Sterling101
Owing to the fact that I've got a few "larger" planes in the hangar I wanted something that was a little easier to measure the CG with that wasn't awkward to store or potentially cause damage to the plane when measuring.

One of our club members has a CG Wizard set up which is just 3 scales connected to a central "puck" and you use your phone via an app to get the readings off it.  I liked the idea but not the cost so set about building my own system from some strain gauges and an Arduino Nano with a few extra bits thrown in for good measure.

The whole thing is based around the CoG measuring system that gets used on full size aircraft and is pretty well documented and even has a handy spreadsheet available too for calculating your balance point (I've attached it to this post).

The principle is you mark where your CG should be on the fuselage and then weight the left and right of the plane and either the tail or nose depending on the plane type.  Ideally using the undercarriage if you have some as it gives a good repeatable measurement point.  This will give you not only the total weight but the weight of each point of measurement.
You then measure the distance between the left/right scales (the reference line) and the mid scale to get the distance between them and using a bit of maths it gives you the point from the line between the left and right scales to where the plane is balancing.  From that you can then move weight around until you hit your desired mark.

I figured using a set square and measuring tape was a pain to get the balance point so I added a small laser pointer to my "puck" and use that to point against the CG mark then measure the distance to this from the reference line (for my big Cub it's 105mm back).  I then use the knob on the control panel I built to dial in the distance from the reference line to the mid scale (880mm to the rear on the Cub). Then just press the Calc button and it takes the measurements from each point and works out the distance from the reference line it's currently balancing at.

Simple system but very effective even on the smaller planes and very fool proof.  I think it could be properly handy for awkward shapes or bulky ones that you just can't measure with your finger tips or CG balancers.
It's also very handy to see if you have things axially balanced as I've put the readings from each of the scales on the screen.
Now the question will be, do I try and sell a few of these as I can produce them a lot cheaper than I've seen them commercially and now I've built one I know what tweaks are needed for a proper production version!

Fun times ahead maybe???

Here's a few pics of the set up in action any way 🙂

IMG_20190902_211159.jpg  IMG_20190902_211232.jpg  IMG_20190902_211310.jpg  IMG_20190902_211445.jpg 
Whoever said nothing is impossible had obviously never tried slamming a revolving door...
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Wildthing
Sterling101 wrote:
Owing to the fact that I've got a few "larger" planes in the hangar I wanted something that was a little easier to measure the CG with that wasn't awkward to store or potentially cause damage to the plane when measuring.

One of our club members has a CG Wizard set up which is just 3 scales connected to a central "puck" and you use your phone via an app to get the readings off it.  I liked the idea but not the cost so set about building my own system from some strain gauges and an Arduino Nano with a few extra bits thrown in for good measure.

The whole thing is based around the CoG measuring system that gets used on full size aircraft and is pretty well documented and even has a handy spreadsheet available too for calculating your balance point (I've attached it to this post).

The principle is you mark where your CG should be on the fuselage and then weight the left and right of the plane and either the tail or nose depending on the plane type.  Ideally using the undercarriage if you have some as it gives a good repeatable measurement point.  This will give you not only the total weight but the weight of each point of measurement.
You then measure the distance between the left/right scales (the reference line) and the mid scale to get the distance between them and using a bit of maths it gives you the point from the line between the left and right scales to where the plane is balancing.  From that you can then move weight around until you hit your desired mark.

I figured using a set square and measuring tape was a pain to get the balance point so I added a small laser pointer to my "puck" and use that to point against the CG mark then measure the distance to this from the reference line (for my big Cub it's 105mm back).  I then use the knob on the control panel I built to dial in the distance from the reference line to the mid scale (880mm to the rear on the Cub). Then just press the Calc button and it takes the measurements from each point and works out the distance from the reference line it's currently balancing at.

Simple system but very effective even on the smaller planes and very fool proof.  I think it could be properly handy for awkward shapes or bulky ones that you just can't measure with your finger tips or CG balancers.
It's also very handy to see if you have things axially balanced as I've put the readings from each of the scales on the screen.
Now the question will be, do I try and sell a few of these as I can produce them a lot cheaper than I've seen them commercially and now I've built one I know what tweaks are needed for a proper production version!

Fun times ahead maybe???

Here's a few pics of the set up in action any way 🙂

      


That hurts my brain, it's cool but I will stick to my tripods 🙂
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Sterling101
You know me and messing around though Jeff - I just can't keep my geek under control sometimes 😃
Whoever said nothing is impossible had obviously never tried slamming a revolving door...
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