Scooter for the city

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maxysu
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Scooter for the city

Post by maxysu » Thu Mar 17, 2016 2:24 pm

Does anyone uses something like this for short rides in town (2-5 km):

Image

It is more convenient if you need to take the train regularly (for which one has to get a separate ticket for the bicycle). Is it true that one can go 15km/h with it?

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vexed87
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Re: Scooter for the city

Post by vexed87 » Fri Mar 18, 2016 10:34 am

I'm sure you could manage 15km/h on flat with effort, or more easily downhill, but here using that on the pavement/road would be frowned upon by the authorities and public alike.

This will get you around your extra charge issues and have a higher top speed!
http://www.thecyclecentrejsy.co.uk/bike ... olding.jpg
http://portapedalbike.com/wp-content/up ... dlebag.jpg

enigmaT120
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Re: Scooter for the city

Post by enigmaT120 » Fri Mar 18, 2016 11:26 am

Are those scooters faster than walking, with comparable effort? I've always wondered that about unicycles, too. I don't see the mechanical advantage.

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Sclass
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Re: Scooter for the city

Post by Sclass » Sat Mar 19, 2016 8:45 am

enigmaT120 wrote:Are those scooters faster than walking, with comparable effort? I've always wondered that about unicycles, too. I don't see the mechanical advantage.
I keep one in the trunk of my car. That way I can use remote parking places.

It's the same one I used in my business to cross between the manufacturing floor, warehouse, and the office areas. I had to walk miles back and forth when I was working. We had some longboards too that were fun...Sector 9 I think. The young guys brought them.

So I think yes. They can speed up moving across a seascape of linoleum. I got it because I heard the inventor of the Razor developed it for exactly that purpose. I don't know if that is true.

Edit - just found this story. I prolly read it here back in the day.

http://www.bloomberg.com/news/articles/ ... d-corp-dot

I like the folding model.

Toska2
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Re: Scooter for the city

Post by Toska2 » Sat Mar 19, 2016 12:11 pm

If I were to use such a contraption, it would have larger pneumatic tires for sidewalk irregularities.

15km/h might be pushing it (lol). I wouldn't rule it out if time and space were a factor. ie getting to a bus/train stop.

Solvent
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Re: Scooter for the city

Post by Solvent » Sat Mar 19, 2016 5:05 pm

viewtopic.php?f=7&t=7314

This came up not long ago actually. I had been thinking about getting one, and then I did.
I still haven't used it that much, although the weather is improving now.
It's definitely faster than walking. Mechanical advantage? Well, I don't know how to explain the physics of it but don't you have a mechanical advantage as soon as you have wheels? Depending on slope and smoothness of terrain. I mean you can't change gears to make a hill easier, so past a certain gradient it is easier to pick it up and walk. On the flat though, it's easier and faster than walking.

I take it on the bus no problem. My aim's not to cut out my bus ride entirely but to make the getting to the bus stop, and from the bus stop on the other end faster.

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Sclass
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Re: Scooter for the city

Post by Sclass » Sun Mar 20, 2016 9:41 am

Solvent wrote:viewtopic.php?f=7&t=7314

This came up not long ago actually. I had been thinking about getting one, and then I did.
I still haven't used it that much, although the weather is improving now.
It's definitely faster than walking. Mechanical advantage? Well, I don't know how to explain the physics of it but don't you have a mechanical advantage as soon as you have wheels? Depending on slope and smoothness of terrain. I mean you can't change gears to make a hill easier, so past a certain gradient it is easier to pick it up and walk. On the flat though, it's easier and faster than walking.

I take it on the bus no problem. My aim's not to cut out my bus ride entirely but to make the getting to the bus stop, and from the bus stop on the other end faster.
You know, this reminds me of a great discussion I had with a bunch of physicists and electrical engineers twenty years back. We were discussing all kinds of impedance matching techniques and why we use them...some examples are a horn, a bullwhip, an interference coating, a transmission, a transformer etc.

Basically the idea is if you want to efficiently couple energy between two unlike mediums you need to make some kind of gradual transition in "impedance" between the two or a lot of your energy will be reflected away. Think of trying to crack a whip made of a thick rope glued to a kite string versus a gradually tapering braid starting thick progressing to a thin cracker.

So one of the bike junkies threw us all for a loop and said "how about a bike". I never got my mind around it but he said the bike is like a transmission between a human and the ground. It tunes the impedance match for forward propulsion for more efficiency over running for instance. He went on to talk about our physiology isn't perfectly impedance matched for efficient forward propulsion so a multi speed bike gets us closer. I kind of got it...but I still really don't grasp it.

I think the answer to your question lies in here someplace. The scooter/human mass still has to be pushed along but it is all about how efficiently you get forward propulsion out of your legs. Simply put (and possibly wrong) scootering may not work as much against gravity as running on level smooth surfaces. If you integrate up all the jumping up and down you do while running it may use more energy than pushing yourself along a flatter trajectory. The bottom line is the advantage exists without a slope.

