Compressor pump speed/motor sizing

[Cuthy246]

Looking for some advice for a compressor I have recently acquired. Bought a Chinook K30 compressor head from a guy local to me for the massive sum of £20 (robbery I know but it's all he wanted). Specs state 5.5kw motor at 1150rpm pump speed giving 31cfm and 160psi. I am distinctly lacking in a 3ph supply so was thinking of getting a 1ph 3hp 3000rpm motor with a large reduction to give about 7-800rpm pump speed. Would this work? Obviously not going to get full output but it's waaay more than I need. Would love to use this but if it's not going to be feasible will probably have to sell it on.

 

[dan treg]

a single phase compressor running a 3 hp 2.2kw motor may produce with correctly sized pump say 15cfm . so effectively you would need to gear the pump down to almost half speed else you will overload motor especially on start up torque and when motor kicks back in. also not sure how efficient pump will be running half speed almost need to consult supplier and ask question

 

[Cuthy246]

Might just give it a go to see what happens. Thinking 3000rpm motor with 6" pulley turning the ~23" flywheel gives a ratio of nearly 1:4 and rpm at pump just over 700. Would love to build a nice compressor around this as it looks like it would last donkeys

 

[brightspark]

using a 3000rpm motor well geared down does not increase the hp .use a 1450 rpm or there abouts

 

[Cuthy246]

I know it doesn't increase the HP was more thinking of the extra torque from the added mechanical advantage of a lower ratio. Or would a 3hp 1450 with an 11" pulley and ratio of 1:2 be more suited??? Sadly can't get 3ph to my garage without massive expense and large (>3kw single phase motors) are both expensive and hideously inefficient from what I've read. Am I right in thinking that the compressor will put out a certain pressure and the speed of rotation merely affects CFM output? Not fussed about getting the full CFM rating but would be nice to get 150psi in the tank.

 

[brightspark]

no extra torque with a faster motor reduced down I once thought that. if it was true everyone would be fitting them if it required a 5hp motor and you fit a 3hp it would need gearing down to pull it over without overload . it would still produce 150 psi but just at a slower rate

 

[bletchmonster]

Not 100% on this, but 1450 mptor is 4 pole as opposed to a 3000 4pm motor being 2 pole so 1450 has better starting torque.
I've put a 1450 motor on a compressor with a huge pulley on it to get the pump speed and it seems more torquey on start up

 

[Cuthy246]

Will give it a go with a 1450rpm 3hp and see what happens. If it's no good will have to go down the noisy petrol engine route. Or do the sensible thing and sell it to fund a more suitably sized one.... But where's the fun in that!

 

[knighty]

Cuthy246 can I have first dibs if you decide to sell it?

3phase here so powering it no problem

new machine coming at work needs 6bar 30cfm

bought a 30cfm hydrovane but could do with a backup!

 

[Cuthy246]

Knighty you can Indeed have first dibs if I do sell. But might be a while if I do as not allowed to post in selling section yet.

Cuthy246 can I have first dibs if you decide to sell it?

3phase here so powering it no problem

new machine coming at work needs 6bar 30cfm

bought a 30cfm hydrovane but could do with a backup!

 

[knighty]

no worries, I'm in no hurry :-)