GrahamWh
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Everything posted by GrahamWh
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I've tried an ultra sonic jewellery cleaner on a sooty exhaust - didn't really do much.
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But not for their engines - they use fully synthetic!
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The castor issue seems to be a bit like the car oil situation. Going to Halfords for a can of oil for the next oil change, there are a range of oils available. There are silly price synthetics, better priced fully synthetics, part synthetics and mineral oils. The modern high performance cars need the fully synthetics, but really old fashion cars can have the mineral oils. All to do with finer tolerances in the latest car engines. Would anyone put mineral oil in a new Audi? Edited By GrahamWh on 17/03/2019 16:23:14
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Downer! Unlucky Cymaz. Looking forward to attempt number 2.
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Is this the least enjoyable part of modelling - having to cut up the plans to manageable sized parts? Painful to chop that lovely artwork up but necessary.
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1/3 scale Bristol Scout
GrahamWh replied to Ian Easton's topic in Building from Traditional Kits and Plans
How's it doing Ian - any progress? -
All part of honing the skills. Nice results Steve.
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Just a thought Cymaz - if all works as predicted with a pitch speed of 44mph, is that enough for your plane - ie. is that well above the expected stall speed? Some say aim for double the stall speed. Looking forward to your test results today.
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Lovely bit of engineering Cymaz. Perhaps start it slow, then only bring it up to higher speeds from a safe distance using a servo for throttle control?
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I'm impressed. Good drone work too for the camera. It didn't break up - he even landed it okay.
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After much umming and arhing after finishing my Bristol Scout following a 3 1/2 year build, I chose to try this BE2e. I quite liked the look of the Be2c, but Doolittle Media/FSM do this one with a laser cut wood pack. There are a few build threads out there (David Davis has one on here) and the plane looks great in various you tube clips. I ordered the plan and wood parts kit at the end of December, and the plans arrived a bit later them expected as Doolittle Media had needed to buy a new printer and were working through a backlog. The plans initially arrived with a flaw - they were elongated as if the scanner or printer paper feed had slipped - but after a phone call new ones were sent which are perfect. I found a build article on Outerzone by the designer Roy Scott which I printed out which will help a lot. I do feel like a bit of a cheat getting the wood pack, but if I'm to get on with this and not take as long as the last build it's for the best. It will still take quite a while though - I work 48 hours a week in a timber yard and am shattered most evenings (no balsa unfortunately as the staff discount would have been useful!) and have a kitchen the wife wants replacing. Then she wants a new bathroom! The workroom is ready after fitting a new cabinet with sliding doors to hide the mess and progress will start soon - once the cowl of the Bristol Scout is mended after discovering that that biplane does indeed tip stall as a forum member had kindly pointed out but I had forgotten! I ordered some strip wood from The Balsa Cabin and I'm ready with the glue. The wood the plans and the engine - a second hand Laser 80 (on the test mount as I will want to play with it in the garden a lot before the plane's ready!)
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Posted by fly boy3 on 15/03/2019 22:46:06: Slightly off topic, would a diode do the same thing as long (dangerous) leads used to reduce volts from 2v cell to suitable glow volts for plug ? Thanks It would, but the diode may get really hot - probably burn out. Buy 2 or 3 diodes and test it, and get a heatsink if need be. Edited By GrahamWh on 16/03/2019 11:40:44
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"Castor was great in old engines and it never really caused them a problem..why i hear you cry? well, they were rubbish thats why."
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I wonder if we could use a chemical additive like the e-cig people do to get that caster smell back in the modern fuels? Could try raspberry or caramel to confuse the guys on the flight line instead! Edited By GrahamWh on 15/03/2019 17:05:36
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The great thing about castor oil other than the smell is that it puts a lot of 4 stroke engines onto the second hand market due to poor performance, where bods who like to can buy them cheap-ish and clean them up and use them or sell them on!
