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View Full Version : My rebuild (BL + RKH frame)

brianp6621
07-31-2011, 04:54 PM
So my RKH frame came in on friday so I decided it was time to do my BL conversion. I finally completed it last night and flew it for the first time today.

Here is a run-down of my bird as she exists now, after the rebuild.

RKH Frame w/ boom supports
MH Swash
MH grips (mine are really nice, not sloppy like others complained, very happy with them so far)
MH tail holder/carbon fin
MH rotor hub
hardwired large gauge tail wires
AeoRC CO5M w/1mm shaft
8T stock pinion
AeoRC 5A ESC
Old style(not the new mCPX version) TheSteve converter
Everything else not mentioned is stock

With all of this installed and a NT batt, the AUW is 45.66g
The oldest baseline I have on my heli is 46.2g (with the stock battery and completely stock)

Pretty darn good if you ask me, lots of significant performance upgrades and 0.5g lighter than stock.

Now some info about the upgrades.

My BL mod
I mostly followed Matt Bockmans walkthrough. http://mattbockman.com/?p=6
I removed the main motor connector on the 3in1, just like I did with the tail connector. I soldered a 2.2kOhm 1/8w resistor(I went with 1/8w since the posts were small enough to solder directly through the board making attachment easier, i hope it is big enough) between the motor terminals and the yellow wire of the steve to the + motor terminal. I soldered the motor and thesteve directly to the ESC. I soldered the red from thesteve to where the small red from the ESC was, the white from thesteve to where the small white from the ESC was, and the blue from thesteve to where the small black from the ESC was. Then the ESC red and black were directly wired to the main power/battery posts (red to white and black to black)

Everything seems to have gone well but I'm not sure about 2 things.

1. I don't have much throttle control. The throttle seems to mostly respond from around 15% to around 45%. Above 45% it seems maxed out. This was gauged when I didn't have any blades installed. I have seen others make comments about this and even say the stock motor acts somewhat the same way. I'm not too sure it matters much as I always fly in idle up but I'm curious if something is wrong.

2. This may be related to #1 but I don't have much of a soft start. It starts up very fast. I don't have any way to program the ESC, but what is the default setting? Are others seeing this?

Now, my observations on the the BL mod.

WOW, very different heli. Ok, not as much power as I expected and I'm still getting some head slowdown (not really bogging) but it is still great.My head-speed on a new battery is around 4900 rpms.

I love the quietness and the sound of the BL motor.

I am getting equivalent flight-times (with my type of upright flying) to the stock (5mins) and very even performance across the battery with very little dropoff. The whole heli is MUCH smoother and very predictable and easier to control.

The tail is LOCKED in (note I don't do much 3D and haven't taken it inverted with the BL yet) but in all upright I did, I never saw the slightest issue with the stock + extended tail. I am VERY happy with how it feels

So overall I am extremely pleased with the upgrade. It isn't ridiculous power but it really make it a different heli.

RKH Frame/boom supports

Overall I'm very happy with the frame. It seems stiffer and more serviceable with 1mm CF rod as the canopy pins and hopefully other parts replaceable from RKH. I did seemingly measure it as 0.5g heavier (take this as a grain of salt until independently verified) but I feel it is worth it.

1. Don't ever take it full apart/all servos or shipping placeholders out at once. It makes it much trickier to put the servos back in.

2. I tried using a new 2mm CF rod for the tail (replacing an older slightly beaten up one) and it seemed really hard to get it into the tail boom mount. In slight haste to get it together, I used the old one with the notch cut out (which shouldn't be needed) and it went in easier. So I don't know if the mount is slightly small or the CF rod I have, is slightly large.

Everything else so far about it is great. No other real feedback yet.

Well I think that's it for now. I'm very happy with how she's flying now.

Ok some pictures.
http://www.pbase.com/image/136864274/large.jpg
http://www.pbase.com/image/136864275/large.jpg
http://www.pbase.com/image/136864286/large.jpg
mCP_X
07-31-2011, 05:30 PM
Great job
thank you for the writeup and photos
liftbag
07-31-2011, 05:47 PM
2. This may be related to #1 but I don't have much of a soft start. It starts up very fast. I don't have any way to program the ESC, but what is the default setting? Are others seeing this?
It seems that the built-in 3 in 1 soft start is active if turning off the hold switch when the throttle channel has a value greater than 55%.

The nanoheli guys have a lot of experimentation on brushless conversion, and they claim that by taking the signal directly from the motor output, even with 2,2 K resistor, does not lead to good results because the signal is too dirty.

In my experience, using the tiny resistor hotspot, expands the useful range of the throttle curve, so you can have a flat stunt curve greater than 55% and consequently the built-in 3 in 1 soft start.
brianp6621
07-31-2011, 05:56 PM
It seems that the built-in 3 in 1 soft start is active if turning off the hold switch when the throttle channel has a value greater than 55%.

The nanoheli guys have a lot of experimentation on brushless conversion, and they claim that by taking the signal directly from the motor output, even with 2,2 K resistor, does not lead to good results because the signal is too dirty.

