Thinking - Slightly interesting TV helicopter factoid

When I watch helicopters shooting at people on TV, it doesn't look very real. Why dont they just hover and shoot?

Why do they keep flying past really fast and taking a few shots, then letting the escaping car escape?

It turns out there's a good reason!

Well at least I think there is, and let's face it, that's good enough for me.

There's this thing called autorotation, and it's a very fine thing indeed. It seems that when your helicopter's motor dies on you in flight, it's not just a case of "plummet to the ground and hope you land in a used marshmallow dump" or something.

It turns out there's actually something you can do.

Which is odd, and a little surprising. And also kind of pleasant if you are in a helicopter with no motor.

Helicopter blades can change the angle they sit at when they are doing their rotating thing. They can make it so they create more or less lift as required, and they can also tilt forward or backward to create thrust so you can actually go somewhere, and not just hover impressively.

Personally I think hovering is impressive enough, but it turns out other people like to derive useful function from their helicopters.

So using some sticks and pedals and things inside the helicopter, your pilot (hopefully) can make your helicopter go where they (or you if you own enough money) want it to.

But when it's falling out of the sky, it turns out they can set the blades in such a way as to make them spin a lot using the substantial breeze that they find blowing through their blades when they plummet to the ground.

As I understand it, it's a bit like strapping a ceiling fan to the front your bike and riding around the block.

The fan, despite being disconnected from any power supply, starts spinning a lot.

Now, it turns out "spinning a lot" is just the kind of thing that you want from a helicopter's blades when you dont have a motor any more.

So if your motor dies on you, as long as you have enough forward momentum, OR altitude, you dont just fall from the sky. Your skilled pilot can do the ceiling fan on a bike thing for a bit, get the blades up to pace, then just at the last minute, turn all that handy rotating blade motion into lift and actually land without everyone's blood falling out.

Way cool.

I mention that the requirement is either forward momentum, or altitude, because that's true.

I like to say true stuff where I can.

If you dont have enough forward momentum to keep the blades spinning, you can trade some altitude by falling out of the sky for a bit and pulling up. This translates into forward momentum. So you need some altitude to do a bit of a dive to get some forward momentum, or just have some forward momentum to start with.

So...

I'm guessing the reason the TV helicopters dont just hover fifty feet off the ground and shoot at Jimmy Bond a lot is because it's a really stupid thing to do.

Who knew?

120ThingsIn20Years thinks TV might have actually got it right.









Aquaponics - Float Valve Mod

I installed a float valve on my aquaponics system because I grow a huge sphere of slime in there as free food for my Golden Comets.

I'm currently making a half hearted attempt at breeding them.

My Float valve looks exactly like this pictured to the left.



I bought it on eBay for two dollars I think.

It works pretty well but it doesn't put out a lot of water. I'm guessing it was designed to keep a dog bowl full or something, and for this it would be perfect. But I need a little extra flow.

Here it is in it's full "on" position.




And here in it's "off" position.

It does "off" pretty well, although I'm not overly fussed about it's "off" state. I dont really care if it leaks a little.

As you can see from the black pipe leading into it, there are some holes to make a spray to add a little aeration, but also to make sure there is never a situation where there is zero flow.



I only have a dozen or so adult goldfish in my system, and it is capable of holding a lot more.

 It could cope without any flow for a day or two, but the fish seem to enjoy their water moving around a bit.

The problem is that the slimeball I'm cultivating in the tank can sometimes find it's way into the outlet. The result is an overflow, and the sump tank running dry. The pump hates it when that happens, and I was lucky enough to catch it just before it ran dry a couple of days ago.

The point of the float valve was to slow the amount of water entering the fishtank if the water level gets too high. But because the flow through the device isn't very high, it isnt quite doing the task I assigned it.

I decided to make it flow a little faster.

To this end, I taped out the pin that holds it all together with a chopstick.


As expected, everything fell apart nicely, and I found that the thing worked by the float levering a small slide with a silicone stopper on the end. This blocked the water outlet when the float was
... floating

The bottom bit has the float on the end and fits into the box section on the next bit up. The lowest bit of green slimy plastic is the silicone stopper that presses against the next higher up bit of green slimy plastic.


I should write operating manuals.

The inlet hole did indeed turn out to be pretty small. Perhaps this is so the silicone stopper has a nice large surface area to stop leaks.

But I dont care about leaks because even when the slime blocks my system, it always lets some water through.

It never blocks it perfectly.




So I drilled it out to a size that should let more water through, but still allow the float to shut down the flow.

I had to do it by hand because the chuck on my drill has decided that it likes having the 13mm drill in it and refuses to surrender it no matter how I try to persuade the thing otherwise.

Thats what you get for running water all over the chuck when drilling stainless hinges and trying not to overheat the drill bit.

Somewhat surprisingly, the thing all fell back together as easily as it fell apart.

A few taps of the pin and it was all good.









So now the flow looks like this when it's in the "off" position.

Not a bad result.

Most of that flow is because I didnt bother to clean up the hole I drilled.

"Drilled" is probably a bit of a fantasy really.

Lets just say I made a hole with a drill bit.

In the "on" position I get a lot more flow now.

All in all I think this can be called a complete success.

And perhaps more importantly, it  shows that maybe I can still do stuff.

It's been a while.




If I care enough, I'll clean up the hole and make it so the flow actually stops when the float is floating.

Trying to drill by hand is fine until you actually make it through the thing your drilling. Then it becomes very difficult to make a clean hole because the drill bit just tries to screw itself into the item.

This is the "before" shot.






And this is the "after" shot.

The result is you get three quarters of a hole as you brake through the plastic.

I'll file it back to something like round if it turns out to matter.





So...

I did something.


120ThingsIn20Years Some of the photos were even in focus!







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