More gear than Carnaby Street in the 60s!

[Jeff Layman]

A bit of festive amusement, and perhaps something of interest for the engineers here.

I have a garage with a roller door which is opened and closed by a motor. A month ago it failed to open, and I had to use the manual winder handle to open it. Strangely, it still closed automatically without problem. Some checks showed it wasn't the remote or control box playing up - it was the motor itself. This was a "roller" or "tubular" motor. I'd never heard of these, but it was no trouble to order one on the garage door supplier's website.

When it came it was a really strange beast. On reading the installation instructions I chickened out and got some local pros to do it (it took them about 2 hours), as it delivers 50Nm and I considered that could do some damage if I got it wrong. Anyway, they left me the old one they removed - which they confirmed was faulty - and I decided to dismantle it and see what was inside. I had previously looked on the internet to see if there was an "exploded" diagram of a tubular motor, but I couldn't find one with sufficient detail.

The complete device itself is about 60 x 4.5 cm, with a motor at one end which is fixed to the wall, and a drive shaft at the other which engages with the roller door. What amazed me was the compound planetary gear. I've never seen such a complex arrangement of cogs and pinions! I never saw it in place in the roller door so don't know how it opened it. I can't get my head round exactly how this works; internally the motor gears (which have adjustable microswitches limiting the opening and closing range) turn the orange tube. The extreme right-hand end of the motor drive assembly has four screws which fix it to the orange tube. As the motor itself is fixed by the large rectangular plate at the left-hand end, when the motor turns the orange tube must turn. Note the starter capacitor fits between the motor and the planetary gear end, so there is no toothed drive shaft through from one end to the other. The fixed planetary ring gear photo shows how the orange tube gear must drive the planetary gear. The ring is fixed in place and not removable. However, that ring only goes down 2 or 3 cm. There are then no teeth until a cm or so above the plate where a toothed shaft comes through (this shaft would mesh with the centre of the three epicyclic cogs on the extreme left of the "disassembled compound planetary gear" photo, but where the other end of that shaft goes to I have no idea!). Unfortunately, no matter how I try I can't get that compound assembly fully back in the tube, so can't see how the motor would turn it when opening/closing the roller door. Anyway, somehow the tube rotates and meshes with the extreme right-hand teeth of the compound planetary gear. It's there my reasoning fails. Somehow the drive goes back through all those planet and carrier gears to drive the final sun gear, which itself leads to the flattened shaft at the extreme RH end of the compound planetary gear. That shaft goes through the middle of the "roller door drive mechanism" metal piece at the centre of that photo, which itself somehow joins to the plastic bit on the left (all held on by a circlip), and that somehow opens/shuts the roller door itself. Too many "somehows"! See photos here:

Tubular motor

Disassembled motor

Drive motor and limit switches

Compound planetary gear

Disassembled compound planetary gear

Fixed planetary ring

Roller door drive mechanism

I assume that the inertia of the roller door allows the gearing to work before it is able to move the door, but has anybody seen one of these and can explain exactly how it works?

[Dave W]

More detail please.

On 'Disassembled motor' there is a capacitor; is this what you call a starter capacitor? There are still two wires going into the tube - where to? I found a diagram of another tubular motor in which the actual motor was in the middle of the tube, and only the limit swiches were on the left.

On 'Fixed-planetary-ring', there is a six-toothed socket at the bottom; is there a corresponding 6-toothed gear in the middle of the planetary gears that fits? Is the socket fixed or does it rotate? Perhaps it is on an internal motor shaft.

Is the flattened shaft on the right of the gears fixed to the housing or connected to the planetary gears?

[Jeff Layman]

I'll get back to you after Christmas on these points. You could be right that the motor is in the middle - the wires disappearing inside puzzled me. I had assumed they might be going to some thermal or mechanical overload switch. Unfortunately the middle bit (under the fixed planetary ring) seems to be potted or is otherwise fixed in. I couldn't see how, but I'll have another look. I might also try to connect it all up to the power and see what turns where.

In you first paragraph you mention a diagram of another tubular motor with the motor in the middle. Do you have a URL for that?

[Tim Lamb]

In message [e-mail], Dave W [e-mail]> writes

I have a duff one still fully assembled if anyone wants to play:-)

[Dave W]

I looked at loads of tubular motors, which are apparently only used in roller shutters, but today I found again:

has the motor in the middle, but I don't think all tubular motors are the same.

[harry]

It's probably something to do with the motor reversing mechanism. Single phase motors need to have a separate start winding which has to be reverse connected to reverse the motor. The limit switches on the door will be linked in.

[Jeff Layman]

Actually, there are three wires - see below.

Yes, It is the six-toothed central sun gear spindle on the left-hand side of the "Disassembled compound planetary gear" photo. It had slipped through a bit to the right, but in practice extends past the plastic planet gears into that 6-toothed socket, as well as meshing with the metal planet gears in the middle gear assembly. That socket must be the power drive from the motor.

It is part of the planet gears. It's not easy to see in the "Disassembled compound planetary gear" photo, but the fixed bit is the dull grey round piece with the lugs and screw hole which hold it in place on the orange tube. The shaft passes through that and is one single piece with the shiny round part holding the four planet gears. So if the shaft is turned, the four planet gears rotate. In practice, of course, it's the other way round - the central sun spindle of the middle gear assembly rotates, thus causing the four planet gears to rotate, and so causing the flattened spindle to rotate.

Thanks for that URL - it explains things neatly. My tubular motor is of the same construction; it's a 45M404-50 (

) You are right that the motor is in the middle. What has - and up to a point still does - confuse me is how the reversible AC motor works. I had assumed it was at one end as that's where the lead from the control unit entered. I still haven't completely dismantled that end of the tubular motor (by the rectangular fixing plate which I had assumed concealed the motor) to see what is inside. It may only be the limit switch controls.

The power lead from the main control unit has four leads - earth, blue (common), brown (down), and black (up). The brown lead and black leads are interrupted by their own (adjustable) microswitch limit switches. They then, with the blue lead, go to the central motor. But the capacitor (which is 8uF 5% 450V AC) connects across the brown and black leads only. Harry mentioned a separate start winding being required for a single-phase reversible motor, so I'll have to look up reversible AC motors later to find out why it is connected that way.

However it works, I have to agree with the statement on that URL you supplied: "This type of tubular motor is designed by international advanced technology..."

I'd love to know how they design how those gears will work!