Radio Control Helicopters
Ray Stacy [[email protected]]
The C-Spec PS mystery has been solved!
LAST MONTH I wrote about carburetor problems that plagued my new O.S. .91 C-Spec engine. I couldn't get the engine to run consistently from one flight to the next or even from the start of a tank to the end of the run. I had the carburetor apart and initially found some debris, and I thought the problem was solved. This quickly proved not to be the case.
The high-end mixture could be anything from rich to lean, and it would be something completely different by the end of the tank. At the same time I couldn't get the low-end mixture rich enough to stop the buzzing idle, nor could I get the engine to return to an idle properly.
It got to be so bad that I bought a new YS 91 engine just so we could get some time on the helicopter. The YS engine ran perfectly on the first flight and every run after that. Then the big dilemma was what to do with this new O.S. C-Spec. I didn't need another doorstop or paperweight, and I couldn't, in good conscience, sell it to anyone.
I have been doing this for enough years to know that the carburetor wasn't right. This didn't surprise me too much because it wasn't the first time an O.S. engine had carburetor problems. The O.S. .46 H required modifications to the carburetor spray bar to get it to run right.
The O.S. .50 model finally had a good carburetor and is one of the best all-around helicopter engines ever made, even though some would argue that the O.S. .50 crank needed to be modified. Today the O.S. .50 Hyper is one of my favorite engines.
A quick check on the helicopter forums confirmed my suspicions regarding the C-Spec PS. Not everyone had problems with the engine, but not all of us run it as hard either. Most of the people who responded were having the same problems I was.
The 60M carburetor that comes on the C-Spec PS engine doesn't consistently work right. I was told that the O.S. C-Specs were designed for active mixture control because all the top Japanese pilots did this. I am unaware of anyone doing that in the U.S.
I received numerous suggestions about how to solve the C-Spec carburetor issue. Some people buy a needle-valve assembly (O.S. part number 29081910) and install it in the overflow hole of the 60M. This lets you control the amount of fuel that is returned back to the tank and forces more fuel into the carburetor. I did not try this.
Others use various methods of restricting the fuel flow back to the tank. One of the more popular suggestions was to install the O.S. 60K three-needle carburetor I mentioned last month.
The more intriguing solution I received was a system offered by James O'Neal of O'Neals Manufacturing Inc., or OMi (www.oneals.com). He created and manufactures the popular Viper Head that many of us use on our O.S. and YS 91 engines.
James offers a modified 60K carburetor and modified Cline Regulator to replace the pump and stock carburetor on the C-Spec PS. With the OMi system, the fuel tank is pressurized identical to the YS setup, and the Cline Regulator controls the fuel flow to the carburetor, similar to the YS regulator.
Everyone I talked to who had tried the OMi system thought it was great! No one disliked how his or her engine ran after installing the new setup. Not only did the C-Specs run better and stronger, but many people also liked not having the goo from the muffler pressure lines going into their fuel tanks and contributing to the deterioration of the pickup lines.
After a quick call to James, the OMi system was on its way to my doorstep. I also decided to get the Viper Head for the C-Spec. I don't know everything James does to make this work, but a basic description is that he bores out a new 60K carburetor to 10.8mm. He may do other things to the carburetor as well. Then he modifies the Cline Regulator to work in our environment.
You can send your carburetor to James for modification if you want, but he prefers it to be new. Ron Lund (www.rcheli.com) goes as far as to sell a new C-Spec without a carburetor so you can save a few dollars if you intend to buy the OMi system.
The OMi installation is easy. Swapping carburetors is as simple as loosening one nut, removing the 60M carburetor, and installing the new OMi modified 60K. Don't forget to remove the rubber O-ring from the base of the old carburetor and install it on the new one.
The fuel pump must be removed from the C-Spec since it is no longer used. The pump is held in place by friction fit, but I couldn't get it out. I had to remove the backplate from the engine and push it out.
At this point you need to run a fuel line with a YS one-way valve from the backplate of the engine to the fuel tank. This is how the tank becomes pressurized. OMi can supply the YS valve if you need it. And that's it!
The Viper Head installation is just as easy. Remove the old stock head, but leave the .008 shim in there. Install the new included .008 shim on top of the old shim and add the new Viper Head. Tighten all head screws equally and you are good to go.
I had to remove the YS engine from a Raptor 90 to try this. By this time there were roughly two gallons on the YS, and it never skipped a beat or required fiddling with. YS did a great job of carburetion on this engine, but everyone I talked to about the OMi setup promised more power from the C-Spec, and I had to see that.
The first thing I noticed with the new setup was that the C-Spec started almost immediately. It never did that with the 60M carburetor. The engine instantly settled into the smoothest idle I had ever heard. I had to double-check and make sure it wasn't still my YS in there!
Engine acceleration was beautiful, and the engine was singing happily on the Muscle Pipe after a few clicks on the needle valve. Full-power climbouts were nice.
The engine is definitely happier, but I really noticed the difference in sustained tic-tocs and long rainbows. Instead of choking and bogging the C-Spec, now it digs in and runs. It hits a point where it just won't slow down. Flying by the seat of my pants, I can clearly tell that the C-Spec with the OMi setup has more top-end power than our YS did.
Fast forward to a couple gallons of fuel later, and this has become the best-running engine I have. I don't think I have touched the needle valves since the initial setup. Nice job, James!
