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Servo Reversing

Why Do You Sometimes Need To Reverse Servos

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Greg Watkiss28/04/2013 13:14:26
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28 forum posts

I am a complete beginner and have seen in the instruction books that come with RC aircraft instructions on how to reverse the servos on the aircraft but it does not go on to explain why this is done. Could anyone let me know about reversing servos.

Regards, Greg

Jim Carss28/04/2013 13:29:26
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2078 forum posts
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Greg

Once upon a time along time ago when servo reversing was not available on the transmitter,If i remember correctly,Futaba servos came with a Red sticker and a black sticker,red ones went clockwise and black one went anti clockwise.

In the early days you had to choose the direction that suited your installation,for example if the elevator had the control horn on the top surface the servo would have to pull ,if the horn was on the bottom of the surface the servo would have to push to operate the elevator

With todays equipment you just install the servos as you want and if the direction is wrong you just reverse direction with the transmitter prog.

Hopefully someone may come along with a better explanation

hope this helps

Jim

Greg Watkiss28/04/2013 13:34:50
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28 forum posts

Hello Jim,

Thank you for the information. I'm now a happy Bunny having learnt something more about RC flying.

Thanks again.

Regards, Greg

Toni Reynaud28/04/2013 13:35:04
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420 forum posts
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Hi Greg,

Servos travel in a particular direction with respect to the direction of movement of the stick on the transmitter. For example, we need the elevator to go up when we pull the stick towards us, or the throttle to open when the throttle stick is pushed away from us. In an ideal world, when building a plane and fitting the servos, we would bear this in mind - we'd check the servo direction then position and fit the servo and control runs such that stick movement gave the correct sense of control surface movement. However, we generally build the plane, fit the servos and control runs in the most mechanically and weight sensitive fashion, then wiggle the sticks and see which way the contol surfaces move. If stick movement gives control surace movement opposite to that desired, we reverse the direction of travel of the servo at the transmitter.

Greg Watkiss28/04/2013 13:43:21
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28 forum posts

Hello Toni,

Thank you for the information. It all makes sense when when someone explains!!

Regards, Greg

crispin church28/04/2013 14:22:39
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442 forum posts
102 photos

also if you need to have 2 servos on a y lead and one is going wrong way you can open the servo and swop 2 wires around and it changes direction (not sure if you can do it on digi ones tho)

NigelH28/04/2013 14:39:05
891 forum posts
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Posted by crispin church on 28/04/2013 14:22:39:

also if you need to have 2 servos on a y lead and one is going wrong way you can open the servo and swop 2 wires around and it changes direction (not sure if you can do it on digi ones tho)

Sorry but that's not true. You need to swap the two motor wires and also swap the two outer connections to the pot.

Bucksboy28/04/2013 16:12:12
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567 forum posts
109 photos

The easier way is to by a Y lead with a reverser built into one of the two leads. This then automatically does the job for the simpletons like me who would be unsure about opening up a servo.

NigelH28/04/2013 16:30:01
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Posted by Bucksboy on 28/04/2013 16:12:12:

The easier way is to by a Y lead with a reverser built into one of the two leads. This then automatically does the job for the simpletons like me who would be unsure about opening up a servo.

Yes, that's also an option, if you don't have a Spektrum radio.

Martin Harris28/04/2013 17:58:03
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9171 forum posts
242 photos

They work just the same for digital servos - all they do is invert the pulse width (normally 1 to 2 milliseconds) of the control signal i.e. 1ms becomes 2 ms, 1.25ms becomes 1.75ms etc.

However, if you do what a friend did last week when using one on a pair of flaps and plug the servos in to the wrong channels, they can both try rather hard to close the flaps - from the closed position - after which we could smell £50 worth of smoke for a short while...

Nigel - often on a relatively complex model, you can get the situation where you don't have enough receiver channels to accomodate a mix - hence the need to use a reversing Y lead...or a much more expensive receiver. Most computer radios can accomodate a suitable mix - Spektrum are certainly not unique in this feature!

Edited By Martin Harris on 28/04/2013 18:05:18

Peter Miller28/04/2013 18:49:43
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I suspect that you are not nearly ready to worry about all those y leads and reversing leads and flap.

