phase_boy

FYI: This is a fairly long message about first flight, and subsequent trouble with my KYOSHO PIPER J-3 CUB.

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 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.

mectf

Pretty cool plane.
I have crashed the crap out of mine. Been thru a few gearboxes. I have decided a washer between the gear and the bushing is twtg.
Still plenty of gear engagement. Just make sure the prop shaft has a fair amount of end play. This stops the bushings from being loaded and over heating. Also if the prop shaft is over tight you have a major loss of HP.

One of my last crashes busted up the pegs on the tail mounting. I decided to take a shot at a repair and decide on a few dabs of Crazy Glue. Worked like a charm..

Reddog177

Phase,
I have a ParkZone Cub that I've had real good luck with! If you'd care to read about my experiences, go to http://www.smallflyingarts.com/cgi-b...7945;start=0#0 . It's my first R/C and I've taught myself to fly with it. I've flown it about 30 or 40 times now.
Dick

phase_boy

mectf,

As I wait for my replacement Cub to arrive, I have already gone out and purchased a bunch of small, metal washers. I realised pretty early on that I would need a few of those. As for the tightening of the prop shaft, I don't know what to do about that. I always made sure there was adequate play, but the prop would always tighten itself into a frenzy of melting nylon. No matter how tight the prop nuts were, the propeller still managed to cause a major tightening of the transmission. Then, as you said, there followed a loss of power. A few seconds later, the motor couldn't turn at all.

I bought some extra nuts to add to the shaft (R/C planes sure are a dirty business), in the hopes that I can tighten them against each other to maintain adequate play in the gear-reduction unit. Maybe loctite or something might help? I don't know.

It's nice to hear that yours has survived many crashes. The foam seems a bit flimsy to me, but then there isn't much mass to the plane, so it shouldn't hit the ground with too much energy (not if I can help it, anyway!).

I can't wait to get the new plane so I can continue learning how to fly. At least a couple times per day I pick up the transmitter and "practise" flying. How embarrassing.

- sylvan

mectf

Reddog177,

Great read.. Thanks for passing that along.

phase_boy,

Take a close look at the height of the spacer stack before you put the nut on the shaft. You should have a little shaft showing between the threads and the top of the bushings. The nut tightens up on the shoulder of the shaft. Remove or add washers as necessary, with that space the nut cannot compress the bushings. A little blue Loc-Tite would not hurt a thing but shouldn't really be needed if the 2nd prop nut is tightened enough against the prop. Hold the prop and turn the wrench for final tightening. I really don't see a need for double nutting.

Another bit of advice.. I put a tiny dab of glue on the rubber propeller thing. Just a touch stops it from falling of in a crash. New props come with the rubber thing so removal isn't much of a issue for me..


Keep up the good fight and keep us posted.. Maybe one of these times I will actually have a successful flight...

kwiktsi

Sorry, didn't read the whole post, but as for the bushing problems- have yo looked into going with a bearing instead? If you get an ID and OD measurement of the bushing, I can look into a bearing for you.
Joe

mectf

kwiktsi,


The bushing measures .019"(3.02mm) ID X.196"(4.98mm) OD X .250 with a .056 X .307 shoulder that also has a index ears and a flat on it.. pretty crazy for a bearing...

For the cost of $7.00 for a gear box... just checking the set up is worth it's weight.


I measured the end float on my spare at .010". It's very happy at that.
3 spacers at .112 .112 .114 and 2 washers at .023 .028.
Insert bushings insideby the gear .250 outside by the prop .247 .

My first stock gearbox only had had two spacer but came with 3 washers. Looks like its all differant.. Just gotta check it all out..

Lots of possible manufacturing tolerance issues.. But for me thats part of the fun..

Paolo66

Hello All,
Some weeks ago I purchased a Kyosho Piper J-3 Cub M24, complete set... the so-called "RTF" version.
Despite I am in Europe, my TX is in mode 1 (throttle to the right) and the included DVD was in Japanese (obviously), German, Swedish and Spanish... It would have been of more use if it were in either Dutch (as it was to be expected since I purchased the model in the NL), English or even Italian language.
Upon close inspection, the metal washer discussed above, between the nylon gear and the shaft bushing, is already in place in my model, even though it's not to be found portrayed in any of the exploded views of the model airplane (I downloaded other manuals relative to this model from Kyosho web-site, besides, obviously, I have the manual of its Park Zone equivalent).
I will soon try to put together a "review" on my Kyosho plane (before and after the improving modifications). As a very brief anticipation: despite the excellent look of the model and materials, not all components of the product were smooth, damage free and correctly mounted / designed (IMO), just out of the box. Packaging and storage, to which I attribute a part of the defects I found in the model, will be one of the issues of my review.
In the meanwhile, I pleasantly read through the whole length of this following thread:
http://www.rcuniverse.com/forum/m_18...r%2Ccub/tm.htm
There is a lot of very useful information and more!!!
Thanks to all in this Great Forum,
paolo66

Ferias flyer

Hi!
Thought about buying one of these, are they to recommend? Checked one out and both the main wing and stabilizer looked a bit thin and fragile.

