Had a nice day to get some speed stuff out

Ken Cook wrote: Today, my son and I were invited to a very old control line club. The club was founded in 1937 . The field is all asphalt circles so it makes flying speed related stuff a joy to fly. I had 3 Cox speed planes. Of the 3 they're all TD .049 powered some having lightened and balanced cranks that have also been heat treated properly. I purchased one of Bernie's lightened and shortened pistons in 2010. I found it to have too much SPI so I used the shims designed for muffler use and shimmed the cylinder up. It took a few tries but using this shim in conjunction with the Kustom Kraftmanship .002" shims I was able to see immediate results after the 3 flight. I was breaking into the mid ninety mph range. I have a full bodied 1/2 A proto speed which just wouldn't run for me today. I need to do some redesigning of the fuel system. The picture quality isn't so great, as it was taken from my cell phone. The orange model in the front is a K&B rear rotor powered formula .40 which easily breaks into the 120-130 range. My son Shawn got some airtime in flying the Dynajet Stunter which was just all out an awesome experience and deafening. My friend and builder of the jet is mixing the concoction of 87 octane gas and methanol for the flight. The jet burns 18.5 oz's of fuel in under 4 minutes. Ken

Wow, those pulse jets are scary in several different ways. I'd like to watch one in real life sometime. Do you hold onto a pole to fly?

Regarding that shortened piston; I'm sure you know this already, but did you put it into a cylinder that was already ground for SPI with a regular piston? Also after all the shimming, does the top of the piston reach all the way to the head landing?

I planned all week and pre-flighted my planes, installed new bladders, loaded the wagon, and then... went wedding clothes shopping with my wife. Right before Football time and then thunder storms.

Rusty, pulse jets are quite unusual. They're for one extremely sensitive to fuel delivery. Rolling on bumpy or irregular ground on take off can cause the jet to immediately quit. As far as Dan (the builder and owner) is aware of, no one has successfully built and flown a control line pulse jet stunter in nearly 40+ years. The idea came from an old American Modeler mag and he was hooked on getting this done. This took extensive tank work and getting the metering jets correct. We tried several different fuels and finally settled on pump gas and methanol. My son Shawn flew the jet one handed for about 2 minutes and then both hands locked on the handle for the rest of the flight.The jet itself is weighing about 83 oz's without fuel. What is truly amazing is to see the jet go inverted. The jet can perform all the maneuvers of the AMA pattern, it just doesn't run long enough to do them consecutively. The other problem is the CG change as 18.5 oz's is burned from the nose of the plane and it becomes squirrely at the end of the flight.

Up until recently, I haven't really played around with my Cox stuff. This piston cylinder as I mentioned was purchased two maybe 3 years ago. What I did notice is that the engine was extremely hard to start until I lifted the cylinder reducing the SPI. This piston cylinder was purchased as a set. The piston didn't come up to the landing which I felt was to my benefit as I was trying to use a Glo Bee racing plug which really boosts the compression . I figured it wouldn't overcompress the engine and I was using 50% nitro. Initially I had two shims which I believe are .010 under the cylinder. I removed one and replaced it with .002" KK style shim. Paul Gibeault mentioned to me some years ago about the problems with running TD's on a regular tank. Without seeing the plane and tank, he knew exactly what the problem is. To date, I have only ONE TD that will run on a tank and this is due to taking Paul's advice. The problem is when the tank pickup is further outboard than the nipple on the TD's spraybar. You need a narrow tank which can't exceed 1/2" in width and it should be relatively long. I need to forget the tanks and go bladder it solves the problems associated with tanks. I spent a lot of time today trying to get a decent run and the tanks are always the problem. Either run backplate pressure or go bladder. I'm thinking it shouldn't be this difficult, but it really is and if you let it get to you it will make you aggravated. Ken

Great stuff Ken,

I wish there was a circle somewhere in OKC so I could drop by one and actually land a plane properly for once. That one being around since 1937 is a feat in and of itself.

Wish you had some video......hint hint

Sounds very angry.
https://www.youtube.com/watch?v=g459ElCbu9U&feature=relmfu

Ken Cook wrote: Rusty, pulse jets are quite unusual. They're for one extremely sensitive to fuel delivery. Rolling on bumpy or irregular ground on take off can cause the jet to immediately quit.

Well, they are reedies!

George

George, your so correct. In fact, the initial flights which took place in April of this year at the same field resulted in the reeds burning up repeatedly. The Dyna Jet head has to be absolutely flat which retains the petal reed. The problem with this equipment is the fact that the guys who know this stuff are either very old in age or are unfortunately not with us anymore. A speed flyer who helped us that afternoon is in his late seventies. He even said himself, remembering this is getting difficult. He provided us with about 20 different metering jets. We tried so many different fuels. Each fuel requiring different jets, once we found the set up, it worked magically. Here is the video of the first flights back in April. https://www.youtube.com/watch?v=mAcLaot_Xic The noise is just amazing. It now starts on 4-5 pumps. Ken

Ken,

I remember reading in a model mag about setting up a Dynajet head. If I remember correctly, they polished the head on glass to get it flat. I THINK they polished the reeds the same way. I have never run one, in fact I have only seen one run. It was in an F-86 scale jet back in ~1959. The plane was released immediately after it started, and when it landed a helper shot a CO2 fire extinguisher inside the fuselage. I did see a jet speed plane run on a Windy tape also.

Sounds like you are having a lot of fun.

George

George, Dan had this jet at the Nats this year. Some of the jet speed guys got a big kick out of it. Many people thought however it wouldn't stunt and would quit. I know the tank is on uniflow. To all of our surprise, the jet kept running. The article that Dan acquired some of this info from was indeed a 60's mag but a lot of the info was either missing or incorrect like the misprint where it meant to say the fuel tank needs to be 18 oz's and not 8. The fellows at the Nats did indeed do the plate glass technique while Dan was there. This immediately increased the run time and power. My son Shawn really impressed us flying it. Shawn is a very capable pilot. One of the contest we attend in the fall Windy is usually present filming. Dan himself completed one of the 1950's Mig-15 jets. I believe they were all Japanese kits possibly Eureka kits. He said the entire kit had to be literally replaced due to poor fits and parts that just weren't correct. The high stab on the vertical fin led to some considerable design changes. I know Windy has filmed the Mig in flight. Ken