Air Compressor Conversion

[orezok]

The electric motor on my 35 year old Speedair is gone. The pump and everything else is in good shape. I have a brand new 6.5 HP gas engine that I could mount. I know that I will need some kind of unloader to release pressure as the gas engine runs constantly. Does anyone have a suggestion?

 

[TemporaryKubotaOwnerMark]

How big was the electric motor? If it was a 5 hp electric, that 6.5 gasser is probably not going to get the job done.

gas hp to electric hp conversion chart at DuckDuckGo

 

[orezok]

How big was the electric motor? If it was a 5 hp electric, that 6.5 gasser is probably not going to get the job done.

gas hp to electric hp conversion chart at DuckDuckGo

It's a 2 HP.

 

[3930dave]

Can't say I know that setup in detail.

I'd probably try and find a shop that has a fleet of road-service trucks. If they don't have some scrap units around to pull parts from, they may be able to tell you of a good source. Just my guess, for a place to start.

Rgds, D

 

[TemporaryKubotaOwnerMark]

Why make it complicated? A 2 horse electric motor is not expensive.

 

[RickB]

Why make it complicated? A 2 horse electric motor is not expensive.

It's the TBN way.

 

[Deere Dude]

I have a compressor and tank with gas motor and uses a pressure relief valve that just dumps air to the atmosphere.

 

[roadhunter]

It's the TBN way.

So true. But hey its' entertaining.

To the OP. Simply go buy a new electric motor would be my suggestion. I'm sure it can be done for under $150 at HF with a coupon.
2 HP Compressor Duty Motor

Seems like it will be complicated to make the gas motor work without adding $150 in parts.

 

[orezok]

So true. But hey its' entertaining.

To the OP. Simply go buy a new electric motor would be my suggestion. I'm sure it can be done for under $150 at HF with a coupon.
2 HP Compressor Duty Motor

Seems like it will be complicated to make the gas motor work without adding $150 in parts.

All true, but this is not my shop compressor. It's primary use is when I need air somewhere on my 26 acres. and I haven't found an extension cord long enough :laughing:. I think running it on my generator is what took out the motor. Hauling both a compressor and a 9000 watt generator is problematic.

I have a virtually new gas motor setting in the shop waiting for a job to do.

I only use the compressor a couple of time a year so I'm looking for a simple solution.

 

[TemporaryKubotaOwnerMark]

How about searching around for a diagram of a commercial gas powered compressor, and seeing what they use? You might be able to grab some part numbers and cobble up your own system.

That approach should meet the TBN complexity requirements, too!

 

[Deere Dude]

https://d2pbmlo3fglvvr.cloudfront.net/product/full/Z2yyo_fo5oy.JPG

$ 5-10

Can buy them preset at a number of pressures. Just tee it in on the pressure line going to the tnk from the compressor..

 

[drizler]

Electric motors are cheap. The secret is where you get it and not get scalped. Try looking for a local mom n pop electric motor shop. Not the guys who rebuild your car alternators and starters but rather the ac type. They may be able to rebuild yours. If not they will definitely be able to score you one for a good price. You can often get a Dayton for less than you pay for "one of those" at HF.
I had a rental mobile home furnace's blower motor go a while back. Replacement was around $200 just for the motor . A couple other places could get one for around $180. I ended up at the local AC motor repair shop to see if they could fix it. No dice but I walked out with a Dayton for around $100. If you can fix it for that much you are far better than shopping for a new compressor.

 

[kc5dlo]

Sounds like a gas conversion is what you need. Electric motors may be cheap, but an engine you already own is cheaper. Add to that no electric service where you use it, no brainer.

The compressor on my neighbors service van will idle down when the tank is pressured up fully. If you are needing just occasional use, I would think an unloader valve would be all you would have to add.

 

[CADplans]

Compared to any other use of electricity, an electric motor is the most efficient use.
For the cost of running a 100 watt incandescent light bulb, I run a 48" fan in my shop.
The whole shop stays comfortable on a hot day.
When it is humid, I can pump almost 3 gallons of water a day out of the air with my basement dehumidifier, for $0.75 a day
The cost of compressing air with a gasoline engine will be high.
I use my stationary electric compressor,,, and have a 100 foot hose to make the air "portable",

Further portability is the only reason to use an engine.

 

[Soundguy]

All true, but this is not my shop compressor. It's primary use is when I need air somewhere on my 26 acres. and I haven't found an extension cord long enough :laughing:. I think running it on my generator is what took out the motor. Hauling both a compressor and a 9000 watt generator is problematic.

I have a virtually new gas motor setting in the shop waiting for a job to do.

I only use the compressor a couple of time a year so I'm looking for a simple solution.

why do you think the genny took out the motor?

 

[orezok]

why do you think the genny took out the motor?

