kmg direct drive?

cbr900son

cbr900son

Joined
Mar 3, 2011
Messages
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Anyone ever hooked their kmg up as a direct drive. Maybe using a jack shaft or something?
 
I thought I understood the question, but if you're using a jack shaft, to me that means shaft, bearings, belt, and pulleys

It wouldn't be direct drive any more.



I've considered it.

Since it's all bolted together, you could remove the back 2 plates the bearings are mounted on and replace that plate with a larger one
motor cut-out and mounting holes.

You may have to use a thinner plate or screw with spacer thickness's to line up the wheels.
 
Yeah I was thinking direct drive or even a shaft to connect the motor shaft to the back shaft in the pulleys. Dunno exactly was just kind iof a idea that just popped in my head.
 
My KMG with a variable speed DC motor (1750 rpm) uses a pulley set-up that looks like it has about a 3:1 step up ratio. Unless, you had a very fast motor, you might not be able to get the faster belt speeds needed for some operations. In short, your belt may not turn fast enough without drastically changing the diameter of your main drive roller.

Mike L.
 
You could just mount a drive wheel to the motor and place it on the right side of the KMG and get the motor to spin clockwise
 
Instead of a pair of plates in the back with flange bearings mounted on them you could use a single plate, take the dimensions for the mounting holes for a direct drive motor from the EERF grinder plans and adapt them to the new single plate for the direct drive KMG clone.
 
woodwrkr221 said:
Instead of a pair of plates in the back with flange bearings mounted on them you could use a single plate, take the dimensions for the mounting holes for a direct drive motor from the EERF grinder plans and adapt them to the new single plate for the direct drive KMG clone.
Click to expand...

I am currently in the process of doing the above (great minds)and building a GIB; I have not been happy with the pulley and belt set-up on the KMG.
 
Well I have a vfd so didnt even think of how the pulleys would complicate things. I think Im gonna have to bust out the lathe and mill and work something out. Worst come to worst it will be a learning experience.
 
In the air conditioning business (my profession) direct drive is very much preferred over belt drive when possible because of the belt maintenance and pulley alignment problems. A direct drive KMG makes a lot of sense to me. Good luck with your builds, wish I had the $$$.
 
Perhaps a simpler way to change to direct drive ( instead of taking apart and modifying the KMG) is to just remove the pulley and replace it with a motor coupling. Then the motor can be installed easily. It will also make for a smoother running unit vibration-wise and sound-wise.
Here is one similar to what I am referring to:
http://www.ebay.com/itm/LOT-3-FENNE...146?pt=LH_DefaultDomain_0&hash=item35b62157ba
 
bladsmth said:
Perhaps a simpler way to change to direct drive ( instead of taking apart and modifying the KMG) is to just remove the pulley and replace it with a motor coupling. Then the motor can be installed easily. It will also make for a smoother running unit vibration-wise and sound-wise.
Here is one similar to what I am referring to:
http://www.ebay.com/itm/LOT-3-FENNE...146?pt=LH_DefaultDomain_0&hash=item35b62157ba
Click to expand...
That is exactly what I was thinking!!!! OMG you saved me some time! I was actually in cad making designs for almost the same thing lol. Now to find one with 5/8 and 3/4" shaft sizes!!

Can yall see any reason not to drill out a 1" bar 3/4 on one side 5/8 on the other and just tap 2 holes for set screws to fit in the keyway? They have some premade for around 50$ but hell I got a mill and lathe and havnt had a good excuse to play with the lathe yet! Just wondering if anyone thinks for some reason the set screw idea would be bad.
 
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Well, from an engineering point of view there is the problem of alignment. Even a fraction of a percent out of straight alignment will cause a huge vibration. Even if the noise and vibration isn't all that serious, the lateral force applied to the bearings on the motor and grinder will cause extreme wear, resulting in premature failure.
The shaft couplings like I linked to have a non-metallic "spider" ( often a hard rubber or plastic) that mates the two pieces attached to the two shafts.
Check your local pump or industrial supplier, they carry them in all sizes. At worst, you might have to buy one of each size and make two 5/8-3/4 pairs. Call the seller to check, but from what I have seen you can mix and match the pieces.
 
bladsmth said:
Well, from an engineering point of view there is the problem of alignment. Even a fraction of a percent out of straight alignment will cause a huge vibration. Even if the noise and vibration isn't all that serious, the lateral force applied to the bearings on the motor and grinder will cause extreme wear, resulting in premature failure.
The shaft couplings like I linked to have a non-metallic "spider" ( often a hard rubber or plastic) that mates the two pieces attached to the two shafts.
Check your local pump or industrial supplier, they carry them in all sizes. At worst, you might have to buy one of each size and make two 5/8-3/4 pairs. Call the seller to check, but from what I have seen you can mix and match the pieces.
Click to expand...

