Personal Website of Julie and Lance

Intended for our family and friends: to keep them up with our adventures



Julie and Lance’s Ideas to mull over:



Ideas list: click on the hyperlinks>


Click here to jump to Lance’s Engineering Geeky Tools (mainly electronics oriented)


General Interest Stuff (click the links below):


All Things Carbon (Controversial idea regarding carbon-credits)


More Miles to the Gallon (Getting more miles from your car's tank of fuel)


Block Paving - Stopping Weeds in the Joints


Extra Security for your Credit / Debit Cards


Domestic Fuel-Oil Price Calculator



Wood Burning Stove:


If, like Julie and I, your thoughts about reducing your carbon footprint resulted in buying a wood burning stove, you’ll be a bit peeved by the recent ‘bad publicity’ about wood burners. Trying to do a good thing can be difficult! The problem, I believe, is the burning of wet-wood: wood with water content more than 20% can result in inefficient combustion; soot produced flies out of the chimney and into your local environment. These pollutants can bring about and/or make worse respiratory disorders. So it’s really obvious why we wood-burner folk should take care.


I was wondering about kiln-dried timber. It seems perverse: using energy to force-dry timber so that it can be ‘legally’ used in a wood-burner. However, that said, is there really any benefit in kiln drying when we have to store the timber outside?


It is surprisingly difficult to measure the water content of wood. The only ‘true’ way is to extract all of the water from a known weight of log (initially wood plus water) and weigh the dried wood and weigh the water. If you find that your 1kg log turns into 500g of dry-wood, i.e. it has lost 500g of water; the log was 100% humid. Therefore the ‘legal’ 20% humid 1kg log will be 833g of wood and 167g of water.


The Hailwood-Horrobin Equation empirically estimates the degree to which wood absorbs or releases water from/to the environment. In the UK the annual average relative humidity of the outside air is around 80%. Your actual location in the UK doesn’t impact, to any great extent, this 80% figure. However, different parts of the UK have quite different annual average temperatures, and it is this fact the H-H Equation can help predict our stove-timber humidity. Where we live, Fife, the annual averages for temperature and relative humidity is 8degC and 80.4%, and from the H-H equation we find that stored timber will finally settle at around 15.25%. Therefore there is little point in kiln-drying timber to less than 15%.


There are good and bad ways to kiln-dry timber. The most environmentally conscious way is to use photoelectric solar panels to power a heat-pump dehumidifier. If you can be sure that this is the method used by your wood-burner logs supplier, then go for it. But, in all truth, naturally seasoned logs are just as good. All wood left under-cover outside in the UK will eventually reach 15% humidity.


Click <here> to download a spreadsheet file. The calculator(s) is in the form of an Excel Spreadsheet, and should function in most computers and devices.



Domestic Fuel Oil Price Calculator (28-second Kerosene):


These days it is very easy to compare gas and electricity prices on the web. When it comes to buying domestic heating oil, as we do here, it's not always so easy to get the best deals. Over several years I have analysed how the price punters pay for home heating oil varies with the time of year and the price of crude oil. The calculator here gives you a starting point for negotiating (if such a thing is possible) with your oil supplier.


·        Never accept the first quote: best to shop around

·        Always ask if the quoted price includes VAT

·        Always ask if the quoted price includes delivery

·        And if you are paying using a credit card, ask if there is a charge for doing so


Click <here> to download a zipped file. The calculator is in a document file that should run on Microsoft Word (part of Office). It contains active content, therefore you may receive a 'warning' to authorise active content: click to accept. Some of the content is specific to Dundee, but the prices calculated are of the UK as a whole.



Extra Security for your Credit / Debit Cards:


If, like Julie and I, you have had fraudulent charges to your credit card you might like to try this simple method of improving security. There is a fundamental security weakness in handing your credit card to, say, a restaurant waiter (or any other occasion where you hand your card over to make a payment). All the details that are needed to make 'non-signed' or 'non-pinned' (aka card-holder not present) payments are in full view on your card. In other words, if someone had your 'long number', the 'expiry date' and 'the last three digits on the back of your card' that person can pay for just about anything on the web using your card details! Going back to the waiter scenario: it struck me that there are a number of occasions where harvesting the necessary information from a credit (or debit) card is possible, and that having all of this information on the piece of plastic is just asking for trouble.


