andress Posted June 20, 2017 Share Posted June 20, 2017 So we all know KS14C has a bit of a trouble with the axle cracking. The first time it happened to me I went trough half a year long warranty process and apart from the time it cost me 290 USD as apart from the motor itself I needed new board (old one is not compatible with the new motors) and I also wanted new shell and I had to pay the shipping and taxes. I thought that with new type of motor they would have solved the issue but no... after 1400 km according to the app my axle broke again! This is how it looks from outside when your axle breaks: detail after removing the pedals: This time I was so careful! I didn't jump the curbs I had barely any falls... but maybe it was caused by not using the spacers that come between the pedal holders and motor. I didn't use them because the ones from the old motor were not compatible with the new one and I didn't receive new one with the new motor. Tina said to proceed without them but I think that was the reason why the axle broke so soon because maybe I put them a bit further apart or something like that. Anyway I didn't want to pay another hefty sum for a new motor to have it broken in few months again and I actually had a new 500W KS motor on hand since they sent it to me by mistake at first instead of the 800W one. First I tried whether it will work with my board meant for 800W motor. No surprise, it doesn't . But the axle is the same so I decided to gut the never used motor to get mine going again. So I took both motors apart. And this is how i looks: The way the wire are connected to the windings Detail of the axle: Detail of the hall effect sensor: To remove the axle you need access to a hydraulic press. I tried to hammer the axle out but had no success, I only damaged the axle even more. I study a technical university so I just went to the building of mechanical engineering and after few minutes I had time setup when I could come to use the press. In the end the people there just did it for me because of safety concerns. The press ( very old made in now nonexistent country of Czechoslovakia :D) Video of the actual removal: https://goo.gl/photos/nJ5HVcn3ogqr8ECB6 Detached axle: To remove the axle I had to remove the cabling first and of course the cabling got damaged while being pulled trough the axle. The original phase wires were 1,22mm2 with plastic insulation the hall sensor wire were 0,22mm2 also with plastic insulation. The replacement cables I used were 1,5mm2 and 0,25mm2 with silicon insulation. So potentially higher quality but they were also thicker so now sheath to put them all together could fit in the axle so i kept them separate. Also as you can see they didn't have the right colors which caused me some trouble later on when connecting to the control board. I had them labeled but the tags fell while I was pulling the cables through the motor cover So when finishing up there was a lot of experimenting with the right order. I knew which wires were for hall sensors and which for phases from thickness and I knew which wires were the power for the hall sensors because these were the only ones with the correct color. But I still had two groups of 3 wires each. That gives me 36 combinations. Anyone who ever connected the wires wrong knows how crazy the unicycle acts if you do that :/ Luckily it only took me 8 tries! Those were some horrible couple minutes! To pull the cables through the axle I used the same method as @Rehab1 - solder them all together and use single wire to pull the trough. Thanks for inspiration! Unfortunately some of the hall sensors got damaged during the axle removal so I had to change them too. The original sensors were MT4451-A (TO-92 package) as @esaj helped me discover from the markings. I could not get these in Czechia so I used TLE4935L instead as I have already used them once on different unicycle and they worked. Damaged hall effect sensor: And here is finally the finished motor with new wiring and hall sensors: After putting everything together the unicycle works! But there are some problems. It does wobble. When I ride it swings back and forth a little. It it pronounced way more while riding forwards then by riding the unicycle the wrong way with the brake light forward. Anyone has any ideas what could cause this? Here is a video of this https://goo.gl/photos/WfKaDb1iGzgadY1p6 Also the free spin maximum speed is different in each direction it is 40,6 km/h in forward (more wobbly direction) and 38,5 km/h in backwards (more stable direction). So IDK is this some mechanical problem ? the bearing perhaps? I used the motor covers from the 500W as the bearings spin much better. Could this be the cause? They seemed the same otherwise and they fit with no problem. Problem with the board maybe? During the experimenting with the right wire order combinations some nasty thing were most likely happening to the board..:/ I will see how it progresses but please if someone knows what it could be let me know I would hate going trough all this trouble to have the unicycle break down again soon after. So in total this cost me about 20 USD. 10 USD for the beers I bought the people who helped me with the press and 10 USD for the wires and hall sensors. It would cost more if I had to have the axle machined. PS. There will be part two with the older motor from the first time my axle broke and new machined axle for that Link to comment Share on other sites More sharing options...
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