rogerrabbitt

Re: compressor motor power

Sun May 30, 2010 12:11 pm

the 5 hp gas motor was running
a 9 3/4 inch pulley and that wouldn't drive it either.

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antique diver
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Re: compressor motor power

Sun May 30, 2010 12:37 pm

rogerrabbitt wrote:ok the biggest equipment i run is a low pressure vtwin compressor
it's 3kw but it has to start with an open valve until it kicks in properly.
the diving compressor turns over maybe five times then labours and blows a fuse.
and it's huge i'm no big feller but i have trouble lifting it.its about 25 percent bigger physically than the other 3kw motor i have
11 inch pully.
First thing is make sure that your compressor is turning easily and smoothly when rotated by hand and no belt on it. Also when you try running it, make sure no other electrical items are on at the same time, thus sapping off some of your available amps. Also check your incoming voltage with a meter! If it is much lower than the motor rating it will cause a higher amp draw and might stall out the motor under load. Also start the compressor running with the condensate drain valves open to let the rpm get up before "loading" the compressor by closing the drains. The 1st and second stages have larger pistons and cause more initial strain on the motor than the others.... so be sure they are draining and not compressing.

Important consideration: Your motor could have a bad "start capacitor" which gives a single phase motor a little extra voltage kick during the high power (amp) draw of starting the equipment turning. If you can have that checked first it might save you a lot of trouble. Also, I assume that the motor runs ok when not connected by belts to the compressor... if you haven't tried that do it now. If that's ok, proceed to check the start capacitors. I see two attached to the motor. If you have an older volt/ohm meter with a needle instead of digital, you can give it a basic test but it's not foolproof: disconnect all power to the motor. Access the capacitor terminals, but note that if you have tried running it recently, the cap (capacitor) may be "charged" and give you a nasty jolt, so short across the terminals with a screwdriver to discharge it while only touching the plastic handle. Then note what wires go where and write it down. Remove wires from cap and turn ohmmeter on. Touch red wire to one cap terminal and black wire to the other while carefully watching the needle. It may jump a little. This has given a tiny charge to the cap from the battery in the meter. Then reverse the red and black wires and watch closely as you touch the terminals with them again. You should see the needle jump slightly as it discharges its stored charge. This is a rudimentary check and does not tell the full story, but if no "jump" on that second step you may have a bad cap. If needle jumps a little proceed to next idea.

Don't worry about physical size as related to power of the motor, as different frame types and even motor age can vary widely in that respect.

Next you might try the other motor if it has a smaller drive pulley... or put a significantly smaller pulley on your existing motor and see if that works better. It will then require less power to turn the compressor, thus drawing less amps and maybe not overloading your circuits.

Try all that for now and give us a report.
The older I get the better I was.

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antique diver
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Re: compressor motor power

Sun May 30, 2010 12:42 pm

I just edited that slightly after looking closer at the motor and seeing that the two capacitors were exposed instead of in a box. So, if you read something I initially wrote about them being in a box on the motor, disregard that comment.
The older I get the better I was.

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captain
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Re: compressor motor power

Sun May 30, 2010 1:32 pm

OK let me get this straight.
Motor 11" pulley 1410 RPM
Compressor 16" pulley 969 RPM

You are only getting a torque multiplication ratio of 1.5
Going to a higher speed motor of the same HP and a smaller motor pulley will increase starting torque and may solve most of the problem.
969 RPM compressor speed seems a little slow for that small a unit.
Do you have any manufactures specification on max compressor speed and motor RPM. Could be it is not the original motor and is not correct for your application.