What we have done is to write down the last three digits of our credit / debit cards on a piece of paper, and this piece of paper kept secure in our wallet / purse: never shown to anyone. The last three digits on the back of the card are obliterated. When it is necessary to quote the last three digits, you have them written on the piece of paper in our wallet / purse.



Block Paving - Stopping Weeds in the Joints:


We have large areas of block paving, and we've tried all sorts of proprietary weed killing and cleaning products. By far the cheapest, and efficient, method is to use dishwasher salt. Completely dissolve 1-1/2 lbs (700g) of dishwasher salt in 2-gallon (10-ltr) bucket of water, add a dash of liquid detergent, and brush into the paving. No need to brush too hard: just spread the mixture evenly across the paving - a bucket does about 150-square-feet. Choose a time when the weather forecast is for a few dry days: rain would undo all of your effort. In about one-week you'll see those pesky weeds going brown and dry!



More miles to the gallon (or should that be km to the litre):


There are several web-blogs discussing the efficacy of coasting a motorcar (i.e. your car is moving without the engine being engaged, the engine running at tick-over). The very first thing to be stressed is that British law requires you to drive safely, and obey all road traffic laws. As an academic question, however, is it correct to say that coasting will reduce your fuel consumption by any meaningful amount?


All models of motorcar differ in their efficiency: they have different streamlining (some cars are better than others of passing through the air), they have different frictional losses (in the bearings, gearbox, and other mechanical bits-and-bobs) and they have different rolling resistance - but that is a quality of the tyres fitted to the car. If a car is stationary with the engine running, it is obvious that you are getting zero-miles to the gallon. With the engine ticking-over there is a small amount of fuel being used to keep the engine running: it's not much fuel, only about one-fifth of a gallon per hour. It is a small, but meaningful amount, and cannot be reduced if the engine is to tick-over with the car stationary.


Everyone is very aware that their car will roll downhill, with or without the engine running. What isn't so widely known is that the speed a car will achieve rolling down a hill with a known slope is proportional to the square-route of the slope. As a very rough-and-ready average, a car freewheeling (i.e. engine on tick-over with the clutch disengaged) will achieve a speed of three times the square-route of the slope (V = 3xSQR(s)), where ‘V’ is miles per hour, and‘s’ is the slope in feet per mile. (And for those folk with metric measure V = 11xSQR(s), where ‘V’ is km per hour, and‘s’ is the slope in m per km). So if the hill has a slope of 100ft per mile, the average car will achieve 30MPH freewheeling down the 100ft/mile hill. A slope of 100ft/mile is not steep; it's a little less than 2%, or around 1 in 53.


The two figures above (one-fifth of a gallon per hour and 30MPH) immediately allow you to deduce a meaningful miles per gallon: 30MPH and 1/5-gallon per hour is 150 miles to the gallon. So if your car is freewheeling down a hill of 100ft/mile, you will be travelling at ~30MPH and have a fuel consumption of ~150 miles per gallon. It is often stated in blogs that modern engines shut the fuel off completely when going downhill with your foot off the throttle and the engine engaged. This is true, but in the example here if the engine were engaged, its frictional losses would further reduce the speed that the car would achieve on the quoted slope of 100ft/mile. Therefore, instead of 30MPH the car might only achieve 25MPH, due entirely to the frictional loss of the engine - but at least you would not be using any fuel!


The bottom line is, of course, what speed do you desire your car to move at? You have to conform to legal speed limits, and in the example above (which could well be a hill of 100ft/mile with a speed limit of 30MPH) you would not necessarily wish to drive at 25MPH (unless particular conditions dictated a lower speed than the legal limit), therefore in order to maintain 30MPH with the engine engaged, you would have to apply some throttle - in other words the fuel cut-off of modern cars is rendered useless.


