The Robbe Millennium II is an update version of the Millennium, which the legendary 3D pilot Bob Johnston help designed. The Millennium start off as a 3D helicopter for 50 class engines, but later due to marketing research Robbe changed the design to a 60 class engine machine. However, personally I think this change would be more due to the fact that when Robbe started design the Millennium, the Futura SE was still being flown by Curtis Youngblood, and they don't want the Millennium to cannibalize on the same market segment as the Futura SE, so Robbe made the Millennium a 50 size. Later when Curtis Youngblood switched from Robbe to JR the need for another "signature" line top grade helicopter becomes more eminent so Robbe made the Millennium a 60 class machine instead.
The Millennium featured some very unique design that caught my desire to get one. Of such are the very sleek outlook, the special drive train system, the Robbe patented 45 degree offset swashplate control system, and the placement of the tail servo.
According to promotional materials of Robbe, the differences between the Millennium and the new Millennium II are:
I ordered my Millennium from Bob Johnston's Skyline Models. Bob gave me a lot of very usual advice and very friendly services. As usual, I ordered some upgrade parts for my Millennium, they include:
Actually there are more option parts in my shopping list but Bob cross them out for me because he found that those parts did not work good with him. I would like to thank Bob for this cause being truthful to the customers should be the most important aspect of service as a shopkeeper in my opinion, and you've won my support, Bob.
Upon opening the box, the big yellow canopy caught my attention immediately. All bags were packaged in a way that when I arrived to a step of instruction I open one bag that is tagged with the step number in relation to the instruction and all parts and screws required for that step of assembly would be included inside the bag. Further investigation reveals that there was even one bag that had hex keys, glue, and lubricant included, which was not usual in other 60 class machine. The instructions were clear overall, with many diagrams and description on the side (In German, English and French) to explain each step. The packaging and instruction were unlike other non-Japanese helicopters that I have ever assembled (e.g. X-Cell and Vario), which were mostly words and few diagrams.
The Millennium main frame consists of two lower frames and one upper frame, and were joint together with the aluminum landing gear brace on the bottom, and with cross members on the top. The first part of the assembly dealt with assembly of the fuel tank and lower main frames. The fuel tank was like other non-Japanese helicopter, which requires drilling for outlet nipples and had a screw top cover on the back side for quick filling. Three holes had to be drilled on the tank and this completed without any hassles. The fuel tank was to be sandwich in between the rear portion of the lower main frame. Before fitting the fuel tank and the lower rear main frame I took advice as posted in Ron Lund's website (www.ronlund.com) to file the engine mounting slot one millimeter lower, and to round off the inside oval opening that holds the fuel tank. Also, since I used the optional carbon frames I took time to round off the side of all six pieces of frames and seal the sides off with thin CA glue. The lower rear main frame was held together by two pieces of S4820 plastic cross sections, which were placed as a "L" shape with the horizontal section double as a gyro mount base. The whole Millennium used a total of seven of these S4820 plastic cross sections, and an aluminum part S4820AL was available as an option. These aluminum cross sections were stronger than the stock plastic ones. I only order four pieces of these aluminum cross sections cause they were quite expensive (at US$25- a pop) and not all parts of the frame requires the additional strength of this aluminum part. I substituted one of the plastic part with the S4820AL aluminum part and was used in the vertical section of the "L". I opt to leave the horizontal part plastic for better vibration absorption as gyro mounting platform. I checked the alignment using an angle rule on a flat piece of marble, and secured the screws without using loctite until the whole mainframe was fully squared. The front main frame consisted of five S4820 cross section and a plastic servo bed sandwich between two pieces of frames. I used the remaining three S4820AL here.
