Thursday, July 14th, 2016 at 7:57 am - - Cave

To distract myself on the underground camp of terror I stripped down my hang-glider logging device and took it down with a string of temperature sensors, barometer, humidity sensor and light cell and stuck it in a box in the corner with the string dallas temperature sensors extending out along the clothes line some ways from the tent.

tentdatalogger

The tent was a home made affair designed to be light and sleep four people. The fabric was slightly water resistant. There was immediately a condensation problem with cavers waking up in the morning with the sleeping bags soaking.

As a consequence people began leaving the front door to the tent wide open which meant that it was not a lot warmer inside than out.

analysispic2

Key: The red vertical lines are in increments of 5 hours, horizontal lines are increments of 1 deg C (when applicable). Cyan lines are the temperature measuring devices, some inside and some outside. Cave temperature was around 2.9degrees, while inside the tent it got to 5degrees in the early part of the night.

The four lumps of yellow on the lower line are from the light sensor and represent: (1) first arrival at camp and setting up the logger, (2) return to the camp after an afternoon of caving, (3) waking up in the morning, (4) returning back to the camp for packing up and leaving.

There is a sudden spike up in temperature when I dropped some of my spare clothes onto a sensor that I took off ready for the long climb out.

The upper red trace is the humidity x 0.1 and varies between 95% and 88%. The middle white trace is the temperature logged by the humidity sensor itself. The lower white line below the zero is the barometric reading, which spends its time around 88000millibars corresponding to about 1200m altitude.

Finally the yellow line is the dewpoint temperature, which varies between 2degrees and 4degrees.

Some condensation was briefly encountered when we first got into the tent slightly sweaty (and the yellow and white lines crossed over). For the first half of the night the dewpoint temperature differential was at about 1degree. Then someone woke in the middle of the night and pulled the tent door much wider open which dropped the humidity by 2% and the inside temperature by 0.75degrees, but the differential widened slightly.

I don’t know why the temperature varies so much during the night. Maybe it’s overall constant, but there are slight changes in convection currents that vary this. I should string the sensors all round the inside to see how it cross-varies.

It takes at least an hour for stability to resume when we leave the camp. Humidity rises as the temperature decreases.

Would the story have been different with a more porous tent fabric that could let out the water rather than one designed to be impermeable to liquids? If this was used we may have been able to raise the temperature inside the tent high enough to be clear of the dewpoint value, even though there is not much room below the 100% mark.

There should be a calculation of number of breathing and sweating bodies, the inside temperature and the and rate of exchange of air that provides for an optimal size and location of vent holes for the night. However, it’s difficult to find anywhere in the world that is this cold, humid and miserable for any experiments.

There are constant drafts around the cave which leave their mark in the rock formations. A set of barometers carefully synchronized, both outside and inside the cave, could produce an account of the total volume of the cave and its effective entrance surface area by modeling the flow of air molecules between these different reservoirs. This would tell you what percentage of the cave has been found. Experiments could be done on man-made tunnels whose dynamics are simple and volumes known. Higher frequency induced pressure changes might also be detected given that the bluefly is measuring at 50Hz.

Wednesday, July 13th, 2016 at 8:54 am - - Cave, Uncategorized

The weather turned caving, so I went underground two times. The first was to the shallow Balconyhohle (60m entrance pitch, then run around horizontal passages). There is a snow slope going up towards the surface that Andrew had a poke up.
balconsnow

Then someone showed me a demo of virtual reality using WebGL on a smartphone in a webpage, and I spent a couple of days coding the obvious idea I’d had years ago of putting all the cave data into a 3D model, using the GPS position and screen orientation to project it so that your phone acts like some kind of X-ray vision through the ground.

ssgroundview2

We used this to find a corresponding hole above the ground, which had a snow slope in it going down. It was a known hole in the database (identified by the metal tag drilled into the rock beside it) but with no record of exploration. Andrew looked at it the next day and couldn’t get down through. Later on he went underground again with a shovel and dug upwards as far as he could reach, but it still remained plugged.

Maybe if we rigged up some kind of a shelter over the hole to stop more snow falling into it, it could melt out in a few years. Something like some metal bars and planks of wood higher up to keep the new snow from getting out of reach of the sun so that the spring meltwater pours down and erodes away a bit of the snow plug each year.

