Random slightly cool stuff you built but not worth its own thread, thread

[Lord Gruntfuttock]

I've been creating...

[Lord Gruntfuttock]

HANG IT IN THE LOUVRE... 

 

[rusty360]

Haha that's awesome!

[Lord Gruntfuttock]

Greatest scene in cinematic history...

[h4nd]

"test jig"

Parking this here for the Heli nerds to discuss, I don't wanna crap up the Aviation Thread:

Flat ALU strip, 2x 1.6mm x 20mm *1m, at 300fps, so 10 RPS, 300RPM, coming up on 30m/s at tip (target for test). Just at this moment, a big flutter started, which knocked down the RPM a bit. Thoughts on how to mitigate this please?

 

erk, linky, longer vid here https://photos.app.goo.gl/vmySqfgaV89jz37S9

[Alfashark]

Excessive flex - lack of a spar to give it rigidity. 

Balancing it properly will also help.  What's it for?

[Nominal]

How about tip weights, would that help?

[h4nd]

It's to simulate a pellet sower which does ~100km/h - 30m/s, and we need to see if video / ultrasonic will count pellets. Pellets are similar to 16x 8mm dowel.

@Nominal weights might be the go, could add mass to resist flutter, hopefully for minimal air resistance. I could experiment with them part way along. I should get slow mo of the rotor disc while it's doing it, I guess.

40kHz ultrasonic craps out at about 1/3 of the target rate. Hmm, I wonder if I can hotwire that sensor upward, LoL

[NickJ]

50 minutes ago, h4nd said:

It's to simulate a pellet sower which does ~100km/h - 30m/s, and we need to see if video / ultrasonic will count pellets. Pellets are similar to 16x 8mm dowel.

@Nominal weights might be the go, could add mass to resist flutter, hopefully for minimal air resistance. I could experiment with them part way along. I should get slow mo of the rotor disc while it's doing it, I guess.

40kHz ultrasonic craps out at about 1/3 of the target rate. Hmm, I wonder if I can hotwire that sensor upward, LoL

Your torsional stiffness isn't up to it, try wrapping some 3-4mm cord around to the tip to break up the flow, works on chimneys.

[datlow]

I feel like getting the holes in the centre is always going to be difficult and maybe adding to it

/ try balancing it as per a ceiling fan

https://www.thisoldhouse.com/fans/21019348/how-to-balance-a-ceiling-fan-and-blades

//VSD  and a 1/2 ish speed angle grinder

if my napkin maths is correct 5-6000 rpm  125mm grinder 

[mjrstar]

@h4nd Rigidity - Some 3mm wire braid attached top and bottom, loops made from cramps. then apply a bit of tension using some budget turn buckles.  you'd need a longer shaft and a top extension to give a bit of triangulation. Put the mounts in far enough back to take your tip measurement unobstructed. Probably a rigid lightweight disc at the blade root. Maybe 5mm aluminum plate 300 diameter would be a low cost worthy addition?

Then a smaller one top and bottom maybe 100mm.

 

/ can you put 4 blades on and 1/2 the speed and half the width, or does actual maths say otherwise. 

 

[BlownCorona]

torsional ridigty will be an issue aswell. theres no aerodynamic shape there so as the blade twists, various sections will provide differing amounts of lift in different directions, changing to round tube may help this.

[BlownCorona]

On 27/02/2025 at 19:13, h4nd said:

I should get slow mo of the rotor disc while it's doing it, I guess.

 

@NickJ got your new work toy put together yet? 2000FPS would highlight issues nicely

[NickJ]

11 hours ago, BlownCorona said:

@NickJ got your new work toy put together yet? 2000FPS would highlight issues nicely

Yep, all set up yesterday and promptly stolen by the test team.

Quite amazing how clear the video is when the lens hasn't been repeatedly run over by a dodge ram

[BlownCorona]

Hey! Its not my fault dodge rams have an insatiable hunger for cameras 
it sure isnt my fault anymore... 

[h4nd]

LoL, build some shit guys, don't just dish it out

(Adjudicator rules pics of carnage acceptable as a sub clause of "making a mess", if not already covered by the failures thread)

[h4nd]

Hey, will your cam do a 1h 240 fps run at 1080p? Want me to test it hanging off the bottom of a Helo for you?

[NickJ]

In our world, a failure is when nothing gets broken and when it does......

On the other hand, one of the test subjects arrived with a duster gun holster under the steering wheel, I have no idea why Americans would need compressed air while driving so I moved it to my lathe as the manufacturer intended.

[NickJ]

58 minutes ago, h4nd said:

Hey, will your cam do a 1h 240 fps run at 1080p? Want me to test it hanging off the bottom of a Helo for you?

Thats gopro territory, much easier to set up than full spec highspeed cam

[h4nd]

I did look, forum is full of "but it craps out after 15 minutes" stories. Interestingly, A34-5G seems to keep up (gets notably warm, tho)