The top main frame assembly was temporary held together by the four screws that holds the four "L" shaped bellcranks in place. Sandwich between the frames for the moment were the tail boom mount and one plastic cross section. Care must be taken when mounting the bellcranks onto the frames. On the place where each bellcrank should sit there were two holes placed vertically on each mounting position. To further confuse things, the instruction did not clearly show which hole each bellcrank should be mounted to. Further looking at the diagrams and some fiddling I found that there were very thin lines that link each bellcrank to their respective mounting hole on the diagram, and they should not be in-line to each other. After more fiddling, I found the bellcranks should be mounted like the following way:
Like my other helicopters, I used stainless steel screws to put the Millennium together. However, due to the Millennium's design, there were certain parts that used 3X70mm long hex screws to fasten parts together, and these type of screws were unavailable in stainless steel, so I had to use the stock black metal screws in these areas. I found that these stock long black hex screws were very high quality German made type. I also use gold colored screw supports to provide better strength on mounting.
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| Assembled fuel tank | Assembled lower rear frames |
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| Assembled lower front frames | Assembled upper frames |
The upper and lower mainframes were joint together using six 3X70 hex screws and six S4813 plastic cross members. I substitute the S4813 with optional S4844 aluminum cross members for more strength. The lower main shaft bearing block was now secured onto the frame. One good thing about the Millennium was that it came with German made FKG bearings, which were very high quality. I checked the alignment of the whole frame one last time placing the whole main frame on a marble platform using an angle rule, and secured the screws using loctite to fix the whole main frame.
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| Assembled main frame | Alignment checking on marble platform |
Next came the fitting of the main shaft, main gear and tail drive pinion onto the main frame. The main gear was made of molded carbon composite and was quite massive in diameter relative to other helicopters. In fact, only the main gear of my JR Ergo CCPM Racing, which came with a 128 tooth main gear, rivals the size of the Millennium main gear. I checked for warp on the main gear and there were none, which was quite surprising for a molded gear in such size. When I ordered the Millennium, I asked Bob if there was a machined gear available as an option, which Bob said there was none, asked me why should there be one. I told Bob about my worries about having a warp main gear and Bob assured me that the Millennium main gear would not come warped, and he was right. On the middle of the main gear sat an aluminum hub that housed a very beefy one way bearing. The one way bearing was not the usual roller type that was commonly found in other helicopters, but was more like a clutch style without moving parts. The size and mechanics of this one way bearing meant it could take a lot of abuse without failing. On the upper side of the hub connected a spur gear that drove the tail transmission pinion. The tail drive spur gear sat on the sleeve of a hub that was secured directly to the main shaft, and this made the tail constant driven during autorotation. This tail spur gear hub had three pre-drilled spaces to place magnet sensors for a speed governor. The instructions explicitly said to set the gear mesh between the tail pinion and the spur gear to be really tight and the tightness would go away after the first few flights. Unlike most helicopters, the collar that used to hold the main shaft in position was located on the underside of the top bearing block, not on the top, due to the fact that there was no bearing block right above the main gear.
Upon here, I would like to spend some time to talk about one of the attraction points for me buying the Millennium, being the main gear design. The Millennium comes standard with a 13 tooth pinion and a 120 tooth main gear, which arrive at a 9.23:1 gear ratio. While the gear ratio is nothing of fancy, the execution by Robbe to arrive to this gear ratio for the Millennium does require some discussion. While most other nitro burning helicopters (except gasoline powered ones) would use motor pinions and main gears with lesser tooth count to achieve a near gear ratio (The nearest would be JR Superio Katsuyuki, with 9 tooth pinion and 83 tooth main gear to arrive at a 9.22:1 ratio), Robbe opt to use gear that have more tooth to arrive at the same ratio. A main gear with more tooth, provide that the gear pitch are constant, means it will arrive in a bigger diameter. This poses several potential design and production problems for Robbe. One being a bigger main gear requires better tolerance on production cause it might get warped or unevenly balanced easily, and second to clamp a bigger main gear to the already compact main frame of our helicopter poses design troubles. Let's say Robbe calculated this gear ratio with "Super Computer" and arrive at this gear ratio which they think is the best, but Robbe could have use gears with lesser tooth count (smaller size) to achieve the same gear ratio, or to increase the tooth count but make the gear pitch more compact. Why does Robbe goes their way and use more tooth on the Millennium main gear, with gear pitch about the same as most other helicopters, to achieve the same gear ratio, which makes design and production a pain? I am not educated as a mechanic, so I do not have a very technical answer. However, my experience accumulated in my over twenty years in R/C cars does give me some hindsight to this. In cars, especially 1/12 and 1/10 on-road electric cars, where most cars could have zillions of gear combinations, I learned that even at the same gear ratio if the tooth count of one set of gears are more than the other, the one set that has more tooth count would generate more torque and less RPM for the rear wheel. Factoring this logic into the Millennium's main gear design, it means that the Millennium gear design would have more torque and less RPM for the rotor head. However, Robbe could have use a lower gear ratio to achieve the same effect, so why goes the hard route and use bigger gears? I hope someone could share some thoughts to this, and if you know please send a e-mail to me and I would post it here for everyone.
