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Author Topic: Dynam Meteor 70mm sport jet  (Read 576 times)
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Measure twice cut once

« on: March 13, 2017, 03:26:09 PM »

What follows is my story with the Dynam Meteor 2. This is a 70mm fan sport jet. It looks like it was the loosing bid when Horizon Hobbies was contracting for a jet that became the Park Zone HABU. That might explain why the Meteor 2 looks a lot like the Habu at first glance.

I have to admit that in the past I’ve never been too impressed with the 70mm EDF. They general aren't big and impressive. Nor are they the small exquisite engineering marvels. (Yes, my Avatar is of the Robbe 4 engined  70mm BAE 146.) But in 2014 I was looking at a then new vendor’s site ‘MotionRC’ and was dumb struck at the blatant honesty I saw in their description of a brand they carried. In bold red letters on their Dynam sales page they had posted a notice that read something like:

Dynam models are a second tier supplier. You can expect some minor quality issues like broken screws and pinched servo wire. They often have shipping damage as Dynam does not use foam inserts in the shipping box. These quality issues should be well within the scope of the average modeler to correct. At their sales price they are a great value.

When I see a vendor level sets the customers expectation in this manner  I just had to patronize them. (I’m kind of that way with up front firms).

At that time (2014) there was little in the Dynam line up that appealed to me. Then I saw the Meteor 2 and for less than half the price of Horizon Hobbies  Parkzone Habu. So for $149 for an EDF jet with retract I told myself I couldn't go too far wrong.

The box showed up in short order, and I started to laugh before even getting it into the house. The box was crushed in the center by about 30mm to 50mm. The box is a big pizza style box and with no internal braces or support structure to keep the top and bottom from collapsing if any loads are place on top of it. You know, like what you would expect any shipper to do to get the boxes on the truck. Opening the box I found that the fuselage had distorted under the crushing weight from the normal shipping environment. I had to chuckle thinking of the red notice on the sales page.  

Upon close inspection I found broken screws and pinched wires just like the red notice said I would. I then examined the EDF unit to find that the rotor (impeller) had fused (welded) to the housing. The outrunner wires had pushed the motor way off center causing tip rub with the rotor and housing. What I found odd was that all these quality issues had a QA stamp near by. I’m sure the pass fail criteria for the EDF unit was does in run. And true to the inspection criteria the QA inspector could say, with a straight face, yes it ran at least once.

Now with my EDF unit the tip rub was so great that the rotor melted into the housing. I had to break away the rotor from the housing, then clean up the rotor and housing. At this time I gave the wires from the motor some clearance in the fan housing to allow the motor to center properly. With a little rework I was able to get the fan unit to run and run smoothly. Again the product was as described in the red notice on the sales page.

After another hour with some hot water and a soldering iron I corrected the other quality issues I noticed with the Dynam Meteor. I need to mention that I found a grave safety issue. The clevises on the elevator push rod were only attached by 2 threads. I feel this is criminal negligence not just poor quality control.

Now here is where I went a bit out of control.  Having recently flown my Freewing Me-262 and now being impressed with the performance out of the modern 70mm EDF I decided to upgrade the Meteor prior to flying her. I justified these upgrades as I had already spent a little over 2 hours bringing the Dynam kit to a usable condition.

First I added 3mm carbon spars to the stabilizer. As I like to “turn and burn” I felt the stab was too flexible as it came out of the crushed box. Also as I had to fabricate a proper length elevator push rod I upgraded the elevator servo to a 13 gram metal geared one (some Park Zone servo). I’m not comfortable using an economy 9 gram servo in a primary flight control application with single point failure in performance ships like the Meteor or Habu. [These models can go over 100 mph coming out of a dive] I also reinforced the foam elevator hinge with blenderm tape.

As I had a Change Sun 12 bladed EDF unit, a HET 2W-27 and a HobbyWing 100 amp ESC I thought these might make a fun 5 cell power upgrade to the stock 4 cell EDF power package. These all fit just fine with little or no cutting of foam. Well it was fine until I tried to balance the Meteor with the 5 cell 4200 mAh battery (496g Zippy Compact). I had to widen the battery compartment all the way to the back wall. If you plan on doing this upgrade make sure to add cooling troughs along the sides of the battery compartment as pushing the battery all the way aft will block the battery cooling holes.  (Please don’t ask how I know this).

As the Meteor was now getting heavy I decided to add flaps. This is easy to do, just extend the aileron hinge line and then cut the flap free at the wing root. I then cut 2 servo pockets and used two Dynam Detrum servos (PN. DY1007 and 1007R).

While massaging the fuselage back to shape the Dynam finish was damaged. This gave me the excuse I needed to refinish the model. And as a guy that likes to mess with the market and branding guys I chose to mimic the USAF Thunder Bird scheme, much like Horizon Hobbies did with the Habu 2. I stripped the Dynam blue with a product called Goof Off. This turns the paint into a gummy sheet that almost just peels off. I like this product a lot better than acetone. With acetone the dissolved paint often flows down into the spaces between the foam beads outlining the beads in the color you are trying to remove.  I used Tamyia paint and graphics from a Sig Kobra to get the desired effect.

