I have seen one of those engines powering a drill bit: Someone needed a hole drilled into concrete under water; and building a single use tool was their solution. Worked pretty well, too.
[deleted]
Fun, danger, and 70s airplane toys
51–60 of 190 posts
Re: Fun, danger, and 70s airplane toys
#52Earlier quoted context omitted.
Those helicopters were very difficult to fly, or so I've been told, as they were unstable. The modern electric copters cheat because they use a computer to stabilize them.
I was going to say. Helicopters are difficult to fly, period! It's not just those -- also the big ones.
Large helicopters are not as difficult to fly as small ones, simply because the time constant of their instability is longer. This is similar to how it is easier to balance a broom on the tip of your finger than a pencil, and a pencil is in turn easier than a toothpick.
Re: Fun, danger, and 70s airplane toys
#53Re: Fun, danger, and 70s airplane toys
#54Earlier quoted context omitted.
> but because I never could get the wheels aligned perfectly straight it would inevitably try to turn Hm. I don't think "wheels aligned perfectly straight" is the actual solution. I wonder if there's some simple mechanism by which it could be made directionally stable, in the sense of continuously adjusting itself to go forward instead of turn.
You need the center of drag to be behind the center of mass (think “feathers on an arrow” as the mental model). Free castering front wheels with fixed rear wheels that develop progressively more drag as the yaw increases will help, but you’ve got to get the mass forward as well.
Would castering rear wheels with mass (engine?) forward be simpler?
Re: Fun, danger, and 70s airplane toys
#55I had one of these as a kid! I could never get the "glow plug" engine to actually fire up, though, so I was never able to fly it. Sounds like I missed out on a spectacular crash.
glow plugs are pretty easy to start - stupid question, but you did have a big battery to power the plug?
The "glow plug" was kind of shaped like a spark plug, but instead of a gap for high voltage arcs, it had a small loop of platinum wire.
To start the engine, you had to pre-heat the plug. This entailed attaching a battery, clipping one terminal to the top of the glow plug and the other to the engine, to send a current through the platinum wire. You'd use a 'D' cell, or maybe one of those big old No.6 types. A mere 1.5V, but you needed enough current to heat that platinum wire.
This electrical apparatus had to be disconnected from the engine before you could fly the plane. Not sure if you could detach it before starting or not. That little wisp of wire would cool pretty darned fast with the current removed. I know with the larger RC planes the practice was to leave the glow plug heater attached until after the engine had started.
Anyway, once the fuel mixture hits that hot wire, there's this catalytic reaction where the fuel at the platinum surface burns extra hot. This imparts enough heat to the glow plug wire to keep it hot enough for the next stroke. Idk what magic keeps the fuel from detonating before the piston reaches top of stroke, but I can attest these engines are fussy little things. They didn't idle very well; throttle them down too much and they just conk out.
You can see other examples of this catalyzed combustion, and get a sense for what goes on inside the glow engine. These butane cigarette lighters that burn blue have a little bit of catalytic wire in them, you can often just see it glowing white hot just inside the flame opening. There also used to be these propane powered space heaters that had a gauze mesh of the stuff to boost the combustion efficiency.
Re: Fun, danger, and 70s airplane toys
#56Earlier quoted context omitted.
You need the center of drag to be behind the center of mass (think “feathers on an arrow” as the mental model). Free castering front wheels with fixed rear wheels that develop progressively more drag as the yaw increases will help, but you’ve got to get the mass forward as well.
Would castering rear wheels with mass (engine?) forward be simpler?
I think you want non-castering rear wheels, because you want the side forces to be generated when the vehicle is yawing with relation to the direction of travel. As the sled starts to spin, non-castering rear wheels will tend to oppose the spin. (If anything, you might even want to set the rear wheels fixed and slightly askew [toed-in] to increase the drag while traveling in a straight line [with near-zero yaw angle].)
Re: Fun, danger, and 70s airplane toys
#57Hey, I still have my Cox 049 engine somewhere. The airplane is gone, smashed up of course. I suppose it was dangerous by modern standards, but not at the time. About the worst it would do would cut your finger if it backfired when starting. Or you could use a cheater stick, or even an electric motor to start it. I once made a car for it out of piano wire. It would take off at high speed down the road, but because I n…
My biggest concern about modern toys is that we have dumbed them down to work for the lowest common denominator. That's why a 3 year old today can (with a bit of training) assemble 12+ LEGO sets. Back in the day, when I was playing with LEGO Mindstorms, I thought the fact that you compile binaries and flash them with a USB cable was a feature, because it gave you full control. There was even alternative OS choices li…
>My biggest concern about modern toys is that we have dumbed them down to work for the lowest common denominator. That's why a 3 year old today can (with a bit of training) assemble 12+ LEGO sets.
I think Lego is the perfect example of this. I never understood the point of it as a kid. Why would I want something that comes with an instruction booklet to recreate the exact thing shown on the box? Why wouldn't I just ask for the thing pre-made instead? And furthermore the bricks were useless for actually creating things. It's nothing more than a slightly more advanced wooden block set.
K'NEX on the other hand was awesome. You could actually build things. Erector too. And those came with all sorts of cool accessories like electric motors and solar panels that you could use to build crazy contraptions. Sad that those things aren't as popular anymore.
Re: Fun, danger, and 70s airplane toys
#58I had one!!
Was fun af, the engine was loud and always was messy (I was not able to refill it, only my dad)
Re: Fun, danger, and 70s airplane toys
#59Oh my. I got a then already very old Russian compression ignition engine like this [0] as a child. It needed a mix of petroleum, aether and rhizinus oil and was extremely hard to start. I did not have any spring or electrical starter and it took forever. Will never forget the sound and smell once it ran though. [0] https://en.m.wikipedia.org/wiki/Carbureted_compression_ignit...
I had to Google it, so just FWIW, that is usually called "castor oil" in English. :-)
Re: Fun, danger, and 70s airplane toys
#60Hey, I still have my Cox 049 engine somewhere. The airplane is gone, smashed up of course. I suppose it was dangerous by modern standards, but not at the time. About the worst it would do would cut your finger if it backfired when starting. Or you could use a cheater stick, or even an electric motor to start it. I once made a car for it out of piano wire. It would take off at high speed down the road, but because I n…
I don't know what toys you have, but my toys today are RC planes with a 25km range that transmit HD video so you can fly them with a first person view.
>>25km
Dragonlink, Crossfire, or something else?