Back in the year 2000 Hirobo introduced the Freya helicopter kit. Before the Freya, 60 size helicopters are considered by most as the top end level helicopter. The Freya, with its easy assembly, maintenance, very versatile flight performance, and economical price quickly won many helicopter pilot's vote as one of the best helicopter available in the history of r/c helicopter. Even while other helicopter manufacturers tried to follow later with their own version of economical 60 size helicopters, the Freya still tops them in terms of value and performance.
All during the years after the introduction of the Freya, it has been through several updates and offerings to cope with the ever changing needs and demands of helicopter pilots. Hirobo, while keeping on the success of the Freya, introduced the Freya Evolution in the year 2005.
The Freya Evolution features the following new designs that is updated from the original Freya design:
Basically most of the above new design parts more or less take reference to the parts of Eagle 3 WC. These modification is to transcend the Freya Evolution into a more refined and precise helicopter, while keeping the value in the level of the Freya. According to Hirobo, over 50% of the Freya Evolution parts are newly designed parts compared to the original Freya.
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Freya Evolution |
Freya Evolution 90 |
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New FFZ-III rotor head |
New clutch bell, switch plate and elevator assy |
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600cc fuel tank |
New pitch control bellcrank |
Here are the dimension of the Freya Evolution as follows:
Engine size: 60-70/80-90
Rotor diameter: 1,561mm (680mm blades)
Tail rotor diameter (With stock tail blades): 270mm
Gear ratio (engine:main:tail) : 60-70 - 9.5:1:4.77, 80-90 - 7.9:1:4.77
There are 2 different packages of the Freya Evolution, the 70 and 90. The only difference between the two is just the gear ratio only.
This article is to review a Freya Evolution 90 kit. Hirobo supplied this kit to me, and emphasized that my kit is a pre-production kit for testing purposes. Future official release kit would have some difference. Especially, my kit have the old type Freya autorotation hub, the new hub body is still in mould testing phrase so it could not be included when they ship the kit. Hirobo mentioned to me that this new autorotation hub assembly uses a beefed up one-way bearing for better reliability.
In additon, Hirobo also mentioned for the USA market there will be a special version of Freya Evolution kit, and this USA version would only have one version for 91 size engines. Basically the USA version includes different parts than the worldwide version as follows:
Seems like once again the Americans are getting a better kit again, thanks to Jeff Green of MRC (Jeff U Da Man!)
Now let's take a look at the assembly of my kit.
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| Freya Evolution and Eagle 3 WC | The first view after open the box |
Upon opening of the box, I see all parts are being laid out in a orderly fashion. Inside the box the first thing that catches my eyes is the blow molded plastic canopy covered by the decals and instructions manual package, besides it is the main blade, then on the side is a small partition that houses bags of small parts. The packaging of the Freya Evolution kit is in line with other Hirobo helicopter kits, with all parts packed nicely into different bags and according to the steps of instructions. All bags are 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 the parts and screws required for that step of assembly would be included inside that bag. Due to my kit is pre-production beta version, I noticed that all bags are tagged with "Freya Evo (USA)". The instruction manual of the Freya Evolution is by far the best Hirobo has to offer, not only does it have the usual highly detailed drawings on assembly, but it has a lot of in depth tips on how to setup, flying and maintaining the helicopter kit for beginners. Gone are the "Jap-ish" that is usually seen in other Japanese made helicopter manuals, and I know Jeff Green of MRC has his contribution on the English part of the description to make it more pleasant reading for English reading owners.
First inspection found that almost all the plastic material of the Freya Evolution, although at first look not much different from the original Freya, but the pieces are much harder to be bent. Later, I confirm with Hirobo that most plastic part of the Freya Evolution are being molded by a blend of plastic and graphite, same plastic material as the Sceadu Evolution. This type of "graphite-plastic" has been used widely by r/c cars to firm up their chassis, and now they are being used in the Evolution line. Hirobo told me that their R&D department tried different compositions of plastic and graphite blends, and finally comes up with the 22% graphite/78% ABS blend that is being used in the Evolution line, and according to Hirobo too much graphite mix would make the plastic hard but brittle, and this blend is used after a lot of trial and errors.
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| Box contents | New main blade |
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| All parts neatly packed in small bags | Each bag packed according to instruction steps |
The first major part of the assembly dealt with assembly of the upper main frame, that also houses the elevator arms and the front tail drive transmission.
The elevator arms assembly is one of the new design item of the Freya Evolution, in that it is based on the elevator arms assembly of the Eagle 3, which have the elevator A-arms offset to offer less binding in extreme swashplate tilting. The assembly should be very straight forward, and Hirobo have incorporated little fins on the base of the assembly so that the user cannot go wrong with the orientation of the elevator A arms. However, during assembly I found that the spacers that goes between the base bearing of the A arms have the inner holes a little bit too small so that the self tapping screws could not go all the way in. Due to the material of these spacers, which is very hard, it took me quite some time to make the inner holes bigger to clear the threads of the self tapping screws. I think this is just one minor glitch of a pre-production kit. I already alert Hirobo about this and they would make sure this problem would go away in the official production version.
