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Old Jun 25, 2004, 10:16 AM
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Montreal, Canada
Joined Jun 2004
8 Posts
Help!
Kyosho Piper J-3 Cub, a.k.a. ParkZone J-3 Cub, FIRST FLIGHT

FYI: This is a fairly long message about first flight, and subsequent trouble with my KYOSHO PIPER J-3 CUB. I also posted this message on RC Universe, so I apologise to those of you who have seen it twice!

Not sure if anyone else has noticed this, but I see that the PARKZONE J-3 CUB and KYOSHO J-3 CUB are the same plane, with minor differences. I will attach two comparison images for your viewing pleasure.

Two days ago, I went out and bought a KYOSHO PIPER J-3 CUB M24, for 15.000yen (that's about $139 USD, or $190 CDN). I have never flown an R/C plane before, and had been set on getting the GWS Slow Stick. Since the Slow Stick is considerably more expensive in Japan, and I couldn't locate any dealer that sold replacement parts for it, I decided to get a local brand's plane instead. Enter: the Kyosho J-3 Cub.

The plane needed some very basic setup (attach the wing and landing gear, and charge the battery), so I was able to test it very soon after buying it. I went to a park, put it on the ground (I'm afraid to hand-launch it, not sure why. I will soon.), and revved the motor until it started rolling along. Nine out of 10 times the thing would start rolling, then begin veering to the right (while still on the ground), and then suddenly spin its tail around and stop. Very frustrating. The rudder made no difference at take-off speeds, so I just kept trying until it went straight (any tips on how to stop it from doing this? I have come up with a simple design for a rudder-mounted tail wheel, which might work). Finally, it took off. I immediately started panicking, not sure how I would ever get the thing down without a spectacular crash. As my girlfriend put it, "I felt like I was on the plane." I flew an ungraceful circuit in the sky, never more than about 7-10 meters off the ground, before I started heading down again. I turned off the motor, and tried to land, managing to put the wheels down relatively softly in some long-ish grass. With the motor off, it slowly flipped over foward and on to its back. That ended my first (and so far only) flight.

Upon inspection, I saw no damage. So I tried to take off again. However, this time it the motor was making a funny screeching sound. I didn't think much of it at the time, but it seemed like it was labouring harder than it should have been. It wouldn't take off, so I gave it a closer look. The propeller shaft (it's a geared unit) was very hard to turn by hand. In fact, after a few seconds of turning it, it simply stopped turning. I couldn't turn it by hand at all, it had completely seized. In retrospect, the landing (in my opinion) could not have damaged the transmission. With just a few tools on hand, I took off the cowling, and unscrewed the motor/transmission unit from the fuselage. I could still not turn the shaft, and I feared that the motor had seized. When I removed the gear/shaft assembly I saw that the nylon shaft-bearing had melted and fused to the nylon gear (I'm assuming these are nylon parts). There was plenty of grease on everything, and I couldn't tell how it happened. With a pair of wire-cutters, I "split" the gear from the bearing, and realised I wouldn't be flying any more that day.

Last night I sent a message to Kyosho's support department, and promptly received an answer this morning: send the whole thing back, and you'll get a new one. No shipping charges, either. (Really, I only need the gear-reduction unit, but they said it was easier to swap the whole thing.) I asked if I could keep the Tx, as I took it apart and changed it from a MODE-1 to a MODE-3. I also asked to keep the 8.4V 600mAh battery as a spare, and they said "Sure."

So now I am waiting for my replacement Kyosho Piper J-3 Cub, and wondering if there will be any differences. I suspect not, though I hope it won't suffer from the same problem the first one did.

Does anyone here have advice, tips, or questions about their Piper J-3 Cub? I assume that everyone else who owns this model has the ParkZone version. The differences seem to be in the motor: Kyosho's has an "M24-class 280" motor. ParkZone's sports a "370" motor. Can anyone tell me what this difference means, if, indeed, there is a difference? As well, the Kyosho comes with a four-channel, two-stick Tx. The ParkZone comes with a three channel, single-stick Tx.

If you've read up to this point, thanks! I hope no one else has had the problem I mentioned. All I want to do is fly it again, and now I have to wait. Well, we all know what it's like to wait when we really, really want something.


