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TF P-51 60 ARF Retract Servo Horn Broke While Test Taxing

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TF P-51 60 ARF Retract Servo Horn Broke While Test Taxing

Old 09-01-2016, 07:29 AM
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Default TF P-51 60 ARF Retract Servo Horn Broke While Test Taxing

My Dad and I have been working on this ARF: http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXTDF5

It uses a mechanical retract servo. The servo they call for in the manual has been discontinued. For that reason I had to buy the Hitec http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXN568 We tried to set up exactly like the manual shows us, and the retracts operated fine up and down. However today when I was taxing the plane around for the first time one of the retracts collapsed on me. After taking the wing off we noticed that the servo horn was completely broken in two. I never got to see the actual set of servo horns that came with the servo. But the one my Dad used is Hitec and fit fine. This leaves me with some questions. Why did a never used servo horn break? And second is the one's that are sent with the retract servo stronger? Because when I compare my Hitec servo horns nothing looks different. They all seem to be made out of the same material.

I currently only own two different Hitec servos. HS-325HB and the HS-75BB retract servo. Are the servo horns the same?
Old 09-01-2016, 09:02 AM
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Greg,
Assuming you weren't putting undue stress on the horn,, that is you had it set up with no binding,, it could just be that horn was old and brittle.

The Horns for the 325 should fit the 75 just fine,, If you need a couple HD servo horns, LMK, I'll mail you a couple
Old 09-02-2016, 06:20 AM
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Originally Posted by scale only 4 me
Greg,
Assuming you weren't putting undue stress on the horn,, that is you had it set up with no binding,, it could just be that horn was old and brittle.

The Horns for the 325 should fit the 75 just fine,, If you need a couple HD servo horns, LMK, I'll mail you a couple
Thank you for the offer.

Currently we would like to know how the retract locking works. The retracts that come with the plane are these: http://www3.towerhobbies.com/cgi-bin...&I=LXUY33&P=BB My Dad has a theory that the retracts weren't locking right and that is why there was too much pressure put on the servo horn. But we don't how to check if the retracts are locking properly. These are the first mechanical set we have ever owned.
Old 09-02-2016, 02:36 PM
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Most work the same way,, there's a cam lock of some sort.

The trick with mechanicals is having the servo horn length just right so when it makes the 180 degree travel there is no binding on either end,, but it does have enough travel each way to go to lock up to lock down,, it does take a bit of tinkering to get it just right.

good luck
Old 09-02-2016, 05:40 PM
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Or make it easy on yourself and put a set of Eflite retracts in instead. They work very well. I have a set of the mechanicals sitting on a shelf.
Old 09-03-2016, 11:57 AM
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Originally Posted by scale only 4 me
Most work the same way,, there's a cam lock of some sort.

The trick with mechanicals is having the servo horn length just right so when it makes the 180 degree travel there is no binding on either end,, but it does have enough travel each way to go to lock up to lock down,, it does take a bit of tinkering to get it just right.

good luck
Thank you for your input. I sent Bax a question about how these locks work.

Originally Posted by acdii
Or make it easy on yourself and put a set of Eflite retracts in instead. They work very well. I have a set of the mechanicals sitting on a shelf.
Several people have suggested Eflite to me for my other plane. Maybe someday I'll buy some.
Old 09-03-2016, 06:16 PM
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The secret is to cheat and use two servos; one for each retract. That way each can be tailored to the exact pushrod length. If your length was off, the servo, not the retract lock, was holding your plane up. The servo is not meant to do that.
Old 09-04-2016, 02:59 AM
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I guess that's an option, and one I used on my Kyosho ta152 since it had a two piece wing,, but a single servo set up right one servo is fine if done right,, after all if the retracts are the same , the pivot points should be the same also.

Here's a youtube vid I founds showing a good set up, notice two things, 1- he's bent the push rods so they don't interfere with each other and 2- you can see he's drilled a few custom holes in the servo horn to get his total throw just right.

https://www.youtube.com/watch?v=GuHB6bDYGNw Like most things in the hobby, once you've learned how to do it,, it's not hard anymore

Good luck
Old 09-04-2016, 06:19 AM
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What I am trying to learn is how to make a decent hatch to hide the switches. The hatch isn't the problem, its the hinging part! Thought I had something going good, but the magnets didn't hold and pop, off it went....somewhere.
Old 09-05-2016, 08:40 AM
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Originally Posted by scale only 4 me
I guess that's an option, and one I used on my Kyosho ta152 since it had a two piece wing,, but a single servo set up right one servo is fine if done right,, after all if the retracts are the same , the pivot points should be the same also.

