Thanks for the input gentleman!! I've been thinking this through, replaying in my mind what I've experienced, and compared that to your responses. Like I said, I have hundreds of hours of experience with these Norvels in a trainer mode, and I can get just about any 1/2A engine, and others, to do what i want them to do. Cox, Fox, OS, ST, Enya, Saito, they are all in my engine footlockers and all get used at some point. This engine came out of my Norvel stash of both .049 and .061 engines, both Big Mig and AME versions. I'm gonna answer some of your question while I cool off from test running the engine in the drive way, and I see an improvement tonight while testing glow plugs.
Glow plugs: I have everything that has been recommended in the way of glow plugs, here and on the thread I posted on C.E.F . I have some Merlin plugs with their head, I have some of what I think are stock Norvel, I have both standard and TD Cox .049 glow heads, and I have both the Kamteknik and Galbreath heads for Nelson plugs with a good supply of Nelson plugs. Kenneth Cook: I compared the Merlin plug side by side to the Norvel plug. The merlin plugs I have look like they have a smaller coil, in a smaller hole in the chamber. The Norvel look much larger, on the order of what you see in a Cox head. I think that would make the Norvel a hotter plug, would it not? If things go well and it turns out my problems came from a boogered up spray bar and needle, I'll try them both later.
Props: I don't have a huge selection, and none of the 5" APCs that have been mentioned. I may trim one of the 5.7-3 props I have down and see how that goes. I have Cox 5-3 gray, some Tornado 5-3 three blade props like Larry Renger said he really likes, and some Tornado 5-3 two blade. I think I have some small MAS three blade in their new design that I have to dig out yet but not sure what size.
Tanks: the tanks I'm using start out as Perfect tanks, but I have pulled the end cap off and reworked the pick up tubes. Some of these are the #8 tank (I think) that is supposed to be a 2 ounce tank but really only holds about 1 3/4 ounce, and the pick up tube comes out the top of the tank about half way back from the front. On the ones I have taken apart, both pick up tubes were way high and like Ken said, not anchored at the back. I made one #8 tank that is standard vent with a new pick up tube that exits in the middle of the front end cap, and angles down to make fuel line routing better. All tubes are 1/8" copper. and I'm using medium fuel line to feed the engine. This idea comes from some stuff I have read and talked with people about flying the big tuned pipe engines and using bigger than normal pick up tubes and fuel line on their models. I am using the pink Prather fuel line. When the engine is running, I can really see what the fuel is flowing like.. I built up another #8 that is uniflow with a new pick up tube and the uniflow went is anchored about half way up the pick up tube, which exits about the same place the other tank does and turns 90 degrees down. I also have a Perfect tank that is a 1 1/4 ounce tank, standard vent, that is more or less brand new and I haven't opened up. In flying this airplane so far, all these tanks seem to run pretty much the same.. I started with a 2 ounce plastic tank, because it would fit, and I had one, but could never get it to run a whole tank of fuel out. I was figuring I would need a capacity of 1 to 13/4 ounces to do a full pattern comfortably on 42" to 44" length lines, and so far I have been in that range and will stick with these tanks and keep testing.
Fuel: I have tried standard SIG 10% Champion because I have run these on this before and it's my main go to fuel. Never had any problems. I have run 15% nitro Cool Power with some castor added with no real improvement or changes, and no obvious problems with it either. Before the last flying session, I had found a gallon of Byrons 15% nitro, 50/50 oil in my stash. I have a quart of Norvel brand fuel ( probably made by SIG, as it looks just like their mixes and they were the original importer of the engines) and it say 18% total oil on the label, so I added enough extra castor to get it up to that and maybe a bit more. I ran this fuel last time out, with a few drops of Amoral in it ( I have ALWAYS kept a small bottle in my flight supply bag and have never had any plug issues from it either) and I think the engine ran best on this mix so far, so I will continue with that. I'll try a few tanks of the 25% Norvel stuff next time, especially if things have improved, I have the supplies now to mix anything I want, also.
The Model; The airplane is a Wild Bill Netzeband Doodlebug. I am pretty sure it's the middle size airplane from the article he presented in the February 2003 Flying Models magazine called "The Doodlebug Brothers". it's about 25" span, and with a chord of 8.75" that puts it in the 200 sq.in. range which would be the middle model of the three sizes he presented in that article, with the smallest being for .049, the middle one intended for the .061, and the largest one is intended for the .074. It weighs 12 ounces I think, and when things have been right, the .061 pulls it just fine, with the engine running ( I think ) in the high 17,000 to 18,000 RPM range and it flies just fine on the 42 to 44ft fishing line I'm using.
The engine: I think it's a Norvel .061 Big Mig , with the bigger diameter head and cylinder. It may have come off a Bratco Sky Baby or Hexdrone airplane. It might also be a NV version. The needle valve goes back at an angle which I like. It has the bolt on venturi. I had an inverted landing early on in this project which bent the spray bar. I did not have a spare, so I had to straighten it out. NV engine didn't have any new ones in stock for a while. Sometime this year I saw they had complete venturi with the NVA in it so picked up a couple of those. I did a standard break in, which I am very familiar with, after all of them I have run and used at KidVenture, but this one had a bit of time on it and it was no trouble at all. Still has quite good compression, and only sticks at the top of the stroke when it's stone cold and no fuel in the cylinder. it starts right now with a 1/2 electric starter. I found a good deal on one of those long, black GlowBee battery powered starters with a charger on eBay once, and now it comes in handy with some new batteries. I solved the loose muffler issue by gluing it on with red silicone and replaced the wire bail that it comes with to hold it on with some safety wire on each end, then twisted the two ends on the back side of the engine to hold it tight. I have to run the muffler for the pressure fitting.
