Restricted servo movement

[lnvisiblemanParticipant @lnvisibleman]

[lnvisiblemanParticipant @lnvisibleman]

Hi folks

I have just puchased a seconhand r/c set up and have a bit of a problem, or not if I am an idiot.

I have connected it all up on the bench and the motor works fine. However, there is only about 60 degrees of movement on the servos, 30 degrees in each direction. Any of you have any idea as to the cause of this and how to rectify it??

 

Edited By lnvibleman on 05/02/2013 18:40:27

Edited By lnvibleman on 05/02/2013 18:40:41

[The Long BuildParticipant @thelongbuild]

What is the TX set, as some set can be set to reduce the turn.

[lnvisiblemanParticipant @lnvisibleman]

It'a flysky unfortunately !!

[Colin BishopModerator @colinbishop34627]

Do the instructions with the TX mention how to change servo 'throw'?

Colin

[lnvisiblemanParticipant @lnvisibleman]

They probably do but I don't have them.

I'd guess they were in Chinese anyway so I doubt it would help .

[Mike PendleburyParticipant @mikependlebury45959]

You can download the manuals in pdf format at this site:

**LINK**

Just chose the model number on your transmitter.

They are in English as well as Chinese.

Mike

[lnvisiblemanParticipant @lnvisibleman]

Thanks Mike, done that.

What exactly am I looking for in the manual?

I really am very new to this mularky !

[Mike PendleburyParticipant @mikependlebury45959]

You are looking to see if there is a section that allows you to set the "end point" for the servo. This controls the amount of servo travel.

Assuming the physical stops inside the gear train of the servo allow it, then many of them can be set to swing up to nearly 180 degrees total travel.

Mike

[lnvisiblemanParticipant @lnvisibleman]

Ok, there is nothing even remotely like that in the manual. It just tells me how to connect it up and even I am not that stupid (?????)

[Paul TParticipant @pault84577]

What is the type and serial of the servos and did they come with the purchase?

Paul

[lnvisiblemanParticipant @lnvisibleman]

Hi Paul. The servos are HOBBYKING type HK15138 and were purchased newfrom a different source to the TX & RX

[Paul TParticipant @pault84577]

From the limited information that I have seen the HK15138 technical details specify 60deg of travel so without further information the conclusion is that your equipment is working correctly.

Spec as follows.

HK15138 Standard Analog Servo

Spec.
Torque: 3.8kg @ 4.8v, 4.3kg @ 6v
Weight: 38g

Speed: 0.21 / 60deg @4.8v, 0.17 / 60deg @ 6v
Voltage:4.8v~6v
Plug: JR Style

I hope this helps solve your problem.

Paul

[Paul TParticipant @pault84577]

Having thought further I realise that whilst answering your question I haven't helped solve the problem so I suggest that there are three courses of action available to you.

1/ Open the servos and change the internals to suit your requirements (difficult)

2/ Change the servos for equipment that has the necessary amount of travel.

3/ Use gears or linkages to increase the operational range of the existing servos.

Paul

[lnvisiblemanParticipant @lnvisibleman]

Thanks for that ! I have been looking at specs for loads of servos and I seem unable to find info on rotational range of each type. Is this available or do I just take my chances and hope that replacements will be OK ?

Is there any possibility that the TX/RX can have any effect on the rotation?

I ask simply because the same servos, when used with a freinds TX/RX, have a slightly greater rotation.

[Malcolm FraryParticipant @malcolmfrary95515]

If it's going to work a rudder, 60degrees is probably just fine, as long as tiller and servo arm are the same length. If using a single rod to connect them and 30degrees each side is not enough, the relative lengths can always be tweaked a bit.

[Colin BishopModerator @colinbishop34627]

You would rarely need more than 30 degrees on a conventional rudder, any more and it just creates drag.

If you do need more rotation have a look at ACTion Electronics' Servomorph which extends the throw of servos: **LINK**

Colin

[lnvisiblemanParticipant @lnvisibleman]

The truth is, I was looking for more movement to operate the reversing and speed control on a steam engine,

[lnvisiblemanParticipant @lnvisibleman]

To obtain full speed in both forward and reverse, I will need at least 60 degrees movement from centre

[Paul TParticipant @pault84577]

You can use gears or mechanical multipliers to increase the range of a servo.

[Colin BishopModerator @colinbishop34627]

The ACTion unit mentioned above is intended for that sort of situation but, a Paul says, you can do the same thing mechanically.

Colin

[lnvisiblemanParticipant @lnvisibleman]

Posted by Colin Bishop, Website Editor on 06/02/2013 10:40:13:

You would rarely need more than 30 degrees on a conventional rudder, any more and it just creates drag.

If you do need more rotation have a look at ACTion Electronics' Servomorph which extends the throw of servos: **LINK**

Colin

This looks like a better solution than cogs and levers, even for a Luddite like me.

[Malcolm FraryParticipant @malcolmfrary95515]

If its just length of throw rather than angle covered, a longer servo arm will give the length. The only thing to watch out for then is to avoid the chance of toggling over and latching up which can happen when the end being worked on geys to the end of its "pull", and gets latched over.

A spung quadrant (or part of pulley), spring return and flexible cable is probably a better answer. Have a look at a car throttle cabe for inspiration.

[lnvisiblemanParticipant @lnvisibleman]

THANKS EVERYONE !

i think I have all I need to know on this one. If I have any further problem, i'll just ask.

[Tony Bell 2Participant @tonybell2]

The cause of the problem is your new receiver outputs a smaller signal width than your existing Rx. You will find no data on this. Using a servo stretcher is the only solution. It's quicker than trying to alter any rudder linkage.

For a full explination read my "Before Buying" **LINK**

Tony

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