Electric ROR Ideas

[decoyp]

Hi,

Very interesting forum. I've been trolling through some of the posts to get ideas for my own observatory and there are loads of great ideas. I've started building mine over the past few weeks. It's a modified shed similar to some I have seen here. I managed to get a cheap shed from "Focus DIY" before it closed down and have been modifying it to make it strong enough for my purpose. I've probably spent as much on materials to modify it as I have on the original shed !!

Anyway, the reason for the post is to find out if anyone has plans to make the roof of their observatory electrically operated. This is my aim although it will probably be a manual setup for this year at least. I want the setup mainly for imaging. So I need to let the camera run for long periods and then sneak off to bed. I would like to be able to either remotely close the roof i.e from a PC in the house, or after a pre-determined time, or by input from a rain sensor or other device. (By the way do rain sensors detect snow ??)

I realize this is a big question, but at the moment I am only after some additional ideas about how to actually motorize the roof . I've got some ideas of my own and as always, am trying to do things a cheaply as possible. My first idea for the motors was to use some old battery drills that I have. They produce a lot of torque and would probably be OK with the loading. My other idea is to use wiper motors as they are complete with a high ratio gear box so plenty of torque also and will probably be easier to reverse.

What sort of method of drive do people use ? I've seen chain operated, and rack and pinion (expensive). I was thinking a cheaper alternative would be to use a rubber wheel on a high friction surface, but what about when it gets icy??

Any thoughts or suggestions would be greatly appreciated. If anyone has done this successfully I would be interested to hear how you did it.

Thanks

Richard.

[Aoraki]

Hi, the only thing I had considered was a garage door opener, new they may be over buget but there are usually some second hand on Ebay. As for any of the electricory self closing etc, sorry but I don't know but I will be watching this thread with interest!

[Gina]

I'm hoping to motorise my RoR in time - I have yet to finish building it . I too have several ideas but nothing fully designed. I too thought of the friction version of the rack and pinion. Also, using cord and pulleys. But the motor remains the main stumbling block. I too need to keep costs down. Although I expect my roll off to move fairly easily on its wheels, there is still the inertia of all that mass. Starting torque would be high.

A DC motor with permanent magnet field would be easiest to reverse but would one be powerful enough, I wonder. A wire-wound field with an armature fed by brushes also provides the ability to reverse by reversing the armature supply only. A parallel wound motor, where the field and armature are placed in parallel, would probably be best - producing high torque and reasonably constant speed under varying load. Series wound motors, while producing good starting torque, tend to run away as the load decreases.

I'd be very interested in hearing from anyone who has found a source of cheap motors.

[decoyp]

Thanks for the replies guys. Seems that most people have similar ideas and consequently we are facing the same stumbling blocks and financial constraints. The problem is for me not really knowing how much load its going to take to actually start the roof in motion. I've got the roof almost completed on my shed and it seems to move quite easily but the initial starting effort is quite high. Suppose I could get one of those spring gauges we used to use in physics at school for measuring load in Newtons (more years ago than I care to remember !!), and then I would at least know a figure to base a design around.

I'm not too concerned about motors running on a bit as I think this could be controlled with a carefully placed limit switch and some kind of damper. I've seen hydraulic dampers on ebay.

You are right Gina. The kind of motor choice is critical. And the fact that they all reverse in slightly different ways. I'm hoping to achieve this in the old fashioned way using relays and avoiding expensive custom built motor controllers. Unless anyone knows of a cheap off the shelf solution. I've already woken up in a cold sweat trying to figure out the exact configuration of the relays to achieve this.

I too initially thought of a garage door opener, but the problem is packaging into my design. My roof rolls off onto a gazebo type structure. The door opener would have to sit there somewhere and be open to the elements. Also on the ones I've seen, they can be energised by pushing a button on the side, not so secure with all that gear inside the shed. Housing the opener inside the Observatory would probably take up too much room.

However the jury is still out on that idea as it has the merit of being an off the shelf solution.

I will take some pics of my setup soon and post them.

