How to motorise the roof.

[Earl]

Im considering the options of motorising the roof so it can be automated, this is heavy so its going to take some grunt i guess, it will need a way of knowing its open or closed, and be controllable from the Observatory PC.

It has mains power so thats a help.

Where do i start?

[The Sailor]

Okay, I have done it, now don't laugh but I used a 12v winch , it is on the roof outside the dome in a waterproof box with the control and battery inside. What I done was remove the hawser from the winch and replaced it with a nylon rope which was around the outside of the dome. The winch cost me £55 brand new on fleabay and all works well, only problem is noise from the winch, have been working on that .

Jim

[Gina]

Very interesting This is something I might be looking into later for my roll off roof. I was thinking in terms of a nylon rope over two pulleys with one driven by a reversible motor. The problem is the motor - well motor/gearbox, it'll want slowing down (unless I use a starter motor).

[Earl]

My first though is to have to motorised wheels on the roof which drive a wheel on each side, but these will need to be in sync and it doubles the amount been controlled.

[JamesF]

I wonder if garage door openers provide any ideas that can be pinched? Or even if one could be used outright?

James

[The Sailor]

I already have the wheels on the dome, this runs on the outside of a 6" lip, a plastic garden hose is at the bottom of the lip and the wheels to ensure a straight turn with no lateral movement. The wheels are attached to an angle iron ring which is attached to the dome. I don't really need the winch as the dome turns very easily with a touch of the hand but me being me I had to give it a go at motorising it .

Jim

[The Sailor]

I wonder if garage door openers provide any ideas that can be pinched? Or even if one could be used outright?

James

Probably could James, did think about it but went for an option I knew would work.

Jim

[JamesF]

Yes, I think different solutions are likely to be required for domes and roll-off roof obsys.

James

[Gina]

Yes, I think different solutions are likely to be required for domes and roll-off roof obsys.

James

Definitely!

I find with my (straight action) roll off roof I can push or pull one side and it stays straight - it isn't necessary to drive both sides. So that will help. Another problem though is to be able to disengage the motor drive in case of a power failure or failure of the motor or control electrics. Maybe I could solve that by having the ends of the rope attached to the ends of a bar with a hole in the middle connecting to a bracket on the roof. Then a pin (perhaps a tractor link pin) could make the connection. In event of a failure the pin could simply be pulled out and the roof moved manually.

[ollypenrice]

I think a lot of people do use garage door openers as James suggests. (That's for roll offs, not rotating domes.)

Olly

[Earl]

I have been looking at garage door openers, the look promising, I need to do a few more mods to my tracking, then ill see about fitting one somehow

[JamesF]

Do let us know how you get on. I'm all for letting someone else make my mistakes for me

James

[ncjunk]

i was looking at sliding gate openers as they come with some inputs and outputs for safety reasons. So you could hook a couple of reed switches up so the roof can only move when the mount is parked.

the only problem for me is they are slightly bigger than the available area i want to stick the motor in the roof.

[Earl]

Do let us know how you get on. I'm all for letting someone else make my mistakes for me

James

Im the man for that !!!

[laser_jock99]

You might be able to use a TUBE MOTOR coupled directly to a roof roller wheel to shift the roof, They are quite torquey (usualy used inside roller shutter doors) and if memory serves me correctly some have built in limit switches. This means you should be able pre set the open and closed roof positions within the drive unit itself- no need for external wires / sensors.

http://www.ebay.co.uk/itm/TUBE-MOTOR-140nm-H-D-TUBULAR-ROLLER-SHUTTER-PART-INTERNAL-DRIVE-MOTOR-240V-/120939988829?pt=UK_Home_Garden_Doors_LE&hash=item1c2895c75d

[JamesF]

I might use the limit switches, but I'd never rely on them. I'd always have a cut-out at each end of the travel mechanically operated by the roof itself. It's ok if you have a dome and for some reason it doesn't stop turning, but I'd not want to find that because of an electrical failure my roll-off roof hadn't stopped and had fallen off the end of the obsy yanking the motor from its mounts and pulling all the cabling out with it.

Ok, so call me a pessimist

James

[ncjunk]

I might use the limit switches, but I'd never rely on them. I'd always have a cut-out at each end of the travel mechanically operated by the roof itself. It's ok if you have a dome and for some reason it doesn't stop turning, but I'd not want to find that because of an electrical failure my roll-off roof hadn't stopped and had fallen off the end of the obsy yanking the motor from its mounts and pulling all the cabling out with it.

Ok, so call me a pessimist

James

no your not a pessimist it's whats required. You have a chain of switches which when all healthy indicate its ok to move. Then switches on the roof to indicate travel in that direction is complete and finally a switch which cuts the power directly if it carries on past the direction complete switch.

You could also include a controller of your own in addition to the gate opener one but I think they have the safety aspect pretty much covered.

you could also include timers so that it stops after a set time (i think thats included). And if you had end stops (why wouldnt you??) you could put a current meter on the motor and if the current draw is excessive for a set period cut the power. (if you want to be really paranoid)

[Gina]

After my heavy roof assembly got lifted off bodily by the wind and carried up in the air and dumped 20 yarfs away, I'm paranoid!

Those tube motors look interesting but they don't say how big they are. I guess you could wrap a rope two or three times round it to provide a drive. Need more info.

[pete_l]

Ok, so call me a pessimist

I'd also be inclined to operate the roof motor from it's own 12V battery that's permanently on a float charge. So when the power does go off *and* it then starts to rain (lightning is a good way to trip substations) the roof will close itself.

For the paranoid's paranoid, you could even arragne that the roof opens "uphill", so if the power does go away, gravity (and a stop at the end) will close the roof without any artificial help.

[ncjunk]

I wouldnt trust gravity close anything, shifty looking chap that gravity. you could only do this if your telescope had absolutely no possibility of being in its path otherwise its a no no.

i'd use a ups with a controller to detect power failure and close but only if the scopes safe.

[ollypenrice]

My rooves and roll offs are all 'captive' when closed, ie there is a tongue under a hoop to prevent lift off. Mind you, you never know, with enough wind.... Wind is as dodgy as gravity. It can lift Jumbo Jets into the air. (I've been in one when this happened. It took off and went right across the Atlantic...)

Olly