Blade CX2 - increasing the separation between rotors

[TowPilot]

Hi Sonny,

I have no internet at home until next week, so just a quick note while on WiFi.

I'll check out what is offered when the internet works at home again.

Cheers,

[Dopesick]

So I have a question on this mod...

I've moved my control rods out 1 hole so far, and had the BCoD come up. I have read and tried lightening the flybar which has solved my BCoD.

Does this mod allow further operation of the Swash then 1 hole out? And exactly how much far can we push the swash plate before it binds, or the blades give out?

[TowPilot]

This is my experience, with the CX2 and blade clack.

Stock, the heli is fine when starting when indoors, over carpet and creeping around learning to avoid walls.

Then, instead of buying stock parts, I read about and considered the various upgrades and self made components. It is part of the fun of the hobby to tweak and tweak between flying sessions.

Consider that if the blades did not flex at all, the plane of blade rotation of the upper and lower rotors, would never "meet".

But, the stock blades do flex. The stock blades flex a lot with a hard over stick input.
The flexing due to coning is not a risk because both rotors are flexing in the same direction, upwards.

Flying outdoors, a gust grabs the CX2 and to compensate, the stick input is a rapid full input.
The lower rotors respond to the stick input. At the same time, the upper rotors respond to the fly bar input which is also full travel. If you are flying with a white background while doing this, you can see the lower blades flexing upward at a 45 degree angle or more, on one side of the rotor disk. The lower blades flex upward into the path of the upper blades.

Here is what I found from trying upgrades and making change after change....

The first thought was to separate the upper and lower rotor heads so that the lower blade flex can no longer reach the upper blades. But the more effective means to prevent blade clack is to use stiffer blades that flex very little. The racing blades from RC Rivesud, flex much less and are nearly as light as the stock blades.

Making the fly bar shorter and or making it lighter, causes less of an input to occur to the upper blades, less input, the plane of the upper rotor is more likely to remain out of the plane of the up flexed lower blades.

A major change was buying the EXxtreme Core Version 2. It was hard to bite the bullet, the expense is about 1/3rd the price of the heli.

I really liked all the components except for the version 2 extended outer shafts. These extended outer shafts bend far easier than the stock outer shafts. I did email Sonny regarding how soft the metal is and how easily it would bend. It was so soft, I even received bent extended outer shafts new in the package. Very frustrating. Yes, they were replaced but still too soft for daily flying.

Sonny's response is the Version 3 extended outer shafts are made using a more durable steel.

My current thought is though, the extended outer shaft is not needed when using blade grips and the much more rigid blades.

Before the Version 3 extended outer shaft was available, I had to do something about the never ending problem of bending extended outer shafts.

If the version 3 extended outer shaft had been available I would have tried one. But, I needed to find a solution.

I moved the EXxTreme Core V2 parts to a stock outer shaft. I wanted to re-use the extended inner shaft because the plastic fly bar head has been very good and not broken during crashes and it seems to have less play in the pivot than the aluminum inner shaft head. And it seems equal to aluminum in resisting crash damage and is lighter.
The fly bar might be ejected from the plastic fly bar head but the head does not break (knock on wood). I used a Dremel tool to shorten the extended inner shaft and ground the two flats on the end for the two collar screws to lock to.

I would try a new V3 outer shaft but I have spent too much already on the soft ones :) I find it hard to part with yet another $10 or so to test fly the new one. I have made an outer shaft from 5/32's carbon fiber tubing to the stock length.

The V.2 order came with racing blades and AFC System labeled blades.
The racing blades are thin, light and stiff. The AFC System labeled blades are thick, heavy and even less flexible.

The AFC System labeled blades looked like better blades than the racing blades because they were longer and of thicker plastic and flexed even less. But, what I have found is that these blades are far to heavy, too much inertia in the four blades for the fly bar and the 3 in 1 to control like they would the lighter stock or racing blades. The response just dies with the higher inertia.

Two fly bars ship in the fly bar package, a soft metal one and a carbon graphite rod one.
The metal one of course, once bent, is never good again. The carbon graphite rod is excellent, and returns to its perfect shape after each crash.

