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Comment by pageld | Hacker News Reader

It actually reminds me of those cable folding doors (http://www.bifold.com/note.php) which have been around for a while. They aren't usually used on garage doors though, more for airplane hangers and pole sheds.

I guess I'm not seeing the benefits for the extra complexity.

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Looks like it'd be a real pain in the ass to open when the motor fails.

Having worked in a warehouse building with massive roll-up doors that had electric motors I would imagine these doors have a backup that uses a reduction gear to make manual operation simple yet slow.

Not to mention maintainability.

I've been too lazy to grease/oil my powered "conventional" garage doors, either the lifting mechanism or the side rails, but they are still working after 15 years of use. I agree with your maintainability concern with this mechanism.

The springs of most conventional garage doors are a hazard to life (if you have a two-story bldg) and property. When the garage door is down, those suckers are cocked like a pistol with the weight of said door. And when one or more fails spontaneously, they will follow Newton's third law and shoot upwards into whatever or whomever happens to be there, with metal shrapnel going in either direction. I've had to repair a garage ceiling and replace all of those springs (once one spring goes, all of them should be changed.)

You are talking about extension springs? In my experiance torsion springs break very harmlessly. They just snap and unwind but stay on the shaft. Torsion springs are the only kind I have myself seen used for garage doors.

No, you had something entirely different so don't try to trivialize something you don't know anything about. Ours fired through the ceiling of the garage and gouged the underside of the roof sheeting because of how the door and springs was engineered. It went off like a slingshot and sent metal fragments upwards at high velocity. Also, they looked like they were from the early 1970's and the springs separated completely as a result of metal fatigue into 3 segments plus some other bits of shrapnel here and there.

> don't try to trivialize something you don't know anything about

I think you misread his comment. He wasn't talking about the same kind of spring you are.

Extensions springs are the old way. Common for a few decades at least. Torsion springs are the new way. They're safer, and smaller, and require less maintenance.

Unfortunately, they're also a bit more fragile. Speculation (mine) is that the metallurgy required to make a big torsion spring makes the material more brittle than standard spring steel. Or maybe they're just thinner and cheaper.

They sure are loud when they snap though.

Loud, yes. Extension springs are still found on single-piece doors.

Single piece doors aren't legal in many states, but interestingly it's not because of the safety issues (which are much greater than tracked folding doors with extension springs, due to the angle of extension).

I've never even seen them outside of California.

I was interested by this but couldn't find anything about single piece doors being illegal. Being from California I've lived in a few places where these types of doors are common.

> Single piece doors aren't legal in many states, ...

Sorry, I phrased that poorly.

There are many states where the typical California tilt-up single-piece door with levered extension springs does not meet code.

Apparently they are not secure in very high winds, so they're especially dangerous in hurricane/tornado country.

Ahhh that makes perfect sense. Thanks for the explanation.

Building codes require those springs to be retained by steel cables. Might vary by state. Cheap soln though.

If there were such a thing, it had fatigued and/or rusted to such a degree that it clearly failed to contain sufficiency energy because a ceiling tile had to be replaced and the ceiling above that had to be patched. (Cheap rental house with ancient crap.) Don't rely on safety properties as a first-line defense, they are a fail-safe, and sometimes they just don't work.

Building code changes usually aren't applied to existing structures. Retaining cables were not a requirement in the early days.

Sometimes code changes are applied at the time of sale -- either by law, by the buyer as a condition of sale, or by a lender as a condition of loan.

Pretty sure retaining cables fall into the first (by law) category, for the safety reasons you mention. It's definitely something that building inspectors look for.

But yeah, rental property is infrequently sold and almost never managed proactively.

California municipalities will come looking for property owners who fail to perform seismic retrofits, but I've never heard of anyone hunting down retaining cable scofflaws.

It's only when someone gets killed from something is anything done and then it's quickly forgotten back to the regular pattern.

Those doors would need a ton of space between the vehicle and the door though.

They fold outwards, and would require less room anywhere inside the garage, Han the op version.

I think he means a vehicle parked in front of the garage door.

Well, the video I saw at the link provided showed the doors opening inward. If they normally open outwards then it obviously wouldn't have any additional clearance requirement on the inside of the garage.

EDIT: I stand corrected. I went back and looked at the image (not video) I saw before. It was deceiving due to the layout but it was folding to the exterior. http://www.bifold.com/assets/slider-37.jpg

Some of these designed wouldn't work in places like San Francisco if you own a vehicle that just barely fits into said garage. The entire interior/exterior operating clearance would need to be available and measured carefully.

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