KMG style grinder upgrade help

timos-

Knifemaker / Craftsman / Service Provider
Joined
Oct 22, 2012
Messages
2,118
Hi All,

Ok last year I ordered a VFd only to find out that I had a 1 phase 1.5 HP grinder, I could not quite swing a new motor at the time so I returned it.
Well here I am again, looking to get the most out of the ceramics belts I buy.
I think I have purchased the correct set up. I have read and read and read old threads and I think this will make a good team. But still not positive! LOL. I am just asking here to make sure im not ordering the wrong stuff again.

I am going from a step pulley mounted that is attached with a large v belt to motor under the bench/ almost on the floor. I think my horrible belt efficiency is related to this and a huge loss of torque under pressure. So with this set up I will now have a direct drive VFD and still be able to plug into 110V. I got the lower RPM motor to have increased torque.

Another issue I may have is my drive wheel. I made it myself quite awhile ago. Its a 5" diameter solid aluminum 4" wide. . Would extra mass in the drive wheel have any negative consequence? Should I machine out some weight to this?

So this is what I have ordered.
1.5HP 1725RPM 56 3PH 208-230/460V TEFC LEESON ELECTRIC MOTOR #116759
-and-
KB Electronics, 9520, KBAC-27D (Gray), 1.5;2HP, 1-Phase, 110-120V;200-240V (Input), Nema 4X Enclosure, Variable Frequency Drives
 
That motor and VFD will work fine.

The drive wheel you have is also fine. As long as it is balanced and concentric, more mass makes it run smoother.
 
thanks Stacy, I am relieved...now just gotta reconfigure the motor mount and back support plates as well as wire the thing correctly and I am hoping a 10" chef knife will no longer cost me 60-70$ in abrasive belts!
 
You will want to use the double hertz set up on the vfd. A 5" wheel will only give you about 22-2300 sfm at 17-1800 rpm.
That is nowhere close to optimum speed for ceramics on hardened steel.
Getting the most from ceramics(36-60 grit) boils down to two things. 1. The speed and power of your machine. 2. Your ability to apply enough pressure while grinding fast.
 
thanks Stacy, I am relieved...now just gotta reconfigure the motor mount and back support plates as well as wire the thing correctly and I am hoping a 10" chef knife will no longer cost me 60-70$ in abrasive belts!
How are you going to Couple the motor shaft to the drive wheel shaft? The two choices are a pulley system or a "Lovejoy" coupling. I would highly recommend the Lovejoy coupling smooth power transmission no belt headaches.
 
I'm sure his plan is to mount the motor in such a way the shaft will be at the right spot to mount drive wheel direct. The motor base is bolted to the bottom base of grinder. This allows a nice way to adjust the motor so the tracking is exact. It some aspects a base mounted motor is more flexible than a face mounted motor.
 
Yes, I was going to mount the motor shaft direct to the drive wheel.
 
thanks Stacy, I am relieved...now just gotta reconfigure the motor mount and back support plates as well as wire the thing correctly and I am hoping a 10" chef knife will no longer cost me 60-70$ in abrasive belts!
I think your combination 1800 rpm/5" wheel is to slow for ceramic belts , even on double speed is on limit for speed needed for ceramic belts ..........
 
Well, I can take down my drive wheel to 4". I wanted the higher torque so that I can apply higher pressure. I figured the 1.5 HP motor may bog down with the higher RPm motors.

I figured out that my current setup is so horrible because when ever I apply high pressure the belt slows down so that I was never able to maintain high speed.
 
If you use 4" drive wheel you will slow down belt speed even more . What HP motor you use in your current setup ?
 
Well, I can take down my drive wheel to 4". I wanted the higher torque so that I can apply higher pressure. I figured the 1.5 HP motor may bog down with the higher RPm motors.

I figured out that my current setup is so horrible because when ever I apply high pressure the belt slows down so that I was never able to maintain high speed.
Most probably you have belt slips ...try this , mark ALL wheels on your grinder , just like they are wheels on belt timing system on your car . Start grinder , run for while , turn off and check timnig /mark/ they should be OK /aligned .Then start grinder again and put that high pressure to feel that belt slow down .Turn of your grinder and check alignment of wheel again .If they mismatch ..........
 
