Build Thread - Helibug Core 7 - Discontinued - See final post

[carey shurley]

Welcome to my build thread for the Helibug Core 7 gasoline conversion

first off what is a Core 7?

Its a gasoline conversion for an Align TRex 700 model. This is the second 700 conversion offered by Helibug and is named for being a more "hard core" gasoline model.

Its typical in that the kit provides frame and certain drive train components and uses the rotor/control components from a std Trex kit.

This one is a little different in few ways:

• the overall chassis layout is more like the 600 conversion
• this uses the std Zenoah clutch shoe system. A common complaint for the original 700 conversion was that under heavy flight loading the drive clutch could slip. To my knowledge this is the first commercial use of this clutch system in a model helicopter. I am sure there are folks who have made custom versions for the clutch but not something that is mass produced. As you'll see this thing is quite large.
• This is the first Helibug conversion that cannot be spin started. It can only be pull started. The stock zenoah clutch design does not support a support shaft that can be used for this.
• it uses a different gear ratio than the original 700 conversion. It was available in 5.75:1 and 6.76:1. This model is only available in a 6.76:1 and 7.18:1 ratios which are more appropriate for high performance/high rpm motors.
• it requires the fewest number of donor parts from an original model to complete

Okay time to get started:

[carey shurley]

So you need a donor kit, a Trex 700N

The first two photos show the parts you need from the original kit


You need the complete rotor head, tail boom and landing gear

the model I'm converting was configured as an FAI version of the 700. You'll see many of the mixer, t/r control and fin parts from the FAI 700


You also need the canopy, main drive components and the complete control system

This requires a different main gear so you don't need the original


Here's what comes in the conversion kit. Frames, engine mount, cooling deflector, pinion and bolts


You MUST have these parts to complete the model

• Align Trex 700 Front Frame Mount (HN7084) - 1 pack
• Align Trex 700 Flange Bearings (HN7067) - 1 pack
• Align Trex 700 Aluminum Hexagonal Bolts (HN7048) - 1 pack
• Align Trex 700 Main Shaft Bearing Block from 700E (H70045) - 2 packs
• Align CNC Main Drive Gear/115T (HN7019BT)
• Zenoah clutch kit - Daves Motors #GT280
• Clutch Bell - Daves Motors #86490

Here are some optional parts that I've used in this build

• Align Metal Elevator Servo Mount (HN7074MT)
• Sullivan Aluminum Fuel Stopper #478
• Miniature Aircraft Fuel fittings (1 each 0410-90, 3 each 0405) or equivalent
• Walbro/Zenoah Fuel Pickup #125-527-1
• Stens/Echo One Way Valve #610-079
• Stator Gator #GGS233-RC
• Servo Nuts (2 required) for pitch/aileron servos
• RC Booya 7ECM TRex 700 Extreme Canopy Mounts

The TRM VX231RS Motor

The kit requires a RC format motor. Either Zenoah or CY versions can be used.
23cc, 26cc or 29cc versions can be used in stock or modified versions
this build will use the TRM VX231RS motor which is ported for a 7.18 gear ratio



You'll need a muffler

You'll want a muffler, the can muffler on the left is usually included with the motor. It is very loud but will work. I have personally run the other two mufflers. They are:

• left = zenoah can muffler
• top = Hatori 956 (the SB12R is the same as the 957 which is a more mid mount)
• bottom = Zimmerman 2653 s/s

[carey shurley]

First build the central chassis

As with all helibug conversions, you have to install the elevator bellcrank bearings into the frame


Elevator Bellcrank Bearings Installed

in the early kits, these bearings were a loose fit and had to be glued into place. That tolerance has been resolved so now you actually have to trim the holes slightly and press the bearings in.

Next install the bearing blocks. The main shaft blocks are as the original model. The clutch bell blocks are installed so that the "open" side of the block face the top and bottom as shown


Clutch bell top bearing block


Clutch bell bottom bearing block

also install three of the frame spacers into the positions shown.


