WARNING! The radio controlled model helicopter built from this kit is not a toy and is not meant for children. It is a flying machine capable of causing property damage and serious bodily harm to both the operator/assembler and/or spectator if not built and operated correctly and responsibly. Rotating components, especially the main rotor blades, are an everpresent danger. Model helicopters operate differently than model cars and airplanes.
Construction Manual Acknowledgments Bergen R/C Helicopters wishes to thank our friends and customers for their continuing support during the development of the Intrepid Helicopter. The Instruction Manual and illustrations were completed with the input of numerous customers and staff. We wish to recognize Gary Wright, who had been the test pilot and helicopter guru in its early years. We would also like to recognize Mike DeMetz for his continuous support and knowledge in electronics and maintenance.
Introduction The first of its kind, interchangeable modular engineered helicopter to accommodate the beginner to a FAI expert… An idea in 1994 to manufacture an interchangeable, modular helicopter, led to the research and development in 1995. Focusing on quality, engineering details, and price, a prototype was produced. After extensive test flights and fine-tuning, the INTREPID HELICOPTER is now what you see today. The first of its kind, strength combined with simplicity for easy maintenance and flying.
Consumer Warranty IMPORTANT! Before building the Observer EB Helicopter kit, read and fully understand the following warranty, and review the entire Construction Manual. By building and/or flying this helicopter you indicate your acceptance of the following warranty terms and conditions, and further agree to build and operate this helicopter in safe and responsible manner.
1. Not withstanding the paragraph above, this warranty is in addition to whatever implied warranties may be granted to the Purchaser by law. To the extent permitted by law, all implied warranties, including the warranties of merchantability and fitness for a particular purpose are limited to a period of (1) year from the date of purchase. Some states do not allow limitations on how long an implied warranty last, so the above limitation may not apply. 2.
Congratulations on your purchase of a Bergen R/C Helicopters Observer EB. The EB stands for Extended Boom, allowing the use of 810 mm rotor blades. There are a few things we recommend in the assembly and use of your Observer EB, and we’ll spell those out as we go, but for now, our first recommendation is a good quality set of hardened allen drivers.
Start with the landing gear. Assemble the skids and cross bars as shown, leaving them loose for now. Locate the landing gear skid bars in bag #1, use them to locate and drill 2 holes in each cross bar. Center the skid bar fore and aft, as well as side to side, and use a #30 or 1/8th drill bit to drill through the cross bar. Set the landing gear aside for now. Gather all of the engine components. Note the tapered end of the crankshaft. Also notice the sharp edge at the end of the taper.
Install the pull start using 4 ea 4X12 SHCS. Again, loctite isn’t needed, however if you feel the need, you can use a drop of CA glue in place of loctite. Note the orientation of the pull start handle, on the same side as the carburetor insulator block. On the opposite end of the engine, install the fan shroud mount plate, using 4 ea 5X12 SHCS and loctite this time. Also note the orientation of the plate; this will be important when you mount the fan shroud.
Tap the high side down carefully, using a small hammer, hitting flat on the tops of the fan blades, then checking the runout. It usually takes only a sharp tap to bring it in. Now torque down on the bolt holding the fan to the engine. Check the runout again. If it has runout, give it another tap on the high side and recheck. You should be able to get the runout to less than .002 without a lot of difficulty. If you are having difficulty, remove the fan. Check the runout of the crankshaft itself.
When you get all 4 SHCS installed, warm the entire shroud to relieve any stress that could cause cracks in the future. Install 4 ea 3M locknuts on the SHCS. DO NOT over torque these nuts; you will crack the ears on the first run of the engine. Snug is good enough. Gather the lower frame components from bag #1. Start with the “butterfly” and the 2 “Front Frame Plate Bars”, noting the orientation.
