Flywheel jig to test trapezoidal trajectory planner


#1

This is a question for maybe @Richard_Parsons or @Wetmelon

I want to test the trapezoidal trajectory planner recently implemented (Trapezoidal Trajectory Planner )
That would basically let me drop my own trajectory planner in python that basicaly forced to use a big PC instead of a small raspberry pi to feed the position commands fast enough on the USB link.

I love the testing jig that you guys used to test/stress the software here => https://youtu.be/8ZAALZAqtTo
It would also be super usefull as a “smoke test” to check some parameters or algorithm even before a given machine/solution has been designed.

I want to use on of those fitness weights I still have somewhere in my garage as an inertia constraint. (something that looks like this https://www.amazon.com/dp/B01CQLGB3A/ref=psdc_3408401_t1_B0041G3ZK6)

However, i’m concerned that making a PLA/ABS printed adapter could potentially makes the table vibrate a lot as RPM increases. indeed most likely the center of gravity may not be exactly at the center or rotation. And i’m basically a bit scared to create an accident having something that heavy spinning a bit fast in case something detaches… the resulting collision could easily create significant injury.

Except for good old common sense (dont spin too fast & stay away), would you have an advice about how to make it right while still mechanically torturing the system for validation purposes? (i have no lathe :/)

thanks


#2

Hi Alexisdal

I was lucky enough to salvage my flywheel off an industrial machine which meant it was already dynamically balanced.

I have seen someone try and use a weight plate as a fly wheel. See the video below.

Their conclusion was that the weight plates are of such low quality casting that they are full of voids and there is nothing concentric about them and so even with a lathe they will never make a good fly wheel.

My suggestion would be to look for something that has already dynamically balanced like an old car brake disc or similar.


#3

thanks for pointing that out

i’ll see if i can get my hands on a spare car wheel, or an old car/truck brake disc

how heavy is your flywheel?
(maybe i can cnc mill it in a thick delrin plastic piece?)