Oil leakage from the gearbox axis

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Re: Oil leakage from the gearbox axis

Postby Burgerman » 19 Dec 2018, 01:27

I think, apart from the time-factor, there is no difficulty. We do about the same with PL8. Or not?

Theres no battery tester, even MKs own one, at anything under 1000s of dollars that can test batteries anywhere near as accurately as the PL8 and some other hobby chargers. But again, once you have the data, its still all about how you interpret it or decide what to do.

Old motors?
Scrap metal.
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Re: Oil leakage from the gearbox axis

Postby Fedor » 09 May 2019, 13:24

Greetings again.
After there was an oil leak, the motor began to work too loudly. I think he lost too much grease. Perhaps a problem with the bearing. I want to completely disassemble the gearbox and fix it. I have never done this, so here is my plan and I will need your help.

1. Remove the motor

2. Unscrew the brake so that it does not block the gearbox. Or is it optional?

3. Open the gearbox. I hope there will not be anaerobic thread locks or something like that?

4. Remove all old grease and clean gears. QUESTION. Using what to remove the grease? Gasoline? Ethanol? Something else?

5. View the condition of the bearing and also lubricate or replace it.

6. Lubricate the entire gearbox. I chose Liqui Moly "Thermoflex Spezialfett"

7. Assemble the gearbox

8. Connect the brake

That is my plan. Maybe I forgot something else? The main issue with cleaning old grease. As far as I know, the gear wheel has plastic in its base and I am afraid that it can be spoiled with gasoline or something.

Thank you so much for any help! Really.
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Re: Oil leakage from the gearbox axis

Postby Burgerman » 09 May 2019, 14:01

Paint brush, and kerosine, or even diesel. But why is it dirty?
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Re: Oil leakage from the gearbox axis

Postby Fedor » 09 May 2019, 15:02

Burgerman wrote:Paint brush, and kerosine, or even diesel. But why is it dirty?


Not dirty. But the old grease is better to remove from all details? I want to completely rebuild the gearbox as much as possible.

Sorry for the mistake. By “clean” I meant from old grease.
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Re: Oil leakage from the gearbox axis

Postby Mechniki » 10 May 2019, 23:31

"Gunk" engine de-greaser or brake cleaner, or a steam cleaner will will work
https://www.halfords.com/motoring/engin ... er-1-litre

Gunk then steam clean, WD 40, GT 85 etc, hair dryer (not hot air gun) no more than 1200W to help quick drying
Brake cleaner is very quick to evaporate
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Re: Oil leakage from the gearbox axis

Postby ex-Gooserider » 14 May 2019, 01:19

Checking the overall condition of the motor, especially the brushes and motor bearings should be on the list.....

Also I would suggest what a mechanic I knew referred to as the 'flotation test' for any replaceable parts like bearings - Throw it in a bucket of water - if it sinks replace it...

Sometimes also known as the 'Vision Test' - if it takes longer than 30-60 minutes to SEE the part, then it's worth replacing...

His reasoning was that the parts are generally reasonably cheap, and far better to replace them w/ new than to have to go back in and do the job a second time after the 'acceptable' part fails...

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Re: Oil leakage from the gearbox axis

Postby Burgerman » 14 May 2019, 09:16

Also I would suggest what a mechanic I knew referred to as the 'flotation test' for any replaceable parts like bearings - Throw it in a bucket of water - if it sinks replace it...


Best not test all your new parts. Might work out expensive after half a dozen times...
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Re: Oil leakage from the gearbox axis

Postby Fedor » 20 May 2019, 21:01

With some difficulties, but the motor was removed and disassembled. To my surprise, the gearbox inside was not like the ones I saw here or on the Internet. Gears all made of metal. Inside was black oil, somewhere liquid, somewhere thick. It looked like shit. After cleaning the gearbox looks like this:
photo_2019-05-20 22.02.42.jpeg

Unfortunately, I did not know which bearings I would see, so I took all the dimensions to replace them another time. Replacing the seal was simple, not counting the wheel hub, which had to be removed with effort.

After all, filling the gearbox with grease, replacing the seal, and assembling all it, a problem arose that I could not solve. These are brakes!
Снимок экрана 2019-05-20 в 22.44.44.jpg

On Ottobock B500 they work with a cable that goes into the brakes of the motors and move a special plate in the brake for free-wheel mode. Despite the fact that the cable pulls the plate as much as possible, the free-wheel of the motor is VERY tight. At the same time, in the standard electric mode, the assembled motor at first glance works normally and synchronously. Repeated adjustment of cables has not helped yet. Even if manually move the plate, the wheel moves extremely hard. I have no idea why this happened, and how to fix it.

