Post by thread:[OT] How do you wind a wire rope around a drive wh

Hi, I am building a electric gate and are trying to use 4mm wire rope to pull the 4m gate in and out, my first attempt was a failure as I (mistakenly) thought that if I cut a groove in a pulley the right width for the rope that the rope would pay in and out in the same spot. I know how to get half a turn around the drive wheel by cutting a parallel groove but would like to get three if possible so it doesn't slip. I am using a PIC and rotary encoder to know where the gate is so I can accelerate and decelerate as quickly as possible, as the rotary encoder is on the drive wheel I can only tolerate a small amount of slippage. I have spent hours on the net trying to find the answer but don't seem to have hit on the magic search terms, I am sure I have seen this done with some sort of thread on the drive drum but might be dreaming it! regards Lee McLaren

A good solution is to mount your rope spool on a thread with a thread pitch = to your wire width. then the spool will move up and down at the same rate as your wire "eats it up". A second best idea is to use a deep grooved pulley/spool, and actually allow the wire to wrap multiple turns on top of itself. This of course results in non-linear rate of pull of the cable, but that probably does not matter for a gate. jon > {Original Message removed}

>I have spent hours on the net trying to find the answer but don't seem >to have hit on the magic search terms, I am sure I have seen this done >with some sort of thread on the drive drum but might be dreaming it! Normally there is some form of concave shape like on the windlass of a boat. The rope winds on one side and works its way down the slope and up the other side as the windlass turns. See this picture http://www.c-mesales.com/contents/media/powerwinch_26.jpg

----- Original Message ----- From: Lee McLaren <spam_OUTlmclarenTakeThisOuTtasnet.net> To: pic microcontroller discussion list <.....PICLISTKILLspam@spam@mitvma.mit.edu> Sent: Thursday, April 07, 2005 12:31 PM Subject: [OT] How do you wind a wire rope around a drive wheel more thanonceand not have it travel up the wheel? {Quote hidden}> Hi, > > I am building a electric gate and are trying to use 4mm wire rope to > pull the 4m gate in and out, my first attempt was a failure as I > (mistakenly) thought that if I cut a groove in a pulley the right width > for the rope that the rope would pay in and out in the same spot. > I know how to get half a turn around the drive wheel by cutting a > parallel groove but would like to get three if possible so it doesn't slip. > I am using a PIC and rotary encoder to know where the gate is so I can > accelerate and decelerate as quickly as possible, as the rotary encoder > is on the drive wheel I can only tolerate a small amount of slippage. > I have spent hours on the net trying to find the answer but don't seem > to have hit on the magic search terms, I am sure I have seen this done > with some sort of thread on the drive drum but might be dreaming it! > > regards > > Lee McLaren Could you remove your need for multiple turns if you increased the tension in the rope? If so consider using a weight, hanging from a pully wheel and placed on the rope). The groove in the pully may actually need to be a sharpe V shape two or three times as deep as the diameter of the rope. Regards Sergio Masci http://www.xcprod.com/titan/XCSB - optimising PIC compiler FREE for personal non-commercial use

Hi Lee If you use a single turn around a pulley, then there is always slip as it enters on one side of the pulley, and exits 4mm stepped over. So the wire is always rubbing against itself. Works, but the wire will soon get scuffed. If you have more than one turn, the situation becomes impossible, as the the wire will 'walk' to one side of the pulley, as you've found out. In order to work, the wire approaching the pulley has to shift the other turns sideways to make space for itself. This situation is fine if the width of the pulley exceeds the travel. In other words, four turns around a pulley, but travel is only three revs. You've probably seen this on older printer mechanisms, or some floppy drives that use a flat strip. I would suggest using a bicycle type chain. It's positive, easy to install, and if you put a keeper above the chain sprocket, it means someone cannot lift the gate off the rack as in most situations. Regards Roland At 09:31 PM 07/04/2005 +1000, you wrote: {Quote hidden}>Hi, > >I am building a electric gate and are trying to use 4mm wire rope to >pull the 4m gate in and out, my first attempt was a failure as I >(mistakenly) thought that if I cut a groove in a pulley the right width >for the rope that the rope would pay in and out in the same spot. >I know how to get half a turn around the drive wheel by cutting a >parallel groove but would like to get three if possible so it doesn't slip. >I am using a PIC and rotary encoder to know where the gate is so I can >accelerate and decelerate as quickly as possible, as the rotary encoder >is on the drive wheel I can only tolerate a small amount of slippage. >I have spent hours on the net trying to find the answer but don't seem >to have hit on the magic search terms, I am sure I have seen this done >with some sort of thread on the drive drum but might be dreaming it! > >regards > >Lee McLaren >-

