Probably because it works. The present owners, of the company, it seems are not too interested in any further R&D and just manufacture the props, etc to IVO's specs.

 

The CB is designed to break at 10A (+tolerances) Just before it reaches its limit, a plastic washer-like device compresses railing the amperage draw. The basic circuit has a spring loaded on off on switch. If the breaker breaks, just reset it and go on your merry way. Not a great system. There are various circuits that are available to make this more manageable by stopping the movement before CB activation. I think that their constant speed attachment takes care of this also. Popping the breaker, is actually no in that when you are in the situation where it might pop, you are either on the ground (prior to TO), setting it for cruise or flattening the prop prior to landing. In each one of these situations, the prop will stay at the pitch that popped the breaker and you are not in a critical part of flight in which you will need to change the pitch.

 

Kinda a sucky system, but effective.

 

I have the constant speed attachment.. which some don't seem to like, however in reading a lot of the comments on flying ivos, even those who really like them,

 

 

Now to poly fuses. A great idea, however-------

 

The way poly fuses work is that there is a conductive material imbedded in an epoxy-type matrix. This matrix expands with heat and causes high resistance at a calibrated temperature separating the conductor material (carbon).

 

It is my opinion, contradicted by some  others that in an aircraft cabin environment where the poly fuse can be in an environment of varying temperatures, (heat soaked cockpit on startup) to very cold, that the calibration, ie circuit release amperage is not specific enough for me and may break prior to or after a safe point (safe being determined by the physical stopping of the motor at its extreme Most fuses are scheduled to protect the wire to which they are connected, most of the time the load is a small percentage of the fuse value. On the IVO the selected value of the breaker is to stop the motor when it has reached a specific point -- to physically protect the load, not necessarily the wires. A similar concept is used in the electric actuators for the Cozy nose gear. The breaker will pop before damage can be caused to the aircraft should the nose wheel be cocked during retraction. Or for other circuits,

I really wanted to use them in my aircraft, but chose not to because of this characteristic. I am told that the remanufactured fuse less units that mimic poly fuses do not actually use poly fuses for that reason.

 

Rich

 

Kelly Troyer wrote:
> Rich,
>   I agree on your assessment on the use of the prop to control
> rpm.............The ammeter is merely a tool to avoid
> poping the IVO adjust motor elect breaker when reaching both the fine or
> coarse pitch limit stops and with
> enough use the pilot can learn to approx where the prop is pitched
> to.............Several of our group flying behind
> or ahead of the IVO use an ammeter for this purpose..............
> 

Why in the world would IVO use a device that is designed to fail critical flight gear in the case of improper control
manipulation when they don't have to?  Isn't this the classical and proper application for a polyfuse?  Polyfuses are
used in power windows for this exact reason.  You're kids can pull on that switch all day without damaging the window
motor.  I'm thinking of the case where a switch gets shorted (like my belt sander's switch is right now...the power cord
is serving as a temp fix until I get time), or someone accidentally leans something against the switch.

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