dkshema
rrMaster
Location: Cedar Rapids, IA
My Posts This: Topic Forum | I've done a little experimentation on my EP to sort out the excess play in the collective mechanism.
I dismantled the MR shaft piece-by-piece last night. The first thing I noticed is that the Z-bends are a pretty darn tight fit in the various holes in the levers (washout levers, and bell-hiller mixing levers. There really is no noticeable play in the Z-bends in the head).
The ball links on the MR grips are a good tight fit, no play there.
A few weeks ago, I sawed the plastic balls off the swashplate, and replaced them with balls and screws from my T-Rex spare parts. Though this made an improvement in the quality of the balls, but the washout links and flybar control links were a sloppy fit on the T-Rex balls.
Grabbing the head, then twisting the MR blades showed that a large amount of the play was due to the loose fit of the washout links on the swash balls.
I dug around my box-o-spares and found a bunch of Kyosho balls. I think I ordered them a long while back when I had a bad crash with one of my Caliber 30's and needed to replace some of the missing balls.
Then, I whipped out my digital calipers. What I found is that the T-Rex balls average about 4.69 - 4.70 mm in diameter. The Kyosho balls measure on the average, about 4.75 mm in diameter. This is good.
I replaced the T-Rex swash balls associated with the washout levers, and immediately got a good, slop-free fit of the balls. At the same time, the majority of the play in the MR blades vanished. This is even better. All balls on the swashplate are now Kyosho metal balls, and the links fit much better all the way around.
I'll see if I can dig up the part number for those balls and post it when I find it.
Next, I took a look at the pitch slider mechanism. I was looking for vertical play in the slider, as Dwight and others had posted about making shims that go under the E-ring to remove the play. What I found was that there was very little, if ANY vertical play. BUT -- the little plastic ball of the pitch control lever that fits in the hole in the side of the pitch slider is a different story. The plastic ball is a loose fit, and allows a large amount of slop in the collective system.
I removed the slider and dismantled it. I also took the pitch control lever off the frame and trial fit the two by hand. As I said, the ball is a loose fit in that socket.
Enter my X-acto knife, a 3/16 inch drill bit, and a 1/16 inch drill bit.
The plastic ball is about 3.8 mm in diameter. I whacked it off, then sanded what was left of the stub so that it was flush with the surface of the pitch lever. Next, I used a pin-vise and a 1/16th inch drill bit to drill a hole in the center of where the plastic ball used to be. I took one of my 4.75 mm diameter spare Kyosho metal balls, and using a screw borrowed from my T-Rex stash, screwed the metal ball on, in place of the plastic one I'd just cut off. I put a little dab of CA on the screw where it came out the other side of the pitch lever, then hit it with accelerator.
Next, I removed the E-ring from the pitch slider, took the metal bushing out, and removed the two ball bearings. I drilled the existing hole in the side of the slider out using a 3/16th dia drill bit. Next, using a smaller diameter drill bit and some 400 wet-or-dry sandpaper, I carefully enlarged the drilled out hole until the new ball fit without binding, but was careful not to introduce slop into the fit.
The 4.75 mm diameter ball is too big to allow the two bearings to fit back into the slider, while allowing the bushing to be reinstalled and putting the E-ring back on. Soooooo...
I cleaned the varous parts in alcohol, then using a microbrush, painted a thin film of GREEN loctite on the inside of the pitch slider where the ball bearing outer races seat. I put the bearings in, but did not drive them fully home. Instead, I put the pitch lever with its new metal ball into the hole in the side, then CAREFULLY pressed the two bearings in, making sure they did not bind on the metal ball. Using the same microbrush, and the GREEN loctite, I then carefully wicked green loctite into gap between the outer race of the bearing, and the inner surface of the pitch slider.
I set the assembly aside for about a half an hour to let the loctite cure.
Next, knowing that I was not going to be able to reinstall the E-ring, I used a new microbrush to put a film of RED loctite on the parts of the bushing that fit into the inner race of the ball bearings. I slowly pushed the bushing back into the assembly, and again, set the assembly aside for about a half an hour to cure.
Once things set up, I reassembled the MR mast. The pitch control works just as good as it did in its original configuration, BUT -- the play in the collective system is nearly gone. The only play that is left, arises from the small amount of play between the washout slider and the MR shaft.
I'm a bit worried that the assembly may come apart since it's relying upon red and green loctite. I trust the loctite based on past experience, but you just never know for sure!
I took the heli out to the driveway this evening after work and hovered it, flew it forward, backward, sideways, up and down -- exercising the collective and the rest of the MR controls as best I could in the limited space.
The heli feels a lot "tighter" now with all that slop out of the collective mechanism. Time will tell if the loctite holds up, but until then, I believe this fix will be worth the risk. If I had access to a good lathe, it would be easy to take a little material off the bottom end of the bushing to allow the E-ring to be installed.
Dave |
xchurchx
... There is also stronger material of main shaft available at the shop I bought all metal parts in Hong Kong but it is expensive for me...almost 4 times compared to the original shaft.
