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Guest -> RE: F-104 car team not doing things in integrated way (9/7/2004 3:02:45 PM)
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quote:
ORIGINAL: Guest
Well Ok Then!
I do appreciate all the helpful advice from everyone who has replied to the North American Eagle and the J79 turbine engine project. I suppose that if you were here working on the vehicle and the engine. Purhaps we might be further ahead of the game then we already are.
Well, here is my view about running a jet car at 800mph. You need the safetest vehicle that will utilize every bit of possible thrust the engine can give but still be within the safety margin. When I was stationed with the "388th Hill AFB UT." some of my fellow engine tech's wanted to know just how far we could push the J79-15 if we were in war time conditions. We ran the fuel control from 100%up to 110% overboost and operated this test engine for several hours on the test stand, by the way the engine did not fly apart and the J79 is one tough engine. Afterwards we tore the engine down to find out what damage had occured. All though the damage was minimal there still was damage. Keep in mind that this was back in 1978. Technology has improved since that time! S&S Turbines from FT. ST. John BC has a new process of Ceramic coating the hot section, this is nothing new, however their new process is better, then say technology from five years ago. I cannot comment on the actual process it is patented and prorietary. I can say that the burners, exit duct and turbine blades are not stock and can handle 40% more heat! Heat is what makes the turbine engine develope more thrust. If you would like to learn more about the J79 modification visit S&S turbines website. www.S&Sturbine.com They have a valuable web site and one can learn about the lastest process.
So let's get back to the fully functional J79 jet engine and why NAE is using it. To go 800 mph one needs some room, say fifteen miles. Two or three miles of that is getting up to speed. This is not a quarter mile! The time trap is one mile. My intent is to not slam the driver with 4.5g's of acceleration nor subject the airframe with that type of loading. One reason for using a fully variable engine is give constant and gradual power up maximum thrust output. The other reason is during testing of the vehicle we will need to do many low speed testing runs. It is inheriently dangerous to run the J79 in the 4000rpm to 6000rpm for any length of time while on the ground. The engine has a very wicked harmonic vibration between these throttle settings! Being able to control the variable exhaust nozzle gives you somewhat of a speed control. With the engine just below 4000rpm, you make thrust by closing the nozzle. It may only give you 1,000-2,000 pound of extra thrust but but taxing the car and running at low speed say around 200-300mph that will be enough. How many arm chair mechanics thought of that one? That idea was thought out and planned for well in advance. We are even modifying the emergency nozzle control valve with a electrical linear actuator for posotive control.
Let us move on to the actual thrust of the J79, as far as I know no production J79 holds together with thrust above 18,000 pounds. Even the the later -19 could at best make 17,900 in normal flight mode! If you do not believe me take a look at the proformance spec's from GE www.geae.com and look up the specs for the J79 yourself. The basic J79 core produces around 12,000 pounds of DRY thrust. The only way to make more thrust was to install an A/B section and this would enable the additonal 3,000-6,000 pounds of thrust. The development history of the J79 started with the simple -3, -7 and -11 and each engine config. only had one or two A/B spray bars. The later -15, -17 and -19 had four and six spray bars. Again the more fuel you pour in, the more heat is developed and the more thrust you make. The -19 config. was at the actual limits of the hot section for the times. Now this new ceramic technology can improve the thrust considerably. Our actual high speed engine is a modified J79-15 and it has all the modern ceramic technology. Now we can actually get a engine with more than 18,000 pounds of thrust, how much we do not know, we will use all the data from S&S Turbines and their test stand to determine the actual thrust. Why am I telling this tell? It all boils down to thrust to weight, if our car weight is 16,000 pounds and the engine makes 18,000+ then some of the rolling force is overcome and now we have the potential to make the 800mph mark. Our current -7a configuration will at best make 15,500 pounds of thrust which will be good enough for low to mid range speeds.
For the nay sayer or the guy who believes that we cannot make our car go very fast. Well I do not know what to say. Just look at what the Brits did with their car, 768mph. I believe that they used two fully functional Rolls Royce Spey engines to develope the thrust. Granted the Thrust SSC and the NAE vehicles are not the same type of cars. The Brits built theirs from scratch, NAE has taken an old jet fighter and converted it. So what, it makes prefect sense to use a proven design. I have heard many poeple say why did you take a perfectly good airplane and destroy it. Well the truth is we did not the owners bought it all cut up. The team took a basket case and over the last five years have put it back together. If it seems like we are dragging our feet and taking to long to get it done. Well maybe one should look at it this way. When traveling at speeds of 800+ would you want your car to be safe? You can not rush through a project of this magnitude, it takes time to build in safety.
This last comment is directed towards one of our favorite supporters Franklin Ratcliff. I have seen and read your comments. I am amazed that you have not already built and run the fastest car ever. With all your vast knowledge it would seem a shame that it is wasted by not building something that currently competes in any land speed venue. When you can show me actual pictures or show up to an actual venue with something that makes some speed. Then and only then will I or anyone take you seriously. So far all I see from you is talk, why don't you put your money where your words are. Even an old tired mechanic like me can spend hours a day looking up info and posting it. However for you Franklin to comment on other people and their work and even tell them what a poor job they are doing. Maybe even take credit for suggesting ideas on how to solve problems. Well I just do not understand that part. Maybe you could show up to one of our work parties that we hold every Saturday and help us out. Got any balls to do so? If it seems like I am picking on you then you would be correct. This whole statement is directed for your benifit. However it is informative for those wanting to know more about what we at NAE are doing to get ready for the 800mph lands speed record challenge.
Just for the record, while working for Boeing I have also been privy to learn current state of the art Hydraulic, Electrical, Pneumatic, Airframe, Avionic systems as well as Flight ready Turbine Engines. That was and is the same thing I did in the Air Force. All though I am not a self proclaimed expert. I do know the workings of every aircraft that I have ever worked on. The F-104 is no different. Maybe the reason it is taking NAE so long to put this old hunk of junk back together is this. Fourty very knowledgeable highly skilled and trained voulnteers are working on this project and when we see something we do not like we speak up. We have had to change many of our own designs because of this small problem. The day we haul the vehicle out to make some actual speed runs will be a very good day indeed. Until that time everyone will just have to be content with looking at our pictures and words. Then have to deal with how slow the build progress is. I for one am in no big hurry. Inspite of what other may say about the NAE we will run the car when it is ready and safe to do so. Thank You for taking the time to read my comments. If you would like to comment please do so I welcome the challenges that life toss at me.
Bill Eckberg
J79 Engine Tech. & NAE Crew Chief
A jet fighter is based around a design with inherent INSTABILITY to provide the maneuverability perceived as needed for combat. This is why even though the X-15 and the F-104 were designed in the same period on similar planforms the F-104 wings use anhedral where as the X-15 wings do not. A jet land speed car is based around a design with inherent STABILITY. For example, placing the center of gravity as far forward as possible and the center of pressure as far aft as possible to provide built-in directional stability.
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