mechanical aptitude
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Willow, the fact that the three small wheels are teh same size allows it to keep moving. if one was a different size then it would lock up as it would be trying to move faster than teh others which wouldn't be possible. as it is each is trying to move in exactly teh same direction and speed so it 'works'
he he he, you'll do a better job than me westender
Hey, Cashman, between the 2 of us we got 96%. Maybe if we worked together we could
bugger it up completely.
Because all the internal gears are free to move laterally as well as rotating.
I can’t think of anywhere where such a configuration could be used though.
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Thanks Lilly but someone of my age and experience in mechanical and electrical engineering should have got 100%, it was that easy.Wow! Well done, Jambutty.
I chose suction too and I'm still convinced that is more right than their answer but I can see the logic of 'air pushing into a vacuum' but to my logic air is sucked into a vacuum.
If the outer rim didn't have cogs then I would agree with you Ian, but the cogs in the outer rim are locked into the cogs in those three small 'planetary' wheels which in turn are locked into the central 'sun'. In any series of gears if one of the cogwheels is held rigid then it prevents the movement of any wheel it interlocks with. So I still say they couldn't possibly move. Now if that outer rim was smooth then of course the three planetary wheels would slide effortlessly within it and their answer would apply, but the rim in the image is not smooth.
Cancel that! I've just had a rethink. I can now visualise them going on a wander within the outer wheel!
I've just had a rethink. I can now visualise them going on a wander within the outer wheel! 
agree with you on this , that was my thought (seized up gearbox)
You need to understand what suction is to see why they asked the question and why they gave the answer they did. Suction - Wikipedia, the free encyclopedia
If the piston didn't move their would be nowhere for the air to go. So we were right and they were not wuite so right.
The outer rim doesn’t have cogs – it is itself a cog and it is locked.
The sun may be fixed on its axis but the planets are free to move rotationally and laterally.
This explains the gears a little better willow. Look how the outer gear is part of the gearbox casing so is held stationary. the 3 inner gears are fastened on a common plate and to the output shaft.
Epicyclic gearing - Wikipedia, the free encyclopedia
Epicyclic gearing - Wikipedia, the free encyclopedia
If you have two containers of differing air pressure and they are connected the air pressure will equalize in both. Whether it is sucked in or pushed in is a moot point and dependant on whether you are in one container or the other. If you are in the low pressure container the air is being sucked in. If you are in the high pressure container the air is being pushed out and if it is being pushed out of one it can be said to be pushed into the other.
It’s a bit like when you mix hot and cold water. Does the hot water make the cold water warmer or does the cold water make the hot water cooler.
The bottom line is that it is the movement of the piston that creates a vacuum and this vacuum sucks in the air. If the piston did not move the air from outside would not push it down.
OK, I meant teeth, The teeth being interlocked with the other teeth.
I knew what I meant.Yes, I suddenly had a blinding flash in which I saw it differently, hence my follow up post saying 'ignore that'
I'm still on the side of suction though.
I too went suction mainly as Jambutty said, the initial action that caused the movement of air is the piston going down. hence as it instigated the whole proceeding I reckon suction is right. Atmospheric pressure was only equalling the pressure so it wasn't pushed in as all,it was dragged across. To me pushed infers that 'positive pressure' is in action.
Well Done Jambutty though!
The ones that made me think were the multiple pully ones.
You know the one where it showed you one pulley which was going clockwise and asked which others were going anti? I missed one of those off and I could kick myself because it was one of the ones right next to it!
It depends where you are. In the cylinder you have negative pressure relative to outside it, outside the engine you have positive pressure relative to inside it. The air will move from a high pressure area to a low pressure one. That is why the air is pushed in. It's still works the same way in a turbo charged car.
You would not say the air is sucked out of you tyre when you press the valve in. The air will move from the high pressure inside the tyre to the low pressure outside. The word suction is commonly used when pressures under 1 bar are involved.
In the end it comes down to using the scientifically correct words. As in a bulb is where daffodils come from whereas light comes from a lamp. It does not really matter which way you describe it. They put that question in to catch people out.
I was discussing this with my mate, an ex fireman. He said they were always taught that if you are pumping water from a pond, the pump does not suck the water out of the pond. Atmospheric pressure acting on the surface of the pond pushes the water into the low pressure area created in the pumps inlet pipe.
The input to a pump is commonly known as the suction side and the output is known as the pressure side. That's stupid English language for you.
Well I still reckon vacuum cleaners work by suction.