4 post lift runway deflection

[bstein]

I have been looking at The Bendpak HD 7W and the issue is that at a 92'' wheel base the unit is rated at 3500#. Well the application I have is for 5280 #. Bendpak has advised that I would need to move into a 14,000# unit.
Understanding the deflection of the runway and distance between columns is partly why I'm considering the short 7000# unit.
A 9XW based on the 92'' wheelbase is rated at 2250#......
Lifting equipment is probably tested at a 1.5 x the rating granted but thats where we would be using the 7W at the 5280#
Why do no other companies list a wheelbase issue, is BP just that pro active ?
Any and all comments welcome !

 

[mikegt4]

5280 # on a 92'' wheel base, what are you lifting?
It must be a compact tractor with a loader and filled tires.

 

[sublimate]

....

Why these strange specifications? Wheelbase @ Rated Capacity, Wheelbase @ 75% Capacity, Wheelbase @ 50% Capacity and Wheelbase @ 25% Capacity
We are simply COA – specmanship and legalese all combined into a simple formula. The specs we show are not based on ultimate failure - they are very liberal and safe working dimensions relative to runway length. We are extra cautious considering any strange vehicle configuration like airport tugs, forklifts etc. When we choose published lifting capacities based on wheelbase dimensions we also consider that same short vehicle raised on a set of two rolling jacks which would be worst case scenario. If others list dimensions that appear to be more favorable, I can assure you they are not built any stronger or more durable. They are just less concerned about anomaly considerations/situations like we are.

Hope this helps.

Jeff
BendPak

 

[Ray916MN]

The problems with all these specifications is they're implicitly based on weight distribution assumptions. Assuming the load from a 99" wheelbase is 50:50 distributed between the front and rear wheels is one type of loading, which is very different than assuming the load is for example 75:25 distributed.

The next issue is once you spec the load, you are also implicitly assuming the user will understand the implications of the load specification. For example if your runways are 120" long and you spec 5000lbs for a 90" wheelbase and your customer puts a vehicle on the lift with a 75:25 (3750:1250)distribution and parks the 1250lb end on the runways where the cross beam for one end is, you now have 3750lb on the runway 30" away from the crossbeam on the other end. This is significantly different loading than what you get if you assume the vehicle is parked equidistant from the lift ends (3750lb 15" and 1250lb 15" from each end)

Lastly, since the makers also sell bridge jacks and trays which can be fairly heavy and alter the weight distribution of a vehicle with respect to the lift, you need to be even more careful with what you tell your customers your lift is capable of handling and you may want to avoid the topic entirely. Some customer, someday may use a single bridgejack to lift an entire vehicle up, thereby making the effectively wheelbase the length of the bridgejack.....