Friday, October 24, 2014

She's dead Jim. Requiem for a 9 year old G5 iMac

I bought my G5 20” iMac in July of 2005 with a 400GB SATA drive and SuperDrive for $1879, it expired today at 9y3m of age. I think the 400 GB Hitachi Deskstar is original - so it is the longest lived hard drive I’ve owned. I pulled it and was able to read it from a drive cradle, though there’s nothing left on there we need.


Today the comparable machine in Apple’s lineup is the 27” 3.2GHz iMac with a 1TB SATA drive but no SuperDrive for $1799. Of course that’s a far faster machine and a much nicer display, but the price is remarkably similar. Not to mention that we’d need to add an ugly external DVD player.

I doubt the 2014 iMac will last 9 years, not least because it’s costly to service. The G5 iMac was designed to be user serviceable — perhaps because Apple stores weren’t ubiquitous. The back came off with 3 standard Philips head screws. It was trivial to swap out a hard drive or memory. When the power supply died in 2011 ($150 for iFixit, there was a recall @2006) it wasn’t hard to swap it out. I think that replacement power supply just died; this time I decided a repair wasn’t worth the trouble.

The G5 iMac was not trouble free. Besides the power supply issues many died young from capacitor failure (defective manufacturing) — though I somehow missed that. The G5 ran very hot, it took Apple a year or two to figure out a reasonable fan management solution. Worst of all, the display developed internal discoloration [1]. 

Despite the issues, 9 years is a pretty respectable lifespan for a heavily used computer. We got a lot of use out of that machine, not least as a handy DVD screen.

Not a perfect machine by any means, but not bad.

- fn -

[1] My 2009 27” iMac has a similar discoloration though it fades with use. It has had two drive failures in 5 years, the last time I put in an SSD.

See also

Sunday, October 19, 2014

The relativistic version of the linear motion equation: velocity = acceleration*time.

My son is starting to do … physics.

It is fair to say I am more excited about this than he is. There is a reason I have a copy of the 1973 Edition of Misner, Thorne and Wheeler’s Gravitation ($35!) on my bookcase. I’m saving it for retirement, by which time will breeze through all the visualizations. It is true I was a failure (non-physicist) at Caltech, but there’s still time…

Ahem. So when #w was given an assignment to create a poster about linear motion, with equations on time, velocity, constant acceleration and the like, I thought it would be fun to show that the equations of linear motion are merely a low velocity approximation to the relativistic equations of linear motion. I was sure a quick Google search would turn up a simple simulation that would look like:

v=a*t (starting at rest velocity after time t is acceleration times t)

Riiiight. I’m sure that simulation exists, but I was never able to find it. With a bit of thought about the problem I realized I might be better off dropping the tricksy concept of acceleration and looking for a relativistic version of:

v= (F/m)*t (since change in velocity is Force*Time/Mass. Push a trike, push a truck, which moves faster?)

That found an “off-topic” [1] stack overflow article which was just a few parentheses short of the good-enough equation [2]: v = c * tanh(asinh((F*t)/(m*c))).

This is the first time I’ve personally run into hyperbolic trig functions, so I thought that was pretty cool, especially since I’d just read Jon Butterworth’s lovely description of how one hops from simple physics to quantum physics simply by tossing the square root of -1 (i) into a classical wave equation (uses Euler’s Formula, so extra points). That article used the familiar sin/cos functions, so I was getting an extra dose of trig. 

Plugging v = c * tanh(asinh((F*t)/(m*c))) into Wolfram Alpha gave me this cool output (yes, the AIs wll be our death, but for now they’re fun):

Screen Shot 2014 10 19 at 1 20 50 PM

Now that is what I was looking for! It clearly reduces to v = (F/m)*t when the squared stuff is relatively small. [5]

We can now compare my son’s high school textbook linear motion equation (v=F/m*t) to the relativistic equation, using the sneaky physics trick of geometrized units so c=1. Just to make things even nicer I’ll arbitrarily set the applied force to “1” (some unit) and the mass to “1” (some unit). This is what Desmos shows:

Screen Shot 2014 10 19 at 1 56 56 PM 

The last shows how simple this is in geometrized units (v is change in velocity over time t in our funky units):

Screen Shot 2014 10 19 at 2 10 11 PM

and here’s the magic graph that shows what happens as velocity (y axis) approaches “1” (speed of light) in the original linear motion equation and the relativistic version:

Screen Shot 2014 10 19 at 1 58 53 PM

Yeah, hits the speed limit. [5]

[1] The iron law of StackOverflow is that any article of interest will sooner or later by marked off-topic.