George the original one
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Re: Scooter for the city

Post by George the original one » Sun Mar 20, 2016 10:08 am

It's a mechanical advantage that ignores the work of making the ground smooth enough for the scooter to be effective. :)

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Re: Scooter for the city

Post by jacob » Sun Mar 20, 2016 10:39 am

Sclass wrote: So one of the bike junkies threw us all for a loop and said "how about a bike". I never got my mind around it but he said the bike is like a transmission between a human and the ground. It tunes the impedance match for forward propulsion for more efficiency over running for instance. He went on to talk about our physiology isn't perfectly impedance matched for efficient forward propulsion so a multi speed bike gets us closer.
In general, force(f) = impedance(f)*velocity(f), f is the frequency. Impedance is inherent to the system, force is what you supply, velocity is what you maintain. For non-cyclical systems, you can think of impedance as simple friction and the equation then describes the force you must continuously apply to maintain the velocity. For a cyclical system, where you are maintain a cyclical velocity with a cyclical force, impedance substitutes for simple friction and measures the resistance of the system as a function of frequency.

In electric terms, the analogy would be that force is the voltage, impedance is the resistance you're working against, and velocity is the current you want to keep driving around the circuit.

If you look at the power of your legs as a function of frequency (rpm) [like a power curve for an engine], it's a parabolic-like curve that peaks out around 70rpm(*) or so. Another way of putting that is that the impedance (of your human leg design when pedalling) is lowest at f=70Hz.

The bike is a simple system that translates rotation into linear distance (gear inches). Now all you gotta do is to set your gearing so that f=70Hz and you will be able to maintain the given velocity (selected by your gearing) with the minimum force. The gearing makes it possible to shift the impedance curve of the system to a wide range of velocities. If you don't have gears, the bike is essentially a system that makes your legs longer while supporting your weight. (See the laufmaschine below). For a standard gearing (42/11 or so), the bike would make each leg some 2.5 meters long!

(*) "Serious cyclists" like to run higher frequencies and are thus slightly inefficient. This is because the torque at higher rpm is lower which is better for the joints in the long run. This wasn't always so. Fifty years ago pro cyclists ran really high gears so they could go really fast while murdering their joints.

A scooter is probably even easier to understand. Here your leg acts as a pendulum which has a natural frequency given by the length of the leg. f=1/2pi sqrt(g/L). To propel the scooter, your swing your leg like a pendulum. The impedance is lowest around the natural frequency. This sets the optimal speed of the scooter. If you go faster or slower than that you're less efficient.---That would be like trying to push a swing outside of its natural frequency (same formula). The only way to go faster on a scooter with the same effort would be to make your leg longer. The speed goes like f*L ~ sqrt(L). This is why taller people are faster.

If you want a more efficient scooter---one where you can use both legs to "scoot"---check out the Laufmaschine.
https://en.wikipedia.org/wiki/Dandy_horse
from here on it's a small step towards the bicycle.

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BRUTE
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Re: Scooter for the city

Post by BRUTE » Sun Mar 20, 2016 2:13 pm

brute knows people who have the folding scooter for getting to the subway and back. they pack up pretty small compared to a bicycle. if the distance is less than 2-3 miles and one then takes it onto the subway or into a car, it's probably worth it vs. the better speed/comfort of a real or even folding bicycle. these things are definitely much faster than walking speed, probably a good sprint speed. there exist scooters with pneumatic tires, but these are generally bigger, and brute hasn't seen a folding model.

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Sclass
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Re: Scooter for the city

Post by Sclass » Sun Mar 20, 2016 7:17 pm

jacob wrote:
Sclass wrote: So one of the bike junkies threw us all for a loop and said "how about a bike". I never got my mind around it but he said the bike is like a transmission between a human and the ground. It tunes the impedance match for forward propulsion for more efficiency over running for instance. He went on to talk about our physiology isn't perfectly impedance matched for efficient forward propulsion so a multi speed bike gets us closer.

The impedance is lowest around the natural frequency. This sets the optimal speed of the scooter. If you go faster or slower than that you're less efficient.---That would be like trying to push a swing outside of its natural frequency (same formula). .

.
Thank you, this makes a ton of sense. Pretty much sums it up.

SallyJo
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Re: Scooter for the city

Post by SallyJo » Thu May 05, 2016 9:39 am

I used one a few years back. Parking near where I worked cost about $5 a day so I would park for free a bit further away and scoot the remaining distance. I found it to be twice as fast as walking. It would take 20 minutes to walk from my parking spot, 10 minutes by scooter.

Make sure to get one with bigger wheels, and perhaps pneumatic as someone here suggested. I started with one of those Razor units with the roller skate sized wheels. I crashed out numerous times on the sidewalk cracks - they just grab the little wheels and toss you before you know what happened. I cracked some ribs with one fall. Bigger wheels are not so bothered by the cracks and crevices.

Another effect I noticed: The leg that stayed on the scooter (the non-pushing leg) would get really sore and tight after 5 or ten minutes. I had to try to change up and push with it instead every so often, which is like writing with your non-dominant hand.

enigmaT120
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Re: Scooter for the city

Post by enigmaT120 » Thu May 05, 2016 9:31 pm

SallyJo wrote: Another effect I noticed: The leg that stayed on the scooter (the non-pushing leg) would get really sore and tight after 5 or ten minutes. I had to try to change up and push with it instead every so often, which is like writing with your non-dominant hand.
I always wonder about stuff like that: asymmetrical exercises. Last summer I tried to teach myself how to split firewood left handed. It sort of worked, in that I didn't hurt myself. But my accuracy sure sucked at first. I got better, and now that you reminded me, I'll try it again this year.

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