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Featured One of my wheelchair motors overheats and stops working

  1. Apr 21, 2018 #1
    Hi can anyone help. I use an electric wheelchair to get around and can only walk a few steps with a wheeled walker. Yesterday I went to my local out of town ASDA, a 1.5 mile trip approx through an alley/Public Footpath, I have done this many times before. This time I was about 3/4 of the way there and the chair started to judder and slow down and pull to the right. It then stopped and after a quick look the right hand motor was hot enough to literally blister my finger whilst the left hand one was touchably warm. I waited for a while and the chair switched on and moved a short way (100mtrs or so) then started to judder again, so I stopped again. My only thought was to get to ASDA and get help so I looked in the backpack on the chair in the hope of finding something to cool it down like a forgotten water bottle. All I found was a 500 ml bottle of Oilatum ( a liquid paraffin skin treatment) I poured half of this over the motor and waited for 1/2 hr and then poured the rest of the liquid over it to cool it even more so I could get to the supermarket and get help. I got to ASDA and the motor was much cooler. I went to the cafe and turned it off for an hour and then switched on and did my shopping, checking the temp of the now cool motor every few mins. It did not overheat so I continued my homeward journey, the motor stayed at the same temp as the other one and did not get hot even though the return journey is more uphill. Does this mean the motors need lubrication or was this coincidence?
     
  2. jcsd
  3. Apr 21, 2018 #2

    jim hardy

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    Sure sounds that way. Does it have a spot to apply oil to the bearings? Does the user manual mention lubrication ?

    Have you a photograph of it?
     
  4. Apr 21, 2018 #3

    anorlunda

    Staff: Mentor

    Hmm. If it was lack of lubrication there would be no reason for the temperature to return to normal when you got back to pavement.

    One guess is that it vibration caused by the footpath being rougher than the pavement. There might be a loose electrical connection somewhere that stays connected except when there is vibration.

    Can you test it by driving over a lawn or some rough ground closer to home? Just drive a short distance and see if the motor begins to warm up.

    I'm thinking of a terminal like the ones below when the nuts are not tight.
    slask.png
     
    Last edited: Apr 21, 2018
  5. Apr 21, 2018 #4

    Hi, thanks for responding. The problem with equipment for disabled people is that most manufacturers (understandably) assume people with disabilities can't do their own maintainence so only give operating instructions not manuals. I can do most things except walk and I cannot afford the large amounts quoted just to look at it. As a PC hardware support and repair engineer when I was working I am quite practical but don't know enough about DC motors to know if routine lubrication is required I have emailed Invacare (the manufacturer) but on past experience I do not expect a reply except the usual "Contact our service dept. and arrange your repair" which was the reply I got when asking how to replace the batteries, I was quoted £375 to supply and fit them, I bought a brand new set with a 6 year warranty from Amazon for £110 and fitted them myself in 30 mins. Really just need to know if DC motors require periodic lubrication normally. I cannot see any lubrication points but given what happened I can see no other explanation.
    Regards Roy
     
  6. Apr 21, 2018 #5
    Hi, thanks for responding. I think you misunderstood, i was on a paved but deserted public footpath not a roadside pavement, and the left hand motor was just warm, as they both usually are. It started to judder and pull right then switched itself off. I waited for it to cool a bit until it would turn back on. It soon stopped again due to getting hotter again. I then found the Oilatum in my bag and used the liquid to help cool it quicker so I could get out of the deserted alleyway where I was vulnerable to mugging etc After pouring the liquid I waited for a fair while it cooled down so it was much cooler. Then when I carried on to the supermarket it cooled down even more WHILST IN USE so whatever caused it to overheat was no longer happening. Logically the only conclusion is the Oilatum lubricated the bearings or similar. So my question is, do these motors need regular lubrication.
    Regards Roy
     
  7. Apr 21, 2018 #6

    256bits

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    Overheating motor.
    Other areas to consider
    You also have a gearbox.
    You also have an axle from the gearbox to the wheel.
    Both of those two points could have been putting more stress on the motor causing it to overheat.
    How.
    Grease in the gearbox is drying out.
    Axle bearing is failing.
    The axle could have also picked up a plastic bag, twine, that wrapped itself around.
    an alley is a good place to pickup stuff.
    The paraffin drip onto the axle can act as a lubricant, until next time if that is the case.
    ( Maybe a cat is stuck in there - any meuwing sounds ::rolleyes: )
    ( Vacuum cleaner beaters have a tendancy to pick up and wrap stuff around the axle and fail that way.
    People throw them out without looking for the cause )
    Front wheel could could be misaligned.