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Also if using a diode, consider the heat it will produce. Test it carefully and use a heat sink for it if need be. For example, if using one diode with a voltage drop of 0.6v, if the current going through it (and onwards through the charger) is say 5 amps, then the power turned into heat in the diode itself will be (voltage drop across diode) x current =0.6 x 5=3 watts. This could get the thing quite hot. A higher current will produce more heat. You can get heat sinks that will dissipate the heat produced and connect to the diode. Heat sinks are rated at temperature increase per watt. Aim to stay below a suitable temperature, say 50 degrees centigrate above room temperature, so a heatsink for 3 watts needs to be 16.7 degrees per watt or better. Of course the diode itself will dissipate its heat to the air naturally without a heatsink, but may get to an unacceptably high temperature to do so. (It''ll get hotter and hotter until the rate of dissipation (which itself increases with temperature) matches the rate of heat production, ie. 3 watts.) In our example the heat sink rated at 16.7 'c/watt would get rid of 3 watts by the time it got to 50 degrees above room temperature. Without a heat sink, the diode may get so hot it burns out or causes damage to whatever it touches. When people say they use a diode in a model with high power servos to reduce receiver battery voltage for example, I always wonder how hot that diode is getting . Edited By GrahamWh on 15/03/2019 16:49:10 Edited By GrahamWh on 15/03/2019 17:01:24
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Can a LiPo battery recover some performance?
GrahamWh replied to David Hall 9's topic in Batteries and Chargers
It's certainly interesting to see the differences. Please let us know how you get on. I wondered if the nanotech ones might be a bit fragile and therefore susceptible to variance between packs. I used to fly electric and noticed that my nanotech packs soon deformed (puffed up) even if I used the within the current and discharge limits, compared to the cheaper normal Turnigy ones which stayed good for longer. -
Cymaz, your table has load factor as proportional to diameter^3 x pitch, the one I use has it as diameter^4 x pitch. It makes a lot of difference. Does anyone know which is right? (MIne comes from RC Model World, Sept 2012)
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Hi Cymaz. As I understand it, it would be the load factor you need to multiply by 1.82 The load factor is proportional to the diameter to the power of 4 and to the pitch to the power of 1 so multiplying both diameter and pitch by 1.82 would multiply the load factor by (1.82)^5 - by 19.6! An 18x8 prop has a load factor of 840 using a table from an old edition of a model flying mag I have, so you need a load factor of 1.82 x 840 = about 1529. If you want the same pitch speed the 18x8 gave you at 6000 rpm, you need a pitch of 8x6000 / 3296 (or 8*1.82)= 14.56....or 14 to 15 inches. An 18x15 would do this as its load factor is 1575.. Alternatives with roughly the same load factor would be 19x11-12, 20x9-10, 21x8, 22x6-7 but hese would have a slower pitch speed. Load factor = pitch x (diameter^4)/1000. This would be a good discussion to have as an article in the RCMA mag by someone knowledgeable. Edited By GrahamWh on 03/03/2019 09:42:56 Edited By GrahamWh on 03/03/2019 09:50:15
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Hi Tim, If I remember rightly I have held the wing off the desk on balsa blocks and placed suitable weights on top at sensible positions above spars etc while the dope dries. I think I must have stopped the blocks sticking by having sellotape on them and moving them a little half way through. It's been a while though. Still have a lot of dope left in the workshop which I may never use again! My last tissue covered model was an SE5a at 26" wingspan for electric power, before that an Aerographics Sopwith Camel adapted for RC.
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I have just received my first laser cut wood pack. It was ordered from the FMS/Doolittle Media site and looks great! It's for a BE2e at 80 inch wingspan. Some of the edges of the ply parts are a bit sticky - I guess from vapourised glue from the ply condensing on the edges of the wood. There is obviously a burn mark on all the cut edges of the ply and balsa parts too. So, what does one do about the sticky bits - wipe with alcohol perhaps? - and is it best to gently sand off some of the carbonised wood too to help with adhesion before applying PVA? Thanks for your thoughts.