Align bearing blocks

The clutch bell cannot be installed until the frames are mated however before you fully tighten the main shaft and clutch bearing blocks, temporarily insert the mainshaft and clutch bell into their respective blocks to ensure everything is aligned. Then you can fully tighten the bolts that hold these blocks.


Bearing Blocks/Spacers Installed

the left side frame is ready to be mated with the right frame


Right Frame in position

the right frame fits as shown and the standard 3mm shoulder bolts attach the bearing blocks


Canopy Bumpers/Bellcranks Installed

the top canopy bumpers and spacer are installed along with the aileron and pitch bellcranks

Because this kit doesn't use the stock clutch bell, if you want to use a magnetic governor sensor you're going to have to fashion a way to mount the trigger magnet somewhere. If you intend to use the clutch bell to do that then you'll need to make those modifications now and glue the magnet(s) in place.


Clutch Bell components

these are the parts that make up the clutch bell. At this point the bearing blocks are already installed in the frame.


Position Clutch Bell shaft into bearings

slide the clutch bell shaft into the clutch bell bearings as shown. Note the shape on the end of the clutch shaft


Pinion gear slotted for clutch bell shaft

The pinion gear has a matching notch which will engage the clutch shaft end inside the upper bell bearing


Pinion is retained by s/s bolt into clutch shaft

This s/s bolt connects the pinion gear and clutch bell


Installing pinion

use a medium/green grade of thread lock on the bolt and install it through the pinion into the clutch bell shaft. This bolt CANNOT be fully tightened or it will bind the bell bearings. Tighten the bolt only until it is snug. The thread lock will keep it in place.


Clutch bell assembled

Here's the finished clutch bell assembly. Compared to the clutches we are used to this thing is HUGE!


Replace main gear and reassemble main drive

Install the 115 tooth main gear on the main gear drive assembly and then reinstall the t/r drive gear as shown


Reinstall main shaft/drive gear

Reinstall the mainshaft and main drive gear. Make sure you use the appropriate spacing shim to ensure that the bearing stack is not side loaded.

in the next thread the control system will be installed.

[carey shurley]

So now that the basic chassis is done its the easiest time to install the electronics and control system.

you'll need two servo nuts for the throttle servo, install it in this direction. You'll have to resize the throttle rod, more on that later


Install the throttle servo first

go ahead and install the radio tray assembly now


Install the radio tray using shoulder bolts and the front canopy mounts

this installs just as it does on the nitro model


Install and connect the pitch servo, only one servo nut required

the pitch servo installs in the same way as on the nitro model. Unfortunately the servo position is slightly different so you'll have to resize the control rods


Install and connect the aileron servo. Only one servo nut required for this as well

the aileron servo also installs in the same way as on the nitro model. Unfortunately the servo position is slightly different so you'll have to resize the control rods


Install and connect the elevator servo

the elevator servo also goes in the standard position. you will have to resize the elevator control pushrods


Install the flight pack switch. Can be installed on either side.

The frames contain cutouts to mount the electronics on/off switch. The switch can be mounted on either side, I mounted it on the right frame side because its the side I've always mounted the switch on my models.

Next thread will cover engine prep and installation

[carey shurley]

okay now lets get the motor ready

if you're going to use a stator gator sensor, you might as well install the pickup in the motor now.

The RC format motor uses a high output fan and the cylinder is well shrouded. However the output air comes out of the cooling shroud at about a 45 degree angle. This can hit the inside of the frames and wind up in the canopy making the electronics hot. So to address this the conversion includes a deflector to better channel the air out of the frames.


Engine Deflector Position

here's how the deflector will be positioned in the cooling shroud


Deflector Installed

and here's how it looks when its installed


Engine Mount assembled

The engine mount is comprised of 4 parts. Because of access once its on the engine, the mount needs to be assembled and aligned before its put on the motor.