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| Elevator assembly | Screws could not fully go into the spacers |
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| Assembled elevator assembly | ¡@ |
The tail pinion assembly of the Freya Evolution is in fact the same thing as the original Freya, where the whole assembly comes fully assembled from the factory. Further examinations reveal that the counter gear of the Freya Evolution is in new molding design where it should offer more longevity in operation.
The top main frame assembly comes in two pieces of molded plastic frames, with an addition piece that goes to the front for receiver tray. The moldings are of high quality, with the side of each pieces clearly marked for identification, and although the mold marked "Hirobo 2000", I inspected the frames and found that it is actually modified to incorporate several updates. Of all the updates that I found being incorporated into the Freya Evolution upper main frame, the major update that I think very useful is the clutch bell being support part. Now the clutch bell bearings assembly is being supported by 3 bearings instead of the original 2, similar to the Eagle 3 design, and this should provide more precision and smoothness on drive train operation. While assembly of the upper main frame, special attention must be paid to the orientation of the elevator arm assembly while sandwitching it inside the upper main frame, cause if you get them wrong you have to disassemble the frames again. I applied some Loctite on the side of the bearings to prevent them from turning loose inside the frame. Another update that I found which is good is that now the Freya Evolution uses hex cap screws and locknuts for fastening together the main frames, instead of the old Freya's metal philips screws and regular nut that requires Locktite. I liked this change very much because in the past I have had no luck with the philips head screws and regular nut, I preached Hirobo for long to use hex cap screws and locknuts for easier assembly and maintenance. I am glad that Hirobo finally listened to me at this point. Although it is a plastic frame, when I assemble the upper main frames I placed them on a flat piece of glass or marble with the main shaft through the main bearings to make sure secure the alignment, but later I found that this step is useless as the frames are aligned without using much attention. Everything fit without the use of saw and file. From my friends who are in plastic molding business to make plastic parts with precision like this requires very high technology and attention, and this shows Hirobo devoted a lot of attention into making their plastic parts.
During assembly, a few steps I took to prepare the frames for better fitting. For a detailed description on how I assembled a plastic main frame, please refer to my page about "Tips on assembling a helicopter ".
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| Tail pinion assembly | Parts to assemble the upper main frame |
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| Upper main frame pieces | Markings inside the frames for easier orientation |
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| 3 bearings for clutch bell support | Assembled upper main frame |
Before joining the lower main frame to the upper, the fuel tank has to be assembled first. The fuel tank is the exact one being used in the Eagle 3. Compared to the old EX fuel tank being used with the old Freya, with this Eagle 3 fuel tank the size is up from 540cc of the old EX fuel tank to 600cc now, also the thickness of the sidewalls have doubled to take up the air pressure of YS engines that runs on pressurized fuel system. However, while the Eagle 3 uses 10 rubber grommets to hold the tank in position, the Freya Evolution only use the 6 that is much bigger and stronger in size compared to the old EX. Assembly of the fuel tank is no brainer, but during assembly I used a file to take of minor flashes on the metal tubes so that they would not cut into the fuel tubes. Also, I changed the inner tube from the original one to a one made by IM because the original one would go kink in extreme bend, and in one case I even find the tube tied a knot by itself inside one of my Eagle. With the IM fuel tube these problems does not exist so far with me. While the manual says the inside tube should be 100-105mm in length, I find that 92mm is the best length to provide best fuel flow without the fuel tube tangling inside the tank. After the fuel tank is assembled, I submerge it in water to check for leaks, and find that there is no leak. This step is very important because if you use engine with pump system like YS and the new OS 91 SX-H C. Spec PS if the tank leaks fuel pressure will not be consistent. In the past with EX fuel tank according to my experience only 4 out of 10 tanks that does not leak, but this Eagle 3 fuel tank is good on the first try.
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| Eagle 3 WC fuel tank component | Fuel tank body |
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| Left is original fuel tube, while right is IM | Round up the edge to prevent cutting into tubes |
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| Leak test fuel tank | Assembled fuel tank |
The lower main frame comes in two pieces of molded plastic, with the fan shroud incorporated into the frames. Once again although the mold marked "Hirobo 2000", I inspected the lower frame pieces and found that it is actually modified to incorporate several updates. One of the update is for the bigger grommet of the Eagle 3 fuel tank. The fuel tank is housed in between the lower main frames, and is hold onto position with six rubber grommets. These grommets have grooves to hold themselves onto the openings of the lower frames, so no glue is needed. Another update is an opening on the landing gear mount for the optional use of the EX landing gear dampers (Hirobo #0404-701). Once again when I assemble the lower main frames I placed them on a flat piece of glass to make sure secure the alignment.
