Critique Requested for 11 Pound Water Cooled VFD Motor in Testing on 2 x 72 Grinder

BelnapCustomKnives

BelnapCustomKnives

Joined
Oct 30, 2015
Messages
139
I have been working on a compact sander frame for a while and part of that is a compact drive. After some study I selected a water cooled, 3HP, 3PH, 220 Volt, 400HZ, 24,000 rpm, 11 pound spindle motor to test. Before the switch in your brain turns to the NOT POSSIBLE position it is already a reality and not just a drawing board discussion.

The target top belt speed was 7000 SFPM and the motor had to be able to pull under the heavy pressure that a Multi Guide bevel guide applies to the belt. After more than 30 blanks ground at 5000 - 7000 SFPM in both hollow and flat grind the motor has proven that it is well capable of performing under these conditions. It also has demonstrated that it is very capable at performing the low speed grinding tasks typically performed during knife finishing.

These motors and drive are not expensive to buy new. I bought the entire package required to run the motor for $350.00 on ebay. Making a special drive assembly cost another $250.00 for prototype parts to be machined. That is pretty low. I am confident that there is not a conventional VFD solution that can match this one in terms of performance and price.
I have tested the motor and drive through most of the operations that I use my sander for during knife making operations. I would be interested in hearing what operations other knife makers might like to see tested on this drive.

Also I would invite those with real knowledge in this particular area to constructive critique the demonstrated performance, and the design as shown in the development videos in the playlist below.

https://m.youtube.com/playlist?list=PLthW154g2QNNalPz0XA4gVKsJLoQe8Mpo
 
I am familiar with water cooled spindle motors for cnc routers and mills, and plan to add one to my cnc mill as a piggyback spindle for high speed engraving. I am also familiar with using 3ph motors along with VFDs for tools as they offer me high torque and variable speed, capable of exceeding that of the original motor rating.
I am curious why go the route of a water cooled spindle motor (the water cooling is a PITA IMO) for a 2x72 grinder when an 1800rpm 3ph motor with a VFD will do the job
just fine. Whats the advantages of one over the other?
 
I personally would pass on this. After have one of those exzact drives literally explode on me. And taking over a month to get a replacement im not a fan. Mine was a 10hp drive as well, yes it was driving a 10hp motor. But I was assured 100% from the manufacture it would handle it no problem. My big question is how is the torque at low SFP. A lot of us run our grinders slow as we start finishing. Trust me I was in the HIGH SFPM mind set when I first started. My grinder would max out at around 10,000SFPM. I thought it was perfect and did not listen to everyone else telling me to slow down. I finly headed there advise and dropped to around 4500sfm max and I could not be more then happy with it. Im not saying I would not own another 10,000SFPM machine but it would be specially designed with 3-5hp motor and a large contact wheel. If your going after the small grinder market I think your a tad late to the show as travis has been perfecting a really nice little grinder. If you don’t know who he is, he is the man behind the TW90. As soon as he releases his little mini I’m going to jump on it. One big issue I can see is the vfd that I mentioned but also the water cooled. Most of us don’t heat our shops so how does freezing weather affect a water cooled spindle?
 
JT hit the nail on the head - why? "IF" you really want a 7,000 SFPM grinder then use am 1800 with 2X jumper, or a 3450 rpm motor with the 1X jumper along with an 8" drive wheel then you've got 7,000 SFPM speed without all the extra parts and with MUCH more torque at lower speeds. And, once you get tired of 7,000 SFPM speeds, you can change to a 5" or 6" drive wheel and have decent slow speed torque. I realize low speeds doesn't require much torque because you're not using lots of pressure at this point.

Those 24,000 rpm spindle motors work great for their designed purpose.
JT, was that a CNC mill you were using the 10hp spindle motor with? That's more than a "desktop" mill for sure.
 
I think it's a horrible idea myself to be perfectly honest.
Look at what a reputable name brand spindle motor costs in comparison to that thing? Hell just a good conventional drive would cost more than that whole setup. You know major corners had to be cut.
I'll be surprised if it doesn't blow up eventually.
Needlessly complicated, an obvious sacrifice of reliability, and for no benefit. This honestly sounds like one of the things you see in beginners groups on Facebook where people are too cheap to buy a proper tefc motor and KB drive.
If I wanted higher speed (my grinder runs from 1100 to 5600 sfm, and I run it wide open for ceramic belts) I would be going the opposite direction from what you have, and use a large drive wheel. A big thing turning slowly will always be more reliable and durable than a tiny thing spinning stupid fast. I'm sure this thing will work great for you, until it let's the magic smoke out or blows up like a grenade.
 
