Millstones, not around my neck

Posted by atomicalex on 2012-03-11
Posted in: Tribology. 1 comment

I rode out to Kalkar Mill on Saturday afternoon to check out the stones. Kalkarermühle is an operating windmill in Kalkar, NRW, Germany, and home to a diverse bunch of people who have decided to keep the windmilling trade alive as volunteer millers. One of the millers is a friend and fellow rider, and introduced me to this neat old technology last fall.

The key to the mill is the stone set. The lower stone, shown here, is fixed and does not move. The upper stone is supported on a pintle that is driven by the familiar sails that catch the wind and power the operation. The entire rig runs at around 120rpm, which is quite speedy, considering that the stones are about 1.6m in diameter. That comes to an edge speed of 24m/s! When the season for milling is low (winter), the millers open the stones for cleaning, resurfacing, and rhynd repairs. On this stone, the darker areas are the wear surfaces, and the grooves are the feeders that feed the grain in.

Fixed stone from Kalkarermühle

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Nordic versus Alpine

Posted by atomicalex on 2012-02-23
Posted in: Style. Leave a Comment

Sun on the bunny hill

 

 

 

 

 

 

 

 

Nordic skiing has a lot more to do with Alpine skiing than skateboarding does with snowboarding.

I traveled to Willingen, a town in the Sauerland area of Germany, to further my skiing abilities, and for the first time, skied fully in parallel, executing pretty stem turns and schussing down a moderately steep piste. Four hours of lessons produced a recognizable and functional technique that could get me safely down the slope with good control. By the end of the weekend, I could ski comfortably, avoiding oncoming traffic and the hundreds of Dutch children covering the bunny hill. I even ventured up the Seilbahn (gondola lift) to take on the big hill. I fell once, sliding due to a bit of fear (my survival reaction is to lean backwards, a quick way to lose control), but no harm done. I seemed to have learned how to properly fall in the process, too.

The instructors both made a good point: I was not a beginner skier. Unlike instructors in the US, who pooh-poohed my hundreds (if not at least a thousand) kilometers of Nordic experience, the Germans were quick to describe each Alpine technique in Nordic terms. This was a confidence boost and made it easier to adopt the new technique of pushing the tails wide (stemming).

I expect I’ll be skiing through the summer, over at the Skihalle in nearby Neuss. Yes, it’s a bunny hill, but I see no reason not to own it, too.

Cure the Symptoms, Cure the Disease?

Posted by atomicalex on 2012-01-28
Posted in: Automotive, Motorbikes. Leave a Comment

It’s one of my favorite literary lines ever, from Michael Crichton’s The Andromeda Strain. The scientist in question is pondering whether successful treatment of the symptoms displayed by his patient means that the disease causing them is actually cured.

So it goes with electronic diagnoses involving logic boards. Stray voltage at one pin results in a strange signal at another one. The voltage can have three sources, but which one is it?

For example, a artificially high (500rpm) tach reading on an F650GS that remains after shut off for several seconds. Coupled with poor running/starting. Symptoms occur only when bike is started wet after cold rain. Brought up to running temp and restarted, the problem is gone. Signal path is a single star circuit of the ECU, the #1 coil, and the tach signal feed. Diagnosis starts with check air and fuel to rule them out for the poor running aspect. Both are fine. Second step – pull plugs. As expected the #1 plug is funny looking, not bad, but a bit pink on the insulator. The primary resistance on the coil is a hair high when the coil body is wet.

Is this a symptom, or is it the disease? I’ll find out when I pull the tach apart. I hope.

Motronic Malfunction, part 2

Posted by atomicalex on 2012-01-13
Posted in: Automotive, Motorbikes. Leave a Comment

All my life, I’ve been pretty good about patents and trademarks. So I’m a bit confused as to why BMW isn’t. The “Motronic” in my bike is actually a Hella product called BMS, as I just learned from the FAQs over at f650.com. This explains a great deal about why it bears so little resemblance to a modern Bosch engine management system, even as it bears resemblances to pieces of so many others.

Did I say anything about wanting to learn a new EFI control codec? No, I did not.

Motronic Malfunction

Posted by atomicalex on 2012-01-13
Posted in: Automotive, Motorbikes. Leave a Comment

edit – when I wrote this post, I was under the impression that Motronic meant Motronic. Not to BMW, who call any engine control unit Motronic, regardless of whether they are violating Bosch’s trademark rights or not… See above.