Thats is what im thinking
 
bladsmth said:
Perhaps a simpler way to change to direct drive ( instead of taking apart and modifying the KMG) is to just remove the pulley and replace it with a motor coupling. Then the motor can be installed easily. It will also make for a smoother running unit vibration-wise and sound-wise.
Here is one similar to what I am referring to:
http://www.ebay.com/itm/LOT-3-FENNE...146?pt=LH_DefaultDomain_0&hash=item35b62157ba
Click to expand...

But . . . without changing the diameter of of the belt's drive roller, you would need a motor that runs at approximately 3 x 1750rpm = 5,250 rpm in order to achieve maximum desirable belt speed.

Mike L.
 
I hope you mean 5250 SFPM,....I would leave the room if someone was running a standard belt grinder at 5200 RPM.
With a 6" drive wheel, that would be 8100 SFPM, with a 4" wheel it would be 5500 SFPM.

If I understood the OP's question, it was to direct drive the KMG drive wheel with the motor and to use a VFD to control the motor. That will give you speeds from 0 to the full speed of the VFD ( approx. 150-200% of motor rating speed). So, with a 1750 RPM motor running a 6" drive wheel at 100% you would get a belt speed of 2750 SFPM. At full 200% VFD output, it would be 5500SFPM. Above that you will need a coolant flooded belt to keep from burning the steel and frying the belt.
 
Stacy,

I think you have mis-understood me, or I'm not being clear enough.

The standard drive wheel on a KMG is 3.875" diameter. I don't propose running a motor over nameplate rated rpm, so I'll assume a maximum motor speed of 1750 rpm.

A direct drive KMG with the standard 3.875" drive roller will produce a maximum belt speed of 1,775 ft/min.

Yet, a desired maximum belt speed would be somewhere around 3500 ft/min. To achieve this, the drive roller diameter would need to be changed to about 7-5/8", which is huge.

That is all that I'm trying to say. I'll leave it at that.

Mike LoGiudice
 
logem said:
Stacy,

I think you have mis-understood me, or I'm not being clear enough.

The standard drive wheel on a KMG is 3.875" diameter. I don't propose running a motor over nameplate rated rpm, so I'll assume a maximum motor speed of 1750 rpm.

A direct drive KMG with the standard 3.875" drive roller will produce a maximum belt speed of 1,775 ft/min.

Yet, a desired maximum belt speed would be somewhere around 3500 ft/min. To achieve this, the drive roller diameter would need to be changed to about 7-5/8", which is huge.

That is all that I'm trying to say. I'll leave it at that.

Mike LoGiudice
Click to expand...


Any of the commercially made direct drive grinders I see are running 3400 rpm motors.

Bader, Wilton Square wheel,

The KMG with the 3 stepped pulley gets that on high speed with a 2:1 pulley ratio on a 1700 rpm motor


The commercially made direct drives I've seen also have 6" or larger drive wheels too.
3.14 x 6 x 3400 /12
5338 sfpm
 
bladsmth said:
Perhaps a simpler way to change to direct drive ( instead of taking apart and modifying the KMG) is to just remove the pulley and replace it with a motor coupling. Then the motor can be installed easily. It will also make for a smoother running unit vibration-wise and sound-wise.
Here is one similar to what I am referring to:
http://www.ebay.com/itm/LOT-3-FENNE...146?pt=LH_DefaultDomain_0&hash=item35b62157ba
Click to expand...

Good idea bladsmth. That certainly would be simpler for an existing machine.

If someone (myself for instance) were building a KMG clone from the drawings available I think I would prefer the 56C frame motor and mounting plate similar to the GIB, this would eliminate the shaft, flange bearings and flex coupling. If everything were well made, balanced and aligned vibration shouldn't be much of a problem.

But for an existing machine, definitely the flex coupling.
 
AVigil said:
You could just mount a drive wheel to the motor and place it on the right side of the KMG and get the motor to spin clockwise
Click to expand...

What a good idea :)

Seriously though if you want to get to it and not screw around. Just put the motor on the same side as the other wheels and mount the drive wheel to it. Bolt it to the table and get your rotation going in the right direction and you are set.
 
I understand your statement now ,Mike.

Unless they have changed the wheels on KMGs they come in 4" and 6". Direct drive is only of use when running a VFD. The RPM on the motor plate are for 60 hertz operation. If running the VFD at higher frequency, the speed increases. Most charts use 200-300% as the max suggested rate.
Using a direct drive with a 6" wheel, on a 1750 RPM 3Ph motor and a VFD will make the KMG belt run at normal grinder speed. If you get a 3400RPM motor, like the Count says, it will run at full speed and not exceed the plate rating.
 
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