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How to slow the closing of a rolling gate
2

How to slow the closing of a rolling gate

How to slow the closing of a rolling gate

(OP)
Some folks installed a rolling gate on a 7% grade. To open it, it rolls uphill. To close it, it rolls downhill.

The gate rolls along a 20' track between a brick house and the end-post of a fence along an alleyway. It rests against the fence end-post (6x6 pine) when closed, and against the house when all the way open. The track is anchored to a concrete driveway, and the gate is made of a 10' x 6' steel frame with cedar planks affixed to it. Needless to say; it is VERY heavy (300lbs?), hard to open, and very dangerous if left to close alone. If it were accidentally let go I imagine the impact would topple the end-post it rests against while closed, and end up in the alley.

I would like to minimize the damage done by the closing gate if let go. My idea is to slow the velocity of the gate -- but not sure what the best method is.

Some ideas are;

1. Counter weight - Fix an eye ring to the home, attach a rope to gate, run through ring and attach to some clock weights. Not sure if these will have enough slowing effect... and may allow the gate to be too easily opened? Could change with weather/rain?

2. A tension spring that works similarly to the above. Again, would it slow the gate in time?

3. A hydraulic fixture with a telescoping arm that when pulled on, will only pull out at a fixed, slow rate. This seems ideal but does anyone make them and what are they called?

Any suggestion are welcome!










RE: How to slow the closing of a rolling gate

I would think that even an air pot might be adequate. I could see maybe the cylinder ends affixed to the post end, and the plungers with a taper to aid in alignment affixed to the gate itself. Air is quite compressible, so that's a possibility.

Presumably, you're using some sort of chain drive. If that's geared, then the gearing itself can provide so level of slowing, but the wear and tear on the gear teeth might be excessive.

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RE: How to slow the closing of a rolling gate

Gravity is reliable. Use the counterweight system. Use pulleys rather than sliding the rope/chain through an eye to change the direction of motion. I'd use chain rather than rope. You might need to run the chain up and down over a series of pulleys to get the travel distance of the counterweight down to something reasonable, with extra weights.

RE: How to slow the closing of a rolling gate

It seems some sort of counterbalance weight would be the least amount of trouble. If done well, this would remove the gravity effects on the weight of the gate, wouldn't it? That would turn the problem into one of simply pushing & pulling a mass against friction.

To minimize effects of the mass of the gate whacking the post, one could attach an industrial damper on either element.

Then, of course, most any of these engineered solutions may be more expensive than redesigning the gate frame out of aluminum or composite material. Just a thought.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
www.bluetechnik.com

RE: How to slow the closing of a rolling gate

I guess that installing the gate level is not an option?

How about a gate opener?


RE: How to slow the closing of a rolling gate

I would suggest a cable & pulley mass balance system to reduce the amount of effort needed to open/close the gate. And maybe some sort of manually released passive braking system (like a spring-loaded foot that bears against the ground) to hold the gate in a given position if you stop pushing/pulling on it. The passive brake would be a good idea since a mechanical balance system may not always provide the exact counterforce needed to hold the gate in place. You'll also probably need to use some sort of compound pulley arrangement for the mass balance if you want to get 10' of cable travel in a 6' height.

Sounds like a fun engineering project if you have some free time on your hands. It's amazing how little energy it can take to operate an extremely heavy system that is well balanced.

Good luck to you.
Terry

RE: How to slow the closing of a rolling gate

(OP)
Great responses from you all!

The gate is not on a chain drive now -- and the budget won't allow.

It seems that the counterweight system is the way to go, with the addition of a damper for emergencies.

A series of pulleys (compound arrangement) is the way to go -- I'll need to research how to get 10' of cable to travel @ 3' in height. BrianPetersen -> What kind of chain is recommended for this? Does it run through geared pulleys?

I also love the idea of a passive brake -- although this would need to be non-locking so the gate can be operated from both sides.

Thanks again for the inspiration!

RE: How to slow the closing of a rolling gate

Any safety risk of the gate closing "too fast" on people or cars? Any safety/security risk of the gate closing too slowly?
At the chosen speed, can you accept the risk that the gate will squish a car or person standing in the way?

RE: How to slow the closing of a rolling gate

(OP)
racookpe1978 ->

There's a safety risk in the gate closing too fast. If someone is in the way or a car driving by at the time it smashes through the end post -- it won't be pretty. Not one for it closing too slowly.

I am having trouble devising a pulley system for the counterweight however. I'd like to get 10' of cable travel to @ 3-6' in height -- are there calculators for this?

Thannks

RE: How to slow the closing of a rolling gate

(OP)
berkshire,

Thanks for sharing that. Very understandable, fun, and practical -- excellent resource!

I'm still unclear re: mechanical advantage and travel distance. They say if the mechanical distance is 2, you'll need to haul in twice the amount of rope. So with a gun tackle rig (2:1) lifting an object 10' high, you would pull in 20' of rope. They did not say if doubles each time.

If I rig a luff tackle with a 3:1 mechanical advantage, will I need to haul in 30' of rope to lift the object 10'?

Also -- does anyone know of an affordable maker of quality pulleys? I'd like something that lasts outside for years to come... and really like Harken but simply can't afford them for this project && am weary of going with National hardware and others I see on amazon.

RE: How to slow the closing of a rolling gate

Quote (I'll need to research how to get 10' of cable to travel @ 3' in height.)


Fabricate a 10+ foot long pipe with pulley on top. Sink the pipe into the ground at the end of the rail. Attach a cable to gate, over the pulley, down the hole, and add sufficient lead weights for counterbalance.

(Simplified solution, but you should get the idea. If you have 10+ feet of depth available.)

