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LohringMiller

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About LohringMiller

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    Boater
  • Birthday 03/05/1943

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    Male
  • Location
    Eugene, OR

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  1. LohringMiller

    Tuned Pipe Wave Velocity

    We never had problems with the magnetic sensors except on the electric hydro. There we ran the sensor on the propeller shaft because the motors magnetic field overwhelmed anything the tiny magnets put out. We still ran it close to some big magnetic fields. The little wire on the last picture is the Hall sensor wire. The big wires were sized for 1000 amps. I ran magnetic sensors on model outboard flywheels as well as the shaft coupler on Zenoahs. See below. I included the thermocouple holder I made for EGT sensing. It's pictured on a crackerbox exhaust extension. Maybe you have a bad unit or Hall sensor. Eagle Trees are model, not aircraft grade grade. We've gone through several, especially when they got wet. Lohring Miller
  2. LohringMiller

    Tuned Pipe Wave Velocity

    EngMod2T has Tom's tuning calculations included. Some other interesting tools are available on this site. The dyno software can be used with an inertial dyno but not for a boat. The drag is too hard to estimate accurately enough. We verified the simulations on an inertial dyno as well as with Eagle Tree data loggers in the boats. The inertial dyno software and data logger costs around $1000. We machined the flywheel, but I would expect you could have it made by a machine shop for around another $1000. An article on all this is available from Model Engine Maker issue 15. There's a lot of on line information as well. I have a spreadsheet for size and stress calculations. The best article on one of our engine modification programs is here. Another article on our gasoline test series in a modified Zenoah is here. We ran the simplest Eagle Tree data logger with an rpm and GPS module. That gives all the information you need but I have measured EGT both on the dyno and in the boat. It wasn't particularly useful at our state of sophistication. The rpm vs time curve on an accelerating boat has a very similar shape to the rpm vs time curve on the inertial dyno. Power is a very sensitive indicator of scavenging efficiency in a two stroke. Gordan Blair went a lot farther at Queens University of Belfast with his Yahama 250 cylinder test series. Even so, he verified the scavenging rig results with inertial dyno testing. Some of the designs tested are below. With very few exceptions, model engines have the poorest transfer passage designs. Lohring Miller
  3. LohringMiller

    Tuned Pipe Wave Velocity

    It's not expensive these days to do the thermodynamic calculations in a two stroke (or a four stroke) engine. Scavenging is a lot tougher problem and requires a full 3D model with a computational flow program. It has been done, though. The model most people I know use is one dimensional. It works very well for pipe and port design using empirical models for scavenging and combustion. The program is EngMod2T costing around $400 and comes with forever updating. It is based on Gordon Blair's work outlined in "The Design and Simulation of Two-Stroke Engines" mentioned above. EngMod has been improved over the years with inputs from around the world by the best two stroke tuners. It also contains great versions of the empirical pipe design and time area programs that were used for years. I can't recommend using it if you aren't very serious about engine design. The available commercial pipes are very good. All you need to do is tweak your port timing and pipe length to get the best performance from the hull and propeller you are running. That's not trivial, though. LOL Lohring Miller
  4. LohringMiller

    Tuned Pipe Wave Velocity

    The catch with measured EGT is where do you measure it. For the empirical pipe design "programs" you are looking for some arbitrary average sound velocity. A good simulator will calculate the actual temperatures, velocities, and mass flows all through the engine. These are determined by the combustion model. However, in inexpensive simulation programs that's somewhat arbitrary but still more realistic. The temperatures I've used in the above programs for gasoline engine pipes are between 400 and 600 degrees C depending on the state of tune. Nitro fuels are cooler, but I haven't done designs for nitro engines. Another area that has seen serious experimentation is the shape of the passage between the port and the header. Cooling the header and that transition area is also important. The feeling in high performance small two strokes has been that you need to keep heat in the pipe, but cool the exhaust flange area. Some mixture spills out of the exhaust and is forced back into the cylinder, supercharging the engine. Cooling the exhaust flange area acts like an intercooler on a turbo. Keeping heat in the pipe preserves the energy of the exhaust pulse. The diagram below shows a transition that works well with highly tuned engines with triple exhaust ports. ABC engines with similar wide ports should also benefit. Lohring Miller
  5. LohringMiller

