Jump to content

Banner.jpg.5ed196c1e70861ebc79109e023c96067.jpg

Gina's Observatory Roll-Off-Roof Automation


Gina
 Share

Recommended Posts

It's 6mm nylon and does have quite a fair amount of stretch as expected with nylon rope. It should be quite capable of handling the tension though. I might change to a stronger type of rope if I have any problems. A bit of stretch is no bad thing with the rope being wound up onto an axle as the total length will vary slightly.

Link to comment
Share on other sites

Now have 44AH car battery (sealed) and appropriate terminals. And this afternoon connected the battery cables from the winch control to the battery terminals and the other two cables from control to winch motor. Then tried it out - yes, it's noisy so I'll mount the winch on rubber mountings. The winch drum does seem to rotate at a reasonable speed though :)

Link to comment
Share on other sites

Do you still have your webcam link Gina so we can see the roof in action?

It's not working at present - a problem with the computer that serves it I think. I'll check again. ATM any time the roof opens or closes it's me pushing it :D

I'm looking at how to mount the winch currently but the weather isn't helping - it keeps raining.

Edited by Gina
Link to comment
Share on other sites

  • 4 weeks later...
  • 2 months later...

A little bit further with the design. This is how I'm thinking of controlling the winch. Two changeover relays replace the push buttons in the hand controller to turn the winch one way or the other. I first thought of power MOSFETs which although rated at 50 or 100 amps, I couldn't see how the legs of TO220 packages could take the 30 or 40 amps of the winch. The drain being the tab could, but the source is a leg which I wouldn't rate at more than 20A (if that) continuous current. I searched the net but couldn't find any power MOSFETs in any other case. I decided I needed something capable of switching 30 or 40 amps, preferably with some to spare so I looked at car relays. I found some 70A changeover ones on ebay - that should give adequate spare capacity. They can be driven by 2N7000N low power MOSFETs which are more than adequate and these will work directly off the digital outputs of an Arduino. The switches connecting to the Arduino are limit switches which close when the roof is fully open or fully closed.

I already have a 100A battery switch as shown in the positive line but I expect to add a fuse too.

post-13131-0-30976800-1359915019_thumb.p

Link to comment
Share on other sites

Link to comment
Share on other sites

This thread has given me some food for thought on the planning of my observatory, all this and that is just for the roof wow. i think it could take some time to do mine. but hopefully will be worth it.. :grin:

An observatory is well worth it :) Particularly in this country when you often need to cover up in a hurry! I love mine :)
  • Like 1
Link to comment
Share on other sites

I've made a bit of progress today on this project. I've mounted the winch on the scope room wall on the south side just below the trolley. It's bolted to a piece of 11mm OSB which straddles two uprights and covers the running rail. Adittionally it is bolted through the OSB and through the 3x2 runner rail with a coach bolt (they'll be two bolts later though one is probably quite sufficient). The OSB is screwed to the obsy framework.

I've been carrying some simple experiments and have the following results :-

  • The winch is noisy - not surprising on a 2ft square sound board ably assisted by the side of the obsy. I may be able to improve this with damping.
  • The winch is a fair bit slower than opening or closing the roof manually.
  • The roll off mechanism is sticking in a couple of places - this needs looking into.
  • The cord is too thin and too elastic - it managed to pull the roof open but broke where there was extra resistance.

I think nylon rope has too much elasticity for this - the current piece behaved almost like a "bungee" and when the roof was moving it was going in jerks rather than moving steadily. Of course, wire rope would not do this and would have plenty of strength but from my experiences with yachting, I don't like wire rope. It would be useful to have a small amount of elasticity - it can allow for the winch continuing to turn a little after the limit switch has operated. Also, rope can be cut relatively easily in the event of a breakdown and sudden rain. I'm thinking in terms of terylene yacht rope - very strong and low stretch, but expensive.

I suppose there are ways to use wire. eg. some elasticity could be introduced with a coil spring and maybe a latch could provide emergency disconnection. But the problem with wire is the termination without special equipment. I'm not going to splice wire ever again!

Link to comment
Share on other sites

The noise is one of the problem I encountered, I have rubber under it and polystyrene round it, just helps to damper it :(

I looked at a number of options for pulling the dome round, polyproplene and nylon were out and I tried webbing strap, good but went out because the roll would not fit the winch drum. I ended up settling for twine, no elasticity, cheap and nasty :) I still have the orignal cable but that would be too heavy.

