This is easy to explain to trainees.

The lift capacity of a forklift is determined with the mast vertical and the forks level. (Altering the tilt to forward will reduce your lift capacity because it alters the CF constant factor and LC load centre.....basic stuff, see below).

The formula for de-rating when either adding attachments or changes in load size variation is this:-

CF + LC x RC
____________
CF + NLC

CF = Constant Factor 'X' (Distance measured in mm from the front face of the forks/attachment to the centre of the front wheel/axle)

LC = Load Centre (Distance measured in mm from the front face of the forks/attachment to the centre of gravity of the load)

RC = Rated Capacity (Lift Trucks maximum rated lifting capacity in kg)

NLC = New Load Centre (The load centre in mm of the new load you are about to lift)

If trainees are simply shown a fancy powerpoint or lots of snazzy diagrams on the above then the average operator (and sadly instructor) is likely to fall asleep and never remember.

But essentially they are only dealing with '4' numbers in mm. How difficult is that?

Much easier and far more interactive to give them the formula as shown above on a prepared piece of paper. Give them a pen and a tape measure. Get them to determine what the basic measurements are for (CF,LC,RC,NLC). Surely they can all take 4 measurements?

Then using a mobile phone calculator (away from the batteries) they will come to a de-rated lift capacity.

A pen, a piece of paper, a tape measure and a mobile phone!

Easy and takes about 10 minutes if you have a slow bunch!

As always........if you don't know the weight of the load you are about to lift and the lifting capacity of your truck.......then you shouldn't be lifting it!!

Cheers

Jonah

To refigure the capacity, you take the known machine capacity x known load center and divide that by new load center. For example:
5,000# machine @ 24" load center. You want to know if your machine can handle a 3,000# load that is 72" long.
5000 times 24 divided by 36 (your new load center) = 3,333. Your machine can handle 3,333# @ 36" load center.

Thanks to all. Post closed

Thanks Normandy,

The explanation was spot on. much appreciated.

I did reply, Check your junk mail!

Thanks again

PaddyB

Email sent

If you have not received it maybe check your junk Mail

Rgds

Dan M
My post stated -
"Contact the supplier or dealer"

I fully understand in "most" cases that if an end user would attempt to contact the OEM they would be provided the name & contact information of the nearest servicing dealer. If there wasn't a local dealer within a 3 day crow fly - most manufactuers would help (I did when I was with 3 significant manufactuers).

And I am fully aware of many of those "rules of thumbs" after 41 years in the truck industry that folks use - that wouldn't hold water if something happened - at least in the courts on this side of the border. Have had to provide depositions a time or two.

The H40 with attachment I look after does indeed have a factory fitted data plate for the truck equipped with the attachment.

I've yet to see an operator look at a data plate on a forklift, if it lifts the load they just don't seem to care.

Not to mention, that on every truck with the lift mast is (should be) the capacity diagram, which shows very clearly what load, on what height, with what load center can be handled.
When the truck is equipeed with an attachment, the capacity plate should be replaced to the one which shows the reduced capacity parameters due to the attachment influence.

I've seen an operator argue with a manager before over picking up a load.

Manager insisted the 4 ton counter balance truck could pick the load up, the operator said NO it can't as the truck capacity is de-rated due to the double handling attachment fitted to it.

Operator logged of the truck & refused to pick the load up so the manager had a go.

Operator was proved completely correct as the manager attempted to lift the load & the back wheels started to lift of the floor.

Linde H40 - 394 de rated from factory to 2803kg @ 600mm load centre due to double handling attachment fitted.

john

with all due respect, I highly doubt that any supervisor or manager is going to bother calling the manufacturer to determine whether they can pick up a load or not, even tho what you say is correct. In the real workplace, they say 'pick it up. If the back end lifts, its too heavy.'

Altho I teach the 1"=100lbs method, it goes in one ear and out the other, but as I tell my students, 'I won't be there on Monday to babysit you'

Thanks Guys,
This is something that should really be taught in courses. I know most trainees are not interested. I don't think there is an operator out there that has not come across a situation that involves moving stock that is out of the ordinary. Ie 700 or 800 LC
Normandy, you are correct one too many "0's" My email is burnspatb at yahoo dot com dot au
Maybe we should all go back to the "curve" data plate?

Sorry - should have added this is simply a load moment calculation that calculates capacity without affecting stability.

If the load centre is excessive, other variables have to be considered such as fork section and strength. If the load centre is extra big, this may also have an effect on carriage bearings which has to be referred back to the OEM.

If it is you suggest, from 600mm to 700mm it should not be an issue

In response to the orginal question.....

Take the original machine rating and calculate the load moment including the 'x' dimension calculated from the centre of the wheel to front face of forks. So 3000 (700 + X dimension). This provides the load moment trying to lift the back wheels off the ground measured from the front axle.

Then, at the other end of the machine, take the unladen steer axle weight and multiply by the wheelbase. (This gives you a load moment of the counterbalance, measured from the centre of the front axle)

Now the rear load moment must be greater than the front load moment (or else you have a huge problem) however the ratio of one to the other is important and must be maintained at all times. (this is also known as the safety factor and is a good measure of machine stability)

Keeping that same safety ratio within the calculation, resubmit the front end-calculation inserting 700mm as the load centre but keeping the capacity as a variable (say 'L') instead of 3000. The new calculation will then put a figure against L and will retain the original safety factor.

Hope that helps

Fully understand that OSHA only applies to the US but would be willing to bet a dime or a 6 pence to a donut other countries have similar regulations.

Hi Paddy

You have either put in an extra 0 or left one out of your example.
this may confuse some answers.
Weight x distance = distance by Weight always
Of course Johnr_J is correct but he may be just over playing it a bit.
OSHA is not in Australia.
His old Inch-pound rating is still fairly accurate
Give me your email and I can send you these calculations without causing a riot.