Roll-off shed rails suggestions

[SteveBz]

1 hour ago, JamesF said:

Ah, jolly good.  I couldn't find any close-ups of the wheel fixings, but I can certainly take some if it would be helpful.  Just let me know.

James

No, it's good.  I'm going to go with DaveS' choice and put some fascia around it.

Thanks for the offer.

Kind regards,

Steve.

[SteveBz]

Goodness me it's been a bit hard getting the stuff from Brundles, that was in turn on back order from Italy!

However, looks like it'll be arriving this week.  🤞

So now I'm thinking about automation.  Maybe a little motor, an elongated bike chain and a couple of relays off the long suffering Arduino.   What do you do?

Kind regards

Steve.

[ollypenrice]

I've found v-section steel wheels to work best and I've also found that they work just as well running on dead cheap angle iron as they do on the far more expensive, dedicated vee rails. The angle iron is bolted to the support such that its flats are vertical and horizontal and the wheels run along the top edge of the vertical flat.  This may even be better than the v-rail but it certainly isn't worse.

We have used modified garage-door-openers driving bicycle chain twice here, on a large shed and a small. Both times it worked for a while but, in the end, both pegged out. We now use driveway gate openers, rack and pinion, and these are far more convincing both in their action and their longevity. If you choose this option I have one key tip: bolt the toothed rack not to wood but to a length angle iron fixed to the wooden roof.  On two sheds we found that warpage in the roof timber threw the rack and pinion out of mesh fairly regularly with seasonal change. The angle iron comes between the warpage and the rack and keeps the rack straight. These systems are now very stable.

Be sure to design in some anti-lift system to stop the roof flying off. They will if they can!

Olly

 

 

Edited July 25, 2021 by ollypenrice
typo

[JSeaman]

I went for U section steel and nylon casters (~£70), works well. 

To automate it, I went for a winch (£60) and a few pulleys and some wire rope (~£25 for a large kit). I have the option of either a manual opening or Arduino to trigger the relays, it works something like this :

 

To open, I flick my rotary switch and press the button to start. To close it, I do the opposite.

 

Alternatively, driving the relay via a FET off an Arduino will do the same thing

[SteveBz]

On 25/07/2021 at 08:27, ollypenrice said:

We now use driveway gate openers, rack and pinion, and these are far more convincing both in their action and their longevity.

Hi Ollie,

Thanks for this. How do you operate the garage opener?

Kind regards

Steve.

[SteveBz]

On 25/07/2021 at 08:56, JSeaman said:

To automate it, I went for a winch (£60) and a few pulleys and some wire rope (~£25 for a large kit). I have the option of either a manual opening or Arduino

Hi JSeaman,

Thanks for your diagram.

Does the winch close too in case of rain? I'm thinking I want to set it up at say 3pm, it rains at 5pm but is clear by 10. It opens at 10, but starts raining at 2am, so it closes again.

Kind regards

Steve.

[SteveBz]

On 25/07/2021 at 08:56, JSeaman said:

To close it, I do the opposite.

OK, I can see it does. How does it 'push'?

[SteveBz]

On 25/07/2021 at 08:27, ollypenrice said:

Be sure to design in some anti-lift system to stop the roof flying off. They will if they can!

Is this automated or a manual catch?

Steve.

[ollypenrice]

3 hours ago, SteveBz said:

Hi Ollie,

Thanks for this. How do you operate the garage opener?

Kind regards

Steve.

It was triggered by a Dragonfly control unit since the system is robotic. Basically the motor was fixed and the chain ran from one end of the roof to the other. The same unit now triggers the gate openers. You need magnetic sensors at each end to instruct the motor to stop but this control facility is built into both garage door and driveway gate systems.

1 hour ago, SteveBz said:

Is this automated or a manual catch?

Steve.

Trust me only to have a picture taken before the anti-lift was fitted to this one! But I've marked it in red. You can see that the roof sides come down below the level of the rail carriers. We then fit a full length baton along the bottom of the roof sides, on the inside, so that it runs along below the rail carriers. If it tries to lift this baton hits the rail carriers. This means that the anti-lift operates along the full movement of the roof.

Olly

[JSeaman]

Yes the winch is push/pull, simply put a separator on the spool and wind one side in the opposite direction. This unspools one side while spooling the other to open and then reverse winch direction to close

[SteveBz]

On 25/07/2021 at 08:56, JSeaman said:

I went for U section steel and nylon casters (~£70), works well. 

