Saylor Beall 705-5 Pump RPMs

[jdclarey]

Just picked up an 80g Compressor that has a SB 705-5 pump (Pump is 11 years old). However, the man who sold it to me was using a Marathon 5hp Cont Duty 1800 RPM motor.

Pulley of motor is about 7.5" OD. Is this motor appropriate for this pump?

AXD 184TBFR7070AP L

 

[jdclarey]

Just did the math and works out right around 850rpms.

 

[Ing3018]

That's about right. I have measured the actual speed on mine before and it was right around that same figure as you calculated.

 

[purplezr2]

845 is listed by Saylor Beall.

Could have had a 1740 rpm, or 1725 rpm motor originally.

 

[Ing3018]

I found a note I made when getting Saylor Beall 705 set up after I rebuilt the pump.
Unloaded motor speed, no belts: 1799 rpm, 10.5 amps
Unloaded pump, 0 psi: motor 1780 rpm pump 822 rpm, 12.5 amps
120 psi, 21amps 808 RPM
170 psi, 23 amps
Has a Baldor motor 1725 RPM motor.

 

[Firebrick43]

845 is listed by Saylor Beall.

Could have had a 1740 rpm, or 1725 rpm motor originally.

All one and the same.

A 4 pole induction motor has a theoretical speed of 1800 rpm at 60 hrs and 1500 rpm at 50 htz.

However there is some slip depending on the load. Some manufacture state rpm at no load, some at rated hp, and some at rated torque.

 

[On-Wheel]

You guys motivated me.Swaped 6.75 to 7.75 !
1740 should be close to 800 now.
The pulley was torched off its motor so I used my shop press to disassemble .
Was an outside unit so it was on there.Made my hydraulic press bleed.lol
The smaller one came off easy.

 

[redmondjp]

All one and the same.

A 4 pole induction motor has a theoretical speed of 1800 rpm at 60 hrs and 1500 rpm at 50 htz.

However there is some slip depending on the load. Some manufacture state rpm at no load, some at rated hp, and some at rated torque.

For a synchronous motor, you are correct. However, you will never see the synchronous speed of 1800rpm on a 4-pole induction motor - the rotor MUST turn slightly slower than this, in order to cut through the rotating field in the stator (known as "slip") which generates current flow in the rotor, which then creates the magnetic field. So that's why you will see something less, like 1725 or 1740rpm, or 3450rpm for a 2-pole induction motor.

 

[Firebrick43]

For a synchronous motor, you are correct. However, you will never see the synchronous speed of 1800rpm on a 4-pole induction motor - the rotor MUST turn slightly slower than this, in order to cut through the rotating field in the stator (known as "slip") which generates current flow in the rotor, which then creates the magnetic field. So that's why you will see something less, like 1725 or 1740rpm, or 3450rpm for a 2-pole induction motor.

Did you read what I wrote? I never said synchronous, I said induction and in the second paragraph talked about slip.

 

[On-Wheel]

I need to switch out my mag start to a soft start.The motor now takes off like on a drag strip.Burning rubber I tell yah!