Sneak Peek - JC Designs Protos Max V2 Gas Conversion

[KSHeli]

Originally Posted by jharkin

... but if it's heavier than a typical rc format heli, it needs more power just to break even performance wise....


???

Jeremy the Protos is a heavy heli to begin with and just another gasser build of a newer model that they are using to validate the prototype motor in. As stated by Carey, when the motor is finally validated, then conversion parts for other models may be produced to use this motor. Then we may have an ultra light gasser in another model.

[rbort]

Big transformers have fin plates sticking out all around the transformer box for this purpose. More material means the heat has to travel through all of it and warm it all up for more heat to build. If big enough some of that material will shed some heat ready for more and keep the temps down.

But not to say you can't use a puh style format engine in the heli, the 1005 was always like that and it works though it not as cool running than the RC motor in general. In the winter it doesn't matter, in the summer you need a better fan. I'm sure your design has a very good fan so its not going to be an issue unless its very hot outside maybe.

Keep up the good work!

-=>Raja.

[jharkin]

Once upon a time I did take college level heat transfer.... Sowa is right on this one...


Material mass does not determine how well the engine dissipates heat. The mass is just a buffer, like a capacitor in an electrical system - it helps to moderate wild swings in temperature but it has no impact on the steady state temp with a given amount of heat input. The steady state temp is determined by how well the system can transfer that heat energy to the outside environment (the air in this case). More fins improve cooling efficiency because they increase the surface area to convect and radiate heat from the metal to the cooling airflow. The ideal configuration from a heat transfer perspective would be to make the fins as thin as possible so you can stuff in as many as possible (think an A/C condenser) but that doesn't work well on an air cooled cylinder head because the result is fragile and subject to cracking from vibration. So we make the fins heavier which adds mass.

Notice that the equation for heat transfer by convection (the dominate method where the air is force fed through the fins by a fan) doesn't even have a term for mass:
http://www.engineeringtoolbox.com/co...fer-d_430.html

[rbort]

When there is more material and mass, the heat has to propagate to all this mass and spreads the heat out throughout the engine and away from the cylinder.

The extra mass has more air exposure, and this extra material sheds off more heat than if there is less material.

It has been my experience in the past the more material is better than less. A simple example if putting a heat sink of a regulator. If you run the regulator without a heat sink, then it will overheat and burn up. But add a heat sink to it, and the heat transfers from the regulator to the rest of the material which sheds the heat off and prevents the IC regulator from burning up. Does that make sense as to what I'm saying now? It works the same way with engines. More material is better than less.

-=>Raja.

[prototype3a]

I wonder if an engine could be made to use off the shelf heatsinks from someone like Alpha Novatech. This way, if damaged, they could be easily replaced and it removes the requirement of the engine manufacturer to machine or cast the fins.

[carey shurley]

well I'll say this, if you've hit the ground hard enough to damage the fins on the engine, repairing/replacing the fins probably won't be important

[goof2]

Raja
Don't get mass and area mixed up. You can ad more area without adding mass.

[carey shurley]

A couple of videos made by Doug Darby and Tom Welch of Jesse Kavros flying one of the Protos prototypes at IRCHA today:

Protos Gasser IRCHA 2017 (5 min 18 sec)

Protos Prototype Gasser (5 min 11 sec)

[HelisRock]

Absolutely awesome to see the prototype coming along so well

[Atomic Skull]

Originally Posted by jharkin

I thought it should be easy to beat those with your ultralight engine? Is the Protos just very heavy to start with?

The Protos is really an 800 with a shortened boom in it's "stock" form. Like the Rush 750 it was designed with longer blades in mind before they realized that helis larger than 700 don't really sell all that well so they clipped the boom and blades and offered it as a 700 with the option to "stretch" it to 800.

[jharkin]

Originally Posted by Atomic Skull

The Protos is really an 800 with a shortened boom in it's "stock" form. Like the Rush 750 it was designed with longer blades in mind before they realized that helis larger than 700 don't really sell all that well so they clipped the boom and blades and offered it as a 700 with the option to "stretch" it to 800.

OK fine... but my point was that this build was advertised at the start with this tagline:

Originally Posted by jc23cl

The Airframe and Motor will push the boundaries of what's possible in Gasser performance (we believe),

...implying the goal was to make this the lightest gasser yet. But it sounds like the reality is its one of the heavier ones.

[carey shurley]

So with the introduction of the Protos Nitro, its likely possible to take advantage of the gear drive system which would return the rotor head to a typical right hand rotation

it would also limit the drive ratio choices as the belt drive version as its simpler to acquire/make the pulleys than it is other gear options. At this point I would assume that the large main drive gear can be installed on either version of the protos.

curious what the interest level is in using the protos nitro as a base as opposed to the original belt drive version.

[Colin Broughton]

I'll buy a protos nitro kit for a gasser conversion in a heart beat

Plus having a clock wise rotating head is a huge plus

[Dawiev]

Originally Posted by carey shurley

.... curious what the interest level is in using the protos nitro as a base as opposed to the original belt drive version.

I cannot recall any airframes for sale since I've been watching those sections. I would hazard a guess that most builds would be a new basic kit and the conversion ?

[carey shurley]

Plus having a clock wise rotating head is a huge plus

out of curiosity, what is that plus? The pilots that have flown the counter clockwise prototype have only said that some maneuvers either had to be started differently or required opposite different corrections

[Colin Broughton]

Originally Posted by carey shurley

out of curiosity, what is that plus? The pilots that have flown the counter clockwise prototype have only said that some maneuvers either had to be started differently or required opposite different corrections

You have to get use to the heli leaning the opposite direction. That to me seems like it would take some adjusting on your thumbs to fly your regular routines on say a clockwise rotation leaning the "normal direction" I've learnt to fly certain manuovers giving aileron correction compensate, so if I grabbed the protos next flight I'll be chasing the heli? Or am I wrong on this assumption?

[brw0513]

Any updates on this project?

[carey shurley]

waiting to see the Protos Nitro. This would address the concerns over the rotor head rotation direction

[brw0513]

Maybe a silly idea, but can you get that bespoke engine to run backwards so the head spins in the conventional direction?

[carey shurley]

no its not silly at all, its been discussed several times

however since the engine can only be spin started, you'd need to have a reverse spinning starter just for this model.

its not that hard to do but it would be another oddity about the platform.