Plummet
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Everything posted by Plummet
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Now who said it is good weather for trainers to take to the air? Plummet
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Sore and soarer. Plummet
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Accident prone Plummet
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Another vote for Modelfixings. But I have found that the Aldi or Lidl special buy tools seem to be good and good value. Try a good local engineers supplies merchant. Plummet
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I made some wheels for a smallish model by sandwiching some thin fibreglass between balsa sheet . I drilled out the centre and inserted a bit of brass tube. I mounted it on some threaded rod and spun it in a drill while sanding it to shape. I made a groove around the rim to take the tyre. I got a length of circular section neoprene sealing strip, cut a suitable length of it, and butt glued it with cyno to make a circular tyre. Plummet
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From the school of "What could possibly go wrong" **LINK** Plummet
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David, At the top of the fuselage plan sheet there is the text "Single wing joiner of 10 swg wire in 4 1/2" long drinking straw wrapped in tissue. Then on the wings part of the plan of the centre section it shows the drinking straw in position against the top spa. The rib section shows 6 ribs with a hole for the straw. The drinking straw is not "structural" it just acts as a guide to make sure that the wire joiner goes into the correct position through the holes in the ribs. The old drinking straws were made of waxed paper, and would be difficult to glue, so wraping them in tissue would make them gluable, while the straw would resist the glue, and stop the wire being glued in as well. It suggests that you build the entire centre section in one piece so that it is nice and straight, and then carefully cut it in two halves (remembering not to knacker the scalpel blade by trying to cut the wire as well). Does this make sense? Nowadays a piece of carbon fibre tube might be a better bet. Plummet Edited By Plummet on 30/03/2019 18:28:59
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Look at the indoor electric models. They are ultra light, but they have full house radio control. All you want is a single channel that activates the dethermaliser. Their receivers are ultra light, as are their servos.. Is this the way to go? Plummet
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Another thought comes to my mind ... It is a good idea to make sure that a burning fuse does not make contact with tissue and dope covering. One of the constituents of dope is nitro-celulose, which is chemically the same as guncotton or the flashpaper magicians use. Otherwise the results might be spectacular. Plummet
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Posted by david miles 7 on 21/03/2019 15:00:12: Hello Everyone. This is my first post. I have just downloaded the plans for a Frog Diana 36 inch wingspan glider. I notice that there is a "string fuse" at the end of the fin. Can anyone tell me what it is for? This is my first attempt at building a model glider! Thanks for any help. David Miles. Just for completeness, the original question asked what is a "string fuse". I have skimmed through the answers and I don't think (I could be wrong - if so, sorry) that anyone has answered this question. The string fuse is a piece of string that will smoulder, without going out, and that will burn at a fairly predictable rate. For a dethermaliser the tailplane is held down with a rubber band. The string fuse is lodged in between the strands of the rubber band and it is lit before the flight. It smoulders, and when the burning part reaches the rubber band it breaks the band, and another rubber band pulls the tailplane up to an angle where the glider stalls and decends quickly. When I was a kid I used to make string fuse by dissolving some saltpetre (potassium nitrate) in water, and then soaking cotton string in the solution. Take out the string and let it dry. When you light the string it may burn, but if you blow out the flame it will continue to smoulder. (The saltpetre reacts to the heat from the burning string by breaking down and releasing oxygen. This helps to prevent the smouldering going out. Saltpetre is used in gunpowder for the same purpose, so you may get funny looks if you try to buy it nowadays.) The string should burn at a steady rate. Test a piece of it to calibrate how long a piece you need. Plummet
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If I rig an electric fence around my plot then it is more likely that it would be to deter (cook?) the sweet little (I don't think) bunny rabbits with which I have to attempt to share my vegetables. Plummet p.s. I know that I am not the speediest person around, but I can still overtake one of the onions. Edited By Plummet on 17/03/2019 17:53:31
