Thread: Ideas for making a motor fan

Originally Posted by BobL

I fitted the 240V 120 mm fan inside the regular fan housing and ran the motor for 2 hours last night. The shaft temperature after a 2 hour run was 29º (Ambient was 25º) so it seems like it's running OK.
I don't like the noise the fan makes, some of this is probably the grille profile - might have a bit of a fiddle with that and see if I can improve it.

but was the motor under load for those temps?...no load the motor wont get very hot.

Originally Posted by eskimo

but was the motor under load for those temps?...no load the motor wont get very hot.

Sure - yes no load. I've been using "no load temps" to identify problems like sticky bearings etc. On one motor, the shaft temp got up to ~50º just free running. after a lot of mucking about I identified this with a poorly assembled motor where one bearing was not seating properly into its end cap so the thrust spring under the other bearing was probably totally crushed. A few from taps of a wooden mailet seated the tight bearing and reduced the pressure on the thrust spring and the shaft temp dropped by ~20º

Originally Posted by BobL

Sure - yes no load. I've been using "no load temps" to identify problems like sticky bearings etc. On one motor, the shaft temp got up to ~50º just free running. after a lot of mucking about I identified this with a poorly assembled motor where one bearing was not seating properly into its end cap so the thrust spring under the other bearing was probably totally crushed. A few from taps of a wooden mailet seated the tight bearing and reduced the pressure on the thrust spring and the shaft temp dropped by ~20º

that was overheating due to mechanical fault.

Motor under full load conditions (max amps) will also cause motor to warm up, and which will prove if if you have it right.

I would go for the external fan; you can get some good prices if you look for used pieces

Originally Posted by Jon_B

I would go for the external fan; you can get some good prices if you look for used pieces

I did that already - see post #14.

Paul McGee like pictures so here is one of a small (0.25 HP Y connection 415V) motor that I found in a skip big where I used to work.

It meggered OK and gave consistent coil readings so I thought I would use it as a practice run for Y to 240 ∆ conversion.
The internal insulation was strong but brittle and I ended up prying/shattering/chewing open 4 connections before finding the common point.
There was plenty of room inside for the extra wiring and I covered all the opened connections up with fibreglass sleeves and smothered it in HT silicone and it came together easily enough.

It had some corrosion on the main motor case and the aluminium fan casing so I ran a wire wheel over it and gave it my standard motor paint colour treatment.
This is a nice little motor, It seems to have a bit more grunt than 1/4HP but without a dyno I'll not really know - yet another reason to make one.

What am I going to use it for, nothing yet, It's going back into my motor stash till I find a need for it, I have another just like it that also could used some TLC

I find it a little interesting that there is a 1/4hp 3phase motor ... not astonished, just interested.

I assume it isn't 3ph over 1ph for current-draw, so ... torque? reliability? keeping loads balanced on a 3ph wiring system?

Just curious.

When I asked about a picture, I was imagining 3ph like this ... ...

20140327_220939 (Medium).jpg

Cheers,
Paul

Could be a smaller part of a larger 3 phase machine so it is done for balance. Another possibility is that 3 phase motors are smoother than single phase and don't need a separate starting mechanism, so if used intermittently that could be a reason too.

Michael

Originally Posted by pmcgee

I find it a little interesting that there is a 1/4hp 3phase motor ... not astonished, just interested.
I assume it isn't 3ph over 1ph for current-draw, so ... torque? reliability? keeping loads balanced on a 3ph wiring system?
Just curious.

The motor came out of a skip but it was attached to a fume hood that has been running continuously since 1966, and its still in running condition.