    I think the whole machine should just be looked at places that can produce stress on the motor.
     
  8. Apr 21, 2018 #7
    Hi, This is an electric wheelchair each rear wheel has a motor directly connected to it so there is no gearbox or axle, This won't let me post a picture but it is an Invacare Mirage Electric Wheelchair, there are many images of it on Google.
     
  9. Apr 21, 2018 #8

    anorlunda

    Staff: Mentor

    That is not the only possible conclusion. Experienced troubleshooters will tell you that the worst mistake they can make is to leap to one theory prematurely. It is like the homicide detective who blinds himself by prematurely thinking that the butler did it.

    A loose connection is still possible. Several of the other things that @256bits said are still possible.

    Unless there is a defect in manufacture, it would be very unusual for bearings on a DC motor to lose their lubrication within the normal lifetime of the machine.
     
  10. Apr 21, 2018 #9
    You can see a small cap on the motor, one or both ends, if it indeed takes oil. Some motors are permanently lubed and so sealed and it is difficult to get oil inside. Look at the motor if you can get to it and see if there is a little cap that swings up to allow oiling. If not, you might try squirting penetrating oil, like liquid wrench onto the outside of the bearings shooting on the shaft, maybe that will get some oil inside.

    Also, look for wheel bearings needing oil too, if the motor starts overheating again, try lifting up the hot side wheel and see if it spins freely when power is not applied. Also, if you can get to the motors and take them out, you might try reversing the motors left and right. If the same side overheats, there is something going on with the wheel, if it goes to the other side, the motor is the problem.
     
  11. Apr 21, 2018 #10

    256bits

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    ms26566_1.jpg
    That's the picture I get from for a wheelchair.
    It is a whole assembly.
    ( To post a picture, for windows, right click on the picture, copy all of the address from the popup, at PF at the top of the posting click on the picture icon ( right next to the smiley face ) , paste the address in the box Image URL , and then click INSERT. )
    That's the left side. Right side is similar.
    from
    https://www.mobilitysmart.cc/invaca...-gearbox-electromagnetic-brake-left-side.html
    https://www.mobilitysmart.cc/parts-spares-c-106/power-chair-parts.html

    the cylinder part is the DC motor.
    The rectangular part is the gearbox.
    The sliver disk looking part attaches to the wheel directly with bolts most likely. Call that the hub.
    From the hub to the gearbox is a shaft that can be called the axle.
    It seems that a clutch and brake are integral to the assembly. And those might be acting up also.
    They also have pictures of motor brushes, so I would naturally assume that those can be replaced if need be.

    It doesn't hurt to look that whole part over if you can.
     
  12. Apr 21, 2018 #11

    anorlunda

    Staff: Mentor

    Here'a another thing you can do to test. Buy or borrow a non-contact temperature gun. You can get one for less than £8.

    slask.png

    If a bearing or lubrication is the problem, the bearing will be warmer than the body of the motor. If the problem is electrical or due to excessive load, the body of the motor will be warmer than the bearings. If the gearbox, or the clutch is the trouble, then it will be the hottest point.
     
  13. Apr 21, 2018 #12

    Tom.G

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    Wheelchairs have brakes, often directly mounted on the back end of the motor shaft. They are typically multiple discs, similiar to a multiple disc clutch or the Coaster Brake on old single speed bicycles. They are applied by default and released when the motor is energized. It sounds like the brake did not fully release on that one motor. Perhaps due to dirt in it or a loose electrical connection. The other possibility is that motor has an intermittent short in it... but I would go with a stuck brake first, especially with your description "...started to judder and slow down and pull to the right."