Jim

Link to comment
Share on other sites

Been on ebay... 6mm braided polyester rope with a breaking strain of well over a tonne (1390Kg) £1.05/m plus carriage :- http://www.ebay.co.uk/itm/Marlow-Double-Braid-6mm-Rope-Braid-On-Braid-For-sailing-Dinghy-Yacht-blue-/281017601631?pt=UK_CarsParts_Vehicles_BoatEquipment_Accessories_SM&hash=item416df44e5f

The nylon rope I used was laid rather than braided and tended to unravel. The link above is for Marlow rope, recognised in the sailing world as the best - not that I need the best yachting rope - I could see it I can find cheaper, if it's worth it. I reckon I shall want around 8-10m. A 10m length comes to £15.50 (£5 carriage).

Link to comment
Share on other sites

The noise is one of the problem I encountered, I have rubber under it and polystyrene round it, just helps to damper it :(

I looked at a number of options for pulling the dome round, polyproplene and nylon were out and I tried webbing strap, good but went out because the roll would not fit the winch drum. I ended up settling for twine, no elasticity, cheap and nasty :) I still have the orignal cable but that would be too heavy.

Jim

Yes, the original cable is far too heavy. Polyester (Terylene) rope is extremely strong - I used it for halyards (pulling sails up) in dinghy racing many decades ago. It can be handled by hand unlike wire. If you were a sailor you will know all about this I suspect :D

One thing I've yet to do is put a divider in the winch drum to separate pulling-open rope from pulling-closed rope. It'll also need another fixing hole but that's no problem - have power drill and files. Since the drum is cast in one lump I shall have to make the divider in two halves. I guess Araldite might do to glue the parts to the drum and themselves.

I think I can probably reduce the noise quite a lot but it's not exactly defening even sitting a few feet away and controlling it manually. I asked my OH who was in the house if he heard it from there - he didn't :)

Link to comment
Share on other sites

One thing I've yet to do is put a divider in the winch drum to separate pulling-open rope from pulling-closed rope. It'll also need another fixing hole but that's no problem - have power drill and files. Since the drum is cast in one lump I shall have to make the divider in two halves. I guess Araldite might do to glue the parts to the drum and themselves.

Gina, I used plastic pipe collars for where radiator pipes enter the floor, I had to widen the centre hole to fit the drum. Two placed "bottom" to "bottom" , put on the drum, glued and hey presto. The great thing is the "top" is sloping into the space for the cable and helps to guide as well.

Jim

Link to comment
Share on other sites

I use wire on mine as all the rope/cords I tried stretched too much or were too thick for the drum. Still too noisy though, so I'm looking at trying to find something like a sliding gate opener to modify I think.

Several people have used gate or garage door openers - I tried to find something suitable without spending a fortune but had no success with any linear device. I'd really like a rack and pinion system. I also thought of a chain and sprocket system. I've ended up with winch and string :D Well - yacht rope once I've measured how much I want and ordered it.
Link to comment
Share on other sites

How about sash window cord - not so sure on strength, but it is non stretch and should take a fair bit of wear.

I don't actually know what the breaking strength is but I wouldn't have thought it sufficient.
Link to comment
Share on other sites

Gina, I used plastic pipe collars for where radiator pipes enter the floor, I had to widen the centre hole to fit the drum. Two placed "bottom" to "bottom" , put on the drum, glued and hey presto. The great thing is the "top" is sloping into the space for the cable and helps to guide as well.

Jim

Yes, I seem to remember reading that. What glue did you use?
Link to comment
Share on other sites

Loctite superglue, thing is Gina once you put a spare round of cord around the drum the collars should stay in place anyway, I actually used the superglue on the cord as well, this helped it stay in place.

Jim

Yes, that's a good point :)
Link to comment
Share on other sites

I've decided that having the winch mounted on that OSB is asking for maximum noise! So I've stripped it down again. I can mount the winch directly on the running rail with 8mm coach bolts (right through with the heads covered by the roof overlap) and down one side onto an upright either with coach bolts screwed into the wood or a roofing bolt right through to the outside but I'm none too keen to bolt through the waterproofing. Also it would depend on where it came through with respect to the shiplap profile. For further noise reduction I guess I could open up the mounting plate holes and use rubber grommets as rubber mountings but I'll see how it goes without first.

Link to comment
Share on other sites

I've been looking at the winch and have taken the drum end apart - very easy, just two Allen screws not even very tight :) The drum is attached to the motor part with a short spline. There is also a rubber seal here and the motor is sealed - so, yes, this winch is designed to get wet. At the other end of the drum is just a plain sleeve bearing with a wavey washer to hold the drum onto the spline. There is a hand nut on the end which doesn't seem to do very much.

One thing that I have been wondering is whether if I were to fashion a V pulley that would give sufficient grip to the cord to move the roof. It could have ridges to help grip the rope. I've done this before though with bigger ropes. Rope wrapping round a ridged V pulley gives a good grip and is the foundation of sheet winches on yachts.

Edited by Gina
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.