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Post by jazzorek on Jan 17, 2014 6:12:23 GMT -7
Hi,
Does anyone knows what kind of oil is in C-Leg hydraulic cylinder (model 98-1)? The oil just leaked from my C-Leg and the Otto Bock service asked for repair much more than I can afford. I must fill it on my own. Can anyone help me?
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Post by snarfler on Jan 17, 2014 20:44:49 GMT -7
Jazzorek,
I can only help you by offering you my advise as an Engineer. Don't try to fix it yourself. Even your Prosthetist is probably not qualified to make the repair. If you have lost any oil at all, it is because a seal has been compromised. Adding fluid will only run out and could result in a catastrophic failure. The unit will probably need to be sent back to OB and the seal replaced. Such piston technology has been around for more than 150 years. The viscosity of the oil is determined by the pressure retention necessary to the application. Anything from Lighter Fluid to almost chewable 900w Gear oil. So please, refer all repairs to a qualified service Technician. I wish I could do more.
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Post by jazzorek on Feb 1, 2014 6:57:50 GMT -7
Thank you snarfler for reply. The leak is blocked, it was the issue of broken seal. The qualified Otto Bock service in Poland asked for repair almost three-quarters of price of a new knee! It makes no sense to repair it in Otto Bock service. That's why I'm looking for some other solutions.
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Post by tedatrowercpo on Jul 11, 2014 10:42:01 GMT -7
If you try to repair it yourself you are in for a big surprise. Special tooling is required for this job. The contents of the unit are compressed by a large and powerful spring. The usual result when someone opens one of these units at home is that all the internal parts go flying across the room, along with the remaining portion of the hydraulic fluid.
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Post by mojaprotezapl on Jul 26, 2016 9:11:42 GMT -7
Hi, Does anyone knows what kind of oil is in C-Leg hydraulic cylinder (model 98-1)? The oil just leaked from my C-Leg and the Otto Bock service asked for repair much more than I can afford. I must fill it on my own. Can anyone help me? Hey, I repair C-Leg, I have the right tools and knowledge. If you want I can fix your knee - cheaper than Otto Bock. Contact me: tomasz(at) mojaproteza.pl |
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Post by djview on Nov 30, 2016 11:55:15 GMT -7
The hydraulic oil is a (clear) synthetic in order to withstand extreme heat & cold and remain stable. I suspect it may be similar to the hydraulic oil used in aircraft landing gear. There are no seals in the C-leg. The valve parts are manufactured to only 3 microns clearance preventing the oil from seeping past. The valve body has become distorted probably due to extreme heat caused by prolonged stance control engagement such as descending a long hill. In the service center, the oil is filled and placed under a vacuum to remove the bubbles. Even if you re-fill the unit, it will continue to seep out. Otto Bock, under the ownership of Hans Georg Nader, has designed their repair policy and repair cost to sell new units.
A simple test to determine if a C-leg is leaking is to run your finger along the piston shaft and smell for oil. If you detect hydraulic oil smell the unit is on its way out and requires servicing. As well the unit will make a gurgling sound (Air) when you flex (Bend) then extend the knee. The average C-Leg repair is about 5000.00
When purchasing a used C-Leg online, diligence must be exercised to ensure you are purchasing a fully functional unit. Otherwise, due to high repair costs, you are purchasing an expensive paper weight.
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Post by djview on Nov 30, 2016 12:19:28 GMT -7
P.S There are no seals to replace and unlike a strut on a car there is no powerful spring. The hydraulic unit operates by a servo motor controlled valve assembly that opens and closes, porting oil through fine channels. The unit receives the signal to open and close from a sensor in the knee hub which constantly measures the knee angle. Essentially, the sensor sends a signal through the microprocessor to the servo motor which opens and closes the valve port to maintain a preset knee angle. Walk fast, it increases the hydraulic oil resistance; walk slow, it decreases the resistance maintaining a constant knee angle. The strain guage sensor in the pylon determines if you are applying 70% toe load and when coupled with the knee in full extension, releases the hydraulic knee resistance allowing the knee to swing during the swing phase of the gait cycle. Otherwise, the knee defaults into stance offering resistance when descending stairs, sitting, or when inadvertently stepping into a depression. Otto Bock has special tooling to remove the knee axis making if very difficult to change the housing.
