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Newton's third law problem.
electrodacus:
--- Quote from: IanB on November 25, 2022, 01:57:18 am ---But the model does have constraints. It is constrained by an accurate representation of the system. What the model does, the real system does. And vice versa.
This is demonstrably not true. If I have a 10:1 lever, I can apply a force of 1 N on the longer end and get a force of 10 N at the shorter end. Gears are no different from levers. Even if the wind exerts a force of 1 N on the vehicle, we can use gearing to make the motor exert a force of 10 N at the wheels in the opposite direction.
--- End quote ---
This must be a record. I was not going to replay but there are parts that I want to help you with.
Your constraints are just geometrical. Not enough for physical simulation.
You can only get 10N out with 1N in if the body of the gearbox is not floating as it is for this example vehicle.
In the case where gearbox body is floating (not attached to anything) your output force can not be anything other than equal with input force.
Take a pair of scissors have it open it half way and glue some adhesive tape between the tip of the cutting blade on one side and at half the distance between the tip and the pivot point on the other side.
Now try and pull apart the two handles and see if you can have two different forces at the two handles
If you can prove that force is different at one of the handles I will be happy to admit I was wrong.
But I hope you do not even need to do the test to know you can not get a different force at one handle than on the other one.
electrodacus:
All usable gearboxes have 3 points of contact.
1) Input
2) Output
3) Body
If the body of the gearbox is not connected to anything as it is the case for all this vehicles then output force can not be different from input force.
If you have a vehicle you can imagine the gearbox body being disconnected from the vehicle body and if say it is also locked the force at the input will be exactly the same as on the output.
You can not have a usable gearbox with only input and output connected with the body floating. You always need 3 points for the gearbox to work.
So this is not a usable gearbox with just two points of contact in total.
fourfathom:
--- Quote from: electrodacus on November 25, 2022, 02:35:39 am ---All usable gearboxes have 3 points of contact.
--- End quote ---
1) Input : Ground
2) Output: Propeller / Air
3) Body: Chassis
IanB:
--- Quote from: electrodacus on November 25, 2022, 02:19:11 am ---This must be a record. I was not going to replay but there are parts that I want to help you with.
--- End quote ---
Then stop trying to help. You cannot be a successful student if you keep trying to teach instead of learning.
--- Quote ---Your constraints are just geometrical. Not enough for physical simulation.
--- End quote ---
I gave you the example of a pantograph. Look it up. It has only geometrical constraints.
--- Quote ---You can only get 10N out with 1N in if the body of the gearbox is not floating as it is for this example vehicle.
--- End quote ---
In the very previous post we had the point where it is not floating. It is sitting on the ground.
--- Quote ---In the case where gearbox body is floating (not attached to anything) your output force can not be anything other than equal with input force.
--- End quote ---
Then you need to enlarge your understanding of how gears work.
--- Quote ---Take a pair of scissors have it open it half way and glue some adhesive tape between the tip of the cutting blade on one side and at half the distance between the tip and the pivot point on the other side.
Now try and pull apart the two handles and see if you can have two different forces at the two handles
If you can prove that force is different at one of the handles I will be happy to admit I was wrong.
But I hope you do not even need to do the test to know you can not get a different force at one handle than on the other one.
--- End quote ---
Yes, this is exactly the example to think about. Suppose the force between the handles is 10 N. What is the force (tension) on the tape?
IanB:
--- Quote from: electrodacus on November 25, 2022, 02:35:39 am ---So this is not a usable gearbox with just two points of contact in total.
--- End quote ---
Having F1 equal to F2 is not relevant to how the vehicle will move. Forces are useful in static analysis problems. They do not help with kinematic problems like this one. The vehicle will move in accordance with how all the parts are connected. It is pure geometry. Unless you think the real world does not obey geometric constraints?
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