carver
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Post by carver on Nov 8, 2019 18:18:33 GMT -5
Hi, For 18" slab saws, the saw blades are supposed to run between 760rpm and 1100rpm per the manufacturer specs (Barranca Diamond). My Dayton 3/4 hp motor seems weak and stalls out on thicker cuts fairly often so I am going to replace with either a 1HP or 1.5HP motor. Cost of electricity or parts is irrelevant to me, I just want it to work correct. I am going to control the speed with varying the pulley ratio on the motor and shaft so that the blade rotates around 960rpm. I live in a wealthy area that has an HOA that gets upset of minor things so noise is a concern to me and my garage wall is shared with 1 neighbor whose garage is attached to the wall. I need something powerful enough to cut through stones without stalling out as I have melted several belts while I was inside the house as I don't sit in the garage when I do cuts but rather am inside. I was thinking about using a 1HP 1100rpm motor rather than a 1HP 1800RPM motor to cut down on some of the noise. What are the problems that will arise from this if any? Will the motor be more likely to bog down or less or no difference because the HP is the same? Any engineers I am sure know this but I do not but am taking intro physics in college currently so know a little about motors but not much.
Also is the noise level greater for the same motor at 1.5HP over 1HP? Last question is single phase bad?
And for other people in the future reading this, here are some suggestions I read online for lapidary slab saw motors. Take at your own risk, I am not an expert but did spend about 10 hours researching this. Maybe use this as a guide to help you research more until you are sure.
****make sure to get a motor rated for CONTINUOUS USE *get a totally enclosed motor (TENV) *potentially get a washdown motor *get a thermally protected motor *3/4hp or 1HP for an 18" slab saw *do not need capacitor start because you are not starting slab saws underload, one forum member said may even be worse off for some reason I didn't understand but he did sound like he had an engineering background.
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Post by Drummond Island Rocks on Nov 8, 2019 19:48:47 GMT -5
I'll be interested to see what kind of responses you get to this. My first thought is go with the same RPM motor just up-size HP so you do not need to do all the pulley math but you mention a noise difference between different RPM motors. I can't see how that plays in. As soon as any of my saw blades hit a rock the blade grinding the rock is way louder then the motor noise. Just about every motor I have is just a hum when not connected to anything. I never noticed certain motors being louder than others without a load on them.
Chuck
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carver
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Member since November 2019
Posts: 36
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Post by carver on Nov 8, 2019 20:38:05 GMT -5
I'll be interested to see what kind of responses you get to this. My first thought is go with the same RPM motor just up-size HP so you do not need to do all the pulley math but you mention a noise difference between different RPM motors. I can't see how that plays in. As soon as any of my saw blades hit a rock the blade grinding the rock is way louder then the motor noise. Just about every motor I have is just a hum when not connected to anything. I never noticed certain motors being louder than others without a load on them. Chuck Thanks Chuck. I agree with you that the motor noise is likely less than the grinding in high pitch noise which is what we hear when we're cutting in the room. However, the vibrating lower pitch noise (think subwoofer noise rather than tweeter) is what you hear in the next room over more which I would think would probably be linked to the motor vibration speed as apposed to the saw blade grinding noise. In regards to the pulley math, with 7k posts I am certain you know how to calculate the math but for others that don't that read this later it is actually really easy to calculate and you only need to really do it once because most people set the saw blade speed only once. Even if switching between the Baranna Diamond 303 and 301 blades which differ in recommended speeds, the middle point (960rpm) is useable for both blades. A larger diamond pulley size presumably allows for less belt slippage under stress though that may not be an issue for others but may cause more torque if on the motor shaft pulley? I am really not sure and was hoping others could know. The larger pulley size on the motor of course would be needed if going with the 1200RPM because you are not stepping down as much as you would be on the 1800 so the ratio between the saw arbor shaft pulley circumference and motor shaft pulley circumference needs to be closer to 1.
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Post by catmandewe on Nov 8, 2019 23:52:13 GMT -5
It all depends on torque, you can gear down a 3500 rpm motor to work on a saw but the problem is that when it gets deep into the cut then the torque of the motor falls out so it cant keep up with the speed and ends up burning the motor up so inversely the 1100 rpm should actually work better because it will be closer to the actual operating rpm thus wont tend to lose torque in the cut. Of course there are other things to factor in such as SF (Service Factor), capacitor start is handy if you need to shut your saw off in the middle of a cut, then you can start back up in the middle again. A 220V motor needs to work less than a 110V motor to do the same job so if you can go 220V it will make it work better.