Technical factors aside from the use of bigger gear, the placement of the main gear in the main frame obviously serve a very good factor in the whole main frame design. Due to the massive main gear, the main shaft of the Millennium has to be placed more aft of the main frame, which shift the CG more aft. The Millennium's fuel tank is one of the few helicopters I saw so far with its fuel tank really below the main shaft with very little overhang (The other I know being the Kyosho Caliber series.), and this achieve the optimal CG for fuel tank position. While Curtis Youngblood, who always prefer helicopters with fuel tank on the front and off the main shaft, said the fuel tank position only affects the control feeling of the helicopter, me being a regular soul thinks that the fuel tank position affects a lot on the performance of a helicopter. The fuel tank is the only part in our helicopter that would constantly change its mass (Lower fuel level, lesser weight), placing the fuel tank at the CG point near the main shaft would lessen the affect of difference in fuel level to control difference during flight. A personal experience, when I fly my X-Cell Graphite SE, which has the fuel tank placed on the front off the main shaft, the fore/aft trim would change during flight with different fuel level. When the tank is full with my X-Cell Graphite SE, and I trim the fore/aft to neutral when the tank is full, after finishing half a tank the helicopter would behave tail heavy and I have to either trim it or use my fingers to adjust. If what Curtis said is right, then why in the first place should we balance the CG of our helicopter on the main shaft in the first place? Moreover, regular souls like myself constantly pays for things that would make the control feeling of my helicopter better, why should I buy a helicopter that would have control differences during one flight, and no matter what things I put in I could never cure the problem? Am I different, or is it just Curtis' control skill is too high beyond reach???
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| Main gear system, note massive main gear! | Assembled main frame with main gear |
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| Spur gear on top of main gear for driven tail | Close-up of drive train |
Anyway, back to the assembly. Next came the fitting of the swashplate, swashplate guide, the under guard and servo rockers. Except for the fitting of the swashplate guide that required trimming on the main frames to fit, other parts fit without any hassles. At this time, the instruction said to put on the landing gear, but I opted to leave it till later steps.
Next came the washout slider. The whole slider assembly consisted of two arms and one center hub, all made in plastic parts. All rotational points were bearing equipped, and even the swash links were installed with bearings to provide extra smooth operation. This slider featured special design where the fixing pins were planted onto the slider hub, rather than onto a separate washout fixer as with usual design. The pins would be running on a plastic guide that was fixed on the lower part of the rotor head, but this design made mechanical timing setting not possible. The center of the washout hub had a brass sleeve insert to provide smooth sliding of it on the main shaft, but the sleeve extended out of the washout hub. Later, I found that the extended part of the sleeve would hit the swashplate to prevent a pitch window greater than 18 degrees, so I used a file to take 3mm off the lower part of the sleeve to give a bigger pitch window without problem.