Install the rear bulkhead using 4 ea 3X16 SHCS and 3M locknuts, then install the landing gear skid bars, front and rear, using 4 ea 3X8 FHCS. Assemble the rear battery tray with battery tray spacers, using 6 ea 3X8 FHCS and loctite. Install the battery tray into the frames using 4 ea 3X8 SHCS and loctite. Note the tray spacers are on top. Install the “Front Frame Block and Arm Mount” on the rear of the butterfly, using 4 ea 3X16 SHCS and 3M locknuts.
Install the lower frame assembly onto the landing gear, using 4 ea 3X16 SHCS and 3M locknuts. Center and rotate the skid tubes to your liking, then drill a #50 pilot hole in the boss, into the aluminum skid tube, on the underside of the gear and install the 2 ea 3X8 self tapping screws. I typically install these into the rear cross bar, leaving the front crossbar able to flex. Install the engine into the lower frames, spark plug facing to the rear (remove the plug for ease of installation).
Locate the delrin bushings, steel inserts and 4X16 SHCS. Note the chamfer on the steel insert. Install with the chamfer toward the head of the bolt. Install the delrin bushings onto the fan hub using loctite, and tighten securely. Assemble the clutch components, clutch, clutch bell, triple bearing block, and retaining collar w/3X3 setscrews. Use loctite on the setscrews in the retaining collar. Install the clutch system onto the delrin bushings on the fan hub.
Press the flanged bearings into the upper frames, making certain to seat the flange down. Be sure to make a right and a left, with the flange on the inside of the frames. Put a drop of CA glue around the outer edge of the bearings to secure them in place, being careful not to get any glue in the bearing itself. Insert the axles into one side frame and slide the opposite side frame onto the axles.
Insert the elevator yoke into the upper frames, with the longer of shaft on the right side of the helicopter. Find the 2 main shaft bearing blocks. Note the cutout portion on the lower bearing block. Install the lower main shaft bearing block, using 2 ea 3X35 SHCS, note the orientation of the bearing, facing up. The elevator yoke is removed for clarity. Install the upper main shaft bearing block, using 4 ea 3X8 SHCS also note the orientation of the bearing, facing down this time, hump side up.
Secure the cross pin with a 3X4 setscrew threaded into the rear of the shaft, using loctite. Make doubly sure the setscrew secures the crosspin. Insert the shaft into the rear of the transmission cradle through the bearing, and slide the brass tube onto the shaft. Install the tail pinion onto the shaft and slide the shaft all the way in, through the forward bearing. Looking through the setscrew hole, locate the divot in the shaft. If it doesn’t line up, look through the second hole in the pinion.
Install the autorotation hub into the main gear with the longer portion of the hub facing up. Use 4 ea 3X8 Low Head Cap Screws and loctite to secure. Insert the main shaft down through the upper bearing block, install the 3 pieces of the thrust bearing and 1 split collar on the shaft with the “ring” facing up toward the bearing, slide the shaft down a little farther and install the second split collar, below the elevator yoke, with the “ring” facing down toward the bottom bearing.
Gather the 26 mm threaded frame spacers and 29 mm non-threaded frames spacers with 4 ea 3X40 SHCS. Secure the rear of the frame sets together by inserting the bolt through the frames and spacer, into the threaded spacer in the middle. Install remaining bolts and frame spacers. Now go back, and one at a time, remove a bolt, loctite and reinstall. Loosely install 4 ea 3X8 SHCS and 3M washers into the triple bearing block.
Set the tail gear pinion mesh by loosening the thru bolt holding the lower main shaft bearing block and transmission cage in place, and loosening the 4 bolts at the rear of the transmission cage. Tap down on the front of the cage at the point shown until you get a smooth running mesh with little or no backlash. The “step” of the ears on the transmission will sit flush with the top of the bearing block. Now tighten the thru bolt, loctite and tighten the 4 bolts in the rear of the transmission cage.