part 1 2095 bytes content-type:text/plain; (decoded 7bit) {Quote hidden}> -----Original Message----- > From: piclist-bouncesKILLspammit.edu > Lee McLaren > Sent: 07 April 2005 12:32 > To: pic microcontroller discussion list > Subject: [OT] How do you wind a wire rope around a drive wheel more > than once and not have it travel up the wheel? > > > Hi, > > I am building a electric gate and are trying to use 4mm wire rope to > pull the 4m gate in and out, my first attempt was a failure as I > (mistakenly) thought that if I cut a groove in a pulley the right width > for the rope that the rope would pay in and out in the same spot. > I know how to get half a turn around the drive wheel by cutting a > parallel groove but would like to get three if possible so it > doesn't slip. > I am using a PIC and rotary encoder to know where the gate is so I can > accelerate and decelerate as quickly as possible, as the rotary encoder > is on the drive wheel I can only tolerate a small amount of slippage. > I have spent hours on the net trying to find the answer but don't seem > to have hit on the magic search terms, I am sure I have seen this done > with some sort of thread on the drive drum but might be dreaming it! I'm not saying you shouldn't do it this way (I quite like the idea of variable speed BTW, or at least soft start?), but if you do and you do get some slippage, then where your PIC thinks the gate is and where it really is might be different. What about when the power goes off half way through a run? All the comercial designs I've seen use either large micro switches or magnetic read switches for the end stops. And they usually use chains to transfer the drive power. As for the answer to the question, one way to do this is to use two sets of pulleys and wind the wire back and forth round both of them. You could manufacture the pullys by cutting parrallel grooves in a drum, instead of a thread. I've attached a quick sketch of what I mean, because reading this back myself, it doesn't make much sense!! Cheers, and good luck...Mike. part 2 3789 bytes content-type:image/jpeg; (decode) part 3 35 bytes content-type:text/plain; charset="us-ascii" (decoded 7bit)

I think this is normally done by using a threaded drum instead of a wheel so the windings on the cable can move axially while the drum turns. Another way to get more grip could be to use two, or ever three (driven) wheels in series and loop the cable through them (more or less like the gear-shifter in a racing bike) . With proper placement of the wheels you should be able to get 3/4 turn on each wheel. Ever consider using timing belt instead of wire rope? You can get that steel-reinforced and cut to any length. A lot more expensive though. Michiel On 07 apr 2005, at 13:31, Lee McLaren wrote: {Quote hidden}> Hi, > > I am building a electric gate and are trying to use 4mm wire rope to > pull the 4m gate in and out, my first attempt was a failure as I > (mistakenly) thought that if I cut a groove in a pulley the right > width for the rope that the rope would pay in and out in the same > spot. > I know how to get half a turn around the drive wheel by cutting a > parallel groove but would like to get three if possible so it doesn't > slip. > I am using a PIC and rotary encoder to know where the gate is so I can > accelerate and decelerate as quickly as possible, as the rotary > encoder is on the drive wheel I can only tolerate a small amount of > slippage. > I have spent hours on the net trying to find the answer but don't seem > to have hit on the magic search terms, I am sure I have seen this done > with some sort of thread on the drive drum but might be dreaming it!

