Utility of a governor, and throttle curves
by Steve Simpson [email protected]
> Hello, I understand the failsafe issues with the Governor so that you do not blow the engine. But how much of a risk is there to actually have your engine blow up on you.
In model helicopters, there will always be some load from the fan and factory heli’s tend to have somewhat conservative gearing so with a stock motor running low or no nitro as is common in Europe, it would take a pretty unusual set of circumstances to actually ‘blow up’ and engine.
In the US is common to have .30 size helis converted to .46 and running high nitro and tunes pipes. In this case your margin of safety gets pretty slim . . .
. and it doesn’t take a lot of coaxing for certain brands to spit rods . . particularly if the carb cannot maintain a rich mixture when the RPM’s suddenly go through the roof. Engine damage from over revving is cumulative though. Like smoking cigarettes. You don’t have to ‘blow up’ an engine all at once . . . it can be done over time . . . As with bending a paper clip back and forth . . . you get away with it the first few times.
There has been a lot of chatter recently about engine damage, but the greater danger is in overspeeding the head itself. Aerodynamics will limit how fast the rotor will turn without engine power because drag increases exponentially as the airflow accelerates the blade, so there is a natural ‘air brake’ of sorts.
However, when the rotor is spinning up via aerodynamic power, the engine is free to really give it shove into the ‘red’ zone. Spitting a rotor blade is a much more serious event than spitting a connecting rod.
> What other benefits do you reap from installing one into your heli?
One of the vexing things about model heli’s up until recently was attempting to provide for some type of ‘synthetic’ governing of engine speed. Early on it was with interconnected linkages and later with our friend the ‘throttle’ curve . .. . no matter how many points there are on a throttle curve, it is still a
static curve and cannot adapt to the various conflicting conditions found different flight maneuvers. Therefore, throttle ‘mixes’ are used to attempt to
give the basic curve some ability to adapt to situations that require more or less power than the basic static curve provides.
Even with all these tools available, often a mix ‘robs Peter to pay Paul’ and fixing one situation worsens another. The more power your heli has available and the more . . . ‘enthusiastic’ your flying style, the worse this situation becomes. While there is always a guru who claims to be able to get ‘perfect’ engine speed control, the fact is that some situations that cause over revving cannot be resolved by curves and mixes. Since these setting are all static, the only solution is to have multiple flight modes where a different set of settings can be stored. Then you simply switch to that mode when you anticipate the
situation.
Are we having fun yet?
A governor eliminates the need to worry about any of the stuff in this post . .
