Ottobock B500 Motor Alternative

[Fedor]

Greetings!
I recently had experience repairing the AMT motor gearbox. They are often used in Ottobock powerchairs. As my experience has shown, these are not the best motors - especially the gearbox design. It is quite difficult to assemble it correctly and it takes a lot of time.

I would like to have another pair of new 4-pole motors (or used in good condition), but with a different design. On my Ottobock B500, the rectangular gearbox of the motor is attached to the frame with four bolts.

What motor do you think (non-AMT) can approach such a frame? In some photos of other B500 I see other motors, but in the official parts documentation there is no information about other motors. Only AMT.

Here is a photo of AMT motor (4-pole, 350w, 10 km/h):



If someone uses a B500 with a 4-pole motor, please tell me, do you have the same motor? If the other, which model?

Do you think it is possible to find an alternative to this motor and use it?

[Fedor]

Another reason to find an alternative to this motor: they are very rarely found on eBay (I have never seen a 4-pole version of the AMT motor on the market). Only purchase from an authorized dealer - $ 700 per motor.

[Burgerman]

They are a manufacturer. If you need a specific motor, gearbox, output shaft length/diaeter tapered or straight, windings, cables and connectors as a package. Then they will give you a quotation in batches of say 100 or greater. They are not set up to sell single otors to retail customers.

So you need to go to a dealer. They are not common, as most chairs are cheaply made, use 2 pole motors. But buying someone elses used up motors is pointless. The only sensible option is new. I know you are going to say they are too expensive but sadly this is the price.

I could sell you any number of my USED motors. Trust me you dont want them!

These are all 1 year old or less from my chairs.

[Fedor]

It's not just because of the price. I do not want to buy a motor with the same design of the gearbox. Dealer offers a replacement at $ 1,400 for both motors. They will be the same as now. They will work for me for 3-5 years and then the bearings will need to be replace and I do not want to again have a gearbox that is so difficult to maintain. Because those motors that I have been using for 5 years have a problem only with the gearbox, the motors themselves are like new ones.

The fact is that the design of the AMT gearbox is quite rare. Others are much simpler, so I’m looking for an alternative that fits into my frame.

[expresso]

would it be possible to send them out to be rebuild - may cost half the price of new and you dont have to do anything. just install and use again for another 3 to 5 years hopefully before doing it again.

here my motors cost $1000 each - insane - i plan to do the rebuilt route when time comes for new motors now - hopefully cost me half the amount.

its an idea you can explore

[flagman1776]

If the motors are still good... perhaps the gear boxes could be rebuilt. I wonder where the wear is? Might a machinist bore the gear centers for pressed in bushings? What material is the gears made of? Might new gears be 3D printed?

[Burgerman]

Powerchair motors are built to very exacting standards, with low backlash and low noise. Rebuilt motors are generally stripped cleaned and bearings replaced. New brushes. They dont fit new magnets that weaken over time and use and reduce power and efficiency, or replace armatures, rubber cush drives, brush holders, gears, shafts, etc. They may replace the brake. And a coat of paint. They are not the same as buying new.

Repairing gearbox also wont be as good as new, and may have increased noise/backlash. The motor will be less efficient than new due to magnetic feild strength reduction over time. It makes less power and more heat so your range and torque decreases. Because of this it makes sense to buy a new set of motors rather than repair/replace parts. They wear out as a unit. All the motors in that photo still "work". But are noisy, have extra backlash, and show reduced range. So they get thrown on the pile of tired motors. I have tried the rebuild thing, and they are still not as good as new, and the money for bearings, brushes, etc would have been better put towards a new set of motors. In the same way, I wouldnt dream of buying used motors on ebay, as they are only really any good for a year of hard use anyway. Or 2 years of typical daily "normal" use...

[expresso]

well that would be nice to buy new all the time but at those prices - i am going to try the rebuilt route with the spare set i have here - and see how that works out - $1000 compared to $2000 - i take a chance and see - when the time comes - i hope its a few years from now -

[Fedor]

would it be possible to send them out to be rebuild - may cost half the price of new and you dont have to do anything. just install and use again for another 3 to 5 years hopefully before doing it again.

If the motors are still good... perhaps the gear boxes could be rebuilt. I wonder where the wear is? Might a machinist bore the gear centers for pressed in bushings? What material is the gears made of? Might new gears be 3D printed?

The motor itself is in good condition. Even brushes and bearings in motor for 5 years do not need to be replaced! I travel a lot, but not hardcore – load is mainly on the bearings in the gearbox so they definitely need to be replaced. Maybe because of their poor quality.

I disassembled this gearbox many times and every time I could not assemble it correctly and it does not work well enough. The main problem is that in my opinion, AMT motors, which are installed on almost all powerchairs from Ottobock, have an extremely bad gearbox design. Their life they work fine, good power and torque. But when it comes time to replace the bearings in gearbox you may have problems. I.e. by "bad" I mean just spending on rebuild.

Here in Russia there is at least one company that makes such rebuild. What did they say? They said that it was precisely these motors from AMT that often could not be rebuild efficiently - they are almost disposable. It takes a lot of effort, time and money. And I can confirm this.

If I continue to use Ottobock, then after 10 years I will have a bunch of discarded gearboxes and a lot of great fans made from motors. Or something else

Therefore, I thought that it might be better to get experience with other motors if they fit into the B500 frame. But I'm not sure that this is real without changing the powerchairs brand.

here my motors cost $1000 each - insane - i plan to do the rebuilt route when time comes for new motors now - hopefully cost me half the amount.

