Loop da Loop for my Rolling Ball Sculpture RBS4 EP 8
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- čas přidán 28. 05. 2022
- Designing, making and fitting a loop da loop to the mechanical kinetic art project - Rolling Ball Sculpture RBS4
Do I trust the maths?......
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I love that you show us the whole process of refinement.. even the initial 'fails'. Thank you for everything. So useful.
You are so welcome! Glad you enjoy it and thanks so much for the comment. 😁
It has to be a 200mm vertical height diff, which is not the same as the length along the track.
As you angle the 200mm long track further and further away from vertical, the height difference will go lower and lower.
The final track angle looks to be about 45 degrees, so your height diff is closer to 140mm; this is why your diameter had to be so much smaller.
Great maths. Thanks for the comments. Ian 🙏
I'm about to make my first loop and I am doing some research. I think, similar to a roller coaster, loops are not circular in shape. So I may try a clothoid loop, which resembles an inverted tear drop and allows for less intense G-forces throughout the element. The teardrop design makes it much easier to balance these forces.
Looks like you’ve thought this through. Good luck!!
The teardrop Form works very well. I managed a 10 times loop spiral with the japanese spacerail. In Addition you have to strengthen the loopholders in order to minimise the loss of kinetik energy into movement of the track. The next Option ist to bent the downhill track in a nice concave accelleration hill, because the ball gather turning Energy. There are lots of Experiments where you have to bet wich rolling track is the fastest.
When making the loop I think if you reduce the track width in the loop it will reduce friction caused as the forces on the balls try to spread the track as they take the loop. Also slightly cuts down on the helix require for the exit to miss the entry (Just a thought)
Thanks Neil. Good points.
Brilliant
Cheers, Thanks :)
I'm a retired aerospace engineer, and I spent a few years after I retired designing and building backyard roller coasters with my grandkids. I looked at a loop, and did the calculations in a spreadsheet. I made a video about loops and put it on my CZcams channel, but never made a loop, as the forces and accelerations were too high for my little grandkids. I documented all four of my backyard roller coasters in videos on my channel, and wrote two ebooks I'd be glad to gift you if you contact me.
You point out that your coaster, in practice, needed a lot higher hill than the physics equations predicted. I suspect that when the ball is in the loop and under high centripetal acceleration forces (a = v^2/r), they are high enough to spread the track rails and you get extra mechanical friction. You might try more cross ties so the track is stiffer and see if it goes faster?
Plus, aerodynamic drag goes up with velocity to the 3rd power, but it's a sphere so the air friction should be low. I believe that once you can characterize your ball drag on a track as a function of speed and accelerations, you could predict with some accuracy your performance before you build. I have a spreadsheet which does this, I'd be glad to share it. I think it is still available for free at backyardrollercoasters.org.
And a clothoid loop, with large radius at the run-in and run-out, and smaller radius at the top, will work better than a single radius loop. You need upwards force at the top of the loop, and a smaller radius will increase that centripetal force.
I just bought the equipment on on of your videos, and hope to get into this fascinating hobby. Thanks for the videos and instruction.
Hi Paul. Thanks for this. Looks and sounds fantastic. Please could you edit the link as I think it’s missing an “s”. Cheers Ian.
@@CopperGravity Thanks!
Fascinating! I tried making the same after watching your video with similar results. Are you twisting the track in a drill to straighten it out before bending it to create the loop? Or is your loop track not twisted? Do you think that twisting the track would impact the amount of friction? I’d like to re-try this without twisting the track but haven’t found the time.
Hi, I do twiat the track to straighten it. But then I also untwist it by approximately the same amount, ao it ends up straight and untwisted.
Thanks Paul.
I believe the problem of your calculation is, that you did not include the inertia and angular kinetic energy. As some of the initial potential energy will be stored in angular kinetic energy, the loop has to be smaller than what you would expect for an object, that is merely sliding in the loop. I might make the calculation later, as I also want to make a loop for a marble machine at some point. If I do, I will share the result with you for later reference :)
Thanks Erik.
@@CopperGravity Yes: It's because the ball is spinning down your track not sliding.
The physics calc is for a road - like a Hot Wheels track!
The narrower the track the less the ball spins relative to it's forward progress[ v ] , and absorbs Erik's angular kinetic energy less.
Thus the narrower the track - - the larger the loop can be - er - I think!
I think one thing that may alter your (probably not incorrect) math is the fact that the ball is not rolling on a planar surface - as I am sure that formula was calculated for. The slight lowering of the ball in the tracks will lower the initiation height a bit, and then you add to it whatever frictional losses from the rails are... (I wonder if that formula considers aerodynamic losses as well?) It might be interesting to see if a slightly larger diameter glass marble would do any better or worse. Since it weighs less it should deform the rail material less and roll a bit easier, as well as sitting higher on the track for a bit more speed.
Edit: Listening to the vid again, it sounds like friction was considered...
Thanks so much for taking the time to reply to this video with your very well considered thoughts. What I learned at the time was that real life results can vary drastically from paper calculations. I do love physics adventures!
Have you attempted a corkscrew type loop?
Hi, not yet. I think you need quite a tall sculpture for multiple loops.
Just a thought, would reducig the track width for this sectio help to reduce friction, allowing for a bigger loop/shorter run in?
Indeed, narrow tracks = faster ball speed. But also easier to fall off. It’s a hard hobby this!!
So exactly what terms do you search for when seeking formulas such as this? Got lots more questions, but what you're doing is pretty sweet! Can't wait to try my hand at one of these!
I think I just googled Loop da Loop maths formula. I watched about ten videos. They all said much of the same thing. So I decided to believe it 😝
@@CopperGravity I did notice that friction was not included in the formulae that you showed. Perhaps it is not negligible after all. The left-hand formula looked all right. I was having a bit of trouble following the right-hand one for the loop-de-loop forces though. I suspect that is the part that went awry.
Hello,
I was wondering about your math. Can it be so much off? Including the ball rotation energy into the equation does not change the drop height by magnitudes.
Is you track spacer doing something with the ball? I immagine to see the ball always stop when it reaches the track spacer.
3:50 and 4:58 drop of the ball right at the track spacer? coincidence?
I checked and the balls never contact the track spacers. So a coincidence I think. 🙃
which soldering tool do you use?
There is a link in the description.
What type of soldering iron do you use. Thanks
Hi, there is a video link in the description below. It’s resistance soldering.