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weight scales - not certified

jeffw@sc47

Well Known Member
Description: Heavy Duty LCD Digital Floor Postal Parcel Platform Scales - 300KG/660lb 0.1KG

Found these scales on both Ebay ($42 - $47 ea +/-), and Amazon ($53 ea).

Two weighing modes: 1) Precision 150 kg/0.05 kg tolerance; 1) High Capacity 300 kg/0.1 kg tolerance.Most likely far east manufacturer.

Has anyone tried these? And comments?
 
I have not tried them but have been giving it serious thought lately since I will be needing a W/B on my -9A before I get it’s AW inspection. Many years ago when we completed the Cozy MKIV, we borrowed an old farm platform scale from a local EAA chapter. After fooling with it for a day we were not at all confident in its accuracy so we bought a set of InterComp racing scales and used those. BIG difference in W/B numbers. I sold the set when I was done with the W/B of my RV-10 and am now back in the market for a set.
 
Description: Heavy Duty LCD Digital Floor Postal Parcel Platform Scales - 300KG/660lb 0.1KG

Found these scales on both Ebay ($42 - $47 ea +/-), and Amazon ($53 ea).

Two weighing modes: 1) Precision 150 kg/0.05 kg tolerance; 1) High Capacity 300 kg/0.1 kg tolerance.Most likely far east manufacturer.

Has anyone tried these? And comments?

Do you have a link or a brand?

Many different kinds on those websites.

Thanks
 
romaja: check your PMs for ebay link for the ones I ordered.

There are a handful of similar model scales on ebay that vary a bit in price and capacity. I ordered the 330 lb / 660 lb model that varied a few dollars each - the one that I found was on sale for $42 ea. Other same models went as for around $46 to $48 ea; same type on Amazon for around $57 ea. I did talk to a local friend that had known someone hereabouts that had a good experience with buying some a couple of years ago.
 
Thanks Jeff,

Let us know how you like your new scales. I will most likely purchase the same product if you are happy with them.

Jim
 
Mixed reviews

Very tempting, but mixed reviews on Amazon. From accurate to an oz to off by 10 pounds.

When I did the initial W&B on my RV-4, I used 440 lbs flat glass bathroom scales. They are within a pound of each other. but of course no guarantee of accuracy.

Hard to use because you have to tap them to turn them on and they turn off after a few seconds.

Built 1" platforms and tailwheel platform so I could roll the plane on and off the scales. Unfortunately left wheel a bit more than 440 lbs so had to gang up two of them.

Another issue with accuracy appears to be weight location on the scales, looks like has to pretty centered on the scales.

I did maybe a dozen measurements to get consistent weights to within a pound.

Looking forward to your report on these.

Also would like ideas on how to check calibration. 50 US gallons of water is 416.44 lbs at 70F. But how do you get a 50 gal container (with accurate weight of the container)?

Finn
 
will report

I will report how the scales work out.

I plan to try them by weighing by few different bags of sand that I can weigh on a scale at a feed store for comparison.
 
I plan to try them by weighing by few different bags of sand that I can weigh on a scale at a feed store for comparison.

Why don't you just step on them and weigh yourself? It's not like your weight is going to change in the 10 seconds it takes to move from one to the next (Unless you're eating a sandwich while you're doing it?).

What does a bag of sand going to prove that your weight can't? Are those sand bag's weight certified and you're sure they didn't leak some out during their movements?
 
Why don't you just step on them and weigh yourself? It's not like your weight is going to change in the 10 seconds it takes to move from one to the next (Unless you're eating a sandwich while you're doing it?).

What does a bag of sand going to prove that your weight can't? Are those sand bag's weight certified and you're sure they didn't leak some out during their movements?

He can stack the known weights to get close to the weights of the wheel he will be weighing. They are cheap scales so they may be pretty accurate at 165#, but way off at 400#. If they are load cell scales, they may be pretty accurate, not so much with spring scales.
 
He can stack the known weights to get close to the weights of the wheel he will be weighing. They are cheap scales so they may be pretty accurate at 165#, but way off at 400#. If they are load cell scales, they may be pretty accurate, not so much with spring scales.

I wonder how he's going to get a 400 pound bag of sand on a real small scale like that.
 
55 gal drum

Seems a possible way to get a 450 lbs weight would be to fill a (plastic or steel) 55 gallon drum with water.

Problems with that are:
1) Getting the empty drum weighed. Use a fish scale or take it to a feed store?
2) Measuring the volume of water as you fill it. Using a 1/2 gallon kitchen measuring pitcher would make it real tedious and errors would add up.

Perhaps taking the scale(s) to a feed store and have them put a known 400 to 500 lbs weight on the scale?

Better ideas?

Would be nice if Van's would rent out scales just like Viking rents a prop balancer. But perhaps shipping wouldn't make it cost effective.

Finn
 
I have a couple of these scales. They are electronic. I tested them by weighing me on a trusted scale and then on them. I weight around 180. They seem to be accurate against the trusted scale and with each other. I suppose one could test them at a higher weight by using a couple of guys.
 
Or you could rest each wheel in turn on a plywood board resting on two analog bathroom scales. That gives you 600 lbs range for thirty bucks total. Shim the other two wheels to that same height to keep the plane horizontal throughout.

Of the two measurements, "Weight" and "Balance", the latter one is more critical by far. By using the same instrument to measure all three Weights you cancel out most of the systematic error on the measurement of Balance.
 
...By using the same instrument to measure all three Weights you cancel out most of the systematic error on the measurement of Balance.

True for the main wheels. But if scales are not linear the critical (for balance) tail wheel could be off. I used a fish scale and the bathroom scales in turn to weigh that. Still I realize that they could all be off because of possible non-linearity of the bathroom scales.

Really wish Van's would rent out calibrated scales.

Finn
 
I am tempted to buy just one for testing. If accurate, buy a couple more. I had to have my old Inter-Comp scales repaired and recalibrated. The repair was very reasonable but the shipping costs are almost prohibitive.
 
Scales

Jeff,

As you know, I live close to you. If you need to verify the scales at the higher weights, using a human subject, just give me another few months of covid lockdown and I can help you out.
 
True for the main wheels. But if scales are not linear the critical (for balance) tail wheel could be off. I used a fish scale and the bathroom scales in turn to weigh that. Still I realize that they could all be off because of possible non-linearity of the bathroom scales.

Really wish Van's would rent out calibrated scales.

Finn

A simple spring has very few means of achieving non-linearity near the middle of its range. :D One common one is to set the "zero" on the dial to a wrong offset. Digital load cells suffer the same problem, except you can't cancel it out with a knob but have to trust the electronics (it's why you have to wait a few seconds after you tap it to wake it up).

One way to reduce that particular source of error is to *add* a known weight to the tailwheel measurement (lead bricks), making the scales indicate the same total weight on all three points.

My point being, calibration of the scales is far less important than operator technique. The levelness of the surface (angle from horizontal) will usually trump any scale error, as the center of mass is a meter up on a 1.5-2 meter wheelbase. An inch of tilt can eat away ten per cent of the allowed C.G. range--any $9.99 dial scale can do better than that with tome TLC.
 
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