There is a very simple rule-of-thumb to apply: if you are going down-hill in your car and you have to break to keep your speed legal (or as desired) then it is better to have the engine engaged. However, if you are going downhill and your speed is what you want it to be without the engine engaged; you are going to save fuel by keeping the engine disengaged. To test this whilst driving, dip the clutch, and if your speed is maintained as you wish, keep the clutch dipped. You must drive safely and legally, of course, but using this technique can save you around 5% of fuel without having to change your drive speed habits.




All things carbon:


We have all heard of Carbon Credits: where a country, or company, with a lower discharge of carbon dioxide than the target level can sell their un-discharged carbon to a polluter discharging carbon above the target level. Well I reckon that these carbon credits should also be available to individuals who discharge less carbon dioxide than a target figure.


We all discharge carbon dioxide whether we like it or not - even breathing is an act of pollution! And try as we might we will probably never be able, as individuals, to be carbon neutral: we have to heat our homes at times, we have to eat to live and this food has to be produced, packaged and transported to us, we will probably never be able to live without transport of ourselves and the things we consume. However, within our scope of choice, we can all choose to do some things and not others, and thereby choose to reduce our individual contribution to carbon dioxide pollution. Ultimately we are all able to choose, to some extent, the amount of carbon dioxide we are responsible for.


Each and every one of us is born with, in effect, this pollution contribution already allocated to us by simply being born! It is a fact that between 1959 and 1995 the world's population increased from 2.5 billion to 5.6 billion people.


It is surly obvious that if the world were not populated by 8-billion (or so) people we, collectively, would not be discharging as much carbon dioxide as we are. And that, consequential to the choice of bearing offspring, a person that has chosen to have children has also chosen to contribute considerably more carbon dioxide than those people that choose to remain childless. If a couple choose to have two children, then that couple have also chosen to discharge twice the amount of carbon dioxide. For an average person consuming the average amount over an average lifetime, that average person would find it very difficult to increase their personal contribution to atmospheric carbon by two times - except that is, by choosing to have a child.


People choosing not to have children should therefore be rewarded (with carbon credits) for making such a choice, and be able to sell their lower than average carbon footprint to someone who, by their choice, has chosen to double, treble, etc., the amount of carbon dioxide they could ever contribute as an individual.


Current world population (estimated): .


Some of my home-grown engineering tools and calculators (most have active content requiring MS Office):


Home Heating Tools: Calculation of Wall insulation R-Value, Dew-Point and Wood Water content in Spreadsheet form – should run on all computers


Balun Calculator: Calculate (requires MS-Word) forward and reverse impedance as well as ideal balun – more flexibility than your average on-line calculator!


Serial to Parallel Impedance Convertor: Circuit Impedance Transforms made easy with this calculator (requires MS-Word).


RF Skin-Effect Calculator: Calculate the effective resistance of a wire conductor at high frequencies (requires MS-Word).


Fresnel Effect Calculator: Calculate the effect of the Earth on RF propagation (requires MS-Word).


Square-Wave Harmonic Frequency Calculator: Calculate the maximum harmonic frequency in a square-wave (requires MS-Word).


Bandpass Filter in Sallen-Key Calculator: Calculate the passive values in an op-amp-based bandpass filter (low frequency).


Q of Sinusoidal Decay: Calculate the Q of a tank-circuit using its decay ratios (requires MS-Word).


R-Value Calculator: A simple to use calculator (requires MS-Word) that approximates the R-Value of a wall using just three temperature measurements. This is best used with a radiometer thermometer; often to be found in the central isles of Aldi!


Dew-Point Calculator: Calculate the dew temperature from relative humidity and temperature (requires MS-Word).


Exponential Growth and Decay: Calculate the Time Constant and Asymptote from three data-points (requires MS-Word).


PSU to mS/cm Calculator: A calculator that runs a grunt-code inverse function of the classic PSU equation (requires MS-Word).



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