Align engine mount

Temporarily install the assembled mount into the frames using the shoulder bolts to properly align it and then fully tighten the bolts that hold the cross mounts in position


Engine mount installed on motor

now you can install the full aligned mount onto the motor


Clutch back plate installed

Install the clutch back plate onto the motor and tighten down the mount bolt


Clutch assembled and installed on back plate

Then you can assemble the clutch shoes on the back plate. This uses two bolts and 4 washers. The washers can only be installed in one order


Motor Installed

slide the assembled motor/mount into the frame and use the shoulder bolts to position and fasten it into place.

Next - install the landing gear

[carey shurley]

Now that the motor is installed, the bottom frame plate and landing gear can be installed


Install Landing gear blocks

install the two landing gear blocks into the lower part of the frame using shoulder bolts


Remove shroud bolts

now remove the 4 bolts that hold the shroud onto the back of the motor. they will be used in the next step


Install bottom frame plate

position the bottom frame plate as shown and use the previously removed 4 bolts to hold it in place. Don't tighten them yet.


Install landing gear

now install the landing gear as shown and fully tighten the bolts. Now you can finish tightening the 4 bolts that attach the bottom plate to the motor


Align pull start

The model can only be started with the pull starter. You have the option of pull starting from either side of the model. So align the pull started so that it faces the side of the model you want to start it from. I typically use the left side of the model so I have easy access to the carburetor/fuel lines


Motor installed

Here's the finished assembly

Next - finishing up the chassis

[carey shurley]

The chassis is almost complete, just a few more steps


Stator Gator Sensor placement

I usually mount the stator gator sensor on the side of the frame. If you intend to use another type of sensor you will have to fashion your own bracket. Since this model uses a different clutch it does not include a place to mount a magnet in it.


Install muffler

Install your choice of muffler now


Install Tail boom assembly

The complete tail boom assembly can now be bolted in. It mounts exactly as it did on the nitro model


Install complete rotor head

The complete rotor head can now be bolted on. It mounts exactly as it did on the nitro model.


Throttle control rod

The throttle rod can be installed. You will have to resize it from the nitro model


Rudder control rod installed

The rudder control rod can be installed. I found that the 700N rod was too long. I used the rudder control rod from the 600n. It fit almost perfectly.

Next - the last steps - the fuel system and the canopy and the model will be complete

[carey shurley]

Next is the fuel system

Right up front I'll say I'm not happy about the fuel tank on this model. If you've read my process for plumbing fuel tanks you'll see I have a very specific process thats guaranteed to work and be trouble free. Unfortunately because of the tank thats used here, the way it has to be installed and the amount of room in the canopy I haven't yet been able to use that process. However what is shown is what comes with the conversion. I will depict it as it should be built using those parts. It is very similar to what is used on a number of the other conversions which have been quite successful work fine.

The kit comes with a 10oz Dubro tank. Unless you are willing to modify the canopy you wont' have much choice but to use it.


Make sure you use the gasoline friendly stopper

First off make sure you replace the black glow fuel stopper with the brown gasoline resistant stopper included with the kit. The black one will eventually melt.

You can still use the walbro felt clunk with this tank. Use a 6" piece of neoprene and connect it to fuel inlet tube in the stopper


Use the Walbro felt clunk

If you've built a fuel powered model airplane, you've built a tank with this type of plumbing. The top two tubes need to be internally bent towards the top of the inside of the tank as they are need to be at the top of the fuel level when the model is upright. The bottom tube is typically the fuel inlet where the clunk attaches internally.


Tank internal plumbing done

Tighten the clunk screw to compress the stopper which will make the tank fuel tight.


Tank positioned for installation

this is the way the tank needs to be installed. Now for the next thing I don't like. In order to get this tank into the frames you'll need to slightly spread them and shove the tank in. It fits VERY TIGHT into these frames. I guess the good news is that you won't need any foam tape to hold the tank once its in there.


Tank final position

push the tank in until the stopper almost reaches the front frame support. Positioning should be as shown

wrap some velcro around the bottom of the radio tray and around the tank and tighten it securely. In the event the tank were to vibrate loose from the frames this will keep it from flopping around


Tank velcro strapping

So now you can finish plumbing.


