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Old 03-18-2013, 03:19 PM   #181 (permalink)
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Default MD500 TOW Defender Logo 500 Build

The scorpion 4035-450kv?

That's the motor I'm using, lots of power on tap, hope you'll be happy with it!
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Old 03-18-2013, 06:47 PM   #182 (permalink)
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I hope so too. It's a shame that the motor did not have the power needed to fly the 16 pound (and growing, as there is more interior to come) porker with some power to spare. By the time the weather gets better (snowing and blowing up a storm outside right now), the motor and shaft will be in and installed.

I just finished a rather important job that had been partially done but not finished. I went out and bought a digital scale capable of measuring up to 350g. at .1g resolution. My blades that I had thought I had balanced, were close but I found I had the two heaviest blades right side by side and they were not very much off, but put both of them in one spot and that will start the vibrations the Skookum will pick up. They are now all at 119.1g with no tape needed. They were all on the money for individual COG, though, which was very impressive. I added just a bit of tape to the tail blades as they were off a bit. I have one other set of blades to check and a set of bearings to replace in the Airwolf chassis. You can wobble the main shaft side to side and front to back, they are that bad. Oh well...

Don
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Old 03-22-2013, 04:17 PM   #183 (permalink)
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Just an update, pictures will follow later, but I am taking them as I move along. The motor came in yesterday and so did the shaft kit to convert it to 5mm. I wish it was not so tightly fitted but of course, that leads to no play in the long run. It was a bit of a slog getting it installed as the mechanics had to come out once again but that is now becoming routine, and getting quicker each time. The motor is the same diameter but 10mm taller so I had to bust out the chassis cover and I am now in the midst of making up a bunch of new side pieces. I can only reuse the front upper panel that was in there from the first cover. The lower parts are ok and only need a wedge of wood to fill in the new angle. When I put this in the first time, I had just the shoulder wall on its own, so fitting parts and sanding was not big deal. It is now. The wall was Hysol'd into place and it not moving any time soon. Live and learn. I should have sold the 890 new in the box and bought this motor in the first place. I may also have to buy a new ESC but my experience so far is that I am nowhere near the regular operating capacity of the CC 85HV so moving up to a 120 is just wasted money and no return for it. Logging is good but not 225 bucks worth of good. It should be airborne tomorrow if the weather is good or Sunday if it is a freeze-out tomorrow. I'll post the pictures ASAP. Take care.

Don
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Old 03-22-2013, 05:03 PM   #184 (permalink)
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You're running 12S now right?

On my test mechanics I log about 18 amps in the hover at 1300rpm governed and a hard climb peaks at around 36 amps... That's at an AUW of about 6.5kg (14.3lbs).

I run using a YGE 90HV and it comes down barely even warm.

The 85HV will be ample I'm sure.
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Old 03-22-2013, 05:39 PM   #185 (permalink)
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Yes, it's already converted (reworked the harness so that the harness is now part of the ESC and the batteries connect directly to it. The pictures later will show how I did it. I found the little trick in someone's 600EFL Pro picture post in the 600 Electric Helicopter sub-forum. So far, I have two parts made and should be able to get it all done this evening/night and have it ready if the weather is good. I am amassing a collection of motors and ESCs that will never be used so I may keep them in my truck and bring them to the club to flog them. I think I have two 70a ESCs, three motors for 6-8s, and a few tail gyros and servos. That's just the tip of the iceberg, lol. Take care.

Don
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Old 03-23-2013, 12:20 AM   #186 (permalink)
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Here are the pictures of the reworked cockpit and motor installation. There are only a few changes to the chassis but I wished I had this configuration when I made the chassis cover as the cover was offset for the original wiring. Oh well, can't win them all and I was not going to build a completely new cover. Take care.

Don
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Old 03-23-2013, 04:20 AM   #187 (permalink)
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With regard to what you were saying about retreating blade stall, i don't think this is an example of it.

Retreating blade stall manifests itself as a hard roll or a flip, but simply falling. I think you are seeing the loss of transational lift as the disk presents a hard angle to the direction of movement.


The way I understand retreating blade stall is as the airspeed of the rotor disk approaches the rotational speed of the blade they cancel out.
The retreating blade is effectively staying stationary in the air and the leading blade is going twice the airspeed, so this makes the forward blade super efficient and the retreating blade useless.

