Fan oven fans

Discussion in 'General Electronics Chat' started by studiot, Apr 27, 2014.

  1. studiot

    Thread Starter AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Our new (we consider it new) range cooker as in pic1 has two electric fan ovens.

    Shortly after the guarantee period one fan failed, then the other.

    the cooker has had relatively light use and not been abused.

    The fans are mounted on the backs of the oven walls so need the whole range to be pulled out to access them.
    All you can see inside the oven is the shaft and the fan.
     
  2. antonv

    Member

    Nov 27, 2012
    149
    27
    Do you have a question?
     
  3. studiot

    Thread Starter AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    As you can see from the pics, I mounted one of the fans on a backboard and tested.

    The core of the motor reaches at least 46°C. I say at least because of the thermal contact with my thermometer when run in the open air. this seems excessive to me.

    Since breaking the kitchen apart to pull out the cooker is significantly disruptive and costly I would appreciate comments that allow me to put back something that will last much longer.
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,789
    1,103
    Edit:
    If the motor itself is creating the unwanted heat (you're getting 46C when its mounted on the board, not the stove?) the only solution I see is to replace the motor with a more efficient one.
     
    Last edited: Apr 27, 2014
  5. Little Ghostman

    Member

    Jan 1, 2014
    294
    97

    I am a bit of what dad calls stig of the dump, I rummage around at the dump and have played with these a bit, its common for them to get hot under normal running, every one I have tried reached 50-60C no problem.
    I never measured how much current they were pulling but I think its a good amount, if you look at the construction, the coil looks pretty inefficient for a motor, I am no expert on this however.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,520
    2,369
    This is your basic shaded pole motor/fan, the copper shading ring (you can see it in the pic) is actually a shorted turn, so they tend to run hot due to this.
    These fans do not like any kind of friction, so when the bearings go dry, they tend to stall!.
    Max.
     
  7. studiot

    Thread Starter AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Thank you for the replies, but what I need is suggestions for a replacement fan that will not fail prematurely.
    The cost, annoyance and disruption of replacement far outweighs the cost of the fans themselves.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,520
    2,369
    What I would tend to do initially is to see if I can find out what causes the failure in the first place, I don't see it motor burn out, so that virtually leaves bearings?
    They are a real simple device.
    The alternative is to visit a local motor supplier that has these type of motors on the shelf and see if they can offer a higher quality alternative?
    Max.
     
  9. studiot

    Thread Starter AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    No the motor hasn't burnt out.

    This was the first fan oven we have ever had, and I am appalled that a respectable (*!#?) manufacturer installs a motor that, in my view, is just not Max (sorry man) enough for the job.

    What I really need is comments form some members who have had lots of experience of these things (such as RB).

    :)
     
    Last edited: Apr 27, 2014
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,520
    2,369
    Different experience in what way?:confused:
    I have worked with motors my whole career, which originated in the UK by the way.
    Max.
     
    Last edited: Apr 27, 2014
  11. studiot

    Thread Starter AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    This is no disrespect, Max.

    I need two replacement motors that will be better than those originally installed by Belling.
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,520
    2,369
    I would imagine that unless the oven is made in Australia, the only thing in common is a source of 240v motors?

    You mentioned that you mounted them to a board and they ran, but hot.
    I am assuming that when they quit on the oven, you were sure the power was still on them??
    Max.
     
  13. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    The best check would be to give the fan blades a nudge and see if the motor is even trying.

    This type of motor usually uses phosphor-bronze bearings, but whatever type the heat is going to dry them out.

    Maybe a PTFE based lubricant like Slic-50 - at least when the oil dries out, it leaves a low friction coating of PTFE.
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,520
    2,369
    Yes. Usually known as Oilite, porous Bronze, oil impregnated.
    http://www.oilite.com/bearings.asp
    We used to remove them and re-soak them in oil, but this is usually after many hrs of operation.
    Max.
     
  15. bwilliams60

    Active Member

    Nov 18, 2012
    722
    88
    Sorry, stupid question but you say they failed and yet they run on a board. Can you be more specific about the failure? Stopped turning/started smoking/ran slow????
     
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,520
    2,369
    Why a stupid question? :cool:
    Max.
     
  17. #12

    Expert

    Nov 30, 2010
    16,261
    6,774
    Two more cents coming at you:

    We all know shaded pole motors are the feeblest sort. Everything about them is cheap and meant to be throw-away. The idea I have is to get a small induction motor and try to mount it a few inches farther from the heat of the oven or offset it with a belt or a gear.

    Not being too educated about motors, I clicked a coupla pix in my junque pile.
    This kind:
     
  18. studiot

    Thread Starter AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Not a stupid question.

    The motors were in service maybe 6 times a week, between them, for maybe 15 months.

    Then one fan failed to start.

    It would start after nudging the fan a bit.

    Then it failed to start altogether.

    I dis manage to get it running by squirting in some WD40 through the small shaft hole and manually spinning the blades to try to work the lube along.

    Then the other started the same, as it received more use.

    Eventually both failed to start so I have had to dismantel an expensive kitchen isntallation (the cooker is built in) to pull the cooker forward to remove the fans and test them.

    Both fans were moderately stiff to turn - they did not rotate more than a couple of turns by them selveswhen spun.

    It was immediatedly apparent that there is no easy path for lube from inside the oven. However it was possible to ease up both fans once removed.

    They were then mounted on the board for testing, in the same manner as they were mounted on the back plate/wall of the oven.

    So far as I can tell the shafts have one have plain bearing in the centre of the mounting spider boss and one encapsulated end bearing at the outside end of the motor. I cannot tell if they are bronze, but I doubt it. They feel too smooth for ball bearings, although the end cap is large enough for a tiny race, so they nay also be a plain bushing by El Cheapo inc.

    Commercial standard replacement assemblies are £15 from CPC-Farnell so not expensive, but they look the same rubbish build in the CPC pic.

    My worry is that if I simply bolt them (or similar new ones) back into place they will soon fail again.
     
  19. debe

    Well-Known Member

    Sep 21, 2010
    946
    184
    This is what I do with oven fans that are stiff to turn. Just dismantle & check if bearings are still ok & re lube the Felt pad in side generously & re assemble. I use industrial sewing machine oil. One wonders if the felt pad is well lubed from new??? It is a harsh environment but ive never seen any beter designed motors for the job.
     
    studiot likes this.
  20. Lundwall_Paul

    Member

    Oct 18, 2011
    220
    19
    If you are using fans to dissipate heat from an oven I wouldn't use wood to mount them. I would also let heat pass through the fan like using a large hole between the two blades.
     
Loading...