The swashplate is next; install 4 ea medium balls on the inner ring, using loctite. After installing these balls, make sure the eyeball in the center of the swashplate moves freely. If not, check that the threads of the balls haven’t gone in too deep, pushing on the eyeball. Remove some of the threaded end, if necessary. 4 ea short balls go in the outer ring, with loctite. Slide the swashplate onto the main shaft and snap the links from the elevator yoke onto 2 of the outer balls.
Insert the 3X7X3 flanged bearings into the arms, 2 ea into each arm. Insert the 3X16 SHCS with 6M shoulder through the bearings and put 1 ea 3M brass washer on the bolt. Note the orientation. Thread the bolt into the washout hub, then install a 3X4 setscrew in the same hole from the opposite side. Set the tension on the bearings by tightening the bolt carefully until the arm spins freely, but there is no side to side slop. Tighten the setscrew, using it as a jamnut to secure the bolt.
Assemble the control system; starting with the collective arms (popsickle sticks), aileron bellcranks, and “X” arm. Install the short balls in all of the pieces, using loctite, making a right and left aileron bellcrank as shown. Install the 5X8X2.5 flanged bearings into the pieces, putting 1 ea into the popsickle sticks, and 2 ea into each bellcrank.
Install the left side popsickle stick, matching the broach in the popsickle stick to the flats on the collective axle, using a 3X4 SHCS and 3M washer at the front into the shaft for the elevator yoke, and a 3X8 SHCS and 3M washer into the collective axle. The right side popsickle stick is installed the same way, except, The “X” arm bolt threads into the collective axle, setting the tension on the bearings by holding the jamnut, then tightening to the popsickle stick.
Install the triple bellcrank on the left side, on the collective axle, matching the broach with the flats on the axle. The single bellcrank is installed on the right side, on the collective axle. Use 2 ea 3X8 SHCS with 3M washers and loctite. Note that the legs with the short balls on both bellcranks should point in the same direction, as shown, both are pointing down. Assemble the rotor head next, starting with the seesaw. Press 2 ea 4X10X4 bearings into the end of the seesaw tube until flush.
When both bearings are installed, center the seesaw tube by tapping on the head of the bolts. The seesaw tube should pivot freely. Install the seesaw tube endcaps, pushing them on until flush with the end, and securing with a 3X4 setscrew and loctite, in the inner hole. The setscrew should engage the slot on the tube. Also install the short balls in the outermost hole at this time. Install 2 ea 3X5 panhead screws to secure the bearings in the headblock, being careful not to get any loctite in the bearings.
You may need to use the blade grips to push the circlips into place, just make sure they are seated all the way around. Now slide the blade grips onto the head axle, all the way to the circlip. Locate your thrust bearings for the blade grips. Notice that one of the races has a larger inner diameter than the other. Grease the ball cage, then install the larger ID race inside the blade grip, on the head axle, with the groove facing out. Now install the ball cage with the open side of the cage facing in.
With both blade grips installed, use 2 allen wrenches to tighten the blade grip bolts. Tighten securely, but there is no need to overtorque them. Loosely install 2 ea 3X25 SHCS into lower boss of the head. These are the “pinch” bolts. Install the Head Button, if optioned, using 2 ea 3X12 SHCS and loctite. Assemble the pitch arm components next. Insert 2 ea 3X7X3 flanged bearings into each bell hiller mixer, then insert a 3X12 SHCS with 6M shoulder and place a 3M brass washer on the threads.
Install 2 ea short balls on the mixers. Note that one end of the arm is longer than the other, and orientation of the balls. In this instance the longer end is to the right. Install the assembly onto each blade grip using 2 ea 3X6 SHCS and loctite. The milled flat on the pitch arm should square up the pitch arm to the blade grip. Slide the head assembly onto the main shaft, lining up the “jesus” bolt hole with the hole in the mainshaft. Slide the pins from the washout unit up into the slots in the head.
Flybar installation is next. Insert the flybar through the seesaw tube bearings; install a 4mm special washer on each side, then the flybar arms. Center the flybar, measuring both sides from the flybar arm to the end, with the flybar arm pushed all the way to the seesaw tube. Secure the flybar arms with a 3X4 setscrew and loctite, making sure the flybar arms are parallel with each other.