You'll probably do better by using chain drive and sprockets (like motorcycle chain). Wire rope is very hard to work with, and if you pre-tension it it will simply wear faster. Chain & sprocket will work best. Just have it fall into an oil pan when the gate if opened. Yes, you were dreaming. --Bob Michiel Boerman wrote: {Quote hidden}> I think this is normally done by using a threaded drum instead of a > wheel so the windings on the cable can move axially while the drum turns. > > Another way to get more grip could be to use two, or ever three > (driven) wheels in series and loop the cable through them (more or > less like the gear-shifter in a racing bike) . With proper placement > of the wheels you should be able to get 3/4 turn on each wheel. > > Ever consider using timing belt instead of wire rope? You can get that > steel-reinforced and cut to any length. A lot more expensive though. > > Michiel > > > On 07 apr 2005, at 13:31, Lee McLaren wrote: > >> Hi, >> >> I am building a electric gate and are trying to use 4mm wire rope to >> pull the 4m gate in and out, my first attempt was a failure as I >> (mistakenly) thought that if I cut a groove in a pulley the right >> width for the rope that the rope would pay in and out in the same spot. >> I know how to get half a turn around the drive wheel by cutting a >> parallel groove but would like to get three if possible so it doesn't >> slip. >> I am using a PIC and rotary encoder to know where the gate is so I >> can accelerate and decelerate as quickly as possible, as the rotary >> encoder is on the drive wheel I can only tolerate a small amount of >> slippage. >> I have spent hours on the net trying to find the answer but don't >> seem to have hit on the magic search terms, I am sure I have seen >> this done with some sort of thread on the drive drum but might be >> dreaming it! > > -- Note: To protect our network, attachments must be sent to .....attachKILLspam.....engineer.cotse.net . 1-866-263-5745 USA/Canada http://beam.to/azengineer

> on the rope). The groove in the pully may actually need to be a sharpe V shape > two or three times as deep as the diameter of the rope. Not really. Have you ever looked at the drums used on garage doors? www.channel3000.com/exterior/1140134/detail.html photo14 link The groove is the diameter of the cable, round and the depth is half the cable thickness. They seem to work just fine in millions of installations. For the OP method to work, he needs to loop the cable back onto the drum, and have a stiff tension spring to prevent the cable from coming slack as the gate bounces along. Robert

On Thu, 7 Apr 2005, Lee McLaren wrote: > I am building a electric gate and are trying to use 4mm wire rope to pull the > 4m gate in and out, my first attempt was a failure as I (mistakenly) thought > that if I cut a groove in a pulley the right width for the rope that the rope > would pay in and out in the same spot. > I know how to get half a turn around the drive wheel by cutting a parallel > groove but would like to get three if possible so it doesn't slip. > I am using a PIC and rotary encoder to know where the gate is so I can > accelerate and decelerate as quickly as possible, as the rotary encoder is on > the drive wheel I can only tolerate a small amount of slippage. > I have spent hours on the net trying to find the answer but don't seem to > have hit on the magic search terms, I am sure I have seen this done with some > sort of thread on the drive drum but might be dreaming it! One way is to put a spring made of wire of the same diameter as the cable on the drum and spot weld it in place. The other is to allow the other end of the wire to pay off into a receiver under some (weak) tension. The latter method will cause the drum to always have 3 turns on it. These will stay where they are after the device stabilises (look at marine winches for clues). Peter

> -----Original Message----- > From: EraseMEpiclist-bouncesspam_OUTTakeThisOuTmit.edu [piclist-bouncesspam_OUTmit.edu]On Behalf > Of Lee McLaren > Sent: Thursday, 7 April 2005 9:32 PM > To: pic microcontroller discussion list > Subject: [OT] How do you wind a wire rope around a drive wheel more > thanonce and not have it travel up the wheel? > > > Hi, > > I am building a electric gate and are trying to use 4mm wire rope to > pull the 4m gate in and out, my first attempt was a failure as I > (mistakenly) thought that if I cut a groove in a pulley the right width And now for something completely different... On the Australian TV show 'The New Inventors' last year, there was a hydraulic gate opener that used water pressure for power. Just hook up your garden hose. Worked well & was quiet. Used about 2 litres per open/close cycle, which ended up on the garden. Somewhere on http://www.abc.net.au. Won't be much detail though. Ha, here's a novel idea, a shower head with a radio powered by the flowing water. Hmm, water flow spins a magnet mounted in a pipe, with a coil wound around it. Even better, a PIC inside tells you (via piezo speaker, or better a LCD) how hot the water is, how long you've taken and how many litres used. ShowerNag Deluxe (TM). That's dumb enough to work! Quick, to the patent office! Tony

Thanks, Lots of good ideas, I don't have room to put a couple of drive wheels so it looks like I will have to go chain drive of some sort, off to price bicycle chain. I don't want to use limit switches to stop the gate as I want it to open and close quickly and therefor want to accelerate and decelerate smoothly. The water idea is nice but the gate is 500m from the house and water is precious to us as we rely on rain water only. regards Lee McLaren