Assembly of the rotor head came next. The rotor head consisted of an aluminum hub, with the blade grips in plastic, and all rotational points with bearings. The head have the spindle shaft "float" on dampers located on both sides of the rotor hub to provide damping. The dampers were of new type that has two O-rings on each side, compared to the only one O-ring for each side with the original Millennium. During assembly of the rotor head, I put on large amount of grease onto the spindle shaft and to the O-rings to make damping smooth. Shims were used to adjust the hardness of the damping action. The bearings inside the blade grips were large and strong that could take much abuse. The seesaw was located below the main blade grips, and was connected to a mixing arm with a special linkage on each side of the blade grip. The seesaw had two settings that permit either a 12 or 24 degrees flybar deflection to suit the owner's need, but stock design did not provide any adjustment as to the bell-hiller mixing ratio. With my Millennium, I used S1057 Variable rotorhead mixers that provided 5 different bell-hiller mixing ratios, but it required the seesaw to be set at a max flybar deflection of 12 degrees only. I need to replace the stock mixing arms on the blade grips with two S4552 aluminum mixing arms to use the variable mixer set. A 4mm flybar was to go through the seesaw, and the Millennium came stock with K&S paddles, which were known for their sharp response. A pair of lead weight was included to fine tune the cyclic response. After the whole rotor head was assembled, I put it onto a high point to balance it.
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| Close-up of rotor head | Washout slider with brass sleeve extended |
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| Stock flybar mixer | Close-up of optional S1057 variable mixer |
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| Another close-up of rotorhead with optional mixer | Modified washout slider installed |
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| Bigger pitch window without binding achieved | Close-up of swashplate at 45 degree offset |
Next came the assembly of the tail unit. The tail gear box consisted of two pieces of molded plastic that encase the tail gear and fit together alright. At first when I ordered the Millennium kit, I also ordered the optional S0318 curved tail gear set of Robbe that was said to be stronger, but Bob Johnston told me not to get those cause his could not last more than 5 minute before they stripped. Once again, this shows Bob's professionalism in taking care of business, cause he told his customer not to buy a certain thing according to his experience. Not a lot of shopkeepers would do what Bob did! I trusted Bob and took his advice. While assembling the tail gearbox, care must be taken when setting up the gear mesh of the spur gears inside the gearbox. Generous amount of grease was applied inside the tail gear housing for adequate lubrication of the gears. Tail pitch control was by a plastic arm with bearings on rotation points. The tail rotor had three bearings that make tail pitch change very smooth. Power was transferred to the tail from the main gear through an aluminum tube that runs inside the tail boom. Connecting the aluminum tube with the tail gearbox was a pair of dog bone adapter machined in Delrin. The bearing support on the tube drive and the tail boom were tight fit, so I use some lubricant to ease sliding the tube in. I used the new K&S tail blades that were said to produce less noise. The tail support and fins were being fitted at this stage, and I fit the optional carbon fins and the aluminum horizontal fin holder. The tail support were made in aluminum, and they were hefty in size. While fitting the vertical fin, I found that one of the mount was missed in the box, which Bob gladly sent me one by express post without charging me a dime, another good service by Bob!
After the tail boom was being mounted onto the main frame, I skipped steps to mount the tail servo. I used a JR 8700G for tail control. Tail servo was mount transverse on the middle rear part of the main frame. I liked this tail servo position very much cause it provided very direct control on the rudder. Other tail boom mounted servo position would had the tail control rod bent to a certain extend to reach the servo, which causes slop, and almost always boom mounted servo would upset the CG of the helicopter a bit. The Millennium's tail servo position would provide straight routing of the tail control rod, while would not upset the CG. Very brilliant design, and I'd say this tail control design was just second to the Kyosho Caliber 60, which in my opinion had the best tail control design by far.