Then, because I didn’t want to do much caving, I decided to go on the deep underground camping trip, which was far, far too deep with a lot of nasty scary rope rigging on the way down and up that kept me in a state of terror for hours on end. This is not as illogical as it sounds. Caving is horrible, and it takes many days for the memory of how horrible it is to wear off (like the memory of a very painful hang-over) before I am prepared to do it again. But once I’m down there I haven’t got a lot of choice.

Becka took her phone down to the camp (at -600m in Kraken chamber) and it took considerably better pictures than the fuzzy gopro I had.
camptent
There was a cross-over with the previous camping group, which is why there’s so many people in this image.

wookonkraken
This is one of them starting up the big loose pitch out of the chamber, which begins with a 60m freehang, and then lots of rebelays on a blank rock above a soily bouldery slope that you keep kicking stuff down from. As a consequence only one person can be on the rope at a time and it takes ages.

bigtunnel
The passages were enormous and we explored and surveyed about a kilometer of cave.

helicmud
There were some surprising formations, including this pickled gherkin sized helictite with a drip on the end that never quite fell from it, because the mud was untouched below it.

When we three finished our two days and one night stint, the next team came down and met us at the tent while we were stoking up on food for the horrendous climb out (lots of pathetic whimpering from me) and overdosing on our salt quota (according to the packet, the instant risotto meal for two I ate contained 11g of salt). Somehow on our ascent one of us pulled the rope up after us and accidentally hooked it over an isolated rock ledge well out of reach, which meant that this team were trapped underground until the full-expedition rescue was called out owing to them being overdue.

griefcloud
Luckily, Becka and me were miles away in Griefenburg by this time, with her on her new road bike, and me playing in the low clouds. The sad thing was my favourite pizza joint in town had closed since last summer, and the restaurant we went to instead was a bit crap.

Back at the expo the next day, Becka went straight up the hill while I attempted to get in another flight. It didn’t go too well, and I nearly crashed off the ramp, probably because I’d kept the nose too high without a headwind to guide with wing position. I barely got away with it and haven’t dared look at the photos yet. Not good memories to leave this place with.

I calmed my nerves for a couple of days by coding the groundwindow application and getting to know something about writing GLSL shader technology. It’s pretty stunning, and it makes the phone quite hot from all the computational power.

Saturday, June 25th, 2016 at 8:38 am - - Hang-glide 2 Comments »

I did it! I f***ing did! The mission to fly from the Loser to the Dachstein and back as mentioned in my Skywings article last year.

It was third day lucky. First day was a practice day, which somehow got me to Grimming and back in a four hour flight.

Second day I went for it because of a very good alptherm prediction, and fell out of the sky from 3000m to ground level in Bad Mitterndorf in a matter of minutes by attempting to punch through huge valleys of sink on my Sport2 due to stupidity, ignorance and nothing else. I misjudged the winds and there were no clouds to remind me where the thermals were — ie not in the valley.

On the third day alptherm gave an even crazier thermal forecast, the like of which I’ve never seen for this place.

alptherm2

I wonder what that german writing at the bottom says. Probably nothing important.*

I held back as two topless gliders took off at 12:30 and one of them went down. I knew 1:30pm was my magic time. The alptherm values are in UTC (add 2 hours for local time), so it really only starts cooking on at hour 1pm, before which it feels like there is a pause in activity.

And I went straight up to 3000m where the valleys and mountains are just minor details and threaded my way from cloud to cloud.

The sky gods sent the cunimbs onto massifs beyond all four corners of the flight and while the Dachstein gruppe remained miraculously clear.

Then it was off the the Grimming, arrived from the thermal hotspot to the east but unfortunately below its peak and was too intimidated to do any circling near this blasted mountain.
grimming

Luckily there were paragliders flying here and there to guide me and stop me from wussing out whenever it was feeling too extreme.
dachapproach
Was it a bad idea to go higher? There was a speck of a floppy paraglider up there in front of the cloud. Is it okay to fly over the 3000m peak of the Dachstein? There were two paragliders right down low over it.

How is it possible for something this amazing to continue? Just a set of simple wings on my back in this crazy place. This is an enactment Niven’s third law including commentary, which may predate the invention of hang-gliding:

3) Mother Nature doesn’t care if you’re having fun.
You will not be stopped! There are things you can’t do because you burn sugar with oxygen, or your bones aren’t strong enough, or you’re a mammal, or human. Funny chemicals may kill you slow or quick, or ruin your brain … or prolong your life. You can’t fly like an eagle, nor yet like Daedalus, but you can fly. You’re the only earthly life-form that can even begin to deal with jet lag. You can cheat. Nature doesn’t care, but don’t get caught.