I understand your situation well. I hope you have better luck and your gearboxes after rebuilds will work better than my.

[expresso]

i see - they make these things not to be repaired really - they just make them to work and break - then replace with new - they dont bother fixing for that reason you say - isnt worth it - more work and time to rebuilt and in that case may cost more than new.

i never had my motors rebuilt before - mines are light also compared to my other 4 pole motor - makes me wonder whats it made of inside -

[wheelie junkie]

My Ottobock Juvo B5 has Linix motors, you might want to see if Linix offer a suitable one for your Ottobock.

From Ottobock spares website it does look similar.

[wheelie junkie]

Although on closer inspection maybe not.

[Burgerman]

But that does not mean those wont fit.
If you do this, i.e. swap to different motors, be aware that you may need to change motor load compensation settings - or be very careful switching on and initial test...

[ex-Gooserider]

Those look at casual glance like F55 motors, I don't know what brand motors were used on those but might be OK...

I have never used their rebuild service, but Eurton at least claims that when they do a rebuild they turn the commutators and replace the cush drives (or at least the rubber bits) and otherwise do a pretty complete overhaul....

I would say that if Linix motors are anything like their actuators I'd consider their stuff to be a downgrade - the Linix actuators I've seen are the cheesiest, flimsiest units I have ever encountered....

ex-Gooserider

[Burgerman]

Clear useful vid. Thats how almost all traditional chair motors / gearboxes work. But most include a rubber cush drive that fails if you are a holligan with sharp programming garanteed. I am OCD, and would have to have removed all old gease with a brush and kerosene before new grease. And new brushes...

[steves1977uk]

Those look at casual glance like F55 motors, I don't know what brand motors were used on those but might be OK...

I have never used their rebuild service, but Eurton at least claims that when they do a rebuild they turn the commutators and replace the cush drives (or at least the rubber bits) and otherwise do a pretty complete overhaul....

I would say that if Linix motors are anything like their actuators I'd consider their stuff to be a downgrade - the Linix actuators I've seen are the cheesiest, flimsiest units I have ever encountered....

ex-Gooserider

Those were EMD motors which are now owned by Parvalux.

Steve

[Fedor]

My Ottobock Juvo B5 has Linix motors, you might want to see if Linix offer a suitable one for your Ottobock.
From Ottobock spares website it does look similar.

Thanks for the information. I am glad that Ottobock does not always use such motors from AMT. I'm not sure that they will fit my frame, but they are very similar, you are right. I will explore this.

I would say that if Linix motors are anything like their actuators I'd consider their stuff to be a downgrade - the Linix actuators I've seen are the cheesiest, flimsiest units I have ever encountered....

That's interesting. Linix is now quite actively used in wheelchairs, as far as I can see. Based on your experience which motors brands do you think are the best for now?

just because its sorta on topic, and you guys might find this interesting.. i'm just now making a video, taking apart a "standard" wheelchair gearbox..

Great video. Thanks. This type of gearbox looks simple and reasonable. I also liked how neutral (freewheel mode) is made - simple and efficient design. In my case, everything is different. Even to just open the AMT gearbox you have to apply a lot of effort because the bearings are pressed right into the cover. After that, one of the axles will most likely move and you will have to adjust it after assembly through a special hole. As a result, even without changing the bearings (as in your case), you will have to do 5x times more work with AMT gearbox, which is not a fact that it will be completed successfully. Therefore, I think about the alternative.

[foghornleghorn]

Apologies if I'm being blind and it has already been said but I've not noticed anyone mention this.

Any different motors and gearboxes you want to use that have different mounting points will probably be able to fix to the chair with an adapter plate. However, be aware they may come with different length/thickness/shape axles so your current hubs/wheels may not fit too. I have no idea how handy you are or whether you would be needing to pay for parts making so be aware you may need to factor this in to any financial based decision.

[Burgerman]

You can frequently get complete used powerchairs for the price of a set of used motors or a refurb. Which is likely a better option. I bought several that were in extremely good condition over the years. Many never get a bid and will accept very little after the auction ends.

[Fedor]

It's true. Even in Russia I can buy a used powerchair as mine in the same configuration. It will cost $ 200-400 more than a set of motors (about $ 1800 for the whole powerchair). But as you said earlier, if you buy only for motors, then this is buying a cat in a bag. Often there is no way to check the motors before buying, even visually. Because it is a different city, delivery, etc...

[Fedor]

While I am waiting for my new motors, I was thinking about what is the reason for the different design of gearboxes for such motors?

Why do some motors have a square gearboxes, like on this (thanks for photo, BM):

However, other motors such as these:

117459-8716883.jpg (8.64 KiB) Viewed 3762 times

All types of motors are 2 or 4 pole. All have 6-8 miles of speed. So what's the difference? Is this just because the frame of the powerchairs may differ? I think there is no problem to make a frame for any motor. Then what explains such differences of motors (and gearboxes) in powerchairs? What do you think?

[Burgerman]

Just easier to mount in different frame types.

[LROBBINS]

Aside from shape, there are some efficiency differences among different gearboxes. The AMT gearbox is bevel and spur gears and is more efficient than using a worm gear (even if harder to fit and align the internals). The Chinese motors that many chairs now have instead of the AMT on their older models are worm gear. The in-line planetary gear motors that Will used on WillChair 1 & 2 were even more efficient, but he then would have lost some with his chain and toothed-belt drives. The one on the WillChair3 is right angle, but also very high efficiency.