Here's a youtube vid I founds showing a good set up, notice two things, 1- he's bent the push rods so they don't interfere with each other and 2- you can see he's drilled a few custom holes in the servo horn to get his total throw just right.

https://www.youtube.com/watch?v=GuHB6bDYGNw Like most things in the hobby, once you've learned how to do it,, it's not hard anymore

Good luck
I was reading his comments, He says that the servo strips out easy and so now He's using servoless retracts.

I was taxing around today and I couldn't keep the plane straight on the ground. I think it's because the retracts wobble so much. My Dad tells me I need more practice or if I keep the elevator up longer things would go better. He's never flown a RC plane in his life! I've been flying for 20 years. All my other planes are taildraggers so it isn't like I don't know how to keep a taildragger straight for take off. But this plane seems to have a mind of it's own, and when it starts to turn one way I almost got to give it full rudder to straighten it up. I'm used to just giving a little rudder here and there.

I want to know if this much wobble is normal for mechanical retracts like mine. http://www3.towerhobbies.com/cgi-bin...&I=LXUY33&P=BB It isn't the struts that are wobbling it's the actual retracts. We tried to take the retracts out of the airplane and check them by hand. They seem to be locking all the way, and yet they got a lot of play back and forth.

http://www.youtube.com/watch?v=LHu8P9JxrUI Also the way I have my servo horn set up is the same way T.F. says to do it in the manual. Of course my picture looks a little different because the retracts were in a different position when I took the picture.


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Last edited by gregoryshock; 09-05-2016 at 08:49 AM.
Old 09-06-2016, 04:35 AM
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Well, I'm not surprised the hobbyking servo stripped, I've never had a problem with the HS75,, Yes, those look more wobbly than most, and yes, some of the better mechanicals have an adjustment set screw that helps a little,, problem is I don't think many companies are still making those type.

I've never cared for those spring type struts for "mains",, they move around a lot on takeoff/landing, they're really just for nose gear on a trike, I'm sure that's adding to your tracking problem

I'd still bend those pushrods a touch to keep them from touching,,

good luck
Old 09-06-2016, 05:10 AM
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I agree, those wire struts are horrible. Have to straighten them every time the plane flew. Put on a set of Robarts struts, and, well, except for my last landing, don't need to straighten them. I didn't have a bad landing, just hit something on the strip the wrong way with the left wheel, which bent the strut. Maybe rubbing tires, or a bump, don't know, but if it were the wire stuts, for sure it would have been bent back into the wing and caused damage.
Old 09-06-2016, 05:40 AM
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Originally Posted by scale only 4 me
Well, I'm not surprised the hobbyking servo stripped, I've never had a problem with the HS75,, Yes, those look more wobbly than most, and yes, some of the better mechanicals have an adjustment set screw that helps a little,, problem is I don't think many companies are still making those type.

I've never cared for those spring type struts for "mains",, they move around a lot on takeoff/landing, they're really just for nose gear on a trike, I'm sure that's adding to your tracking problem

I'd still bend those pushrods a touch to keep them from touching,,

good luck

I did some more research and I found this video:

http://www.youtube.com/watch?v=DRjjbEY3Q34 It's 5 years old. I have no idea what name brand those retracts are and He didn't put it in the video description. I don't understand why some youtubers make a how to video and leave out some important detail like that. These https://www.amazon.com/HobbyKing-All...2FP-47D%2FAT-6 look like they could be the same thing. I know some people like hobbyking but I got almost no experience with them. The last time someone suggested I buy a small camera from them and I did. It wasn't any good in more than one way.

Personally I have always flown with spring type struts off of grass. I've never tried anything different. Robarts are expensive. But in this case the main issue was the retracts themselves. The play you see in my video was entirely in the retract, because I didn't put enough pressure to flex the struts. But I respect your opinion/experience with struts and retracts.
Old 09-06-2016, 12:35 PM
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I understand,we all have our preferences,,,

I think these still have the adjustment set screw like in that video,, frankly I'm surprised Tower still sells them,,I guess they only sell them as a trike set now, they used to sell just mains in different angles also,, the metal frame one is a design that goes way back,, many different companies made a similar products.

http://www3.towerhobbies.com/cgi-bin...gfcaAoCp8P8HAQ

good luck
Old 09-06-2016, 01:01 PM
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Assuming these are the stock retracts that came with the Top flight ARF, I have mine still, I can look to see what they have and if they can be tightened up.
Old 09-06-2016, 03:53 PM
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Well these things are so simple. The stock strut should be a tight fit in the hole, and one set screw holds it in. That would mean the center section is loose, so take the 5 screws out, separate them and add a thin washer or two to tighten it up. This one has never been used and it too has a slight wiggle to it.


