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Old Jul 06, 2012, 02:35 AM
Bicycle clown
Shuffle's Avatar
Helsinki, Finland
Joined Feb 2010
399 Posts
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Powerful retract servos?

I got good giant-scale retract systems. I am running them with these:

http://www.hobbyking.com/hobbyking/s...ACT_Servo.html

Problem is, i need just a bit more torque to get my all systems work 100% well.
What kind of servos would you suggest? I need around 10-12kg torque.
Yes, normal servos are fast but their advantage is that you adjust the end points with them, which is a big plus.
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Old Jul 06, 2012, 01:28 PM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
12,900 Posts
Up the servo voltage ?, unless you are already running 6v.

Add some spring biasing to the legs to reduce the load ?.

One nice thing about using standard servos, (as against retract servos), you can add a servo slow to slow the undercarriage down. looks more scale.

Ouch!, did you read the reviews on that HK link ?. (Scroll down the link).
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Old Jul 06, 2012, 11:37 PM
Bicycle clown
Shuffle's Avatar
Helsinki, Finland
Joined Feb 2010
399 Posts
Quote:
Originally Posted by eflightray View Post
Up the servo voltage ?, unless you are already running 6v.

Add some spring biasing to the legs to reduce the load ?.

One nice thing about using standard servos, (as against retract servos), you can add a servo slow to slow the undercarriage down. looks more scale.

Ouch!, did you read the reviews on that HK link ?. (Scroll down the link).
Allready using springs and 6V No, i don"t read reviews of HK, i just use them They are fine for their price.
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Old Jul 15, 2012, 07:42 AM
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Canada, ON, Windsor
Joined Apr 2008
972 Posts
Some of the newer HV servos have some serious torque, well above the 200oz/in rating. 4.5-6V rated swash servos for larger helis or control servos for jet gear can be quite strong.

The problem is these become expensive. However, along with paying for performance you are also investing in reliability. I have seen MANY of those less expensive HK metal gear servos fail or become very sloppy with little use. Many also make the mistake of having the entire gear train from motor to output shaft made from metal. This provides a direct path for RF and interference created in the motor right to the output. Add a metal servo arm and things get even worse. If you look at a lot of the higher end gear the first gear from the motor, (and the one under the lowest loads) will frequently be fabbed from an insulating form of composite.

It sounds like you will be pushing them near the top end of their output torque and that means high current demands. If you go digitals the current demand is even higher. Slow the sweep speed down and it will spend a LOT more time with with those high currents through the board, motor and servo leads/connectors, so you do the math on reliability.
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Old Jul 15, 2012, 11:03 AM
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43851E's Avatar
College Station, TX
Joined Jul 2009
882 Posts
Shuffle,

You said that you were running the servo network on 6Vdc, Try to measure the voltage while your servos are in acuation. And or possibly hook the system up to a bench supply (lots of available current) and seen if having more current available improves things. Then if there seems to be an improvment, you will need to consider a new or improved voltage/current source onboard. This may include larger wires in the circuit maybe?

Doug
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