Space Hoppers

[Dure]

What if, in the late 19th Century the Space Hopper is invented and rivals the bicycle in popularity. There is more investment in Space Hoppers or the 'Gentleman's leaping dervish' as it is known, than there is in the bicycle. Eventually cycling becomes a minor sport whilst leaping becomes an international sport and mass hobby. How does this affect the application of the Sterling, Diesel and internal combustion engines when they arrive? Do we get three and four wheeled cars as in OTL or do we get powered Space Hoppers?

 

[Tom Veil]

You're going to have to provide a little more explanation...

 

[DoktorDespot]

Youve got to be joking right:

Space Hopper:

 

[Dure]

Well obviously they would have to be made of natural rubber to start off with.

 

[Michael Busch]

Bicycling is an efficient form of long-distance transportation. Space Hopper, not so much. This is ASB, but funny.

 

[Dure]

My preposition is that if percussive pneumatic transport had the same levels of development and investment as bicycles over the same period of time that bicycles have been being developed then percussive pneumatic transport would be as efficient as bicycles are now if not more so.

 

[Michael Busch]

My preposition is that if percussive pneumatic transport had the same levels of development and investment as bicycles over the same period of time that bicycles have been being developed then percussive pneumatic transport would be as efficient as bicycles are now if not more so.

Not possible. You loose a lot of energy bouncing up and down as compared to rolling a wheel.

I really hope that you intend this entire thread as a joke.

 

[Dure]

Michael,

As a scientist I am sure you will realise that simply saying:

Not possible

Is completely unacceptable. We require evidence.

Then making an unsupported claim about wheels and bouncing and their relative efficiencies is not a proper refutation. You should be well aware that a thermodynamic cycle based on the adiabatic compression/expansion of a column of gas is, in thermodynamic terms about as efficient as it gets. The efficiency of a wheel however is largely a function of the technological level of the mechanical engineering that goes into the construction of the wheel and the environment in which the wheel is used.

In other words, based on first principals physics the Space Hopper kicks bicycle arse.

 

[Tobit]

what would a powered space hopper look like? The idea certainly is cool.

 

[Michael Busch]

We require evidence.

Sorry - I was in a hurry and the answer seemed obvious. My logic is below.

In other words, based on first principals physics the Space Hopper kicks bicycle arse.

No.

First, we have the control problem: a rolling wheel moves in a straight line and is stable. A bouncing hopper is an unstable equilibrium - it tends to fall over. It takes energy to keep it moving straight. Perhaps you can get around that with some active control system, but it is an important component.

Second, the compression and expansion of the gas is not the problem with a hopper. In a bicycle, the sources of energy loss are all friction: the bearings, the atmosphere, the ground, and the brakes when they are on. In a hopper, the energy loss is elastic deformation of the bladder. That is a lot of energy for something made out of rubber or plastic. If you were using pistons instead, you could use grease to lubricate them, but the friction on a human-sized set would be a lot larger than that on bicycle bearings.

The elastic energy loss and the control problem are why a hopper is so much slower than a bicycle, a runner, or (usually) a walker. Maybe you can make a faster version with some crazy materials science, but the hopper is still impossible to use if you are going fast. This is a mood of transportation that involves bouncing off the ground and landing again and again and again. The acceleration and jolting are killers - and that is why a powered version is a very very bad idea. See what happened to the Mars rovers when they did their airbag landing and you have what you'd be feeling whenever you went anywhere.

 

[Dure]

First, we have the control problem: a rolling wheel moves in a straight line and is stable. A bouncing hopper is an unstable equilibrium - it tends to fall over. It takes energy to keep it moving straight. Perhaps you can get around that with some active control system, but it is an important component.

Gyro or just flatten the bottom and 150 years of development. With a nice flat bottom I can even see them being used by paraplegics to get about. This idea is really going places. I really appreciate your input. It has been very helpful.

Second, the compression and expansion of the gas is not the problem with a hopper. In a bicycle, the sources of energy loss are all friction: the bearings, the atmosphere, the ground, and the brakes when they are on. In a hopper, the energy loss is elastic deformation of the bladder. That is a lot of energy for something made out of rubber or plastic. If you were using pistons instead, you could use grease to lubricate them, but the friction on a human-sized set would be a lot larger than that on bicycle bearings.

With a small motor as I have suggested this would be no problem.
I like the idea of the pistons, it is basically the kangaroo walkers you see kids using these days. They are the result of just 15 years or so development. Just think where the Victorians and Edwardians will take the Space Hopper given 150 years. If they can come up with a puncture proof fabric then I confidently expect Space Hopper mounted Infantry on the Somme. They will be khaki of course the bright orange would just attract snipers. If you like you can develop your own thread on kangaroo walkers Michael your idea is a pretty good bit of steam punk.

The elastic energy loss and the control problem are why a hopper is so much slower than a bicycle, a runner, or (usually) a walker. Maybe you can make a faster version with some crazy materials science, but the hopper is still impossible to use if you are going fast. This is a mood of transportation that involves bouncing off the ground and landing again and again and again. The acceleration and jolting are killers - and that is why a powered version is a very very bad idea. See what happened to the Mars rovers when they did their airbag landing and you have what you'd be feeling whenever you went anywhere.

The Victorians are used to jolting and bouncing, they ride horses after all. I think this is a bit of a non-issue. Air bag landings are a bloody stupid idea for space probes for numerous reasons we can discuss elsewhere but in any case the closing velocity is so much greater than that of a Space Hopper by at least one if not two orders of magnitude that the analogy is irrelevant.

 

[mowque]

Love this site.

 

[Dure]

what would a powered space hopper look like? The idea certainly is cool.