Tony
PS I am not an engineer, just a tinkerer
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carver
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Member since November 2019
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Post by carver on Nov 9, 2019 15:54:19 GMT -5
It all depends on torque, you can gear down a 3500 rpm motor to work on a saw but the problem is that when it gets deep into the cut then the torque of the motor falls out so it cant keep up with the speed and ends up burning the motor up so inversely the 1100 rpm should actually work better because it will be closer to the actual operating rpm thus wont tend to lose torque in the cut. Of course there are other things to factor in such as SF (Service Factor), capacitor start is handy if you need to shut your saw off in the middle of a cut, then you can start back up in the middle again. A 220V motor needs to work less than a 110V motor to do the same job so if you can go 220V it will make it work better. Tony PS I am not an engineer, just a tinkerer Thank you, I will go with a capacitor start for the reason you mentioned. I am also having my dad install a 220V outlet so I can go with a 220V motor. I just got the highest grade out of 170 students in my Physics class so I should understand Torque but I'm afraid its all textbook knowledge as opposed to application use. My dad was trying to explain what you are describing with torque. The saw arbor shaft will be running at 950 while the motor will be running at whatever speed the motor is supposed to, I am not going to lower the speed of the motor with a dial but rather just vary the pulley size so I don't understand how the operating RPM would be relevant though you clearly know more about motors than me.
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Post by woodman on Nov 9, 2019 21:32:30 GMT -5
A couple of things I would look at first. 1: what is your feed rate? maybe too fast. 2: How long has it been since the blade was sharpened? I don't know the size of the motors I have on my 18 and 24, but they are both 110. I should check and see what my blade speed is.
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carver
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Member since November 2019
Posts: 36
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Post by carver on Nov 10, 2019 2:08:01 GMT -5
A couple of things I would look at first. 1: what is your feed rate? maybe too fast. 2: How long has it been since the blade was sharpened? I don't know the size of the motors I have on my 18 and 24, but they are both 110. I should check and see what my blade speed is. How often should you sharpen your blade? I only have trouble with taller stones (~6" tall on an 18"). Every quartz tall quartz cut jams it as do larger others like Jasper/Hematite.... How would you do it, simply by cutting a cinderblock? My feed rate I can vary using different pulleys but use about 6-7 inches of cart travel per hour as standard. For checking blade speed, I had my dad instal a 10 dollar Hall Sensor from Amazon that came with a digital display. I simply mounted the display in a plastic electric box next to my pulley cover and powered it through the saw's motor and now I have an RPM gauge on my saw so I know if its starting to bog down rather than having to guess. This was money well spent. If I knew how to install an automatic kill switch when the RPM drops below a threshold I would love to install that but unfortunately I don't know of a method to do this.
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Post by woodman on Nov 10, 2019 10:30:52 GMT -5
A couple of things I would look at first. 1: what is your feed rate? maybe too fast. 2: How long has it been since the blade was sharpened? I don't know the size of the motors I have on my 18 and 24, but they are both 110. I should check and see what my blade speed is. How often should you sharpen your blade? I only have trouble with taller stones (~6" tall on an 18"). Every quartz tall quartz cut jams it as do larger others like Jasper/Hematite.... How would you do it, simply by cutting a cinderblock? My feed rate I can vary using different pulleys but use about 6-7 inches of cart travel per hour as standard. For checking blade speed, I had my dad instal a 10 dollar Hall Sensor from Amazon that came with a digital display. I simply mounted the display in a plastic electric box next to my pulley cover and powered it through the saw's motor and now I have an RPM gauge on my saw so I know if its starting to bog down rather than having to guess. This was money well spent. If I knew how to install an automatic kill switch when the RPM drops below a threshold I would love to install that but unfortunately I don't know of a method to do this. I bought some cheap silicon carbide grinding wheels and just make a couple cuts on them. I do it when i feel that it is taking to long or like on my 24, when I fried the belt.
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Post by Rockoonz on Nov 10, 2019 15:25:20 GMT -5
If you're burning through belts while you're cutting then your motor isn't stalling, your blade is. Feed speed, blade condition, and a score of other factors could be the root cause. Knowing what brand of saw, feed type, and blade brand/type would help as far as giving advice.
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carver
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Member since November 2019
Posts: 36
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Post by carver on Nov 10, 2019 19:02:50 GMT -5
If you're burning through belts while you're cutting then your motor isn't stalling, your blade is. Feed speed, blade condition, and a score of other factors could be the root cause. Knowing what brand of saw, feed type, and blade brand/type would help as far as giving advice. I have no idea what brand it is. I remember a plaque that said something like slab master or master slabber but I never could find anything online and I have since painted over it. The feed rate is roughly 6 inches per hour. The blade is MK 301 18". Feed type is carriage power feed powered by a belt linked to a 4rpm motor. The belt has burned through several times (it is a connector nylon link belt) when the blade locked up as well as once which stopped the blade and motor. Blade condition seems good because it is mostly new and has only cut about 75 slabs of red jasper and hematite/dinosaur gem bone.
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Post by aDave on Nov 10, 2019 20:06:40 GMT -5
I can't help with your problem(s), but I'm wondering if you have seen this document in the first post in this thread: forum.rocktumblinghobby.com/thread/52499/general-lapidary-infoFrom most of the responses I've seen about it, it appears to be fairly well received. Perhaps you can get some helpful tidbits. Good luck.