The OMi setup isn't for everyone. It isn't inexpensive, nor should it be. It works well and does exactly what OMi claims it will do. I am unhappy with how the stock C-Spec ran, but I am grateful for the OMi solution. I will probably do it again for my next project.
If you are interested in increasing your C-Spec PS's performance and reliability, give James a call at (256) 776-0879. You will not be disappointed.
I like to hear other people's perspectives on things. Therefore, when my flying buddy Jeff Francis asked if he could write a piece about crashes, I jumped at the idea—mostly because he has had some of the best crashes, and I was anxious to see
RC Helicopters
Ray Stacy
how he did it! Okay, maybe not, but Jeff has become one of the better pilots at our field, so he must be doing something right.
He wrote:
"Crashing: If you fly helicopters, you no doubt know a little something about crashes. If you are a beginner you may be very familiar with them, and if you are an experienced flier you may have not had the experience in a while.
"Everyone has crashed or will crash at some point in his or her flying career. I have crashed what I consider to be more than my fair share in the three years I have been flying model helicopters.
"My first year I had a major crash on an average of every 12 flights, and I put in about 300 flights that year, but I justify it and don't let it bother me too much because I have been fairly pleased with my flying progress. This past month I have had a string of bad luck and crashed more than I did all last year. Here is my take on how to avoid crashing, what to do during an imminent crash, and what to do after a crash.
"Precrash: First off, everyone should do a thorough preflight at the beginning of the flying session. This is obvious, and there is a lot of info available on this. Loose screws and such will ruin a flight quickly. Everyone should have a throttle hold curve setup and know how to activate it. This becomes important during the crash.
"Test your battery before each flight with a meter that puts a load on the battery. I lost a helicopter on the second flight of a freshly charged battery that usually lasts five flights. A cell had gone dead between the two flights. The helicopter dove straight in 30 seconds into the second flight.
"Make sure you have the correct model on your transmitter. When I am spinning up the blades, I test the cyclics to make sure everything tilts the way it should and the rudder responds normally. If you have the wrong model selected and didn't get a hot start, this will verify that everything is at least working the way it should.
"While flying, especially when trying a new maneuver, I plan out which way to move the sticks if things go wrong. When I was learning nose-in inverted hovering, I concentrated on learning the move but also practiced my bailout just in case. It was always in my head that if I lost it, left thumb down and right thumb up. This would return me to a tail-in hover where I could regain control.
"During the crash: If something happens while you are flying, it is for one of two reasons: a failure of the machine or dumb thumbs. If it is dumb thumbs, you may not have time to react. Try new moves up high for this reason, and plan your stick movements if things go wrong before trying them.
"If you do get completely disoriented and can't tell which way the helicopter is, move the sticks. I have been frozen as I lost orientation and done nothing as the helicopter drills itself into the dirt. If it's screaming down, reverse collective, or put in cyclics. Don't do anything.
"If it is a mechanical/electrical failure, my best advice is to try and get altitude; there is a lot less earth to crash into up high. Don't panic; try to evaluate what has gone wrong. If you have lost throttle or collective pitch, the helicopter can still be flown. Most of the early helicopters didn't have collective pitch; altitude was controlled by raising or lowering the head speed.
"If you do lose your collective pitch control, you will need to get used to a slower response and head speed changes. Using the throttle, you can still control altitude.
"If you lose the tail for some reason, go up high and try for an autorotation. If you have a driven tail this may not help, but it might. I have had the link pop off the tail on my driven tail model and did a successful autorotation. For some reason the tail spinning kept it from going to extremes of travel, and the tail just sort of wobbled back and forth a little.
"If the helicopter seems barely controllable for whatever reason, get it away from people and get it down. Once you are sure it is going in, hit throttle hold. You don't want the engine throttled up when it hits, and once it hits you may not be able to throttle down. This is why it's important to have a 'hold curve' setup. Rather than bringing the throttle down with the stick, it is easier to just flip a switch.
"And what if you are in idle-up? Bringing the left stick down will not kill the engine. During this turn you don't have time to think to change flight modes and bring the stick down. Throttle hold will get you to idle no matter what.
"I once had a washout link break off of the swashplate. It still responded—sort of. I tried to bring it back for a normal landing. As I got closer to myself, it became clear that the control I had was not precise enough to be flying that close to myself.
"I ended up getting it about 20 feet high and 20 feet out with no idea which way it would go next. I put the left stick down, and luckily the collective still mostly worked. I didn't feel bad about destroying it because it was trying to destroy me!
"If you have lost complete control and the model is flying erratically, yell as loud as you can, 'I don't have it!' This does two things. It alerts others around of your situation so they are aware and can pay attention to where it goes. Also, if I'm in the pits and forgot to use our frequency control system and just turned on my transmitter, I will know it's a good idea to turn it off pronto. Be safe!
"If the helicopter goes in off the field, get a bearing of where it's going to land. This may not be possible. Rick at our field had a radio failure with his helicopter. It dove straight down behind a tree line. A few seconds later it came back up only to do another dive in another direction. That one took awhile to find.
"We have a written 'rule' at our club that anyone watching while the crash happens is to make note of where the aircraft went in. This is more or less just to remind everyone to do this. Get a bearing, and then (for example) say the model went down between me and that tree, 400 feet out.
"Postcrash: Now walk that line until you either find it or get close to where you"
Transcribed from original scans by AI. Minor OCR errors may remain.
