Some might have read the article I did two weeks back on the Raptor 50 Xtreme edition...Somehow, it got lost in the server upgrade process and so I did a repost of the article HERE.
In any case, I have continued on with the little project and finally have got everything sorted out. For those the busy ones who just want to know the results...Basically, this whole conversion is definately a worthwhile effort. It corrects the bad tendency of the stock raptor head, that is the pitching in FFF and slow roll rate. It gives a very nice feel in the cyclic, not too slow, nor too sensitive. With the new head, I can get that sort of "pop" effect that I thought was only possible on the 90 size. A lighter pair of paddles like the super stubz will make this head even better for 3D.
For the interested ones...read the full story here =>Preparing the head...
FLybar carrier
The head came assembled, but there was one problem pointed out to me by the previous owner- The flybar bar carrier bearings. In the "older" 6mm RJX head, the flybar carrier is secure to the rotor hub by a pair of 3mm screws that many had problem with. So in the 8mm edition, the screws were changed to 4mm, along with a new flybar carrier. Flange bearings were employed, but without any form of collars for the screws that goes into the hub and flybar carrier.
That means that the tolerance between the bearings( that are seated into the hub) and the flybar carrier has to be PERFECT. Else, the screws will press the bearings toward the carrier, thereby pushing them off their position in the main hub. This creates a loose and shaky flybar carrier relative to the main rotor hub.
My solution to this was to take out the bearings, clean them and reinstall with R48 retainer. Glad to report, its still intact and tight after 8flights. A better solution might be to have a collar on the screw, but that will require a bearing change. Adding shim to better the fit between the flybar carrier and the flange is almost impossible because its tight, but not tight enough.
Dampers
I had originally wanted to change the dampers on the head since it was bought used(and in relatively unknown condition) but was told by the local RJX dealer that this head was just purchased from him very recently and the dampers in the 8mm head are very lasting. Anyway I got a pack of dampers just in case. Note that the 8mm head makes use of O-rings instead of the typical dampers. Have to admit, this head is stiff, even more so than my T-rex 700N.
Washout arm
Due to the smaller diameter of the raptor swash, the longest push rod on the head will bind against the screws on the washout arm. Coming up with a solution to it was a lot more time consuming than I had thought. Anyway, in steps...
1. Replace the ball linkage end on the swash with those shorter ones on the double links of the raptor head. The longest raptor linkage rod on the head will work ok for this head. Adjustment required.
2. Replace the washout hub screws with BUTTON HEAD SCREWS. Only button head will work here. Cap screws don't. I elected to use the RJX washout hub and arm because they fit the screws I have w/o the need to cut the screws.
3. No matter which washout arm or washout hub you use, make sure to use the raptor's washout linkage arm because it sits the washout at the right height.
4. Adjust the phasing ring so that the washout hub don't hit the ring on the max positive collective and doesn't "escape" from the pin guides at max negative collective. Note that the RJX washout hub will have a smaller length of "bite" on the phasing pins.
With that, the head was fitted on with no other significant issues that I can remember of.
SETTING UP...
Mixer Level Position
The most important part in setting up is TO KNOW WHAT YOU ARE DOING. Since I did not have a single clue as to what each position on the mixer arms stands for, I had to refer to this...
This paragraph caught my attention.
"IMPORTANT:
When using very responsive settings the forces applied to the CCPM servos are higher
than normal. Plastic servo gears can suffer or break. Servos with metal gears are
recommended for those settings."
Since the load on the servos for a ECCPM heli is 1/3 of what the servos in my MCCPM raptor will see, I couldn't help but start to worry because I haven't got any metal gears in my servos. So in an attempt to reduce the in flight load on the servos, I changed the ball link position of the servo arms and the collective pitch cradle arm. This will reduce load on the servos, but also slow down the servos, which doesn't matter for me because I don't ever "crack" my heli. I found the 10mm position on the cyclic servo arm to work good for me. As for the collective pitch cradle, I opted for the outer hole with a push rod length of 58mm tip to tip of ball linkages. Haven't had any issue with stripped servos yet, hope it will never happen.
And the mixer arm positions that I ended up with after lots of fiddling and measuring...yup, same as the previous owner of the head.