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Off topic ... ish ... I sent away for some special unusual onions. (Variously known as Tree, Egyptian, or Walking Onions.) The company were selling one onion plant, but they promised to send four, so that there was a good chance that one would survive. When they arrived there were not four but seven. I planted them all, and six out of the seven are growing. Plummet
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Posted by Charles Pic on 11/03/2019 12:08:09: After ten days, only 1 of my 6 seeds had sprouted. So that one has now been planted into a small pot. Not sure if the others are going to do anything so I have started 6 more seeds in damp kitchen paper. I did just realise though that I’ve omitted the “fridge for 24 hours” stage from the latest batch of 6. Will have to wait and see if they sprout anyway. Chilli seeds need to be kept warm to germinate. **LINK** The web page above suggests above 20 C. This only seems fair - we keep them warm when they are little, and they provide heat in return when they have grown up. I have also read that germination may take 10 days or so. Plummet
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Posted by Geoff Sleath on 02/03/2019 17:14:02: Rubber bands are very useful but when under tension tend to perish. I've no idea why and 'O' rings are the same. I use them on the long pins that help to fix the interplane struts on my DB Moths and keep a bag of spares in my tool box. The ones in the bags don't deteriorate at all. So keep a few spares to hand. Geoff UV light. Rots a lot of things. You can buy fine silicone rubber tube. Cut a length and tie it into a loop. It lasts a lot longer than rubber. I acquired a skein of it that was surplus to requirements many years ago and have been working my way through it slowly. Plummet Edited By Plummet on 02/03/2019 17:39:06
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Posted by Don Fry on 01/03/2019 11:58:42: In SW France, coriander is like gold dust. I've never been able to grow it, but I'm a rubbish gardener. Any ideas? I have not tried growing it, but some years ago we knew a lady who taught Urdu. She grew it well. This was in Bradford, so the climate is not like SW France, but she just planted a few seeds in a row. They grew quickly, and was soon ready to harvest (the leaf - that is) so she had to make a series of successive sowings in order to keep it available. The bit of land she used was amazing. It was a strip of fine gravel that was between her concrete or tarmac (I forget) driveway and the brick wall of her house. I think that the strip was between 6" and 9" wide. I have no idea what sois was under the gravel (if any). So poor soil and lots of heat from the wall. That sounds as if SW France has more possibilities. Plummet
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A useful website is **LINK** You can enter where you live and it adjusts suggested dates for planting etc. See in the top right hand corner of the front page. Plummet
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OK, so I understand that the "strand" is the 10 way cable that is attached to X3. This means that you can control up to 10 LEDs or groups of LEDs. Consider this (rather scruffy) circuit diagram. Here we are controlling two groups of LEDs. The two switchy things at the bottom left hand corner are playing the parts of two channels of your controller thingy. The leds in group A are in series. Those in B are in parallel. The two boxes at the bottom are two resistors. Now suppose that your battery produces 12 volts, and that each LED drops 2 volts when shining and needs a current of 15 mA (0.015 Amps) If you want to think of electronics as being a bit like plumbing, then the Voltage is like water pressure, and the current is the amount of water flowing. We might say that the watery battery generates a pressure of 12psi. and that each LED will have a pressure drop of 2 psi across it. The resistors are there to limit the current in each branch. If they were not there then too much current would flow and the diodes would expire. Looking at branch A. The same water/current passes through each LED. So the total current in the branch, and flowing through the resistor is 15 mA. However each LED is dropping the voltage/pressure by 2, so the 4 LEDS drop a total of 8 Volts/psi. Thus the resistor must drop 12 - 8 = 4 Volts/psi. Compare branch B. (First we must assume that all the LEDs are identical. This assumption is not always possible to satisfy, so using LEDs in parallel is often a bad idea. There will be 15 mA flowing through each LED, so a total current of 60 mA must flow through the branch B resistor. The volt drop across the LEDs will be 2 volts. This means that the resistor must drop 12 - 2 = 10 volts. By Ohms law ... V = I R so R = V / I Resistor A must be 4 / 0.015 = 266 ohms, and resistor B is 10 / 0.060 = 166 ohms. Plummet
