problems with home built grinder.

S

SixKnives

Joined
May 16, 2018
Messages
12
hey guys, new to the forum. just finished my build on my 2x72 and the grinder is awesome. however, I pulled out an old treadmill motor (2.65hp pulling around 6k rpm). I also installed an MC60 motor controller that I ordered off ebay. Initial setup and test run worked fine. I got one knife into it and the motor crapped out. I then felt the motor which was screaming hot and it appears that I fried the controller. Everything was wired per many instruction found on youtube and other forums. Im not running any choke on the controller (but I dont think thats the issue.) has this come up at all with other builders? I have orders that need to be completed and now im dead in the water. any advice is good advice.
 
One of the biggest issues with a treadmill motor is the open design and how it cools. You very well could have gotten it full of metal dust and its shorting out.
 
If you are on the home built belt Grinder group on fb, you will see my repeated attempts at reasoning with treadmill motor enthusiasts in regards to time spent setting them up vs. short lifespan. You'll also see I am repeatedly told that it's not an issue. Get a proper sealed motor so you can stop screwing around with the motor, and get to making knives.
 
I will state my standard reply:
The ONLY motor the is suitable for a grinder is a TEFC motor. The controller must be dust shielded . That can be done by mounting it in a large closed plastic box, but a NEMA4 enclosure is what you really want. A 1.5HP 220V 3Ph motor and matching NEMA4 controller will cost a bit, but will still be going strong ten years from now. A treadmill motor and cheap controller will fail sooner or later ... usually sooner.
 
Anyone who is serious about knife making will find a way to get a motor and VFD like Mr. Apelt describes above. I also would recommend that a KBAC drive be considered since it is very popular, reliable, and is enclosed in a NEMA4 enclosure with heat sink fins on the back. I have used three of them for the last ten years with no signs of problems. The vast majority of professional knife makers use TEFC motors and NEMA4 drives. Larry

]
zYmxqSGl.jpg
 
Yes....It has come up with other Home Builders cobbling together less expensive parts and yes they wind up where you are and yes they ask the same questions....Take Stacy and Larry's advice to heart the TEFC Motors and KBAC drives are designed for dirty environments where METAL and WOOD dust can cause failures. Like Larry I also have multiple TEFC motors and KBAC drives with no failures in over 10 years of service worth every penny not to be down and waiting on replacement equipment.
 
Yep, I hated biting the bullet on the KBAC 27, but its proven itself, and I know I can get sound advice from a multitude of users on this site should problems ever arise. Save up or sell something replaceable to get the proper, quality tools.
 
My first 2x72 had a treadmill motor on it. I learned real quick after 3 knives made with it why everyone recommended a tefc and vfd. I still have that grinder but it's just sitting on the bench awaiting a new motor and I have another grinder I built with a 3hp 3ph motor and kbac 29. I'll never look back.
 
Insufficient cooling may have been one issue, metal dust or debris another, or it could have just been a motor that was on its way out to begin with. Hard to say. Hopefully you didn't spend too much on any of it.

I will say one thing though: I've never missed a single dollar that I spent on my KBAC-27d VFD. Worth every penny.

You can get a 3 phase, 2HP IronHorse motor for about 175 brand new, IIRC. If you're on a tight budget, I've seen used and surplus motors for anywhere from $40 to $150. You can also get by with the $100 china VFDs if you keep then free from dust, though you will need 220VAC available. Other than that, it's mainly just a matter of switches and wires, which you may already have from your current setup.
 
I did get away with an old 1940’s or 50’s open motor when I started using step pulleys for an adjustable speed set up with my ol Coote Grinder. This motor is so old it has oil spouts for the bearings.. LOL ..—————————————————..I didn’t kill it. Still have it,, When I bought my Hardcore Products Grinder with the Bador 1 1/2hp and built it Variable control I haven’t looked back and have insisted on TEFC motor for any motor that drives a 2 x 72” or Disc Grinder in my shop!
 
The huge problem with treadmill motors is not that thy are open but that thy are DC motors that have a permanent magnet inside. This magnet will suck every little bit of of steel out of the air. Also these motors are highly over rated. By that I mean HP rating, 2.65hp on a consumer device designed to be plugged into a living room outlet. You would be lucky if it out put half that.
 
The rating on treadmill and other high RPM motors like routers and vacuums is a calculation that someone came up with that is false. They take thewattage and then multiply it by the percentage of speed over 1750. A 5000 RPM motor that creates 745 watts of power suddenly becomes a 2.85 HP "rated" motor on the box description. This might sell the items, but doesn't change the reality that they are only 1 HP.
 
knife to a gunfight said:
You can also get by with the $100 china VFDs if you keep then free from dust, though you will need 220VAC available.
Click to expand...
Good comment above. For a professional shop I'd for sure recommend a NEMA 4 enclosure, nothing else. I'm a hobby type maker and a $110 Chinese NEMA 1 open VFD has served me nicely for 4 yrs or so. I do have filters over the air inlets to prevent steel dust from entering the VFD.
Stacy E. Apelt - Bladesmith said:
They take the wattage and then multiply it by the percentage of speed over 1750. A 5000 RPM motor that creates 745 watts of power suddenly becomes a 2.85 HP "rated" motor on the box description.
Click to expand...
Thanks for that input Stacy - I'd always wondered how they came up with those over rated HP numbers. The ONLY way to tell true hp is look at the wattage. Due to the inefficiency of motors it's going to take almost 1,000 watts to get 1 hp. 745 watts is in a perfect world.

Ken H>
 
Kevin McGovern said:
If you are on the home built belt Grinder group on fb, you will see my repeated attempts at reasoning with treadmill motor enthusiasts in regards to time spent setting them up vs. short lifespan. You'll also see I am repeatedly told that it's not an issue. Get a proper sealed motor so you can stop screwing around with the motor, and get to making knives.
Click to expand...


YES

Leave the treadmill motors in the treadmills.

I once saw a treadmill that cost $5,000 ish new get gutted for a motor.

SELL it.

Buy a proper industrial motor and controller.
The motor mounts and wheel mounting will be universal fit and replaceable.
 
Stacy E. Apelt - Bladesmith said:
The rating on treadmill and other high RPM motors like routers and vacuums is a calculation that someone came up with that is false. They take thewattage and then multiply it by the percentage of speed over 1750. A 5000 RPM motor that creates 745 watts of power suddenly becomes a 2.85 HP "rated" motor on the box description. This might sell the items, but doesn't change the reality that they are only 1 HP.
Click to expand...

It's similar to how some Professional Audio companies market their speakers and amplifiers. They like to put PEAK wattage on the labels, when in reality you'd be lucky to run it at just over half of that, and in many cases, you probably won't even get THAT rating out of it.

"but higher numbers are better!" :rolleyes:
 
12345678910 said:
YES

Leave the treadmill motors in the treadmills.

I once saw a treadmill that cost $5,000 ish new get gutted for a motor.

SELL it.

Buy a proper industrial motor and controller.
The motor mounts and wheel mounting will be universal fit and replaceable.
Click to expand...
Agreed. There are plenty of people in the market for a new clothes rack... :D
 
You must log in or register to reply here.
Back
Top