[2] I discovered the problem when I plugged it into Wolfram alpha, I had to do some web searches and play around the parens to get the correct expression.

[3] Incidentally, if you’d told me in 1995 that we would still lack easy entry of mathematical notation into web pages in 2014 I’d have assumed some kind of worldwide civilizational collapse.

[4] Once I had this expression, which was provided by the Wolfram AI, I found a discussion thread (scroll down) telling me it can be derived by “substituting F/m for a in the Baez equations(where m is the proper mass) and dividing by c where the tanh/sinh stuff is related to “proper and coordinate time”.

[5] I’ve done great violence here to the principles of general relativity — the meaning of time and distance are entirely dependent on frames of reference and I’ve glossed over all of that — largely because, you know, I’m not a physicist. It is kind of neat, however, what one can kludge together with a handful of web tools. In the general vein of non-physicist at play, it’s fun to compare this to Butterworth’s masterly representation of quantum physics using high school math. I again am left with feeling that physics will be easier to understand once we figure out what “distance” and “time” emerge from.

Friday, October 17, 2014

Blogging is definitively back - the NYT has redone their Zombie RSS page

My feeds (Feedbin/Reeder) have never gone quiet — but there’s no doubt it was getting harder to find links to feeds over the two years since Google tried to kill RSS to boost G+.

Then came signs of a turnaround. Apple very quietly added RSS reading back into Safari — after removing RSS from both Safari and [2]. Google, fairly quietly, backed away from G+ — I don’t get any G+ social invites at all any more. More interestingly, Google blogs all became more active. Microsoft kept RSS features in IE 11. Facebook never removed RSS from Pages. Old blogs started lighting up in my feed reader. Rosenberg has started writing about a blog revival amidst disaffection with Twitter and Facebook [1]. 

All significant developments, but they pale next to the very biggest sign of them all — the New York Times has updated their RSS - Feed Page! It no longer recommends use of Google Reader! [3] The NYT has even added Topic Feeds:

Times Topics feeds collect news, reference, photos, graphics, audio and video on thousands of subjects, covering material published since 1981 … Search 10,000+ Times Topics Feeds

 Dave Winer should be a happy guy today.

[1] Not directly related, but fairly suddenly, and for no obvious reason, many of my friends and family have stopped posting on Facebook.

[2] Apple needs to update it’s RSS Feed page though — it doesn’t mention use of Safari.

[3] It does mention AOL Reader. I thought that was a bad sign, but, and this shocks me, AOL really does have a Feed Reader with its own spiffy web site: "Moving from another RSS reader? You can upload your subscriptions in standard OPML format and start reading right away!”. It even has its own friggin’ API. Turns out this was launched a year ago. It’s still in beta, but there’s an active development blog and they released an iOS app in August that has few ratings but seems well liked. Best of all, it supports OPML export as well as import. So this is a real contender.

Thursday, October 16, 2014

The Alibaba/Apple Ratio and the fools guide to post-bubble market timing

Google tells me Apple’s market cap today is 576.39 billion dollars. (Think on that for a moment.)

Alibaba’s market cap is 223.28 billion dollars.

So the Alibaba/Apple ratio is 0.39.

I’ll be buying into the S&P as the market falls, but I’ll buy more when that ratio gets closer to 0.10.

Monday, October 13, 2014

Repairing carbon frame mountain bikes: Ruckus Composites vs. Cyclocarbon

With this post I'll finish my 3 week journey from carbon frame naivete to bloodied veteran (see below for related posts). It began when a bike shop refused to repair my newly acquired used Cannnodale Scalpel because of this frame finding:

Yes, the strange irregular line where the end of an aluminum seat insert meets a carbon frame top tube. The bike shop and everyone else who looked at it was certain the frame was dangerously unride-able, whereas the previous owner felt it was fine. (As it turned out, it's not clear who was right [2], only that there was no way to service the bike.)

