|Oct 11, 2012, 08:33 PM|
Joined Nov 2009
The MD 900 is a current helicopter, still in the range of Vario, and probably they are going to cotinue this model for some time more, it is one of their eyecatchers.
Usually Vario has pretty good service, just contact their importer, chances are, they have virtually everything in stock, and will ship promptly (at least, that is one of Vario's key marketing points, quick spare delivery)
Vario helicopters are usually of very good quality, but since these kits (and the Notar in particular) need considerable building skill, flight quality is completely depending on build quality. Especially the construction of the tail rotary valve is pretty critical. If it is an early model, chances are it has a cable operated flapvalve, that unfortunately was discontinued quickly, so please check this.
If the radio equipment is in good condition, don't change it; it does not give any benefits as long as the servo's (especially the tail) is within Vario's specs. Swashplate should be OK with 4 x S9202, or 3 x S9206
Tail needs a strong digital servo, fast is less important
As long as the gyro is not a mechanical one, no need to update. Scale helicopters do not really need high-end gyro's and these helicopters typically tend to not really like those high end stuff either (it is possible though). A Futaba G 400 or GY401 should be all you need.
The motor should be good, Webra's were excellent engines.
They don't like high Nitro content, and usually this motor should be fine with either 0% Nitro, 15% fully synthetic, or if you prefer, 5% itro and 18% full synthetic.
Don't use more Nitro, unless compression ratio has been adjusted accordingly.
This particular helicopter has a gear ratio of 11.2:1, and you definitely need as a minimum 1350 RPM on the head, in order to get sufficient engine RPM to keep the fan in its effective range.
Due to the (slightly unusual) gearing ratio lots of people make the mistake of adjusting "by sound" and ending up with too low RPM, not enough tail authority, and I would not be surprised if that is the reason you got it that cheap.
Just let it rev high (adjust the pipe accordingly) and enjoy.
Take care, this helicopter requires a lot of power, so fuel consumption is probably high, typically allowing for max 10~12 minutes of flight on the 500 cc tank.
Due to the partly downwards directed airflow out of the tail, the tail tends to lift. these helicopters should be balanced 1/2 to 1 inch tailheavy!
Have fun with it!
|Oct 12, 2012, 12:03 AM|
Joined Aug 2005
|Oct 12, 2012, 12:10 AM|
United States, TX, Mission
Joined Jun 2007
Wow Brutus that was quite a report on the MD 900, I already started taking her apart for cleaning and repairing, hopefully I'll be fliying her in about a month. the notar is the servo version,S9250 servo on the tail. I'm attaching pictures of the tail and boom duct.
|Oct 12, 2012, 02:38 AM|
Joined Nov 2009
Me and my hobby-buddy are building together (regardless whether it is mine or his helicopter ont he buidling board) and currently it is his MD900 under construction....
I see you have the two bladed version... than 3 x S9202 is OK
For a mutliblade these servo's are on te lower limit but for a paddlehead it is OK.
The S9202 and S9206 are in my opinion the best swash servo's ever....
As far as I know the 9250 is OK on the tail. Just check if that tail cap is rotoating smoothly..
Please be really careful with "re-doing things", these heli's really dislike excessive weight (they are pretty heavy as is), don't go over 6.5 kilo, because every ounce loads up the tail system, and even if that system is sufficient, it does not have the power reseves of a conventional tail rotor...
Vario's are usually designed to be functional on the inside, and I have seen several Vario's being built too neat, too tidy, reinforced where no reinforcement was needed, modified where no modification was necessary, and ending up to be too heavy to fly good.
Usually, a Vario built according to plan, flies (within the limits of its design) impeccable.
The GY 240 should be able to do the job as well, personally I would not change that for something different.
Lots of "tail problems" that I see reported here, can be solved by going back to a low-tech gyro and some practice in manual tail control, rather than high end gyro and superfast servo and endless adjustment. Especially with non-conventional tail systems like NOTAR and Fenestron, this seems to be the case.
Good luck getting it back into the air.
PS: what did you consider "dirt cheap"? New price of this helicopter will be somewhere in the area of 2000~2500 Euro, depending on installed components and rotorhead
EDIT: forgot to mention: I saw, you are flying T-rexes and Raptors: These big helicopters, although completely up to the job, don't like rough landings, so while in the process of rebuilding and repairing, practise your landing skills with respect of soft touch downs.
Set your pitch curve to -2 degrees minimum, +5 degrees midstick and 9~10 degrees maximum, and make sure your throttle curve keeps a constant RPM while airborne or you will REALLY get into trouble....
You CANNOT fly these big machines with the curves usually flown in Raptors and T-rexes. The fuselage and landing gear are not designed for it (if they were, the thing would become too heavy to fly, so please think twice about reinforcing those areas).
|Feb 16, 2013, 08:55 AM|
Varios are gorgeous!!
Sandy Jaffe has some beautiful Notars.
Always a treat to see why he brings to our fun ly each year.
Here is his Notar and a few other beauties!
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