Bridge crane end truck weight rating system.

Bill D · Oct 5, 2018

I looked and could not find the definitive answer about bridge crane end truck rating. If I have two end trucks rated for say 1000 pounds does that mean the maximum total weight, including beam and hoist gear is 1000 pounds or is it 2000 pounds.
Or is it 1000 pounds minus the trucks weight or maybe 2000 pounds minus the trucks weight.
Bil lD.

john.k · Oct 6, 2018

To rate the truck,you need to take half the weight of the crane beam(including that truck)...plus the entire lift capacity of the crane hoist plus crane hoist weight,assuming it comes over full travel on to either side....This will be slightly in excess then multiply by your safety factor........ OH bridge cranes have a habit of taking overloads.....My personal experience of OH cranes includes turning over fabrications that flip over and shock the crane ,and of coaxing a OH crane to lift way over max by using a forklift to get the weight elevated.So the code requirement of 4 x capacity structural strength is well warranted.......as you are likely wanting a powered truck,then acceleration and braking ,and speed need to be considered too.

adama · Oct 6, 2018

Bill D said:
I looked and could not find the definitive answer about bridge crane end truck rating. If I have two end trucks rated for say 1000 pounds does that mean the maximum total weight, including beam and hoist gear is 1000 pounds or is it 2000 pounds.
Or is it 1000 pounds minus the trucks weight or maybe 2000 pounds minus the trucks weight.
Bil lD.

Yep each component derates the next as it were when it comes to total lift. total maximum weight you can support with thoes is 2000lbs, thats beam and everything and importantly equally distributed, now do a lift at one end and you can not even lift 1000lbs, by the time you factor in bridge, beam hoist and its running gear your real world lift capacity is going to be in the 1/4 ton range. Thats not much at all.

m16ty · Oct 9, 2018

Theoretically, your capacity would be double the rating of the trucks, If the hoist point was in the center and was stationary. Where your load goes way up is when your hoist is moved to the end of the beam, closest to the truck. In that position, the truck closest to the load is going to be seeing the majority of the weight.

For all practical purposes, 1,000 Lb trucks equals 1,000 lb max load. You could actually divide the weight of the beam between the two trucks, but that weight will be so small (unless you have a really long span)that it really won't make a difference.

Mcgyver · Oct 9, 2018

john.k said:
.So the code requirement of 4 x capacity structural strength is well warranted......

Is the 4x fairly universal? As you point out its dynamic and there can be shock loads. We've been making some box girder cranes (have an 80 foot one on the floor now) but its not our engineering. I'm just curious what design rules are.

john.k · Oct 9, 2018

Where I worked the overhead cranes were antiques,looked like old railroad bridges repurposed.....the lift units had big open gears.......and the things survived incredible abuse......they used to shake the shed turning over big fabrications,and heavy plates.....the load would often tow the crane along the rails.....we employed imbeciles ,nincompoops ,dimwits,and lunatics........ever seen two cranes collide at full speed ,cause the morons thought if the loads could pass,the cranes would too.....The bridges had railway buffers on the frames to take these collisions.....Or lift a 15 ton boiler with a 10 ton rated crane...Get it started with a bit of help from a forklift......One was replaced with a modern one,looked like a toy,and was hopeless.....ended up parked up at the end of the rails,permanently.

m16ty · Oct 9, 2018

Mcgyver said:
Is the 4x fairly universal? As you point out its dynamic and there can be shock loads. We've been making some box girder cranes (have an 80 foot one on the floor now) but its not our engineering. I'm just curious what design rules are.

