Help with Speed of Belt Grinder Belt

B

Bushman150

Joined
Sep 13, 2018
Messages
6
New to forum..Hope I have this in the right place..I am in the process of building a homemade belt grinder and was wondering how to calculate the speed of belt. It is not complete, but did a test run on what you see in picture and it runs out real well so far. seems a little slow

The belt is 72" long X 2"
The motor is 2 HP 1745 RPMS
The drive pulley on motor is 4-3/4"
The idler pulley 2-3/4"
The other two pulleys are 2" diameter

Any help would be greatly appreciated
 
(Motor rpm x drive wheel diameter x pi) divided by 12

1745rpm x 4.75 x 3.14 = 26,026.675 inches per minute

divide by 12 for feet per minute

= 2,168.89 surface feet per minute
 
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Bushman150 said:
New to forum..Hope I have this in the right place..I am in the process of building a homemade belt grinder and was wondering how to calculate the speed of belt. It is not complete, but did a test run on what you see in picture and it runs out real well so far. seems a little slow

The belt is 72" long X 2"
The motor is 2 HP 1745 RPMS
The drive pulley on motor is 4-3/4"
The idler pulley 2-3/4"
The other two pulleys are 2" diameter

Any help would be greatly appreciated
Click to expand...

To slow..........you have only 10m/s belt speed or 2150 SFPM....
Just enter your data ................

https://www.blocklayer.com/pulley-belt.aspx
 
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OK guys, lets not derail the OPs question.

As Matthew explained, all you need is the motor speed and the drive wheel size times pi and divided by 12 ( to convert to feet).

2170 SFPM isn't screaming fast, but is a usable speed for a grinder. It is slow enough to work hardened steel and wood, and fast enough to remove stock at a reasonable rate.

To increase the speed you have to use a larger drive wheel, or use a 2/3/4 set of pulleys. A pair of those would give you 1000/2100/4200 SFPM speeeds.
 
Matthew Gregory said:
(Motor rpm x drive wheel diameter x pi) divided by 12

1745rpm x 4.75 x 3.14 = 26,026.675 inches per minute

divide by 12 for feet per minute

= 2,168.89 surface feet per minute
Click to expand...

Appreciate the fast response..Thanks a lot...New to the site. Looks like it has a lot of helpful folks
 
Stacy E. Apelt - Bladesmith said:
OK guys, lets not derail the OPs question.

As Matthew explained, all you need is the motor speed and the drive wheel size times pi and divided by 12 ( to convert to feet).

2170 SFPM isn't screaming fast, but is a usable speed for a grinder. It is slow enough to work hardened steel and wood, and fast enough to remove stock at a reasonable rate.

To increase the speed you have to use a larger drive wheel, or use a 2/3/4 set of pulleys. A pair of those would give you 1000/2100/4200 SFPM speeeds.
Click to expand...

Thanks for the update..Appreciate it
 
There is a trade off between torque and speed. So while some may say it is a bit slow, i would say it is a torque build (hard to bog down). Also, if you do post HT grinding like i do a lot, it will help reduce heat. My current grinder is 3000sfpm (odd pulley sizes) and it removes material fine for me, but it has a weak motor and i bog it down sometimes.
 
Torque is a very over-rated issue with knife grinders. We don't need torque, we are using a moving surface. The factors that control a knife grinder are power (HP) and speed (SFPM). Generally speaking, on a basic grinder set-up, any motor over 1.5Hp is sufficient and any speed in the 2000-3000SFPM will work.

With a 2HP motor, Bushman won't have power issues. The speed of his grinder can be left as is, and in the future he can either switch to a 2/3/4 system of pulleys or go VS with a 3Ph motor and VFD. I always recommend going to 240 VCA power and using a 3Ph/VFD package as the simplest upgrade. DC and a speed control is also a good option.
 
Though I agree that most people will be fine with a 1.5-2hp grinder I think it’s kinda the starting point. I really lean into my grinder and it’s a 2hp. And I want more power. Where I find issues is when I over drive the motor to faster RPM then rated speed. I really like the 6k range for hogging and even used belts can rip steel off at these higher speeds. Next belt grinder I’m building will be at least 5hp. Not becaus I think more is better but I just don’t want to notice any slowing or loss of power at higher speeds.
 
Hey JT, i have often wondered if there is a belt speed where you remove metal so fast that the blade starts heating up less. Is there?
 
metal removal by abrasion creates heat … the more you remove the more heat created.
 
you want to remove metal quick, you use saw or 90* grinder. 2x72 is best used for fine grinding and setting bevel
 
scott.livesey said:
you want to remove metal quick, you use saw or 90* grinder. 2x72 is best used for fine grinding and setting bevel
Click to expand...

I beg a differ. An angle grinder for the most part won’t hold a candle to the amount of steel s 2x72 will remove with a fresh belt. Also bandsaws are used do you can profile a blade out of sheet or wide bar. Depending on the saw of corse speed varys. Still a belt grinder is faster. Only a thing I have found that can remove steel faster the a belt grinder is a plasma cutter.
 
I'm with JT here. A 36 grit ceramic belt and a good 2X72 will eat metal FAST. I can set the basic bevel in one or two passes.

As to heat build up - I regularly turn steel red while hogging it hard.
 
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