For example the airspeed of the disk is 150 mph the rotor blade tip speed is 200 mph, this means that the forward approaching blade is effectively doing 350 mph and the retreating blade is effectively doing 50 mph.

So you have no lift at the rear of the rotor disk and high lift at the front of the disk.

Couple this with gyroscopic precession and you get a hard roll as all forces act at 90 degrees to the application of that force.

This is why helicopters can't fly as fast as planes.

Sorry to digress from your excellent work, and it looks fantastic in the air by the way ;-)

/Steve

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Old 03-23-2013, 05:51 AM   #188 (permalink)
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So you have no lift at the rear of the rotor disk and high lift at the front of the disk.

Couple this with gyroscopic precession and you get a hard roll as all forces act at 90 degrees to the application of that force.
Slight correction - right idea but wrong order... you have a loss of lift on the right side of the disk on a CW rotation head (as the blade span passes through perpendicular to the forward airflow)... Through gyroscopic precession this is translated to a downwards force at the back of the disk resulting in a nose up condition.

That's the first sign of onset - nose pitching up. It also means its a naturally self correcting condition if you release the controls as the nose pitching up results in airspeed slowing down and thus relative airspeed of the retreating blade increasing.

It's only once you have totally catastrophic blade stall that it might roll to the side of the retreating blade.
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Old 03-23-2013, 09:56 AM   #189 (permalink)
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Thanks for the compliment, stevec.

So, what has actually happened is that I was descending through the downwash and had not actually brought on a stall condition yet, but a loss of lift defined as settling with power. I was flying downwind at that time and the mistake was making the start of the turn without enough forward speed to keep out of the downwash of the rotor. I have done the same turn only to the left and had seemed to not have the same problem. Anyway, thanks for the explanation and correction but it is now time to get ready to get my bird airborne once again. Take care.

Don
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Old 03-24-2013, 10:48 PM   #190 (permalink)
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Good news and Bad news.

First the good: 12s 450kv and the existing gearing is the sweat spot for this helicopter at 1350rpm. Tons of power, I can add the pitch I took back (climbs like a scared cat up a phone pole), and the power range is so much higher, if I get descending through dirty air, it can power out of it. This helicopter climbed so fast, it was up to 300ft. before I knew what was happening. When I did the last climb test, it bogged out at far less than full collective. This time out, I could put it to full collective (14 degrees of pitch) and it just climbed. The power returned to the two batteries was around 2200mAH per battery for a 7.5 minute flight. It should be under 2000 per battery for my usual 6 minute flight.

Now the bad: I got cocky and didn't check the batteries so I got all that height and started to wind down in head speed. I barely made it to the ground in time but the landing was very hard and the rear left gear snapped. Fortunately, the skid bit into the soft ground and the TOW missile launchers prevented the helicopter from turning on its side. The tail housing slipped forward but that was not such a big problem but it did highlight that the housing needs to be changed. I guess it is its last flight so another is going on the order checklist. So all in all, the one leg broke and the wires snapped clean inside it. That will be a simple change once I get the new legs in, as I will repair this, less the light working, until the new ones get in. A couple of wire staples Hysol'd in should do the trick. Oh well. Back to the bench, lol. Take care.

Don
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Old 03-25-2013, 07:59 AM   #191 (permalink)
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All the fun of the hobby - glad it wasn't worse.
Just think of that damage list if it had fallen over
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Old 03-25-2013, 08:48 AM   #192 (permalink)
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Yes, lucky!

Sorry to hear you got any damage at all, but as you say could have been much worse.

Are the skids easy to get hold of separately?

Glad the new power system is working for you - I found the same, a governed 1300 or so gives more than enough power to really pull through anything.
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Old 03-25-2013, 10:48 AM   #193 (permalink)
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Thanks. The srut is already repaired and as far as I know, the struts are a regular stock item. I need to get on it right way, though. I know an order is coming in from overseas so if I get it in now, I may only be waiting a couple of weeks. That is why the repair and not just hold on. Two 1/16" piano wire staples embedded in Hysol will hold like steel reinforced concrete. It should be back together this afternoon at the latest, less the landing light in the tip. Take care.

Don
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Old 03-25-2013, 01:28 PM   #194 (permalink)
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Awesome job on the heli Don, sorry to hear about the damage, but i have no doubt you will sort it ansd have it back to it's former glory double quick
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Old 03-25-2013, 03:15 PM   #195 (permalink)
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I am amazed by this work. I am amazed you got a logo 500 into that canopy. I looked at trying that and quickly decided against it. It seemed impossible to me. Well done.

