mightypeesh Posted June 15, 2015 Share Posted June 15, 2015 Hi Ladies and Gents. My Great Planes Little Toni has finally made it back onto the bench for repairs after the UC ripped out last season. As I was fibreglassing and making good it has got me thinking about the engine installation. The plane was 'very' second hand by the time I got my mitts on it and has a OS 108FSR (BX1) which is inverted. I have always found it difficult around the idle point to keep her running smoothly, and out of maybe 15 or so flights that I have had she has probably gone dead stick on approach as the revs drop on about 10 of them. She is a very slippery plane and flies beautifully - Its just the stopping thats a problem! As she is stripped down at the moment I thought I would investigate solutions. At present the relationship with the fuel supply outlet from the tank is as follows: Engine inverted - the needle is 28mm lower Engine right way up - needle is 28mm higher Engine sideways - needle is 15mm higher. The outlet pipe is 30mm from the top of the tank. In the OS manual it states that the top of the fuel tank should be 5-10mm above the needle - so the right way up it should be about right, but upside down it is way out. Also I have read that for inverted engines just turn the plane upside down for starting and adjustments. If that is correct then am I just making work for myself by turning the engine? Would a Perry pump from just engines help? I hope this all makes sense - this is my first plane that is powered by other than electricity so I am on a steep learning curve. The black felt tip line on the firewall is the level of the fuel outlet pipe. Cheers for your thoughts, Simon Edited By mightypeesh on 15/06/2015 11:12:05 Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted June 15, 2015 Share Posted June 15, 2015 Simon- I wouldn't worry to much about the top of the tank etc...it looks ok to me with the mark you have put on....the only reason I would put the engine on the side would be to get the exhaust on the bottom of the model(my preference). ken Anderson......ne....1..... on the side dept. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted June 15, 2015 Share Posted June 15, 2015 You have asked questions that will result in war being declared between forumites. My sixpence worth is OS engines are competent engine builders and their advice is good. You can get away with deviating from it but everything gets more critical. Putting the engine sidewinder gets you as close as dammit to manufactures advise. Engine upright is a bit too high, and sooooo ugly. A Perry pump will work, but with a bit more complexity. I have a feeling however that the bottom end of your carb is not set well, and this is the dead stick problem. Have you access to an engine Guru before you make work for yourself, because as we all know work is harmful to health and should have a proper risk assement before being undertaken. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted June 15, 2015 Share Posted June 15, 2015 I've had similar instillations myself and I agree it sounds like the slow running needle needs a tweak ? If you did change it I agree sidewinder, get the exhaust at bottom. John Quote Link to comment Share on other sites More sharing options...
The Wright Stuff Posted June 15, 2015 Share Posted June 15, 2015 Ahh, stick the undercarriage on the top and reverse the elevator and rudder servos. Engine is now inverted, and you have a unique high-wing model. Sorted! Quote Link to comment Share on other sites More sharing options...
mightypeesh Posted June 15, 2015 Author Share Posted June 15, 2015 Hi gents, thanks for the responses to my question. From what you are saying it is more down to a tuning problem rather than the location of the tank. I will re-install it inverted for now and start afresh with the set up. I have dug out Brian Winches '2 Stroke Tuner' article from November 2012 and have got a tacho as well. I will set it up at home before going to the field, and get one of the sensible chaps to check it for me. If it still plays up I will have a go side ways. Plus point is I dont have to mess about cutting the cowling again! Cheers folks, Simon Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted June 15, 2015 Share Posted June 15, 2015 Try a longer feed pipe to the carb as well Simon, so the fuel has to go uphill in case it's getting swamped a little. John Quote Link to comment Share on other sites More sharing options...
mightypeesh Posted June 15, 2015 Author Share Posted June 15, 2015 Good idea John. I just got the roll of fuel line out to replace them so I will do that. Thanks, Simon Quote Link to comment Share on other sites More sharing options...
Nigel Herron Posted June 15, 2015 Share Posted June 15, 2015 Hi Simon I have been down this road several times, even gone to the extremes of major alterations with trying to lower the tank in relation to spray bar height, different types of tank and even purchased a Clyne fuel pump not the perry pump as this will not resolve your problem with siphoning or bad starting and as to starting an inverted plane think of the hazards involved been there done it etc etc (I'm not saying it cant be done just not preferable by me) I would agree that it sounds more like a setup issue get that right then go from there, it may be that the idle mixture is leaned out to stop any of the above issues? nige Quote Link to comment Share on other sites More sharing options...
Rick Tee Posted June 15, 2015 Share Posted June 15, 2015 You could also try a hotter plug, OS6 I think, might help. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted June 15, 2015 Share Posted June 15, 2015 Rick, why? Quote Link to comment Share on other sites More sharing options...
ROY DAVIES 1 Posted June 15, 2015 Share Posted June 15, 2015 Make it a sidewinder. You have an 'apple cheek' cowling so it will look prettier and less chance of flooding unless you do inverted starts ( always a pain ) and less chance of flooding itself when sitting on the ground awaiting it's next flight. And importantly if you happed to land it 3 or 4 inches lower than normal you may only need to buy a new silencer. Go Sidewinder. Quote Link to comment Share on other sites More sharing options...
Tony Richardson Posted June 15, 2015 Share Posted June 15, 2015 Simon a good rule of thumb that has always worked for me is the centre line of the fuel tank should be in line with the fuel needle valve, keep the tank as close as possible to the engine ( unless you have a pump ) Nigel is right a Perry pump will not solve a siphoning problem a cline regulator may? My advicde tune your engine as close as possible to perfect and keep the idle high until you are over the threshhold then pull it all the way back, an on board glow driver that is programmed to light the plug at 1/4 1/3 throttle may also be a solution, keep us posted will be interested how it turns out. Quote Link to comment Share on other sites More sharing options...