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
www.bluetechnik.com

RE: How to slow the closing of a rolling gate

Galvanized or stainless steel wire rope and pulleys as used for overhead garage door.

If it's a 6 feet tall gate why are you constrained to 3 feet of height for your counterweight travel?

RE: How to slow the closing of a rolling gate

(OP)
Mint,

It'll be less than 6' due to height of weight, + height of attachment pulley at top of gate. I also imagined I'd be rigging to the center point of the gate rail (midway to the top).

Can you confirm I'll need to haul in 3' of rope to lift an object 1' when rigged with a 3:1 mechanical advantage system?

Thanks!

RE: How to slow the closing of a rolling gate

RE: How to slow the closing of a rolling gate

Briceburg,
Mint julep has done the heavy lifting for you in his last post.
So now work backwards. What is the travel of the gate, I think you said 10'-0" How you have the mechanical dis-advantage of getting the short vertical lift. did you say 3'-0" that gives you a ratio of 3.333 so now you say the gate weighs 300 Lbs that would mean your block W in mint julep's sketch would have to weigh 1000Lbs.
Now the thing that you are going to have to play around with is the friction in those blocks.
B.E.

You are judged not by what you know, but by what you can do.

RE: How to slow the closing of a rolling gate

err, the gate weighs 300lb, but it's only on a 7% slope therefore the load on the rope is a lot less than 300lbs. I agree you need to think about the friction in the pulleys and the track, but a half tonne weight is maybe a bit excessive...

Actually not too sure how it works at the moment, but would seem to be people powered, so can't need that much force to open / close safely unless they are training to be a line backer or a wrestler....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

RE: How to slow the closing of a rolling gate

If the guess of 300 pounds is correct then 7% grade gives you 21 pounds of grade force trying to close the gate.

I sketched a 1:4 mechanical disadvantage, so you are in the neighborhood of 90 pounds weight needed when rolling resistance and friction are considered, with a lift of 30 inches.

RE: How to slow the closing of a rolling gate

OOPS, I missed that one ,
Neglecting friction I get 36 LBs for the 7% grade with 120 LBs on the counterweight.
I used a metric calculator with the force on the gate being 161 Newtons.
B.E.

You are judged not by what you know, but by what you can do.

RE: How to slow the closing of a rolling gate

Granted that getting power to the gate opener could add expense, I think that a gate opener is not going to be that much more than buying all of the hardware and designing and fabricating the counterweight and components. Making this thing look like much more than a polished p.o.s. is going to be difficult. Also need to consider whether the gate opens with the counterweight or drifts shut with the counterweight. Operation in all weather conditions is also an issue. Plus,one still has to accelerate the counterweight and gate to get them moving. Recommendations for a counterweight would be to use a force gauge to decide on how much pull is required. Also use a steel box that can be filled with cement or steel punchings to get an accurate fill weight.

Regardless of how it is done there is more money and effort involved in making the gate close. Why not do the job right and level the gate?

RE: How to slow the closing of a rolling gate

Greg,
I have seen that system and totally forgot about it. If I remember right, the catenary effect of the chain increases the force on the gate as it gets closer to the closed position.
B.E.

You are judged not by what you know, but by what you can do.

RE: How to slow the closing of a rolling gate

Hello,

As far as damping the final travel of the gate to prevent banging, you might look at a door check like this:

http://www.dictator.nl/engels/fredo.htm?http://www...

They make the door checks for swinging doors as well as sliding doors.

Kyle

RE: How to slow the closing of a rolling gate

I can just imagine briceburg getting out of his car, pushing the 300lb gate uphill to open it, then getting back into his car to drive thru before the gate rolls back downhill closed. And even if he manages to squeeze past the gate without getting hit by it, he will catch heck from the Mrs. for the noise the gate made when it slammed into the side of the house.

And briceburg, it will do no good to try and blame the posters on this forum for any problems that may occur with your gate system.

RE: How to slow the closing of a rolling gate

If one of the gate's wheels could be fitted with a crank, the crank's motion, and hence the gate's motion, could be damped by an ordinary telescopic shock absorber, attached between the crank throw and a fixed anchor point on the gate.

Mike Halloran
Pembroke Pines, FL, USA

RE: How to slow the closing of a rolling gate

Use rotational spring rollers on the gate. As it closes, the springs get tighter, thus offering resistance. Will help the opening process as well.

RE: How to slow the closing of a rolling gate

Wrap spring brakes, which I think Ron is talking about, are kind of finicky for outdoor use.

Mike Halloran
Pembroke Pines, FL, USA

RE: How to slow the closing of a rolling gate

Mike...I agree, outdoors might be a challenge. I was thinking along the lines of a garage door spring (similar, but much less resistance), attached to roller axle. Could be covered and greased for protection.

RE: How to slow the closing of a rolling gate

Ron,
If you go that route, and I am not sure the OP will, Then a garage door wind up spring attached vertically to the wall of the house would work.
Put the cables one to the top of the gate and one to the bottom, and let the gate wind up the spring as it closes.
It may be possible to dispense with the top cable if the design of the garage counterbalance spring will allow it.
B.E.

You are judged not by what you know, but by what you can do.

RE: How to slow the closing of a rolling gate

Berkshire...that's a great idea! Could use existing garage door spring and axle setup.

RE: How to slow the closing of a rolling gate

A torsional garage door spring assembly would definitely provide close to the amount of travel needed, it has attachments at each end for connecting a cable, and it has provisions for setting the level of preload required. But these spring systems are usually something like 12ft long. Plus the system is designed for indoor use (the torsion spring is carbon steel) and must be protected from the weather.

It could definitely be made to work.

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