Gantry Crane Help

[jeff_canfora]

I have a service bed that I need to remove off of my truck, so the truck will be more useful by having a flatbed. After looking up some great functioning gantry cranes made out of wood, and one guy saying, “I know wood, so I used wood”, I thought as a welder… I know steel so I’ll use steel. However an inspector once told me, if you assume it makes an ass-out of-u-and-me. So after a few google searches I came across this forum and thought it best to consult with the experts.

First thing we all think before a lift is load to be lifted. I’ve researched this several times and I’m thinking 800-1,200lbs.
Dimensions: I’m going 10’ up with upper beam to be able to clear the bottom from the tires. The 10’ includes the ringing wire rope. I’d be going 120” wide to have 18” of side clearance, vertical to load clearance.
I will try to submit my sketch and picture of actual load.

I chose 1-1/2”x1-1/2”x1/8” angle because it’s cheap and this is a one or two lift operation. For the 10’ beam I put two legs back-to-back and stagger welded them together. 3” of 3/16” welds every 12”, then staggered on the other side. I’ll send a picture of that too. I was hoping that I’d be able to use the horizontal legs to use as trolly support if I ever wanted to use it for a load to be moved, rather than a simple vertical pull, as is intended for this service bed.

The vertical legs were going to be a single
1-1/2”x1-1/2”x1/8” 10’ tall going into a horizontal of same material with two braces on both sides and ends of same material (all welded connections) on 4” casters.

For the connection at the top corners I was going to weld square plate with holes onto beam, and make a bolted connection to the vertical legs for disassembly and storage purposes.

Am I on the right page so far or am I way off?
Do I have to have my safety factor of 5?
I will use a 1 ton hoist which will weigh 65lbs. Including the wire rope and hook.

As I am wrapping this up, I don’t see how to attach photos of things and I’m not sure if saving them as PDF’s would even do.

Thank you,
Jeff

[dvcochran]

1. I am not entirely sure I follow but a 10' length of 1-1/2" angle iron is going to have a good amount of flex. Also critical is the metal properties, A36 (hot rolled) versus something like 1018 (cold rolled). Below is a simple way to get a good idea of the strength properties. It should also help you figure out the necessary bracing to strengthen up the frame.
   Use a tape measure to find the depth and width of the angle iron bar, and the bar's total length (both angled sections). Take the force pushing or pulling on the angle iron and multiply it by 3 and the total length.
   
   Square the depth and multiply it by two times the width of the iron. Divide the answer from Step 1 by the answer from Step 2. The result will give you the ability of your angle iron to resist breaking its angle, in units of Newtons per square meter.
   
   
   

[dalecyr]

Jeff:
Are you still interested in doing this?
I have designed, fabricated, installed and currently use a few of these.

But first, have you checked out the gantry crane available from Harbor Freight?

If you just want to use one, that one might fit your needs.
And all you have to do is assemble it.

If you want to build one, I can help you go down the right path.