# converting 3 phase motor to 6.5HP gasoline



## briankmizell (Aug 22, 2012)

*convert 3 phase elec air compressor to 6.5HP gasoline*

I got an old air compressor that had a 3 phase 5 HP engine on it, I believe its a 60 gallon tank. I am going to put a 6.5hp honda engine on it.

I am new to this so I need some info about plumbing sizes, idle control etc etc.


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## KRE (Nov 29, 2011)

You need to match compressor speed, easy to do with pulley size on engine. The old un-loader system may have to be changed. You will have to add an air throttle, or electric actuator to the Honda to idle the engine when the pressure in the tank meets required max pressure. The swap out is *Not* a plug an play.


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## briankmizell (Aug 22, 2012)

I knew it wouldn't be plug-n-play, (to bad it isnt that easy...lol).

Using this calculator Pulley Belt RPM and Speed Calculator, the original electric motor rpm was 1750 and the pump pulley would rotate at 464.8 rpm.

The engine pulley is 4.25" O.D. and the pump pulley is 16" O.D.

The honda engine turns 3600 rpm MAX, this will set the pump pulley's new speed at 956.3 rpm.

I have read that you want to keep the pump rpm's below 1000 rpm. Would there be a problem running it that fast?


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## KRE (Nov 29, 2011)

Most pump mfgs recommend a middle of the road spec, for life vs SCFM delivery. I'd pulley to factory specs +/- 10% easy to do as pulleys can be had cheap. Be sure to match the belt size(with) or it will eat belts. Unload-er system will be your main issue, with the engine speed device second. Resip engine unload-er's are totally different than electric motor, unload-er's. By the time your done you will be at or above the cost of just installing a single phase motor an starter. Neither are pricey if you shop around. The skill set learned in the swap out might be worth the effort, depending.


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