Need input on attic lift fall arrestors

[SJMaye]

I am planning a build of one of the attic lift elevators using a hoist. Many on YouTube use a fall arrestor as a backup in the event the hoist fails. The thing I don't understand is the load rating on the fall arrestors. Most YouTubers show a single fall arrestor rated to hold no more than 310# when I feel confident the lift build materials, a human and whatever they are lifting to the attic weigh more than that.

Do I not understand the specs of these fall arrestors?

 

[PCustoms]

The thing I don't understand is the load rating on the fall arrestors. Most YouTubers show a single fall arrestor rated to hold no more than 310# when I feel confident the lift build materials, a human and whatever they are lifting to the attic weigh more than that.

Do I not understand the specs of these fall arrestors?

Fall arrestors are made to arrest the fall of a person. Not a homemade lift, a person and whatever they are lifting.

 

[fitter30]

Fall arrestor has to tied off to something else not the hoist. A retractable lanyard might work for like a roofer would use not for materials only you. The other problem would be its reaction time for lock up. Lanyard that takes to long you will hit the ground. Why would you want to ride with the load put a couple of tag lines on it to keep the load steady and straight.

 

[Spud McGee]

That may have something to do with the standard requiring that specific number. They are not building/testing/certifying them to handle 510lb, because the standard says self retracting fall arresters for people should be able to handle that 310lb. If I remember right, it was the locking mechanism that has to meet that 310lb, and has to lock up within 2ft of freefall.

You would probably have to look into a different line of products besides the ones built for the "stops people from falling".

There are some made for things that are not people. This one starts out at 660lb and goes to 11000lb. https://hysafe.com/product/load-fall-arrester-heavy-range/
These ones go up to 1100lb. https://hysafe.com/product/load-fall-arrester-light-range/

 

[SJMaye]

That may have something to do with the standard requiring that specific number. They are not building/testing/certifying them to handle 510lb, because the standard says self retracting fall arresters for people should be able to handle that 310lb. If I remember right, it was the locking mechanism that has to meet that 310lb, and has to lock up within 2ft of freefall.

You would probably have to look into a different line of products besides the ones built for the "stops people from falling".

There are some made for things that are not people. This one starts out at 660lb and goes to 11000lb. https://hysafe.com/product/load-fall-arrester-heavy-range/
These ones go up to 1100lb. https://hysafe.com/product/load-fall-arrester-light-range/

So, my suspicions are true? These guys are putting these self retracting lifelines on the lifts, but the weight of the loaded lift exceeds the rated weight? The specifications that confused me were

• Worker Weight Capacity: 130-310 lb.
• Average Arrest Force: 900 lb. (Max)
• Arrest Force: 1,800 lb. (Max)

What is the arrest force? The force put on the body when the device engages?

 

[cvairwerks]

The arrest force has to be greater than the force applied by the falling body being decelerated in 3.5' after a 6' fall. Typically a 6' lanyard will require about 19' from the anchor point to where you want to prevent falling impact. Retractable lines need about 15'.

Force is approximated as Body Weight x 4.5 "G" x 2 Safety factor. So a 200 lb worker, subjected to a max of 4.5 G's and a safety factor of two, has to potential to have an 1800 pound force applied to the anchor point. This for a person in a full body harness only. Any other type of harness or belt derates the fall distance and cuts the lanyard length significantly. When I climbed towers, we were only allowed a 2' lanyard while climbing and typically tied off with a 1' when working.

 

[PCustoms]

@SJMaye

Do you intend to hook the fall arrestor to the building, then to the lift in order to stop the lift if it (and it's load) falls due to winch failure?

 

[billconner]

This is made for heavy loads, not people, Aut-O-Loc 2 Backstop Safety Strap

Aut-O-Loc 2 Backstop Safety Strap - 503229 :: Draper, Inc.

www.draperinc.com

Breaking strength of 6000 pounds, so in the 1000 pound safe working load range. They are sometimes used on overhead stage rigging.

 

[SJMaye]

What I have been seeing on the youtube videos is the fall arrestor attached to the building and the bottom is attached to the carriage.