Install the fuel tank, starting with locating where the fuel fittings will be installed in the tank. Slide the tank under the battery tray and mark where you want the fittings. Drill a #16 hole in the tank at the spots marked. Install a single end fitting on the top of the tank for the vent line, and one on the side for the return line.
Install the tank under the rear tray and secure with the 2 long tye-wraps provided, running the tye-wraps through slots in the tray. On the carburetor you will find an idle adjustment screw, remove it and throw it away. Install the throttle arm on the carb, in the direction shown. With the carburetor butterfly halfway open, you want the throttle arm pointing straight away from the carb. The idea here is to center the throw of the arm for setup purposes.
Snap the air filter cover in place and secure with the slide on the bottom. Now install the fuel lines from the tank to the carb. The fitting at the front of the carb is the fuel in fitting; the rear fitting is the return line to the tank. Don’t forget the vent line hanging straight down past the landing gear cross bar. You may want to secure these lines with tye wraps around the fittings, as you did with the clunk line inside the tank. Install the muffler next.
Begin assembling the camera mount by installing the Front Frame Block and Arm Mounts to the “flying squirrel”, noting the orientation, with 8 ea 3X16 SHCS and 3M locknuts. Don’t tighten these just yet. Place an extension arm on one side, and install 4 ea 3X35 SHCS through the Front Frame Blocks, then place the opposite extension arm on the bolts and thread 4 ea 3M locknuts on the bolts. Now tighten all the bolts, pulling the extension arms up to the “flying squirrel” tightly.
Install 1 ea thrust bearing block w/4 ea 3X8 SHCS and 1 ea standard bearing block w/2ea 3X35 SHCS and 2 ea 3M locknuts onto the front end of the extension arms. Note the orientation of the blocks and bearings. The thrust bearing block is installed on the bottom, with the hump down. Leave the bolts loose for now. Through one turret arm, install 12 ea 3X35 SHCS and place flat on the table.
Locate the three round spacers and place on the three shafts; the lower ones go on the inside of the blocks, the upper one sits on top of the upper G10 block. Install the height adjustment arms onto the shafts, putting a 3X30 SHCS through the arm and the hole in the shaft, securing with a 3M locknut. The three different holes allow for height adjustment when using different sized cameras. Install the base plate in between the arms securing with 4 ea 3X20 FHCS and 3M locknuts.
Push the assembly all the way up, push the split collar down on top of the thrust bearing and tighten the split collar bolt, NO loctite. The camera mount should spin freely. Install a large pulley onto the shaft, installing a 3X20 thru bolt and 3M locknut. You may need to tap up on the whole assembly to get the holes to line up, then carefully tap it back down. Now tighten the bolts securing the bearing blocks to the extension arms.
Install the small pulley/servo wheel onto the servo, then place one of the servo assemblies in between the extension arms, angling it in while installing the pulley belt. Push the servo mount in until the thru holes line up and install 2 ea 3x35 SHCS, 4 ea 3M washers, and 2 ea 3m locknuts. Set the tension on the belt fairly tight and tighten the nuts. Repeat for the tilt servo on the side of the turret arm.
To get the full 360 degree rotation with out winding up the servo wires, try this little tip. With a 12” long servo extension wire, remove the male plug by lifting the tabs and pulling the connectors out. Remove the 2 thru bolts in the long vertical shaft, one in the pulley and one in the turret arm. Feed the wire without the plug up through the shaft. Reinstall the plug on the wires and carefully reinstall the bolts through the shaft without cutting the wire.
Begin assembly of the tail system with the “dogbone”. Insert the crosspin and secure with a 3X4 setscrew from inside the dogbone with loctite. Locate 2 ea arrow shafts, they are aluminum, and you will see a silver dot on each end. Cut 1” off of each end of both arrow shafts. This is to remove the part of the arrow shaft that is not machined to the proper size. Now cut 1 arrow shaft 16 ¼ “ long, the other 17” long.
