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Old Jun 18, 2014, 05:56 PM
Which shall it be, Passworthy?
Near Dallas, TX
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H9 60 size AT-6/SNJ

I just acquired a Hangar 9 60 size SNJ. It seems to have several (hopefully minor) problems. One of these is that the retracts are wobbly. The previous owner removed the retract servo and fixed the gear with a couple pieces of wood. I would like to re-enable the retracts. As this model is no longer being made, it appears that I may not be able to find H9 replacement parts. What alternatives do I have, that don't require modification?

Also noticed that the engine (early OS FS-91) doesn't appear to have been installed with any offset.

Thanks for any suggestions.

Dave
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Old Jun 19, 2014, 05:12 AM
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Kansas City
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Top Flite has a similar size plane whose retracts may fit. Robart sells air retracts for the Top Flite version that may fit as well. In any event, you'll have to customize the install.
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Old Jun 19, 2014, 09:33 AM
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I have the Tf version of the plane and IMO the stock mechanical retracts for it are not really any better than the ones that came with the H9 version. Never had that one, but from what I have read they take a bit to get setup right so they lock in both positions. Then they will be fine for a while until they start gettin slop. I'm not a big fan of air retracts so I'm going to replace mine with some E-Flite 60-120 90 degree electrics. The stock struts will fit the retracts so the only mod will be to make room for the retracts motor. Most of that is getting rid of the tube for the mechanical retract and trimming the wheel well.

On the firewall angle, it's really hard to tell without putting an angle finder on the firewall on some of these ARF's. My 60 size TF Corsair looked like it had up built in the firewall. After really checking what you find is the shape of the fuse at the front has a bit of an angle from the cockpit to the firewall. Unless it is stated in the manual I think a lot of these older 60 size ARF's were built with 0 up and 0 left/right. For my own comfort factor I slid a washer behind the top motor mounts in my Corsair and left the side/side at 0 and it flew like it was on rails.
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Old Jun 19, 2014, 10:25 AM
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I had two of the H-9 AT-6's with the blue fuselage/yellow wings. I used the factory retracts in the first one and they were wobbly but they held up well and always worked. I sold the plane and they are still going strong. the second I installed robarts and if I remember correctly they fit right in with minimum mods and they are also still working fine. I sold that plane also. Both flew great with Saito 82's.
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Old Jun 19, 2014, 07:30 PM
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Canada, ON, Windsor
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I just picked up the ARF version of the T/F AT-6 last weekend. I already have the gold kit built and am likely going an identical route with custom trunnions and legs for the Eflite 60-120's I have in that one.

That being the case the NIB stock units are pretty much spares. If you are interested give me a PM. Replacement cost through Tower Hobbies for the retracts and legs comes up to approx $35. Can work something out or perhaps a trade.

Also have spare retract servos. One was modded with a standard board and pot to enable speed control, (to simulate full scale and to allow for end point adjustments through the Tx) or possible flap operation with those same characteristics.

ps. Regardless of which model retract, add hardwood blocks or lite ply sub ribs below the mounting flanges to support the retract body sides. This removes stress on the mount flanges if you have a rough landing.

Here are a few pics of the complete frameworks I fabbed for the kit-built. Tore the mounts out of the second set of retracts and the solution were these. When bonded to the wing and spar the entire structure is virtually indestructible.
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Old Jun 29, 2014, 10:14 PM
Which shall it be, Passworthy?
Near Dallas, TX
Joined Jun 2007
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Update. We had windy conditions this weekend (too windy for me to fly, anyway) so I spent several hours both Saturday and Sunday at my table freeing up the glued together stock retracts. Previous owner must have used an ounce of CA in one of 'em! Happy to report that both units are functioning again, and they aren't wobbly -- they lock up and down pretty well. I now suspect the reported problem was due to bad servo adjustment. I ordered a Hitec HS-77BB low profile servo (with 180 degree option) from ServoCity to use as the retract servo, so I can slow down actuation in the radio.

LG wires are also bent out of shape a bit -- amazing to me I've managed to get 'em pretty much back into shape. I think they'll still need to be twisted to get the alignment right.

Next issues will be troubleshooting binding in the tail feather control rods.

Plane came with Futaba 3003s on all surfaces. No idea of the age. Should I replace 'em?
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Old Jun 29, 2014, 11:04 PM
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Although their speed is a bit on the slow side compared to newer servos, they put out 57 oz/in at 6V, so if they aren't acting up, really don't see a problem for this type of scale app.

Mind you, the servos could have a lot of time on them. Personally, if faced with the same situation I would open them up to check gear condition and renew the lube. At that time may decide to place them in a non-critical use, such as throttle, scale sliding canopy, etc.
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Old Jun 30, 2014, 10:18 PM
Which shall it be, Passworthy?
Near Dallas, TX
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Thanks for the comments, Cougar. I just re-read your previous post. D'Oh! I should've talked to you about the servo. Sorry!

Dave
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Old Jul 01, 2014, 06:47 AM
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One thing I forgot to mention and can't find it in the specs is if this servo has bearings. Most likely does not, but I believe they are available in conversion kits.

My own thinking is, unless I have them sitting in spares will not invest any more in upgrading that style servo, (ever hear the term "Polishing a $@$%"?).

That in itself suggests one more issue that can have the potential to cause all sorts of problems, including the loss of the aircraft and increased risk for injury. Closely check the connector for each of those old servo for signs of corrosion or pitting.

On ANY, and I mean ALL old aircraft where the flight battery has been connected for a long time, such as in storage, there can occur a devious little problem called "Black Wire Disease". Unseen the negative conductor can corrode and turn black. and unless you have total power loss you may have to actively go look for it.