Shaunie Posted June 15, 2015 Share Posted June 15, 2015 Personally I would prefer to go sidewinder in that installation. It will lift the needle valve height a bit, also with the exhaust port at the bottom flooding should be a thing of the past and will as a result prevent fuel pooling in the plug. Nevertheless I think a bottom end tweak may also fix your current problems. Shaunie. Quote Link to comment Share on other sites More sharing options...
Tony Richardson Posted June 15, 2015 Share Posted June 15, 2015 Just had a real close look at the above picture, Shaunie is right turning it on it's side will bring the carb up level with the outlet pipe should be perfect, also if that is a Great Planes motor mount the holes are square so all you have to do is turn that mount 90 degrees and everything should line up. Quote Link to comment Share on other sites More sharing options...
Rick Tee Posted June 16, 2015 Share Posted June 16, 2015 Posted by Donald Fry on 15/06/2015 19:18:03: Rick, why? Engines dying at tick over can be caused by the plug cooling off, which is one of the reasons for fitting an on board glow (though usually with large, inverted 4 strokes). Fitting a hotter plug may help if that's the cause. Checking the engine settings are spot on with half a tank is the first thing I'd try. You can also try re-plumbing the tank using the uniflow system, which takes the fuel mass out of the equation (constant flow full to empty) but will require 2 one way check valves to prevent flooding when closing the throttle. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted June 16, 2015 Share Posted June 16, 2015 Thank you Rick, makes sense. What is a uniflow system for my continued education. Quote Link to comment Share on other sites More sharing options...
ROY DAVIES 1 Posted June 16, 2015 Share Posted June 16, 2015 And once you have found the ideal setting don't fiddle with it unless you go with another fuel. I have found a good running setting is a good setting all year round as long as you don't have it leaned right out initially. Good Luck, Donald. Quote Link to comment Share on other sites More sharing options...
mightypeesh Posted June 16, 2015 Author Share Posted June 16, 2015 Wow, thanks for all the input chaps, Plenty to try if the initial retuning does not work. I will sort out the uniflow system though as that sounds like it will help prevent syphoning and flooding the engine. the page I read that explains it quite well is here **LINK** I will report back as and when Cheers, Simon Quote Link to comment Share on other sites More sharing options...
Don Fry Posted June 16, 2015 Share Posted June 16, 2015 There, I have learnt two things today. 1 uniflow fuel systems. 2 use a clamp when doing 1mm holes into tough nylon. The 7 mm deep hole between finger and nail is vey sore. Quote Link to comment Share on other sites More sharing options...
ROY DAVIES 1 Posted June 16, 2015 Share Posted June 16, 2015 I think I will say a collective 'Ouch that hurt' from all posters on this topic. Were you wearing goggles and a hard hat plus boots? Nylon and all plastics are pigs for drill bits breaking through before they have cleared the hole the next thing you know is the drill bit screws it's way through with all sorts of consequences. If you can sandwich between two pieces of wood and drill It will give you nice clean holes to the correct size. a small centre drill is useful they don't tend to 'grab' great for accurate piloting but you are then back to the above scenario of using a grips or clamps. If you were using a pillar drill it may be useful to check this, Hold the chuck and move it up and down (vertically ) If it moves therein is the problem. When pulling down to drill there is resistance that holds the spindle up as soon as the drill begins to breakthrough it's away. It can be fixed by looking for the screw/s that hold the column in place, there are many and various. The same applies to some electric hand drills that have a hammer function their spindles are free sliding for a mm or more. be careful when using them. Again, Ouch, Get better soon. Quote Link to comment Share on other sites More sharing options...
GrahamWh Posted June 16, 2015 Share Posted June 16, 2015 One last comment Simon, when you have done all you intend to do re installation and re-tuning, another thing that can be helpful if need be is to increase the idle speed setting on your transmitter to make it less likely the engine will cut out as you are on the final approach, and to off-set this by using a lower pitch propeller to keep the approach speed down. I had trouble slowing down my Renegade until I swapped the 12x7 prop to a 13x5 (approximately the same load prop, but less pitch). This meant I did not have to reduce the engine speed to "likely to cut out" revs. I hope your finger heals okay - I damaged a thumb last year drilling! Edited By GrahamWh on 16/06/2015 15:55:38 Quote Link to comment Share on other sites More sharing options...
mightypeesh Posted June 16, 2015 Author Share Posted June 16, 2015 I'm learning loads too! I love this site. Sorry about your finger Donald. My favorite is slipping with stanley knives - always on the same finger - its pretty much stiched end to end now! Thanks Graham, I will try that too - I have a 15x8 on it at the mo, so maybe try a 16x6? I hope I get this sorted because it is a lovely aircraft. Cheers, Simon Quote Link to comment Share on other sites More sharing options...
Rick Tee Posted June 17, 2015 Share Posted June 17, 2015 **LINK** Nice pic of uniflow system which uses 2 check valves: **LINK** Quote Link to comment Share on other sites More sharing options...
mightypeesh Posted June 17, 2015 Author Share Posted June 17, 2015 Thanks Rick, they are brilliant links - I am learning so much. As usual I have got a bit more involved in this repair than I intended - it was going to be quick and back in the air, but now I have inspected the wing damage where the spats punched through both it going to take a bit more love than that. Also whilst it is nice and clean and fuel free I am going to do a re-spray and change her into the blue and silver number 6. I will start a new thread on that and the repairs to the wings later. Many thanks, Simon Quote Link to comment Share on other sites More sharing options...
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