Cheers

richard

[ncjunk]

I'll be using a gate opener that you can get for the gate on a driveway. They come in kits with 4 m worth of toothed rail that is attached to the ROR and the motor attatched inside of the shed base (my shed has a perfect position for one).

They come rated per weight of gate, normally 400kg but other wieght ratings exist, and i think it will be fine. This is one part of my observatory i really can't be bothered to home build. I have done a focuser, stripped the eq6 and played with a cloud sensor but i have no interest in a motor on a roof so i'll buy one (about 300€)....it just seems too boring for me to bother with!

[steelfixer]

Hi Richard.

My obs is a little different to what most people build as my roof is a split design where the section over the scope slides inside the other section.

I am going to motorise it by using a length of 20mm threaded rod fixed to the back wall of the obs..

On the rod there will be a barrel nut with a gear cog welded to it.

The barrel nut is held in a bracket with bearings that is fixed to the sliding roof section.

The drive will come from a 12 volt motorcycle starter motor via a small gear cog to reduce the speed and increase the torque.This is also fixed to the sliding roof section.

When you press the button the roof will screw itself open or closed along the threaded rod.

Limit switches either end of the threaded rod will stop the motor.

Dead simple to do but extreamly effective.

Graham.

[Gina]

Interesting Graham But do you have a way of disengaging the drive in case of a power or motor failure and it's just started tipping down with rain?

[Merlin66]

I used a 12V 25W window regulator motor/ gearbox ( why? - In a previous life I used to make them - 28,000 a day!!)

A "endless" pair of 3mm s/s cables run over pulleys at each side of the roof down to a tensioned cross shaft driven by the motor....worked very well. The roof could still be manually opened/ closed by relieving the tension on the motor/ cross-shaft and turning the shaft by hand..

HTH

[Aoraki]

24v gate opener approx £289, 240v about £417 both plus vat and drive rack, this is for CAME gear but there are lots of others out there. I think garage door opener would be a better solution and cheaper @ £199 plus vat.

[ncjunk]

24v gate opener approx £289, 240v about £417 both plus vat and drive rack, this is for CAME gear but there are lots of others out there. I think garage door opener would be a better solution and cheaper @ £199 plus vat.

I agree with you completely on price, I just have no interest in designing this part of the Observatory and the gate opener will fit with no modification and very simple installation. Having said all that it may be taken out of my hands and be down to money.

I can pick them up for 300€ including the drive rack, I wont pay 420 for it.

[decoyp]

I like the sound of all these ideas. The gate opener sounds like it would give a professional solution but also sounds a bit too dear for me. I hear what you're saying about reaching a point where you can't be bothered about doing it yourself. We all reach that point at different times I guess.

The threaded rod idea sounds great also. That would give quite a controlled motion with no chance of the drive jumping out of engagement if there is any flexibility in the system. Perhaps a type of universal joint that could be uncoupled when needed could be used to allow manual operation. I don't know if you've already got this built in. The pulley system also sounds like a good solution.

One question has occurred to me though. If the drive system is only on one side of the roof (I presume these ideas are not installed down the middle of the shed), will that put a twist on the roof as it tries to open ? I was envisaging putting a motor on each side to reduce the load and avoid twist. Although they would have to be in sync or it might cause other problems.

I just put a set of scales against the roof and pushed on it to see how much force it takes to open it. It registered about 3Kg to start and about 2.5Kg when running. Didn't seem too bad although the roof felt isn't on yet so it will probably increase. I'll have to dig around on the web to see how you equate this to "torque required" and build in a factor of safety before I start looking for motors. It seems that the car industry has the answer though in the form of window motors/ starter motors etc.

[Freff]

I was thinking of the threaded rod method also. I have built a CNC machine which uses the same principles and the small stepper motor exert huge amounts of torque.

I know two motors can work in sync quite easily, so a two threaded screws (Acme thread) would eliminate twist.

Now I'm not sure how this could be controlled. My CNC steppers are controlled by a simple breakout board and stepper drivers, and the computer. Now it's getting a bit complicated.

It would be a nice project to do. I don't see any big obstacles. The breakout board, drivers and power supply could be housed in a small cabinet with the wires running to the stepper motors.