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carver
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Member since November 2019
Posts: 36
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Post by carver on Nov 11, 2019 1:11:57 GMT -5
I can't help with your problem(s), but I'm wondering if you have seen this document in the first post in this thread: forum.rocktumblinghobby.com/thread/52499/general-lapidary-infoFrom most of the responses I've seen about it, it appears to be fairly well received. Perhaps you can get some helpful tidbits. Good luck. Thanks for the suggestion, I will read that.
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Post by Rockoonz on Nov 11, 2019 1:21:56 GMT -5
I can't help with your problem(s), but I'm wondering if you have seen this document in the first post in this thread: forum.rocktumblinghobby.com/thread/52499/general-lapidary-infoFrom most of the responses I've seen about it, it appears to be fairly well received. Perhaps you can get some helpful tidbits. Good luck. What are the diameters of the pulleys that drive the blade?
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Post by woodman on Nov 11, 2019 17:34:29 GMT -5
On my 18 inch lortone, the motor pulley is 2" and the pulley on the blade arbor is 7 inches. was going to get rpm reading but my meter battery is dead. need to get a new 9 volt battery! If I am right on motor RPM is should be getting a blade RPM of about 700 www.blocklayer.com/pulley-belteng.aspx
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carver
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Member since November 2019
Posts: 36
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Post by carver on Nov 14, 2019 0:49:01 GMT -5
I can't help with your problem(s), but I'm wondering if you have seen this document in the first post in this thread: forum.rocktumblinghobby.com/thread/52499/general-lapidary-infoFrom most of the responses I've seen about it, it appears to be fairly well received. Perhaps you can get some helpful tidbits. Good luck. What are the diameters of the pulleys that drive the blade? I don't recall the exact size but around 4" on the blade and 2" on the motor. The RPM at the blade is set to 758rpm based on the RPM gauge I installed.
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Post by Rockoonz on Nov 16, 2019 12:32:04 GMT -5
If you're burning through belts while you're cutting then your motor isn't stalling, your blade is. Feed speed, blade condition, and a score of other factors could be the root cause. Knowing what brand of saw, feed type, and blade brand/type would help as far as giving advice. I have no idea what brand it is. I remember a plaque that said something like slab master or master slabber but I never could find anything online and I have since painted over it. The feed rate is roughly 6 inches per hour. The blade is MK 301 18". Feed type is carriage power feed powered by a belt linked to a 4rpm motor. The belt has burned through several times (it is a connector nylon link belt) when the blade locked up as well as once which stopped the blade and motor. Blade condition seems good because it is mostly new and has only cut about 75 slabs of red jasper and hematite/dinosaur gem bone. I don't know how I missed this, I see a definite issue. The link belt. Due to it's construction link belt provides a lot less surface contact to the pulleys, and stretches rapidly. I use it for driving the arbors on cab grinders and on the feed for my old Highland Park saws, but never to drive a saw blade. I have tried them and they slip every time. Also the tension required to cause them to slip less is hard on the blade arbor bearings. I use the Gates green belts exclusively for saws, they are designed for the belt drives on lawn tractors, quite durable and they are less likely to slip.
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Post by arghvark on Nov 19, 2019 10:40:01 GMT -5
If you're melting belts I'd look at belts and reducing drag before changing motor. My 18" cuts large, hard material with a 3/4 hp non-cap motor (including stop/restart) with no issues. It has two cheap v-belts with low tension. (The feed belt has a tensioner arm with pulley that I wasn't able to keep in position so I just hang a jug with 3/4 gallon of water from the tensioner arm. This seems to provide adequate tension since the belt never gets hot.) Agree with Lee Rockoonz , a solid belt should provide better grip than a link belt, affording less slip with lower tension. Drag: Keeping the blade well dressed can reduce drag quite a bit. If you have access to it, obsidian is an excellent blade dresser. I just run a few slabs of obsidian after each few slabs of hard stuff. Blade thickness also affects drag, so if you have a thick blade, keeping it well dressed will be even more important. Feed speed also has a big affect on drag as well as noise level. My 18" has a 3-step pulley to drive the feed gearbox. I use the lowest speed for hard stuff and the highest speed for obsidian. (I've tried higher speed on agates/jaspers. It seems to cut just fine, but is MUCH louder, sometimes setting up super annoying, neighbor-angering high-pitch resonance and the cuts are noticeably rougher.) Argh
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carver
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Member since November 2019
Posts: 36
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Post by carver on Nov 21, 2019 1:17:12 GMT -5
Thanks everyone for the suggestions. I will stop using the link belt, which means I will need to install a tensioner as the lack of tensioner and quite factor was the reason I used the link belt. I may also try increasing the pulley size on the motor and arbor shaft so there is greater surface area to grip and as long as they are kept at the same ratio I wouldn't think this would cause any issues because the speed of the arbor would be the same. My powerfeed currently uses the common 4RPM Dayton gearbox motor which I am going to make inactive by removing the clamping nut. Instead, I am going to drill a small hole on the back of the saw housing and using a pulley and cable attached the carriage with a weight hanging off the back of the saw that way the powerfeed doesn't power too much and can be kept at a constant force so larger and harder stones are not an issue. Thanks again everyone that chimed in.
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