What can keep the gear in the free-wheel? It moves, but very hard. Why? I have not found anywhere information about this type of motor and this type of brakes. As always, I hope for your help. Thanks!
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Re: Oil leakage from the gearbox axis

Postby woodygb » 20 May 2019, 21:58

the free-wheel of the motor is VERY tight
...The free-wheel of the motor AND GEARBOX is VERY tight.

This is because your trying to back drive the worm and wheel.

As a rule of thumb is the worm will not back drive if the ratio is 50:1 or higher ...wheelchair gearing is.... as I recall... somewhere around 25:1.
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Re: Oil leakage from the gearbox axis

Postby Fedor » 20 May 2019, 23:10

Thank you, Woody. But I understand that it is tight. The question is why the motor touched has become tighter than the other (untouched). The difference is very big! Something obviously happened, or I don’t understand how to adjust the brake cable, because its maximum tension does not work.
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Re: Oil leakage from the gearbox axis

Postby ex-Gooserider » 21 May 2019, 01:35

Remember that what happens with the brakes on most chairs is that you have a solenoid that releases the brake when you put power to the motor...

If you have a power supply, you should be able to put power on the brake to release it - and see how much effort it takes to turn the motor....

The function of the cable is to make the brake do the SAME THING to release when you pull the cable by flipping the lever into free wheel as it does when you apply power... It seems possible that if you over-tighten it, then you might be binding.....

Other things to consider
- new thick grease is going to take more effort to move than old worn out thin grease... (though this shouldn't be a big difference)
- When running motors on the bench they are basically under no load so will spin easily, even if there are bad bearings or other wear issues (and the new grease will tend to hide problems as well) but when backdriving them by hand, you are putting a pretty significant amount of load on all the bits that touch, which will cause any bad bearing or gear wear issues to be much more visible...

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Re: Oil leakage from the gearbox axis

Postby Burgerman » 21 May 2019, 08:28

Gears all made of metal. Inside was black oil, somewhere liquid, somewhere thick. It looked like shit.


All grease is made from oils. With a thickener added - usually a lithium soap. So much of all grease is called a lithium grease.
In time, with use, they seperate. You end up with some thicker grease in some parts that never touch any moving parts pushed to the edges that now does nothing, and an oil thats thinner that is loose and free to move around that has escaped... Many think that theres oil in the gearbox because of this.

The grease that you found when you opened the gearbox was black in this case because it also has molybneum disulphide added to the grease.
https://www.ebay.co.uk/bhp/molybdenum-grease
That had done the usual seperation thing over time. It would be 'tighter' to push with your new grease as this has not seperated out into oil/solids. Thats quite normal. Once refitted, the chair will push as you remember it.

Is molybdnium disulphide grease a better choice? I dont think so. Much of the claims about this grease is from the past, and it does not seem to add anything in the vast majority of testing. Its more marketing than function if you ask me. A bit like the commonly sold magnetic water softeners. Its all snake oil but accepted by many as a real thing. If it does anything much then the difference is so small its hard to measure. So I would just use common old lithium grease.

In fact I do...
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Re: Oil leakage from the gearbox axis

Postby Fedor » 21 May 2019, 09:37

The problem is that the motor is blocked by default with a solinoid. And I could not completely remove the solinoid. I was surprised that the design of solinoid on the AMT motor is different from what I saw earlier. For example, there is no switch, there is a plate that pulls the axis, freeing the motor. And you need a lot of effort to pull it manually! At the same time, it presses a micro switch that helps the controller determine the status. Moreover, as soon as I tried to unscrew the solinoid, the wire that went to the microswitch fell off! I think he could fall off from shaking on the road. Soldered back.

In the gearbox, I added a lot of grease, but it couldn’t affect the free-wheeling mode so much. It became very tight compared to the other old motor. It is now impossible to use the wheelchair in the free mode, but I need it!

Now I will try to adjust the cable. There are suspicions that he must pull the plate not to the end, but to a certain position. And check if the micro switch is pressed correctly. Idiotic system, I think. But I will try.
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Re: Oil leakage from the gearbox axis

Postby Burgerman » 21 May 2019, 10:26

The problem is that the motor is blocked by default with a solinoid. And I could not completely remove the solinoid. I was surprised that the design of solinoid on the AMT motor is different from what I saw earlier. For example, there is no switch, there is a plate that pulls the axis, freeing the motor. And you need a lot of effort to pull it manually! At the same time, it presses a micro switch that helps the controller determine the status.


Thats how most work.
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Re: Oil leakage from the gearbox axis

Postby Fedor » 21 May 2019, 12:21

I thought most of them looked like that.
3035F54F-07B6-473E-AA1C-48B302A841F0.jpeg

My - otherwise.

Brake testing has shown that the problem is not in it. Probably. It works as it should, but in the free-wheel mode, something pulls the gearbox.