A programme like Mach3 could then run it from the up and down arrows on the computer.

Perhaps this is a project to do in the future when all I can do is look at cloudy skies.

[Gina]

Plenty of cloudy skies lately - well here anyway! Plenty of the damp stuff coming out of them too!!

I was thinking of arranging the RoR drive in the middle but I don't know how yet. I'll wait until the RoR is built then see how and where the drive could go. A rope/cord and pulley system could be arranged to push/pull both sides at the same time with one drive. OR you could have a shaft going the full width of the roof and drive the sides simultaneously from the shaft. The drive could then go anywhere along the shaft.

[Aoraki]

I just put a set of scales against the roof and pushed on it to see how much force it takes to open it. It registered about 3Kg to start and about 2.5Kg when running. Didn't seem too bad although the roof felt isn't on yet so it will probably increase. I'll have to dig around on the web to see how you equate this to "torque required" and build in a factor of safety before I start looking for motors. It seems that the car industry has the answer though in the form of window motors/ starter motors etc.

That's about 30Newton to start and 25Newton to keep going, gate and garage door motors are usually rated in Newtons.

[George]

Already done mine a while back using a garage door opener.

Thread with pictures and video demo here

http://stargazerslounge.com/diy-astronomer/85087-motorising-my-roll-off-roof-part-2-a.html

[decoyp]

Wow Tony. you built your own CNC machine !! I'm sure a RoR observatory is really no challenge for you. Can you let me know what controllers you used for the stepper motors and the motor spec etc. I'm very interested in this as it is for me the best solution, because it lends itself to computer control. I don't want to really get into observatory control software as it probably does a lot more than I need at the moment. However a basic open/close computer interface and someone to write me a very basic application is probably not outside the realms of possibility. I was going to do it the old fashioned way with relays, DPDT switches etc but always wanted to get computer control ultimately.

I'm coming around to the threaded rod idea too. I have given it some thought and there are several configurations that would suit my setup. Great suggestion Gina about one drive shaft at the rear providing drive to both sides of the roof. That is worth developing too. Having a central drive will not work for me as it would get in the way of my scope setup, and could block a clear view in some orientations it would probably be fine for some designs though.

Thanks for all the suggestions. Will keep you posted on the progress and some pics at some point. I wont get to work on it until the weekend now as the evenings are too dark. Hopefully I can get the roof completed and then I've broken the back of it from the construction point of view. Should be up and running in manual mode before long.

Thanks

Richard

[Freff]

Hi Richard. Here is an image of my CNC machine. http://stargazerslounge.com/1875845-post40.html

I don't have the details of the drives for the stepper motors at hand, but can dig them out tomorrow. I think these are the ones...

MSD415 Microstepping Drive, Stepper Drives

These are the steppers I used..

NEMA 23 High Torque Stepper Motors, Stepper Motors

The breakout board was a simple one similar to this...

MCP25 Breakout Board, Accessories

[decoyp]

Thanks Tony. I'll probably be picking your brains a bit later about these ideas if that's OK.

Cheers

Richard

[Freff]

No problem, glad to be of help.

[steelfixer]

Hi again.

In answer to your questions.

The threaded rod will be in the center of my roof. Because of my roof design it will not get in the way as it will be over the fixed roof section which I use as a workshop.

I will not need to manually open or close the roof as I will be running it from a 12 volt mains supply with a battery backup.

I have however decided to do a belt and braces job, I will attach the threaded rod to the rear wall using a spring loaded cottel pin. Flick up the spring clip remove the pin and just push the roof shut threaded rod and all.

Graham.

[steelfixer]

Just to add.

If anyone want a hand designing or fabricating parts let me know.

I have my own steel fabrication business and am always willing to help out fellow SGL members if I can.

Graham

[Aoraki]

Just to add.

If anyone want a hand designing or fabricating parts let me know.

I have my own steel fabrication business and am always willing to help out fellow SGL members if I can.

Graham

Me too, small world!

[Gina]

Ah! That explains the perfect welding Not that there aren't some good amateur welders, of course.