A massive eruption took place in the sea just meters in front of this lighthouse in 1957 (over 13 months). What was before the tip of the island is no more. This is now a magical place of inevitable history and volcanic science.
The more I look at this picture the more I like it.
And it's not one of those I thought: "this will make a fantastic shot" when I took it.
Been researching the various valvetrain designs out of a philosophical discussion on hydraulic adjusters not commonly employed in motorcycles (H-D engines are the notable exception). Fascinating!
I found out how hydraulic adjusters are currently used in various car engines and how elegantly they solve the problem of keeping valve clearances. I also read a bit about pneumatic actuated valves with cams/followers or with electro-hydraulic actuators and no cams. Clever!
Being uninformed about hydraulic valve adjusters, I did the right thing and researched a bit. I'll share a summary for those that, like me, would like to know.
Hydraulic valve adjusters are a clever solution meant to solve the problem of keeping correct valve tolerances at any engine/oil temperature. Incidentally the design led to having permanent contact between cam, lifter, pushrod, rocker arm and valve stem, making it quieter.
[I now realise that the more common cam followers+shims+buckets should equally have (more or less) permanent contact between all the parts. This happens because followers to shim clearances are filled by oil pressure that builds up underneath the buckets as the engine runs: makes sense and came from a very reliable source.]
This is an open loop feedback system in which pushrod operating travel changes by action of hydraulic lifters which, in turn, are influenced by engine pressure and/or temperature. Ingenious!
"Our" design is more on the style of "getting it right for the typical range of engine temperatures".
Two typical engineering approaches to the problem, both with their pros and cons. While it's easier to see the cons in the non-hydraulic shim+bucket style system, the hydraulic type is not without them:
Being an open loop system, it relies on correct information coming in from oil (density+type+dirt+volume=different pressure vs temperature curves) as well as integrity of the lifter itself (spring load). But even if everything else is kept, oil changes with wear and that affects operation of the lifters. Self adjusting valves gradually come out of adjustment at all engine temperatures. Then of course this is a more complex system and probably more expensive to manufacture. Hydraulic lifters are precision parts with very tight tolerances. It is hard to tell if the time it takes to get a valve significantly out of tolerance is so long that it becomes non-serviceable... I really don't know. Some people say yay other say nay.
Me, I would go for the hydraulic type, but I'm an engineer, not a business man. On that note, how about the desmodronic valve actuator system currently used in Ducati engines? Funky, eh?
Thanks for reading. Feel free to poke holes at it.
References were:
One wonderful thing about bikes is that much more often than in a car, you go out for a ride with no purpose, sometimes with no defined direction or destination.
I work in an office in Thame, roughly 15 miles away from home. Commuting by motorcycle is good and fun: not too long, very little traffic, twisty but safe (good visibility throughout, no sudden tight bends, etc). It's a good mix of city, dual carriageway (A40) and A-road (A418).
Weird stuff went on recently on my network;
It started last night while I was fiddling with my lab network - dark witchcraft including ospf, eigrp, nat, acls, ppp/chap, etc. I discarded it as being my laptop still fussing with its gateways and default routes... I was tired and didn't care. So I just turned things off, went to bed and forgot about it.
[side note: I should post my network diagram someday, so everyone can appreciate a true overkill geek home network...]
This morning, though, my wife couldn't reach facebook from her laptop. Whoops, I must have done *something*...
Symptoms were:
First things first: Check the squid proxy - seemed ok;
Lazy as I am, I decided to just reboot the routers because I might have left some not-very-well-though-configs there. The routers came back up and the situation got worse! Now I had no comms between the core and uplink routers. WTF?
The router was broadcasting BPDUs out its ports triggering bpduguard on the switch which, in turn, disabled all the ports that connect to the router (the ones from which BPDUs were received). This effectively shut the router off the switch.
As a quick & dirty solution, I enabled bpdufilter on those switch ports. Just ignore those BPDUs instead of disabling the ports if one is received (bpduguard is setup globally on the switch, rather than port by port); The proper solution involves shutting down STP on the router instead with no spanning-tree vlan X commands.
Layer 2 issues sorted, I was back to last night's situation. Being a little more pragmatic this time, I disabled wccp redirects from the core router. Sure enough, everything was back to normal. The proxy was good but the connection between the core router and the proxy service/host was not (this connection being a GRE tunnel - did I mention how nice WCCP is??).
I had a massive update pending on the server including a kernel upgrade. I had to reboot now. Naturally the server did not come back up as expected because the updated version of udev required a kernel >=2.6.27. The latest accessible kernel was 2.6.26 - d'ough!!
So there I was manually creating md nodes on /dev via a serial console to mount and copy the newest available kernel, modify grub's configuration and try again with a new kernel. It worked! Everything came back to normal, the GRE tunnel came back up, as all other services on the server.
Along with all this, I forgot about the new terms of service of editdns.net (my DNS provider) and they cancelled my account. My domain pjvenda.net has been unavailable since 3rd January 2010 and should only be restored after tonight (10th January 2010).
I'm lame sometimes. Must be the cold.
Cheers, PJ
I know there is still time, but I don't expect many more convenient breaks in this British weather.
I took this picture after coming back from a short ride earlier this month - an English December, mind you. It was a good ride through Oxford city streets. The weather was dry and not too cold (for my kit). If everything seems grey and dull, it's because it was.
I doubt I'll be able to go out again this year and if so, here it is: the record of the last ride of 2009.
Cheers, PJ.
Taken from the hotel's balcony, while having dinner, during my honeymoon.
The balcony shook as every tram or bus passed by, but the result was not bad. 30sec exposure done with an EOS 350D + Sigma 18-125mm.
Posted one day after I signed up for a flickr Pro account.