After a bit of research guided by local bike shops and mountain biking friends, I learned about the hierarchy of carbon frame repairs. There are roughly 3 levels of carbon frame repair:
  • Elite: often with a national market, may use ultrasound to inspect frame, usually need to strip bike and ship frame, repairs take 4-6 weeks but look like new.
  • Regional "race ready": services a metro area or geographic region, mostly hand delivered bikes, focuses on fast turnaround rather than fine finish. Often used by racers, who own the majority of broken frames.
  • Hobbyists who do a small number of frames, often for friends.
I ended up comparing an elite option from Ruckus Composites with a "race-ready" option from Drew at Cyclocarbon. This is what I heard back from Ruckus after they reviewed my blog post:
Ruckus Composites 
... First we will do a full inspection for structural integrity on the frame and hunt out all of the damage. once that is complete we will contact you with a quote and report our findings. 
After that we’ll machine out the damaged carbon fiber because (like a crack in a windshield or a tear in your jeans) all of the damage needs to be removed or it’ll keep propagating under the patch. 
Once we have that taken care of, we can go in and structurally rebuild it with fresh carbon fiber. When that’s done, we can repaint and clearcoat your frame so it’ll be just like new. 
For a repair like this I would estimate around $400-500 and about 3 weeks of in-house labor to complete. I suggest the next step you take is to take your bike to your local friendly bike shop and have them tear it down and box it up. Tearing the bike down to just a frame makes shipping a lot cheaper...
Cyclocarbon (Cyclocarbon on Facebook is more active) doesn't do this "like new" kind of repair. They do "race ready" for $150-$200, typically in about 3-5 days. That means no repainting of the original decals, no clearcoat, and a functional rather than "like new" shape. Repair warranty is informal.

I ended up going with Cyclocarbon, in large part because of turnaround time and because Emily was willing to drive my bike 1.5 hours from St Paul to Rochester MN [1]. Cyclocarbon has a strong local reputation, so I felt their repair would be reliable. For me the cost and hassle of tear down, shipping, and reassembly outweighed the aesthetics of a Ruckus repair. Once I factored in shipping and assembly costs Cyclocarbon was also significantly less expensive.

I think Ruckus would have been an excellent choice too however. I do miss the Scalpel graphics, and my top tube now has a bit of pudge. If I'd gone the Ruckus route I'd have invested in tools to do my own disassembly and reassembly.

It's good to have choices.

[1] If she'd known who lousy the drive would be that day I'm sure I'd have done local shipping rather than driving. I was able to pickup the bike during a trip to Rochester for my son's High School mountain biking race.

[2] Cyclocarbon's Drew tells me that despite the worrying artifact the carbon seemed strong. He's not sure whether the frame was truly weakened.

See also:

PhotoCard 1914

I'm a fan of Bill Atkinson's;  I send one weekly to my father, currently in long-term care. I love the fusion of ancient Egyption and modern American tech.

So I appreciated discovering a 100 year old PhotoCard in my father's effects. This print is a (way) pre-photoshop overlay of my father's Uncle Max and his mates on an 'ISOLATED' image.

On the back of the print is the stamp that made it a 1914 PhotoCard - with a section for postage and for a note. (In this case it was never stamped).

Hard to believe there will still be postal delivery in 100 years, but maybe Amazon will stick them in packages.

Sunday, October 12, 2014

What is the best material for a mountain bike frame?

One of the great things about blogging is that it lets someone who knows very little look much the same as a world class expert. All of the usual cues to merit and expertise are stripped way. In the Feed Reader, nobody knows you're a naif.

Ok, that's enough informed consent. I'm now going to tell you what material works best for a mountain bike frame - Aluminum, Steel, or Carbon. I base this wisdom on two weeks of recrimination after Akerloff's information asymmetry and rampant bike lust [1] got me a problematic Carbon Frame Cannondale racing mountain bike. During this time I sorted out how to buy a used mountain bike and why Carbon frame warranty loss hits resale value -- and I came up with the definitive guide to the BEST frame material:

Attribute Aluminum Steel Carbon
Perform 2 1 4
Retail $ [2] 4 2 1
Repair $ [2] 1 1 3
Reliability 3 4 1
Comfort 1 2 4
Lifespan 2 4 1

The spider graph [3] makes it clear ...

What do you mean there's no clear winner?!

Year, it's like that. Since I don't race and don't have time to spend on fussy stuff I'd be best off with an aluminum frame or, if I had the money, a steel frame from one of the elite Minnesota steel bike companies. Still, there's no denying the performance and comfort of carbon.

So it just depends.

I lied. Sorry.

[1] My brother bought a Porsche under similar circumstances. He says I got off easy.
[2] In these cases higher rating is less cost. Carbon can be relatively cheap to repair if you can find the right person or don't mind mailing a frame.
[3] It is really quite amazing that one can create a table in Excel/Windows and paste it into Blogger's composer window as an HTML table. I don't think I can do that on my Mac. I tried to do this graph in Google Spreadsheet but didn't seem to be supported there.