Bad bolt/washer or missing nut?


by sgvaibhav
Tags: bolt or washer, missing, toothed lock washer
sgvaibhav
sgvaibhav is offline
#1
Dec31-13, 04:53 PM
P: 68
Hi, I have a top loading panasonic washing machine.

It is an no agitator top loading machine something similar like this type http://www.automaticwasher.info/TD/A...11-03-25-8.jpg.

So now i dont know if i have a damaged bolt, or a missing washer or a missing nut or a damaged washer.

Let me explain the problem.

The spinning motor suddenly loses contact with the screw.
The bolt/screw and the base plate then do not spin, whilst the motor spins inside.

I have added all pictures of my washing machine components.

To summarize the problem, whilst the motor is spinning, the bolt becomes lose during operation and it loses it contact and it does not spin anymore, and i keep tightening it with screw driver every few minutes to fix the problem until it occurs again.

All pictures can be found here.
https://www.dropbox.com/sh/s0b2kpk6a14tux5/m16pxyoeNd

If the problem still remains unclear let me know, i can try to record another video

I wanted to know how can i fix this problem, should i buy a new bolt (bigger??), new nut??, new washer??
Phys.Org News Partner Engineering news on Phys.org
Lifting the brakes on fuel efficiency
PsiKick's batteryless sensors poised for coming 'Internet of things'
Researcher launches successful tech start-up to help the blind
nvn
nvn is offline
#2
Dec31-13, 07:56 PM
Sci Advisor
HW Helper
P: 2,110
sgvaibhav: If you are missing a flat washer, or nut, I cannot determine that from the current pictures.

My current guess is, the splines inside the agitator disk hole might be plastic (?), and might be stripped (damaged). Perhaps a lock washer underneath the bolt head is missing (?). You might try adding a star lock washer (also called a toothed or serrated lock washer) underneath the bolt head. (But ensure the bolt would still be long enough, after adding a lock washer, to provide plenty of thread engagement length, to avoid stripping the tapped hole.)

I hope I am wrong; i.e., I hope the splines inside the agitator disk hole are not plastic. If they are plastic, there probably would be almost nothing you could do to fix the problem, and it would indicate a very poor design. But I am currently doubtful the splines are plastic.

Could you show close-up pictures of what is inside that hole on the bottom side of the agitator disk?

Another reason I guess a star lock washer underneath the bolt head is missing is because, in engineering, there is a general rule that threaded fasteners on any rotating part generally must have a mechanical locking device, not just bolt preload. If we use this rule, it indicates a star lock washer underneath the bolt head might be missing. Was there an occasion where someone could have lost this lock washer?
AlephZero
AlephZero is offline
#3
Dec31-13, 08:27 PM
Engineering
Sci Advisor
HW Helper
Thanks
P: 6,351
Your pictures seem to be all taken from the top. Since gravity usually acts downwards, if anything has "fallen off" it it more likely to be from the bottom than the top.

The motor should be replaceable, since they sometimes burn out. If you remove it, you should be able to figure out why the drive mechanism isn't working properly.

256bits
256bits is offline
#4
Dec31-13, 10:15 PM
P: 1,260

Bad bolt/washer or missing nut?


Closest I can get is perhaps this
http://www.searspartsdirect.com/part...DiagramPageId=
sgvaibhav
sgvaibhav is offline
#5
Jan1-14, 06:33 AM
P: 68
Few years ago, there was some drainage problem, and some unauthorized servicemen had repaired it, who could have been careless with the re-assembly.

Referring to 256bits diagram of Tub assy (http://www.searspartsdirect.com/part...&prst=&shdMod=), I have parts 68, 70, 84, but i am missing on part 69.

Can part 69 be the source of the problem?
nvn
nvn is offline
#6
Jan1-14, 09:38 AM
Sci Advisor
HW Helper
P: 2,110
Quote Quote by sgvaibhav View Post
Can part 69 be the source of the problem?
sgvaibhav: Yes, part 69 missing is the source of the problem. Part 69 is called an external star, toothed, or serrated lock washer, described in post 2. Sometimes the word "lock" is colloquially omitted. There are two categories: external tooth, as shown above, and internal tooth. Part 69 appears to be the external tooth type.

Try to buy the highest quality lock washer you can find. Ensure it exactly matches your bolt size. I.e., if you have an M6 bolt, then you must buy an M6 star or serrated lock washer. It perhaps could be the external or internal tooth type; probably buy both, and see which one seems better.

By the way, the missing lock washer may have, by now, caused some partially stripped splines, as mentioned in post 2, thereby reducing their load capacity. But first, just try adding the missing lock washer, just to see if it works and how long (or if) it lasts. The evidence currently indicates it might not last long. Let us know if you want further explanation.
siaynoq
siaynoq is offline
#7
Jan2-14, 02:22 AM
P: 2
Hi there joined just to help you as I came across this question although I look forward to the site.

Yes you do have a lock washer missing but I am afraid that is the least of your problems,you require a new agitator as yours has stripped the internal splines. Notice how there is a small indent of the 6 splines in the darker grey (metal?) section in your 6th picture and a lot of grey material spread around the inside of that housing?

That material should from a splined sleeve locking the rotor (agitator) to the motor shaft with the screw/washer assy holding (not locking) it in place, instead you are trying to rely on a friction fit which will not work. Yes nvn hit on the issue in his first post but a lock washer will *not* fix your issue but will be required to prevent the screw from coming loose after the part is replaced. I would order parts 68, 69 & 70 giving you a new screw as the head on yours is damaged

BTW there would be little/nothing wrong with the design even *if* it had a plastic rather than metal spline sleeve as there is very little torque applied to the component there are machine that have just that. (Ex-washing machine engineer)
sgvaibhav
sgvaibhav is offline
#8
Jan2-14, 04:18 AM
P: 68
Ok thanks a lot.

