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  #1  
Old 03-14-2005, 01:57 PM
PopcornWelder PopcornWelder is offline
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Default Tubing Strength

I'm thinking of building a lifting table to use in my barn and was trying to decide what I should build it out of. I'm a computer geek by trade, so I'm a bit late in coming over to the dirty side. :-)

The two main items I'm looking to lift with this table is my Honda CB750K motorcycle and my lawn tractor. I'd prefer to build it out of scrounged materials, but I also don't want to build something that will immediately fail on me. I'm hoping someone can point me towards a listing showing the strengths of various size steel tubing. Also, if it isn't self evident, how to read the table. I'm gonna be looking to figure out how much weight how far away from the pivot point the tubing can reasonably support before crumpling, deforming, etc.

I know I've seen some members say "Oh, well that should hold X pounds without a problem", but I'd feel safer if I could get my thoughts in the right ballpark so I don't gain my experience the hard way.

Thanks,
Popcorn Welder
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  #2  
Old 03-14-2005, 02:00 PM
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Sberry Sberry is offline
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Quote:
I also don't want to build something that will immediately fail on me.
You dont want a lifting device to ever fail. You have any computer geeky drawings that would help? I am not a engineer by any means but I have seen a lot of thigs done by number crunchers fail (stuff from Sears are some great examples,, ha) Like a lot of guys here just from sheer experiece we can tell if it will work or not. I saw some gussets in a piece of log loading equipment fail a while back, no matter what the calculations said I would have added 50% due to the torsional stresses although I build lighter all the time in most cases. When we start out we are the masters of overkill.

Last edited by Sberry; 03-14-2005 at 02:10 PM.
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  #3  
Old 03-14-2005, 03:07 PM
PopcornWelder PopcornWelder is offline
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Default Diagrams

I haven't yet made any drawings/diagrams, although I do have a design in mind. I saw the SlagBilt Lifting Table (patent pending, all rights reserved, trademark used without permission) and decided that was the one that I wanted! (Well, as near a replica as I'm likely to build.)

Not having any materials yet makes it easy for me to change my plans. I think the thing I'm most worried about is the length of the tube bending when the weight is low, with most of the tubing horizontal.

PW
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  #4  
Old 03-14-2005, 03:18 PM
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moe1942 moe1942 is online now
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Use heavy gage C-channel steel cross braced for the lift mechanism.

Last edited by madam X; 02-27-2011 at 10:31 PM. Reason: remove hacker link
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  #5  
Old 03-14-2005, 03:51 PM
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SlagKing SlagKing is offline
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When I lift something heavy with my welding table, example a riding mower, smaller motorcycle, up to a 450 class. It's fine. Heavier bikes, which I have also build lifts for, require less lift then the welding table, and a third leg.
My world's famous welding table lifts to 50 inches, down to 3 inches. Riding mowers and such are an easy lift for the welding table. The frame, without the top is only 14 inches wide. Perfect for driving a riding mower onto.
The best part of the welding table is the ability to change it's height. With that ability, I can weld from different angles, accesses. I can use it with my drillpress on long stock. With it's 7 foot length, I can even lay on it, and roll it up to and over an engine compartment on a pickup, for example, changing the points on a chevy, instead of laying on a hot engine or leaning on the wiring and fan. I truely would be lost without it.
Within the last 6 months, I have added several things to the table, that I have posted on this forum, I won't post again those things in pictures but those things would include........
Vises that are loaded the same as a receiver hitch
Bench grinder.....loaded the same way
HF bender holes in the top, Scroll attachment included in this
Wings for clamping.
Various clamping points on the top. those would use the same holes and wings as above stated.
It all sits on a dolly I built which I can remove if I need more stablity.
That dolly much like a piano dolly, only longer.
If I can get it into my shop/garage, I can lift it and add stands along with the welding table if I need to.
My point, before my sidetrack is.....when I lift something heavy, and I don't think I would lift more then what I have already said I did, is that there is no bending of the lifting arms, or bowing. This is because of the design of the table to begin with.
It's not so much as a pressure lift, as it is more of a tension lift. The tension is along the top frame as it pulls the rear legs upright. The weight of this tension is applied in line with the leg, from it's top to it's base in a straight line, reguardless of the angle of leg or it's height. Nor does the front leg bend or bow, as I thought it would since the jack does apply it's force there.
Since it doesn't , I would have to say that the frame itself because the legs can't change distance from each other, reguardless of height or weight, that the legs do not bow or bend, because of transference of weight or tension to the frame.
I'm not an engineer so I'm sure there are true reasons for this non bowing, but since I'm not an engineer, could be why it works to begin with.
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  #6  
Old 03-15-2005, 12:23 AM
PopcornWelder PopcornWelder is offline
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Default Bending/Bowing

I'm just an amateur when it comes to physics, but I can't see where the design of the legs prevents bowing. I would think that the reason it isn't bowing is because the weight of the table and whatever is on top is less than the force required to bow the legs for the given weight. What size tubing did you use? Is it 2"x2", or is it smaller. I was thinking of using 2x4 tubing, but that will probably be overkill. Meanwhile I'm going to try and recall what my HS physics classes tried to drill into my skull about weights on the end of a bar with a suspension point, which I think would be the most similar to the pivot and lift design of the SlagKing Lift Table.

PW
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  #7  
Old 03-16-2005, 10:47 AM
PopcornWelder PopcornWelder is offline
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Default Tubing Size

Ok, by looking at the "Other" site, I noticed the post saying that the tubing was 1.5" square. So 2" might be better if I'm looking to lift a 750cc motorcycle, but 2x4 would be such overkill.

I'm still on the lookout for any specs for tubing related to shear or crumpling weights. If anyone knows, please share. I don't have the Machinery's Handbook, and I'm not sure if they have it, but if anyone does and can look, I'd appreciate it.

Thanks,
PW
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