JTknives said:
I personally would pass on this. After have one of those exzact drives literally explode on me. And taking over a month to get a replacement im not a fan. Mine was a 10hp drive as well, yes it was driving a 10hp motor. But I was assured 100% from the manufacture it would handle it no problem. My big question is how is the torque at low SFP. A lot of us run our grinders slow as we start finishing. Trust me I was in the HIGH SFPM mind set when I first started. My grinder would max out at around 10,000SFPM. I thought it was perfect and did not listen to everyone else telling me to slow down. I finly headed there advise and dropped to around 4500sfm max and I could not be more then happy with it. Im not saying I would not own another 10,000SFPM machine but it would be specially designed with 3-5hp motor and a large contact wheel. If your going after the small grinder market I think your a tad late to the show as travis has been perfecting a really nice little grinder. If you don’t know who he is, he is the man behind the TW90. As soon as he releases his little mini I’m going to jump on it. One big issue I can see is the vfd that I mentioned but also the water cooled. Most of us don’t heat our shops so how does freezing weather affect a water cooled spindle?
Click to expand...
Thanks for the feedback.
 
Geoff Flato said:
I think it's a horrible idea myself to be perfectly honest.
Look at what a reputable name brand spindle motor costs in comparison to that thing? Hell just a good conventional drive would cost more than that whole setup. You know major corners had to be cut.
I'll be surprised if it doesn't blow up eventually.
Needlessly complicated, an obvious sacrifice of reliability, and for no benefit. This honestly sounds like one of the things you see in beginners groups on Facebook where people are too cheap to buy a proper tefc motor and KB drive.
If I wanted higher speed (my grinder runs from 1100 to 5600 sfm, and I run it wide open for ceramic belts) I would be going the opposite direction from what you have, and use a large drive wheel. A big thing turning slowly will always be more reliable and durable than a tiny thing spinning stupid fast. I'm sure this thing will work great for you, until it let's the magic smoke out or blows up like a grenade.
Click to expand...
Thanks. Planning to find out what it will take to kill it.
 
Ken H> said:
JT hit the nail on the head - why? "IF" you really want a 7,000 SFPM grinder then use am 1800 with 2X jumper, or a 3450 rpm motor with the 1X jumper along with an 8" drive wheel then you've got 7,000 SFPM speed without all the extra parts and with MUCH more torque at lower speeds. And, once you get tired of 7,000 SFPM speeds, you can change to a 5" or 6" drive wheel and have decent slow speed torque. I realize low speeds doesn't require much torque because you're not using lots of pressure at this point.

Those 24,000 rpm spindle motors work great for their designed purpose.
JT, was that a CNC mill you were using the 10hp spindle motor with? That's more than a "desktop" mill for sure.
Click to expand...
Thanks
 
Belnap, I commented before watching this video - I watched the first one you put made with this grinder. While I don't see the reason for the CNC spindle motor, please do allow me to compliment you on how smooth and straight the grinder tracks. You surely did a good job of getting it all lined up. Have you tried it in reverse yet?

Good job on building.
 
The 10hp motor was on my press. I actualy just received the replacement yesterday and it going on my surface grinder which is only 3hp. These VFDS serve double duty thy can be programmed up to 400hz. I’m not going to say thy are bad becaus thy actualy are ok for the price. But having one blow up left a real sour taste in my mouth. But I would fallow the advise I was give by the electricians at my work. Get a vfd rated for twice the size as the motor your running.
 