    Wheelchairs generally have a manual brake release, sometimes called "freewheeling lever" or similiar, so the chair can be pushed if the drive fails. That would be a possible workaround the next time the situation arises. Depending on your tool inventory and mechanical adeptness, you can likely at least get access to the brake assembly for inspection. SInce the brake defaults to 'engaged' via a rather stiff spring, don't disassemble further than you can reassemble! It may just need a cleaning and debris removal.

    Oh, and the chair stopping in that situation is normal, the motors have a thermal overload in them for their self-protection.

    Please keep us updated on your findings and resolution.

    Cheers,
    Tom
     
  14. Apr 21, 2018 #13

    jim hardy

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    oops i got distracted... went out to look for an old wheelchair i have to see if it's same brand... several posts appeared in the meantime so this is out-of-date.. sorry 'bout that.
    ...............................................................................................................................................
    Aha ! Here's a Youtube of a handyman working on an Invacare wheelchair motor.

    His has a built in brake that's controlled by an electromagnet.
    He says the logic is ENERGIZE the electromagnet to RELEASE the brake. I guess that way it won't roll down a hill if the battery is dead.

    So that invites your observed trouble if there's an intermittent connection to that brake electromagnet.

    That seems to me a lot more likely than a sudden loss of lubrication.

    Intermittent connection explains the jerkiness, too.
    But that it fixed itself is worrisome. It'll come back, unless the motor wrecked the brake rendering it ineffective...

    What do you think ?
     
    Last edited: Apr 21, 2018
  15. Apr 22, 2018 #14
    Please do check the current and voltage with a multimeter for both the motors, in no load conditions and see these values are within the range of name plate , if its not, then the problem with motor or gear box or clutch.
    Usually the motor and gear box are fitted with life time lubricated bearingns

    Sent from my E5363 using Tapatalk
     
  16. Apr 22, 2018 #15
    Hi Tom, thanks for replying. I think you have solved my mystery. I thought the oil had done the job because it was the only thing that I changed between running hot and running warm BUT until you mentioned it I had forgotten the brakes, as you know Wed was extremely hot and where the chair stopped was in full sun, so I released the brakes manually to scoot backwards into the shade and then re-engaged the brakes to wait for it to cool down. If it was debris or dirt in the mechanism, manually operating them may well have dislodged any blockage. As for the thermal cutouts, these have come into play in the past but only on very hot days going up the steep hill near my home, on those occasions both motors stopped and I just waited for them to cool, press the reset buttons and away we go. On those occasions there was no juddering or slowing down, just running normally then stopping dead as you would expect, also the motor was nowhere near as hot then as it was this time but the cutout did not operate, so I think that it was the friction of binding brakes causing the heat. I will try to check the electrical connections and clean the brakes out this morning. Thank you again for your help.
    Best Regards
    Roy
     
  17. Apr 22, 2018 #16

    Thanks Jim, I think it probably was the brakes. Please see my reply to Tom G. Thanks again
    Roy
     
  18. Apr 22, 2018 #17

    anorlunda

    Staff: Mentor

    We should have a trophy badge, maybe "The Sherlock Holmes Award" In this thread, @Tom G would be the winner.

    Think of the process in threads similar to this one.
    1. The OP provides a description, usually very incomplete. In this thread, it was more complete than in many threads.
    2. The OP brings his own theory about the correct answer, thus introducing a bias.
    3. The OP asks a specific question (in this case " Does this mean the motors need lubrication or was this coincidence?" We can answer the question literally, or we can use critical thinking. In this case, critical thinking led us to think "That's the wrong question."
    4. In some threads (not this one) the OP might be offended if we don't answer literally. There's not much we can do about that.
    5. Actual replies ranged from literal, to "need more info", to general advice on troubleshooting not specific to wheelchairs, to wheelchair specific.
    6. In many threads (not this one) we get replies that comment on other replies, ignoring the OP question. That didn't happen here.
    I think this thread illustrates PF's engineering forums at their best. Kudos to everyone.
     
  19. Apr 22, 2018 #18
    Thank you, You are absolutely right, I expressed my theory (wrong as it turned out) and probably pointed responders in the wrong direction but happily, people looked for other causes and Tom Gs' suggestion made more sense. I have checked and cleaned the connections and removed years of grime from the brake mechanism and all seems well now, time will tell. I am going out later for quite a while in this hot weather so I will monitor the temp closely.
    I would never get offended by people trying to help me, there is no point asking for help if you don't listen to and evaluate their suggestions. Once again thank you to everyone that helped. Great site.
     