Well orange obviously, except for the military ones which would be green or perhaps DPM.

The motorised ones would have a small roots or piston blower at the top rear to provide the pneumatic pulse this would be powered by a small engine of some sort.

I suspect the early ones would have a saddle not unlike an English riding saddle and there would be lots of brass and ivory fixtures.

In the 1950s I suspect there would be a response to the shortages of WWII and they will get seats like an OTL Lambretta so your girlfriends can sit behind you. They will also get chrome and perspex fittings.

 

[Michael Busch]

I call Butterfly, and must insist on my previous call of ASB.

Let me explain the magnitude of the jolting you'd be talking about, so you understand why this is a bad idea, the power and stability problems aside:

Say an early bicycle goes at a typical speed of 5 m/s (11 miles an hour) and you want a person-sized hopper to match that. You hit the ground at 5 m/s on a hopper 0.5 m across. Say you compress it to zero thickness each time you bounce (an exaggeration). If you were going straight up and down, that would be equivalent to taking an automobile airbag to your posterior on each bounce.

On a flat surface, it is nowhere near as bad as that, because most of the velocity is tangential to the surface. Going down hill on a hopper at that speed, you will have serious bruising very shortly, and on the flat any large distances will cause a high rate of repetitive stress fractures. Going up hill is less bad for the stress, but requires very strong legs.

The injuries get worse with the square of the velocity, so bouncing around a room at 0.5-1 m/s isn't a problem.

 

[Mike Stearns]

Love this site.

Yeah. Threads like this one are the reason why AH.com is called the place where what if? meets what the fuck?!

 

[9 Fanged Hummingbird]

I'm gonna take a stretch and say that even if he's joking, Dure has obviously gone completely insane. Like, a Col. Kurtz kind of insane. Not that this is a bad thing mind you, we need people to start monologuing, people with power!

 

[Kevin in Indy]

Cool Hobby, but...

This could make a fascinating hobby, with all sorts of derivative races, parade units, treks across England / Asia / North America, hopper racks in public places, etc. I don't think, however, that a hopper could permanently supplant wheeled transport should that develop. The repetitive shock is just too much.

Rather than a "powered hopper" might a more plausible development path be into "walkers" taking advantage of the "flat-bottomed" hopper design?

Anybody with an artistic streak (not me) - remember that bear cavalry poster - can you imagine a military-camo, two-man hopper (one driver, one shooter) with the "hopper cavalry" title?

Now, one fascinating idea would be for hopper technology to slow the development of wheeled transport until something even more fun came along, such as hovercraft...

 

[Kevin in Indy]

Stray Thought

Please don't take this wrong, but I cannot escape the vision ala Invader Zim of a group of cattle (or maybe cocktail weenies) on "gentlemen's leaping dervishes" chanting in a digitally modified voice, "Hop with us, Dure! Hop with us into oblivion..."

 

[Dure]

I call Butterfly,

Aw! Pet names for me how romantic. I shall call you Cricket to keep it within the Insect clade.

and must insist on my previous call of ASB.

No we really don’t need an Anti-lock System of Breaking (ASB) for the Space Hopper.

Let me explain the magnitude of the jolting you'd be talking about, so you understand why this is a bad idea, the power and stability problems aside:

So many negative waves, you are almost worse than Douglas!

Say an early bicycle goes at a typical speed of 5 m/s (11 miles an hour) and you want a person-sized hopper to match that. You hit the ground at 5 m/s on a hopper 0.5 m across. Say you compress it to zero thickness each time you bounce (an exaggeration). If you were going straight up and down, that would be equivalent to taking an automobile airbag to your posterior on each bounce.

This is a dodgy analysis to say the least. Both the material from which the Space Hopper is made and the low pressure gas within it are highly compliant and can be made more so with the addition of a small compression chamber. An air bag as it approaches full inflation is only slightly compliant and because it is at higher pressure than the Space Hopper transmits more force. The compliant Space Hopper will I am sure offer no more discomfort to the cheeks than a horse would.

On a flat surface, it is nowhere near as bad as that, because most of the velocity is tangential to the surface. Going down hill on a hopper at that speed, you will have serious bruising very shortly, and on the flat any large distances will cause a high rate of repetitive stress fractures. Going up hill is less bad for the stress, but requires very strong legs.

This is a good point. A variable geometry saddle might be needed on the ‘mountain’ versions

The injuries get worse with the square of the velocity, so bouncing around a room at 0.5-1 m/s isn't a problem.

This is fallacious and correlates injury to kinetic energy rather than momentum transfer which correlates linearly.

I am sorry you did not take up the opportunity to develop the kangaroo walker concept. I think it is rather a magnificent one. It will lead to a completely different WWI.

On the Somme the huge guns fall silent and the British assault begins. Tommys equipped with kangaroo walkers leap up above the parapets of their trenches and begin to stride towards the German positions. They reach the barbed wire and leap high and far across it. Just then the German machine guns open up but the British infantry are too close and the Germans cannot raise the elevations of their machine guns high enough to stop the rain of Tommys with bayonets as they fall upon the foe. The brake through is complete all down the line. The big gap is here at last. The British cavalry move forward to exploit it supported by tens of thousands of dervish mounted ‘fast’ infantry and horse artillery.

The next year at Cambrai the British unleash the bouncing tank on an unsuspecting world. The German infantry reeling after the introduction of the kangaroo walker infantry are completely unable to deal with the near 40 ton monsters that launch themselves 50’ into the air and over 300’ forward on each bounce. In short order all German opposition is completely crushed.

 

[Dure]

This time-line is really going places but I would really like it to link up with my Queen Victoria introduces the bikini idea. Does anyone have any suggestions?