Engine hoist electric conversion - video

[Jon]

Engine hoist electric conversion. By Wood and Metal Shop Time. 33:25 video:

[BuffaloJohn]

Hmmm, this looks like a bad idea to me.

I look at the forces on the hoist. The column that tilts backward from the load is in compression. The main lifting force from the cylinder is counteracted by the pull down force of the straps (flat bar) that come from the top of the column to the frame base to the rear of the column base. That makes a triangle, with the straps being in tension (which also look like they are installed to the inside of the base beams and not to the outside - it may have been designed that way, but it would be stronger if they were to the outside).

The second triangle is the hydraulic cylinder pushing up on the lift arm, which connects to the top of the main column. The upward force of the cylinder is resisted by those straps on the main column (the first triangle).

So what happens when you put a force of the cable from the top of the column to the bottom where the tension straps are? The tension straps are no longer carrying the load and the cable becomes the tension member of the triangle, but because it is a moving joint, it is really only removing the tension straps from being something to strengthen the column to base triangle and the column does not resist side forces as well.

How to fix this? The winch needs to pull in the same plane as the main upright (leaning back) column, so then either the winch needs to be mounted at the base of the upright column with the cable being as close to parallel to the upright column or there needs to be another pulley to change the cable direction so that the cable is positioned properly. The more I think about it as I write, the more I think the winch needs to be fixed to the upright column near the base of the cylinder so that the tension triangle of the column and straps is maintained.

And while I am at it, remove the paint before you weld. Paint and primer interfere with the strength of the weld. If you are blowing out flames, you have a bad weld... And welding on plated metal is pretty bad for your lungs as well - zinc/chrome/etc. turn into some nasty gases which when you weld in an unventilated space, means you get to breath all that in - and they mess up the weld strength also...

Maybe I should just not watch some of these...