FIAC AB5/10 compressor pump.

[p0689109]

I have one of these pumps that I picked up at auction. The motor was burnt out so I have been trying to work out what size motor is required to power the pump. it has twin pistons of 59mm bore by 60mm stroke. The flywheel(pulley) fitted has a diameter of 350mm. I contacted the uk importers of these pumps to find out the optimum speed of them and he said that with a 3hp motor it would be 1000rpm, 3.5hp would be 1250 rpm and a 4hp motor would be 1400 rpm. Now I always thought that the optimum speed would be a set rpm and then by selecting a motor with a given speed, set by the number of poles it has, and fitting a pulley wheel of the correct diameter to turn the pump to obtain that speed. But from what he said the pump can be run at any speed up to 1450rpm. Of course you can run a pump slower than its max but you are not getting the max output of the pump which is a bit self defeating! Does this sound right to you or am I reading this wrong?
Regards, Michael T

 

[tigler]

From that information it appears the pump is designed to operate over a wide speed range to provide different air volume depending on the motor.
The same pump is used on a number of compressors in the Fiac range.

 

[marc76]

It looks to me a low rpm is beneficial. Assume those cylinder heads have poor valves in terms of area vs. swept volume which means not a lot of air will flow there, or heat will build up otherwise.