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Car/buggy vs. heli vs. airplane engines

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Car/buggy vs. heli vs. airplane engines

Old 06-01-2006, 09:43 PM
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Fred420
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Default Car/buggy vs. heli vs. airplane engines

[sm=spinnyeyes.gif] OK so what is the real differance in engines? Why can I not use a car/buggy or heli engine in my 3D?
Old 06-02-2006, 09:18 AM
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Default RE: Car/buggy vs. heli vs. airplane engines

Heli engines have a carb optimized for mid range and generally a shorter crank shaft. The carb might be an annoyance but on the OS 50 and the heli 50 the threaded portion of the crank shaft is 7mm shorter, I doubt you would get a thrust plate, prop, washer and prop nut on the crank shaft. They are made for screwing on a fan and putting the prop nut on.
Old 06-02-2006, 10:38 AM
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Default RE: Car/buggy vs. heli vs. airplane engines

The biggest difference is in the port timing. The car engines are designed for high rpm. They trade torque for huge rpm, and you get the torque to the wheels back through gearing.

The same goes for heli engines - but to a lesser extent. They trade some torque for rpm to develop HP, and then use gearing to take advantage of the power. They are very similar to the aero engines, and in some cases are actually identical internally, and only incorporate a unique carb optimized to run at high rpm at mid and partial throttle settings - in order to hold constant head speed while varying the pitch/load. The three-needle carbs are good examples. Engines like the Hyper 50 and OS70 were definately designed for higher rpm, and with the right pinion selection and a good exhaust system they can really produce a ton of power. The heli engines also tend to have special physical features, like the heat sink head obviously, the shorter output shafts, or 1/4" threads - to keep with some installation requirements and industry compatibility.

For 3D work, you want to directly turn a larger diameter, somewhat flat pitch prop. Usually this ends up being at lower rpm. The midrange throttle is again important, but the difference here is that in midrange, the engine rpm falls back somewhat proportional to the throttle setting. So in this case, you want the carb designed for that type of operation, and you want to optimize the port timing and other aspects of the engine design for a better balance of torque and rpm.

An example I am personally familiar with...

The Jett 60LX - A ".40 size" sport engine engine, designed for higher rpm, high output. Comes with a tuned muffler for the 17,000 and up rpm range. Props like a 10x6 are perfect at 18,000 rpm. Carb is matched to the needs of this setup, and the fuel demands of a tuned muffler. Idle and transition are smooth and consistant. For a pattern type plane, speed ship, diamond dust, or for really hauling an old Sweet Stick around - its perfect.

The Jett 60L-H is the same engine. Same bore and stroke. Same physically and externally. However the port timing is different, the engine uses a non-tuned muffler, and the carb is matched more specifically for best fuel draw and very linear performance in midrange and hover points. In this case, this engine is intended for 3D, fun fly and profile flying, turning larger 11x5, 12x4, 12.25x3.25 props around 14,000+ peak rpm.

I trust this illustrates the difference a bit. It all comes down to how the engine is designed to do a specific job.

Marine - heli - speed car - buggy - sport plane - speed plane - racing - ducted fan - 3D
All have their own special needs.

Bob
Old 06-03-2006, 03:23 PM
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Kweasel
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Default RE: Car/buggy vs. heli vs. airplane engines

Most of the 28-36 heli engines make very good airplane engines as they are. Most of the carbs on larger heli engines are not right for airplanes. With an airplane carb and a tuned pipe 60-90 heli engines are usually more powerful than their airplane equivalent.
Old 06-05-2006, 08:38 AM
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Default RE: Car/buggy vs. heli vs. airplane engines


ORIGINAL: Kweasel

Most of the 28-36 heli engines make very good airplane engines as they are. Most of the carbs on larger heli engines are not right for airplanes. With an airplane carb and a tuned pipe 60-90 heli engines are usually more powerful than their airplane equivalent.
Yep, thats pretty much accurate. The OS 70H is a real killer engine on a prop and a pipe.
Old 06-06-2006, 02:43 AM
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Default RE: Car/buggy vs. heli vs. airplane engines

So ... do you think that my old TT39H (with a new ring!!!) will be OK for airplane use?
thanks
RTD
Old 06-06-2006, 08:12 AM
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Default RE: Car/buggy vs. heli vs. airplane engines

Sure..... as long as you can get a prop and prop nut on the shaft.

I would suggest running a tuned muffler like the jett-stream or ultrathrust, or a full-pipe. That engine in particular has some nice timing and pipe response. Use an 8x6 or 9x5 prop. Let it rip.

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