How to Read Articulating Crane Ratings
Articulating crane ratings are basically (Load) x (Distance)
Articulating cranes are rated based on the term ‘Load Moment’ which simply means “the load multiplied by the distance at which it is lifted from the center-line of the crane”. In the United States ‘Load Moment” is expressed in ‘lb.ft’ (foot pounds) like ‘torque’.
The vast majority of articulating crane manufacturers are based in Europe and so use the metric system. They express ‘Load Moment’ in ‘Ton.meters’, rather than ‘lb.ft’.
Converting Articulating Crane Ratings from ‘ton.meter’ to ‘lb.ft’ (foot pounds):
The European ton is 2240 lbs and the meter is 3.28 feet so 1 ton.meter is equal to 7,347 ft.lbs.
These manufacturers number their crane models to indicate the crane rating using Ton.meters. They do it in different ways, Palfinger might refer to a 32 ton.meter crane as a PK32000 and Hiab might refer to a 5 ton.meter crane as an 055 whereas IMT will call an 18 ton.meter crane an 18/129 which shows the rating in ft.lbs as well as ton.meters. The numbering systems are all somewhat different but the ton.meter rating is always included.
Frequently Asked Crane Rating Questions:
1) Is an 18 ton.meter the same as an 18 ton crane?
The answer is theoretically yes, but in practice, no. In theory an 18 ton.meter crane can lift 18 tons at 1 meter from the center of the crane rotation but in practice this doesn’t mean much because to load or unload a truck requires that the crane reach be in excess of 3.28 feet(1 meter). In practice, then, most crane manufacturers rate the maximum capacity at or around 6-7 feet. Some actually rate the cranes maximum capacity at 4-5 feet which in most cases means a 2nd hook point on the inner boom.
IMT typically rates the maximum capacity no closer than 2 meters or 6’6”. When comparing cranes the important number is the crane load moment rating as discussed above.
2) Where is the best place to mount an articulating crane? Behind the cab or at the end of the truck frame?
There are no hard and fast rules as to where the crane should be placed. It has to be said that the majority of cranes are mounted behind the cab and, where the crane is used for simply loading and unloading a truck of materials typically off the side of the truck the crane will typically mount behind the cab to maximize the payload as the crane weight will be borne primarily by the front axle. There are certain applications where the crane is typically, but not always, mounted on the rear of the truck frame such as for monument stone handling, poured wall form handling, heavy equipment repair and glass handling.
So it depends on various factors
· Truck design, cab forward or conventional
· Application, mostly side loading or rear loading
· Payload and axle ratings
Often, the application is probably the most important factor in determining which end the crane is mounted. Where the truck is used to back up to the unloading point, such as in monument applications where the truck is often forced to back up narrow lanes, having the crane on the rear greatly extends the useful reach of the crane compared with having the crane behind the cab. This does however put more load on the rear axle which might effect the payload capacity of the truck. In other applications where most loading is off the side rather than the rear the crane will usually be mounted behind the cab.