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Skyleader slider servos, max voltage, ok to use or what replacement?

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martin collins 109/07/2020 13:58:29
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I have replaced all the old Skyleader servos in my Hawker Hart conversion except the aileron one which is under a small hatch in the top wing, as you can see from the pictures it is of the old slider type. It is going to be used in a 6s electric conversion, will the servo take the voltage or better still is there a suitable slider type replacement? I am using Spektrum 2.4 radio gear.img_20200709_134830_resized_20200709_014925488.jpg

Edited By martin collins 1 on 09/07/2020 13:59:11

Dickw09/07/2020 14:22:41
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The radio and servos won't be running at the 6s voltage. They will either be using 5v from a BEC in the ESC, or you could fit a separate power supply for the radio - e.g. a 4.8v battery.

Dick

martin collins 109/07/2020 14:33:45
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I realise the voltage is controlled by the ESC, the rx has to run with 6v on the Spektrum 2.4, a lot of people got caught out running 4.8v rx packs when not going through the ESC, say on an i.c model as the voltage dropped too low for it to operate.

Dickw09/07/2020 14:47:32
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Ah, so it is a question of if the servo will take 6v? Sorry, I can't help with that one.

Dick

Steve J09/07/2020 14:47:43
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Posted by martin collins 1 on 09/07/2020 14:33:45:

the rx has to run with 6v on the Spektrum 2.4

No it doesn't.

Martian09/07/2020 14:53:43
2540 forum posts
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Thinking back to my old futaba it used all linear servos(slider) and as far as I can recollect there were no available rechargeable batteries then and we used dry cell batteries i.e AA batts at 1.5v x 4 giving 6volts assuming that was the norm at the time I would say Skyleader were 6volt

martin collins 109/07/2020 15:06:49
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Interesting Martian, i have posed the question to the Servo shop, hopefully they can provide a definite answer or suggest a suitable replacement. I will post their response for anyone else who may come across this question.

Barrie Lever09/07/2020 15:15:02
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Posted by martin collins 1 on 09/07/2020 13:58:29:

I have replaced all the old Skyleader servos in my Hawker Hart conversion except the aileron one which is under a small hatch in the top wing, as you can see from the pictures it is of the old slider type. It is going to be used in a 6s electric conversion, will the servo take the voltage or better still is there a suitable slider type replacement? I am using Spektrum 2.4 radio gear.img_20200709_134830_resized_20200709_014925488.jpg

Edited By martin collins 1 on 09/07/2020 13:59:11

100% only run that servo on 4.8v from a Ni-cad or Ni-mh or suitable dropper, that servo was a hand granade in it's day, it will not be any better now.

There was an answer that suggested that 6v would be OK as that is what 4 x 1.5v drycells put out, what that does not take into condsideration is the very high internal resistance of the dry cells, just imagine it like a current limiting resistor in the system.

So with the dry cells as soon as a load is applied there is a significant voltage drop in the system, quite possibly to a lower system voltage than a decent rechargeable 4.8v battery would supply.

You can purchase individual in line voltage droppers to enable you to run one unusual servo (lower voltage) in a model, Multiplex certainly make such a dropper, it just looks like an extension lead.

B.

Richard Clark 210/07/2020 08:47:55
418 forum posts

Personally I would replace it with a modern 'rotary' servo. Nobody seems to make linear ones anymore.

Use an output disc rather than an 'arm' and drill a hole for the kwiklinks a short distance either side of the existing holes. Preferably 'out of line' with the existing holes to keep the distance short and so they don't break through to the original hole.

You will have to deepen the holes in the ribs a bit to turn them into 'slots' to allow for the slight up and down movement.

gangster10/07/2020 13:54:56
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1035 forum posts
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They are lovely servos. The rotary output planes were rubbish so I always used mine in

linear mode. As for voltage I would not risk 6 volts, why would you? There is still an old wife’s tail out there that seems to suggest that all Spektrum receivers must be run on 6 volts. Surely this dates back over a decade to one or two DSM2 receivers that took a few seconds to recover from a volt drop caused by overload or poor installation. I have used Spektrum for 7 years and every receiver I have tested does not exhibit this. If you must use 6 volts and would like to use your src1 servos why not get a 5 volt bec or regulator and isolate the red leads from the rx. Ie piggle the red lead out of the plug and common them. As for the dry battery argument I don’t believe Skyleader ever offered a dry batter option in that era. In addition 6 volts from a dry battery will be fine with a Futaba 128 servo but 6 volts from nicad will fry one. This bears out a previous comment

Richard Clark 210/07/2020 14:10:32
418 forum posts

Yeah. The rotary ones used those awful tapered splines for the output disc. If you didn't do it up real tight the disc could slip and if you did you could strip the thread in the output shaft.