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| K&S special tail blades | Transverse tail servo mounting position |
The clutch mechanics was another interesting design that I bought the Millennium for. The clutch bell was an interesting item where it was shaped like an inverted ice-cream cone, with holes drilled around the cone for cooling. A pinion was fitted onto the top of the clutch bell (cone) and to a bearing block. A tapered collet was first slot onto the crankshaft, then the cooling fan, fan hub, clutch and a clutch cover were then slotted onto the engine's crankshaft, all held in position by a woodruff key, and then the whole assembly was secured by a prop nut. Both the clutch and fan were large and strong, but I replaced the stock plastic fan with an aluminum item from Robbe. After the clutch assembly was secured, a start adapter was to fit onto the clutch cover. Starting of the engine was through slotting a 7mm hex drive that would go through the bearing block to the start adapter directly fitted on top of the clutch cover. The whole assembly was very clean and smart. I used a regular OS61SXWC as power plant, which did not have the long crankshaft as with European engines. Millennium, like other European helicopters, required a long crankshaft engine, but Robbe was clever enough to have an adapter that enabled using a regular crankshaft engine with the Millennium. Since European engines were rare out of Europe, the availability of this adapter made the Millennium more marketable out of Europe. Mounting of the engine was through two pieces of metal engine mounts which were beefy in size. At this stage, the manual also mentioned the assembly of a glow plug extension that came with the kit, which I did not use because it used RCA connectors that resembles those use in Hi-Fi. I replaced the stock glow plug extension with one that is dummy plug style so that I could use regular glow driver.
Next on the manual was fitting of servos and linkages, but I skipped that and go to fit the fan shroud instead. The fan shroud were three pieces of plastic, with two carbon mounting pieces to fix the whole fan shroud onto the main frame. The fan shroud requires a lot of cutting and trimming for it to clear the needles and the throttle control arms on the carburetor, which took quite some work. Inside the fan shroud was a piece of plastic current diverter that was supposed to be set nearly touching the heat sink so that all current from the fan would go through the fins on the heatsink to maximize cooling effect. The fan shroud was massive, and it covered the whole engine heatsink. Adjusting the fan shroud in position not to touch the cooling fan was another time consuming feat. The fitting of the fan shroud in fact took me one whole night.
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| Engine with clutch and optional metal fan | Clutch bell and optional short crankshaft adapter |
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| Engine mounted on frame | Close-up of the huge fan shroud |
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| Inside of fan shroud showing diverter | ¡@ |
After fitting the fan shroud, the assembly came back to the main frame, where servos, various mixers and linkages were to be fitted. I used the new JR NES8300 Super Servos on the cyclic, DS8201 on throttle, a CSM ICG540 gyro and a NES 8700G on tail. While sitting the servos on the rockers and the plastic mounts, I found that the holes that were pre-drilled on the mounts were for the size of Futaba servos. JR servos were a bit larger in size than Futaba servos, so I have to re-drill the mounting holes for JR servo. Various helicopter manufacturers would made their servo mounting holes conform to a specific brand of servo. In the case of Robbe, since they were the European importer of Futaba, so they made all mounting holes conform to Futaba servo specifications. While this might be logical to the manufacturer's support of a particular brand of servos, it would made users that uses servos of other brands very difficult to install their servos on to these helicopters. In the case of the Millennium, using JR servos would require me to either re-drill the servo mounting holes for JR servos, or use the original holes but have to use a bit of force to screw on the servos. I choose the re-drill the servo mounting holes, but this took some extra efforts.
The control mechanism was another feature that I bought the Millennium for. The Millennium used conventional method for cyclic controls, in another words, not CCPM. However, the way that Robbe executed the mechanical mixing for cyclic control was not by using various mixing arms but through the use of moving servos on rockers. Robbe placed the swashplate at 45 degrees offset, with the aileron control servo and elevator control servo each sat on rockers and linked diagonally to the swashplate through L-shaped bellcranks. Collective pitch control would be by the pitch servo moving the rockers of both elevator and aileron servos. This control mechanism achieve the best of both worlds between mechanical mixing and CCPM cause aileron and elevator servos were linked to the swashplate directly with minimized slop, but would still retains the cyclic control smoothness that exist on conventional mechanical mixing.
