Saturday, June 29, 2013

Citi Bike is failing at physics

It seems that New York City needs to take some remedial STEM – the promotional materials for NYC BikeShare have an elementary physics mistake.

Their marketing materials state:
[the bike] has a low center of gravity for a more stable ride.
It turns out that a moving bicycle, is actually less stable when the center of gravity is low. Much like a balancing a pencil (low CG) is harder than balancing a broomstick (high CG). This phenomenon is explained well in this article about robot bicycles.
I emailed citi bike to complain and they responded with this:
I'm fairly certain that the engineers involved in constructing these bikes have looked at the pros and cons of both high and low centers of gravity, and found this to be the best option for the widest range of people.
I cannot argue with this. I've ridden these things in Boston and in Washington DC and they are indeed very stable; nicely done engineers! The stability has absolutely nothing to do with a "low center of gravity." In fact the stability to ride might actually be due to a high center of gravity for bike+person compared to more aggressive bike frames.
The next thing citibike said was:
Besides, almost anything with a lower center of gravity is going to be more stable based on simple physical laws.
Correct and irreverent again. Objects siting motionless on the ground will be more stable with a low center of gravity. But bikes mid "ride" are more like an inverted pendulum than a stable object. Here are some suggestions for a new description.


I wouldn't normally be so fast to recommend remedial classes ... but just last march NYC made a subway poster which mathematically embarrassing at best. Also, several years ago Eli previously discussed the state of science education in NYC which left much to be desired.

I'll end this post with a snobby message from Boston: get it together New York!

Thursday, June 27, 2013

Cell phone tower camouflage

The ridiculousness of cell phone tower camouflage is well known. See, for example, Keeping Up With The Parental Units or this excellent gallery. Today, I noticed a different sort of camouflage:
They tried painting the cell phone antenna to look like the brick behind it:
At the end of the day, this still looks ridiculous. At a certain point they should just embrace the antennas as is, and stop trying to hide it.

Sunday, June 23, 2013

Getting around Boston by bicycle is fastest



When I used to live on the (B) line in Boston - I would bicycle past two or more (T)rolley cars on my way to BU. It seemed faster to bike anywhere than to take the public transportation option. To find out which one is really faster - I collected some data from Google maps. After my fellow blogging brother (Eli) challenged me - I ended up comparing cycling to public transportation times for travel to anywhere in Boston and starting at any time of day. The video above is the result.

For more commentary see this blog post about how getting a bike will open up your city. If you want to see how I actually did this (collected and plotted the data) go to the description on my homepage here.

For high-resolution images of these charts see below:

Tuesday, June 18, 2013

Shotgun Bulb

Last week I went to visit my old high school auto shop. They where mounting an electronically (or handcuff key) locked shotgun mount. For some idiotic reason this mount which was designed for cars was also designed to take 5 volt DC power (cars use 12 volt DC). To reduce the voltage across the solenoid in the mount they had mounted a resistor in series with the mount, however after they did this the solenoid no longer actuated. I thought to check the resistance on the solenoid and found it to be about 4.5 Ohms, the resistor they were using was a 1 kOhm resistor. What this meant was that there was almost no voltage or current across the solenoid. I did some math and determined that what they needed was a 10 Ohm resistor to get 5 Volts across the mount. However 10 Ohm resistors tend to be far more pricey and bulky than regular resistors because they tend to have to deal with far more power than most resistors due to V=IR (so if the resistance gets smaller and the voltage stays constant much more current is drawn), also we didn't have one. What we did have was an old tail light with resistance close enough for our purpose. So now whenever the switch is flipped to open the shotgun mount a light will turn on.

 The switch.

 The lightbulb on.

 Shotgun mount closed.

Mount open, it is designed so that you can simply flick the switch and pull the gun out.

If you ever wondered what was in a cops trunk. The red and blue lights flash whenever the trunk is open.

Thursday, June 13, 2013

On the blink

A phone at work was having some difficulties:
Either that, or this person was very popular.

Sunday, June 09, 2013

Waterworks Museum Demo

I built a little demonstration for the Metropolitan Waterworks Museum. There is a longer description of how the demo actually works over on my homepage here. Since I added the laser-etched labels the only thing that is missing is a super-cheesy facilitator script with lots of bad puns... anyone?


Here is the demo being built.

It was built at a time when labor cost was a lot less than material cost. Everything in the building looks amazing.


This is a big one-way valve to control water in the reciprocating pumps.


I would consider this museum to be a must-see if you are in Boston. Feel free to ping me and I'll give you a tour.


Thursday, June 06, 2013

Too many emails

Our synagogue, Congregation Shaare Tefillah, has an email list for members. I've noticed an increase in the number of emails I've been getting over the last few months, so I decided to see how bad it is. I've discovered that the number of emails going out has been increasing exponentially. That means that not only are the numbers of emails going out increasing with time, but the rate of increase is increasing with time, too:

The number of emails going out is doubling just over every four years. In seven years we'll have 200 emails a month (or 6-7 a day). It is worth noting that the month-to-month variation in number of emails is increasing, so even if it looks like "Hey, we had fewer emails in month x", it's entirely likely that the next month will be higher:

I recognize that some of this is due to our rapid growth as a shul. However, our emails per member ratio has also been increasing:


The two curves correspond to an exponential fit to both members and emails (the better fit, IMO) and a linear fit. In both cases the number of emails sent increases at a larger rate than the membership.

I'm sure there's something that can be done about it, but, for now, I just set up an email filter...

Sunday, June 02, 2013

Poem: The grouse and the pattern

Here is a cool grouse,
in a tree having fun

Here is a cool pattern,
partly lit by the sun