I am a card-carrying K-Jetronic girl. When I first discovered K-Jet-E in my 1982 VW Rabbit Convertible, I leaned back in awe and remarked to myself that this is how I would do fuel injection if I had to: I would take apart a carburettor and distribute its parts liberally around the engine bay, making sure that each had its place and did not interfere with the others, all being individually adjustable and controllable (einstellbar und kontrollierbar, auf Deutsch). Just like K-Jet. I regard K-Jet as one of the peaks of elegant engineering design, and certainly one of the coolest systems to ever leave the halls of Robert Bosch Gmbh. It is also simple and easy to work with, provided you understand the basics of air/fuel ratios and a few other odds and ends about ICEs, of course.

I can’t say the same for Motronic, Bosch’s “modern” EFI control system. I’ve been watching a weird problem on my bike lately, and I’ve tracked it down to what looks like a bad hack job over in the Motronic design group. Not content with just supplying a modern, 2004 version of Motronic, it appears that Bosch decided to crib together the lousy parts of Motronic (signals taken from only half of the system), an interesting part of K-Jet (running the whole thing off the coil sense), and who knows what from Digifant.

The problem manifests itself as a flat 500rpm lift in the tach signal when it rains. Being Motronic, the tach signal is fed from the coil sense, but only from one of the two coils. The Rotax engine is known for some assorted issues (other than being a bullet-proof, workhorse, dinosaur of a fuel-efficient and otherwise great motor), one of which is pretty serious surging. Well…. imagine that. When your injector circuit is being driven by a feedback loop from half of the coil circuit, and voltage is building up due to phantom capacitance somewhere, yeah, the poor thing is going to surge like crazy.

So, I’ll be spending my weekend working on the bike with the only tool you need on a Motronic machine: my DVM. This is not what “working on the (insert ICE-equipped vehicle)” is supposed to mean, Mr Bosch…..

Lubrication considerations in wet steel wire drawing – InterWire 2004

Posted by atomicalex on 2012-01-09
Posted in: Chemistry, Tribology, Wire Drawing. 1 comment

Much more important than people realize, your tyres are riding on this wire…

From my presentation to the Wire Association International in 2004. Still the most wonderful, talented group of engineers I know.

Lubrication in steel wire drawing operations generally brings soap powders to mind. For larger wires this is uniformly the case. The soap powder melts in the wire/die interface and provides a viscous film that supports the drawing force. The fillers and additives in the drawing soap impart polishing, extreme pressure, and many other properties to the lubricants. As wire sizes get smaller, the soap powders become unsuitable for high performance drawing. The viscosity of the molten film is too high, and the film occludes the hole, reducing the wire diameter and eventually breaking the wire. Additives may corrode the wires causing breaks. The polishing aids and other particulate materials may be drawn into the wire, weakening it and resulting in failures. Wet drawing lubricants are required to overcome this problem.

Wet drawing lubricants are based on water and/or oil and have considerably lower viscosities than the molten soaps they replace. This reduces the film thickness and the chances that the film will occlude or block the die orifice. Wet lubricants do not contain particulate materials, so foreign inclusions are not drawn into the surface from the lubricant. The additive level is much lower in a wet lubricant and can be controlled by dilution. The wet lubricants also provide cooling to the operation, a feature absent from dry drawing operations. The wet lubricant requires different maintenance techniques than those required for dry soaps. A comparison of the two types of wet lubricants and their individual requirements for usage will be presented.

Ever wonder about steel rolling? STLE 2004

Posted by atomicalex on 2012-01-09
Posted in: Chemistry, Tribology. Leave a Comment

Abstract from my 2004 presentation to the Society of Tribologists and Lubrication Engineers….. Probably one of the best papers I have ever given, and winner of the Deutsch award for practical tribology research. That was a big day for me!

Predictive testing of Steel Rolling oils using the Elastohydrodynamic Lubrication Rig

The rolling of steel sheet from continuously cast slabs and coils or ingots to sheet and tin products is a fundamental step in the manufacture of goods worldwide. Slab and sheet reduction is accomplished by plastic deformation of the slab using large metal rolls to apply a force normal to the slab. The contact area between the roll and the slab/sheet must be lubricated to provide proper sheet finish and good tool life. Rolling operations are very large, and it is difficult to test the performance of rolling oils on the mill due to the volume of lubricant and the set-up times required. Development of reliable predictive testing methods is critical for the design of good rolling lubricants.

Rolling oils are typically formulated from fat and mineral oil basestocks with appropriate additive packages and provide hydrodynamic and boundary lubrication to the roll contact. The rolling contact is formed by the plastically deformed sheet and the roll and has three specific zones – the backward slip zone, the neutral point, and the forward slip zone. In both of the slip zones, fresh metal surface is exposed and the process operates in a slip condition. At the neutral point, the contact operates in a true rolling condition. This suggests that a test method with variable slip is for testing and evaluation of rolling lubricant performance.