "X" FPM, what is the larger motor doing to consume more electrons? Radiating heat? Shooting arcs in the air? Writing its congressperson? It takes the same amount of power to spin the same machine at the same speed, so if there is a difference in electrons sacrificed by the different sized motors it has to be due to efficiency differences in the motors and/or the motors sending the electrons off to do other things. snip Start up current. Have you ever seen a 2 HP motor wired for 110 volts dim the lights while it spins up? I agree that once the motor spins up the running current difference is only that needed to keep the more massive armature turning and overcoming more friction of the larger bearings of the bigger motor, but I imagine you could run a 1/2 HP motor for 15 minutes on the current drawn by 2 HP motor on start up alone. -- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply) |
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Larry Jaques wrote:
Blade friction?!? The motor drives the lower wheel which drives the blade and the upper wheel goes along for the ride. Whether you have a 0.5 or a 5.0 hp motor should make little difference, since the weight of the blade and upper wheel will be the same mass no matter what motor. The blade friction is still there and has to be overcome. Unless the blade slips on the wheels the torque is taken by the frame. Think of it as pushing a rope which is the reason for barreled cuts. Grizzly's tech support was iffy on a 1.5 HP on my G1019 and had a definite "no" on a 2 HP. Did they say why? Were they saying no to the combo or to the larger motor? My guess is the former, not the latter. If you mean the combo of the G1019 and a 2 HP motor, yes the saw was designed for a 3/4 HP motor. I don't know if the riser kit figured in, but I imagine it would. The tech says a 1 HP wouldn't be a problem, 1.5 was questionable and 2 HP was out. No, I meant the wider blade and higher tension. But did you tell him you'd be using low-tension Suffolk Timberwolfs? (Or were you?) How much difference in mass could the longer/wider blade make? 8 ounces? That slim margin would easily be quintupled by extra tension on the original bandsaw with the original spring. Inertial mass _can't_ be it. I normally use a 1/2" Timberwolf blade which Suffolk recommended for the saw. I tried there 3/4" and as Suffolk predicted the saw can't handle the tensions produced by the added blade friction of the extra 1/4" blade width while resawing. It is especially noticeable when attempting to saw "green" lumber (i.e. milling short logs into boards) which has more of a tendency to bind the blade. -- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply) |
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On Fri, 24 Dec 2004 03:52:21 GMT, "Mark Jerde"
wrote: P.S. Those who finished engineering degrees are invited to correct my mis/mal understandings. ;-) I think that the difference involved occurs when both are under load. A bull and a mouse can pull a small toy behind them a the same speed if the bull takes it slow and easy. If the toy sticks against something, the mouse will stall. The bull will destroy the toy, the something, and anything else that gets in the way. It's smart to not overdo it. |
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On Fri, 24 Dec 2004 08:49:06 -0500, Nova
calmly ranted: The blade friction is still there and has to be overcome. Unless the blade slips on the wheels the torque is taken by the frame. Think of it as pushing a rope which is the reason for barreled cuts. I think of it as the wheel pulling the teeth down, into the wood. The majority of the tension on the blade is between the table and the bottom wheel on the downward side. Since the wheels are connected, there may be a very minor amount of "pushing", but the fact that the band is laying on the -outside- of the wheels precludes much of that. Any attempt at pushing would simply make space between the blade and the wheel, and that could come only if there was no tension on the blade at all. No, it is my understanding that barrel cuts are the result of insufficient tension on the blade. No, I meant the wider blade and higher tension. But did you tell him you'd be using low-tension Suffolk Timberwolfs? (Or were you?) How much difference in mass could the longer/wider blade make? 8 ounces? That slim margin would easily be quintupled by extra tension on the original bandsaw with the original spring. Inertial mass _can't_ be it. The only part I can see being stressed by having a larger motor would be the lower wheel (major) and its bearing (minor). Startup might be quicker, creating higher initial (and inertial) stress, and it would be able to do more work when making heavy cuts while resawing. The upper wheel and frame are merely used as guides for the band. I just don't buy that C-frame flex thing at all. Wider bands and the higher tension needed to run them would be the only cause of frame stress that I can see. No, I take that back. The frame may have more stress AT the lower wheel bearing mount during heavy cuts. The wheel being slightly deflected upward up would also result in lower tension on the blade, with the tension spring attempting to take up that slack. Maybe the guy at Griz could expand on his concerns. I'd be very interested (despite having their old heavy-duty 18" G1012.) I normally use a 1/2" Timberwolf blade which Suffolk recommended for the saw. I tried there 3/4" and as Suffolk predicted the saw can't handle the tensions produced by the added blade friction of the extra 1/4" blade width while resawing. It is especially noticeable when attempting to saw "green" lumber (i.e. milling short logs into boards) which has more of a tendency to bind the blade. Yeah, and they make resaw blades for both green and dried wood, with different set, hook angles, gullet depth, etc. for each one. -- "Most Folks Are As Happy As They Make Up Their Minds To Be" -Abraham Lincoln ----------------------------------------------------------- www.diversify.com - Happy Website Development |
#34
