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Home built gantry cranes

RobinHood

Ultra Member
Premium Member
Is that a variable pitch prop? Are the light coloured areas that are supported by the “saw horses” the plain bearing journals?

You can also see how they have wooden dunnage to protect the shaft and increase friction to stop it from sliding if it were just steel on steel.
 

Janger

(John)
Administrator
Vendor
Is the pitch of the screw blades adjustable? While in operation? oops Rudy already asked this. I'll ask another. Do ships like this have bow thrusters?
 

CalgaryPT

Ultra Member
Vendor
Premium Member
Here is something for you guys about lifting things - stuff you don't see everyday

Dry Dock 2016: ...Pretty beefy saw horses eh!?
Always look forward to your updates Brent. If you ever need a stowaway who will make himself useful on board, I'm your man.
 

Brent H

Ultra Member
@Dabbler : have you or any one you know built an overhead crane verses the gantry style? The crane type where you can basically run an I beam back and forth across your shop ceiling with an electric hoist that can slide back and forth? I gather it would be more expensive depending on the span, but if you were going for perhaps 12 feet (say half a 24 x 24 foot garage) it might not be way out of the question. Thinking of that of the classic beam trolley down the middle.

I would say the beam trolley has a lot more limitations, but might be adequate in many uses. Your design lends itself to He-man portability which would also have many benefits .....

Just thinking of plans......
 

Dabbler

ersatz engineer
so... you ask at a good time. I'm building a 15' wide X 22' long bridge crane in my shop right now. The engineering is a bit tricky, but we can discuss some of the details here...

John N has built several bridge cranes and has more practical experience than I do. My cousin has been buiding bridge cranes for 45 years, and has helped me refine some of my lifting ideas. My Dad used to maintain the 200 and 400 ton bridge cranes at Stelco Hamilton, so I got a little info from him as well as I was growing up.

My design is using a 3X3X 3/16 wide flange aluminum I beam for all of the support members. I got the material for a steal from another member... The entire design stems from what capacity your trusses will hold at the rails. The rails must be perpendicular to the trusses, or you are in for a lot of restucturing. My trusses will hold 250 lbs on the bottom of the chord quite safely - we tested this with myself and my daughter on the same truss several times while insulating the ceiling. You have to determine what is safe for your situation.

If your requirement is only to lift that amount (such as in my case, 250lbs) then you need to then size your I beam accordingly. For a 250lb lift I'd make the rails out of 2X2X3/16 wide flange I beam. You have to use wide flange I beam for all structure, as the trusses aren't good at bracing the load at unexpected angles. A stiffer I beam will also help spread the load across I beams.

Next go to an I beam calculator and use the load and span to find out what I beam you need to support your design load. Here again you must use wide flange I beams. When a load is moving or seinging in a random direction the normal flange I beams will fail a far below the calculated load. Make sure that your bridge will support at least 2 - 2.5 times the max load.

Both rails need a novel mounting scheme, as they just cannot screw into the trusses, weakening their bottom chord, and risking pull out. I'm using a wooden beam above the trusses to further average out the load, but my lifting requirements are much higher than a single truss will tolerate.

I'm being cagey about the details here because doing this wrong or at loads that are too high can damage your trusses. Every truss system has weaknesses and I cannot generalize here. In the late 1970s I designed and implemented truss design software, so I can be sure that what I'm doing on my trusses will work. Depending on the number of chords (diagonal members) and design limits, your trusses might be stronger or weaker than mine. Note that stiffness does not mean strength. You can infer the strength of your trusses by measuring deflection under load, as long as that deflection is very small.

There are tests you can do to help you, but you should not deform the bottom chord of your truss by very much at all. This is because deflecting this puts tension stresses in your top chord connector plates that were designed for compression loads. At the place where your rails join to your trusses, you want a deflection less than .250 IF you are near the centre of the truss. Depending how how far you are from the wall, you will find this to be in the range of 200-400 lbsf. You should never exceed this value during any lift. NOTE THIS IS A VERY BROAD DESCRIPTION THAT CAN BE COMPROMISED BY A MEASUREMENT AT THE WRONG PLACE. iF YOU ARE WITHIN 24" OF A WALL THE .250 DEFLECTION IS NONESENSE. READER DISCRETION IS STRONGLY ADVISED.

This is just an overview of the 50 or so hours of design work I did for my bridge crane - but my gantry crane had as much or more design effort. I'm not trying to scare you here, but I'm trying to say that lifting equipment can be tricky, and it has to be thought through carefully - for safety's sake.
 
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Brent H

Ultra Member
Hmmmmm.....

I would be going the way of supports that would not be connected to the garage, but rather be self supporting -
issue 1 - I would think is the footing - but that would depend on load.

Something like this:

NOMAD-XW-1cellcr.jpg

Obviously a simple drawing but this type of set up would be more the tickle of my fancy- Like you could park in the garage and take out the engine if you wanted, or move things around a shop and maintain the work space.
 

Dabbler

ersatz engineer
There are commercial versions of your above design. The posts do not need reinforcing. Even 3X3X .100 square tubing can support over 1000 lbsf. What you are missing here is racking protection in both directions. The cheaper-but-good versions use cables in an X formation on the rails to prevent racking. The racking in the moving beam direction has to transfer the load to the concrete. This can be done by a 10 or 12" triangle and a concrete fastener (or equivalent) You can also gusset near the top to provide racking.

Racking protection should be able to withstand 10% of the rated load. Remember that if bracing for racking at the floor to keep in mind the moment arm of the crane.

I magine the heavy load moving so as to describe a cone with the lifting strap, and bracing for this. The diameter of the cone being 1/8 of the lifting height.

youtuber bobcloc02 installed a 20 ton bridge crane into his barn-shop. He is a structual engineer, so his experience is applicable.
 

Brent H

Ultra Member
Hey @Dabbler this was what was dropped off for me:

B6F6BC0F-CA7C-43F0-A0FB-1FAE8E369B3C.jpeg
One beam is 15 feet the other is 11 foot six. The web is 1/4” and the flanges 5/16”. They are 5-1/4 wide and 8-1/4 high. The other steel is a bonus I guess.
 
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