There is a suspicion of a small bearing that does not stand up well and rubs against the gear. I will continue to try.
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Re: Oil leakage from the gearbox axis

Postby Fedor » 22 May 2019, 18:34

What type of bearing is best for gearbox? ZZ, 2Z, 2RSH, 2RS, or doesn't matter? I will try to replace each, 4 for each gearbox.
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Re: Oil leakage from the gearbox axis

Postby Burgerman » 23 May 2019, 07:46

Where there is no grease 2RS.
Where grease can escape, 2RS...
Where there is grease, inside gearbox just plain bearing with no sheild, no rubber seal.

Inside motor, 2RS.

ZZ are suposed to be used only where high speed keeps too much oil out to prevent skidding. So they can run in oil mist. So should not be in wheelchair motor.
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Re: Oil leakage from the gearbox axis

Postby ex-Gooserider » 28 May 2019, 03:23

Fedor wrote:I thought most of them looked like that.
3035F54F-07B6-473E-AA1C-48B302A841F0.jpeg

My - otherwise.

Brake testing has shown that the problem is not in it. Probably. It works as it should, but in the free-wheel mode, something pulls the gearbox.

There is a suspicion of a small bearing that does not stand up well and rubs against the gear. I will continue to try.


The picture is fairly standard for brakes that do free-wheel mode by defeating the solenoid parking brake - The lever on top cams the brake internal parts apart so that it releases - just like the solenoid would in normal operation.... The levers come in many different styles depending on the sort of linkage used to work them...

I would expect that your brake is just using a cable to pull on the equivalent lever.

That the brake releases when you give it power says the solenoid is working, and that most of the brake internals are OK. It does NOT mean that the lever part is working / adjusted properly.....

SOME chairs have a different system where there is a lever on the GEARBOX not on the brake, on these, the brake never gets released other than by the solenoid operation. Instead the lever moves one of the gears in the gearbox so that it no longer meshes, disconnecting the output shaft from the motor... These can sometimes be a little tricky to work as the gears won't want to disengage under load, and won't want to engage unless they are properly lined up - slightly rolling the chair back and forth a bit usually solves either problem....
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Re: Oil leakage from the gearbox axis

Postby Fedor » 30 May 2019, 21:47

ex-Gooserider, thanks for the information! My version of solinoid is similar to this one:
MotorKITrs.jpg

Unfortunately, I did not make my own photo. When I unscrewed the brake, the black plate with the square inside (on the photo: in the package, above) was in the motor part. So I could not get it. I correctly understand that solinoid pulls it towards itself and releases the motor axis? I don’t really understand how it works when there is no electricity and I move the lever with my hand. How does she pull this black plate?

Now I have bearings. Thanks BM for help. And I will change them soon. I have a question, if I use a sufficiently thick grease (I wrote which one above), then how much to fill the bearing with it? I read that at 50%, or not?
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Re: Oil leakage from the gearbox axis

Postby Burgerman » 30 May 2019, 22:31

1/3rd to 1/2 seems about right.
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Re: Oil leakage from the gearbox axis

Postby Fedor » 03 Jun 2019, 21:04

Long story ... Long.
Since I didn’t have a backup powerchair at that time, the gearbox was assembled back and I waited until I received the bearings. Now it was the turn to completely rebuild the gearbox. I thought so...

Disassembling the gearbox for the first time I saw the two bearings on the gears and decided that on the other side are the same. And that's all I need.

That was a mistake. Having knocked out the first large gear (with the axle), on the other side there appeared a bearing of larger diameter. Furtherm it turned out that it was impossible to pull out the second axis with the gear without removing the worm. But you can pull out the worm only if you unscrew the gearbox from the motor:

Image

Unscrewing it with great effort - it was not fixed, but there was a small hexagon. And there were only two such bolts on both sides:

Image

It is curious that on the motor itself there are eight holes (only two are used):

Image

The worm was free! On it was another oil seal and bearing. Removing the worm, the gearbox was completely disassembled. While I was waiting for additional bearings and oil seal, I decided to unscrew the second gearbox.

And here there was a big problem. The bolts holding the gearbox have a strength class of 10.9, and they have a small hex. In this case, it is difficult to use the powerful tool, as the gearbox cover is in the way. I was lucky with the first motor, but no luck with the second. In short, the hex on the cap was torn off. And now need to figure out how to unscrew this bolt (second photo above, but another side).

There are a few ideas on how to unscrew it:
1. Drive the torx key into it and unscrew it. This is dangerous, I think.
2. Drill out a bolt with a long bit - more than 170 mm. because it prevents the closed part of the gearbox. There is a risk not to pull it out completely.
3. Take a metal plate, drill a hole the size of a bolt in it, and weld the plate to the bolt. Unscrew the plate with the bolt.

Six openings threaded on the motor make it possible to screw an additional bolt. But in any case, after the gearbox is unscrewed. Any idea how to do this?