Blade Shims
Before setting up the push rods length, I will need to at least put on the blades. What started out as a 2mins quickie ended up as 2hr of agony. You see, I always use two pairs of blades for maiden, a pair of cheap Funkey FG blades for first flight test in case something is wrong and a pair of Rotor Tech 610mm for actual flying because they just make everything feel faster. The FG blades fitted the blade grips on the head with 2x 1mm washer on each grip, but the Rotor Tech 610mm did not. It was a case of one too few and two too many. So I had to spend a good 2 hours trying to grind down 4x 1mm washers to something like 0.75mm thickness. After the first 2 aluminium ones were done, I decided that enough was enough and started looking for alternative. Thank god I found some plastic 1mm washers from my VERY old Funkey blade packaging. Grinding aluminium vs sanding plastic...go figure...
Note the black washer on the underside of the blade root. That is the plastic shims...
I also found the nut retainer cup on the blade grips to be loose and spining together with the blade bolt nut. Again, R48 retainer fixed it.
PUSH ROD LENGTH
As per the linkage labelling in the photo above, from tip to tip of ball linkages...
Rod A=>50mm
Rod B=>99mm
Rod C=>35mm
Rod D=>60mm
Rod E=>80mm
Because my elevator A arms are adjustable ones, YMMV for rod D with the stock elevator A arms. A good way to start would be to keep the cyclic servos at neutral and set the rod D such that the swash is FLAT. With those rod lengths, I set my head for +/-12 for collective and +/-7.5 for cyclic. There is still more to spare if desired.
Binding Issue
After all the setting up, I was puzzled for a good 2 days by some weird binding. What happened was that at max negative collective and a slight amount of cyclic, the flybar would bind on the slightest deflection. I checked the rods and ball links and nothing was even touching. I looked, I observed and I stared. At long last, I found the culprit- The linkage balls with the hex nut molded on it. The hexagonal nut part was binding against the ball links at certain conditions. Consulted the expert on runryder and was told that RJX has a different type of linkage balls w/o the "nut" part now, just like on the Kasama linkage balls. Thanks to my local RJX dealer I was able to get it a few hours later...
Where it was binding...
The solution...
MOST IMPORTANTLY...FLYING
As per the intro of the this article, I found this head to be much better at FFF than the raptor's. Cyclic are more positive, but not overly so. Collective was very good too. I did manage to get a slightly faster roll rate, but its still nothing like on the 700N. I suppose I might need either a 3mm flybar conversion or a pair of lighter/larger paddles. Its definately a worthwhile conversion to me.
There were however two very interesting observations.
Firstly, I found that with the correct pair of blades and paddles and suitable position on the rotor head, this rotor head will make the raptor a VERY good F3C trainer. Using my funkey 600mm FG blades, which are supposedly over 140g, and the Align CF paddles, my raptor had EXCEPTIONAL hover capability. Despite the stiff damping, it was so smooth and stable that I WAS SHOCKED. The hover was even more predictable and stable than my 700N. Tracking in aerobatics flight was good too.
Secondly, and even more shocking, I thought my raptor flew better with the cheaper FG blades that was so much slower on the stock raptor head than the Rotor Tech 610mm. With the Rotor Tech 610mm, power demanding manuveurs were slightly less demanding on the pilot's collective management, but thats it. The Funkey FG 600mm that used to feel too soft(as in literally, physically too soft) on the stock raptor head was now much better in everything, and I mean everything.
Hovering with the Rotor Tech 610mm, Align paddles and the mixer arm settings as per above also proved to be a disaster. There was a VERY strong tendency for the heli to fly into the wind, it was EXCEPTIONALLY BAD. Suprising, isn't it? How a change of blades and mixer arm position can totally transform the heli.
Conclusion
Overall, the RJX head is a big step up from the stock design of the raptor head. With a head like this, you get the best of both world- modern head design with a strong and proven plastic frame and a very simple tail belt drive design. TBH, this is already the ideal 50 size weekend stick banging trainer. With a decently powerful engine(i.e a hyper with fresh bearings and ring and a hatori #522), it feels decent even when compared to a 700N.
Having said the above, I don't suggest that anyone just run out and buy a RJX head to stuff onto a raptor. This type of "unorthodox" conversion is very time consuming and can be costly. Do consider the economic sense in buying a brand new head for conversion vs selling your existing raptor and buying a new heli. For me, I did the conversion because I got a used deal for the head and I really love the simplicity of the plastic frame and mechanical mixing on the raptor. And in recent times, I have learn to appreciate the quality of the raptor vs my 700N.
No comments :
Post a Comment