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Post by djview on Feb 4, 2017 18:52:23 GMT -7
I found some aircraft hydraulic fluid however it is an amber colour, not clear. I found some hydraulic jack oil at Canadian Tire which is good in low temperatures and is clear. I tried filling the hydraulic from the top but it doesn't seem to enter the ports and valve assembly. I might take the servo motor assembly off the bottom of the valve assembly then remove the valve assemly plate thus exposing the 4 oil ports. I will then submerge the hydraulic unit and value assembly in a container of hydraulic fluid allowing the trapped air to bubble out of the two parts. I will also cycle the hydraulic while the valves are in their open position to siphon the fluid into the ports. Once all air has escaped I will then assemble while submerged. I will assemble the rest of the knee then take it to a c-leg certified prosthetist to zero set and activate the knee. I'll post the results good or bad.
I also researched an additive used in hydraulic systems which treats seals and stops leaks. This may help limit fluid escaping past the O-ring on the piston shaft.
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Post by djview on Feb 6, 2017 23:51:22 GMT -7
The hydraulic low temp jack oil purchased at Canadian Tire worked. I refurbished three knees. I also discovered that after re- assembly, if you disconnect, then reconnect the battery, it resets the computer. It takes some perseverance and patience to purge all the air from the system. As well, reassembly is a bit tricky. It helps to tape each connection ribbon to the housing after plugging them in.
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Post by lizz8129 on Feb 17, 2017 19:04:25 GMT -7
Please don't try to fix this youreview self! I am a technician for Ottobock and do hydraulic services daily. There is much more to it than just putting in more hydraulic fluid. Each hydraulic cylinder goes into it airtight chamber so that we can remove all air from the unit. Seals are replaced, piston is checked and as well as all the other components. If you try to do these services on your own it can result in a catastrophic fall, which unfortunately is not going to be covered. I know that the service is kind of expensive, but it is worth it because you're getting the best
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Post by dentarg on Apr 2, 2017 7:57:18 GMT -7
my c-leg leaked oil after I finished painting my fence I was bending down a lot and when I went to walk I could feel the oil slowly leaking out “warning c-leg doesn't like to be fully compressed”... it’s a 2009 model so no warranty.. took it back to the prosthetist they sent it back to Otto bock, and Otto bock to my surprised quoted $20,000 WITH NO WARANTY… that is crap, who would quote $20,000 and not back it up with a warranty… “quality for life” my ass Otto Bock”… so this what I did, I told Otto bock to stick it… got a second hand c-leg for $300 and took out the hydraulic unit out and swapped it.. took it back to a prosthetist to get it programmed and it works perfectly… I am so glad to find this form, I didn’t think it was possible to replace the oil and to find people who can do it… thanks guys….
Oh p.s lizz8129 “I know that the service is kind of expensive, but it is worth it because you're getting the best”…. I just laughed at your statement “kind of expensive”, “The best” my ass then why don’t you offer a warranty on a second hand service I mean come on your only putting in new oil.
I don’t think you’re an amputee mate?
Try to imagine that you buy a brand new BMW with 5 years’ warranty and your car has served you well, but sadly after 5 years you need a new engine (or in are cases a new oil change). You love your car and BMW will put in a new engine hmm let’s say for $20,000 (Otto bock prices example), I don’t think a whole new BMW engine would cost that much but let’s use it for an example… do you think BMW Being a major German company if they quoted you $20,000 do you think they would give you a warranty on a brand new engine or a repair?
I will let you think about that…. While I try and figure out how to get the maximum “quality for life” out of my c-leg by figuring out how to service my own leg and helping others do the same… c-leg is amazing knee, not because it’s the best it’s because its low tech and that we the people can get the true “quality for life” out of your products by servicing them are self but prolonging the life out of the c-leg by knee is good as gold and I fixed it for $300… Im sure you will fix that problem in the future knees but you know what Im very happy with the c-leg its simple but it has everything I need..
You know the services are ridiculously high! But you have a job and no doubt you have a family to feed but I believe somewhere in the back of your head or in your heart you know that is just plain greed on Otto Bock behave… by forcing people to buy new c-legs when all you have to do is service them at a REASONABLE price then people would not have to take risks when it comes to their NEEDS… but then again it’s kinda fun figuring out it for are selves, so thanks Otto Bock for making a product that is truly a “ quality for life” product like the c-leg…
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Post by vinicius89 on Dec 25, 2020 8:12:43 GMT -7
Hi,
Sorry for reactivating an old post.
I would like to know if you could share more information about the hydraulic repair of the cleg.
What better oil? (if they can recommend the specifications)
Can any additives be used?
Any tips for removing all air from the hydraulic system?
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Post by cristiano on Mar 31, 2021 22:24:48 GMT -7
Hello my name is cris and i can help who need repair c leg.
I repaired c leg at 7 years .
Just contact me in chrisorthopro@gmail.com
Best regard
Cris
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Post by mojaprotezapl on Oct 4, 2023 1:48:01 GMT -7
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