dkshema
rrMaster
Location: Cedar Rapids, IA
My Posts This: Topic Forum | I got a bit of time this evening to work on the EP again. I started by mounting the Elevator, Aileron, and Collective servo. It's late, so I'll provide the words, and post some pics tomorrow when I have more time.
I chose HS56 servos based on some feedback from Chris at RCHeliworks, and Hoverking. They recommended a servo having at least one ball-bearing in the output shaft, as having tried EFlite S75s, they noticed trouble with servos centering. Based on how well the plastic links fit the control balls, I'd have to say that the centering fault is in the servo, not due to drag or friction in the control system. The recommended maximum size for servos in the EP 400 manual, and the need for a ball bearing kind of limited my choice to the HS56s or Airtronics 94091s, without going into some extensive research or big $$$. I settled for the HS56 based on the success people have had with these on the T-Rex.
The mounting method used for the aileron and elevator servo is unique, effective, and will work with any servo, no matter how many holes it has in the mounting tab. It consists of a plastic clip that fits over the end of the mounting ear which is held to the fuselage by a couple of 2x8 mm self-tapping screws. When installing the servos, make sure that you get the mount screws tight enough to keep the servo from moving around in the mount.
The control rod fabrication was quick and painless. I used the standard "X" shaped horns that ship with the HS56 servos, and the outermost hole in the arm which is just shy of 10 mm out from center. The instructions recommend that the hole for the control rod be somewhere in the range of 7.5 to 10.5 mm from center. I used a sharp #11 X-acto blade to enlarge the holes in the arms so they would accept the Z-bend end of the rod. Prior to whacking off the three unused arms on the horn, I centered each servo using my trusty 8103 TX, then figured out which of the four-positions of the arms got me the best centering. I had to tweak only the Aileron servo centering using the TX sub-trim (value of 20). Not sure why that was, maybe my TX needs a trip back to Horizon for a tune-up, maybe the servo is just a bit off. In any event, not a big problem
Note that with all four servos, the extra mounting tabs on the servo case had to be removed. This is easily accomplished by scoring the tab at its base using the tip of the #11 blade, then simply snapping off the tab. Quick, painless (unless that knife gets away from you) and makes a clean break needing no trimming.
The aileron and elevator servos were mounted, the horns installed, and the pushrods fabricated very quickly and painlessly.
The Collective pitch servo is a bit of a different story, this owing to my selection of the HS56s. If you choose to use these servos and remove the three extra mouting tabs, you're left with four holes in the remaining mounting ears, two on each ear. The EP 400 ships with two different mounts for the pitch (and rudder) servo, the size of the rectangular cutout being larger in one than the other. The HS56s fit the smaller of the two mounts very well with one exception. The mount is designed for servos having only one mounting hole on each tab that is centered in the tab. This means an HS 56 needs to have a third hole drilled in each mounting tab. With some difficulty (minor), the tabs were drilled, and a single screw on each tab was used to hold the servo down.
The mount must first be attached to the fuselage (using a couple of 2x8 mm self-tapping screws) , then the servo is screwed down (if you put the servo in the mount first, the servo body conveniently covers up one of the two screw locations for the mount in the fuselage). No biggie, but a pain if you already got the servo screwed down to the mount. It would be a bit easier to mount this (and the rudder) servo had Kyosho continued to use those nifty clips. Apparently, the mount can't be made long enough to accomodate them.
The collective rod was easily and quickly fabricated.
The recommended length for each pushrod is given in the assembly steps, and when these values were used, the swash came out pretty darn level, and the pitch lever ended up centered with the collective stick centered, and a linear 0 to 100 pitch curve in the TX. Mid-stick, 0 pitch. Looks good. I may have to tweak the zero-blade pitch later on when I get the MR blades installed. That will be accomplished by tweaking the pitch links up on the grips.
I still have to mount the TR servo, and it appears that I'll have to make the same accomodations to that servo's mount, as I did for the collective servo. Maybe tonight I'll think up a less painless mod to make mounting the pitch and rudder servos easier (of course, it would be child's play had I chosen the proper servo -- one with a single hole in each mounting tab).
When you install the servos, take the time to center the arm on each one then install and adjust its control rod before mounting the next servo.
A couple of recommendations to Kyosho for the control setup would be:
1. Lose the Z-bend and go with standard issue ball links.
2. Modify the pitch and rudder servo mounts to accept servos with mounting holes such as the HS56. (maybe adapt those neat little clips used on the other two servos).
In a previous post, I noted that the reported loose fit of some ball links hadn't been encountered. Tonight, when I snapped the aileron ball link on the swashplate control ball, I got the feeling that it should have snapped on with just a little more force than it required. I tugged on the link, it appears to be tight enough, and I don't think its in danger of popping off in flight. The amount of force needed to pop the elevator and pitch link was more than acceptable.
Kyosho should address the fit of the swash control ball links in future revisions of the EP.
With all three servos installed for the MR control, I plugged a battery into my RX, turned on the TX, and made sure the servos travelled in the correct direction, and fixed any problems here before proceeding. I should note that at this stage of completion, the servos saw very little, if any, resistance to control movement. In contrast, I had to hand-polish ALL of the balls in my two T-Rexes to produce ball links that weren't too tight, and that allowed my servos to work smoothly. I like the fact that I didn't have to waste a lot of time making each ball and link a custom fit with the EP 400.
Tomorrow, time permitting, I'll post pics to go along with this post over in the EP400 Gallery in my gallery. I'll also tackle the TR servo mount and adjustment, followed by programming my CC35 ESC, and figuring out how and where to mount the rest of the electonics.
After that, it's paint the canopy, mount the blades, set the pitch and throttle curves, then wait for decent weather.
This little chopper is a FAST build so far. The canopy seems to be the only time consuming assembly task.
Dave |