I originally had a 3500 watt generator and tried to run the compressor. After about a minute it started to release the factory smoke. I stopped it and inspected the motor. One of the points on the centrifugal switch was completely melted off. I McGivered it as the motor is 35 years old and I couldn't find a replacement part. I dug through my junk box and found an old set of automotive points that had a large contact. Silver soldered it to a piece of brass shim material and then silver soldered that to the metal spring that contacted the centrifugal mechanism. The nylon "rubbing block" was also gone so I found a small piece ofnylon and epoxy'd it to the spring.

This has worked for about a year when I could access shop power. I got a new 9000 watt running 10000+ starting generator and thought it would do the trick for remote operation. I hooked it up and tried it again, closely watching the motor. After about 10 seconds,the factory smoke started to reappear. I quickly killed it. No noticeable damage this time. Tried it again on shop power and it runs OK.

The only thing I can think of on the generator power is that for some reason the motor is not geting up to full speed and the centrifical switch is not disengaging allowing the start capacitor to remain in circuit. This will cook the windings in short order.

The 9000 has more than 3 times the power needed to run this motor which has a RLA of 12 amps.

Since I just use this compressor a couple of times a year for small projects, I think I will just install a 120PSI blow off and let it run. This motor doesn't have a governor so there is no practical way to make it idle down. I'll just manually adjust the speed to keep the pressure close to blow off pressure.

 

[Mendonsy]

One thing that hasn't been mentioned yet .... the electric motor probably runs at about 1760 rpm but the gas engine will want to run faster than that. You may have to change the drive ratio between the motor and the compressor.

 

[SPYDERLK]

I originally had a 3500 watt generator and tried to run the compressor. After about a minute it started to release the factory smoke. I stopped it and inspected the motor. One of the points on the centrifugal switch was completely melted off. I McGivered it as the motor is 35 years old and I couldn't find a replacement part. I dug through my junk box and found an old set of automotive points that had a large contact. Silver soldered it to a piece of brass shim material and then silver soldered that to the metal spring that contacted the centrifugal mechanism. The nylon "rubbing block" was also gone so I found a small piece ofnylon and epoxy'd it to the spring.

This has worked for about a year when I could access shop power. I got a new 9000 watt running 10000+ starting generator and thought it would do the trick for remote operation. I hooked it up and tried it again, closely watching the motor. After about 10 seconds,the factory smoke started to reappear. I quickly killed it. No noticeable damage this time. Tried it again on shop power and it runs OK.

The only thing I can think of on the generator power is that for some reason the motor is not geting up to full speed and the centrifical switch is not disengaging allowing the start capacitor to remain in circuit. This will cook the windings in short order.

The 9000 has more than 3 times the power needed to run this motor which has a RLA of 12 amps.

Since I just use this compressor a couple of times a year for small projects, I think I will just install a 120PSI blow off and let it run. This motor doesn't have a governor so there is no practical way to make it idle down. I'll just manually adjust the speed to keep the pressure close to blow off pressure.

Sounds like a genny speed problem. Low frequency will cause slow running and will heat a motor up. Compounding that with a sticky start winding switch and youve got a smouldering fuze.

 

[Soundguy]

I originally had a 3500 watt generator and tried to run the compressor. After about a minute it started to release the factory smoke. I stopped it and inspected the motor. One of the points on the centrifugal switch was completely melted off. I McGivered it as the motor is 35 years old and I couldn't find a replacement part. I dug through my junk box and found an old set of automotive points that had a large contact. Silver soldered it to a piece of brass shim material and then silver soldered that to the metal spring that contacted the centrifugal mechanism. The nylon "rubbing block" was also gone so I found a small piece ofnylon and epoxy'd it to the spring.

This has worked for about a year when I could access shop power. I got a new 9000 watt running 10000+ starting generator and thought it would do the trick for remote operation. I hooked it up and tried it again, closely watching the motor. After about 10 seconds,the factory smoke started to reappear. I quickly killed it. No noticeable damage this time. Tried it again on shop power and it runs OK.

The only thing I can think of on the generator power is that for some reason the motor is not geting up to full speed and the centrifical switch is not disengaging allowing the start capacitor to remain in circuit. This will cook the windings in short order.

The 9000 has more than 3 times the power needed to run this motor which has a RLA of 12 amps.

Since I just use this compressor a couple of times a year for small projects, I think I will just install a 120PSI blow off and let it run. This motor doesn't have a governor so there is no practical way to make it idle down. I'll just manually adjust the speed to keep the pressure close to blow off pressure.

9kw genny should have no problem starting and running that motor...

 

[orezok]

One thing that hasn't been mentioned yet .... the electric motor probably runs at about 1760 rpm but the gas engine will want to run faster than that. You may have to change the drive ratio between the motor and the compressor.

It's a typical 3450 230v motor. Very compatible with gas.