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Old 19th May 2019, 08:03   #1
HarryM1BYT
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75 Contemporary SE Mk II 2004 Man. Sal. CDTi 135ps, FBH on red diesel, WinCE6 DD

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Default Electric roller door near disaster

Opened the remote control electric roller shutter garage door last Wednesday to get the car out, after getting it out I pressed the open button by mistake. The door opened more (it shouldn't have, the limit ought to have prevented it) and jammed against the roof and motor just kept going.


I switched it off and needing to go out, I left it as it was because the manual crank handle did nothing.


On my return, I left the car out, unjammed the door by teasing it down a bit at a time and it suddenly came crashing down at high speed. Would have been serious if anyone or an animal had been in its path.


It uses a tube motor, inside a tubular barrel to wind the door onto. Once down, the shutter door can be easily disconnected from the barrel and the barrel with the motor inside removed.



The tube motor is quite a clever and intricate design, it includes the motor, limit switches, a three stage planetary gearbox and a slip ring system to transfer power to the motor which has a stator which rotates with the tube.



Opening up the tube motor, I found the cause of the failure - It relies upon a 3/8" shaft for the drive to 'push against', the 3/8" shaft had been turned down to reduce its strength to form a weakness, turned down to around 1/16" diameter. Idea is that the shaft snaps if the motor is overloaded, but I am surprised it has lasted as long as it has, around ten years since I installed the roller door. I think the shaft was much weaker than it ought to have been.



To get it back to normal working as quickly as possible, I ordered a new tube motor on Thursday, delivered and installed yesterday morning. I will repair the shaft of the original one to keep as a spare.



It is an identical door to the Crocodile door advertised on TV by that builder, but I paid a fraction of what Crocodile would likely charge for the same door.



Point is - if that bit of 1/16" diameter shaft snaps, there is absolutely nothing to stop a roller door coming crashing down at high speed and they are heavy.













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