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"Larry Jaques" wrote in message ... On Fri, 24 Dec 2004 08:49:06 -0500, Nova calmly ranted: The blade friction is still there and has to be overcome. Unless the blade slips on the wheels the torque is taken by the frame. Think of it as pushing a rope which is the reason for barreled cuts. I think of it as the wheel pulling the teeth down, into the wood. The majority of the tension on the blade is between the table and the bottom wheel on the downward side. Since the wheels are connected, there may be a very minor amount of "pushing", but the fact that the band is laying on the -outside- of the wheels precludes much of that. Any attempt at pushing would simply make space between the blade and the wheel, and that could come only if there was no tension on the blade at all. No, it is my understanding that barrel cuts are the result of insufficient tension on the blade. How about this: The free-wheeling upper wheel gets ahead of the driven, but loaded lower, causing the blade to bunch into the gap. Doesn't take much difference in speed to start the process, which then increases in effect as the bunched part slows.... |
#35
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George wrote:
.... How about this: The free-wheeling upper wheel gets ahead of the driven, but loaded lower, causing the blade to bunch into the gap. Doesn't take much difference in speed to start the process, which then increases in effect as the bunched part slows.... The upper wheel isn't free-wheeling, it's driven/pulled by the blade...the blade makes the wheel move, not the other way round... |
#36
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Larry Jaques wrote:
.... The only part I can see being stressed by having a larger motor would be the lower wheel (major) and its bearing (minor). Startup might be quicker, creating higher initial (and inertial) stress, and it would be able to do more work when making heavy cuts while resawing. The upper wheel and frame are merely used as guides for the band. I just don't buy that C-frame flex thing at all. Wider bands and the higher tension needed to run them would be the only cause of frame stress that I can see. No, I take that back. The frame may have more stress AT the lower wheel bearing mount during heavy cuts. The wheel being slightly deflected upward up would also result in lower tension on the blade, with the tension spring attempting to take up that slack. You've got it except you're overlooking the fact that the blade is pulling on the outside of the upper wheel which is applying torque to the frame...as the motor applies more power to the blade this gets transferred to a higher load which could in extreme case, cause the support to fail... |
#37
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In article ,
Duane Bozarth wrote: George wrote: ... How about this: The free-wheeling upper wheel gets ahead of the driven, but loaded lower, causing the blade to bunch into the gap. Doesn't take much difference in speed to start the process, which then increases in effect as the bunched part slows.... The upper wheel isn't free-wheeling, it's driven/pulled by the blade...the blade makes the wheel move, not the other way round... On the other hand, the upper wheel has rotational inertia. It's an interesting dynamics problem to figure out exactly what happens if you get the whole system up to speed and then place drag on the downward-moving blade. |
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On Fri, 24 Dec 2004 11:57:37 -0600, Duane Bozarth
calmly ranted: Larry Jaques wrote: ... The only part I can see being stressed by having a larger motor would be the lower wheel (major) and its bearing (minor). Startup might be quicker, creating higher initial (and inertial) stress, and it would be able to do more work when making heavy cuts while resawing. The upper wheel and frame are merely used as guides for the band. I just don't buy that C-frame flex thing at all. Wider bands and the higher tension needed to run them would be the only cause of frame stress that I can see. No, I take that back. The frame may have more stress AT the lower wheel bearing mount during heavy cuts. The wheel being slightly deflected upward up would also result in lower tension on the blade, with the tension spring attempting to take up that slack. You've got it except you're overlooking the fact that the blade is pulling on the outside of the upper wheel which is applying torque to the frame...as the motor applies more power to the blade this gets transferred to a higher load which could in extreme case, cause the support to fail... How could the inertial mass of the blade and aluminum wheel (under 10 pounds would be my highest guess) cause any more tension on the frame than the tension adjustment spring, which is in the hundreds of pounds? I still don't buy it, but I would like to hear the Griz tech's explanation. ---------------------------------------------------------------------- * Scattered Showers My Ass! * Insightful Advertising Copy * --Noah * http://www.diversify.com ---------------------------------------------------------------------- |
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Roy Smith wrote:
In article , Duane Bozarth wrote: George wrote: ... How about this: The free-wheeling upper wheel gets ahead of the driven, but loaded lower, causing the blade to bunch into the gap. Doesn't take much difference in speed to start the process, which then increases in effect as the bunched part slows.... The upper wheel isn't free-wheeling, it's driven/pulled by the blade...the blade makes the wheel move, not the other way round... On the other hand, the upper wheel has rotational inertia. It's an interesting dynamics problem to figure out exactly what happens if you get the whole system up to speed and then place drag on the downward-moving blade. Not a tremendous amount, however, as the mass of the wheel isn't all that great... But, you're correct, it's a fairly complex dynamical system if one accounts for all effects including blade slip, stretch, ... |
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Larry Jaques wrote:
.... How could the inertial mass of the blade and aluminum wheel (under 10 pounds would be my highest guess) cause any more tension on the frame than the tension adjustment spring, which is in the hundreds of pounds? I still don't buy it, but I would like to hear the Griz tech's explanation. It's not the inertial mass we're talking about here...it's the extra torque exerted by the larger motor when more force is exerted (particularly suddenly) by the blade through the material... |
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