Restricted servo movement

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5 February 2013 at 18:39 #5208
lnvisibleman
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@lnvisibleman
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5 February 2013 at 18:39 #39054
lnvisibleman
Participant
@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
5 February 2013 at 18:56 #39055
The Long Build
Participant
@thelongbuild
What is the TX set, as some set can be set to reduce the turn.
5 February 2013 at 19:03 #39056
lnvisibleman
Participant
@lnvisibleman
It'a flysky unfortunately !!
5 February 2013 at 19:18 #39057
Colin Bishop
Moderator
@colinbishop34627
Do the instructions with the TX mention how to change servo 'throw'?

Colin
5 February 2013 at 19:29 #39058
lnvisibleman
Participant
@lnvisibleman
They probably do but I don't have them.

I'd guess they were in Chinese anyway so I doubt it would help .
5 February 2013 at 19:41 #39059
Mike Pendlebury
Participant
@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
5 February 2013 at 20:26 #39060
lnvisibleman
Participant
@lnvisibleman
Thanks Mike, done that.

What exactly am I looking for in the manual?

I really am very new to this mularky !
5 February 2013 at 22:46 #39061
Mike Pendlebury
Participant
@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
5 February 2013 at 22:56 #39062
lnvisibleman
Participant
@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 (?????)
6 February 2013 at 06:29 #39068
Paul T
Participant
@pault84577
What is the type and serial of the servos and did they come with the purchase?

Paul
6 February 2013 at 07:26 #39069
lnvisibleman
Participant
@lnvisibleman
Hi Paul. The servos are HOBBYKING type HK15138 and were purchased newfrom a different source to the TX & RX
6 February 2013 at 07:50 #39070
Paul T
Participant
@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
6 February 2013 at 08:45 #39072
Paul T
Participant
@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
6 February 2013 at 08:58 #39074
lnvisibleman
Participant
@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.
6 February 2013 at 09:25 #39078
Malcolm Frary
Participant
@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.
6 February 2013 at 10:40 #39080
Colin Bishop
Moderator
@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
7 February 2013 at 14:32 #39086
lnvisibleman
Participant
@lnvisibleman
The truth is, I was looking for more movement to operate the reversing and speed control on a steam engine,
7 February 2013 at 14:33 #39087
lnvisibleman
Participant
@lnvisibleman
To obtain full speed in both forward and reverse, I will need at least 60 degrees movement from centre
7 February 2013 at 14:37 #39089
Paul T
Participant
@pault84577
You can use gears or mechanical multipliers to increase the range of a servo.
7 February 2013 at 15:26 #39093
Colin Bishop
Moderator
@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
7 February 2013 at 16:54 #39101
lnvisibleman
Participant
@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.
8 February 2013 at 08:55 #39114
Malcolm Frary
Participant
@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.
11 February 2013 at 19:27 #39150
lnvisibleman
Participant
@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.
1 April 2013 at 17:52 #40044
Tony Bell 2
Participant
@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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