I got there. There were big anvil clouds to the south darkening the whole horizon. This is the way I am going, across this sea of rock and snow back to Altaussee.
dachpoint

It was like a solid glide for 20 minutes, then a thermal off a corner buttress so I didn’t have to squeak through the Obertraun valley, then another 20 minute straight glide to the Trisslewand that had a huge cloud hat on that worked. There was nothing else between.

fromcampsite2
I decided to come down before anything went wrong and was actually able to phone the cavers sitting in base camp to tell them to look to the sky. They couldn’t hear me, so I texted them instead. Texting while flying is about as dumb as texting while driving, but the air was quite open at 2200m.

campdig
Becka cycled up and helped me carry down from my favourite landing field behind the campsite. I celebrated with a beer. It still gave me a headache. Back to earth. This is now the state of the campsite. The noise is awful.

* Translation: At the moment thunderstorm and precipitation symbols can’t be shown due to technical reasons.

Wednesday, June 22nd, 2016 at 5:46 am - - Cave

I cried at the state of the campsite in Austria when we arrived this year. It looked like part of the Amazon Rainforest — clearcut and still raining.
clearcut

The plan is to be here for about six weeks, and it’s not looking like a great idea. Only about a quarter of the people have arrived so far, and even the cordoned off area is pretty churned up. I pitched my tent on a gravel patch by hammering in nails to guide the tent pegs.

So, to cheer myself up I did some coding, and wrote stl2png, a program to slice STL files directly into PNG images for use with an SLA printer.

This is an example of a generated slice of the two chamber whistle someone has been printing a lot of in DoES.
V29D_Fixed_0003

(The wifi internet for the computer is pretty poor around here in the campsite, and there is no mobile tethering allowed when you are abroad, so I am unlikely to get much blogging done for a while.)

Friday, June 17th, 2016 at 1:48 pm - - Machining 1 Comment »

What was that horrible noise coming out of the closet at DoESLiverpool for about three days?

I was attempting to machine down one of these hold-down clamps so it could fit the 70mm wide type 2 vice I’d bought recently.

My earlier attempts to clamp the vice down on two points failed when the bolts rattled loose and the whole thing started being dragged back and forth across the table by the milling cutter. I decided was going to require at least four points of attachment to work, and these neat little clamps looked just the right shape — except for the problem of being slightly too tall.

(That current configuration in the picture was an idea Andy came up with at the last minute when trying to solve this problem.)

Andy had tried to skim them down on his lathe and told me that the metal was too hard. But I was determined to prove that anything could be done if you took little enough cuts. In this case it was steps of 0.1mm per layer and 0.5mm across

At 8000rpm there were sparks. These didn’t happen at 6000rpm. I was running with a 5mm 2fluke flat bottomed tiain-coated carbide tool. Furthermore, the conventional milling sounded marginally less nasty than the climb milling passes. I’m surprised nothing broke, though I don’t have the experience to tell whether a tool has worn out or not.

The result was pretty crap. Instead of performing some clean cutting, it seems like some of the metal was simply bashed flat and pushed out to form a lip around the face.
flatcut
I didn’t know that metal would have the propensity to produce this result when undergoing milling.

It’s not a factor accounted for any software I’ve heard of.

I’ve written many algorithms that detect the horizontal flat faces of a part and create toolpaths to skim them out, but no one has ever requested a subsequent pass just below each open edge to clean off the burr left over.

Sadly, there won’t be any more machining for at least six weeks as I’ll be in a rainy campsite in Austria waiting for the chance to fly. At least this will give me lots of time to try and write some useful code when I’m not washing pans or carrying rope and other provisions for the cavers.

Friday, June 17th, 2016 at 12:03 pm - - Whipping

I went to the International Festival for Business down at the Liverpool docks to see a presentation on the funding competition for 3D printing by InnovateUK yesterday.

I was quickly trapped in a dark room full of suits as the Government man painstakingly powerpointed his way through the process by which they were going to hand over several millions of pounds to the sorts of respectable businessmen who ultimately don’t give a damn if the technology can be made to work productively or not, because the underlying purpose of their job titles is to extract financial profits for themselves as the primary objective.

That is the very definition of a respectable businessman these days. It’s not ever defined as someone with the character to manage and inspire the teams of technologists who would have the capability to deliver the technology, or a preparedness to use finance in the service of these ends rather than as an excuse to impose inefficient and ineffective research and development methods onto any program they control.