I made all pushrods according to the instructions, and later found them to be on the ballpark with little adjustments required. These pushrod came in 2.5mm thickness, not the usual 2.0 or 2.3mm thickness, so that should be more stronger. I set the pitch curves of my Millennium for 3D, to give a pitch window of -10, +13 degrees.
When I tried to install the power switch, same problem that I had with servo mounting came back to haunt me. In Europe, Futaba radio were imported by Robbe, and the design of the power switch that came with European Futaba units were not like what we used to see. Their power switch were box type that were 2 to 3 times larger in size compared to what we have. In the Millennium, there was a place to mount the European size switch, but no place to mount the regular size switch. Since the original void for the European switch was too big to fit in my JR power switch, I have to find some place to mount it. I dig into my parts bin and found there were several Hirobo Eagle switch plate unused, so I drilled two holes in the lower part of the main frame and fit the Hirobo switch plate.
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| JR 8300 servo | Cyclic control servos on their rockers |
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| Original switch plate position | Use of Hirobo switch plate |
After radio setup, I put on the tune pipe and landing gears. I used a Zimmerman stainless steel header and a Nova Rossi tune pipe for exhaust. The long tune pipe would run from the engine to the very rear of the helicopter, and secured by a plastic tune pipe mount that is clamped onto the tail boom. The look of the Millennium with the tune pipe was awesome, but tuning it would require extra effort than to use a muffler.
I jointed the tune pipe and the header with a piece of silicone pipe joint from Kavan, and secured the joint with stainless steel clamp that were widely available in hardware store. These stainless steel clamps had screw on each of them to adjust the tightness and the good thing about them was that they were re-useable. Since I anticipated that I had to take off the pipe several times in the future to tune the exhaust, so these re-useable clamps would be better than nylon straps.
Those stock landing gears have very low profile, and colored yellow to match the canopy. I used a pair of NHP 710 carbon blades, which were proven for performance by Bob Johnston. I routed the servo wires and packed the receiver in foams. A K&S header tank was used to provide better flow of fuel to the engine.
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| ¡@ | ¡@ |
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| Nova Rossi tune pipe | K&S header tank used |
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| Stainless steel pipe clamps | ¡@ |
The canopy was made of "vacuum pack" material, which came almost ready to be mounted without trimming. The "glass" part of the canopy came bonded in one piece with the whole canopy, so no extra work was needed. The only work required to the canopy were to put on the rubber grommets and stickers. The shape of the canopy was sleek, good looking and it is shaped contour to the mechanics without any unwanted bulge. Using exhaust other than tune pipe would require cutting the canopy, which would damage the look of the Millennium canopy. Bob Johnston was kind enough to put his signature on my canopy, and his signature made the canopy look even sharper. The decals were very thin and sticky, and the standard scheme was so simple that four big piece of livery would finish up decorating the whole canopy. I used the "soapy water method" to apply decals on the canopy. While mounting on the canopy, I found that using an extra pair of S1048 on the lower canopy mounting post would save me the hassles of fumbling with the canopy mounting screws.
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| Canopy before applying decals | Note Bob Johnston's signature! |
After everything was mounted I checked the CG of the helicopter and found it a bit tail heavy due to the hefty Nova Rossi tuned pipe. About 60 grams of weight was glued onto the canopy to make the CG balance on the main shaft. The dry weight of my Millennium was a tad over 9lb, which is quite light compared to other 60 class machines. With everything ready and checked, I waited for the test flight to come.
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| All set and ready to fly! | Use of tune pipe without modification on canopy |
Conclusion
The Millennium passed with flying colors as a 3D helicopter. Its fast, agile and execute everything with precision and brute force. It does have a little bit pitfalls, but if you could cope with them, like to 3D, the Millennium is a very good piece of machinery to have.