To automate it, I went for a winch (£60) and a few pulleys and some wire rope (~£25 for a large kit). I have the option of either a manual opening or Arduino to trigger the relays, it works something like this :

 

To open, I flick my rotary switch and press the button to start. To close it, I do the opposite.

 

Alternatively, driving the relay via a FET off an Arduino will do the same thing

Hi Guys,

So we have a start.  Here is a sliding roof that performs 2 functions.  Firstly, it rolls off, but it only moves about 1.5m to expose the scope. Secondly it keeps the bikes and lawnmower dry.

Needs some fascia and stuff.

@JSeaman, can you send me a link for your reversible winch?  I find it hard to see which winch behaves the way you describe.

@ollypenrice, the roof weighs so much I can't lift it.  maybe a third of a tonne.  Do I really need to worry about the wind taking it away?

Tx

Steve.

 

[JSeaman]

Hi Steve, just buy any normal winch and then make a divider on it. 

Some pics of what I did ...

Bought a winch

 

Took the barrel out and drilled a second hole

 

Made a divider (cut a circle with a slit, bent it open then put it on the barrel and bent it back, was going to weld it but it was a good fit

Wound one rope one way and a second in the opposite direction then you have push and pull!

[ollypenrice]

2 hours ago, SteveBz said:

 

@ollypenrice, the roof weighs so much I can't lift it.  maybe a third of a tonne.  Do I really need to worry about the wind taking it away?

Tx

Steve.

 

Yes.  If you think of wings, they are not very big but they lift massive aircraft into the air. The highest wind speed recorded in Sussex (where SGL tells me you live ) is 82 mph. While this is given as a record, gust speeds in specific local situations may go unrecorded yet still be remarkably high. If the wrong gust goes over your roof, that's all it takes. Here on the forum we've been told of several flying observatory roofs, one of which was mine. It was chained down to two strong-looking steel brackets but these turned out not to be as well made as they looked and one of them sheared. The roof had survived a wild night and the wind had dropped by morning. I had a check then went in for breakfast. When I came out, despite the reduced wind speeds, one of the observatory roofs had flown off and damaged another observatory. It took four of us to lift it back on and, remarkably, it was fine, as was the setup inside. You just need to right gust...  (or should that be the wrong one?)

Olly

Edited August 9, 2021 by ollypenrice
Typo

[SteveBz]

2 hours ago, JSeaman said:

Made a divider (cut a circle with a slit, bent it open then put it on the barrel and bent it back, was going to weld it but it was a good fit

This is beginning to feel at the edge of my technical competence. 😅

I'll investigate some more.

[JSeaman]

 It's really easy even if you're a novice, just grab some 1mm steel and hacksaw/bend to your heart's content.. You could probably do it out of wood/cardboard etc. in a pinch. Just expoxy it to the main drum of the winch and wrap your rope in opposite directions

[JamesF]

1 hour ago, ollypenrice said:

Yes.

Very much so.  In the wind a roof can work exactly the same way that a wing does.  Obviously it was designed with the intention of flying, but the 22.5m² area of a Spitfire's wings was enough to lift three tonnes of aircraft off the ground.  I can't see the size of your roof after a quick scan through the thread, but I'd guess it is perhaps a third to a half of that area, and maybe less than a tenth of the weight?  It probably doesn't need to be very efficient as a wing to generate enough lift to match or even exceed it's own weight

Civil engineers do actually have to take this problem into consideration when they design buildings, and modern houses have the roof plate strapped to the walls with steel bars to prevent the roof lifting in high winds.

James

[JamesF]

By "your roof" there, I meant the OPs, not Olly's.  Apologies if that wasn't clear.

James

[Tiny Clanger]

Practical demo (it always impressed the 9 year olds, I hope some of them recalled the name Bernoulli Principle after messing around with it .)

Take a sheet of paper, half a4 (a5 !) or reporter's notebook size works well  . Hold it horizontal with the short edge just below your lower lip, so the far end of the paper hangs down . Blow across the top of it.  The effect is surprising if you've not tried it before.

Heather

 

Edited August 9, 2021 by Tiny Clanger
clarity

[ollypenrice]

44 minutes ago, Tiny Clanger said:

Practical demo (it always impressed the 9 year olds, I hope some of them recalled the name Bernoulli Principle after messing around with it .)