Somethings that have come to light after test flying the Meteor are that the battery compartment is far to weak in the front over the retract. I added some carbon strips from over the retract all the way to the inlets. The retracts don’t have a coil spring strut. As a result all the shock loads go to the retract mount causing the retracts to get ripped out on all but the best landings. I’ve add a set of struts from the E-flite 15 electrical tracts. Also the steering Z bend and the steering fitting can become dislocated making ground steering impossible. I brazed a retention washer onto my steering push rod. This is another safety issue that Dynam needs to address.

Now to the flying! In a word FANtastic!

With the ChangeSun rotor I was drawing about 87 amps but only getting about 2.25 minutes of run time when as a result voltage suppression the ESC would shut down the power. It was fun for about a 3 minute flight, but these flight times are like what we had in the old days of the Sanyo 2000 mAh Nicads. I was looking for more flight time than what we had 20 years ago.  So I took a que from FMS when they cut down their rotor load by changing from a 12 bladed rotor to an 8 bladed rotor.  I found an 8 bladed 70mm rotor, in fact I think it is an FMS rotor.   As luck would have it the Change Sun housing is a 9 vane stator design so there was no high frequency ‘on' ‘off' loading we often get using an evenly divided ratio between rotor blades and stator vanes. (I tried a 9 bladed WeMoTec rotor in the Change Sun housing and didn’t like it).
with the 8 bladed rotor the amp draw is down to 65 amps. I’m getting about 6 minutes plus of flight time with no loss of performance. I’m flying at around 5/8 throttle stick as there isn’t much to be gained (speed wise) other than climb rate using more throttle.  I think that with the high amp draw 87 there is a large voltage suppression which is a lot less with the 65 amp set up, so the power isn’t down as much as the 87 amp vs 65 amp would indicate. Also the Meteor has a thick wing which adds a lot of drag keeping the top speed in check.

So how does my hot rodded Meteor compare to the stock set up?
Performance (Speed and Verticals ) she looks better. It isn’t like night and day, but I’d have to give my set up a nod in the 15%  to 25% range. What I like is that mine has this added performance and at the same time has dropped the noise, a lot. I also like that she flies heavier. That is she cuts through the wind much better. And with the added flaps she is more stable landing slow, she is less likely to tip stall on landing. But because of the added weight you can’t glide her in. With the flaps out you can drop in without gaining too much speed. Note; with the 4 cell stock set up (no flaps) you can land slower but the wings rock a bit.

A note about the Dynam retracts is in order. Contrary to what you might read on the MotionRC site and other forum sites the issue isn’t with temperature. The problem with the retracts is that the amplifier latch is too fast. Yes the resistor capacitor circuit in this latch is could be a bit more thermally stable. But the issue is in grabbing the pulse from the receiver.  I have found that if my gear would respond to the retract switch that changing the throttle or flicking the aileron/elevator stick into the upper right corner will trigger the retract amps. This has to do with the stability of the pulse train coming out of the RX. While I do make a gear down pass I have yet to land with a  gear up. Note that my model is 3 years old. I’m told Dynam has reworked their retracts to address this issue.

Would I do this again. I would say a qualified yes. If you want performance and a quite swooshing sound I think this 8 bladed set up is much more efficient than the standard 12 blade rotor we see today from most OEMs. If you can’t find an 8 bladed rotor the WeMoTec Mini Evo with the 9 bladed rotor would be a great substitute, even preferred. But this is a sport jet not a performance jet so I don’t think she is worth the effort in trying to get that big (500 grams) battery in her. I would upgrade to flaps as it opens up a whole new avenue in your flight profile, but leave her a 4 cell ship.

Compared to the Park Zone Habu I like the Dynam Meteor’s wing tips better and the placement of the ESC is far superior. The Habu has a better nose (more foam) and a smaller wheel well (less drag). And if you are more of a PNP/ARF modeler the Habu has the flaps already outlined for you.

The Meteor is a fine ship and great value, very easy to fly. Dynam kits often have quality issues. But if you are a true modeler these are often easy to spot and address. Even with the QA issues the Dynam are a great value just do a thorough check and burn in all the electronics for 15 minutes before your first flight. I love mine as a good sport ship.

Back in the day I called MotionRC about the quality issues. I got an appoligy and an offer for compensation. I said no thanks as their notice clearly stated what I would receive when ordering a Dynam model. I just wanted them (MotionRC and Dynam) to know the quality issues were noticed! Now if I call about a quality or technical concern they (MotionRC) hang up. It is painful to see how far a stand up firm like MotionRC has fallen!

All the best,
Attached files Thumbnail(s):
Dynam Meteor 70mm sport jet
Dynam Meteor 70mm sport jet
Dynam Meteor 70mm sport jet
Dynam Meteor 70mm sport jet
Dynam Meteor 70mm sport jet
Dynam Meteor 70mm sport jet

Cut it twice and it's still too short!
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