Building a Gantry Crane

Glen, I would say a 1 to 3 ratio. 3 on the tall leg. 1 on 1/2 of the total bottom leg.
 
iam planning on building a 2 ton gantry crane for my RR shop, similar to the one in the photos below. It won't be real tall, maybe 8'-9' to the top of the beam.

My big question is how long should the cross beams be, at the bottom, where the casters mount?

There's recommendations for straight ladders, that the rise:run should be 4:1 .
That would suggest a 4 foot base (two ft from center) for an 8' hoist, but shorter would work
too (because you have nonrotating joints, which the ladder doesn't). It would be useful, too, to know
exactly which doors the crane has to potentially navigate, and which pickup or flatbed trucks,
might have a heavy item in the bed, before defining the full sizes of the project.
With the right design, a short-topbeam gantry can slide one leg under the truck bed, so needn't
straddle the full width.

I can tell you from experience that a bookcase taller than 75" and/or wider than 24" will sometimes
have problems getting through a door, or up a stair, or down one. Also, pallets and lifting points are your
friends.
 
Just came back from picking up a couple of lengths of 6" x 6"x 5/16" A 992 structural I beam. More like H beam. No doubt waaay oversize for what I really need. However, with Craigslist you work with with you can get I guess.

Yep, the loco in the picture is an 18" gauge, 1/3rd scale true diesel at the non- profit Swanton Pacific Railroad, north of Santa Cruz, Ca. Way bigger than my small 12" ga stuff. The S&P RR is the permanent home now for the ex- Overfair steam locomotives that operated as people movers during the SF Exposition in 1914. Visited last spring to take some pics of the diesel for another train guy in Texas who wants to build in that scale. The Swanton Pacific is operated by a group of volunteers, funded by a perpetual trust set up by Al Smith of Orchard Supply fame back in the 70's. They have a mile of track and some nice shops on Mr. smiths old ranch, donated and operated by the University of California regents. The land trust says if the Regents don't maintain and operate the RR in good repair, they loose the 3000 acre ranch! Al was a Smart guy!! Here's a photo of two of their steam loco's. The bottom one just had a new boiler made up and installed. Stills needs the outer shell put back on. Lots of fun and very impressive if you like hobby railroading. Also, one reason their gantry and backshop equipment is so massive.

IMG_3024.JPG

IMG_3956.JPG

So regarding the gantry, It looks like the height to length of base ratio for these things is generally in the range of 2:1 to 4:1 depending on manufacture. So in line with what several have advised above. With the weight of these beams I just bought, Iam now also thinking weight aloft could easily affect this base measurement. These babies are heavy. I don't want to deal with an unnecessarily top heavy assembly. Anyway, it's off to the shop now to take some more measurements of equipment, then decide if I want to keep these monster beams or look for something smaller. I think I really need to stop jumping on these killer deals on Craigslist.

Thanks much for your suggestions and advice. Very helpful!

Glenn
 
Last edited:
Glen, if you have the room, the heavier beam just gives you some extra comfort knowing it won't be the cause of a buckle. So maybe you need to go a little wider on the supports to control the top heavieness, but better to have too much than not enough on a gantry.. Just my opinion.
 
Hopefully some steel design/fabricators will offer some advise here . Could not find the same measurements of your beams but did find a six inch high by 4 inch wide beam in my 6th edition Steel handbook and the uniform load published for that size on a 10 foot span is: Beam size 15#/foot =16.2 Kips; Beam size 12#/foot =11.6 Kips and Beam size 8.5#/foot = 7.4 kips with a Kip being 1000 pounds. If memory serves me right a point load should be 1/2 the uniform load. No doubt you are aware that a deeper web will yield greater strength for example a 10 X 4 beam with the following data: Beam size 15#/foot will hold 22.1 kips or 11000 pounds for concentrated load. Loss of 4 inches in height but gained 3000 pounds lifting capacity.
Lots of good advise given here, +1 on larger wheels.
Have a good day
Ray
 
A wide flange beam like this, 6 x 6 x 5/16, is not designed to for a trolley as used with a hoist. The angle of the wheels will not match up. Not to say you couldn't make a new set of rollers to match the flange angle which is probably less than one degree. As for loading, this will take a bit of calculating to get the results needed. Here's a link to one set of calculations that can be used. It's been a while since I've used any of these calcs since my line of work now doesn't involve beams.

http://www.engineeringtoolbox.com/beams-support-forces-d_1311.html

Also, the normal safety factor to use here is at least 4 or greater. This is based on material yield .5% offset, not ultimate yield.

Ken

Edit: There are a few things that can be done to a beam to strengthen it up a little if needed. Rather than do this, I would suggest getting a proper size beam instead.
 
Ray and Ken, thanks for the follow up and suggestions. The 6x6 beams (there are two pieces) are grade A992, rated at 65 kpi- so 65,000 lbs. it's often used in girders for bridge construction. Probably not mentioned in your book as it's a recent high strength material release meant to replace older structural steel compositions.

Ken, I've been looking into trolleys. A couple of 2 ton trolley manufacturers say their units will accommodate either flat flange or tapered. However, I plan on exploring farther to verify. Thanks for the heads up. Worst case these could be used as footers to add counterbalancing weight at the casters.

Last night, measured the equipment footprints for the four or five things I likely will need to lift. Now leaning toward a beam span of 7' or 8' rather than the more narrow 3' I first proposed. 6 1/2' clears the bed of my pickup. Also 6' clears the width of my old Farmal Cub tractor. I need to split the case on the old cub at some point and replace the rear main seal. So supporting both ends of the cub with two lifting points, positioned end to end would be a good solution.

However, a 3' to 4' beam span is ideal for all the rest of the equipment. The 4' extra feet width will sure make a difference storing this thing in my shop. The uprights for an 8' wide gantry soaks up a lot of high value space right around the edge of my work tables. Still debating. I need to get a sign that says "More thinking needed!"

Glenn
 
Last edited:
Glenn,

That's good that the beam has a rating of 65K psi, that's literally double that of A36 steel beams most of us use. What do you think would be maximum load you will be picking up with your gantry?
I'm not a license engineer, but I'll be glad to run some numbers for you if you like, if you don't want to mess with it yourself.

I didn't think about it, I believe there are a couple of guys that hang out here that are more qualified to run number than I am. Maybe they will chime in and offer help.

Ken
 
Thanks Ken, my max load shouldn't exceed 1800#. That is the weight of my Utilathe. Heaviest piece of equipment I own at present. I have on hand an existing 2 ton chain hoist, which I plan on mounting to the beam, once the frame is fabed up. So Iam shooting for 2 ton capacity overall. However doubt I will ever need to lift more than a ton.

I appreciate your offer to do some calcs on this. What kinds of results would show up from running some numbers, and what inputs should I provide?

Glenn
 
20161007_163642.jpg

I built this one a couple of years ago... the beam is 6x6x5/16 h beam supported on an A frame made of 2 inch box, 1/4 inch wall... I currently have a 2 trolleys on it, 1 with a 1 ton hoist and 1 with a 2 ton hoist.

It is 10 feet wide and 9 foot 10 inches tall, so it will barely squeeze under my 10 foot roll up doors on my shop.

I built it mainly for removing engines and such, so I figured it would never hsve to lift over 800 lbs or so... but then I bought a lathe...

I'm guessing the lathe weighed around 2000 lbs... the crane lifted it easily.

I need some heavier duty wheels to put on it... my current wheels are only rated at about 750 lbs for the set. I didn't even think about that until I had the lathe set down on the roller dollies... that could have been a bad mistake, but they handled the weight.

-Bear
 
Back
Top