Greg

jj69

Hi, I also live in Japan and have been thinking which way to go for my first RC plane. i bought a few TAIYO cessna r/c toys and have had immense fun with them but once they crash they crash and now want to move up to something more real. The kyosho cub was recommended by shops in Akihabara and looks the part but these problems with the motors seems worrying. Strangely the shop guys said it cant take off from the ground and needs to be hand launched?

How are things going with yours? The other plane that looks promissing is the J3 Grasshopper from Lee in China I think. It seems to get great reviews

http://www.abcmodelsport.net/p393523...ONIMHCHGR.html

where are you based by the way?

groundcheck

I'm a J-3 Fan. I did most of my learning on my Parkzone J-3. Other than the radio, the only diffrence is the Parkzone motor is more powerfull. The gearbox is the same, and the Parkzone suffered from gearbox problems as well.

I don't know how many flights I have on my plane. I had 4 batteries for it, so I could charge them as I used the others, and could fly all afternoon. I did go through 8 main gears, 5 gear boxes, and 2 motors before abandoning the original gear drive.

The gear drive is the only flaw in the plane. I used a Wattage 270 gear drive with a 370 motor installed. the 370 fits into the drive with only small changes, and has been flying the plane well for months. The plane can also be adapted for use of a stick mount gear drive.

A tail wheel will transform the plane into an amazing plane. Rise from Ground (ROG) takeoffs will be much simplified, and the ability to Taxi adds to the fun. But if you don't have access to a tail wheel, a simple toothpick tail skid will help. the rear skid on the plane doesn't have enough friction to keep the plane in a straight line. the main landing wheels are also a bit small for trying to take off on anything except smooth concrete. adding 45- 50 milimeter wheels will help it to take off from grass or rough surfaces, and make landings much smoother.

And while this is way off topic, there is one more modification that many people have been doing to the PZ J-3. We have a product called Great Stuff. its a self expanding spray insulating foam. I imagine they have a similar producr in japan. Adding some to fill the inside of the front section of the plane will greatly increas it's survivability on a crash

jj69

Thanks for this. Sounds good. Also looking around it sounds like Kyosho might have added the washer to solve the gear box problem. I suppose you havent heard about the CCLee or SDM products?

What exactly is the toothpick thing? Can u buy from model shops? Is that etter than the tail wheel?

jj69

Managed to eventually get the cub in the air.　It snowed in Japan so I thought Id at least have a soft landing but somehow managed to fly it into a small mound of ice. Its all taped up and still flying but have bought a spare to be ready for when it falls apart.

Somebody mentioned 50mm wheels...they only had 55mm so I bought anyway. Maybe too heavy?

Does anybody know if you can change the mode of the transmitter? Im in mode 1 but I think Id find mode 2 much easier!

Hope its good weather at the weekend!

Grasie

Hi all,
I have a Kyosho J-3
And have tried the expanding foam tip (works a treat)
nose dived into the ground bent the propshaft snaped the prop ouch!
Just want some info on motor and gearbox upgrades,
all so if any one know the pinouts for the servos, so i can use diffrent RX.

Thanks for any help

jj69

Hi Grasie,

This is Jason in Tokyo. I think we are the only two left in this blog at the moment. The strange thing is Im actually from England, and Middx as well. Whereabouts aare you based?

Re the Cub, Im pretty new to this but loving it. Am on to my second plane and haave rebuilt it with balsa etc but still flying good. So how easy was this expanding foam. can you let me know hoe you did it and aalso where you got the dtuff from? I was in the States recently but could not get hold of any, I think they thought I ws mad. Is there brand name over there.

Re the motor upgrades Im not really the man to ask but what I can workout is that the ParkZone model which is basically the Kyosho cub under a different brand runs on a 370 motor. Personally I think the 280 is good enough for me as space is also limited over here. Would love to put it on floats though but my model shop seemed to think it wouldnt be possible for that model.

where do you fly?

JJ