Introduction: Lego Pan Balance

Picture of Lego Pan Balance

How to build a balance with Lego, for weighing things.

Part needed:
Some basic Technic pieces
A few other basic Lego pieces
(optional) plastic containers

Step 1: Key Features

Picture of Key Features

For smooth operation the balance requires low-friction pivots. I hope the pictures show this well enough - I used the edge of a brick, balanced in the gap between two lugless pieces.

The pans for weighing / weights used to hold Canon B95 FAXPHONE inkjet cartridges. (Note that fax machine failed this week: it was a nasty, noisy, slow, weedy-plastic, cheap thing. While the old Brother Thermal-Fax is still working after at least 7 years. Having been disappointed with the Canon L160 in another office, "we" decided to replace the B95 with a Brother 1460 - so far pretty good.)

The pans are PP and lift in and out easily.

The pans are supported by hangers, resting on pivots as described above

The hangers rest on an arm, it's self resting on the same type of pivot on top of a tower.

Step 2: Central Tower

Picture of Central Tower

Pictures only - should be easy to follow or design your own.
The only critical component is the pivot base at the top.

Step 3: Hangers

Picture of Hangers

As in the previous step, pictures only - should be easy enough to follow.
The only critical component is the pivot at the top, the pans should be customised to suit your needs / bits.

Step 4: Main Arm

Picture of Main Arm

This beam carries the two hangers, and sits on the central tower.

Step 5: Final Assembly

Picture of Final Assembly

Combine the arm with the hangers, and add the grey pivot bases.
Mount the arm on the tower.
Hang one pan on the arm carefully, then the other.
If the balance is not perfect, adjust the weighting with small Lego bricks.

Step 6: Weights

Picture of Weights

For weights, coins can be good. Look up your currency on the internet, it's not that hard to find out what coins weigh.
I find that UK 2 pence coins weigh 7.13g or 7=~50g, UK 1 pence coins weigh 3.56g or 7=~25g. I've also collected some wheel-balancing weights, which are marked: 35, 30, 25, 20, 10g
Under load, 225g on each pan caused a bit of bending in the arm, but no functional problems. This is designed for weighing small quantities up to ~150g, but it's good for 200g.


gsda7fdasf (author)2012-05-01


35Timmy (author)2011-09-03

i like it

stephenniall (author)2009-08-15

haha i got a 20 year old Fax machine it uses thermal Paper and it great I bought it for £1 (abot $1.50) the guy didnt know a thing about it when i picked it up He gave me like 15 rolls of paper too

Derin (author)stephenniall2010-06-21

Not just old machines, newer fax-only machines (not copier-printer-fax) use the thermal paper too.

lemonie (author)stephenniall2009-08-16

You did well there, thermal rolls aren't cheap. L

stephenniall (author)lemonie2009-08-16

haha thats one of the reasons i bought it I cut up one of the rolls and Usewd it in a gameboy printer

RMConstruction (author)2009-08-21

Well what do ya know, Mister L has legos! lol, not intended to be offensive!

lemonie (author)RMConstruction2009-08-21

I've got some KNEX too, but never yet found anything to do with it... L

DJ Radio (author)lemonie2009-08-25

you could give it to me?

lemonie (author)DJ Radio2009-08-25

Well I don't think I'm ever going to do much with it. PM me your postal address, when I can find a Jiffy-bag I'll post it. L

DJ Radio (author)lemonie2009-08-25

you get my reply to your PM yet?

lemonie (author)DJ Radio2009-08-25

(Yes I did) 2nd PM sent to you Aug 25, 2009. 3:35 PM - but these things can be a bit slow...


DJ Radio (author)lemonie2009-08-26

Now I got it.

DJ Radio (author)lemonie2009-08-25

Ok, sure.

caitlinsdad (author)2009-08-15

You would have joined the immortals if you made this out of Knex.

DJ Radio (author)caitlinsdad2009-08-25

Too easy. Knex specializes in rods and connectors.

Bartboy (author)caitlinsdad2009-08-15

I made one a few months ago from knex.....

caitlinsdad (author)Bartboy2009-08-15

ah, but did you post?

Bartboy (author)caitlinsdad2009-08-15

No, but dsman did.

lemonie (author)Bartboy2009-08-16

I can't find it ? L

lemonie (author)Bartboy2009-08-16

Ah I was looking for an instructable ("and i am going to post it" Sep 19, 2008), thanks. Yes, the other one does look better. L

Immortals? cool I'm immortal!!!

Seems some people just can't kill knex.

Goodhart (author)caitlinsdad2009-08-16

it isn't a matter of killing, it is more like letting the dead RIP LOL

BobS (author)2009-08-15

I had to use an accurate balance in the field in Suriname. I used a small board balancing on 2 nails on another oiece of wood. 2 plastic cups were glued on the ends as cup holders (should not get wet or dirty). Measuring glasses were used to get the right amount of distilled water in one cup-1cc=1g. I used it for weighing soil samples.

lemonie (author)BobS2009-08-16

I see, simple. Top-heavy though? L

BobS (author)lemonie2009-08-24

If you look real well at the photo, you can see small (ice cream-) containers halfway under the board at both sides. These are to prevent the balance from tipping too far. The accuracy was about 2 drops of water... (convert that to SI)!

lemonie (author)BobS2009-08-24

Yes I saw the containers and a assumed correctly. 2 drops is good, what do you reckon 10mg per drop? L

lemonie (author)2009-08-18

I've added another step, you'd probably want to stop at 250g per pan. L

the_burrito_master (author)2009-08-15

pretty cool although a needle at the top would be a good idea. Maybe even a scale.

About This Instructable




Bio: I'm an experimentalist, a scientist and I have a tendency to do things just for the sake of doing them, or to find out ... More »
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