Fan oven fans

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

  1. #12

    Expert

    Nov 30, 2010
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    Yes, those are bushings with felt for an oil reservoir.
    No, it's not for dissipating heat, it's a convection oven. The fans stir the air to break the surface layer of air to get the heat through quicker.
    I HAVE seen new motors with no lube in them! That's why I tear down every machine I install, before I arrive at the job.
    and, no, WD-40 is not oil. Don't do that!

    ps, I pull appliances out regularly. What makes this one difficult?
     
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  2. THE_RB

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    Thanks for the vote of confidence but apart from a small time during my apprenticeship 1981-84 and some repairs for friends and family I have never worked much with white goods. My main time in repairing was exclusively electronic goods TV/VID/audio and microwave ovens which I suppose are a form of white goods. (Or big radio transmitters, depends on your perspective ;)).

    I've replaced quite a few of those type fans in MWOs but I really couldn't say a "good" brand or type of motor. Generally we would order a Panasonic fan by model number for a Panasonic MWO. Or, with other brands or hard to find fans we would just order by frame size, wattage, etc, or even just from the picture in the catalogue for unsuual fan shapes and sizes.

    The main cause of failure is almost always bearing failure. They rarely blow windings (unless maybe AFTER bearing failure).

    Your fault is probably fan lube, that was not a good lube choice for the temperatures. A high temp oil suitable for fan bearings (simple bush type) may restore your dead fans and give you 10 years more fan life.
    :)
     
  3. #12

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    They (electronics) are called brown goods at Sears&Roebuck.
     
  4. bwilliams60

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    Nov 18, 2012
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    My experience is mostly rebuilding DC starter motors, generators and alternators but I have to agree with the rest in regards to this being a lubrication problem. If these are brass bushings, it is best to find a lubricant that can withstand the temperature and coat the inside and the shaft with the lubricant. If they are cintered bronze, we used to heat these up and allow them to cool in oil (temp rated). If they are bearings, we would remove them and replace them with a good reputable bearing that was prelubed and sealed. Again, temperature being the key because once they get hot, the lubricant will ooze out and then it will become tighter on startup. You can change motors and end up with the same problem. Try a company like SIEMENS and see if they have something comparable. They have a good reputation but not sure if they deal with this kind of motor. Good luck
     
  5. Brevor

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    Wow Little Ghostman, when I was a youth I guess I was a "stig of the dump" too.
    The dump was the coolest place in town.
     
  6. studiot

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    Thanks for all the useful advice folks, keep it coming.

    :)
     
  7. ian field

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    If the bushes are really stiff, penetrating oil might be a good idea, it can dissolve the dried out lubricant residue and any carbonised deposits.

    There is a competing product to WD40; GT85 which contains PTFE (probably others too) - but the warning stands, penetrating oil washes any lubricant out, so you have to follow up with replacement oil into the bushes.
     
  8. alfacliff

    Well-Known Member

    Dec 13, 2013
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    many of these types of motors have cooling fans on the back end of the shaft. can you fabricate a cooling shroud or duct for the fan motors?
     
  9. MaxHeadRoom

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    It may be possible to fit Oilite bronze in place of the usual cheaper brass, if possible.
    I have tried relubing the existing cheap bearings, but it does not last, and you have had the failure in a relative early time.
    Max.
     
  10. studiot

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    Yes there is one in the picture.

    The fan motor and its cooling fan is mounted directly onto the back wall of the oven.
    It is in a free air space approx 1.5 times the height of the motor/cooling fan assembly ie about 75 mm and the size of the back of the cooker, ie 850 x 450.
    It is covered by a vented sheet metal plate.

    So I can't see any ducting helping.

    I think those who council working on the bearings are right.
    I will be investigating them further.

    The net if full of tales of woe of early failure of these things (cheap bearings).
     
    Last edited: Apr 29, 2014
  11. debe

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    Sep 21, 2010
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    We have a Emilia fan forced gas oven & its 6yrs old & no problem with the fan yet!! This oven when turned off, the fan continues for quite some time to cool the oven down. Still wonder wheather some fans aren't lubricated properly when manufactured?
     
  12. THE_RB

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    It's all down to lube. Cheap China lube that works ok in gentle temps (like a pedestal fan) will go real bad in an oven fan.

    I'm also wary of PTFE lubes. Teflon in lubes is a suspended solid, so as the liquid part of the lube dries out and gets gummier, having a suspended solid makes it go real bad real quick.

    Just a medium weight oil, rated for high temperatures so it doesn't get gummy after extended time at high temps. I used to use a two-stroke engine oil, it's great at high temps because its designed to stay wet and lubricate well even at combustion temps inside an engine.

    And I used to lube new fan bearings before putting the fan in use. That probably increased their life by a great deal.
     
  13. Alec_t

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    A last ditch option (subject to wifely approval ;)) would be to mount the motor/fan assembly on a metal plate and hack a hole in the back of the oven big enough to allow the assembly to be withdrawn from the inside of the oven for periodic oiling/servicing. The plate would normally cover the hole and could be attached by self-tappers to the oven back.
     
  14. sirch2

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    Jan 21, 2013
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    I have to say that sounds a bit drastic and how would you insulate it etc. The fan in my oven has run almost daily for 14 years without any servicing what so ever and must have done many thousands of hours.

    It has to be better to fit a quality part than start hacking at the oven.
     
  15. studiot

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    I'm open to suggestions on sources.

    That's actually quite a good idea. I will look into my trepanning kit. I think I have an adjustable tank cutter that has a large enough radius arm.
    I would also have to extend the supply cables to allow the assembly to be pulled forward.
     
  16. sirch2

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  17. THE_RB

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    They all have the same little crappy bronze bush bearings.

    It's not the lonevity of the FAN, it's the longevity of the OIL. :)
     
  18. MaxHeadRoom

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    Not all.
    The higher quality use the sintered bronze type such as Oilite oil impregnated that are porous and retain oil for a much greater length of time.
    It is just a cost cutting corner on construction.
    Max.
     
    Last edited: Apr 29, 2014
  19. ian field

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    Horses for courses - sometimes crappy bronze bearings are the best for the job.
     
  20. THE_RB

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    Agreed, my point was they won't use ball bearings (because of high-temp app), only bush type which are always very lube-critical.

    Oils aint oils. :)
     
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