Band saw

[Howard LewisParticipant @howardlewis46836]

Out of the box, the generoc saw worked reasonably well.(It worked even better after it had been fettled and adjusted)

The only reason for changing the bearings was that the incredibly skinny bearing spacer failed, and ruined the lower bearing and oil seal, so my hand was forced.

“As received”, careful alignment and adjustment should result in a quite useable machine.

Setting the blade tension correctly will greatly extend blade life.

Howard

[JasonBModerator @jasonb]

Just measured my Femi holding the phone at head height.

82dB on slow and 86dB on fast. so about half the noise level of what yours is making.

[Adam HarrisParticipant @adamharris13683]

I have removed the blade and the dB sound level is the same – ie it is the motor and nothing to do with the blade wheels or guides

[Adam HarrisParticipant @adamharris13683]

Jason, very interesting and thank you so much for the effort in measuring yours. As it is purely the motor creating this noise (maybe a reduction gearbox too through which the motor spindle drives the wheel?), it is difficult to know what to do next. I will disassemble the motor and see if I can improve the spindle bearings or at least check the grease levels

[Adam HarrisParticipant @adamharris13683]

I have checked with Chester and they have just tested some other 85M machines/motors in stock and found them all similarly very very loud (ie 92dB or more at min revs), and since the motors and machines are all the same as the generic chinese BS-85 one can only assume that the official documentation stating these BS-85 bandsaws produce sound levels of 82dB at min revs is simply a load of hogwash, probably a pretence in order to compete with the Femi. I’m going to pull the motor apart and see what the issue is and if any mods can reduce the noise.

[MacolmParticipant @macolm]

I assume all the band saws we are considering have universal (commutator) motors. My quite old Femi certainly does. The main noise, therefore, most likely comes from the armature fan. This is present both for cooling the windings but also to present a rising load characteristic with increasing speed in order to limit the maximum speed on light load.

On my Femi, a slotted end cover limits the fan airflow. With this removed, the noise is greatly increased, so it is presumably there to manage the noise level. Do the Far East saws have anything similar?

[Adam HarrisParticipant @adamharris13683]

Hi Malcolm, spot on! I have removed the motor and the noise only drops by 2-3dB so the gearbox is not the culprit. It is a regular commutator motor, bearings appear smooth so I also suspect the fan as it cannot really be anything else. So I have flattened the vanes somewhat in the hope of reducing noise but have yet to get it back in between the pair of sprung carbon brushes! I am looking for some long steel shim strips gone missing and will revert. Many thanks

[MacolmParticipant @macolm]

If the brushes have spiral “snail shape” springs, you can sometimes offset them to bear against the side of the brushes so as to hold them clear. Then pry them to the proper position once assembled. May need some bent wire manipulation.

[Adam HarrisParticipant @adamharris13683]

A decent length of shim steel works well with carbon brushes. Anyway, I flattened the vanes to 50% of their angle and got a 2dB improvement, then flattened them further until hardly any angle and got a further 2dB improvement at max speed and no further improvement at min speed. Still decent airflow. So now I am at 90 dB min speed and 94dB max speed. Quite a noticeable improvement and better harmonics to my ears. If I put a sound canopy over the slotted end cover where the air intake occurs, leaving a gap of 5-10mm I do get a further 2dB reduction both at min and at max speed so I think that is worth doing as a future project . However I think the fan design is the real issue and  I will look for a better designed and smaller fan, maybe try to buy the Femi fan as a Femi spares part, or maybe the whole motor if cheap enough and can be fitted to my gearbox! I attach a photo of the innards for any who are interested. Very many thanks Malcolm and Jason for your contributions.

[Adam HarrisParticipant @adamharris13683]

[Adam HarrisParticipant @adamharris13683]

[Adam HarrisParticipant @adamharris13683]

Very many thanks Malcolm and Jason for your contributions.

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