The stock landing gear tend to break when you cut the throttle at 50 feet and drop to a concrete driveway, well, just kidding, but the stock landing gear are of a brittle plastic and do break fairly easy. The much softer plastic on the EXxtreme landing gear has lasted for a very long time. I did not break one until I slammed full speed into the corner of the house. I expected lots of crash damage and all that broke was one leg on the landing gear, which I fixed with Goop and a piece cut from a swizzle stick and the lexan canopy was creased for about 3 inches and house paint on it and a small hole was cut into the lexan. No broken blades, rotor heads, fly bar or fly bar head.

The most important thing to do is simply cut the throttle as soon as possible before impact so that the stalled motors do not draw full amperage through the 3 in 1.

I put on a carbon fiber tail boom, much much much nicer for outdoor flying.
The smaller the profile the better is what I've read and I sure do concur from experience. So I'm also considering moving to the racing canopy to get the size down further.

So stock distance between the rotor heads and with the above components, no more clack.

There is a bit more play with the blade grips on the rotor heads than is needed for free play. And on the top rotor head, if you slide the blade grips through this travel, this changes the top rotor blade pitch. So, to reduce this play so that the fly bar is the only factor for changing pitch for the top rotors, I fitted a thin washer on the pins of the rotor head. This really helped for spot landings. It really does not matter if you are landing any where on the floor though.

Oh an one more note. I purchased a used CX2, this one came with the aluminum E-Flite swash plate. It is heavier than the plastic stock swash plate but it has a very good fit to the outer shaft, there is no play. I am flying that now and really like the stability.

When building back up, check each ball link for free travel. I use 600 grit sandpaper to remove the plastic flashing or the poor mold alignment of the plastic balls to make them just free enough that a link will swivel down from gravity. This also works fine for the metal balls. I use a Dremel and polish to make them shiny smooth but the 600 grit is fine enough also by itself to do this.

Balance is not necessary but can be done for the blades. To do this easily I use a spare set of grips snapped together to check blades before installing or, after I clean up nicks from the leading edges. Just tack on the tiny bit of tape to the leading edge about in the middle of the blade to test the balance before pressing it into place on the underside of the blade in that location.

I only say balancing is not necessary because if the blades are far enough out of balance, you will notice it right away after installing them. Most, not all, but most of the blades seem to be so close right out of the package.

Making sure the blades are aligned straight on each blade grip has a greater factor in balance in most instances.

With the current configuration, I can pretty much simply fold out the blades after each crash and go fly again.

My current and very crash damage resistant CX2 currently consists of the core version 2 components
--inner shaft with plastic fly bar head
--carbon graphite fly bar
--upper and lower plastic rotor heads
--the stiffer racing blades
--flexible landing gear
--carbon tubing tail

Cheers ;)

[heuerfan]

Just got this in the mail from helitek-rc.
http://www.helitek-rc.com/cgi/commerce.cgi?product=Shafts&cart_id=1217616491.216

Can't wait to try this out, read good things about this product on rcgroups.

Will post my feedback,
Steven

[TowPilot]

Here is the one I made using the delrin gear from a bent steel outer shaft.

To know where to drill the holes, I used broken rotor heads as jigs.


http://www.helifreak.com/attachment.php?attachmentid=56936&d=1217383361

The logo on the Helitek web site is about the best looking one around. Click the logo and the page that displays looks well done also.

[TowPilot]

I'll try my hand at documenting making the shaft too, in response to a PM, here goes, yet another version of making an outer shaft of CF tubing. Good personal practice for tech writing skills :)

Monstermaxx posted his directions and from those, I made just the outer shaft of carbon fiber tubing.
benzee1 has posted directions also.

After a PM asking for more specific directions, I thought a few photos might help people along with making one. There is more than one way to make them, these are the steps I took with photos.




It's fun to make one, install it and watch it fly.

I keep some broken parts, they can be useful to make parts, serving as jigs or to take measurements from.

In this instance, I used a broken lower rotor head as a jig to drill the lower rotor holes needed for the outer shaft. And the slightly bent metal outer shaft as the template for the CF tubing outer shaft. A mainframe bearing was used as a guide to sanding the CF tubing.