Back in the old days when the Government wanted some new technology developed, like nuclear weapons, space travel or machine tools, people sought out and spoke to the engineers who were ultimately going to have to do the job, and then designed programs around the necessity of organizing these engineers to get it done as efficiently as possible.

If their one idea is that people like me have to be subserviently employed under a contract to deliver closed source software for the know-nothing suits they’ve deliberately empowered to curate this technology by virtue of proving them the grants, then it’s going to be a disappointment.

I walked out to the main hall where FW de Klerk was being introduced prior to his speech.

deklerk
(more…)

Monday, June 13th, 2016 at 2:14 pm - - Kayak Dive

I haven’t dived near Skomer since 2008 when we arrived just after Bristol University left a day early, having been drenched by the rain. This time we successfully caught them on the last day of their trip and tagged on for a dive on the north face of Tusker Rock in Jack Sound, which is known for having a very short slack window.

tusker1

We paddled out there for the dive at 1:10pm, but the Bristol boats didn’t show up from around the corner till 1:28pm — very late. Everyone blamed everyone else for the faff, and I didn’t feel confident with going in here at this crazy place alone without being really sure we got the place right. (The north flowing current is menacing as it descends down to 50m as it leaves Jack Sound.)

tusker2
Bit blurry, but there’s a dogfish swimming past Becka

tusker3
Rather too soon, we got washed off the rock by the south flowing current and had to come up.

We had an excellent extra dive in the calm waters of Martins Haven where the scallops were stacked like bricks (apparently there’s a fine of £50,000 if you’re caught taking one of them). Lots of lobsters, spider crabs, and nudibranchs. The camera was of course out of battery by then.

Next day we headed for Octopus Reef on Dinas Head, where I’d met Red Dragon Divers on a sea kayaking trip in 2012. This was a chance to tick that one off, although the visibility was very poor from the plankton bloom. Becka found the octopus on the first dive, after we’d fallen off the reef onto gravel and were swimming round in circles at 13m. Spent the night in Parrog (where we’d kayaked from), too flaked out to go to the pub.

Final day had us paddling out of Gwbert by Cardigan to Cardigan Island to try and dive the SS Hereford. Unfortunately, the westerly swell was picking up quite a bit, so the sea was a little crazy out there and not a great place to try a dive on a shallow wreck. So we dropped in round the corner in the sheltered waters that was very much in its pea soup stage of plankton (little green translucent peas of algae everywhere), bothered a few lobsters, dogfish and spider crabs, before paddling onwards to Mwnt visiting all the sea caves in the coast. The carry-out was not as bad as it looks in the photo.
mwnt

Becka left me at the tea shop while she walked back to fetch the car. The lady running it explained that the dolphins can normally be found off the north end of the beach, whenever you see a gannet flying there. She guessed they were driving the fish into a sand-bar, and the gannet was picking the ones off that came to the surface.

We can check it out next time we go down there and have a third attempt to do the Hereford wreck when we are sure the sea state is calm enough to make it worthwhile. Kayak diving wins again.

Friday, May 27th, 2016 at 12:07 pm - - Flightlogger

The datalogger is fitted to the right hand upright of the control frame. According to my shoddy measurements the upright is 176cm long and the basbar is 138cm long. There are two wires from the corners of the control frame to a point on the keel 151cm forward, each of length 206cm. And there are another two wires to a point on the keel 80cm backward, each of length 205cm.

This seems to add up to a vector of (69.0, 42.06344442205491, -156.2492943010685) from the top of the control frame to one corner of the base bar, which is the alignment of the datalogger and its BNO055 orientation sensor strapped to the upright.

I definitely don’t have time for a complete blog record of this, and a lot of it isn’t working, even though I’ve spent no end of time hacking on things, but if I plot the logger vectors that go backwards and perpendicular to the upright on the gps track, I get this picture:

keelorientation

For scale, the red lines are 11m long and the plot rate is 3x on the 100Hz samples, so there are 33 of those lines per 1second of motion.

It’s reasonably smooth and consistent, unlike the accelerometer values, which I think represent a lot of vibrations in the system, if the creaking wicker chair-like noise on the gopro soundtrack is anything to go by. It’s about right, if you think of the airspeed being in line with the keel of the glider (which it is probably not, because of the yawing and side-slipping in turns).

I nearly bought a sonic anemometer second hand off ebay last week, but missed it. I’ve got an alert watch on a new one and have designs on fitting one to the top of the kingpost where it is out of the way and least likely to get damaged by flying into a hedge or the ground.