Install the “dogbone” assembly in the front end of the short arrow shaft, again with a collar and only 1 ea 3X3 setscrew to secure. Using a #50 drill bit, pick one hole in each collar and carefully drill through the arrow shaft into the underlying shaft or dogbone, creating a divot in the shaft. With loctite, install a 3X3 setscrew in each drilled location. Remove, loctite, and reinstall the rest of the setscrews in each collar. The completed assembly is quite long and fragile at this point, be careful.
Assemble the tail pitch bellcrank by installing a 3X7X3 flanged bearing in one side, the aluminum spacer, Then the opposite bearing. Insert the 3X16 with 6M shoulder SHCS through the bearings and spacer, with the delrin cup on top, and add a 3M brass washer on to the bolt as a spacer. Thread this into the pitch arm on the gearbox, but do not tighten yet. Thread a 3M locknut onto the bolt and set the tension on the bearings by tightening the bolt, then tightening the nut to secure.
Slide the pitch slider onto the shaft engaging the ball into the delrin cup at the same time. Locate the Heavy Duty tail hub and 1 ea 3X4 setscrew. Note the divot on the output shaft. Install the hub onto the shaft lining up the hole in the hub with the divot in the shaft, secure with the 3X4 setscrew and loctite. Only 1 setscrew is required and suggested. Tail blade grips are next, note the radial bearings are preinstalled, and order of installation of the thrust bearings.
Locate the 4M shoulder bolts and eyelets. Slip the eyelet onto the shoulder bolt and install on the blade grip with loctite, being careful not to get loctite into the eyelet. It has to rotate on the shoulder bolt to operate properly. If you run into tail problems, drift, hot servo, tail wont hold, look here as a possible culprit. You should also lubricate this joint daily with a light lubricant such as 3 in 1 oil. On the 2 “Special Ball Links” you will note a rib down the side.
These pictures show installation of V-Blades tail blades as an option. Others may be used and install the same way. Just make sure they are balanced, and should be no longer than 110mm, the minimum is 95mm. Your kit may come with plastic white tail blades. Use a spacer on each side of the tail blades, inserting into the blade grip, then installing the tail special bolt with 3M locknut. Again note the direction of rotation.
Install the Horizontal Fin using 2 ea 3X8 SHCS with a drop of CA glue in place of loctite. Your fins may be solid or have lightening holes in them. The vertical fin is mounted using 2 sets of boom clamps and 4 ea 3X35 SHCS inserted into the fin, then 1 half of the clamp over the bolts. Place the fin and clamps onto the boom with the rear clamp up against the gearbox. Install the other clamp half and secure with 4 ea 3M locknuts, making sure the fin is vertical to the gearbox.
The tail servo mount is installed between the vertical and horizontal fins using 2 sets of boom clamps, and 4 ea 3X30 SHCS and 4 ea 3M locknuts. It’s position will be adjusted after installing the servo. The push rod can be installed also, but will need to be adjusted later as well. Use the 140mm pushrod. Install the boom assembly into the boom clamps at the rear of the frames, pushing it all the way in to engage the dogbone into the delrin cup.
The pushrods are made up of 2.5mm SS rods with threads rolled onto them and the famed Rocket City Links threaded onto the rods. There are a lot of rods and a lot of links. Most rods are in pairs. Start with these and find the most logical fit for the pushrods. Start with the collective pushrods from the single and triple bellcranks to the collective arms (popsickle sticks), these pushrods are 78 mm from center of hole to center of hole using the 50 mm long pushrods.
The pushrod from the swashplate to the bell-hiller mixer is 98 mm from center to center, using the 75 mm long pushrods. DS 811 servos used for picture taking only. We DO NOT recommend them for use in your Observer EB. Begin installing servos, starting with the throttle servo. Snap the plastic servo mounts into the slots in the frames and install the servo, spline to the front. Secure the servos with screws provided with JR servos, or if using Futaba servos, use 2.5X10 SHCS and 2.5M washers.