2.4g Shaun10/07/2020 14:42:21
29 forum posts
1 photos

Hi Martin,

Chuck it away; it's 40 years old and you are obviously spending a reasonable amount money upgrading this to a 6s set up. 40 year old electrolytic capacitors don't age well and fail, plastics embrittle and can fail with worrying regularity. I have often seen this in our museum collection of retro radios that we endeavour to keep going when we give our talks to clubs.

Also as mentioned, 4.8v (4 cell nicad)  was the design voltage for this servo 6v will kill it in short order and you don't need 6v for Spektrum gear; old wives and tales comes to mind. I was lucky enough to have one of the first DX7's in the UK and have struck with the brand since. I've had thousands of flights on a 4 cell NiMH pack with out any problems using suitable capacity cells that were capable of delivering the required current under load without pulling the pack voltage down.

I would replace your servo with around one 13g sized servo on each aileron. It will mean making a small new hatch at each side but you should be able to pull the servo extension leads through the ribs with the piano wire pushrod. To make it easier, carefully remove the plug( Rx end) and tape the wires to the pushrod and pull from the hatch end then replace the plug.

This will be a far superior and safer solution. Looking forward to some flying shots, great aircraft.

Cheers,

Shaun

 

Edited By 2.4g Shaun on 10/07/2020 14:46:44

martin collins 110/07/2020 15:03:40
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429 forum posts
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Thanks Shaun, came to the same conclusion in the end, just hope the hole through the ribs is large enough for servo wire. Replacing the fuselage control snakes as well as the inner on the plastic snakes is of the crimp type but they have not been crimped, only very old epoxy holding them in and the inner snake is also very brittle...........

Richard Clark 210/07/2020 15:27:53
418 forum posts
Posted by martin collins 1 on 10/07/2020 15:03:40:

Thanks Shaun, came to the same conclusion in the end, just hope the hole through the ribs is large enough for servo wire. Replacing the fuselage control snakes as well as the inner on the plastic snakes is of the crimp type but they have not been crimped, only very old epoxy holding them in and the inner snake is also very brittle...........

I dunno how experienced you are so you may not need this advice. You can remove the servo plug from the lead (so you can get a new lead through the wing) by VERY gently pulling up the little plastic tag on the plug with a pin one at a time and pulling its wire back a little way. When you have done all three you can pull the whole lead off. Later you can 'pop' them back in.

martin collins 110/07/2020 16:20:07
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429 forum posts
199 photos

Will need extension wires run through the wing anyway as it is a large model so i will put new plugs on the ends.

2.4g Shaun10/07/2020 17:26:01
29 forum posts
1 photos

Hi Richard,

I got distracted whilst posting and meant to add how to remove the Rx plug ends.

Good advice for new modellers, well spotted, thanks.

I've been at it 53 years now (aeromodelling that is), 18 years more than my marriage. 😆😆

 

Martin..

If the holes in the ribs are not wide enough you can use this trick. Get some brass or steel tube from B&Q about 1/4" dia X 1 mtr, sharpen one end then file teeth into it. You can then go in through the wingtip and carefully drill through the ribs buy twisting it by hand if you are retaining the covering. It's worked for me in the  past. Plug the hole in the tip, spot of paint and the jobs done.

Re the  the wing servos, buy decent ones. Not sure of the span and AUW so you may need to go larger but I would use metal gear analogue and ball raced will last longer . Some of the cheap Chinese 9 - 15g servos have a surprisingly large current draw. I usually buy my servos from 4-Max, Inwood or Al's Hobbies (other shops are available 😆.

 

Shaun.

 

 

Edited By 2.4g Shaun on 10/07/2020 17:41:50

martin collins 110/07/2020 17:38:39
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429 forum posts
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Good tip Shaun, will try that if i need the holes widening, the paint is way past pristine anyway, it has a nice patina to it. If it flies really nicely i will treat it to a change of scheme over the winter............

2.4g Shaun10/07/2020 17:47:18
29 forum posts
1 photos

I've just finished the airframe for a Hawker Tomtit. Built from a pristine vintage Veron kit ( take note kit collectors, this is what the designer intended).

The Hart is another one on my someday build list.

 

Another tip for the wires. You can hold the to the servo extension wire to the piano wire with heatshrink tubing  if the holes are on the tight side. Tape can unwind and get stuck sometimes

Edited By 2.4g Shaun on 10/07/2020 17:52:30

kc10/07/2020 18:11:01
6576 forum posts
173 photos

Nobody mentioned the oldest trick of all - before you pull out the old wire tie a string onto it so you can pull the new lead back in........too easy to forget this trick until a minute after it's too late!

2.4g Shaun10/07/2020 18:17:13
29 forum posts
1 photos

Good one but Martin's wing doesn't have any servo extensions in atm just a piano wire pushrod.

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