drive wheel size

J

jonnydot

Joined
Nov 18, 2022
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Hi all What size motor drive wheel would you suggest please? My motor is a 3phase at 50htz 2,2kw 2880 rpm or at 60htz 2.55kw 3456 rpm (run via a VFD input power is 240v 50 htz (Australia)) I have a 121mm ,m20 bore tracking wheel (eBay special) and 47mm m12 bore platen wheels from TR maker using Brian Housewert plans. Usage is for general hogging will not at this stage be making knives ....Link to the motor specs https://cononmotor.com.au/product/2-2kw-3hp-2800rpm-shaft-24mm-electric-motor-three-phase-gl-415v-2/
 
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It depends on your preferred hogging speed. with your 2880rpm motor, the VFD can deliver 5760rpm at the 2X setting.
Most folks max their belt speeds between 5000 and 6000fpm (roughly 1500-1800meters per minute). Some folks run them at 7000fpm/2150mpm, which is really fast!
shooting for the 1500-1800mpm range, you would use a 4"/100mm drive wheel and set the VFD for 2X max speed.
If you wanted to use a larger wheel like a 6"/150mm, you could run the grinder at a lower motor speed and still get the desired belt speed.
7"/175mm would almost double the belt speed, and you would only need to run the VFD at the 1X setting.
The differences are really insignificant with a VFD.

So, 100mm minimum, and 175mm maximum. For a hogging grinder, I would go with a 150mm drive wheel.
 
Look at the tech specs on the good belts.

the ceramic blaze belts recommend 5,000- 6,000 sfpm

The sfpm of your grinder will be rpm x (pi x wheel diameter in units of feet not inches )

a six inch wheel
3400 rpm x (3.14 x ( 0.5))
= 3400 x 1.5 ish

5,100 sfpm





My wilton square wheel clone came with 3400 rpm motor and 6 inch wheel.
 
His motor only runs at 2880rpom. ( Australia 50Hz)

Otherwise, your calculations are correct. Use a 6" wheel - which is a 150mm wheel.
 
Stacy E. Apelt - Bladesmith said:
His motor only runs at 2880rpom. ( Australia 50Hz)
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If he's using a Chinese VFD he can set the speed to 3500, or even 4,000 RPM if desired. While the 27D VFD only has a 2X setting (my understanding) the Chinese VFDs normally allow choosing the RPM desired by setting the max freq used.

That brings up a question, since the output freq of the VFD is what determines the motor RPM, does it matter if the input to VFD is only 50 hz?
 
Ken H> said:
That brings up a question, since the output freq of the VFD is what determines the motor RPM, does it matter if the input to VFD is only 50 hz?
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No. Input is irrelevant. VFD alternates frequency per setting. Input is transformed to DC before alternation.
 
Ken H> said:
If he's using a Chinese VFD he can set the speed to ...4,000 RPM if desired.
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Yes, but at some point there is a limit on bearing speed.

4000 rpm, 6" drive and 2" platen wheel is

4000 x 6/2 = 12,000 rpm on those platen wheel bearings.
 
JoeBusic said:
No. Input is irrelevant. VFD alternates frequency per setting. Input is transformed to DC before alternation.
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That's what I was thinking. As a result the 50/60 hz motor that turns 2850 rpm on 50 hz, is actually going to be the same as a 60 hz motor when using a VFD. Even with the the 27D with the max speed trimpot (0.7-1.1x) the 100% would give a 2 pole motor the normal 3600 rpm rather than the 2850 rpm of a 50 hz motor - is that correct?

12345678910 said:
Yes, but at some point there is a limit on bearing speed.
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Yep, that's why I use a 3" platen wheel. I run my 5" drive wheel around 3825 rpm for a 5,000 SFPM belt speed.
 
Ken H> said:
That's what I was thinking. As a result the 50/60 hz motor that turns 2850 rpm on 50 hz, is actually going to be the same as a 60 hz motor when using a VFD. Even with the the 27D with the max speed trimpot (0.7-1.1x) the 100% would give a 2 pole motor the normal 3600 rpm rather than the 2850 rpm of a 50 hz motor - is that correct?
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Yep. All 3 phasers have the same efficiency at 50 and 60Hz. Intentionally, so no worries where the motor came from. Only to consider are the bearing if one wants to go high speed, like closer to 15000sfm (75ish m/s). Bearing deteriorate fast with overspeed. It's way better to put a bigger drive wheel.
 
