Synergy E750 Project complete: With Pictures and build details

[Chris Sexton]

Well I finally got my Synergy E7 stretched to 750 complete. Not a massive stretch by any means, but still had it's challenges. the Synergy boom uses a less than standard boom OD so i had to have custom CF booms made. The Torque Tube is a one off. Not that it is complete and tested, I am going to pull it back out and measure it. I want to try and fine some tube long enough to make out of one peice, for ease of replacement reasons. Let's face it, these things tend to crash :thumbup:

Here is a complete list of my setup and changes:

Synergy E7 TT
Scorpion HKIII 4035-330kv /w 13t pinion
Castle Ice2 160a ESC /w Hobbywing Digital RPM Sensor
Mikado V-Bar Blue Line, full size with 5.3 Pro
VBAR Gov: 1350/1420/1500
13.5 degrees of Collective Pitch
Agility:100
Cyclic Gain: 90
Tail Gain: 85
Gov Gain: 30
Savox SC-1267MG Cyclic Servos
Futaba BLS251 Rudder Servo
Fromco DCUP2 Cricket CAP Pack
Castle BEC PRO V3 @ 5.7V
Edge 753FBL Mains
Rail 116 Tails
Boom: 22x21x855 custom hand rolled reinforced CF tube
TT: Stock E7 tube extended 38mm
Tail Control Rod: Custom Cut CF tube from stock
Custom Vinyl decals on Custom Canopy

I want to eventually upgrade the servos, but with a Buffer pack, I feel comfortable with the Savox servos and the BEC Pro. I know the 1267s weren't reported to have the huge ramp up amps that the 2271's did, but I had the Fromco already, why not be sure.

I am playing with the Castle 4.01 beta software and the Hobbywing digital RPM Sensor. So far so good, bench tests all came back positive and the resolution on the throttle in VBAR is great.

It rained this afternoon and some this evening so I didn't get to maiden this ship today. But I did take the time to go through the setup one last time, just to be safe.

I don't know the final weight yet, but I can tell lifting it and my stock E7 I missed my mark on weight. It's still lighter than my X7 and Whiplash were with these same packs. I had to use my Hyperion 4200s to get it to balance. The 3700s I wanted to use were too light. Had them so far forward on the tray the canopy wouldn't go on.  With the 4200s, I am still ever so slightly tail heavy, i am hoping this will be ok in flight. If not, I will be adding a few grams to the nose for sure.

Thanks for following along. I hope to see you all at IRCHA Friday for the Synergy Team Photo!


Pictures:

[JustinProud]

Nice work. 

[Ross Lawton]

Awesome Job!! I have to say that is one wicked looking canopy!!

Cheers!
Ross

[Chris Sexton]

Maiden done! It flies!

I just put a quick 4 minute light basic hovering and mild forward flight on the frame. I noticed a couple of things I need to look into.

1. the head has a minor shake, could be blade balance, could be bent shaft, could be worn dampeners. I got the frame used from a very reliable source, but it does have plenty of flights on the head already.
2. One of the TT bearings must have some CA in it, I am hearing a clicking on spool down in the boom.
3. I am going to have to rake the skids a bit, the tail touches easy. Didn't do any damage but too close for comfort.

Other than that. It tracked straight, flew well and the blades sound AMAZING at 1350 and 1440 rpm   My collective management skills aren't there just yet, so I will probably spend the most of my flights at idel2 which is 1500, but the tail held well!

I doubt I will have time to completely eliminate these minor issues before IRCHA, but I will at least take the head and TT apart and see if there is something obvious. I am also going to pull the VBar logs to look for issues there.

[steffgiguere]

Anxious to see it.

[Chris Sexton]

Made a few changes. The head wobble was the resonance at 1500 head speed. No wobble at all at 1300 and 1400. Going to put the 14t pinion back in and see of the head smooths back out at 1600.  It flies fine at 1400 but the tail is weak. That's probably my crappy collective management skills.

I also upped the tail gain as well as turned the gov gain down. Tail is locked in fff. Start throwing the collective around and it shows signs of potential blow out. Again my crappy collective skills there.

I will probably spend more time at. 1400s but I want to know if I am right and the head will smooth out at 1600.

So far the frame is holding up well!


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[Chris Sexton]

Anxious to see it.

It will be with me at the synergy booth for team pictures.


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[Chris Sexton]

Ok a couple final points.

1. I purchased longer boom support rods and new boom support ends from ExprienceRC while at IRCHA and moved the tail boom clamp back farther. Matt seemed to agree that the boom was flexing more than acceptable. This little touch helped brace the boom enough that my boom flex on hard rudder inputs is gone.  I am still hunting down an aluminum solution for long term functionality.
2. I put the 14t pinion back in it and now have 1450/1550/1650 head speeds setup. Head resonance is gone. Flies solid and at 1650 the tail has plenty of authority and would not blow out on even the harshest collective punches.

I have now flown this heli a total of 12 times. Most of those at IRCHA. This thing is a keeper! It's wicked fast and with the 5000mah packs, I had my timer at 7 minutes and the packs were at 3.90 rested.

Thank you to all the pilots that stopped me and asked about it. I never expected to have this kind of interest in a pet project of mine.

Hopefully I can find a more labor friendly solution for TTs but the effort was well justified after tweaking the setup.

Sorry you guys didn't get to see it fly. They closed the flight line at IRCHA for noon demos and I had to go to site 3 to get and flying in as I had to leave at 5.

See you all in Lexington

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[Chris Sexton]

Well this project has been shelved until I can get either a higher quality CF boom, or an aluminum boom. The two 855mm CF booms I had made are too weak and on hard rudder inputs flex severally

At first I thought all was good but as I grew confident in the heli I started trying harder and hard moves to stress the boom.  I am getting a serious deflection on hard tail stops and reversals. Makes the heli look as if I am entering a piro flip it kicks the tail so hard.

In FFF it seems fine, reverse flight or funnels get scary fast.

It's a fun idea and I hope to find a vendor for a permanent boom solution, but for now it isn't worth risking a crash and or getting someone hurt.

[Matt Botos]

Thanks for the update Chris. Hopefully I can work on an E750 project this winter.

Thanks,

Matt

[Chris Sexton]

Thanks for the update Chris. Hopefully I can work on an E750 project this winter.

Thanks,

Matt

Now that would be awesome! A factory upgrade with maybe a little faster tail ratio. I would be on the waiting list now :

[Chris Sexton]

OK I was just told on RR that the N9 boom is also 22OD and is long enough for me to cut down, if that is true, that is GREAT news.

Two questions, those of you with N9 experience.

First, I can't find the boom and TT specs listed anywhere.  Is the TT compatible with the TT chucks the E7 uses?  If so I have my solution, GrandRC has the booms and TTs in stock!

Second question, what's the tail gear ratio on the N9? Is it worth possibly looking at the N9 tail box to get my tail rotor spinning faster?

[Chris Sexton]

Well grand RC inventory was wrong. They do not have the boom in stock. Still looking.

And Rob Cherry reminded me that the torque tube on the E7 is 8mm hollow.  The N9 TT won't work.

My custom torque tube is holding up fine. I just need a medal boom.


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[Kevin Feil]

Chris if Matt doesn't beat me to it first I got all those answers for you. I will hit you back when I get home later this evening, The N9 boom is longer than the e7 and it will work if I'm not mistaken. I'll get back to you on that..as far as the tail chucking up it will because Dan did it with his E7 transmission upgrade on the E9... Pm him as well.. "Dycocker"

Kevin

[Kevin Feil]

get with Dan on the TT portion of your build, I have tail booms for the N9!!!

Kevin