tean
Senior Heliman
Location: Gloucestershire,UK
| I've just finished building a Viper 70 and thought I'd share some thoughts:
I bought mine as a complete package with motor and controller. Beware! The pinion is not included. The controller supplied is a Lexors H70 which is rated at 70amp and is much too big and heavy. A smaller 40amp controller would be much more suitable. The motor, a H8, is a dead cute little outrunner.
The kit goes together quite easily and quality of the parts is good. Exception to this is the swashplate which is a nasty, bendy plastic affair in which the centre ball sticks horribly unless you attack it with a scalpel. There is plenty of pitch range for inverted flying, but watch for the ball links touching the maingear at the extreme top. You may want to cut a notch in the front of the tailboom before you fit it to give more room for the rear servo's link.
The two stage geartrain runs nice and smoothly and is equivelant to a 120 tooth single gear. The H8 motor with the recommended 19 tooth pinion gives a headspeed of about 2500rpm with a 3s battery.
The tail features a novel torque tube control. This is slop and friction free, but is let down a bit by the plastic endpeices which strip if you even look at the grubscrews harshly. The tube arrangement effectively gets rid of the servo arm, so you're totally reliant on the travel adjust in the transmitter to set the throw. I had to reduce the travel to 30% each way and this could well be a problem if you want to use a heading lock gyro that doesn't allow for end point setting.
The tail pitch slider has a roller bearing instead of the usual ballraces. This seems to me to be poor design as the flange on the end of the brass sleeve rubs on the steel case of the bearing. Despite assembling it as per the instructions with a little bit of play and oiling it, after two test flights I noticed brass filings. The brass flange had half worn away. Another two or three flights would have seen it fail. I have temporarily placed a nylon washer in here and it seems to be fine for now. Replacing the roller bearing with ballraces would seem to be the long term cure.
The canopy is pre-finished but the stickers are poorly applied with many wrinkles.
The setup at present is:
H8 outrunner motor. Lexors H70 controller. 19 tooth pinion. Flightpower 3s1p 2500mAh lipo. 4x JR 371 servos. JR G400 gyro.
How does it fly? Well it's only had some hovering and gentle flight in the garden so far but it seems very good. There is loads of power from the motor and the Flightpower 3s1p 2500mAh battery gives about 9mins of hovering. I can think of some mods to get the weight down so this might get better. The model is very smooth with no vibration and it makes a nice, non-screetchy noise. The weighted, wooden blades track well. There was an intermittant wobble on the first couple of flights, but this seems to be going away by itself. The fat tailboom and yellow canopy help orientation and the cyclic response (I left the flybar weights off) is strong but not twitchy. The hovering response is a bit soggy, probably due to that yukky swashplate. After flight, the motor and controller are only slightly warm, but the battery is up around 48C. Some vent holes in the cabin would seem advisable.
I'll add some more when it's been hammered about a bit.
Logo14 Vbar, Logo500 CSM flybarless, Trex 600 CSM flybarless, 3DMP, Logo10, Lipoly, Mini T, ....... |
