Crocodile type electric roller shutter garage door.

[Harry Bloomfield]

I have the same unit they keep advertising on TV by that builder type bloke, but it is not a Crocodile supplied unit, though the identical electrical/mechanicals.

Today it opened further than it is supposed to do, jammed itself on the roll and the motor kept running and seems to have done itself some internal damage. I managed to release it/unwind it and the door shot down to the fully closed position. Motor makes a noise, when pressing the open button, but the door hardly moves as if something on the drive has stripped.

So I'm looking for some information on the internals of the drive system. The spindle is around 4.5" diameter and includes the motor and obviously must have some sort of concentric gear drive, which I suspect is the issue.

The manual open/close drive crank also does nothing at all, no resistance to turning the manual drive rod at all.

 

[Nozzle]

I would suspect there's probably a sheer pin in the shaft which protects the motor from stalling/gearbox from opening itself should it go past the physical stops. A sheer pin is like a roll pin but is designed to snap beyond a certain torque

Nozzle

 

[Harry Bloomfield]

Thanks, you might well be right, but I will need to disconnect the shaft from the door and unbolt it. From memory its a low voltage motor drive.

 

[Harry Bloomfield]

It uses this, or something very similar to it. Mine has a bare metal out though. https://www.ebay.co.uk/itm/RD50NM-5...m=120511008351&_trksid=p2047675.c100005.m1851

 

[Harry Bloomfield]

I have got the complete roll disconnected from the door and down on the ground, plus tried to get inside the motor. The actual tube motor/ gearbox / limit switch unit is this below..

The unit tube motor fits inside a hex sided steel tube the full width of my door, between the two side brackets. In the video, the first item he pulls out is the section with the limit switches and limit drive system. I pulled that out but it was still tightly attached by its wires to something, so rather than cause damage, I thought to have a go at the far end of the unit. Probably a mistake, because that is the gearbox. 3 sets of 3 planetary gears in succession came out. No sign of any fault or damage yet. Motor sounds as if it runs when powered, but I cannot be sure yet. I have abandoned it for the night, another go tomorrow.

 

[Harry Bloomfield]

I have now got well into the unit and it is a very clever design indeed. The motor actually rotates when it is running inside the casing, with the power taken to it by something similar to 'slip rings' - pairs of brass rings or washers, which act as slip rings. Through the centre of which passes the drive shaft around 3/8" diameter and it seems to be this shaft which has snapped. Complete new unit is £60 - which is where I will end up.

 

[Harry Bloomfield]

New complete motor ordered, but I might repair what I have as a spare unit when I get a roundtuit....

One thing really concerns me about this and that is that if the 'sheer pin' fails, as it is designed to do, then there is absolutely nothing to prevent the door coming barrelling down as happened to me yesterday.

First image is the manual crank and its gearbox on the left, followed by the limit switch section, then 'slip rings' feeding through to the motor and capacitor still in the hidden in the blue tube section. The broken shaft is down the middle, half in the left half on the right through the brass washer 'slip rings'.

Second image shows the two halves of the snapped shaft, which is around 3/8th" diameter yet it appears to have been turned down to around 1/16th of an inch to act as a 'sheer pin'.

Third image is a close-up of the limit switches, top and bottom. Manual gearbox remains stationary and blue tube rotates, driving the limit switch cog system around.

I'm thinking - cut a slot into the end of each shaft, then join them with a bit of thin steel with a drilling through steel and thin steel, to enable a couple of small split pins to be fitted as a spare tube motor. Another way would be a bit of tightly fitting tube, again pinned to each section of the shaft. There is some pull, to pull the two sections of the shaft apart, from springs applying pressure on the slip rings.