12345678910 said:
Yes, but at some point there is a limit on bearing speed.

4000 rpm, 6" drive and 2" platen wheel is

4000 x 6/2 = 12,000 rpm on those platen wheel bearings.
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Yep. Bearing destroyer. Mine went bust in a week. Changed them with high quality german ones and it's almost 2 years and still running fine.
 
JoeBusic said:
Yep. All 3 phasers have the same efficiency at 50 and 60Hz. Intentionally, so no worries where the motor came from. Only to consider are the bearing if one wants to go high speed, like closer to 15000sfm (75ish m/s). Bearing deteriorate fast with overspeed. It's way better to put a bigger drive wheel.
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I run one of my grinders on 50 m/s .Only reason I don t try faster is belt .I can t find data which is max. speed on belts .Do you think that 75 m/s is safe ? I would start making another grinder tomorrow if belts can handle 75 m/s :)
 
Natlek said:
I run one of my grinders on 50 m/s .Only reason I don t try faster is belt .I can t find data which is max. speed on belts .Do you think that 75 m/s is safe ? I would start making another grinder tomorrow if belts can handle 75 m/s :)
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Forged in fire had the machines set for max 75m/s. Only a few belts broke and was attributed to too high pressure. I think the biggest issue is the platen. Avoid the joint to smack the edge of the platen and all should be OK. Speed is just a different approach to grinding. Even AlO belts can grind carbide monsters. :)
My max is 60m/s and never broke a belt except for the one where the platen edge ripped it. On the wheel it's a blast how things go.
 
JoeBusic said:
Forged in fire had the machines set for max 75m/s.
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I've been looking at that number for a couple of days and it just seems FAST!!! 75 meters is (3,3 X 75) = 247.5 ft/sec? That would be (247.5 X 60) = 14,850 ft/min (SFPM). From looking at the grinders used the drive wheels are perhaps <7" diameter?

Even with the motor turning 5,000 rpm which I understand is about the max a motor will turn, that would require <11" diameter drive wheel.

Please correct if I missed something in my math.
 
Ken H> said:
I've been looking at that number for a couple of days and it just seems FAST!!! 75 meters is (3,3 X 75) = 247.5 ft/sec? That would be (247.5 X 60) = 14,850 ft/min (SFPM). From looking at the grinders used the drive wheels are perhaps <7" diameter?

Even with the motor turning 5,000 rpm which I understand is about the max a motor will turn, that would require <11" diameter drive wheel.

Please correct if I missed something in my math.
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In one episode they said the max speed is 7k rpm. That's 200% on the VFD of a 3456rpm motor. They use 8" wheel.
 
JoeBusic said:
In one episode they said the max speed is 7k rpm. That's 200% on the VFD of a 3456rpm motor. They use 8" wheel.
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WOW - that's humming. At 7k rpm is almost 13k SFPM belt speed. I think that would scare me! Can you imagine a 36 grit belt breaking at that speed while grinding? In the blink of an eye you could get some serious skin rash..... right to the bone!
 
They mentioned it's 15k sfm. Shielding upper wheel on a platen is enough for protection. When the belt brakes, it has due to low mass low momentum and drops immediately. It has to break between the tracking and upper platen wheel at high speed to have usable momentum to flip into the head real close. If it breaks anywhere else, it's harmless. So, a simple shield on the upper wheel will do. Adding a large piece of tape on the connection can be very helpful, just in case. :)
 
Ken H> said:
WOW - that's humming. At 7k rpm is almost 13k SFPM belt speed. I think that would scare me! Can you imagine a 36 grit belt breaking at that speed while grinding? In the blink of an eye you could get some serious skin rash..... right to the bone!
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Not dangerous at all if belt break on high speed . I know that first hand :) JoeBusic explain that well .....
 
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