DaveL322

John,

The flying I did was with a borrowed prop...I didn't measure it....some one else will have to check their prop

Regards,

DaveL322

NYA? Not yet available? But it appears to be in stock. The 21x14 is a pretty heavy load depending on the motor/ESC/lipo, but works very well on a lot of setups. It or the 20.5x14 are probably the most popular prop for F3A. The 20x15 will also work, but is best for a fairly fast flying style....it does not have nearly the downline braking with the higher pitch and lower diameter.

Regards,

nonstoprc

My Feedback: (90)

Thanks!

OhD

[/quote]

Limiting the throttle will not solve the problem. The readings we get on the meters are an average current. The ESC works by allowing full current to run to the motor in pulses, and throttle controls the rate of the pulses. Using the throttle to regulate the current will still let the full 94A or whatever get to the motor, just not as often.

However, if you are running 94A intermittantly, maybe it's OK for the ESC. I talked to Castle and they had me turn off my current overload protection since I fly F3A. We don't use full throttle that often, and I think the rating is max continuous current. Just double check that one as I'm fairly new at this.
[/quote]

Actually the ESC switches the full voltage on and off at a constant rate (I set mine to 8KHz) and the throttle regulates the duty cycle. At full throttle the duty cycle is 100% and the voltage to the motor is essentially DC at a level close to what you measure at the battery terminals. The motor will try to run at an rpm equal to that voltage times the Kv of the motor. The current increases with load which is determined by the size of the prop, the rpm and the forward speed of the plane. If you limit the throttle, the average voltage drops and the rpm drops, so the load decreases requiring less current. So if you want to reduce the current at full throttle to save your batteries for example, turning down the ATV will solve the problem.

If you are worried about burning up the ESC that is another question. I may be wrong but I believe it is heat due to power dissipation at less than full throttle that is hard on ESCs. There is an AC component in the RMS current that ends up in heat.
Read Bob Boucher's book and see if I've got it right.

Jim

serious power

Hi Chris,
Are you going to produce your packs as 10's brick, a la TP10SPL2.

Brian

DaveL322

Jim,

Several years ago, Castle had an article on this topic in their periodical newsletter, "Scrye", which has not been continued and is no longer on their website. According to the article, reducing the endpoints did not reduce the peak load seen by the battery, and lower voltage (from the higher load) from the battery generated more ripple current to the ESC, making the ESC work harder, in particular the capacitors on the front end. I don't remember the article being technical per se, but if it were, I'd be stretching to accurately convey more than the concept.

You know far more about the workings of this stuff than most, so maybe this concept fits with some possible scenarios you might have for how the ESC is working.

Regards,

OhD

Thanks for the feedback Dave. I'd like to see that article and I'd really like to talk to a guy that really knows what is going on inside ESCs. To me it is clear that lowering the end point reduces the load on the battery. We know that if we fly around at mid throttle we take a lot less energy out of the battery, so it follows that any amount you limit the high end will reduce the load. What happens to the current is more difficult to deduce. We know that it takes more current to turn a given prop at a higher rpm. So it follows that lowering the endpoint and rpm should lower the amount of current required. Do we still get the same peak current? I doubt it. What would determine it?

The higher ripple current I'll buy into. That is the AC I mentioned and I believe that is what the ESCs don't like.

I've been thinking about setting up a small motor on the bench and look at it with a scope but never seem to get to it.

Not sure this helps. I think everyone is agreed that ESCs don't like to be operated in the 60 to 90 percent duty cycle range but I don't think it is a peak current issue.

Jim

Chris Moon

My Feedback: (8)

Brian (Serious Power)

No plans for a 10S brick right now but that can always change if there is enough demand for one.

John (Wingster)

See attached pic of PT Model 21-14

nonstoprc

My Feedback: (90)

The data log seems indicating that the voltages are relatively stable (even drop) whenever there is current-drawn spike (see [link=http://www.rcuniverse.com/forum/m_7905478/mpage_38/key_/tm.htm]Post #945[/link]. I would think those moments correspond to the advance of throttle.

With a watt meter, one probably can easily find whether the current reading is linear to the position of the throttle.

2Sunny

delete: duplicate post

Alex Voicu

Can you please tell me the weight for the PT Model 21x14 or 20x13 prop?

What would be the PT equivalent of the APC 20x13 in terms of input power or RPM?

mups53

My Feedback: (41)

Guys I've been running the new Power Unlimited packs all season long. We like to refer to them as PUXFUpacks. At the Nats I was really pushing them hard with an average of 4200 mils pulled on my six competion flights. I'm happy to report that they are really hauling the mail so far. I couldn't be more pleased with their performance. They can take abuse and not have any lasting effect.I also had some Zippy 5000 15C's and a Rhino 4900 20C packs and these are significantly more powerful. They are the only packs I will use in competition. I'm running an AXI F3A in my Integral with a Rasa 20.5x14 prop. My WOT amps are about 80. It's a very powerful setup and allows a wide open faster style that I like. I'm flying the AMAMasters schedule and it's long and these packs deliver all the way to the end.
They have the advantage of a lower weight with a higher C rating which makes a big difference. Mike