JTknives said:
I personally would pass on this. After have one of those exzact drives literally explode on me. And taking over a month to get a replacement im not a fan. Mine was a 10hp drive as well, yes it was driving a 10hp motor. But I was assured 100% from the manufacture it would handle it no problem. My big question is how is the torque at low SFP. A lot of us run our grinders slow as we start finishing. Trust me I was in the HIGH SFPM mind set when I first started. My grinder would max out at around 10,000SFPM. I thought it was perfect and did not listen to everyone else telling me to slow down. I finly headed there advise and dropped to around 4500sfm max and I could not be more then happy with it. Im not saying I would not own another 10,000SFPM machine but it would be specially designed with 3-5hp motor and a large contact wheel. If your going after the small grinder market I think your a tad late to the show as travis has been perfecting a really nice little grinder. If you don’t know who he is, he is the man behind the TW90. As soon as he releases his little mini I’m going to jump on it. One big issue I can see is the vfd that I mentioned but also the water cooled. Most of us don’t heat our shops so how does freezing weather affect a water cooled spindle?
Click to expand...
Was there specific reason you did not like the high speed grinding capability of your machine? Why were people telling you to slow down? 3M recommends operating many of their belts at 7000 - 8000 SFPM and I have found that operating these slower reduces their performance. I did use antifreeze in the spindle during freezing weather to prevent damaging the motor. I am familiar with Travis but have never met him. I do sell many of my bevel guides Multi Guide Pro to owners of the TW-90 in USA and Canada. I did not select this motor because of complete lack of experience. I had a 5HP that was driving my machine. The compact frame I am working on is not the same as the mini that Travis is developing.
 
Ken H> said:
Belnap, I commented before watching this video - I watched the first one you put made with this grinder. While I don't see the reason for the CNC spindle motor, please do allow me to compliment you on how smooth and straight the grinder tracks. You surely did a good job of getting it all lined up. Have you tried it in reverse yet?

Good job on building.
Click to expand...
Thanks. I had a 5 HP motor driving previously and understand that system. I am designing a compact frame machine and am looking for a light weight full performance drive. Mostly research to see if this motor will do it and how long it will survive doing it. So far it is doing an amazing job and only showing strengths. That is why I posted here to see if other had additional ideas on how I could test the motor/drive to try and identify weakness and failures.
 
Jonathans said:
I am familiar with water cooled spindle motors for cnc routers and mills, and plan to add one to my cnc mill as a piggyback spindle for high speed engraving. I am also familiar with using 3ph motors along with VFDs for tools as they offer me high torque and variable speed, capable of exceeding that of the original motor rating.
I am curious why go the route of a water cooled spindle motor (the water cooling is a PITA IMO) for a 2x72 grinder when an 1800rpm 3ph motor with a VFD will do the job
just fine. Whats the advantages of one over the other?
Click to expand...
Hi, Thanks for commenting. size, weight, performance. Have not seen a drive that can go from near zero to 7000 SFPM without changing wheels for this low cost. Total cost has been $600.00 so far for the complete setup on the machine and running. This drive is being developed for a compact frame 2 x 72 I am working on. A comparable conventional 3 ph, 3 hp motor is about 48 pounds. This one is 11 pounds and so far is performing all of the jobs my previous 5 hp was doing equal to or better than. It runs much smoother and quieter than the 5hp.
I debated on the water cooled vs the air cooled version. Decided to try the water cooled first because it was quieter than the air cooled motor. Not much of a reason I know.
 
It’s not that I did not like the high speed, it was that it came at a reduced torque penalty. With fresh sharp belt yeah it hauled ass but once the belts started to wear and you needed to really lean on the steel the grinder would have issues. So like I said if I could have say a true 5hp and go from about 1000sfpm up to around 9000sfpm it would be perfect. But the other issue is vibration and noise level has a tendency to go way up when in the higher ranges. I love a quiet grinder. So maybe your on to something if it truly has low sfpm preformance. I’m going to be building another grinder soon and had planned on it being a smaller grinder set up like travis mini. Would just be for hallow grinding. But my design requires a motor that’s stout enough to support the entire grinder on the shaft. But I could see potential for a high HP hogging grinder that is wicked smooth. It could even be set at one SFPM and just left there as it would be duty specific.
 
BelnapCustomKnives said:
I have been working on a compact sander frame for a while and part of that is a compact drive. After some study I selected a water cooled, 3HP, 3PH, 220 Volt, 400HZ, 24,000 rpm, 11 pound spindle motor to test. Before the switch in your brain turns to the NOT POSSIBLE position it is already a reality and not just a drawing board discussion.

The target top belt speed was 7000 SFPM and the motor had to be able to pull under the heavy pressure that a Multi Guide bevel guide applies to the belt. After more than 30 blanks ground at 5000 - 7000 SFPM in both hollow and flat grind the motor has proven that it is well capable of performing under these conditions. It also has demonstrated that it is very capable at performing the low speed grinding tasks typically performed during knife finishing.

