Rebalancing a largish fan rotor?

DanniAgro

Member
Just refettling an 11kW fan for a grain drier. The fan is about 3 ft diameter and because it's been left outside, the assembly must be rebalanced, so was wondering if anyone had any ideas for doing it.
At the moment I was just going to turn it gently by hand and after seeing where it stopped, adding small weights to try to balance it again. This seems on consideration to be possibly a very long winded process, so can anyone help with suggestions to speed the whole process up, and possibly make it more scientific?
Cheers in advance for your ideas.
 

Fuzzy

Member
Arable Farmer
Location
Bedfordshire
Just refettling an 11kW fan for a grain drier. The fan is about 3 ft diameter and because it's been left outside, the assembly must be rebalanced, so was wondering if anyone had any ideas for doing it.
At the moment I was just going to turn it gently by hand and after seeing where it stopped, adding small weights to try to balance it again. This seems on consideration to be possibly a very long winded process, so can anyone help with suggestions to speed the whole process up, and possibly make it more scientific?
Cheers in advance for your ideas.
Try running it up first, if no vibration do nothing!
 

DanniAgro

Member

DanniAgro

Member
Why do you think it needs balancing? Have you been welding it ?
Part of it was exposed to the elements and scaling meant that one side lost some metal, and when I tried several small hand aided rotations, it always stops at the same place. But the giveaway is that it starts to turn backwards when it's passed the preferred stoping point.
 

Wisconsonian

Member
Trade
If it's just a fan, not a wider blower wheel, then static balancing should be fine. Just the way you're thinking will work. Spin it past the place it wants to stop and keep adding until it doesn't seem to want to stop the same place. Then mark it and spin it good a dozen times and record the location it stops. So get at least ten rotations on it and if it doesn't have a pattern out of a dozen stops, that's close enough.
 

Dry Rot

Member
Livestock Farmer
Assuming the fan is on some sort of horizontal shaft, friction will play a part if you try to balance it by spinning it on the shaft.

Take it off, get a boss turned to fit into the hole that is now revealed with a depression in the centre. Spin the fan balanced on a point and add counter weights as above. Friction is now almost eliminated.
 

DanniAgro

Member
The method we used doing static balance was to add plasticine to the light side until balance is achieved. Then weigh it and add metal in the form of a welded plate. A bolt with varying numbers of washers is another way of doing ithe only trouble is finding the plasticine!
The only trouble will be finding the plasticine!
Seriously though, that seems to be the best method I can think of.
 

DanniAgro

Member
Assuming the fan is on some sort of horizontal shaft, friction will play a part if you try to balance it by spinning it on the shaft.

Take it off, get a boss turned to fit into the hole that is now revealed with a depression in the centre. Spin the fan balanced on a point and add counter weights as above. Friction is now almost eliminated.
You'd think that would be true, but I find that every time I give it a spin it always stops at the same place, and the fact that it reverses rotation in order to get back to that point makes me feel that friction in the bearings isn't important in this case.
 

Chieftain

Member
Mixed Farmer
Location
Nottinghamshire
Is it just a fan on a horizontal shaft? If so just find the centre of mass of the fan part (assuming you can take it off the shaft) then put a mass on the opposite side of the eccentricity to balance it statically.
 

DanniAgro

Member
Just refitting the fan in its housing after getting it balanced by the experts.
I tried the plasticine method and got what seemed to be a good balance. However when it was randomly spun by hand, it seemed to be still avoiding stopping in some areas after 30 or 40 spins, so obviously needed more balancing than I was capable of.
Ringing Hereford Rewinds revealed that they would do the job for £75, taking about two hours, so I took the fan into them (it was still not installed on the motor permanently) and got it back the next day. They'd welded five pieces of plate of differing sizes onto very different places plus two areas of weld for smaller weight. It makes me wonder how well balanced it was originally, as a lot of the added weight didn't seem to be related to the bad scaling caused by leaving it outside.
So all you wise guys who said I should get it done professionally were quite right, it was just the price I was worried about, but it was very reasonable after all.
 

thesilentone

Member
NFFN Member
Location
Cumbria
Just refitting the fan in its housing after getting it balanced by the experts.
I tried the plasticine method and got what seemed to be a good balance. However when it was randomly spun by hand, it seemed to be still avoiding stopping in some areas after 30 or 40 spins, so obviously needed more balancing than I was capable of.
Ringing Hereford Rewinds revealed that they would do the job for £75, taking about two hours, so I took the fan into them (it was still not installed on the motor permanently) and got it back the next day. They'd welded five pieces of plate of differing sizes onto very different places plus two areas of weld for smaller weight. It makes me wonder how well balanced it was originally, as a lot of the added weight didn't seem to be related to the bad scaling caused by leaving it outside.
So all you wise guys who said I should get it done professionally were quite right, it was just the price I was worried about, but it was very reasonable after all.
Money well spent.

A small frequency can be very, very expensive.
 

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Man fined £300 for bonfire-related waste offences

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Written by William Kellett from Agriland

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A man has pleaded guilty at Newtownards Magistrates’ Court to waste offences relating to a bonfire next to the electrical sub-station on the Circular Road in Newtownards, Co. Down.

Gareth Gill (51) of Abbot’s Walk, Newtownards pleaded guilty to two charges under the Waste and Contaminated Land (Northern Ireland) Order 1997, for which he was fined £150 each and ordered to pay a £15 offender’s levy

On June 25, 2018, PSNI officers went to Gill’s yard, where they found a large amount of waste consisting of scrap wood, pallets, carpet and underlay.

Discussion with Northern Ireland Environment Agency (NIEA) officers confirmed the site...
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