747-RCU

My Feedback: (22)

This might be seem like a dum question and may have been asked, but I just want to know that the specs on the servos state the torque and speed. I understand the torque part, but not sure what does the speed specify and what is better for what application. Can someone help me understand that.
Thanks

Charlie P.

It refers to the amount of time a servo's arm takes to transcribe a specified arc. A slower servo may give a more realistic response (or be preferred for a throttle), but a faster one might be preferable for 3-D or pattern, where fast response time can be appreciated. I believe some of the 'high-torque' servos are just geard down standard servos, making them slower but stronger.

rmh

The speed means very little on most of em.
The servos -in actual use move as fast as they can ,considering the load on them -
Consider this:
a servo has a motor and electronics capable of "X" amount of torque.
If we add a high speed gear train - the rated speed will be high (no load speed) but the rated torque will be low.
Now change just the gear ratio.
The rated speed (no load) will be slower but the rated torque will be higher.
Now add the load .This is the real world
The high speed servo may move the loaded surface slowly or not at all
The high torque servo moves the loaded surface faster.
It can be very confusing .
If the modle is tiny and light with small surfaces - you can use the fast rated servo
If the model has larger surfaces which will seea larger air load- go for more torque.
Don't forget, that the speed or torque , is no better than the battery supply to the servo.
a tiny battery trying to dump energy into a big high torque servo may be just as ineffective as a cheap faster rated servo.
keep asking questions - these servo/battery relationships are often ignored and you can spend a lot of money and get bad results.

747-RCU

My Feedback: (22)

Thanks fot the replies Dick hanson and Charlie.
I got a lot more info than I had before.

Now my understanding is .16sec/60 is more speed than .23sec/60, am I right here or no?

In plain terms, torque is more important than speed GENERALLY. And a good battery pack is a must for good performance, right??

What are the pros and cons of using 6V pack instead of 4.8V?

Thanks again.
Maqsood

Charlie P.

You got it.

Now for the bad news. 6v gives you more torque power, but substantially shorter flight time. The 6v packs run down to threshold voltage something like 25 or 30 % sooner. Doesn't seem fair or intuitive, but that's how it is.

I tend to over-simplify. Dick has some good insights in his response. Anything you can do to free-up the control surfaces so they move easily will pay rewards. If you're bottoming out because of balsa-on-balsa contact where a control surface was not prepared well, or a rod is binding along it's travel, you're putting unwanted load on a servo. A stalled servo sucks up power very quickly. Any time you hear that little "Bzzzzzz" at the endpoints you are paying for it in excessive battery drain.

rmh

grab your checkbook when or if you decide you have to have the "best"
make some thoughtful decisions on just what size model and type of flying you have in mind.
It may be that very simple lower powered servos are exactly the right choice.
For example - a servo such as JR's inexpensive 811 digital rated as 55 in ozs - is excellent for medium sized models using glo engines-
tho the torque rating and speed is ho hum - the actual holding ability - due to fast power update makes these very quick and tight around center .

blkbird68

My Feedback: (19)

Just to add some confusion and something else to think about.... when doing static testing when I built my power buss that I use, I found just the opposite to be true, running the system at 4.8V it consumed greater amperage than running the same tests at 6V, therefore, equal capacity packs of 4 and 5 cells under static conditions the 5 cell should take longer to draw down to "cutoff" voltage.....I did static testing by using servos loaded to half rated torque. but this was using my buss and deans connectors replacing the "stock" servo connectors,and dual 10amp capacity regs setting the voltages while using a 6 cell 3000mah pack as the supply.

Since I haven't run the system in the air with different voltages I can't say if it still holds true under actual flight conditions.

However I do agree that with the typical "stock" setup your observation is accurate.....kinda interesting I think....
As Dick pointed out, a servos speed under no load is not = to speed under load, and servos will try to run as fast as they can, maybe the servos are sending you a message.....give me the electromotive force I need under load and I will reward you with closer to spec performance. in other words, considering the large voltage losses I have seen in testing across "stock" connectors, they are acting as restrictors, with the higher pack voltage the losses are slightly less so the servo now can operate with a voltage closer to what it really needs. but at the expense of shorter pack life.