The collective servo is installed between the frames, with the spline to the rear. The aileron servo is installed on the mount between the collective arms, spline to the rear. Install tail rotor servo into rear mount plate with spline forward. The following is the setup we use for JR radio systems. Futaba users can copy the hole pattern from a JR wheel after centering the servos and wheels, marking the center or straight up point on the wheel.
When you have each wheel marked, put a ball on a 2X10 Phillips screw, thread a 2M nut up to the ball, then screw the assembly into the wheel at the marked hole. Thread another 2M nut on the backside of the wheel securing with loctite. Repeat for all the other wheels, with the throttle and tail servo wheel only using 1 ball on each. Turn on the radio system again, making sure each servo is centered and reinstall the servo wheels onto the servos.
Collective servo wheel is installed with the offset to the rear; pushrods are 50 mm long, center to center using 30mm long pushrods. The throttle servo wheel just uses one ball and pushrod, but still needs to be centered, with ball at the top. Throttle pushrod is 173 mm long center to center using the 140 mm long pushrod. With the servo centered, the throttle arm should also be centered with the carb at half throttle. Setting up the throttle requires some math☺.
Install Gyro on the mounting plate, preferably with the green Zeal anti vibration gel, and connect to servo and receiver. Use a long servo extension wire to connect the servo to the Gyro, securing the connections with tape or heatshrink. Install the on-off switch for the heli in this location. You’ll notice 2 slots for the switches in the case of the Dual Redundant Battery system available from Bergen R/C or ElectroDynamics.
The radio setup numbers for JR radio is as follows; Futaba radios will be similar but may require slight changes. The tail setup procedure is suggested using a GY401 gyro and 9254 servo. ATV’s or travel limits; Aileron 115% Elevator 85% Collective 100% Rudder 90% Gyro Gain HH 90% Gyro Gain non-HH 80% Throttle as described previously. Rudder ATV set’s the pirouette rate, not servo throw. Ensure that all servo directions are correct, especially the gyro and tail servo.
To static track the tail blades, try this. Fold both blades up against the blade grips. Push one blade in until it touches the bolt for the vertical fin mount. Without changing the pitch, carefully rotate the tail system until the opposite blade comes close to the same bolt. Adjust the length of one special ballink until both blades touch the bolt when rotated. Now check your travel limits again to see if adjustments are needed.
Install the NHP 800 MM Blades, first inserting the brass bushing into the root. Put a plastic spacer on each side of the blade root and slide the assembly into the blade grip. Note direction of rotation, in this case, clockwise as viewed from above the rotors. Install a 4X25 SHCS w/shoulder through the assembly and secure with a 4M locknut. Tighten the blade bolts enough that the blades will not fold when the heli is turned on its side and shaken.
With the pushrod lengths given earlier you should be close to a 0 degree pitch at half stick, -6 or so at bottom stick and +11 or +12 at full stick. If you prefer to hover at half stick, adjust the pitch curve in the radio to get the setup that you prefer. As an option, we offer a velocity stack for your carb, doing away with the somewhat restricting air filter. If you are flying in a dusty area, we do not recommend this.
You can install Pool Noodles on the landing gear as a visual aid; you may need to divert the exhaust as shown to prevent melting the foam. Install the Pan and Tilt receiver in between the framework at the top, with padding, and secure with tyewraps or Velcro. The battery pack is secured lower down in the frames, again with padding and tyewraps or Velcro. Your downlink system can be attached under the camera plate, with battery pack strapped to the side.
Slowly spool up the blades, checking the tracking. Adjust as necessary by adjusting the length of the pushrod from the swashplate to the bell mixer. Hover RPM should be between 1450 to 1650 depending on payload, local conditions, and altitude. Adjust the RPM, using the throttle and pitch curves, to obtain the smoothest possible platform for your camera.