If you have a set of trucks with a certified rating on them, I would think that number already has the safety factor figured in. I don't know what the rating of overhead cranes is, but rigging safety factor is 5X in the USA.

m16ty · Oct 9, 2018

john.k said:
Where I worked the overhead cranes were antiques,looked like old railroad bridges repurposed.....the lift units had big open gears.......and the things survived incredible abuse......they used to shake the shed turning over big fabrications,and heavy plates.....the load would often tow the crane along the rails.....we employed imbeciles ,nincompoops ,dimwits,and lunatics........ever seen two cranes collide at full speed ,cause the morons thought if the loads could pass,the cranes would too.....The bridges had railway buffers on the frames to take these collisions.....Or lift a 15 ton boiler with a 10 ton rated crane...Get it started with a bit of help from a forklift......One was replaced with a modern one,looked like a toy,and was hopeless.....ended up parked up at the end of the rails,permanently.

A lot of that old stuff was ridiculously overbuilt. It's like that they didn't have the engineering knowledge to calculate what it would hold, so they just way overbuilt it to make sure they were covered. They also seemed to build with abuse in mind.

Nowadays, the standard practice is to build something as light as they can, and still meet the load requirements.

john.k · Oct 10, 2018

When the new Kone crane was put up on the rails,the foreman tried it out with the owner watching........Col(owner)....says "OK now put it into the fast working mode"....Foreman.."That is the fast mode"....Col ,to the Kone rep....WTF?...

Mcgyver · Oct 10, 2018

m16ty said:
If you have a set of trucks with a certified rating on them, I would think that number already has the safety factor figured in. I don't know what the rating of overhead cranes is, but rigging safety factor is 5X in the USA.

I was just curious the design approach with overhead cranes. We do lots of design build in other equipment but not of cranes, in that line we're the manufacturing partner. Drawings and commercials are supplied to us.

Crane company motto "we stand behind our cranes, but never under them"

homanfab · Oct 10, 2018

Mcgyver said:
I was just curious the design approach with overhead cranes. We do lots of design build in other equipment but not of cranes, in that line we're the manufacturing partner. Drawings and commercials are supplied to us.

Crane company motto "we stand behind our cranes, but never under them"

There are standards from ASME and probably ISO covering the design approach for overhead lifting devices. Application, number of cycles, and environment are used to determine the required safety factors. Certain components will have higher safety factors than others. I interned at a company that designed cranes but I was working in a different department so I didn't have too much exposure.

I did hear the story of a 60 ton crane that was designed but they forgot to include the weight of the paint in the design. Due to the size of the crane there was about 2000lbs of paint so they had to redesign part of the crane to meet the design requirements.

hobbyman · Oct 10, 2018

I worked in a small shop making end trucks in batches. What blew me away was the difference between their five ton and ten ton end trucks. Everything was identical except that they installed four 6000 series bearings on the heavier truck wheels instead of two. The selling price was almost double. Capitalism at its best :')
Final proof at install was a rated load was lifted mid span and a measuring tape hanging from the bridge was checked for deflection.
In my experience these type of cranes are idiot proofed by the hoist winch. The drum brake simply will not hold the load. You can lift over capacity by a fair amount but when you let go of the up button the load simply drifts down to the floor.

m16ty · Oct 10, 2018

We have supplied loads to load test cranes before. Every one I've ever done, they bypass the overload safety and pick 125% of rating. After that, they reset the overload to trip out at 100%, and call it a day.

On the older cranes, you can usually pick until the breaker kicks out (or the crane falls out of the sky). On any newer cranes, they have overload safeties set to not let them pick more than rated.

I don't know about that crane having 2,000 lb of paint, that's a lot of paint.

Bill D · Oct 10, 2018

that 2000 pounds of paint was probably lead paint.
By the end of WW2 the Allies did not paint their planes, to save weight, and they no longer needed camouflage from Nazi bombers.
Bil lD.

john.k · Oct 11, 2018

Does seem a lot....on a 60 ton crane.......We were industrial painters ,and some of the paint was very heavy.....like a 5 gal pail at 60 or 70 lb.......zinc paint is very heavy,and often sprayed as a Hi-Build coating in chemical environments.I know painting refinery tanks ,we would go through a truck load a day...8 tons.

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