 

[Renegade1LI]

I am planning a build of one of the attic lift elevators using a hoist. Many on YouTube use a fall arrestor as a backup in the event the hoist fails. The thing I don't understand is the load rating on the fall arrestors. Most YouTubers show a single fall arrestor rated to hold no more than 310# when I feel confident the lift build materials, a human and whatever they are lifting to the attic weigh more than that.

Do I not understand the specs of these fall arrestors?

This is what osha requires

1910.140(c)(5)
Self-retracting lifelines and lanyards that automatically limit free fall distance to 2 feet (0.61 m) or less must have components capable of sustaining a minimum tensile load of 3,000 pounds (13.3 kN) applied to the device with the lifeline or lanyard in the fully extended position.
All anchor points must be rated to hold 5000llbs.

Not sure I’d use a personal arrest system for a material hoist, there are ratcheting ones that are better suited for hoists.

 

[Zeke]

I can't envision what kind of lift/hoist this is. You say there are videos? Can you link one?

 

[Spud McGee]

I can't envision what kind of lift/hoist this is. You say there are videos? Can you link one?

You can find them on youtube by searching "unistrut elevator".

 

[SJMaye]

That is one of the last ones I watched. It appears the fall arrestor he is using is one of the 3M Rebel models. I believe it is only rated at 310#. During the video there was all kinds of discussion about safety, but the load rating for the fall arrestor was never questioned. At least as I recall.

 

[Zeke]

Thank you. I like it. The builder mentions that the fall arrestor needed to be lowered so that the platform can reach the floor in the event of a failure. IDK why that's a concern. Stopping one foot off the floor should be fine. A commenter said that the fall arrestor should be on another structural member and I agree with that.

Pretty cool overall. I knew of a guy that built one of these and he had it on a screw drive. Man, was it slow. He may have converted a garage door opener, I don't remember. It wasn't for people as he had stairs as well. Just for boxes that are awkward to carry on stairs.

 

[Spud McGee]

Thank you. I like it. The builder mentions that the fall arrestor needed to be lowered so that the platform can reach the floor in the event of a failure. IDK why that's a concern. Stopping one foot off the floor should be fine.

I think the issue is the fall arrester would never let the lift reach the floor, ever. It was too short the way he had it mounted first.

 

[Zeke]

Dude, it was only 12" of chain....

 

[SJMaye]

Dude, it was only 12" of chain....

As I understand this model fall arrestor from the point of the beginning of the fall it will allow it to drop no more than 54" (likely much less from what I have seen demonstrated). My take is if the hoist cable snapped while you were 8' up you could drop no more than 54" and you would be 42" off the floor.

Is my understanding correct?

 

[Spud McGee]

As I understand this model fall arrestor from the point of the beginning of the fall it will allow it to drop no more than 54" (likely much less from what I have seen demonstrated). My take is if the hoist cable snapped while you were 8' up you could drop no more than 54" and you would be 42" off the floor.

Is my understanding correct?

The same standard that says fall arresters have to work for 310lb humans also says they have to stop the falling within 2ft. If the cable snapped while you were 8' in the air, you should be caught by the arrester at 6' or higher in the air. That standard does not apply to these other products we're linking that are made for heavy loads instead of people. So we don't know about those.

I think the initial issue in this guy's build is the length of his arrester was not quite long enough. Even at its full extension, it would not allow his lift to reach the floor during normal use. So he had to go back and lower the top of the arrester so it would let the lift go all the way down.

 

[Zeke]

^^^That was probably the issue. He didn't make that clear to me, but you have to be right.

 

[strutaeng]

I watched that YT video...

I gotta say, I've analyzed and designed Unistruts and it's pretty strong for what it is. But that seems outright sketchy to me!

From the platform (just held together with plywood and screws?!) to the connections into the existing structure, bending of the wall studs... yikes!

I can't comment on the question about the fall arrest. :-( Is the fall arrest for the user like in a harness as when using a boom lift?

Actually, I can't recall using Unistrut for anything carrying a person. Just used for lights, ducts, pipes, etc.