Time to head to the panasonic spare parts shop.
nvn
nvn is offline
#9
Jan2-14, 03:34 PM
Sci Advisor
HW Helper
P: 2,110
Quote Quote by siaynoq View Post
Notice how there is a small indent of the 6 splines in the darker grey (metal?) section in your 6th picture and a lot of grey material spread around the inside of that housing? That material should from a splined sleeve ...
siaynoq: If you are talking here about the picture file named "Rear Screw.jpg," those approximately "six" indentations in the black greasy ring are the completely wrong size to be made by the steel shaft splines. Besides, the steel shaft has approximately twelve splines, not six splines. Therefore, I did not understand some of your description yet.

Also, the wet clothes and water have a significant mass moment of inertia. The splined steel shaft in this particular Panasonic washing machine, model NA-F60G2T, is so small, that if the internal splines were plastic, the plastic probably could not withstand the stress. We see in file "Rear Screw.jpg," there probably is a square-ish steel insert mounted into the plastic agitator. And the internal splines inside this steel insert are probably steel. But we cannot see inside the black circular hole in files "Rear Screw.jpg" nor "Rear.jpg," to give proof, because the pictures currently do not show adequate detail of the relevant parts we need to see. I think you could only perhaps get away with plastic internal splines on other designs that have a much larger-diameter splined steel shaft.

We would need better, close-up photographs, showing the relevant parts, for this specific model. And I did not understand why the first link in post 1 shows a different brand and model, instead of showing a picture of sgvaibhav's own washing machine.

Also, sgvaibhav says the agitator still works, until the bolt loosens. Therefore, it indicates the internal splines still exist, and are not totally disintegrated, unlike what your above quote implies. We do not know, however, if the splines are partially stripped, which I touched on in the last paragraph of post 6. See post 6.
siaynoq
siaynoq is offline
#10
Jan2-14, 09:53 PM
P: 2
Hi nvn looking with a different opinion/from that view you may well be right and yes I was talking about 'Rear Screw.jpg' & 'Rear.jpg' more detailed photographs would help, making the grey ? as being possibly a grease soaked seal helping to prevent ingress of dirt/water down the motor shaft there is also a hex shape around the motor shaft it all looks very worn/corroded though

I would still say the internal splines are stripped at least from the views we can see as sgvaibhav tells us it stops rotating every few minutes until he re-tightens the screw leading me to believe he is relying on a friction contact, even if the screw comes loose the rotor would still be engaged with the splines with the weight of the clothes on top it would not/should not lift enough to completely disengage (especially within minutes). I imagine the last 'engineer' left off the locking washer even so the machine has worked for some time (5 years!)

I have just noticed something else of concern, there is distinct circular scoring of the 3 round nylon?? shapes matching the inner circular ring on the underside of the rotor. Is this due to the metal insert in the rotor being damaged/worn or has the motor shaft dropped? Possible motor gearbox housing loose (sounds terrible) that much friction on the rotor could be another reason for the splines stripping if indeed they have, can you lift the motor shaft at all (although maybe a friction fit through its top bearing not enabling you to)

More detailed photographs would help for sure.
nvn
nvn is offline
#11
Jan3-14, 10:54 AM
Sci Advisor
HW Helper
P: 2,110
siaynoq: Good points. That perhaps helps shed a little more light on the issues. Another mystery to me is, how all that black grease could stay inside a washing machine. I thought detergent soap, mixed with moving hot water, would fairly quickly dissolve grease. This implies the grease exists in an air pocket, such that no water touches the grease; and I guess this implies that the greasy black ring is a water-tight and air-tight synthetic rubber seal.

But with the bolt loosening (due to the missing lock washer), I do not understand how the rubber seal did not leak. I think it would leak, thereby eliminating part of the air pocket, up to the plastic fins above the rubber seal. Therefore, it seems this should have washed off most of the grease (?), up to just above the bottom of the plastic radial fins. Instead, we see lots of grease still remaining below this level.

And if the rubber seal was leaking, perhaps water also leaked down the steel shaft, toward the motor, causing corrosion.

I think the three, round, white, teflon or nylon bumps (bumpers), and six outer bumpers, are intended to be bearings, limiting the agitator tilt; therefore, some scoring might be normal.

Anyway, with the motor also being old, worn, and noisy, as I mentioned in the last paragraph of post 6, I would "first, just try adding the missing lock washer, just to see if it works, and [just to see] how long (or if) it lasts."

Adding the missing lock washer is such an easy thing to try first, just to see if it works, and just to see how long it lasts. Therefore, I would not recommend buying a 30 euro agitator before even trying this simple lock washer installation.

sgvaibhav: I would first try an internal lock washer. If it does not work well, I would then try an external lock washer. If it does not work well, then I might buy a new agitator (and parts 68, 69, and 84), but only if I think the washing machine motor has a long life span remaining.


Register to reply

Related Discussions
Missing Matter - Is anything really Missing Cosmology 15
Converting torque applied to a bolt into the linear force exerted by the bolt Mechanical Engineering 8
window washer Introductory Physics Homework 1
Pressure washer Introductory Physics Homework 2
Missing Matter, Missing Energy? Cosmology 8