I agree, either your current drive belt, or abrasive belt is slipping.
I don't agree that "timing" marks will work on the wheels. It might if youre drive and tracking are the same diameter.
You're not going to easily stall a 1.5 hp motor. Maybe if the motor is rated in Shetland ponies.
 
I agree, either your current drive belt, or abrasive belt is slipping.
I don't agree that "timing" marks will work on the wheels. It might if youre drive and tracking are the same diameter.
You're not going to easily stall a 1.5 hp motor. Maybe if the motor is rated in Shetland ponies.
It is mission Impossible to stall motor !
My first grinder was two wheel /drive wheel is 22cm/ and have about 32m/s. Have gas tension 30lb + about 10-12lb steel spring tension, together over 40 lbs /?/ tension .With 40 grit ceramic belt removes steel as crazy /that I was thinking/......... Then I made another grinder WITH ratchet mechanism ........And after the first contact of steel with belts I felt difference .HUGE difference !New one grind faster on same speed ????? Then I check my first grinder....BELT SLIPPING !!
 
I agree, either your current drive belt, or abrasive belt is slipping.
I don't agree that "timing" marks will work on the wheels. It might if youre drive and tracking are the same diameter.
You're not going to easily stall a 1.5 hp motor. Maybe if the motor is rated in Shetland ponies.

They would work..... To get on Ducati Multistrada bike timing belt on mark you must turn engine 7 or it was 8 full circle /forget/ of crankshaft . On grinder will be some pattern/no matter of wheel size / something like on this sketch...Easy way is to look backside of belt , if text labels is erased , belt is slips .
XeeatT9.png
 
you guys are brilliant. yes, its belt slips big time. the writing on the backside of belts is quick to disappear. I am hoping to alleviate this problem by going to direct drive. I do have a 20lb gas piston for tension.
The motor I have now is 1800rpm 1.5HP motor Leeson Farm grade but is only 1 Phase so wouldnt work with VFD. I have been using a 3 step pulley I got from Beaumont Metal Works.
Now even if my motor is not optimum speed for the ceramic belts I am hoping I will still see a huge change in performance by going from the belt/pulley to direct drive, no?

Ideally I will have a 3HP motor and a KBAC29 VFD with 240V but that is still a ways off for me.
 
Now even if my motor is not optimum speed for the ceramic belts I am hoping I will still see a huge change in performance by going from the belt/pulley to direct drive, no?

I don t want to disappoint you , but no ! You will not see huge /if any at all / change in performance .Performance come from speed and pressure on belt ................. maybe if you solve the problem with slip .But real thing believe me is ratchet mechanism ....best tracking and no slip belts anymore :thumbsup:
 
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Yep, speed and pressure are key to long lasting ceramics.
I also don't think direct drive is going to help if your abrasive belt is what's slipping. 20 lb gas spring is plenty if it's positioned right.
Can you post a pic of your machine?
 
The VFD should be here today. Ive got the motor already, I will exchange it if I have too.
Do you guys have a better motor rec. ? Should I get my hands on a bigger drive wheel?

I dont have a very good picture at the moment but this weekend I will be getting into the upgrade. I mostly run a hardened d2 flat platen.
i7J12da.jpg
 
I don t know if I can help .I don have enough data to calculate . On one of my motor I have this data on plate......on 50 Hz motor have 2790 rpm/min , on 60 Hz have 3380 rpm/min .So 10Hz give 590 rpm more .......If this go linear up ...I mind if motor on 70 Hz run 3970 rpm/min ( 3380+590) .And IF all this apply if we decreasing Hz .... it is easy to calculate which drive wheel and speed you need to get ALL in one ..if it is possible ? I have no experience with fine grain belts so which is slowest speed you will need for some task I can t know ...
On this link is very easy to calculate belts speed if you know Rpm and Dia. of drive wheel .
https://www.blocklayer.com/pulley-belt.aspx
 
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