I skimmed the thread but I didn't see, what head speed are you running?

Thanks for sharing this incredible build.
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Old 03-25-2013, 04:09 PM   #196 (permalink)
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Thanks guys.

billyd:

The truth is that it was a matter of scrounging some CF from a tail fin that made the entire cutting a bit of child's play. It only took moments and a very sharp saw to cut the chassis where I did. It was the measuring over and over that took the time. I too, was amazed that I was able to get the chassis in there because of nearly zero clearance of the chassis boom to the bottom of the fuselage boom at the main body join.

I am currently running 1300 rpm on spool-up and 1350 in the air. I have 1400 on tap but it does not sound as good. I may fly it around some more with the higher head speed (same as my AS350) but I think that all I will get is faster forward flight, which is not my objective. Right now, the fastest this helicopter has flown is 67kmh, which is at my target "no faster than" speed. Most of the time it is in the 35kmh range. Thanks and take care.

Don
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Old 03-27-2013, 11:16 PM   #197 (permalink)
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Last night, around 2am, I decided to add a unit insignia to the tail and the uniform sleeves of the three figures. My printer was plugged and could not be cleaned plus I could not find my clear and white label materials. 75 Bucks later, I got them done with a bit of help from Photoshop. This is sure as shootn', a one of a kind helicopter, lol. At least the printer is good for another couple of months. I need to get it out more often.

Don
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Old 03-31-2013, 09:25 AM   #198 (permalink)
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Yesterday was a great day for flying. A bit breezy for planks so they eventually packed up and stayed on the ground leaving the skies to the helicopters and it was done in style. I got 4 flights in with my TOW Defender and it gets better with every flight. The power the motor puts out is fantastic so those moments where it looked like the bird was on its way to the ground are gone. The funny part of this heli is that the speed it flys down the runway at is very misleading. As fast as it may seem, it maxes out at about 60kmh (about 45mph). I still need to get the tail gain dialed in but there is lots of tail authority. I put in 5 flights with my Jet Ranger and this one has really picked up speed this year with the change of the pinion. It was a stock 16t pinion and I changed it to a 15t with the results that the power draw went up but the sound is music to the ears as it does sound like a turbine inside. The wind never fails to pick up just as I am about to fly and does the opposite for others, sigh. Maybe this week I can catch a break and get some calm air flying in to make up for yesterday. I need to get more video shot of it and get my tripod out of the studio and into use with a camera on it rather than my laser line systems. Take care.

Don
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Old 04-01-2013, 03:55 PM   #199 (permalink)
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I have a question for you since you have built a few scale heli. I have a Trex 450 that I installed in RCA G-Jive 500 running a 5 blade rotor system. The first hover ck the head speed was to high don't remember the numbers it's been since last fall I mess with it. I change pinion gear on motor the head speed to me was still to high hovering 1-2 min at a time. I change motor and pinion same result still to high. On the fourth or fifth change pinion again hovering about a foot off the ground the heli shook violent pop the nose off and broke the vertical fin. Airframe was tight to the fuselage I don't get it! I'm just wondering if the rpm change had anything to do with it. Never had a problem until reducing the head speed.I saw on YouTube a guy was hovering a Blackhawk for few min and it exploded not sure the reason got to be something I'm not aware of. What's your opinion on this issue.
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Old 04-01-2013, 05:22 PM   #200 (permalink)
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The problem here is that I don't know your helicopter so you will need to tell me what motor, pinion, head, blades, etc. that you have or I am walking in the dark with no lights on. The nose popping off sounds like a harmonic vibration where the body starts to shake because of the chassis being in need of sorting out. That Blackhawk, which shattered, I have seen before and my original thoughts were that the doghouse popped up into the head but I downloaded the video and had a really good look at it frame by frame. It seems to me that the chassis became separated from the body (repeated hits to the asphalt) and the torque of the blades caused the chassis to break out of the body, ripping it apart as it came out. A lot of glues that people use (yes, companies too) are not suitable for bonding to fibreglass and in a lot of cases, better adhesives are used to help with factory assembled woodwork. I have an Align A109 body that needs to be re-glued in a few spots because of the glue breaking its bond. Not a big deal as it is in one spot but now imagine the entire woodwork letting go at once and you have the Blackhawk in that video.

Give me a bit more info and we'll see where you should put your attention. Take care.

Don
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