Ciao

- Sylvan

LINKS:

For the Kyosho Piper J-3 Cub:
http://www.kyosho.co.jp/rc_model/air...3cubm24-e.html

For the ParkZone J-3 Cub:
http://www.parkzone.com/Products/Det...Number=PKZ1100

FIRST IMAGE: Kyosho Piper J-3 Cub

SECOND IMAGE: ParkZone J-3 Cub

THIRD IMAGE: The gear-reduction unit (photo from ParkZone website). Notice the large, white nylon gear. Behind that gear is the nylon bearing. The gear and bearing fused together.
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Old Jun 25, 2004, 10:57 AM
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Montreal, Canada
Joined Jun 2004
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ParkZone J-3 Cub

ParkZone J-3 Cub
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Old Jun 25, 2004, 10:57 AM
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Montreal, Canada
Joined Jun 2004
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Gear-reduction unit

Gear-reduction unit
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Old Jun 26, 2004, 01:13 AM
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Northern VA
Joined Jun 2004
15 Posts
Help on first flight

Hey Sylvan-
Welcome to the cub club. Congrats on your first plane and noble efforts on
flight. I've been flying the ParkZone version of the Piper J-3, and have
crashed many times. Perhaps I can give you a few pointers....

1. Take off's from the ground will be difficult without a tail wheel, since the
tail skid just acts to impede forward motion. Have you tried holding the tail off the ground, revving the engine and releasing the plane? This should give you a fairly straight launch vector. Torque from the engine can cause a plane to veer right (or left).

2. You should be prepared to buy extra spare parts. The prop shaft is prone to bending on this model, and even a slight tap will cause it to bend. Once bent, you must swap it out. I'm able to carefully bend the shafts back to being fairly straight and have been able to use them on additional flights. The motor and pinion should be fairly durable, and usually won't bend. You will also probably break the gearbox, but unless it is really demolished, can be repaired or glued back together (once again spare parts on hand, are very helpful to have).

3. I prefer hand launching (into the wind, of course), but be careful of the "dead zone." The first 10 feet off the ground. Crashes occur in this zone frequently. Also, don't try to make any sudden turns for the first 10 seconds, or your plane will stall or snap-roll and crash. Let the plane pick up speed and height (20+ feet), then turns and flight is more manageable.

4. As far as the fused gear problem. I find this happens quite a bit. The nylon gears and prop shaft guides can fuse under the heat created by the motor, and friction. I put a small metal washer between the prop shaft gear and the rear prop shaft guide. I use a ceramic grease on all parts, although you can use a high temperature wheel bearing grease (but it's messier). I try to avoid any areas where plastic touches plastic, as these areas will fuse under the heat, load and friction.

5. The Piper from Park Zone has a 370 motor (a designation to indicate the power), so I don't know if your 280 motor is very strong. I suspect that you might have a tougher time getting the plane airborne, so you'd have to be extra careful during take-off's not to stall your plane. The ParkZone Piper weighs in at 15-16 oz, so I hope your model weighs less than that with a 280 motor. Once airborne, you should be able to fly ok.

There's a pretty good flight sim program that can help you get the basics of which way to adjust rudder, elevators, throttle, etc. I can't recall the website, but run a google search for FMS sim (I believe it's at Flight Model Simulator.com) It's a nice program (for free), so I should give some credit to the guys who designed it.

One tip that someone gave me that really helped was when the plane is coming at you, if a wing tips too far (and starts a turn that you don't want) move the rudder stick in the same direction that the wing is tipping to correct the turn. Until the motions become second nature, you will have to actively think about which way to turn the stick to control the plane. After 20-30 flights, it will become second nature (most of the time).

Hope that helps. Remember to buy those spare parts. And, Good luck!

Sincerely,

Spare Parts
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Old Jun 26, 2004, 07:59 AM
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Montreal, Canada
Joined Jun 2004
8 Posts
Re: your pointers

Spare Parts,

Thank you for your kind message. In regards to your pointers:

1. I have already come up with a simple design for a steerable tail wheel (using the rudder, naturally). When I receive my replacement Cub, I'll put the wheel on and see if it makes any difference. I hope it does. Torque from the motor is certainly the main cause of spin-outs, as it is directly related to the level of motor output. Of course the tail-dragging nature of the design also helps to set the tail moving laterally one way or another (usually when it bounces off a pebble or stick or something). I did have better luck by giving full down elevator, to get the tail off the ground as quickly as possible. Then, with a slow progression to up elevator, the plane took off the one and only time I flew it. Finicky little Cub!

2. I've been trying to source spare parts here, but, unfortunately, the few hobby shops that do exist in this town deal primarily in R/C cars. They all have Kyosho banners, though, so I should be able to get them to order a few things for me. Failing that, there is a direct mail-order option (though the prices are higher, and I have to pay shipping). I chose Kyosho because it is a Japanese brand, and being in Japan I figured it would be easy to find replacement parts, though so far I've been out of luck.

3. I do intend on doing hand-launches, though I like the "realism" of taking off from the ground. I should master both in good time. Right.

