? using a pull back ram to correct a weldment

Hi, I have a large weldment where I need to push two of its surfaces togather to get better bolt hole alignment. The surfaces are about
6" apart and need to be corrected by about 1/8". I have a porto power kit but not a pull back ram and was thinking of getting one. The problem is that I'm not sure how to use a pull back ram in this situation. The extended length of the new ram would be 28" and the compressed length is 22". There are chain hooks at both ends. Given that my surfaces are 6" apart, how would I rig things up?
--zeb
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Picture.
I suspect an I beam or a couple pieces of heavy channel, some blocking, chains, bolts etc and you could cantilever or lever some kind of rig to bend or flex your piece with a ram rather than a puller, but I think I would need to see your setup this morning to come up with an answer. My brain is not engaging this morning, and I can't picture your setup in my head from your description.
I did a couple quick block diagrams of the principles. I bet with your first hand knowledge of what you have you can find a safe way to apply the principles.
Pulling with a push ram.
http://www.yumabassman.com/images/metal/Ram%20To%20Pull.jpg
Pushing with a push ram.
http://www.yumabassman.com/images/metal/Ram%20To%20Push.jpg
Before beginning figure out exactly what you need to happen. Visualize the piece moving into that position. As you setup your rig picture how the forces will be applied and if it will do what you want.
Take your time. Figure out what you have. Exactly what you need. Use materials for your push pull lever that are sturdy and at least 10X stronger than the material you are flexing. Use solid blocking. Another steel I-Beam would be best. Strap or chain with something that has no stretch.
Position your pump so that you will not be in the path of anything that might fly out, break, or slip and fall. Where safety glasses. If something breaks it could fly in any direction.
Good Luck.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Wrong tool. First try a big C-clamp or bar clamp or big vise. If you need more oomph, make a frame that slips over that's big enough to use a hydraulic ram inside the frame to push one side into alignment with the other.
1/8" is a big error. You can also consider using a smaller bolt, or slicing the weldment, realigning the hole and rewelding it to fit better.
Grant
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That depends on what it is.
I have welded and filled air gaps upto 1/4" with my little el cheapo welder before I got my big fancy welder by swinging back and forth building up each side and then working inside the gap.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I might add. Ever put up an I-Beam steel building? Its routine to have to use aligning bars to force a lot more than an 1/8" to get the bolts in.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Aug 23, 9:51am, snipped-for-privacy@hotmail.com wrote:

Use big turnbuckles, or wrap a long rope around it several times and tighten like a tourniquet. Using multiple loops of rope puts less stress on the knot. The 2" webbing binders that WalMart sells can pull half a ton a few inches and it's easy to take up ALL the slack first by pulling on the free end of the strap.
Wrap a chain around everything and drive wedges under it. Lacking wedges you can put a crowbar under the chain with enough slack to get a block under one end, then pound the block toward the middle.
I bought a pull-back ram and only used it once, to proof-test a wire rope fitting. A ratchet load binder like this http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=5511 will do the same job for less money.
Jim Wilkins
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Aug 23, 9:51 am, snipped-for-privacy@hotmail.com wrote:

I would describe the problem part of the weldment thusly: The basic configuration is like a ladder with 3 rungs. All of the pieces are 3 x 3 x 1/4 angle. (Actually channel from the scrap yard cut to look almost like 3 x 3 x 1/4 angle.) The "ladder" is 3 feet tall and 6" wide. Before finish welding I had tacked bottom "rungs" to the 2 "rails" and bolted the top rung to the rails. After welding with 6010 I took the bolted top rung off and TWANG --lots of built of stress. Now I have to take a wood clamp and squeeze the two rails together before I can bolt the top rung on again --which works but is a PITA. This does not take much force. The problem is to move the steel enough to get it to yield.I like the load binder idea.
I don't remember the order of welds but I thought as long as everything was tacked and rigid I would not encounter this problem.
Maybe it's when I cut the channel: I cut the channel lengthwise with a plasma cutter and was surprised by all the internal stress that was released. If you sighted down the cut piece you could see the curl. I accounted for the distortion before tacking and everything seemed fine before welding.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
squeeze the two rails together

^^^^^^^^^^^^^^^^^^ You could bolt it up one last time, and then, with a big--big torch, heat the metal red hot in the right spot, and the stresses would relax. Prolly not in the cards, kuz it would need a BIG rosebud and lots of gas. So, instead, bolt it up, and then make a saw cut partly through one of the angle irons to let it bend and relax the stresses. Then Vee it out so you can weld back the angle iron from both sides, to balance the shrinkage, so you don't wind up right back where you were.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Aug 23, 7:45 pm, snipped-for-privacy@hotmail.com wrote:

I build up fairly precise machine parts by welding so distortion is a frequent problem. A small bead across one side of 1/2" plate will bend it. I just make them large and machine to size afterwards, and during the heating season I anneal them in the wood stove after hammering or pressing them back to shape.
You can straighten steel up to about the size you're using by catching one end in the low fork of a large tree and pulling on the other. Standing at the end you are in a good position to sight down it to see the bends. You can pull harder with a block and tackle but don't ever get downrange of it. It's a good idea to grind the sharp edges off first.
To bend only one flange of the angle, attach a crossbar to it that bears against the tree or hold it square with a big adjustable wrench as you pull.
I straightened the 3" channel iron for my bending brake with a scissors jack in the middle and chains at the ends connected to a heavier beam underneath. I had to bend the 40" long piece well over an inch to reach its yield point.
Measure the distance you move it when you push or pull, so you can increase the force in controlled steps and not overbend it.
Be careful. Bent steel stores a lot of spring force that can toss loose parts like a catapult if your jury-rigged pulling setup slips. That's why I suggested a direct pull with soft, lightweight rope or webbing instead of spacer blocks with the pull-back jack.
Jim Wilkins
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.