Tank side plumbing

• Run a tube from the bottom fuel inlet to the inlet on the carburetor
• Run a tube from one of the top vents to the fuel return on the carburetor
• Attach the one way valve to the other tank vent

Carburetor side plumbing

here you can see where the fuel inlet and return connects to the carburetor


Canopy installed - model complete!

Finally the canopy is ready to install. It will fit properly without any modification if you use the stock 10oz tank and position it as shown.

At this point the conversion is complete and the model is ready to setup and fly.

[carey shurley]

I did put the initial flight on the model today.

my donor model was in fact a Helibug HB7-RC so practically all of the setup was already done and the motor is already broken in.

model lifted off and everything is working as expected. The clutch engages at about the same point that the Quick or Lynx clutches and much sooner than the stock clutch would.

i'll have more information and video in coming weeks.

[WillJames]

AWESOME Thread Carey!! Thank you for sharing, excellent detail.

[fastflyer20]

Thanks, very well done.
How much does it weigh?

[carey shurley]

about 12-1/2 lbs

[carey shurley]

Earlier in the build thread, I showed how the stock fuel tank is supposed to mount and be plumbed. I also indicated I wasn't happy with how it works. Its only 10oz, it doesn't fit well into the frames and can only easily be plumbed one way.

So now here's my option. I have a simple way to plumb tanks, I do them all the same way as I posted here:
Fuel Tank Plumbing - My Way

Here's how to apply that setup on this model:

First turn the tank 90 degrees, or on its side. Doesn't matter which side. Drill it to put the optional connectors in as shown. Use foam tape and velcro to secure it. Its going to have to mount slightly further forward than with the original setup. This will require canopy mods - see those in a minute.


Fuel outlet locations

Here's the tank vent, fill and return connector


Fuel inlet location

Here's the fuel pickup


Required canopy mods

To make this work, here's how you have to mod the canopy


Here's the result

Here's how it turns out. You can see the fuel level and the best part is that now you can use a 10, 12, 14, 16oz or larger fuel tank

The Bottom Line:

This optional mount may or may not be something you like. It is effective however.

[dar61]

How is the zimmerman pipe? is that better than hatori?

Which one is the loudest between those 3 pipes?

Nice Thread anyway, keep updating

[carey shurley]

By FAR the stock can muffler is louder than just about anything else you can buy!

The zimmerman would be second and the Hatori is the quietest

I'm working on some testing between the stock can, Hatori, Zimmerman 2653, RJX and Century Torpedo for a specific set of high performance circumstances. When I'm done with that I'll publish a thread.

[jonB]

Need some guidance on the battery options for Trex-700-G core-7 build.

So far the electronics I have are 4xDS610s, BLS251, GY520, Rx JR790 SPCM (not 2.4G).
Should I use the Align regulator or CC or Western Digital or any other? I would like use the 6v circuit for all electronics, I heard BLS251 works fine with 6volts, everything else I have is rated for 6volts, except JR 790 receiver , dont know the voltage specs, cant find it anywhere.

I also fly Trex 450SE, so have bunch of 3S LIPOs ~2200mah, I would like to use these batteries for the 700-G, if possible.

Ideas?

[carey shurley]

the bls251 is not rated for use at 6v. other people may be doing it I'm just not aware of it. I run mine at 5.2v

I've been using Fromeco regulators lately without any failures, both the Arizona and Sahara. The Arizona is big but includes a step down. The sahara would requre an additional stepdown for the rudder like the Perfect Regulator setup. I've heard good things about the Perfect regulators but haven't run them.

I run 7.2 v setups with regulators on everything now.

[carey shurley]

So just talked to Ali at Helibug, due to strong customer feedback he's decided to discontinue this model and instead offer the h/d clutch upgrade for the existing HB7-RC 700 conversion thats been offered for a while.

He's offering a pretty nice replacement plan for Core-7 owners.

I'll leave this up for a bit but look for a new build thread for the HB7RC with the h/d clutch upgrade.