4. Again, that was the idea that came to mind right away. I didn't know what kind of bearings it had before I took it apart. Had I known, I definitely would have put some metal washers between any contacting nylon parts. What is ceramic grease, by the way? I was going to invest in some standard bearing grease, but it generally comes in volumes that I just don't need for a small model.

5. The 280-class motor is a bit small, though I didn't find the take-off roll too long. Furthermore, it seemed to have plenty of power during the 45 seconds I managed to keep it airborne. Of course, being that it's my first plane I thought it seemed almost over-powered. I thought the same thing when I first started driving my parents' car, but, within a few weeks (as a teenager, especially), that same car seemed painfully under-powered. I'm sure it won't be long before I'm investigating potential motor upgrades. This Kyosho Piper J-3 Cub is almost identical to the ParkZone Cub, so the weight is about the same. I think they say it's 480g, which is about 16oz.

I've been playing with FMS for a few weeks now, but of course I don't have a Tx that I can use with the software. Steering an animated plane with a keyboard doesn't have too much in common with flying the real thing; however your tip on which way to move the rudder stick seems very useful. Certainly it's more simple to think about that tip than it is to imagine being behind the plane and yawing the correct way.

One change I did make to the kit, specifically the Tx, was to swap two potentiometers inside thereby changing it from a Mode-1 to a Mode-3. (The Kyosho Cub comes with a two-stick, four-channel radio) I found that flying it in Mode-1 was counter-intuitive, after years of playing flight-simulators with a joystick (pitch and roll on the same stick). Naturally I made this change AFTER the gear-reduction unit seized, so I was able only to test it out with the plane sitting (in pieces) on my bedroom floor. Interestingly, though there isn't an advertised basic/expert mode-change option like with the ParkZone Cub, this Kyosho Cub's radio does have a series of switches hidden behind a sticker on the front of the unit. While I had it apart, during the potentiometer-swap, I noticed a bank of five switches on the circuit board. With some experimentation, I found that the first four switches are used to reverse the four channels; the fifth switch adds rudder/elevator mixing. As the kit comes, there is no mention of these capabilities, nor is the mixing on by default. Again, when I receive the new Cub, I look forward to trying out the mixing. I suspect, however, that I will probably leave it off. I'd like to think that I can mix things up on my own, so to speak.

It's been just over 24 hours since I sent the Cub back for a replacement. According to mail tracking, the box has arrived at Kyosho HQ in Tokyo. Now I just have to wait for them to go to work on Monday morning, and send me the new one. Sigh.

How have you found the landings to be? I've read other posts of people complaining that the aluminium landing gear, and foam wheels, are too springy. I was thinking I could add some kind of support between the two landing gear struts, as a rudimentary flex-limiter of sorts. Of course, I don't want to transfer the shock of a bad landing directly to the fuselage. Maybe the springiness is a good thing..

Thanks again for your reply. I apologise for writing so much, but this new hobby is all I think about these days! Lame, or what?


- sylvan
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Old Jun 28, 2004, 11:25 PM
Registered User
Northern VA
Joined Jun 2004
15 Posts
Did you get your new plane?

Howdy Sylvan-
Did you get your new plane from the manufacturer? From the sound
of your posting, you seem to like to tinker with stuff. That is
always helpful when working with RC. It sounds like you're on the
right track, just keep practicing.

You can get ceramic grease or other types of grease for gears at
your local hobby shop. Try the RC car section. I have used high
temperature wheel bearing grease and that seems to work ok.

The problem with the landing gear is the bounce. There aren't too many places to fly in my area (outside Washington DC), so I mostly just
hand launch and land in the field.

I lived in Japan for three years (Yokohama), and can only imagine that
the fields must be pretty small. Maybe the local police don't get too angry when you fly a little RC plane. I've been shooed away from some fields, but found one that no one uses either early in the morning or at dusk.

Keep us posted on your progress, and don't fly into any bamboo's.

Spare Parts
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Old Dec 29, 2008, 02:38 AM
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Joined Dec 2008
1 Posts
Just a few questions.

Hello

I'm not sure if this would be the right place to send this, but I got a Kyosho Piper j-3 cub as a christmas present and me and my dad (yes, my dad i'm only 14) went to try it out after those basic setup things. Obviously when i got to control it I crashed and crashed... No major problems really, mostly they have to do with the outer shell cracking. probably the worst cracks are; the small thing where you attach your rubber bands to (for placing the wing) has hit itself through the shell up above, partly because of a crash, and partly because of the tension of the band. The other larger problem is the flap(dont know the proper term) at the back which controls turning. The controller rod that comes from the plane is not anymore connected to the flap because the joint has cracked. I think The temperature (-6 C) has something to do with it.
Should i just wait till summer?

Thank you in advance
Oh it broke
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