Instructables

How to convert a gas powered air compressor to electric?


I have an old gasoline engine powered, belt driven air compressor on which the the engine no longer works. Does anyone know of a way to convert it to an electric compressor I can use in my shop? I'm guessing I could remove the engine and use an electric motor, but am not sure how to make the motor shut off when the tank reaches pressure, how many rpms the motor needs to do, or even what kind of motor I need to look for. Thanks for any help you can give me!

chip1232 years ago
The way I interpret this there are several problems to be addressed: identifying a replacement motor; attaching the motor to the compressor; powering the motor; and the shut off when the tank reaches the desired pressure.

Identifying a replacement motor
You need to find out the rpm of the existing engine. If you know what engine it is, it is usually easy enough. Just type in the make/ model of motor into Google and look for a spec sheet. Then take this figure, and find an electric motor which has the same rpm. If you can find one, then great. Remove the old engine, put in the new motor, job done. If you can’t, then you will need to identify the rpm required by the compressor pump. Then find the rpm of the desired replacement motor. Then rig up a pulley system which gives the desired rpm at the pump. i.e., if the pump wants 1000rpm and the motor gives 2000 rpm, then put a small pulley on the motor side, and a one that is 2 times the size on the pump size. Then for every 1 revolution of the motor, there will be 1/2 a revolution at the pump. The rpm isn’t the only thing to worry about though; the torque also needs to be considered. If your new motor produces very little torque then you will need a very large pulley ratio which will drastically reduce the rpm. If the new motor produces very high torques then only worry about matching the rpm.

Attaching the motor
If the shafts on the new and old motors are the same size and type, then simply remove the old one, put the new one in, and job done. If not, then the best bet is probably to find a new pulley which will accept the new shaft. As for mounting the motor to the tank, attach by whatever means suits you. If this means cardboard and duct tape then so be it, but probably better to go for a steel mounting bracket which will bolt on to where the old motor was previously attached.

Powering the motor
I’m not even going to go there. I don’t know enough about electronics to begin to describe how to do this. Best to get someone who knows what they're doing.

Shutting off the motor when at desired pressure
Did the old engine used to stop and start automatically? If it did then there’s already a pressure sensor and it will be a matter of connecting this to the powering circuit. As I said before, I don’t know enough about electrics to describe how to do this. If it didn't, then why should the new one? There will be a pressure release, or a valve of some kind that will open so air is no longer pumped into the tank when the desired pressure is reached; so the motor can just be running constantly.

How do I know this?
I was going to do something similar. In the end I decided not to, due to how many variables were involved. If you make it work, please let me know- I’d like to hear how it turns out.

One last thought:
Does it have to be electric? If not then why don't you just get a direct replacement engine that's exactly the same as what you had before? May work out cheaper, and it would certainly be a lot less work.