When your beater lights up that right rear, here is who you can thank...

[Scott Colmer]

Went to the San Diego Museum of Natural History's Leonardo D Vincci exhibit and found this example of a rear differential designed to let cart wheels rotate a different speeds during turns. L.D. has always been one of my heroes.

 

Hosted on Fotki

 

[Snake45]

But "My four-speed, dual-quad, Leonardo Four-Oh-Nine" just doesn't sing....

[Ace-Garageguy]

While I've been a lifelong fan of Leo D., the explanation of a "rear differential designed to let cart wheels rotate a different speeds during turns" kinda begs the question of why the cart wheels weren't simply placed on bearings so that they could rotate separately?...which just about ANY cart or wagon wheels were.

The need for a differential is non-existent unless the "cart wheels" are mounted rigidly to the ends of an axle powered by something...not dragged down the road by a horse, ox, donkey, etc.

                                                                  

[Chuck Most]

While I've been a lifelong fan of Leo D., the explanation of a "rear differential designed to let cart wheels rotate a different speeds during turns" kinda begs the question of why the cart wheels weren't simply placed on bearings so that they could rotate separately?...which just about ANY cart or wagon wheels were.

The need for a differential is non-existent unless the "cart wheels" are mounted rigidly to the ends of an axle powered by something...not dragged down the road by a horse, ox, donkey, etc.

                                                                  

Could be that he was so taken by the idea of creating a cart differential that he never really stopped to ponder if such a thing was needed in the first place.  Or just mounting the wheels independently was too simple of a solution. Maybe he had some use in mind for the resulting "flywheel" on the back... kind of makes you wonder. 

 

[Dodge Driver]

While I've been a lifelong fan of Leo D., the explanation of a "rear differential designed to let cart wheels rotate a different speeds during turns" kinda begs the question of why the cart wheels weren't simply placed on bearings so that they could rotate separately?...which just about ANY cart or wagon wheels were.

The need for a differential is non-existent unless the "cart wheels" are mounted rigidly to the ends of an axle powered by something...not dragged down the road by a horse, ox, donkey, etc.

                                                                  

It looks to be a variation of Leonardo's odometer, from his drawings of a cart designed to measure distances.http://www.leonardo-da-vinci-models.com/da-Vinci-Models-Odometer-p2.jpg

 

Edited January 29, 2017 by Dodge Driver

[Snake45]

While I've been a lifelong fan of Leo D., the explanation of a "rear differential designed to let cart wheels rotate a different speeds during turns" kinda begs the question of why the cart wheels weren't simply placed on bearings so that they could rotate separately?...which just about ANY cart or wagon wheels were.

The need for a differential is non-existent unless the "cart wheels" are mounted rigidly to the ends of an axle powered by something...not dragged down the road by a horse, ox, donkey, etc.

                                                                  

He came up with an unnecessarily complicated solution to a problem that wasn't really that big a deal to start with? Could Leonardo have been part German?

[JollySipper]

He came up with an unnecessarily complicated solution to a problem that wasn't really that big a deal to start with? Could Leonardo have been part German?

Nah, ol' Leo presented to the World a complicated "bad" idea so that future generations could look at his designs and say 'there's a better way to do that'.......

A man ahead of his time! Look at some of his flying machines and you'll see what I mean.......

[Ace-Garageguy]

...Look at some of his flying machines and you'll see what I mean.......

Gotta love the air screw from 1493.    

He had a very strong intuitive grasp of what he wanted to accomplish and how to get started, but simply lacked the math and physics derived from hundreds of years of experimentation to make it all happen.

The design of his gliders reveals he appeared to have an understanding that the curved (airfoil) shape of a bird's wing was a necessary part of the equation for flight, and enough experimentation would have almost certainly revealed to him that the shape of his air-screw would have to be modified to include airfoil sections in order to provide lift (thrust) as well.

These are, of course, the elements the Wrights successfully combined in 1903, along with the necessary engine that was finally light enough...while still producing enough power...to lift itself. Then the helicopter finally realized his wingless-flying-machine vision in the 1940s (though a helicopter's blades are nothing more than rotating wings...)

[Ace-Garageguy]

Could be that he was so taken by the idea of creating a cart differential that he never really stopped to ponder if such a thing was needed in the first place.  Or just mounting the wheels independently was too simple of a solution. Maybe he had some use in mind for the resulting "flywheel" on the back... kind of makes you wonder. 

Indeed. Sure would be interesting to know what he was really thinking of. The differential effect as applied to a "cart designed to measure distances" wouldn't be necessary if one simply used a single wheel in the center of the whole affair connected to whatever the measuring apparatus was to have been.

Probably somewhere in his lost papers there was a drawing of a diesel-electric power unit too.  

[Dodge Driver]

Indeed. Sure would be interesting to know what he was really thinking of. The differential effect as applied to a "cart designed to measure distances" wouldn't be necessary if one simply used a single wheel in the center of the whole affair connected to whatever the measuring apparatus was to have been.

Probably somewhere in his lost papers there was a drawing of a diesel-electric power unit too.  

I found a different photo of the cart and it's a stand alone creation, not a derivative of the odometer. I was wrong about that.

