SERVO TRAVEL improvement question

[raolguio]

Hi, I really need help in this mater.

Please read these fact before anwser my question:

1- I now the digital servos can be programed through servo programers, like the Hitec HPP-20.

2- There are some servo stretcher to improve the travel of the servo up to 180° or more.

3- You can also solder some resistor to the servo to improve this function.

My question is: if I bought a transmitter like the Futaba 4PKS, would I be able to improve the travel of ANY servo (analog or digital) just using the functions of the transmiter like the EPA?. or are this function only for little adjustments?. Would this radio be enough? or should I do some of the earlier modifications mentioned?

I don't know how the EPA function works, becuase I only have the stock HPI radio of the Wheely King.

I want to improve my WK steering radio, there is still some gap between the max turn radio and the axle. Right know I have a traxxas 2056 servo.

PLEASE HELP........

[raolguio]

would anyone be so kind as to help me in this issue??

[Narly1]

OK, I will try to help you as best I can without knowing the finer points of the 4PKS.

A good place to start is with the following link which explains how the pulse width of the signal coming from the receiver relates to servo position (in the case of the Hitec 7950TH):

http://www.servocity.com/html/hs-7950th_servo.html

Note how 600 usec corresponds to and angular position of 0 degrees, 2400 usec corresponds to an angular position of 180 degrees, and that center is 1500 usec.

In the case of a servo with 90 degrees of travel, 1200 usec corresponds to 0 degrees and 2000 usec corresponds to 90 degrees. Center is still 1500 usec.

Most transmitter/receiver sets are set up to drive servos with 90 degrees of travel.

Now this is where things get tricky. Depending on the brand of radio, you get a different range of pulse widths below 1200 usec and above 2000 usec, when the EPA's are set to their maximum values. What confuses the situation even more is that the EPA "values" shown on your transmitter (if it has a display screen) are entirely arbitrary and have no relation from transmitter brand to brand.

So to answer your question, the only guaranteed (and probably the best) way to get the travel you require is to buy a fancy digital servo (like the 7950TH) and program it so that it travels to the left and right extremes (mechanical steering limits) when your transmitter steering is at full left and right WITH THE EPA'S "MAXXED OUT".

The reason for having the EPA's maxxed out during the programming exercise is so that you can't over-travel the servo against the mechanical limits and burn it out.

In short you don't need a new radio to get the extra travel, just a programmable-travel servo.

Hope this helps,

Narly1

[raolguio]

Thanks, it was very useful.
Are only Hitec servos programable? I haven't seen any other brand servo programer.
1- Futaba has one, but is specific for just one servo
2- there is another brand that I can recall, but it only offers servo programer for micro-servos.

[Narly1]

Originally Posted by raolguio

Thanks, it was very useful.
Are only Hitec servos programable? I haven't seen any other brand servo programer.
1- Futaba has one, but is specific for just one servo
2- there is another brand that I can recall, but it only offers servo programer for micro-servos.

Can't help you out there, sir.

Whatever you get for a servo, you are going to want high torque as well.

An additional benefit of a long-travel servo is that it often allows you to run a shorter servo arm, which, in effect, means more usable steering torque.

For example my own rig:



Note how I am still able to run a perfectly straight drag link even though it is raised up on the knuckles with spacers.

Narly1

[raolguio]

Thanks again, I will follow your advice.

the Wheely king is my first RC (four months ago) and at the beginnig I just wanted it to be waterproof, that's the reason I chose the traxxas servo. But, right know I realise it doesn't have enough torque. Trial and error is the best way to get into this hobby, I guess