Converting a KMG to direct drive...?

With the dual tool arm slots, it doesn't block the tool arm. :)


Also, most of my tool arms are 18" and not 24", simply because they don't need to be that long. I have three tapped holes per tool arm slot, and at least one of them will grab an arm,no matter how short it is.
 
There's been a handful of these kits that have made their way to folks, at this point, and a couple tidbits that were beyond my ability to observe have been pointed out.

Although I mentioned it in the original announcement post in this thread, it seems to have been overlooked, and this is critical : THE KIT REQUIRES THAT YOU HAVE A 56C FACE MOUNT motor. The motor bolts to the adapter, and without the face mount, it ain't gonna work.

Also, guys have said that they had to cut the length of some of their tool arms down, as the adapter bracket won't allow a tool arm to stick past it. I didn't notice this on my own grinder, because I added the additional tool arm slot, which lets the tool arms clear the bracket in the top slot, AND I made almost all my own arms and cut them at 18". I couldn't see any advantage to making them any longer, and I could get four tool arms out of a six foot long bar. Things to keep in mind if you decide you want one of these.

Feedback has been beyond positive. Improved tracking, elimination of vibration, and gobs more torque due to the elimination of belt slip. For most, also, an increase in speed when the VFD output frequency is doubled.

Figured I ought to pass all this along for people that may want one in the future.
 
Hi Guys,

Matt was gracious enough to help me get the direct drive conversion kit for my KMG. I have been having issues with vibration, tracking and stalling so much so that I bought an Esteem. The Esteem is amazing levels above the KMG so I started looking into how to make my KMG more like the Esteem and came upon this post.

I had to make a new tilt table for the grinder so it can flip with the new motor position so it took a couple of days but the grinder is up and running and I can't be happier.

Here are a couple of notes:
- You need a 56C face motor, the KMG stock is not a c-face motor.
-1725rpm with your vfd adjusted to 2x will give you double the speed back up to 3450rpm but give you more torque.
-You will have to cut down your tooling arms with the flat platen and any wheel over 8"
-Kit comes with a 5.5" drive wheel

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Observations so far:

The KMG runs so smooth now, no vibration and belt wobble was greatly reduced and boost in speed.
Nice plunges I couldn't do before with the wobble, but now I can.
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And about Matt...

Matt is probably one of the nicest and most helpful guy I've meet in this community. He went above and beyond to help me with a couple of issues that are mainly my fault during assembly. I just can't say at how impressed I am with his kindness, he isn't making money on this, he just did it to help me out. The guy is as solid as they come.
 
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I'm looking seriously into doing this conversion on my KMG... do you guys have any recomendations for a variable speed motor and controller? I currently have the 1.5 HP Leeson but want something with a bit more grunt.
 
If you're making the conversion yourself, obviously you can use anything you want. There are countless two and three horsepower motors available that will work in this configuration. If you're talking about getting this conversion kit from my buddy Joe, then it absolutely needs to be a 56c face mount motor. I strongly suggest getting a 1700-1800 rpm motor, as it will produce more torque, and then just doubling the frequency in the vfd to increase capable speed.

I kind of think Joe may even have one of these kits available, so if you want one, email me.
 
Hey bud, if you're using the BF email system, don't. I think I get every third email through that POS.
 
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I figured I should add a bit to this, as there have been quite a few of these direct drive kits sold, now. The last one had an interesting tidbit that I thought I should share...

The pulleys were apparently a major source of vibration for this guy, so he ditched them and went 'direct drive' with a lovejoy coupling, which improved it, but didn't entirely eliminate the vibration. After much debating, he ordered this kit. He needed to order a new 2hp motor, but the kit came before the motor did. Just because he's impatient (like the rest of us!), he yanked a 1hp 3450rpm motor from another machine and stuck it on the direct drive kit - just to see.

WITH THE VFD RUNNING IN 2X MODE, he said the machine is smooth as glass.

Guys, that's just shy of 10,000 sanding feet per minute. Or, about 100mph. :eek:


I do NOT endorse doing this, as I have no idea how the belts we run can handle it, but I thought it was interesting enough to share. It's also another example of how any one component (perhaps, in this case, the drive pulley shaft or pillow blocks), can be the problem, or yet another problem, with these machines.
 
Can anyone that uses a 1725 motor and the 2x option on the KB drive comment on the torque. It has been explained that torque will be an issue and it is clear when running the numbers but how does it feel? Thanks
 
You have full torque up until 50% (which is the original max speed at 1x), but it doesn’t increase beyond that point. I think that’s where people get confused. Your speed doubles, but your torque remains consistent.

In use, I don’t find any issues, especially compared to the ridiculous slip that occurred with the shitty belt and pulley setup. I could stall the same motor with the pulley setup without even trying, and now that it’s direct drive I would have to really work at it to do it, and my grinding would be the furthest thing from safe or controlled at that point.

Perhaps my methods differ from others, but I’m only using coarse belts at high speed, and although pressure is certainly a factor, it’s speed that’s inproving material removal. Until you’ve used a ceramic belt north of 4000sfpm, you really haven’t experienced the effectiveness of these abrasives.
 
I have used a 1725 rpm 1hp motor and vfd on 2x direct drive since I started and never stalled it. If I really need to slow things down I just move the jumper, but I haven’t had to yet. Plus 3450 with a 4” drive wheel is plenty fast for me. Not sure I’ve ever gone above 75-80% on my vfd
 
Sounds like I should be ok with my 3hp motor. Looking forward to fabbing it up as well as mounting on a table with a rotating axis.
 
Matthew Gregory- A little while back I think I read about a 56 to 56c motor mount conversion made by Lesson. I remember, when I was looking to do the direct drive conversion, my problem is that my motor didn’t have the 56c mounting bracket. Do you think that mounting conversion would work?
 
Matthew Gregory said:
I figured I should add a bit to this, as there have been quite a few of these direct drive kits sold, now. The last one had an interesting tidbit that I thought I should share...

The pulleys were apparently a major source of vibration for this guy, so he ditched them and went 'direct drive' with a lovejoy coupling, which improved it, but didn't entirely eliminate the vibration. After much debating, he ordered this kit. He needed to order a new 2hp motor, but the kit came before the motor did. Just because he's impatient (like the rest of us!), he yanked a 1hp 3450rpm motor from another machine and stuck it on the direct drive kit - just to see.

WITH THE VFD RUNNING IN 2X MODE, he said the machine is smooth as glass.

Guys, that's just shy of 10,000 sanding feet per minute. Or, about 100mph. :eek:


I do NOT endorse doing this, as I have no idea how the belts we run can handle it, but I thought it was interesting enough to share. It's also another example of how any one component (perhaps, in this case, the drive pulley shaft or pillow blocks), can be the problem, or yet another problem, with these machines.
Click to expand...
I use Klingspor ceramic belt 50 x 1020mm. length and before I took out my VFD from that belt grinder I run maybe several hours in total on over 55m/s . I did not notice that there was some problem on that speed.Tension on belt on that grinder is over 15kg ............Without VFD I use them at 31 m/s .... no breaks or any damage till now .
 
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