DIY crankshaft balancing with an oscilloscope 10

[NDimitrov]

Hi all,
since I cannot find a local place to balance my crank I started to make a balancer stand using ADXL335 accelerometers and a QRD1114 looking at a reflective tape for triggering .
Finding the heavy spot using the acceleration plots is the easy bits .
I can't make the connection between acceleration and gr/cm imbalance .
Could somebody shed some light on that topic ?

Kind regards
Nikolai

 

[NDimitrov]

OK, a bit of a delay but here is some progress .

I got the halves to weigh equal (+/-0.2 g ).
I have the correction weights done as well .

The position sensor is a hall effect 0-360 degree 0-5v output sensor, in effect giving me an absolute encoder .

I'll get some play dough and do a dry run, this weekend, figuring out the light spots .

Cheers !

 

[Brian Malone]

Good luck with your tests. You have put a lot of effort into your motion system and the bobweights!

 

[enginesrus]

This is great, and excellent work. Maybe some detailed plans in the works? Others maybe interested in giving it a go as well.

 

[NDimitrov]

I'll cobble together a list and come back to you .
If I'm honest, I'd build it much simpler next time .

 

[NDimitrov]

So I cobbled together some build information for this balancer .
Hope it helps somebody .

 

[NotecA]

Good day !

Why did you decide to make a hall sensor and not, for example, a laser tachometer or an optical speed sensor?

I would make the struts shorter and the bands holding the support longer.

 

[NDimitrov]

Judging by your username it's no surprise you caught that right away. In fact there are two issues with my previous setup. One is the length of the arms, which in my second attempt is 150 mm (that gives a normal frequency of less than 7 Hz ). And the output of that adxl 335 is very noisy. The solution came from : Link . It uses Hscope app and is based on an esp32 which reads from two adxl345 sensors .
It worked like a charm . Only thing is you have to go by feel when it comes to how much to remove .
The whole setup is very easy to make with very basic tools .

Edit : The small accelerometer pcbs work just fine with a clear cot on them. I found no good reason to build a case around them.