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Gary, As Frank has said, the connection should go from "8" on connector X1 [LHS] to one of the pins 1-8 of X3 [Lower LHS] as shown in the manual on page 46. The X1 pin 8 is the +ve supply. The X3 pins are switched so that when switched on current can flow from +ve supply, through your leds, and to 0V (the other side of the battery. You ask about leds in strands. I am not sure what you are asking. A. You might have some ready mounted strips of LEDs in some form of ribbon. B. Or you may be wishing to put several leds in series, linking the +ve of one led to the -ve of the next. C. Lastly you might be wishing to put a number of LEDs in parallel, that is, all their +ve s connected together, and all their -ve s connected together. An answer about the resistor requires that we know which of the three you are trying, and also what supply voltage you are using. Plummet
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This page has some nice stuff... There is a pink table some way down that gives some sample values. http://dangerousprototypes.com/docs/Basic_Light_Emitting_Diode_guide Plummet
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Posted by Denis Watkins on 18/02/2019 18:11:14: Plummet, 666 ohms, as the 0.15 should be 0.015A Noughts always get me too Ta, Expletive! Of course, instead of using Amps and Ohms you can use mA and kOhms and the sums come out correctly usually without the pesky decimal points. Plummet
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Posted by Barryorbik on 18/02/2019 17:23:16: <snip/> ... I am sure some kind person will calculate the resistor value and Wattage rating for you. Barry Um... An example showing my working method. From the spec of the led find the forward voltage drop and the working current. The volt drop is the voltage change across the led when it is shining. It varied depending on the colour and brightness of the led. The current rating will be higher for brighter leds. Lets call the volt drop D. It will be about 2.0V A typical led will be rated at 15mA that is 0.15 Amps Lets call it I What is your battery voltage? Lets call it Vb, and I'll pretend that it is 12volts The resistor needs to ensure that the led gets the correct voltage across it. The led is dropping D volts, so the resistor needs to drop Vb -D volts. Dear old Ohms law says V = I R The voltage (in Volts) across a resistor equals the current (in amps) multiplied by its resistance(in Ohms) Reorganising this gives us R = V / I The volt drop across the resistor is Vb - D, so R = (Vb - D) / I which with our numbers is R = (12 - 2) / 0.15 = 66.6 ish Ohms OK? Plummet
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But to answer your original question... It does not matter where in the circuit the resistor is as long as it is in series with the led. All the current must flow through the led and the resistor. (As opposed to in parallel with it. If they are in parallel then current can flow through either the led or the resistor.) What is important is that the led is fitted the right way round with respect to +ve and -ve. Plummet Edited By Plummet on 18/02/2019 17:30:07
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Depending upon what enthuses you you might also consider the Raspberry Pi. I know that the PIC and Arduino are much used for simple embedded tasks, The RPi is a much more powerful beast that is capable of computing power similar to a slow laptop, It interfaces to electronic projects easily. It will support keyboards, mice, cameras, audio and screens, but that of course means buying add-ons. The more recent versions of the RPI have built in Wifi. Do be aware that they are quite power hungry. I am currently listening to the radio via the use of a Raspberry Pi Zero W which is a lot better as a web-radio than the DAB radio it replaces - a lot less cut-outs. Plummet
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Hello, I am sitting here looking at a Flitetest Mini-Sportster that is awaiting maiden flights. I did build it using the advised hot-glue and although I usually dislike hot-glue it did seem to work quite well. The hot glue was used not only for sticking bits together, but also for reinforcing control surfaces hinges and for strengthening edges of the foam board. I do not think that POR would be as good for these tasks. Others may say otherwise. My model looks a real mess because I made a bleeping bad job of painting it. I am learning to use an airbrush. I had a real problem with paint adhesion - masking tape would lift the paint. The advice to decorate the model before you build it is good! The only real problem I had was that the ESC supplied in the recommended power pack died on me and I had the problem of diagnosing just what had died. The routing of the motor wires requires sharp bends close to the motor and I was unsure whether it was a sick motor or ESC. The BEC part of the ESC was still working, just the motor turny-roundy bit was faulty. Plummet