Going back to the old days, as they say, you had to set up the direction of the throw and also the travel by using the different holes on horns and output arms on the servos. It all took a long time and patience.

BUT You only had one transmitter and no memories so all your models were set up and you could fly any one on the same tx with no worries about flying on the wrong memory.

NigelH28/04/2013 19:11:57
891 forum posts
1 photos
Posted by Martin Harris on 28/04/2013 17:58:03:

Nigel - often on a relatively complex model, you can get the situation where you don't have enough receiver channels to accomodate a mix - hence the need to use a reversing Y lead...or a much more expensive receiver. Most computer radios can accomodate a suitable mix - Spektrum are certainly not unique in this feature!

Edited By Martin Harris on 28/04/2013 18:05:18

I think that you misunderstood my point. There's a warning on Spektrum RC which specifically says that reversing Y-leads should not be used.

Peter Miller28/04/2013 19:27:02
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10756 forum posts
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10 articles

I think that you misunderstood my point. There's a warning on Spektrum RC which specifically says that reversing Y-leads should not be used.

Interesting. I missed that and have used a servo reverserin a Y lead without any problem

However a large model (not mine) with a petrol engine was fitted with one and this picked up interferrence from the ignition system which caused wild flapping of the controls at low rpm.

Strangely enough when I mentioned this to Horizon before writing it up elsewhere The chap at Horizon did not mention this warning.

John Olsen 129/04/2013 03:54:05
446 forum posts
23 photos

With some of the digital servos you can connect them to you PC via a suitable interface and then reverse them from the PC. They remember the state you have set them in. You can also change the travel, centering, speed, and deadband, and of course it makes a handy servo tester, since while it is conected up you can test movement in either direction. The setup I have is for Hyperion, I think there are others with equivalent features. This is one reason why digital servos may be preferable for some applications...you can tailor the servo behaviour to match what is needed.

John

A.T.29/04/2013 05:29:18
83 forum posts

There are many and varied reasons for servo reversing, as noted above, the first Tx had nothing other than 1,2,3 or 4 ch. Hitec, JR and most other Tx servo operated in a clockwise direction whereas Futana operate counterclockwise - easy solution was to use one Hitec & one Futaba or else open servo and exchange 4 points = Red & Black power in and the outer two on the pot - then realign pot to new center position before locking down. Now we have the luxury of servo reversing on the Tx but best oevra; are the programmable digital servo which then suffer no losses. Otherwise good reeading under sub section:

"Servo - Modify for Retracts, Swing, Number of Turns, Ganging, Reverse & Continuous Rotation"

. Modify to 180 & 360 degree operation.. Gang and Fit servos to yachts & boats - email Alan for .pdf

. Sailwinch servo - adjusting the number of rotations for Hitec HS785HB - email Alan for full ,pdf

. Sailwinch servo - adjust number of turns from your TX *- - email Alan for full ,pdf in need

. Servo - How to modify (S148) for 360 degree rotation - winch

. Servo - Drive Sprockets and Chains in lieu of horns.

. Servo - DIY Fit Flat Aluminium Horns

. Servo - DIY Linear Action

. Servo - DIY Reverse Rotation

. Servo - DIY Reverser, Driver, Direct Controller and other mods.

. Servo - Reverse operation . DIY pictorial

. Servo - Reverser for Y-cord operation - If site down, email Alan for copyy

. Servo - Modify HS-322HD for continuous rotation

. Servo - Modify HS-311 for continuous rotation .

. Servo - Modify for 360 degree rotation.

. Servo - Modify Digital for infinite rotation, 360 degree rotation

. Servo - Modify HS-81 & HS-85 for 180 degree rotation

. Servo - Modify HS-55 & HS-85MG for Continuous rotation.

. Servo - Modify non digital for 180 dregree rotation

. Servo - Retract Conversion (S-148)

and more under Alan's Hobby, Model & RC FAQ Web Links (quick search = Ctrl+F)

Alan T.

crispin church29/04/2013 08:07:03
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442 forum posts
102 photos

A T many thanks for all those links

i woundered when i got a second hand plane why all futaba and one hitec

 its ok saying just buy a y lead with it built in   not everyone got loads of money 

 

Edited By crispin church on 29/04/2013 08:09:59

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