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Old 04-13-2008, 02:48 PM   #1 (permalink)
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Default My Sexy TREXY 500, finally! (Build Report)

After months of homework for all the mods, I've finally finished my TREX 500.

The build took a long time and I found that I had to do many more mods then were required for either my 450 or the 600 builds. Some of the mods were required and some I just wanted to do. Ultimately, I’m really happy with the quality of the completed bird.

I tried to stay top end on the components since I have found that spending more up front usually costs me less long term and I am generally more happy with the heli. I didn’t follow this to an extreme though since I didn’t opt for a Jazz ESC on this build.

ESC: Stock Align
Cyclic Servos: JR Z3650s x 3
Tail Servo: Futaba BLS251 Brushless
Gyro: Spartan DS760

Component placement is always critical for me so I built off of all the lessons I have learned from the 450 and the 600 as well as lots of Helifreak input. Here are rules I generally try to balance while laying out components. Most of these came from Finless Bob years ago with an associated EEEK.

1) Isolate high current noisy components (Main Battery, ESC, and motor) from low current parts (Antenna, Battery, gyro, gyro controller, and receiver)
2) Protect all components from crash damage
3) Make heli parts you replace regularly easy to replace (Bottom Plate, Tail boom, belt, tail pulleys, etc)
4) Keep wiring runs short
5) Protect all wiring
6) Assure continuity from head to tail. (Newly added rule with this build)

Here's what I came up with:

I avoided running any wiring through the boom block area so it could be easily removed. I ran the wires on the outside through this area.

Side views with no canopy

The receiver and gyro were combined into one Electronics Module. It’s completely protected inside the rear of the machine and easily removable as an entire unit. This allowed me to minimize the wire runs between these components. I couldn’t use one of my TREX500 gyro trays since the Futaba receiver has its plugs on the top so I made a variant tray that slides in the back. The rear two plastic bottom plate screws secure it in place while allowing it to be easily removed. I was trying to avoid any rewiring when I have to swap out the plastic bottom.

When shortening the gyro to rudder servo run, I included a drop down diode under the shrink around the tail servo connector.

The ESC was placed inside the front to protect it and minimize high current wiring. It fits under there with no altering of the stock ESC wires like it was made to fit. I'll keep watch on that area for heat since both the motor and ESC are heat generators. I used a similar approach with my TREX 600 and have had no problems with it.

The ESC control line is isolated to one side away from all the servo runs. Each servo wire was run in its own sleeve to allow easy replacement if a servo dies. The Elevator and rudder servo wires were shortened, but the aileron and pitch servos were just barely long enough. I left some slack in the wiring in back to allow me to wire the Electronics module while shifted out the back.

I opted for a Revolution Whip this time just to try something different than the Deans. I used the antenna bobbin approach that OICU812 showed me while building my 450. I still use my 72 MHz receivers since they have served me well and I’m kind of waiting for the 2.4 radios to mature a bit. Notice also that I never run any wiring below the skid mounts because I have often seen the skids ripped off in a crash.

I opted for the Spartan DS760 gyro and Futaba BLS251 brushless tail servo (thanks OICU812) since I really want a locked in tail and was willing to pay a bit more to get it. Since the BLS251 is a full sized servo, I had to use a TREX 600 tail servo mount with the TREX 500 boom rings. I've seen others grind the 500 mount and make it work. I did use a drop down diode since this servo expects a 4.8 volt input and I wanted to drive my cyclic servos with the higher voltage. I was a bit worried about COG with the larger tail servo, but with the canopy mod and overall component layout, it balances perfectly without even having to move the battery down on the it's tray.

Since ESD is an issue for this heli, I did a number of things to minimize it. The main thing I did was make sure I had conductivity from head to tail through my frame and metal components. I did all the following mods to limit ESD:

1) Use metal tail and assure conductivity from shaft to boom. I used a file to scrape off the anodize just under the screws where the black plates connect to the silver frame. I also sanded the inside of the tail assembly where the boom enters. I filed the paint off the boom at both ends.

2) Copper foil on boom block to assure conductivity from boom to pulley to frame. The copper foil feeds way down into the hole for the cross tie so that when the cross tie pushes in it makes good contact. I filed the top edge flat across like a waterfall where it first goes into the cross tie hole.

3) Made frame into Faraday cage. I have no real proof that this mod helps and it took a few hours of work to do. I'm using it as a test bed to find ways to reduce ESD. I would not recommend others to re-create it. I in fact have already removed parts of it since the copper is thin and gets damaged easily when changing things.