By contrast I have a 7" compressor pulley and a 2.75" motor pulley so I am getting 2.5 torque multiplication.
Captain

rogerrabbitt

Re: compressor motor power

Sun May 30, 2010 2:31 pm

wow thanks to all of you
for the invaluable help,i'm in town this week so i'll
check out some smaller pulleys to start
and run the motor up without any load and see what i get.
i will post all results as soon as i've checked everything.
kindest regards roger.

rogerrabbitt

Re: compressor motor power

Thu Jun 03, 2010 11:56 am

Gentlemen i salute you.
today i filled my own tanks with my compressor.
this is a culmination of four years messing about with
a dead dive shop compressor bought off ebay for repair.
i ran the compressor motor up without any load which
was very successfull.i then fabricated a slightly smaller belt pulley.
11 inch down to 9 inch,from PLY WOOD.
i then bolted this to the existing pulley with six bolts ,
first run we managed just under 100 bar
then it threw a belt,after adjusting the belt tension the second run managed just under 150 bar but threw up a leak issue on the filter tower.after fabricating an "o" ring from 4 mm "o" ring material the leak was fixed.third run i filled my vintage italian tank to 150 bar,fourth run i filled my normal 7 litre tank to 200 bar and fifth run i filled my 12 litre tank also to 200 bar.
i am extremely happy to be able to fill my own tanks at last
a very big THANK YOU to everybody for help and advice on the motor problems .
hopefully now i can get MORE diving in this year and contribute more to vintagedoublehose.if it wasn't for you guys i would not have persevered and pulled the stops out to fix this unit.
kindest regards roger from bulgaria.
anybody build their own dive helmets ?????

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Bryan
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Re: compressor motor power

Thu Jun 03, 2010 12:49 pm

Very good news to hear. Congratulations! Building a pulley from plywood is very impressive. Please post a picture of that for us. We are too spoiled here in the US where we can get most items anytime we want.
Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

rogerrabbitt

Re: compressor motor power

Thu Jun 03, 2010 2:26 pm

here for your delectation and amusement is
"THE WOODEN PULLEY"
i do hope you all have a good laugh,
but for us it means freedom from the 100 mile
round trip for a fill.
kindest regards to all of you.
from roger and dawn in bulgaria.
sure nobody builds their own diving helmets on here ???
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Bryan
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Re: compressor motor power

Thu Jun 03, 2010 2:33 pm

Not laughing at all. You took what materials you had to work with and solved the problem. If I get stranded on an island I hope there are a lot of creative people like you around!
Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

rogerrabbitt

Re: compressor motor power

Thu Jun 03, 2010 2:56 pm

Bryan many thanks
we look at the result with hapiness
four years of long trips to get a fill are not fun
vintagedoublehose is like an oasis for us
as we can actually converse with like minded people.
viva "vintagedoublehose"
regards roger and dawn.
we'll try and post pics of our adventures here sometime.
i just wanna know any helmet builders here !!!!!!

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antique diver
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Re: compressor motor power

Thu Jun 03, 2010 5:04 pm

Roger,
Congratulations on your success and your ingenuity in fabricating a successful wooden pulley!!! You will probably be giving us some good advice soon!

Isn't it great pumping your own air? :D

Bill
The older I get the better I was.

rogerrabbitt

Re: compressor motor power

Fri Jun 04, 2010 2:52 am

Bill
it's fantastic pumping our own air at last,
dawn and i got very drunk last night celebrating our new
found independance,all thanks to you guys for the help.
roger and dawn.

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antique diver
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Joined: Sun Dec 10, 2006 12:50 pm
First Name: Bill
Location: North-Central Texas

Re: compressor motor power

Fri Jun 04, 2010 7:52 am

I'm beginning to think we might see a custom made wooden diving helmet come out of Bulgaria some day! I'm sure it will work too!
The older I get the better I was.

rogerrabbitt

Re: compressor motor power

Fri Jun 04, 2010 7:59 am

haha
i'll post some pics soon
regards roger and dawn

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Bryan
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Re: compressor motor power

Fri Jun 04, 2010 8:00 am

rogerrabbitt wrote:Bill
it's fantastic pumping our own air at last,
dawn and i got very drunk last night celebrating our new
found independance,all thanks to you guys for the help.
roger and dawn.

We need a trip to Bulgaria.. Compressor building, diving , drinking! Good times for everyone!
Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

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