The adventure will continue...
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Re: Oil leakage from the gearbox axis

Postby ex-Gooserider » 04 Jun 2019, 00:41

The typical brake design is that the motor will have a stub shaft sticking out on the side opposite the gear box. The solenoid housing mounts on the end cap of the motor. There will be a 'drive piece' that fastens onto the stub shaft - most of the ones I've seen are hexagonal like a nut, but some are square... The drive pieces I've seen fasten to the stub shaft with very small Allen screws. The drive piece will fit into a recess in the brake pad or disk so that it spins when the motor does...

In the solenoid is a piece that slides in and out a tiny amount, and clamps the brake disk between it and a second fixed plate. Usually the brake disk is more or less sealed inside the solenoid 'can, with one end being the fixed plate and the moving bit inside. However in the picture you posted it looks like it MIGHT be the brown circular bit with the square hole in it.

The solenoid is spring loaded so that when there is no power it clamps down on the brake disk which keeps it from turning, and in turn that holds the driven piece and the motor.... When power is applied, the solenoid sucks the clamping piece in so there is enough space that the brake disk can spin. If working right, the lever pulls the moving piece in the same way the solenoid would...

In terms of the motor rebuild - based on the photo I would try either the welding a piece onto the bolt, or drilling with a short drill to get it clear of the end cap and then removing the bolt stub after pulling the motor apart to get at it....

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Re: Oil leakage from the gearbox axis

Postby Mechniki » 06 Jun 2019, 19:05

ex-Gooserider wrote:
In terms of the motor rebuild - based on the photo I would try either the welding a piece onto the bolt, or drilling with a short drill to get it clear of the end cap and then removing the bolt stub after pulling the motor apart to get at it....

ex-Gooserider


Did you try to use an impact screwdriver? I once got a mate to weld a wrench into the head of the bolt/set screw if I have received a damaged item from ebay. AMS
Black Country Mobility etc

If I have ZZ (metal shield) bearings I replace with RS (rubber shield) - I try to get food grade bearings. I just started using rubber grommets on bearing spacers as it makes assembling the caster easier
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Re: Oil leakage from the gearbox axis

Postby Fedor » 10 Jun 2019, 17:36

Well. Thanks for the advice. The torx key was driven into the bolt and it was easily torn off.

But these this gearbox is made strange. I'll try to explain.

Image

As I have already shown, it has two axes. On the first axis is a large gear, on the second axis is a small and middle gear. There are no problems with the first axis and with the worm - each of them are blocked by a lock ring. But, the second axis is made differently. In the gearbox cover, it abut on a small spring. From the other end it abut on a round plastic cap which is twisted on the thread.

Image

So, this axis can be adjusted. But, in one position, she rubs against the worm too much. In another position, with its bearing, it hits the big gear. When I first saw a disassembled gearbox, on a small bearing there was a trace of gear. I was surprised.

When I wrote that the freewheel mode became too tight, it turned out that after the assembly, this axis had shifted and began to touch the worm with its upper part.

At the same time, if after assembly knock on the axis through this round hole on the gearbox, you can fix it. Or make it worse, because the spring at the other end is too weak. And you have to disassemble the gearbox again.

Can someone explain to me WHY the manufacturer did not make the lock ring (like the other axis) under this plastic cap? This would simplify the assembly of the gearbox many times and make the design more reliable. Or am I wrong?
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Re: Oil leakage from the gearbox axis

Postby Burgerman » 10 Jun 2019, 18:31

It may be to allow adjustment for backlash, or different ration gears.
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Re: Oil leakage from the gearbox axis

Postby Fedor » 10 Jun 2019, 19:22

Have you ever seen a similar hole for adjustment from the outside on other gearboxes? I did not even immediately realize that the cap is unscrewed.
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Re: Oil leakage from the gearbox axis

Postby Burgerman » 10 Jun 2019, 19:45

No.
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Re: Oil leakage from the gearbox axis

Postby Fedor » 14 Jun 2019, 14:16

The manufacturer confirmed that it is necessary for some adjustment. They do it on the assembly line with the help of some equipment. Perhaps something like balancing the axis and testing the gearbox on the stand. I do not know for sure.

Anyway, with the help of my best brother in the world, we replaced all 5 bearings and 2 oil seals in each gearbox. However, at the assembly stage, due to the above described feature, it is not yet possible to assemble the gearbox without extraneous noise while driving.

As far as I understand now, its most unusual and rare gearbox of all that are used in powerchairs now. Some people who had experience with powerchair motors confirmed that this type of gearbox is very difficult to assemble correctly. I can only agree. It is curious that the entire product line of AMT Schmid motors made with a similar principle. And these motors go on all Ottobock powerchairs, including the new ones.

In general, if someone rebuild and assembly specifically such a gearbox on practice (AMT Schmid SRG05, 4-pole, 350w, Ottobock B500-B600-Juve). Advice would be very helpful.
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