Why do you use HV and / or why don't you?

[DeathHorse]

Well we could make the HSB 9380 push 800oz if we wanted to, but the case, geartrain, and wiring wouldn't handle the loads so we made it more conservatively powered.

A standard or coreless digital will slow down as the servo arm nears its outer control throw limit because the loads tend to be their greatest out at those points from the airflow on the control surfaces trying to push everything back. Brushless servos don't slow down (not nearly as much) as the control throw nears the outside limits because of all of the additional power available with the motor. You can still stall a brushless servo, but it's more difficult to do. It's almost like having a servo with more torque.

Interesting. I figured there might be an advantage here. Someone should test speed under load.

This can explain why you won't get a linear scale of diminished torque with a longer arm when comparing to other standard or coreless digital servos. Like I said, you guys are more than welcome to do your own testing if you wish to see for yourself.

Provided you max the arm out at one inch you'll always get 1/2 the torque by weight going to a 2" arm. 100oz/1" and 50oz/2" are two ways of saying the exact same thing. It's like saying 24 inches instead of 2 feet.

 

[3D-Joy]

^^^^^
X amount of torque coming from any motor on the planet will ALWAYS be exactly X amount of torque. Again, if you see anything else than a flat line on a graph which use distance and force for scales, you did something wrong. There is no way around it sorry.

The servo does not know which arm lenght is attached to it, all it does is try its best to get to the commanded position, be it end point or center, it also does not make any difference.

 

[Jetpainter]

^^^^^
X amount of torque coming from any motor on the planet will ALWAYS be exactly X amount of torque.

Yes, but does torque curve change with motor RPM like a gas engine? Or another question does the motor produce more torque when moving that holding?

Interesting discussion by the way.

 

[crashflow]

give me oh say 9 servos and I will test them

 

[DeathHorse]

Yes, but does torque curve change with motor RPM like a gas engine? Or another question does the motor produce more torque when moving that holding?

There's very little torque curve in a brushless motor relative to a gas engine.

Torque would be holding a load and horsepower (watts) would be the combination of the amount of work and how fast it is done so I don't think torque really describes how fast it is being moved.

 

[bigblueswope]

Torque from servo remains constant. Torque applied to the surface is a factor of arm length.

 

[WMcNabb]

This may take the thread slightly off topic because it's not directly related to Terry's question on HV...

I understand the idea of testing servos side by side for comparative purposes with different power systems (HV, regulated, etc.).

The bigger question for me is...

Toward the end of the last flight of the day, meaning lower voltage on the packs, but still flying hard, meaning loading and unloading multiple servos, how does one know the servos are sized correctly for the airplane?

 

[DeathHorse]

It doesn't easily knife edge loop even if you have super high throws on the ground. If rifle rolls are noticeably slower at high speed.

Those kind of things would be signs of blowback.

You also need to make sure the servos are getting sufficient power, both from the batteries and via the wires.

 

[Terryscustom]

OK, so here is a dumb question. I'm thinking of trying a couple of LiPo's but I need to put a regulator in my plane because I'm not going to rush out right now and buy new servos for 8 GS planes. I will have to slowly switch over. I am looking at two regulators from two different companies that I can regulate to 6.6 volts. One of the regs also has internal battery matching and isolation features.

- So my question is, has anyone heard of any issues with a Spektrum power safe RX that is fed by a regulator that also has power safe features??

My simple way of thinking is the answer is no, because the RX should not care less how it is being fed.

 

[stangflyer]

OK, so here is a dumb question. I'm thinking of trying a couple of LiPo's but I need to put a regulator in my plane because I'm not going to rush out right now and buy new servos for 8 GS planes. I will have to slowly switch over. I am looking at two regulators from two different companies that I can regulate to 6.6 volts. One of the regs also has internal battery matching and isolation features.

- So my question is, has anyone heard of any issues with a Spektrum power safe RX that is fed by a regulator that also has power safe features??

My simple way of thinking is the answer is no, because the RX should not care less how it is being fed.

To some extent Terry, you are correct. Most all rx's don't care "HOW" they are fed. But the biggest thing to remember, is to allow for a constant "UN-INTERRUPTED" power supply for the rx. I have read and seen some systems set up in such a way that servos were drawing power through the rx. and thus high demand from HV servos have been reported as drawing so much, that the rx itself "starves" for voltage. Dropping below the nominal 3.3 or so volts, causing brown out and complete loss failures. I know a lot of you out there don't use the SF boards, a lot of you have power safe rx. that allow battery redundancy. But the biggest reason I have used and continue to use the SF boards is because the SF powers up the rx to a constant 5 volts. With absolutely no risk of losing voltage, (unless the batteries are drained) And also allows battery redundancy for the rx. as well. While supplying a direct supplied voltage to each servo. Pluse with the SF boards, you also have internal battery matching and isolation features. As for using a regulator to utilize two lipos is a sound idea. Fromeco and SF both have some awesome regs. I have used both in the past. I think I like the Sahara from Fromeco best. I don't know Spektrum, but I would say if you are using a power safe version, You're covered except for the servos. You would need to find a way to regulate the servos to the 6.6 volts you are looking for. If you regulate the entire system, such as two regs, one to each battery connection on the power safe rx, then you are covered completely. And since you are not using HV serovs, you most definitely are not going to be starving the rx. for needed voltage. Unless you are considering a single reg that will give you the battery redundancy along with the battery matching and isolation features. Then in that case, You're set!!

I truly am a "HUGE" advocate of the SF boards. Battery redundancy, constant un-interrupted 5.0 volts to the rx., and battery redundancy of battery supplied voltage to my servos. If I were using a normal voltage servo system, I would go the route you are thinking.

These are just my thoughts. Maybe someone knows of a better way?