The carbon fiber stock comes in rod (solid) and tubing (hollow).

I purchased at the local hobby store, a length of 5/32 carbon fiber tubing for $3.90.
I brought a lower rotor head to the LHS to determine which diameter CF tubing to buy (yet another use for a broken part, as a template). The lower rotor head slipped perfectly over the 5/32's diameter CF tubing. (I knew which size to test right away because Monstermaxx told me which size to use, but, if you didn't know, using the older parts as a fit test is a good way to find out.)

I take photos of components before I turn them into individual parts. Photos are better than my memory of them. Before pressing the metal outer shaft from the gear, note how far into the gear the metal tubing is pressed.

http://www.helifreak.com/attachment.php?attachmentid=58258&stc=1&d=1218262756


Press the bent steel tube outer shaft out of the upper gear and use this section of tubing as the means to measure how long to cut the CF tubing. Use a razor saw and a miter box to get a nice clean square cut. Or make the cut slightly longer than needed and sand with a piece of sand paper over a wood block to get the length needed.

I have one so I used it, a miter box, razor saw and the 3 foot section of 5/32's CF tubing.

http://www.helifreak.com/attachment.php?attachmentid=58260&stc=1&d=1218262592

Making the cut

http://www.helifreak.com/attachment.php?attachmentid=58259&stc=1&d=1218262553


Press the CF tubing into the lower gear to the distance found on the old component.

To determine the drill bit to use for drilling the hole into the CF tubing, see which bit fits into the metal outer shaft hole.

To determine the location to drill the hole into the CF tubing, I used a dial caliper.
I picked up a cheap dial caliper to be able to copy measurements from one part to the next. I am not working from plans so the dial caliper does not need to be expensive. I only need to take the measurement and apply it to the next part. So this cheap dial caliper fills this need nicely, $15 from Mills Fleet Farm.

http://www.helifreak.com/attachment.php?attachmentid=58257&stc=1&d=1218262553

Put the lower rotor head back on the old metal outer shaft. Measure how far it is from the gear to the rotor head, lock this distance in on the dial caliper using the thumb screw. Check the distance as being correct after tightening the thumb screw on the dial caliper.

Put the lower rotor head on the CF tubing and slide it into position using the dial caliper. Carefully snug the two bottom screws of the lower rotor head to hold the head in place. Check the distance to the gear again with the caliper to assure the head did not move.

Drill the hole into the CF tubing using the rotor head as a jig.

http://www.helifreak.com/attachment.php?attachmentid=58256&stc=1&d=1218262553

Press the bearing into the upper gear.

http://www.helifreak.com/attachment.php?attachmentid=58261&stc=1&d=1218263457


The bearing will not be flush with the gear.

http://www.helifreak.com/attachment.php?attachmentid=58262&stc=1&d=1218263569


Slide the brass stepped washer onto the shaft with the step towards the mainframe.

http://www.helifreak.com/attachment.php?attachmentid=58263&stc=1&d=1218263660

The CF tubing may not be perfectly 5/32's throughout the length. The CF tubing may need light sanding with 600 grit sandpaper. Press a mainframe mast ball bearing out and slide the bearing over the CF tubing to check for a good fit for when the CF outer mast is assembled into the mainframe.

Put the bearing back into the mainframe and slide the new CF outer shaft into the mainframe, making sure the stepped brass washer is on the shaft with the step facing the mainframe.

http://www.helifreak.com/attachment.php?attachmentid=58264&stc=1&d=1218263729

Slide the collar into position, remove the screw from the collar and use the collar as a jig to drill the hole for the collar set screw into the CF tubing.

http://www.helifreak.com/attachment.php?attachmentid=58265&stc=1&d=1218263835


That's it, you now have a CF tubing outer shaft and upper gear component.

The gear in the photo is white because I painted the gear black after assembly. Well, actually not, but that is my story and I'm sticking to it :DOH

I choose not to make an inner shaft using CF. The torque and clamping by the lower collar set screws tends to cause the lower end of a CF inner shaft to shred and fail.

I've never bent a steel inner shaft but I keep the CX2 subsonic in the lower Mach numbers.