In my experience, using the tiny resistor hotspot, expands the useful range of the throttle curve, so you can have a flat stunt curve greater than 55% and consequently the built-in 3 in 1 soft start.

Good to know. I am going to leave as is for now but if something goes wonky or I break it and really have to redo it, I'll try the resistor spot.
dbennettya
07-31-2011, 06:34 PM
Looks like your experience is very similiar to what I had on my first try except I used the tiny connect point for the Steve. I built a second BL mCP X and used an XP-7A instead of the 5A AeoRC ESC and it flies much better with the C05M with 8T pinion and makes better power with the XP-7A ESC.

I just ordered another XP-7A for my mCP X with the HP05S to see if it improves also.

Good Luck, Don
brianp6621
08-01-2011, 11:52 AM
As a followup I decided to dial in my indoor setting (and by indoor I mean really just hover and slight movement in my living room/kitchen, not indoor gym style flying) to the new BL setup. I found that due to the extremely limited range of throttle right now, 15% throttle gets me a much more manageable headspeed indoors, so my indoor flight mode has a flat 15% throttle curve. It is VERY stable and managable indoors. Much so than ever before.

I noticed indoors especially, that I no longer have apparent pitch/throttle inconsistencies. With the stock setup, hovering indoors I'd have trouble maintain a constant altitude with unexpected drops/rises with no input changes. This is all gone now and I could touch down on the counter-top with the lightest of a touch if I wanted.

Very pleased. It is nothing like that nanoheli setup in the other thread but the control/consistancy/power it does add is a huge improvement.

I am not too worried about the limited throttle control of the extra gains from a 7A ESC so I'll leave as is for now unless I have good reason to monkey with it again. I just want to fly now.
brianp6621
08-01-2011, 03:34 PM
I'll add one more note, I decided to give the KBDDs one more try today as I really like the white and the foldability of them. Again, a no go. They just rob too much collective from the heli. Again, with them everything felt more sluggish and I felt the BL semi-bogging more than with the stock blades. Oh well, I give up on them.
755 robert
08-01-2011, 06:33 PM
I'll add one more note, I decided to give the KBDDs one more try today as I really like the white and the foldability of them. Again, a no go. They just rob too much collective from the heli. Again, with them everything felt more sluggish and I felt the BL semi-bogging more than with the stock blades. Oh well, I give up on them.
That is so strange< I have been reading about some with diminished performance using the KB blades.I did not find this to be the case ,before or after my BL conversion.I swapped back to the two stock blade types and even with my cutdown stockers.and the KB's are the best as far as precise cyclic, I do not notice any robbing of power or flight times..With my BL setup I am getting 5min strong flight times with or without the KBs.
brianp6621
08-01-2011, 06:39 PM
That is so strange< I have been reading about some with diminished performance using the KB blades.I did not find this to be the case ,before or after my BL conversion.I swapped back to the two stock blade types and even with my cutdown stockers.and the KB's are the best as far as precise cyclic, I do not notice any robbing of power or flight times..With my BL setup I am getting 5min strong flight times with or without the KBs.

Ok, I should revise my statement. The cyclic did not feel sluggish but I'm also not sure they felt more precise, it is the power/collective that feels more sluggish.
brianp6621
08-10-2011, 06:12 PM
I have made a few changes to my setup.

I am now using the XP7A ESC and switched to the small resistor connector point for the yellow wire.

I'm much happier with the power/response that the C05m makes but now I do have some tail blowout (20deg) when going from a hover to a full pitch climb.

The ESC now has near full range control of the throttle whereas before my throttle response was from like 20-45%.

It is clear the XP7A is a better match for these brushless motors but puts us again in the regime where the extended stock tail can't fully hold anymore.
brianp6621
08-15-2011, 03:12 PM
Ok, today was the first time I flew fully in a larger open area with the XP7A controller. It is very clear this is NOT a good match with a extended stock tail. I was getting MASSIVE blowout that I've actually never seen before on my heli.

It is possible my stock tail is also getting weaker as it is still the original motor.

I am thinking I need to quickly do 1 of 3 things.

1. Swap in a new tail motor and see if it helps.
2. Go to an alternate tail motor setup
3. Go back to the 5A ESC.

Edit...
I am retracting this statement in all the threads I posted it in. After some more testing, it looks like the onset of my major blowouts were due to a deformed tail NOT the XP7A. One of the 2 blades was bent pretty flat but it was still a little hard to spot. As soon as I replaced the tail blade, I noticed that it was back to when I first switched to the XP7A, more blowout than with the 5A, more blowout than stock with the ext tail, but not a lot which can't be collectively managed and to me still makes it worth the upgrade to the XP7A for more main power and program-ability.
IanWhitehead65
08-15-2011, 09:46 PM
Ok, today was the first time I flew fully in a larger open area with the XP7A controller. It is very clear this is NOT a good match with a extended stock tail. I was getting MASSIVE blowout that I've actually never seen before on my heli.

It is possible my stock tail is also getting weaker as it is still the original motor.

I am thinking I need to quickly do 1 of 3 things.

1. