Posts: 2
Joined: 5/12/2004 From: ChobhamSurrey, UNITED KINGDOM Status: offline
Greetings all...
I am a total novice to helicopters, and am currently experiencing a steep (and expensive) learning curve. After mucking about with the Hummingbird and Piccolo, and finding them really awkward to control - a stable hover is just a dream (nightmare) - I bought a Protech Zoom 400. The difference in build quality and value for money, compared to the aforementioned, was staggering... Anyway, after much trial and error, I finally came close to my dream goal - actually hovering one of these confounded machines, when... hard landing shredded the tail output gear, it being plastic, and the input gear being brass(?) - metal anyway. One new Zoom later, for spares, same again! Not happy... Is this a problem? Can I expect tail in landings to destroy this part, even though the rest of the heli remains unscathed? Don't suppose there's a metal replacement??? Even though I'm a novice, a grounded heli seems a high price to pay for a relatively minor error...
Posts: 269
Joined: 3/3/2004 From: MelbourneVictoria, AUSTRALIA Status: offline
I cant believe you bought another however I am sure it will come in handy.
I managed to strip my tail gear when I forgot to turn off the brake on my ESC. Basically when you throttle off the tail comes to a dead stop imediately. The next couple of teeth came off on a hard landing like yourself. I kept flying with a bit of tail wagging until I got a spare.
Apparently there is a stronger/tougher plastic gear made since this is a well known problem. I ordered a couple of the new ones through www.tedani.com since he told me about the new design and had some in stock. You can check with your local dealers to see if they have it ?
One more thing - If you are coming down a bit too hard you may want to raise your pitch curve at 0% and 25% so that it doesnt have that much negative at low throttle.
< Message edited by jbalat -- 5/13/2004 5:50:57 AM >
Posts: 25
Joined: 1/10/2002 From: Covington, GA, USA Status: offline
Yes, you can expect to keep breaking tail gears. Micro helis are not designed for abuse. They are very fragile compared to a 30 sized helicopter. If you had metal gears then you would just break the torque tube or strip the gear at the other end of the shaft. On the other hand, there small size really makes them cool.
If you are still learning then try not to use hardly any negative pitch. The helicopter will not have a tendency to slam into the ground when you get to aggressive on the collective.
Posts: 2
Joined: 5/12/2004 From: ChobhamSurrey, UNITED KINGDOM Status: offline
Hi.
Thanks for the replies. And thanks for the tips about the negative. Like an idiot, I'd selected a new model memory in my Futaba FF9 and completely forgot to alter the pitch curve (duh!).
Posts: 227
Joined: 10/30/2003 From: La Habra, CO, USA Status: offline
are you saying your tail rotor blade touches the ground and therefore shreds gear teeth? or blades aren't touching anything yet hard landing some how shreds those gears?
Posts: 269
Joined: 3/3/2004 From: MelbourneVictoria, AUSTRALIA Status: offline
The gear strips when the tail rotors touch something. This may be a hard landing or backwards landing or smashing into another object.
I originally stripped my gear on the first day since I forgot to switch off the brake on my esc. It did not like it when coming to a sudden grinding halt from high rpm...
There is a stronger gear available now if you ask your hobby dealer.
Keep in mind that something has to give. If its not the gear it may be something else which is more expensive. A flexible drive shaft and beefed up gear may be the answer ?
I have my zoom hard landed with tail blade hit the pavememnt first. the gear stipped. But I then changed the gear with those from my sons cars spare part. It is very cheap ( 20 pcs for USD 1 ) . I have no more fear of stripping the gear.
Posts: 33
Joined: 4/1/2004 From: Alamo, CA, USA Status: offline
YES! Please! Where did you get the gear --- or more specifically, where may others find it? The Zoom/Shogun is a TERRIFIC machine, an order of magnitude more stable than any Aerohawk, Dragonfly, etc... BUT the Achille's heel is that nylon tail shaft gear. If anyone were to come up with a source for this gear, he would earn the undying gratitude of the Zoom/Shogun community. If anyone knows of a substitute, here are the specs for it (sorry for the crude image, and I hope it loads OK):
This is a crown gear; it meshes with a standard pinion to change the plane of rotation by 90 degrees. Many other helis do the same thing with a couple of 45 degree miter gears instead.
The gear has 20 teeth. It is too small for me to measure the angle & rake of the teeth. Dimension A, the gear head diameter, is about .436"; approximately 11 mm or 7/16". Dimension B, the barrel diameter, is about .180", or 4.5 mm. The barrel bore is a star shape, and it fits tightly onto a 2 mm (.078 max dia) hex (6 sided) shaft. The shaft measures .069-.070" flat to flat, and .078" point to point. or max dia. Hope that makes sense. It may work to take a standard circular bore and jam the hex shaft through it; what's important is that the gear not turn or slide, on the shaft once installed. Dimension C, height of gear teeth combined with gear wheel thickness, is a bit less than 1/8" or .125. Overall length of the gear barrel, which any moron would have remembered to put in his drawing, is just under 1/2"; I measured it at .49". Material appears to be nylon; delrin or metal might also be OK, although I think this is a designed failure point to protect more expensive stuff further up the gear train line, and metal might not be the best choice in the long run; replacing this gear may just be the price of owning a terrific micro heli whose tail motor doesn't need replacing every 2 days. If anyone knows of a quick & cheap source, PLEASE let us Shogun/Zoom/Dolphin owners know!
< Message edited by meb48 -- 6/1/2004 4:50:33 PM >
Posts: 6
Joined: 6/1/2004 From: Philadelphia,
PA, USA Status: offline
hadis,
Are you going to give us some more info, or are you going to keep it a secret??? I've searched, and I can't find 20 packs of any Tamiya crown gears anywhere. The closest I've come was crown gears for slot cars, which look very promising ;-)
Posts: 53
Joined: 6/3/2004 From: Herts, UNITED KINGDOM Status: offline
Hi,
I've found that if you have the screw (holding the blade in) too tight, it increases the lightly hood of stripping the gear. Obviously too loose presents a more costly repair should the screw decide to do the off!!
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zoom 400 tail gear problem - 