4) Boom stop mod to keep it from hitting the belt

5) Metal cross ties in the boom block

6) Metal main bearing holders

Finally, I did ChasHeliCops canopy mod to make adequate room up front for my battery and linkages. This mod is sweet. I’ve never had a canopy fit more perfect.

ChasHeliCops thread:

Many ask about the wire braid. I put sleaving on all my wires to protect them from rubbing on edges and to hide any splicing. I take off the connectors using the tip of an exacto knife blade to release the catch on each one.

I used flexo clean-cut that I bought years ago:

Many use this:

You put the sleaving on first. I used 1/8" and 1/4" depending on how many wires I was running. It can be bunched up to make the inside diameter increase so that you can easily slide wires through it. Bunch it like an accordian and keep sliding the wire through. Slip some heat shrink over the ends after ward. Put the connectors back on then shrink the tubing. I bought an assortment of heat shrink sizes from Home Depot and used the size that was just bigger than the sheathing.

If you have to lengthen a run, you can buy servo wire extensions and then cut off the socket end and splice in the new wires. Put shrink around the individual wires to isolate them. You can shorten runs by cutting off the connectors then replacing with new ones.

There are kits available to put on new connectors.
I use this one:

I opted not to do the following mods:
1) Ground the motor mount to the ESC or battery negative. I prefer to leave my electronics floating with respect to the frame. I will ground it via a resistor or fuse if I later find I have problems.
Warning: Do not ground your frame or motor mount to the negative of the battery or the ESC without using something to limit current in case a short occurs.

2) Rollers to keep the belt from hitting the boom. I like this mod but I won’t do this unless driven to it. My 450 and 600 belts rub slightly too and I’ve never had a problem with them.
Docjoe's mod:
Jetleaf's mod:

Things to be aware of when building:
1) Had to dremel some plastic away on the plastic bottom in front of the motor on one side to get the frame to lay flat
2) Set screws in the skids leave ugly thread marks in the white plastic
3) Boom needed to be shortened (may have been from the metal tail)
4) ESD problem and associated mods
5) Tail rudder linkage had binding till I filed it a bit.

6) Was difficult to get Spartan in programming mode because I had to plug in the Deans then quickly start toggling switches. I would prefer they give you an extra second or so. Spartan was simple to set up once I got it into setup mode.

As usual, Bob’s vids were invaluable. I found the Spartan vid particularly helpful. Thanks to all the many Helifreaks I borrowed ideas from and bounced ideas off of.
Bob's TREX 500 Build Link:
Bob's Spartan DS760 Setup Link

7) Some had had problems with the screws stripping out. Do yourself a favor and get the set of Align Drivers and you most likely will have no problem.

The other option is to replace the screws. Heres a good link:

Another great resource for ESD and build stuff by ChasHeliCop:

All in all, it turned out pretty nice. I can’t wait to get out and fly it. It seems to be an overall solid bird and the size seems perfect.

Hope you like it!


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Edit: Oct 4, 2008 Scorpion 1600KV Motor Upgrade:
I bought the Scorpion Motor and a Scorpion ESC back on father’s day when my family knew they wanted to get me heli stuff but didn't know what to buy. My stock Align motor squealed from the first day I powered it up. The squeal went away for a long time, but it had been intermittently doing it recently. I had been flying with it all season so I really don't feel bad about retiring it. Since I was going to the Heli Phenom, I figured it was as good a time as any to give the Scorpion a try.

I reused my 13T pinion since that seemed to be a good tradeoff between headspeed and flight time. I'm mostly a sport flyer anyhow (not by choice ).

The ESC connectors were different than the stock Align version so I had to solder new connectors on my ESC. I didn't put new connectors on the motor since I wanted to be compatible with the Scorpion ESC when its time to upgrade my ESC. Hopefully it will just plug right in.

The biggest changes were caused by the fact that the Scorpion is an out runner. Since the outside motor case spins, you can't locate wiring next to the motor or it will get chewed up. Strategically placed nyties solved this problem and overall the switch over went without a hitch. Here's some pics.

ESC Motor Lines to the right, and control line to the left. I ran the control line above the motor to keep with my philosophy of keeping the bottom plate easy to change in the event of a crash. The only wiring I have under the heli is my 72 MHz antennae.

Right Side showing routing of ESC control line over the top of the motor:

Left side showing nyties I used to assure the wires never migrate to the pinion or spinning motor casing area. Everything seemed to stay in place on its own but I used some nyties to be absolutely sure.

Closeup of the ESC Motor lines:

I took it outside under the spot lights and hovered a bit and it sounded perfect.
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Last edited by rdlohr; 04-27-2009 at 09:06 PM.. Reason: Added Scorpion Motor Upgrade
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