Take a sheet of paper, half a4 (a5 !) or reporter's notebook size works well  . Hold it horizontal with the short edge just below your lower lip, so the far end of the paper hangs down . Blow across the top of it.  The effect is surprising if you've not tried it before.

Heather

 

Interesting! I couldn't make it work because I was holding the edge of the paper horizontal. This guy holds it pointing upwards with the paper arcing over and it does work.

So back to roofs: high velocity airflow has low pressure, low velocity has high. Bad news for sheds, because the air velocity below the roof approximates to zero while that on the outside is the wind speed. And I think it gets worse, though I'm not a physicist: once the high pressure has lifted up the roof it's highly unlikely that the now unstable roof will remain horizontal. It will have an angle of attack with regard to the approaching wind. If the randomly created angle of attack is leading edge low, trailing edge high, it will work like a racing car wing and push the roof down (where it will rebound and come up with an alternative angle of attack...). But if the angle of attack is leading edge high, trailing edge low, both lift and drag will briefly increase, meaning the roof will lift higher and be displaced in the direction of airflow - away from its walls. It will then stall and come down fast, rather in the manner of a French guillotine approaching an aristocrat's neck... 

As pilots like to say, 'If you want to go up, pull back. If you want to come down, keep pulling back...'

1 hour ago, JamesF said:

 the 22.5m² area of a Spitfire's wings was enough to lift three tonnes of aircraft off the ground. 

James

Also impresssively, a Formula One car could drive upside down along the roof of a tunnel from about 100mph upwards, I read. By that speed its downforce is already exceeding its weight.

Your observatory roof wants to fly!

Olly

[Tiny Clanger]

1 hour ago, ollypenrice said:

Interesting! I couldn't make it work because I was holding the edge of the paper horizontal. This guy holds it pointing upwards with the paper arcing over and it does work.

I should have elaborated , something like,  hold the edge of the paper below your lower lip so that edge of the  paper is horizontal , grip the paper either side of your mouth with thumbs and forefingers, letting the far end of the paper curve down naturally, then blow across the top ...  It's much easier to demonstrate than explain ! Each time I showed it to a new batch of victims, I asked what would happen, and 100% of the time the answers were a mixture of 'nothing' , and 'the paper will bend down more' .

Another demo I used was something like the one in this http://hawkquest.org/TA/XL/AirPress.pdf

except my version went with some thread through the straw , and children running around like headless chickens holding the thread vertical and tight to get the wing to rise. Activities they could do for themselves were more effective and memorable (and fun)  than a single demo by teach.  I soon learned to set off the more riotous activities just a few minutes before playtime, lunchtime or home time so they had to stop without me having to get too officious and spoil sporty.

Me 'Yes, of course you can take that fully functioning set of 'musical' pipes playing various notes which you've made from paper straws home !"

Class " Yay!"

Parents "  .... unprintable  "

[SteveBz]

On 09/08/2021 at 11:01, JSeaman said:

Hi Steve, just buy any normal winch and then make a divider on it. 

Some pics of what I did ...

Bought a winch

 

Took the barrel out and drilled a second hole

 

 

Made a divider (cut a circle with a slit, bent it open then put it on the barrel and bent it back, was going to weld it but it was a good fit

 

Wound one rope one way and a second in the opposite direction then you have push and pull!

It it the Silverline 748850 shown here?

Silverline 748850 Elektrische Seilwinde, 12 V 909 kg | eBay

[JSeaman]

Yep I run it at 24V with no problems but you can do this with most winches

[SteveBz]

26 minutes ago, JSeaman said:

Yep I run it at 24V with no problems but you can do this with most winches

Which is why you have 2 car batteries.

I think my roof is about 300 kg, so about 1/3 of the max spec.  Why do you run at 24V?  Is it faster to operate?

Steve

[JSeaman]

Correct on both counts. Two batteries in series for double the voltage makes the winch operate much quicker. I use one of the 12V cells for the relays (Which are less tolerant of 24V but often work OK)

The cheapo winches are a bit slow and very noisy, if you want to operate in the middle of the night then you could upgrade but if it can wait until daytime this works well

[SteveBz]

On 09/08/2021 at 12:56, ollypenrice said:

It was chained down to two strong-looking steel brackets but these turned out not to be as well made as they looked and one of them sheared.

So what hope do any of us have?  I've just installed some M8 turnbuckles. Is it enough? Time will tell.