These motors and drive are not expensive to buy new. I bought the entire package required to run the motor for $350.00 on ebay. Making a special drive assembly cost another $250.00 for prototype parts to be machined. That is pretty low. I am confident that there is not a conventional VFD solution that can match this one in terms of performance and price.
I have tested the motor and drive through most of the operations that I use my sander for during knife making operations. I would be interested in hearing what operations other knife makers might like to see tested on this drive.

Also I would invite those with real knowledge in this particular area to constructive critique the demonstrated performance, and the design as shown in the development videos in the playlist below.

https://m.youtube.com/playlist?list=PLthW154g2QNNalPz0XA4gVKsJLoQe8Mpo
Click to expand...

I like what you done .With help from my friend in his shop we are half away in building CNC grinder/8000SFPM/ and I was thinking to use same motor as yours .My friend manufacturing big 4x2 meters CNC router for furniture factories and he use this kind of motor,China made . He sell many router and have no complain from user about this spindle motor ....But I give up from this kind of motor .First reason was NOISE .................well that thing/motor/ is really LOUD on high RPM and I live in very urban environment ...... Second reason was drive wheel .........considering that motor have very high RPM must be used very small drive wheel and I was concerned that belt would slip on drive wheel , small contact area on drive wheel with belt .But now I see that small drive wheel can work... you have now put me in doubt .maybe i will use spindle motor :) My current belt grinder /two wheel and 2x42 inch belt / run on 6450 SFPM and I like it ...................
Today I start to work on another small grinder /2x42 belt/ will run in range of 2000/ 8400 SFPM ........ + small wheel and max. 12 inch wheel attachment ;)
AhCgjpH.jpg


I think that you wasting time talking with guys here about high speed grinder ... :Dthey don t like screaming fast grinder .........I have no idea why :(
Thank you for showing your grinder ..........:thumbsup:
 
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I love a fast grinder, and have nothing against it provided speed doesn't come at the cost of reliability, tracking, or being smooth and quiet. Its the chinese spindle motor I don't like about this. For what its worth, I do plan on building a grinder that will go to 7-9000 at some point, but it will have a conventional 5 or 7.5hp motor driving it.

You'd never see high speed motors used for this in industry. And there is a reason for that.
 
Geoff Flato said:
I love a fast grinder, and have nothing against it provided speed doesn't come at the cost of reliability, tracking, or being smooth and quiet. Its the chinese spindle motor I don't like about this. For what its worth, I do plan on building a grinder that will go to 7-9000 at some point, but it will have a conventional 5 or 7.5hp motor driving it.

You'd never see high speed motors used for this in industry. And there is a reason for that.
Click to expand...

Why you need 5Hp motor ? I run 2hp motor on 2800 rpm and 8.6 inch aluminium drive wheel and have 6450 SFPM . Even HULK can not stop that thing ............In USA you have 3450 rpm motor , with 8.6 inch wheel will run almost 8000 SFPM ........and nothing can stop that ?
 
Geoff Flato said:
I love a fast grinder, and have nothing against it provided speed doesn't come at the cost of reliability, tracking, or being smooth and quiet. Its the chinese spindle motor I don't like about this. For what its worth, I do plan on building a grinder that will go to 7-9000 at some point, but it will have a conventional 5 or 7.5hp motor driving it.

You'd never see high speed motors used for this in industry. And there is a reason for that.
Click to expand...
That s way I build mine two wheel grinder and use 2x42 belt .Just for rough grinding with 40/60 ceramic belt . Drive wheel is from aluminium and 8.6 inch /give high torque / and tracking wheel is 4.7 inch ...perfect tracking and low noise .My tracking wheel /4.7 inch/ run on 5100 rpm . You use small wheel /two inch/ and if i use them they will spin on 12320 rpm :eek: and make noise like F-16:)
 
Trust me you can. I could stall out my 9000sfpm 2hp grinder, that’s why I dropped the rpm so I could bump if the torque. It all comes down to surface area. If your just profiling thin blade steel then it’s hard but as soon as you move from a wheel to a platten and start flat grinding then it’s a different ball game. Geoff maybe something like this bad boy, 7.5hp Baldor. Got it for free becaus the bearing where shot. $15 and she is good as new, would make a hell of a grinder lol
Photo%20Mar%2010%2C%202%2022%2011%20AM.jpg
 
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