Peter Christy Posted October 28, 2023 Share Posted October 28, 2023 One problem with modern synthetics is that they are so good, it is difficult to run an engine in on them! I have an ASP 30, which has now had an hour or two's running, and STILL tightens up if run at full chat for too long. I think I need to put a tiny prop on it, and let it scream it's nuts off for a bit! 🤣 It is currently flying a Frog Jackdaw on a 10x5 prop. My OS 20 FS also used to fly an Attilla on a 10x5. Ok, smaller, lighter model, but much more lively on a similar prop....! And it didn't tighten up at all. Suggests to me that OS manufacturing tolerances were much better than ASP! Quote Link to comment Share on other sites More sharing options...
Jon H Posted October 28, 2023 Share Posted October 28, 2023 2 hours ago, Paul De Tourtoulon said: Hearing it siezing up, is when you are flying flat out for a few seconds, even though you have peaked it out on the ground and for good measure opened it up at least a 1/4 of a turn before take off, is when you can hear the rpm dropping off shutting down for a few seconds to cool it down then flat out again and the rpm drops off again, thats what i call an engine siezing up, to hot as not enough lubrification. We could be crossing a language barrier. Seizure is a loss of lubrication that will cause a thermal runaway between the two components and physical damage. In this case throttling back will not cure the problem as the loss of RPM you heard is caused by massively increased friction between the parts and resultant damage. The high friction can cause the crank pin to hit about 400'c in under a second. This weakens the aluminium conrod to the point of failure and it is left with a distinctive hooked appearance. In any case, the damage has already occurred before you even notice something is wrong and there is no way to stop it once it has begun. The symptom you describe is simply down to the engine getting a bit warm. This can be due to insufficient cooling, incorrect tuning, or tuning change due to tank placement, valve clearance out of spec, worn piston ring or excessive use of full throttle. Most engines will not tolerate being run at full power indefinitely. As the engine heats up clearances open up and power is lost. That ruined OS fs40 i did a thread on some time ago looses power if i run it too hard for too long without throttling back. Its pretty normal behaviour and very easy to manage. I find a turnaround routine with plenty of off throttle dives keeps things under control and i can wring its neck for the whole flight without issue. Quote Link to comment Share on other sites More sharing options...
Jon H Posted October 28, 2023 Share Posted October 28, 2023 5 hours ago, Jonathan M said: what that model might be will be the subject of a separate thread! Are you looking for suggestions? If the fuel question has been dealt with the mods can change this threads title to cover the model as well. Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted October 28, 2023 Author Share Posted October 28, 2023 Suggestions would be interesting and welcome, but I think I'll start a separate thread for that. Stand by... Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted October 28, 2023 Author Share Posted October 28, 2023 PS - Any suggestions on fuel tube type? Any reason to not just use common-or-garden 3/32 clear silicone? (My old box of tubing, spare tanks, clips, bungs, filters etc has all gone so I'm starting from scratch again.) Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted October 28, 2023 Author Share Posted October 28, 2023 See What Sports Aerobatic for an OS 30FS thread. Quote Link to comment Share on other sites More sharing options...
Jon H Posted October 28, 2023 Share Posted October 28, 2023 2 hours ago, Jonathan M said: PS - Any suggestions on fuel tube type? Any reason to not just use common-or-garden 3/32 clear silicone? (My old box of tubing, spare tanks, clips, bungs, filters etc has all gone so I'm starting from scratch again.) I would stick to the model stuff just in case the garden/fish tank tube reacts with the fuel. I had that in the past where the tube supplied with a tank (from china) became swollen and my clunk fell off. I think every model shop in the country will sell it. If not, call me monday as i have about 30m of it at work. Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted October 28, 2023 Author Share Posted October 28, 2023 Thanks Jon - I didn't mean actual 'garden' grade, it was just a turn of phrase really. I was looking at MSL's own basic fuel tubing Quote Link to comment Share on other sites More sharing options...
Jon H Posted October 29, 2023 Share Posted October 29, 2023 i am sure that would be fine 1 Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted October 30, 2023 Share Posted October 30, 2023 I use Bekra 10 on my small four strokes up to 52s, the extra nitro smoothes out the needle settings to make them less critical. 1 Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted February 9 Author Share Posted February 9 (edited) On 28/10/2023 at 13:54, Jon - Laser Engines said: If the engine is new and un-run i recommend removing the rocker cover and cam cover to allow plenty of 2 stroke oil to be tipped into the engine. Turn it all around, then stand it up in such a way that most of it will drain out of the crankcase breather over night. OS do pack their engines well, but its been many years since that engine was discontinued so i would be tempted to throw some more oil at it. After that fire it up or something small ish from the range of props. run it rich at half throttle for a minute or two to warm up, full power, tune for about 90% of peak and throttle back. Get the slow run setting half decent (remember the carb is air bleed and the screw works in the opposite way to a twin needle). Run it in this state of tune up and down the throttle range with a few full throttle blasts about 5 seconds long. Once you have about 10 minutes on the clock pinch the fuel off to stop it, let it cool, restart, tune for peak power and then go flying. The OS instructions are more conservative than the above to help defend against those who's throttle only has two positions. If you can fly a normal flight with full use of the throttle up and down there is no need to mess about. Great, really helpful advice Jon, I followed it all. Beautiful little engine - was finally able to get outside and run it up today. Pre-oiled as suggested, fitted a 9x4 prop, used fresh 5% nitro fuel, primed, cleared excess, set throttle to 1/4, then it fired up on the third hand-flick! Here it is chugging away with needle at initial 2.5x open seconds after it first started: https://vimeo.com/911665369?share=copy After a couple of minutes running rich at 5,000rpm the head was getting nicely warm, so leaned it straight to 90% peak, needle now 1.25x open, which read 10,500 on the tacho, then gave it a full 4oz of fuel at various states of throttle: https://vimeo.com/911666585?share=copy Let it cool for half an hour, then primed etc and it fired first flick! Ran that up and down, tweaking the needle a bit to be certain it was in the right ball-park of slightly rich, but didn't worry about the low speed air-bleed yet as ticked over at 2,500 without much hesitation on opening up, so will deal with that more fully once it's in the model with a suitable flying prop. Thoroughly delighted with the engine! All I have to do now is build the model... 😁 Edited February 9 by Jonathan M 2 Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted February 10 Share Posted February 10 Nice to hear it is a good-un Jonathan, what flying prop will you fit? I have an un-run OS 30 FS too. After a decade long break I am finally fitting it in my as yet unfinished Peter Miller’s Ally Cat. 🐈⬛ 1 Quote Link to comment Share on other sites More sharing options...
Doug Campbell Posted February 10 Share Posted February 10 Yes Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted February 10 Author Share Posted February 10 2 hours ago, Piers Bowlan said: Nice to hear it is a good-un Jonathan, what flying prop will you fit? I have an un-run OS 30 FS too. After a decade long break I am finally fitting it in my as yet unfinished Peter Miller’s Ally Cat. 🐈⬛ The book suggests a 9x6-7 or a 10x4 for sports/aeros, I'll prob start with a 9x6 then experiment to see which suits the Amelia best once she's eventually flying. How much left to go with the Alley Cat? Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted February 12 Share Posted February 12 On 10/02/2024 at 10:31, Jonathan M said: The book suggests a 9x6-7 or a 10x4 for sports/aeros, I'll prob start with a 9x6 then experiment to see which suits the Amelia best once she's eventually flying. How much left to go with the Alley Cat? Wing finished with servos etc. Fuselage, a way to go yet but most parts made. 1 Quote Link to comment Share on other sites More sharing options...
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