[Snake45]

Gotta love the air screw from 1493.    

He had a very strong intuitive grasp of what he wanted to accomplish and how to get started, but simply lacked the math and physics derived from hundreds of years of experimentation to make it all happen.

The design of his gliders reveals he appeared to have an understanding that the curved (airfoil) shape of a bird's wing was a necessary part of the equation for flight, and enough experimentation would have almost certainly revealed to him that the shape of his air-screw would have to be modified to include airfoil sections in order to provide lift (thrust) as well.

These are, of course, the elements the Wrights successfully combined in 1903, along with the necessary engine that was finally light enough...while still producing enough power...to lift itself. Then the helicopter finally realized his wingless-flying-machine vision in the 1940s (though a helicopter's blades are nothing more than rotating wings...)

That "air screw" thing would never work. Unless you hooked two of them onto a common platform, preferably rotating in different directions. And even then, probably not.

[Chuck Most]

That "air screw" thing would never work. Unless you hooked two of them onto a common platform, preferably rotating in different directions. And even then, probably not.

Well, it wouldn't work for it's intended purpose. But it would make for one scary fun carnival ride if you worked out the bugs. 

[Lunajammer]

While I've been a lifelong fan of Leo D., the explanation of a "rear differential designed to let cart wheels rotate a different speeds during turns" kinda begs the question of why the cart wheels weren't simply placed on bearings so that they could rotate separately?...which just about ANY cart or wagon wheels were.

I wonder if it had to do with lateral stability over rough roads so your, um, donkey is getting less jostled. Italy was probably kind of rocky. Yes, it would be interesting to know what problem of the day he was trying to solve.

[Scott Colmer]

Hmm. I'm trying to think. Did they have berings then? I saw some at the exhibit too, but they were very large. 

 

Here is a link to the differential. I'm not sure if it answers the question as to "Why?"

 

http://www.abc.net.au/news/2016-04-19/a-model-of-da-vincis-design-of-a-cart-with-a-differential./7336748

 

 

[unclescott58]

But "My four-speed, dual-quad, Leonardo Four-Oh-Nine" just doesn't sing....

Sounds good to me. 

Scott

 

[Ace-Garageguy]

Hmm. I'm trying to think. Did they have berings then? I saw some at the exhibit too, but they were very large. 

A "bearing" is just about anything where two surfaces slide on each other. Bearings on wooden wheels on carts can be nothing more than a hole in the center of the wheel, with the end of the wooden axle sticking through, lubricated with animal fat or tallow.

There'd be no need for any "differential' with the wheels rotating freely on the axle this way.

Bearings were also made from other materials to prevent like-materials from being in contact with each other. Strips of lead or leather were common. Strips of leather have been used as emergency "bearing" material for 20th century automobile wheels and even internal engine parts, notably during the Dust Bowl migrations.

 

Edited February 1, 2017 by Ace-Garageguy

[Ace-Garageguy]

That "air screw" thing would never work. Unless you hooked two of them onto a common platform, preferably rotating in different directions. And even then, probably not.

The interesting thing is that Leonardo's "air screw" did in fact indicate he had an intuitive understanding of the problem, as it actually illustrates quite well the path of a propeller through the air.

                                                     

A large ship propeller is also very obviously much like his early idea, but with sections of the "screw" removed.    

What he did not grasp, however, was the particular non-intuitive working of an airfoil, which would have required rigorous experimentation and mathematical analysis to unravel.

BUT...if you simply cut away almost all of his "air screw" and left only two slender wings, you'd have something very much like the Wright's early propellers.

 

 

[Snake45]

The interesting thing is that Leonardo's "air screw" did in fact indicate he had an intuitive understanding of the problem, as it actually illustrates quite well the path of a propeller through the air.

                                                     

A large ship propeller is also very obviously much like his early idea, but with sections of the "screw" removed.    

What he did not grasp, however, was the particular non-intuitive working of an airfoil, which would have required rigorous experimentation and mathematical analysis to unravel.

BUT...if you simply cut away almost all of his "air screw" and left only two slender wings, you'd have something very much like the Wright's early propellers.

 

 

But he didn't intuit that as soon as the thing broke contact with the ground, the chassis would immediately start counter-rotating, killing half of whatever "lift" was being generated, and it would immediately sit right back down.

Unless of course you could figure some way for the "screw" to be powered independently, such as some early helicopters that had tiny jets or ramjets on the tips of the rotors. Otherwise, you need some sort of anti-torque provision.

[Ace-Garageguy]

But he didn't intuit that as soon as the thing broke contact with the ground, the chassis would immediately start counter-rotating, killing half of whatever "lift" was being generated, and it would immediately sit right back down.

Unless of course you could figure some way for the "screw" to be powered independently, such as some early helicopters that had tiny jets or ramjets on the tips of the rotors. Otherwise, you need some sort of anti-torque provision.

Agreed, but he did a pretty good job considering that the torque-reaction you mention wasn't formally understood until about 200 years later when Newton's Third Law stated:  For every action, there is an equal and opposite reaction.

Leonardo's air-screw is also likely influenced by the "Archimedes screw" used to pump water, which dates to the third century BC, but may be from as far back as 700 BC.