  20. Apr 22, 2018 #19

    jim hardy

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    As an old troubleshooter every problem is like a mystery novel (or short story).
    EDN magazine had a series called "Sherlock Ohms" where readers sent in their troubleshooting stories.

    And every old utility engineer remembers "Power" magazine's legendary "Marmaduke "
    https://en.wikipedia.org/wiki/Marmaduke_Surfaceblow
     
  21. Apr 22, 2018 #20

    anorlunda

    Staff: Mentor

    Oh yeah. I used to love the Marmaduke column. It was very well written.
     
  22. Apr 22, 2018 #21

    jim hardy

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    The humor was precious.
    No internet back then . It took me years to figure out the Ringelmann #5 cigar pun - Ringelmann is an opacity test for smokestacks..

    Ringlemann#5.jpg
     
  23. Apr 23, 2018 #22

    Tom.G

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    I would say that the most help in finding a (tentative) solution here was the clear and concise problem statement by the OP, @Roysmokie.
    As he is a technologist, he knew that details mattered and extraneous stuff was just that, extraneous.
    To give responders a starting point, you expressed a tentative conclusion based on the circumstances, the materials available, the observed results, and past experience. That's all any of us can do. In fact, in the Homework threads this is required.

    I had a suspicion about the brakes but the photo that @256bits posted, showing the extended rear cover on the motor, was the clincher.
    It just happened that I had worked with motors that had built-in brakes before; specifically about 50 years ago when developing controls for an anti-aircraft gun!

    As @anorlunda said, Kudos to everyone. And thanks for "The Sherlock Holmes Award" too. (Now if I can just find a frame for it... :wink:)

    Cheers,
    Tom
     
  24. Apr 23, 2018 #23

    OCR

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    Aw, heck... that should be elementary. . :wink:





    Well, somebody had to say it
    . . :-p
     
    Last edited: Apr 23, 2018
  25. Apr 24, 2018 #24
    Hi Jim,
    As expected, the following is the email I received back from Invacare, Still, they managed to deduce "there seems to be sort of problem". So now I know!
    Seriously though, I have used it all day yesterday and it was fine, so I think it was a sticking brake. Thanks for your input.
    Regards
    Roy
    RE: [EXTERNAL] Contact us

    23/4/2018 10:28
    serviceuk@invacare.com

    Copy roysmokie@virginmedia.com

    Hello.
    There seems to be some sort of problem, please visit your local dealers for them to assess the fault.
    Regrds.
    Cyril.

    -----Original Message-----
    From: uk@invacare.com [uk@invacare.com]
    Sent: 21 April 2018 12:07
    To: uk@invacare.com
    Subject: [EXTERNAL] Contact us


    field_requests_type => Need support

    field_subject => Wheelchair motor problem

    field_description_contact => I have had an Invacare Mirage Wheelchair for about 4 years and it is really excellent. I cannot walk at all so I use it to go everywhere. I was out and the chair started to judder and slow down and pull to the right then cut out. I felt the motors and the RH one actually gave me a blister while the LH one was only warm. I was in a quiet area with nobody around to help so I waited for it to cool a little and tried again it moved for a short while then started to judder again so I turned it off and searched my backpack in the hope of finding a forgotten water bottle or something to cool it with. I had a bottle of Oilatum skin treatment oil and poured this over the motor slowly and it eventually cooled down and I continued my journey to seek assistance. Arriving at the out of town ASDA I let it cool completely. and tried again. This time it got me home (about 2mls) . Oddly the motor only got warm like the other one. Does this mean it needs lubricating and how do I do that please.
     
    Last edited by a moderator: Apr 24, 2018
  26. Apr 24, 2018 #25
    In the future I suggest keeping something that can cool it on hand at all times in case a similar issue arisis, particularly I would get a coolant designed for cooling motors rather than say a water bottle. But even if that something can cool it effectively I would of course still get it checked after
     
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