Regarding the kinematics of the system, every part of the flight is the same as everything else, so I can strip out the simpler bits to see if there is a relationship. In particular, this is a plot that claims to be 10 second long sections of the flight where the bank angle is less than 3degrees.

nobanksections

This doesn’t fit too well, and I can explain it that the calibration value on the device was at 1 out of 3 for most of the flight, in spite of starting off on the ground at 3/3, so it’s telling me it got it wrong.

Anyway, it’s straight enough to move on to this complex plot of some of those flight sections:

pitchsections

Time goes from left to right of about 10 to 20 seconds. The following traces have been displaced close to the zero horizontal white line so you can see their correlations, if any. Green is pitch angle, Yellow is smoothed acceleration in forward direction (approx because it’s not aligned with gravity yet), Red is airspeed, and White is differentiation of windspeed.

What I would hope for is a delayed correlation between pitch (green) and airspeed (red). If you push the nose up and hold it there, the glider will slow down, and then fly at a slower speed. If you pull the bar in and hold it there, the glider will speed up and then fly at a constant higher speed. But of course you’re moving the bar all the time. But you can almost convince yourself of the response; the green line goes down, and the windspeed then starts to rise, and vice versa.

This should be built this into a kinematic model of control and response. It would actually also align with the barometric reading, where the sink rate goes up with a higher speed, so it’s quite 2 dimensional in the vertical plane, with energy equations.

The other correlation should be between the forward acceleration and the derivative of the airspeed. Both the airspeed signals and the acceleration signals are quite full of noise, so they needed to be smoothed (I think I’ve done this incompetently here, but that’s for another fortnight of coding).

Here you would expect a direct correlation in still air, because if the accelerometer says I am accelerating at 1metre per second per second, then over the course of 2 seconds my absolute velocity will increase by 2 metres per second. And, if the air is still, then my measured air speed should also increase by 2 metres per second.

So these two ought to be scaled the same. Except the smoothing flattens out all the humps and troughs, so you really can’t tell what the absolute value of anything is from this anymore.

Some of the bumps seem to line up, but this is not adequate for a kinematic model.

The numbers get hairier and hairier as I try to approach something useful. And that useful thing would be to separate the absolute motion into that which is due to my control and the flight characteristics of the glider, and that which is due to the underlying wind speed and direction.

Accordingly, I should be doing lots of boring flights in completely still air at the start of the day with a working logger where everything is calibrated, rather than having lots of fun in thermic air. This is a job to do in Austria where the hills are high and I should have hours and hours in the campsite not coding on other things.

This work just takes so much time and has hit so many technical failures already that I doubt it could be done by someone who is answerable to a boss.

Wednesday, May 25th, 2016 at 1:05 pm - - Machining 1 Comment »

You know those clamps for the vice I was so pleased about fitting?

Well, they slipped out while milling metal due to all the vibrations during helixing.
loosevice

This just after I’d spent all afternoon compensating for the rotational position of the vice to withing 0.04mm across 50mm of its width by probing a piece of metal in the jaws wrapped in a piece of wax paper to electrically isolate it from the vice.

Bog! That’s ruined my day.

And the weekend is going to be rubbish, waiting in a tiny cold tent in Yorkshire for the fog to clear.

Wednesday, May 25th, 2016 at 12:58 pm - - Hang-glide

This was Sunday (yesterday) on Tailbridge Hill while Becka and friends were attempting some 80 mile massive cycle ride including a race up Great Dun Fell (844m), somewhere square in the middle of that dark grey wall of rain and hail to the north of me.

tailbridge

They didn’t make it. I suspected that something bad could happen in that area on an otherwise sunny day because of the RASP forecasts:
dunfellrasp
They were to the NE of Kirkby Stephen in the blue, and I was to the SW in the place with the nice thermal updrafts. I already knew no one was interested in my weather observations if it could lead to a change of plans, because they’d all been on a futile journey walking up a hill to a flood-prone cave on Saturday when I knew two strong cold fronts were predicted to pass overhead and make everything miserable.

I got into my own spot of hail up at the clouds at 1300m over Mallerstang Edge late in the day, and it was nice witnessing this three-dimensional field of white pixels streaming past.
mallerhail

I don’t have time to edit any video, so here is a video with a bit of hail in a flight last month from Builth Wells.

I had to do a better landing yesterday, because in Yorkshire the field boundaries are made of rocks.