Compressor conversion question

[rcontrera]

That compressor is a Coltri Sub MCH6 that American Briston adapts to their own use and needs at least a 4 HP electric motor. The rated operating speed is 2400 to 2800 RPM.

 

[pescador775]

The American Bristol compressor was based on a block made by Bristol in England. It was not the Coltri Sub. I doubt that the small "fresh air" is still available in the US. Parts for it may be hard to find. As I said in previous posts, the owner of American Bristol retired and the company went in another direction.

 

[dogfix]

Here is some additional information on my compressor. It was made in 1979. American Bristol is now owned by Scott Health & Safety, out of Monroe, North Carolina. I have talked with Scott H&S and they assure me that parts are still available, at least for a while.

I don't know what "an unloader" is, at least by that name.

I received no manual or documentation with the compressor. Scott H&S no longer has any documentation for that old of a product.

When I originally got the compressor I took it to Breathing Air Systems in Reynoldsburg, OH. They gave it the twice over, and pronounced it to be in sound working order.

 

[pescador775]

Believe it or not, here is a Bristol, electric for sale:
http://cgi.ebay.com/Fresh-air-scuba...QQihZ019QQcategoryZ106436QQrdZ1QQcmdZViewItem

It was the smallest model offered at that time.

 

[twosheets]

Have boat, need anchor! Will pick up for F R E E!

(just had to say this, I am sure you will find someone knowleable but if you don't...)

 

[dogfix]

What is the process for calculating pulley ratios if I need to make an adjust to the speed?

 

[rjack321]

Do you really want to change the speed and know why? Some compressors won't get enough lubrication if you slow them down and speeding them up past design speed is a bad idea too.

Regardless its a simple ratio, diameter drive pulley to diameter compressor pulley. Like 3":12"

If you made that 6":12" - the compressor would turn 1/2 as fast.

 

[dogfix]

The reason I was asking about pulley ratios is: I'm assuming which ever motor I get will run at a different RPM than the gas engine. So I would need to adjust the pulleys.

Is there a control that I could put on the motor to adjust the speed?

How can I measure the speed the compressor is running at?

 

[rjack321]

RPM motor / RPM compressor = diameter motor pulley / diameter compressor pulley

You need to know any 3 of those 4 numbers, calculate the 4th by cross-multiplication.

You have the RPM of the compressor (~2500) and can measure the compressor pulley's diameter. The plate on the electric motor gives you its RPM. So the remaining value is the motor pulley diameter.

Or if you want to reuse the motor pulley calculate the other way and figure out what RPM motor to buy.

 

[pescador775]

If you install a 3450 rpm electric motor you can use the same size pulley wheel. The faster the motor spins, the faster the motor cooling fan turns. Stop worrying about non existent problems like speed controllers and ratios.