    Tuned Pipe Wave Velocity

    This has been interesting. As Dave points out, you need to match an empirical design from some canned program with lots of testing. I've done that with quite a few gasoline engine pipes. Better than empirical programs are engine simulation programs. The one I use, EngMod2T, even has a glow engine combustion model and a large choice of fuels. The model inputs need to be realistic and match real world dyno results. That takes accurate measurements on a real engine. I have not played with nitro pipes other than to run commercial ones and adjust the tuned length. The basic mechanical design factors are maximum diameter, baffle cone position and angle, and diffuser length and horn coefficient. A guess at an appropriate average exhaust temperature sets the various lengths and positions. I would start at 250 degrees Centigrade for nitro. Then you run a dyno test to see if the rpm you were designing for is actually the peak power rpm. If not, you guessed wrong on the temperature and it's back to the drawing board. Below is a starting point for design that has been successful for gasoline engines. A spread sheet is also available. By the way, Brian Buaas has built several carbon fiber pipes for small engines. One was used on a winning boat at the NAVIGA Worlds. Lohring Miller
  6. As far as I'm concerned you own the Leecraft name. If Tommy says it's OK it's fine with me. Lohring Miller
  7. LohringMiller

    Engine Cooling

    Great minds think alike. Yours and the person I stole this from, not me. Lohring Miller
  8. LohringMiller

    Engine Cooling

    I'm not sure how much difference coatings would make in our small engines. Another approach is to make the head button so only the plug threads and squish areas are cooled. The head button looks something like yours but with a cylindrical area where you have a rounded corner on the outside over the combustion chamber. Water is routed around the squish and around the plug, but not over the combustion chamber. Heat loss issues should be more pressing with gasoline since it has higher combustion temperatures. Lohring Miller
  9. LohringMiller

    tunnel bottom side ?

    We've tested a lot of hulls. The basic ideas behind the hydrodynamics and aerodynamics is summarized in my series of articles on high speed boat design in the NAMBA Propwash: http://namba.com/content/library/propwash/2016/October/#16/ http://namba.com/content/library/propwash/2017/April/#14/ http://namba.com/content/library/propwash/2017/October/14/ http://namba.com/content/library/propwash/2018/April/8/ Lohring Miller
  10. LohringMiller

    Lipo Batteries

    I also see that the maximum capacity is 6000 mah. These limits only apply to NAMBA 1/8 scale electrics, not all classes. Lohring Miller
  11. LohringMiller

    tunnel bottom side ?

    To me the biggest advance in smaller tunnels was the increase in sponson dead rise angle. The deep vee effect gives better handling in rough water but the issue then becomes cornering. The universal solution has been stumble blocks to keep the bow up in the turn. For comparison the Shaman has 17 degree dead rise on the left sponson and 20 degrees on the right. Most other tunnels use 15 degrees on both sponsons. Different sponson heights on the right and left sponson also help in the turns. The biggest factor in high speed running is the tunnel width, length, angle and position relative to the sponson trailing edge and angle of attack. Very fine adjustments between the sponson and tunnel wing angle of attack determine the flight characteristics at speed. Lohring Miller
  12. LohringMiller

    Engine Cooling

    Below is some cooling information from a very experienced two stroke tuner: All the testing I have done with water cooling more , or less , in certain areas, sees only small gains individually. But combine them and the effect is synergistic. Arrange the plug threads to have water close , cut a ditch above the squish band with coolant holes from that , dropping right up close to the boundary layer , ceramic coat the chamber only as well as the area inside the squish on the piston, have the coolest water flow passing over the transfers first - then around the exhaust - then across the head and out. All these together make an engine that is HUGELY deto resistant, makes more power, and is way less influenced by tuning errors, be they too rich or too lean. As an example of just one experiment was changing the coolant flow on a TM - KZ10C.By moving the water entry to above the boost port as well as drilling 1/8" holes in the water plugs blanking flow underneath the Exhaust duct and then rebiasing the area of access holes into the head was worth just over 1 HP . But take away the Ex duct coolant holes and ceramic coat the Ex internally duct lost just over 1 Hp but even very conservatively tuned it detoed like hell , to the point I aborted the dyno run. Lohring Miller
  13. Our boats used the logo below. Lohring Miller Factory Team logo Red.bmp
  14. I have a wooden version that Arno built to use as a plug. We never did anything with the boat, but Alfred loved the design and went forward with a glass version. The design follows the Pacific Northwest sport hydro design evolution that spawned several boats. The current ones I can think of are the Mutt II sport 40, the Snake sport 20, and this hull. Lohring Miller
  15. LohringMiller

    RIP Kevin Taylor

    Long time boater Kevin Taylor from the Las Vegas Challengets RC Boat Club died in his big Race Boat in the Parker Enduro. I met Kevin at the dawn of gas boat racing when he owned R&R Prop Shop. He did props for both model and full size boats. He was the main prop supplier for west coast gas boaters and the NAMBA gas director. Below is a picture of Kevin talking to Al Waters at the 1998 NAMBA Nationals. Lohring Miller
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