You should have some indication at the plugs or connectors and there will be evidence of that corrosion or if severe enough, the pin or socket will be totally eaten away. The same corrosion occurs within the insulation of each wire and also inside the switch. etc. The only cure is total power system replacement, (switches, leads, etc.) and unless you are skilled enough to replace the servo plugs and leads, then they are pretty much toast.

Here's where the devious part comes into play. You may have normal system response when testing on the ground. The servos will really not be under load and can perform with very little current draw. In that case the power system will be able to deliver enough to feed demand.

In flight, or if any load calls for increased power demand, then the conductors, switches and plugs that have suffered the problems described will now come out to bite. As current demand increases the system will simply be unable to feed the need through the compromised components and as a consequence the voltage starts to fall off. The further down the system the worse the problem will be, so servos out on long extensions or with multiple plugs will start to act up first.

If the demand is high enough that voltage drop can be severe enough to cause system shut down or reset. Either means you will no longer have control.

This same effect can occur in electric apps where the Battery Eliminator Circuit simply cannot supply the demands in flight. Same voltage drop and possible system effects.

Lastly, the ON/OFF switches supplied with radio systems aren't really rated for high demand conditions, having a max current rating of 3-4A, (mostly due to the connector limitations). With a standard, 4 analog servo setup should not be a problem, but start loading it with more servos and/or digitals, then the shortcomings will be apparent.

Here's an example of what I used as a solution. In the pic you will see the power control setup I have in Rare Bear. The flight system is fed by a 2S LiFE pack through a 20A regulator. This will cover all the servo demands, including the servoless retracts. The second switch on the left is tied to the 4-cell NiMH battery that is covering just the receiver and has the bar graph indicator. The two are separate, hence the receiver can be much smaller than you would expect.

Part of it are the switches, each with paralleled contacts for redundancy. These are from my dwindling stock of aircraft grade toggles that are less vulnerable to vibrations and are also rated for DC. If you look at the most commonly available switches that rating will be in AC and the actual DC capability will be a small fraction. What that means is if you see a 10A AC current rating, then the DC capability can be even less than 1-2A.

Hope that helps. Now go have a look at some of the connectors.........
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Old Jul 01, 2014, 10:35 PM
Which shall it be, Passworthy?
Near Dallas, TX
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Good write-up, Coug! I started setting the tail servos up tonight, will inspect them before attempting to use.

According to servodatabase.com, the 3003 has bushings. Pretty small gauge leads, too.

Dave
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Old Jul 02, 2014, 07:21 AM
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Canada, ON, Windsor
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If you look at their own specs, Futaba states the following:

Quote:
This servo can produce high-current draw from your batteries.
If using NiMH or LiPo batteries, make sure they are capable
of delivering sufficient amps.
HA! Must have been written before digitals were popular.

With bushings the friction on the output shaft will increase with the load. It was also one of the prime locations for drying out or lube contamination which made it worse. With such a commonly available servo bearing conversion kits became available to at least help reduce drag.

Can you post pics of this project as you go along?
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Old Jul 02, 2014, 05:44 PM
Which shall it be, Passworthy?
Near Dallas, TX
Joined Jun 2007
2,486 Posts
Quote:
Originally Posted by Cougar429 View Post

Can you post pics of this project as you go along?
Post pics? Moi?

Not at all sure there'd be much interest, except perhaps as comic relief! I'll take a few snaps just to illustrate the condition, but don't expect a play-by-play.

Dave
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Old Jul 07, 2014, 06:32 PM
Which shall it be, Passworthy?
Near Dallas, TX
Joined Jun 2007
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I changed the thread title and category. Hope that doesn't lose anyone whose been reading. Sorry I haven't posted photos, but I will. Have been a bit under the weather yesterday and today.

Most recently I have been re-doing the throttle linkage and I also took out the fuel tank to replace the lines as soon as I get some more. Ran thin CA along all the joints inside the fuse, too. Seems like I find more things to adjust or fix while I'm adjusting/fixing previously discovered problems.

Dave
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Old Jul 07, 2014, 08:13 PM
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Hope this adds to your options. I have been using the same style throttle linkage for almost the entire 30 years and it has proven one of the easiest to work with.

First, nylon tubing identical in O.D. to your current brass tubing. Buy a bit of it as it has lots of uses, (such as tubing into the fuel tank). From what I remember it's the same as you would get for aquariums. I get mine at our industrial supply house.

Next would be a stop at the local hardware store for a browse through their cable rack. You will find one of the really fine aircraft cables, (uncoated) fits perfectly within that tubing. The benefit is the routing can be relatively complex to clear obstructions and the action will remain smooth and slop free. That cable can be soldered into a threaded control end, simply fit through a servo quick-link and even CA'd into a nylon control connector.

Only advice is to use a nylon style connector at the motor end to break the electrical bond.
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Old Jul 18, 2014, 07:03 PM
Which shall it be, Passworthy?
Near Dallas, TX
Joined Jun 2007
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Still no pictures, I know. Sorry.

Fuel tank plumbed and back in. Didn't use your suggestions, Coug, maybe next time.

Remaining work: finish retract installation. Check aileron servo setup. Install tail wheel. Install power switch. Install receiver and battery (2 cell A123; not permanently installed). Reinstall cowl.

Spent considerable time wrestling with misshapen main gear legs. They are close to correct, and close to being mirror images. That's about all I can do. Latest frustration is that the main gear recess covers (thin gray plastic) interfere with the linkage rods I bought to connect the retracts to the servo. I don't know what the originals looked like, they had been removed before I got the plane. Pictures in the manual only show the ends visible from the servo opening in the wing. OK to bend the wires?

Dave
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