Old 09-07-2016, 10:01 AM
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Concerning servo arm breaking, did you by chance happen to use any loc tite on the fittings that secure the rods to the arms?
Old 09-08-2016, 05:49 AM
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Originally Posted by scale only 4 me
I understand,we all have our preferences,,,

I think these still have the adjustment set screw like in that video,, frankly I'm surprised Tower still sells them,,I guess they only sell them as a trike set now, they used to sell just mains in different angles also,, the metal frame one is a design that goes way back,, many different companies made a similar products.

http://www3.towerhobbies.com/cgi-bin...gfcaAoCp8P8HAQ

good luck
My struts won't fit those. My struts are bigger around.

Originally Posted by acdii
Well these things are so simple. The stock strut should be a tight fit in the hole, and one set screw holds it in. That would mean the center section is loose, so take the 5 screws out, separate them and add a thin washer or two to tighten it up. This one has never been used and it too has a slight wiggle to it.


I wish I could see how much wobble "play" your has. Can you put them together and make a quick video? Because if your's has the same amount mine has then probably all of T.F. has that much....

Originally Posted by speedracerntrixie
Concerning servo arm breaking, did you by chance happen to use any loc tite on the fittings that secure the rods to the arms?
Loc tite wasn't used that day. I wanted to put some on them but my Dad didn't think it was necessary for a test taxi. We did really crank them down as hard as we could. We don't always Loc tite things when we are still in the process of adjusting things. They did not let go the horn was snapped into two pieces, and they were both still tight. I want to have loc tite on them before we fly the model. *If I can ever figure out what to do about the retracts.

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Old 09-08-2016, 06:12 AM
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You don't want to get Loc Tite anywhere near plastic. It will make most plastics brittle.
Old 09-08-2016, 08:56 AM
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There is very little wobble to it, but it does wobble. These have never been used, so there is no wear in them. There is about 3/32" of play at the end of the strut.
Old 09-11-2016, 12:47 PM
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Originally Posted by acdii
There is very little wobble to it, but it does wobble. These have never been used, so there is no wear in them. There is about 3/32" of play at the end of the strut.
Dad was able to get the 3/4 of an Inch wobble to stop.

My work on this P-51D 60 is done for the year. The plane tracked straight but when I took off I didn't think fast enough. The airplane ended up in the ground and now things need to be fixed. It will be a winter project.

It's no surprise I'm out of practice. And I never flew a war bird.
Old 09-11-2016, 04:33 PM
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Warbirds are hard to fly if you never flew one. You have to keep two steps ahead of it or it will go CRUNCH. They also have to be perfectly balanced and trimmed, with proper throws, or they go CRUNCH. Been there, done that, still have nerve issues when I fly the Mustang, though they are getting less noticeable. I have 4 very good flights on mine so far after it went CRUNCH due to improper balance and throws. I think once I get the foam tire inserts in mine, ground handling and landing will be far less eventful. Once I can get a few good uneventful landings where the nose stays above horizontal instead of below it, then flying it will be no different than my other planes. I'm hoping to have a few more decent flying days this year to get my P-51 and P-47 more flight time. Flying season came and went and I hardly used a gallon of fuel. I think I used more at the SIG flyin than I did the rest of the year.
Old 09-13-2016, 07:01 AM
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Originally Posted by acdii
Warbirds are hard to fly if you never flew one. You have to keep two steps ahead of it or it will go CRUNCH. They also have to be perfectly balanced and trimmed, with proper throws, or they go CRUNCH. Been there, done that, still have nerve issues when I fly the Mustang, though they are getting less noticeable. I have 4 very good flights on mine so far after it went CRUNCH due to improper balance and throws. I think once I get the foam tire inserts in mine, ground handling and landing will be far less eventful. Once I can get a few good uneventful landings where the nose stays above horizontal instead of below it, then flying it will be no different than my other planes. I'm hoping to have a few more decent flying days this year to get my P-51 and P-47 more flight time. Flying season came and went and I hardly used a gallon of fuel. I think I used more at the SIG flyin than I did the rest of the year.
This year I went through two and a half gallons of model fuel just flying the Zlin 526 and the Hog Bipe.
Old 09-13-2016, 10:35 AM
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Been flying a T-Clips for over two years now and still haven't used a gallon of gas in it. Hard to when it flies for an hour on 12 ounces. I just haven't had as much flying time this year as I want to, usually I go through two gallons of Wildcat and half gallon of gas, now with the P-47 I might go through more gas, seems like a good flying plane and if it doesn't have any bad habits, will most likely become my go to. I flew my Somethin Extra the most this year, the more I fly it, the less fuel it uses as the engine breaks in. The P-51 uses the most fuel, and flew it only 4 times this year.

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