Expensive mistake today. It was -6°C this morning and I went out and pressed the remote to open the roller garage door. Lots of very unpleasant noises as the irresistible force of the door motor met the unmovable object of the frozen garage door (loads of rain here which soaked everything on Monday). The result was four broken plastic pieces which pull or push the door to open or close it. It's being repaired as I write this.
I can't see any way of protecting the door to stop it freezing again in a severe frost. I wondered if wiping it with neat antifreeze might help, but rain would wash it off. Even heating the door from the inside with a fan heater is of no use as the aluminium slats of the door are insulated to help stop frost getting in the garage.
Anyone come across this issue before, and found a way round it?
There is usually a sacrificial plastic link between the motor and the door mechanism that should fail before anything else more expensive does. It presupposes you have another way into your garage.
Wait until the sun warms it up works for me. WD40 in the lock too. I've had the lock fill with water and freeze before now.
Proper design would have included either a shear bolt (cheap solution) or a slip clutch (expensive solution), or if it is a DC motor doing the work a software version of a shear bolt that measures stall current, which is how my Swish Autoglide curtain track motors know when the curtains are fully open/closed.
How about some form of current limiting circuit or a motor stall detector, Slipping clutch, sounds like a design flaw to me or is it meant for use in hot countries?
My ancient (20 years or so) old Chamberlain motorised doors have exactly this. There's a 'force' setting that is set so that it's just enough to close the door when the mechanism is free but stops trying if it's any harder. It's sensitive enough to stop a bit early when the door needs lubricating.
I always thought there was an overload protection device on the motor, but if there was one it didn't work! Or perhaps I'm mixing it up with the limit switches which stop the door opening and closing too far. Those motors are incredibly powerful. I had the old motor replaced just over three years ago, and decided to dismantle it. It was a tubular motor rated at 282W, and the torque developed was 50Nm. I don't know what the original speed of the motor was, but it ended up at 12rpm through the most complex compound planetary gear I have ever seen. Some photos here: Tubular motor
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Disassembled motor
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Disassembled compound planetary gear
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The complete motor was about 500mm long.
Good point about the spray de-icer. I'll consider it next time the door is iced up. It's the garage door. Some things like a mower, power washer, drills, etc stored inside the garage and viewable from the road, so it can't be left open.
Mine has plastic links, but when my roller door jammed, it broke the motor shaft itself. The shaft had a deliberate weakness machined into it, with no way to repair it, if it snapped.
I could have fabricated something to repair it, but opted for a new motor, which wasn't that expensive.
There is overload protection, a deliberate weakening in the motor shaft, so it snaps on overload.
That was identical to my motor/gearbox, where the drive shaft snapped.
Yes, the gearbox is rather clever, and the limit switch system is remarkably accurate once set. Mine has the limits, plus the control also includes a setting to limit how long the motor can run for.
I think they actually call them butane gas space heaters. I recall standing in the outlet stream of one of those in a barn on an icy day to warm up. About 2 metres away was close enough and the stream was then wide enough to share with a handful of others.
I would check to see if your motor has any torque adjustments. My new Garador 9 motor has two small adjustable potentiometers to limit maximum opening and closing force.
Yes, I remember putting a shoebox under the door to test it. The shoebox stopped the door and wasn't damaged. A bit surprising these other doors don't have similar.
Apart from the motor replacement 3 years ago, the roller door has been fine for 10 years. At the start of December with the really cold weather there was some noise on opening on one day, but it opened and closed without problem or noise for the next month. The December weather was cold but dry - unlike Monday's weather. So it might just be the freak weather of very wet followed by a severe frost which was responsible. It looks like the rain ran down the door, penetrating between the slats and freezing. There was also a lot of ice at the bottom. I assume the rain pooled there and froze; the ice effectively locked the door to the garage floor.
It was repaired yesterday, but as it was again -6°C here last night I'm not going to be trying to open it until it's fully thawed!
To answer some of the other points...
There is no lock; the mechanism prevents the door being opened by hand from the outside.
I'm sure there is no sacrificial link or designed weak point. Perhaps there would be in a more expensive door. That, in any case, would have to be within the tubular motor assembly. A new motor would cost as much as, if not more, than the broken plastic linkage.
There is no touch sensor along the bottom of the door, just a light and photocell across the gap to detect if anyone was there as the door closed. In any case, a touch sensor would be designed to work on closing, not opening, and it was that which was responsible for the damage.
I'll have a look sometime to see if there is any adjustment on the circuit board to detect the motor current, and set it for an overload. I doubt it, as I think on previous occasions when looking there is only a relay to open/close/stop the door depending on the door position or photocell input. I guess it should be possible to put an overload circuit in the mains lead from the circuit board to the motor; I'll have to do some research. Looking at the motor label, there is a category "S2
4min" which is the Short Time Duty Cycle. However, the motor didn't stall - it's torque was enough to break the plastic couplings.
In the meantime, I'll be the "frost 'stat" by checking the door's temperature and condition before I try to open it!
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