Mobile crane sizing.

[Smoothie1969]

Is there an effective utility for estimating the required size of a crane? I’m an estimator for a mechanical contractor, and it seems we never allow enough money for crane rental. And unfortunately, I don't have the time to call the rental company to give them specifics on each and every job I bid. How can I effectively adjust my estimates?

 

[Metalfixer]

I am not aware of an effective utility, but from experience, there are so many things to consider that time has to taken for the specifics on every job. I don't know if most of your work is indoors or outdoors, but weather conditions and ground surface have to be considered, also ceiling height. The weight of the objects, and angle of the lift, sometimes other buildings or machinery are in the way, and a larger crane is needed to safely lift and position your material. A call to the rental company, with the specifics, would be well worth the time.
Larry

 

[JStephen]

Try to get copies of the crane charts for the kinds of crane you use, and you won't need to call the rental company every time.

 

[Philrock]

Don't have the time...?

Check this out:

http://www.snopes.com/photos/accident/crane.asp

 

[Smoothie1969]

No, I don't have the time to wait for a quote for every bid. I need crane charts, pricing, destination charges, etc so I can ESTIMATE the COST myself. If we are awarded the project (~20% of the time), I will let the construction manager handle renting the equipment.

 

[nnjunger]

Your crane rental place should be able to give you a rate sheet for each crane in the fleet. If special setup or minimum fees apply to a crane, they should be able to give you these figures as well. Travel and setup you should be able to quickly estimate. If you are bidding the work, I am assuming you know the weights and heights for the lifts you are going to make. Some quick calculations should allow you to make reasonable estimates.

As far as not having the time, if you can't do it yourself, make the time to utilize your contractors. What is it costing you if you a) continue to miss estimates on the low side and lose money on projects or b) start over estimating the cost and lose projects because you are not competitive.

Those are just my thoughts, hope it helps.

 

[unclesyd]

I don't know where you are located but in our area there are two sizable crane rental companies that will gladly have some one sit in on a planning meeting or in case of a contractor sit in on a bid preparation. These, at least for us and several other industries have always done a very credible job in crane availability and controlling cost.

I've seen too many instances where cranes have caused delays and cost overruns due to very controllable factors. On the last large project that I was involved with the rental company had a representative at the morning project meeting at least twice a week. I never hear that we are waiting for the crane.

 

[mizzoueng]

Depends on what you are lifting, is it a uniform load or is it something odd shaped that will require a long boom? How far are you lifting it (or dropping)?

But I would say a good estimate for load calcs is 2.5x that heaviest thing you will see, ie. 5 ton chiller (weight), 13 ton crane, but i think they come is 5 and 10 ton increments.

Call your rental company and ask for a catalog. Also, do a search on google for crane sizing, I am sure there is something out there that would help in a pinch.