Raising an engine lathe 5 or 6 inches

My back is in mediocre shape, and being moderately tall I have been raising many of the tools and benches in my shop to make them more
comfortable to work at. I would like to raise up my lathe about 5 to 6 inches, and have been thinking about how to do it. I'd really appreciate some advice on the best way.
The lathe is a Trens SN40, and it weighs around 4200 lbs. There are two pedestals: the one under the headstock is drilled at the base for 4 retaining bolts, and adjacent to each hole is a threaded hole with a leveling bolt in it. The pedestal at the tailstock end is drilled at the base for 2 retaining bolts, and 2 adjacent leveling bolts. Both pedestals are cast iron, and they both have an integral flange about 3 inches wide at the bottom contacting the floor.
The floor itself is a poured slab approximately 4 inches thick.
I have three alternative plans, and am hoping someone out there has a much better way:
1) I have some I-beam with a 1/2" thick web: I could cut 4 pieces and put two under the long edges of the headstock pedestal and two under the long edges of the tailstock pedestal. I'd bolt the lathe pedestals to the beam, and bolt (or bolt and grout) the beams to the concrete floor.
2) I also have some 5" square tubing with 1/2" wall. Cut and bolt essentially the same as the I-beams above. This would clearly be stiffer than the I-beam, but might make the lathe very loud since the tubing would act as resonators. I could pour concrete into the finished tubes, or fill them with that formadehyde-based expanding foam-in-a-can they sell at the Big Box.
3) I'm also considering cleaning and roughening the concrete under the pedestals, building 2 pedestal-sized forms, and pouring concrete 6 inches high. If anyone likes this plan, I'd appreciate advice on how far out from the pedestals to go with the concrete.
The design goals are: Safe, Rigid, and Quiet. OK, OK, "Cheap". :-)
Thanks for thinking about the problem; I'm really looking forward to hearing new ideas!
Dave
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For cheap, do to the concrete block yard and buy 4 of their 6" solid blocks (4 x 8 x 16) to try the height to see if you like it.
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On 7 Feb 2006 00:33:12 -0800, "LowEnergyParticle"
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I'm guessing that tube loaded with the 4200 lb. lathe isn't going to resonate that you could detect. If it does, you could always use the foam or bolt some rubber between the tubing and lathe base.
Pete Keillor
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Get a scrap piece of glue-lam left over from a building site, and just use it like a giant wooden shim under the whole thing?
I've done this with a Little Giant No. 25 power hammer, worked fine.
GWE
LowEnergyParticle wrote:

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I'm not quite sure why you would say that the tube is 'clearly' stiffer than than the I beam (assuming the 'I' beam has the same FLANGE width and thickness) From that standpoint, beam versus tube is a tossup. And to split hairs, is the 'I' beam a true 'I' shape with tapered flanges or is it a 'M' or 'W' shape with uniform flanges?
I think the biggest issue is getting things bolted down. Can you get at the needed bolts through the ends of the tube? But if you use the 'I' beam, will you be just bolting to one side of the flange? If so, I'd weld some vertical stiffeners running from flange to flange.
I don't really like the idea of narrow concrete pillars to support things. If you go that route, the concrete should be twice as wide as it is high, best is to do a 24" square on each end. The concrete needs to cure at least 30 days (60 is better)to get to reasonable strength before you add vibration loads to it. Use premium concrete (6000 psi)
You will also need to have some sort of adjusting bolts somewhere in the system to allow you to level the machine and avoid stresses in the bed.
LowEnergyParticle wrote:

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I raised a 4000 lb Chinese lathe (made for those shorter people, apparently) using 6-inch steel C-channel, welded into the box needed to support the periphery of the pedestal. We didn't bolt the thing to the floor, so made the box with the channel facing inside, but you could weld it up with the channel facing out, giving access to the flanges for bolting to the lathe and floor. Make sure you get rolled channel, not formed. Formed stuff is too light. Rolled channel has radii inside the angles and a sharp 90 degree on the outside. Rolled has radii in and out.
Dan
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safety is good, but...
30 day's cure for concrete before use? really?
with a decent re-bar prep, I'd think you could support that unit after 48 hours.
Our 5" spindle boring mill (more than 12 tons) was rolled across non-reinforced concrete in less than 48 hours.

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Normal concrete (without special additives) takes several days to get up to reasonable strength, normal cure time to get to spec strength is 28 days. A high strength (5000psi) mix would have only 15% of that at 48 hours. Worse than that, early loading on the concrete may produce tiny fractures that don't show imeddiately but it wall spall out later. For someone who just tosses some premix bags down on the floor with 1"x6" forms, let it set for a week or two minimum.
FWIW; I've seen a tandom dump truck sitting on it's rear axles after completely punching through 10" of reinforced paving that had poured 2 days previous. The pickup trucks were driving on it, the tandom tried to pull across.
http://www.cement.ca/cement.nsf/37693a7697922813852567b6006c2e36/87bd292932c91cff85256bdf0060ce77?OpenDocument
Jon Grimm wrote:

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OTOH, if you use "high early" cement, cover it and steam cure it, as is done in beam casting plants, you should achieve, IIRC, 70% strength in 16 hours. Gerry :-)} London, Canada
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You'll noitce I was careful to say "without special additives" and "normal" cure time. :) These are not likely to be available to the OP.
Gerald Miller wrote:

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Thanks very much for all the helpful responses! I've decided to bail out of the concrete solution, and go with the 5" square tubing with 1/2" walls. I really appreciate being told about the difficulties of the concrete cure; I was kind of leaning in that direction and would have gotten myself into a mess.
Thanks again!
Dave
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I raised my rockwell lathe up with concrete pads. I used 2x6 to build a box and place it under the lathe. I drilled a couple holes in the floor and stuck rebar into the holes so they would stick into the pad.
The lathe was hoisted over top of the forms and set down on blocks so it would be the right position. I put the bolts into the lathe mounting holes sticking into the forms. I mixed sackrete in a bucket and poured it into each form. Knock the forms off after the concrete sets. A bit of work but reasonably priced. I'm sure the pads will break up easy if I ever decide to more the machine.
As to size, don't bring the pad to far forward because you will kick it constantly. I think my pads are only about 1 foot wide and the depth of the machine. Nice place to tuck stock etc.
chuck
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    --Got a welder? Consider building a take-apart gantry. They're damn handy and once used and taken apart they take up very little room. I've made three in different sizes/capacities and it's made my one-man shop a whole lot safer, plus I can now move/lift things that would normally require several people with strong backs. Here's a link to a couple of photos of the biggest one: http://www.nmpproducts.com/gantry.htm
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"Steamboat Ed" Haas : Whatever happened
Hacking the Trailing Edge! : to Pasquale Gumbo?
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