belt grinder build

A

achillesgr

Joined
Apr 29, 2012
Messages
9
hi ,
i am mew to this forum and i need your help to build a belt grinder for 72" belts.
i need to know what is the optimum speed of a belt so i can choose a motor.
the motors i heve seen are 1phase 1400 or 2800 rpms.
can someone pleae suggest a speed or optimum rpms?
thanks
 
Which grinder type do you plan to build ?


In my opinion,it won't' really matter much between those motor speeds, because you can change it with pulley and wheel sizes..




Make sure the motor is enclosed

a 5/8" shaft will give you the greatest flexibility on buying wheels


If possible buy a VFD and 3 phase motor for variable speed.
 
The motor I am planning to use is 1400 rpms and with a 4” drive wheel I will get about 2880sfpm.
Also I am thinking to use 2hp motor so not to have drop in rpms .(the problem is that the motor have 1" shaft)
i will try to avoid the 3 step puuley setup for simplicity reasons.
I did not use that kind of equipment before and do not know if that sfpm range is enouth. Do you think it is ok?

can i use any 3phase motor with vfd or do i need special motor?
i have seen some vfds on ebay but i do not know much about motors.
thanks!!
 
No expert here but have built my own NWG grinder. The slower the better in my opinion I have 1400rpms on my 2hp and it runs just fine, I also have a four step pulley system to vary the speed which in my opinion is important, but can be achieved with a VFD. As far as I know it doesn't have to be a special VFD just check the shaft suits the rest of your system.
 
hi,
in witch gear you have the step pulley setted most often?
do you have experience with those vfds? id do not knowhow good it is for the motor..
there are some vfds about 100$ on ebay and two step pulleys are about 50$ , no big deal. but is this usefull?
do i need 3phase motor to run with vfd?
can i use any 3 phase or there are special type mootors?
thanks
 
Most 3-phase motors will run fine on a VFD. Very old ones seem to have brittle varnish on the windings which can break down as a result of the fast switching from a VFD. I've used motors from the mid-1960s without a problem but I wasn't overly keen. I've no qualms about motors from perhaps 1980 and onwards.

Mostly, people think in terms of slowing motors down, but a VFD can also speed them up.

Usually, the best usable speed range is to be had from a 4-pole motor (rated for a bit under 1800 RPM on 60 HZ mains, 1500 RPM on 50 HZ), run between 10 Hz and 100 Hz to give a 300-3000 RPM range. A Sensorless Vector VFD can usually extend the slow range a bit, and you might find you can get a bit more at the high end once you have it all put together and start playing.

Below about 25Hz on a TEFC motor, you usually need to derate, as the cooling air is moved by the fan on the motor itself. Slowing the fan reduces airflow which reduces cooling. In reality, it's not a problem for anyone with any mechanical sympathy at all (they'll just ease up or let it rest) but is something to be aware of.
 
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