Harbor freight air/hydraulic engine hoist conversion (flat bottom jack)

[chevyracer56]

Hey there, as with most people I like to save money where I can . Today's project consisted of modifying a $40 ( $32 with coupon) air/hydraulic flat bottom jack into the equivalent $80 jack for use on my engine hoist.

$80 jack
http://www.harborfreight.com/8-ton-l...ack-94562.html

$40 jack
http://www.harborfreight.com/8-ton-l...ack-95967.html

The only differences between these two, at least that matter to me, is the flat bottom one is not a direct bolt in for my HF engine hoist. So I decided to use my HF bandsaw, cut off the old flange and weld it onto the new jack. Keep in mind I was not terribly worried about perfect penetration since this part will remain in compression under a load.

Anyhow on to the pictures (forgive cell phone quality)

[redbeard]

Amazing that those tabs make it worth double the price.

I probably would have been scared to weld directly to the jack and fabbed up a whole plate to bolt to the bottom, especially since I am so fond of drilling.

[chevyracer56]

redbeard- I actually considered doing something very similar, but the main reason I went the route I did is because I got a 1 year warranty with it and the lady said even if I set it on fire I can bring it back and get a new one lol. Also the $40 ram allegedly will sit about 1/2" higher (than the $80 one) so I didnt want to raise it anymore then I needed to, although I doubt it would of had any negative effects.

[performance]

Those bases are often cast iron, and not cast steel. I hope it holds. If its cast iron, it won't.

[chevyracer56]

Performance, I actually had not considered that..........I did a quick grind test and I think you might be right on it being cast iron. When I put the grinder to the base of the HF jack it produced yellow/orangeish sparks but when I grinded on some home depot steel next to me I got a very similar color but just a lot more spark.........and from my quick research this seems consistent with the grind tests of cast iron vs. steel.

I suppose I should grind down the old welds and go back with a nickel N99 rod? Some posts mention stainless steel er308 works well also?

[performance]

I think you might use some non machineable cast rod, and it would be cheaper than N99.

But welding cast is tricky and not for the average welder, particularly in a serious structural situation like this, where something can be life or death. To weld properly, you'll literally have to set the thing on fire, getting it hot enough to destroy all the internal seals, and cook the oil into sludge...then cool it slowly over a long period of time.

[performance]

I think I'd rather weld some fabricated steel ears on a flat piece of plate, drill the plate, and tap holes in the bottom of the jack, and affix it with bolts.

[chevyracer56]

I decided to do a little destructive testing/comparison between er70s2 rod and er308L rod that I had laying around......it was quickly obvious that the 308L rod performed better on this cast iron.

Here is what I did, removed a cast part off of old HF jack and welded it to the old jack, then took a 3lb sledge hammer and struck it.

Test 1: ER70 rod, seemed to weld nice, looked decent, however upon striking it with the hammer the weld ripped in half and the piece went flying.......which is bad lol
Test 2: ER308L rod, seemed to weld nice, looked decent, 1st strike with the hammer flipped the jack around about 1 full revolution, 2nd strike formed hair line fracture outside of weld bead, 3rd strike broke the test piece however the weld remained intact...............I also decided to try and break off the weld by hitting it with the hammer....after about 10 hits as hard as I could and it not moving (but sending sparks) I decided it wasnt going anywhere.
(note this was done with zero pre/post heating)