Weighing something you cannot lift

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ruffrecords

Well-known member
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Nov 10, 2006
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Location
Norfolk - UK
I am about to ship a fairly heavy mixer. It is too heavy for one person to lift but I need to weigh it to get a shipping quote. So I am wondering if there is a way to weigh it without lifting it all off the ground. And I don't have scales I can get it on.

What I have in mind is lifting it from one end and measuring the force required with a spring weigh gauge. The I repeat the process from the opposite end of the mixer (because the centre of mass is not in the centre of the mixer).

So I have two force measurements from which I need to work out the overall total weight. I did some algebra by taking moments about each fulcrum and solving as simultaneous equations. After some manipulation and cancelling out I came up with the result that the weight is just the sum of the two measured forces.

It is about 50 years since I was taught applied maths so I hope I got the right answer. I can show my working if required but this result 'feels'  right.

Comments?

Cheers

Ian
 
Most shipments aren’t strictly by weight. It’s a combination of weight and  dimensions. There are usually weight and dimension classes for shipping. If you contact the shipper they may be able to give you a range that you know  the mixer fits in.
 
If you have a long enough lever, and fulcrum (like see-saw), and know what you weigh, you could estimate unknown weight by how far down the lever arm you need to stand to budge it.

OR not

JR
 
Weigh the modules and the frame separately , or get a second pair of hands in to help out. A luggage scales might be easy and cheap to find.
I had to lift a small cast iron stove recently , around 62.5 kg and I weight around 72kg , managed to get it out of the back of the car ok , once I had found the right way to hold it .  If you absolutely have to do it on your own how about some rope ,a couple of pulley blocks and a step ladder as an A frame .
 
Tubetec said:
Weigh the modules and the frame separately , or get a second pair of hands in to help out. A luggage scales might be easy and cheap to find.
I had to lift a small cast iron stove recently , around 62.5 kg and I weight around 72kg , managed to get it out of the back of the car ok , once I had found the right way to hold it .  If you absolutely have to do it on your own how about some rope ,a couple of pulley blocks and a step ladder as an A frame .

I don't have to move it on my own - my daughter will help with that. It is just weighing it that is the problem.

Cheers

Ian
 
You could hire  a crating company and have them take care of it. Problem solved.

I usually guesstimate  and wait for the bill. It’s easy for the shipping company to do. I’ve always told shipping companies that I can’t weigh a heavy piece . I give an estimate and that is usually close enough for them to do their thing.

Something like weigh a module. Multiply by number of channels. Add something for the frame and add 25%.

If you really want to weigh it you could do a pulley and a hoist with a counterweight. Seems like an awful lot of unnecessary work to me.
 
> the weight is just the sum of the two measured forces.

I *think*: only if the tilt is small or all the weight is at the bottom.

If the tilt is extreme or the weight is high, then you under-measure the total.

If you find a block of wood the same height as your scale, then the sum is valid.

Strictly the weigh-point should be close to the end, same on both sides, 2-point/line contact, which suggests two lengths of dowel/pipe to define the weight/counter points. However I doubt such fussiness is justified to get a Shipping Weight. As the USPO keeps reminding us, it IS what the carrier's scale says it is; you just want to know if it is nearer $100 or $200 (is it worth the cost?).
 

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