The instructions calls for the use of two 3X64 cross members (Hirobo #2511-007), one on the front, another on the rear, to further strengthen the lower main frames. These cross members have only 6mm face to touch on the side frames, which I think provides not enough perpendicular side support. I made different cross members by using two 3X60 cross members (Hirobo #2511-024), with each ends hammered on an EX screw spacer (Hirobo #2506-039) upside down. These cross members now offers 10mm face for perpendicular support to the side frames. In order to install one of these cross members onto the front, I have to take off a little bit material from the side frames to clear the cross members. Further, I use one more of these cross members on the holes near the middle of the lower side frames for further support.
The USA version of the Freya Evolution includes a third metal bearing holder (Hirobo #0404-618) to be installed on the lower main frames, located right beneath the main shaft. For non-USA Freya Evolution kits this part is optional. The use of this part is supposed to further strengthen the drive train. I install this part into the lower main frame, also put in another 10X19X5 bearing into this bearing block to further strengthen the drive train. Note the orientation of the bearing block when installing it.
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| Parts for assembly of the main frame | Lower side frame |
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| Grommet opening for fuel tank | Parts to make up special cross members |
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| Hammer EX spacer onto end of cross member | Assembled special cross members |
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| Special cross members installed | EX landing gear dampers installed |
Joining of the upper with lower mainframes comes next. Assembly of the whole main frame was so easy that it take me less than one hour to have it standing in front of me. According to the instructions, fitting the landing gear comes next, but I intentionally skip that and wait until all the mechanics have been fitted onto the main frame.
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| Main frames before joining together | Assembled main frames |
Next comes the fitting of the main shaft with the DTDS gear onto the main frame. The main shaft of the Freya Evolution is same as the Eagle 3, that have 3 different settings of rotor head height (185mm, 195mm and 199mm respectively). Although the instruction said to use the 185mm hole, it is still possible to use the other two holes just by changing four push rods that connects the rotor head to the swashplate. The longer length main shaft setting is said to provide better hovering characteristics. The lower DTDS gear comes attached to the autorotation assembly. Hirobo mentioned to me that my kit includes an old type Freya autorotation assembly, while the official release Freya Evolution would come with a new autorotation assembly with a much stronger one-way bearing. I have attached a photo of the new one-way bearing below. The EX main gear 95T is a machined Delrin item for smooth operation. For the USA version this main gear is 93T that should offer more RPM for better 3D performance. The main shaft collar is the same as the Eagle 3, which is a clamp on style, rather than the old style which would dent on the main shaft. While installing the main shaft collar, pull the main shaft up fully with the whole main frame suspend in the air, while securing the main shaft collar, is the best way to ensure no end play on the main shaft assembly.
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| Main drive train parts | Main shaft with 3 rotor head height settings |
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| Clamp on style main shaft collar | Securing shaft collar while suspending main frame |
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| Third bearing block | New one-way bearing |
Once again I skipped steps to fitting the engine onto the main frame because I wanted the whole drive train to be fitted and align. I use a YS91ST engine as power plant for my Freya Evolution. The clutch parts are actually the same as the Eagle 3, a clutch hub is to be mounted with a cooling fan secured by the prop nut, and on top of the clutch hub are the clutch and the clutch bell. The Eagle 3 WC fan hub uses a taper collet, which the manual recommend dial indication to less than 0.05mm on the fan hub and tip of the clutch shaft. Hirobo explains very clearly in the instructions manual as to how to dial indicate and adjust the fan hub and clutch to achieve acceptable run out. Although very time consuming, this step is require for smoothness on drive train operation.
After the fan is dial indicated, the whole engine assembly is to be installed in between the lower main frames. I notice that the Freya Evolution clutch bell is different than that of the Eagle 3. With the Freya Evolution the clutch pinion use the old design, small blocks type pinion. The Eagle 3 12T clutch bell pinion gear comes with "real", triangular shaped teeth, and should provide better operation smoothness than the Freya that have gears that looks like small blocks. I think this is due to the fact that Hirobo did not change the clearance of the Freya Evolution frames for the Eagle 3 type pinion, so they have to revert back to the small block type. Once again for the USA version this clutch bell pinion is 11T instead that should offer more RPM for better 3D performance.
I use the optional WC one piece engine mount (Hirobo part# 0404-716)for more reinforcement on the lower main frame. When fitting the engine with the engine mount onto the main frame, I had to first slide in six bushings onto the plastic main frames in between the frames and the engine mount. These bushings are there to prevent the mounting holes on the plastic frames to deform after securing the engine mount onto the frame with the six 4mm screws. When fitting these bushings, I used some greese on them so that they would temporary stick onto the main frame to prevent them from dropping off during the fitting of the engine onto the frames.
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| YS91 ST engine | Fan and clutch parts |
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| Clutch bells with different type of pinion | Regular triangle type pinion gears |
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| Small block type pinion gears | Check run out on the tip of the fan hub |
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| Check run out on the tip of the clutch shaft | Run out less than 0.05mm |
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| Optional WC one piece engine mount | Engine fitted into main frame |
As I am still assembling this helicopter kit, please check back for latest update.