winch using 2-post lift as anchor point?

[Bill in MI]

Need to get a dead vehicle into my garage from a sandy, narrow alley where there's no straight shot in. Also short drive in front of garage has a decent incline.

Was thinking of putting a strap around one of my Bendpak 2-post posts and winching it in. Strap would be placed as close to the base as possible to keep the fulcrum as minimal as possible. 6 large bolts holding the post in 6+ inches of concrete seems plenty strong, but it wasn't designed with this application in mind either.

Anyone smarter than me know whether this is feasible and safe?

 

[Daedalus]

On the surface, sounds perfectly fine to me. If we're talking less than 1000 lbs of force to move the vehicle, I wouldn't give it a 2nd thought. You'll have almost zero bending; less than you would with a car on the lift with the CG off center. Some shear in the post that isn't a concern at all. Each anchor gives probably >1000 lbs of friction capability on its own. I would do it and just keep an eye on things to make sure nothing's flexing noticeably due to an unexpected weakness somewhere.

 

[bubinga]

On the surface, sounds perfectly fine to me. If we're talking less than 1000 lbs of force to move the vehicle, I wouldn't give it a 2nd thought. You'll have almost zero bending; less than you would with a car on the lift with the CG off center. Some shear in the post that isn't a concern at all. Each anchor gives probably >1000 lbs of friction capability on its own. I would do it and just keep an eye on things to make sure nothing's flexing noticeably due to an unexpected weakness somewhere.

Sounds good to me I think you'll be all right also.
Also after all it's not like you're winching a dead weight, the car is on wheels.

 

[ItsNemo]

I can't imagine that being a problem at all and wouldn't even think twice about doing it myself. If you're really worried strap around the bottom of both posts, chain to the middle, pull from the mid point....basically spread the load between the two posts.

Shear strength on some random Hilti wedge anchors that would be roughly sized for a lift is a few thousand pounds for one bolt.

 

[pmiranda]

If you have a small S hook handy to put between the winch and the strap you can be sure that you won't over-load the columns or bolts. The winch force should be minimal pulling a vehicle on wheels.

 

[CraigStu]

I'd do it in a heartbeat.

 

[firebirdparts]

yeah, they're very strong.

 

[HPRifleman]

On the surface, sounds perfectly fine to me. If we're talking less than 1000 lbs of force to move the vehicle, I wouldn't give it a 2nd thought. You'll have almost zero bending; less than you would with a car on the lift with the CG off center. Some shear in the post that isn't a concern at all. Each anchor gives probably >1000 lbs of friction capability on its own. I would do it and just keep an eye on things to make sure nothing's flexing noticeably due to an unexpected weakness somewhere.

I'm curious about this statement. Do you have a link to more data so I can do some research?

 

[Daedalus]

I'm curious about this statement. Do you have a link to more data so I can do some research?

Just round numbers in my head. 3/4" anchor torqued to 960 in-lbs. From Shigley with a nut factor of .2, preload = 960/(.2).75 = 6400 lbs. Assuming a .2 friction coefficient (just a guess), friction capability is .2 * 6400 = 1280 lbs. These are based on some assumptions but gives a decent enough ballpark to show there's no concern with the anchors.