Befuddled about bearings, a couple of questions

[Bob Korves]

Kind of slow. Like human pulling slow. Holding a lathe being lowered down my (steeper than current code would ever allow) basement stairs. Four sheaves in a pair to get 7-8x mechanical advantage. Indoors. Not used in a marine environment. Human could be at the bottom of the stairwell, keeping the lathe on the track, so don't want any spindly eBay crap.

Keep in mind that while the mechanical advantage will be easier to pull, the cable will still carry the entire load throughout the entire length. Have adequate strength everywhere, including the anchor at one end and the attachment to the lathe at the other end.

 

[WobblyHand]

If you’re going downhill, isn’t friction good?

The right kind of friction is ok. Friction due to binding, wearing, heating or galling isn't. I am thinking of using this for other things someday. Pulling up, friction is not so good.

 

[WobblyHand]

Keep in mind that while the mechanical advantage will be easier to pull, the cable will still carry the entire load throughout the entire length. Have adequate strength everywhere, including the anchor at one end and the attachment to the lathe at the other end.

Yes. Was looking at 1/2" sheaves for 1/2" rope. Breaking strength is 3200 lbs. Working strength I believe is 880 lbs. Load is about 350 lbs. Was going to use a 6x6 across the doorway, but I will make sure that is strong enough. A section of I-beam would definitely work. Probably weld up a trolley out of angle iron, and bolt the lathe to the trolley. Will attach a big hook or ring to the trolley.

 

[Firstram]

A few wraps around a belaying pin would give you plenty of control to slide down a staircase. Not sure where the stairs are though, if facing the exterior you could use a vehicle as a deadman.

 

[Boswell]

I agree with Firstram. For only 350lb a controlled friction system would likely be enough for lowering.

 

[Asm109]

For your application ABEC 3 bearings are fine. For a grinder spindle you want better.
Rule of thumb for bearing mounting. The rotating ring of the bearing should be a press fit. Stationary ring can and should be a slip fit. Especially if the shaft and housing are different materials, you need some place for the differential expansion to take place.

 

[markba633csi]

I would probably choose a comealong for this also- they have a safety pawl to allow controlled feed-out, a bit at a time.
-Mark

 

[whitmore]

Yes. Was looking at 1/2" sheaves for 1/2" rope. Breaking strength is 3200 lbs. Working strength I believe is 880 lbs. Load is about 350 lbs.

If the weight is only 350 lbs, could you get it onto a hand truck with stair-capability? Those are rent-able,
and winching the truck (ratcheting steel cable winch) is straightforward.

 

[WobblyHand]

I would probably choose a comealong for this also- they have a safety pawl to allow controlled feed-out, a bit at a time.
-Mark

My come along doesn't seem to have a very controlled way to feed out, only on the feed in. If it worked ok on feed out, I'd be using it. Or maybe I don't really know how to use it. Found it at my Dad's place. Directions are long gone. For all I know, he got it used.

 

[matthewsx]

I bought one of these years ago and it’s my go to for lifting machines out of my pickup.

2,000 lb. 1-Ton Capacity 25 ft. Max Lift 10:1 Leverage Web Strap Puller Come Along Tool

But, for 350lbs a couple of strongish guys and a decent rope should be fine. Or, if you’re solo an electric winch will work well.

John