Last session, the last several flights all seemed to slow down from things going rich, just slow enough that I couldn't fly the pattern. It did it with the uniflow tank and with the 1 1/4 ounce tank, almost exactly the same each time. After reading everything you all have posted here and on C.E.F, and thinking about what I have done so far, I took the following actions. Today, I pulled the venturi off. It had never been off before and it feels like it's almost a friction fit in adding to the O-ring and bolt through the venturi to hold it in place. I was going to use a whole new assembly, but when I tried to put it in, it didn't fit well, and the spray bar went straight through so the needle was NOT swept back like the original. That made it really hard to put the fuel line on the nipple because the end of the muffler is in the way. So I just pulled the spray bar out of that venturi, and pout it in the old one, and used some red hi-temp silicone to help seal it when I put it back in. I also put a short length of fuel line on the threaded portion before putting the needle in, like we do on a lot of engine, to help seal the thread against air leaks. I had been running it like that the last few time out and it seems to help. Kenneth Cook : I have noted the idea of building up a one of these new venturis with the Cox needle valve assemble that you made mention of. I have all the stuff, but didn't want to get that deep into it tonight. I put everything back together and headed out to the driveway to test glow plugs.
I started out with what I thought would be the bottom rung of the ladder, and that was the stock Cox glow head, like 944_Jim suggested. ( Thanks Jim!!) I have run some of mine with these before and knew that would fit. Al Kelly clued me in that the Norvel, Cox and Testors heads would all interchange. The threads were really just ever so slightly different, but not enough to cross thread them or cause any problems and I have found that to be true. I used the same 15% Bryons fuel I spiked up with some extra castor. I shook the bottle and still no foam. Engine started easy as usual, needled it in slowly through 17,000 RPM and then about 17,500, it quit like it was over lean but really sounded like it had just got into a wet 2 stroke. I repeated this several times and it did it at the same tach reading , so I made note of that and moved on.
The next plug was a Cox TD high compression head. The only difference I can see in these is that the combustion chamber on the standard head is bigger, and the TD head is more flat across the bottom surface. I installed that, fired it up and got more RPM, into the 19,000 range and higher but didn't go so far as to see when it went over lean and quit. It seemed to run much better, much more steady that previous static runs. Before, it would seem to needle Ok , then hit a spot where the RPM would just take off, right about the high 17,000 range like I need it to be. I added a head gasket but that didn't seem to help at the time, and I left it in there, so there are two head gaskets still..
Next came the Galbreath/Nelson plug combination, again with two head gaskets. It seemed to pick up right where the Cox TD head left off, very similar run, but seemed to needle a bit better. I could put it anywhere I wanted between 17,500 and 18,200, which is where I think I want it. Run time on a full 1 1/4 ounce in the standard vent tank ran very smooth and consistent. Up to this point, I wonder how necessary uniflow is on these engines in this RPM range?? Flight tests will help answer that question. I can make more of these tanks with a uniflow vent in this capacity, maybe 1.5 ounces, if need be.. When running in these tests, I can see just a few bubbles , and I mean very few, ever now and then. The fuel line stays clear, almost like there is nothing in it. I have one of those small diameter fuel filter in the middle of the fuel line, after thinking that I needed that , plus filtering my fuel when getting a syringe full. I did not try the Kamtechnik head, because when compared side by side to the Galbreath head, the head surface and combustion chamber size looked the same, so I don't expect a big change, if any, when I use it. I'll try it after test flying a few flights.
One things came to me while I was typing out this diatribe!! I have some of those Wasp .061 R/C engines that Hobby People used to sell so cheap, and some one used to put out a replacement venturi for them that used a TD spray bar and needle. I am pretty sure there are some extensive threads on here on how some guys did their own modifications. I made up a couple of my own and installed them, but never ran them. If this engine continues to give me fits, I can just swap it out for the Wasp .061 really easy. I think I remember the engine getting good reviews for power and being pretty much like the Norvel. I'll dig one of those out and look it over. Maybe the muffler will interchange if I have to use these straight verturis from NV engines?? More experiments to come.
I have several 1/2A stunt kits in my stash, plus a whole pile of plans and other ideas to try. Now is the time to get to them!! I really liked the
Leprechaun Legends planes that I have plans for also. My first real 1/2A stunt model was a Gremlin, that I still have, that I blew the plans for it up out of Model Builder magazine and built it with the wood from the Admiral River Boat life preserver balsa wood!! I powered it with a TD .049 and it was the first C/L stunt airplane that I ever did any outside square loops with!! I may get that down off the wall, recover it and put it back in action!! Thanks a lot to all of you again for your input and suggestions. Dave Moritz : Thanks for the email with the engine information. I will save it to my computer and print out some hard copies for future reference. I again thank everyone for taking the time to respond and I will update after test flying again, possibly tomorrow.
Type at you later,
Dan McEntee
Topic: Norvel .061 Big Mig for Semi-Serious St (Read 16048 times)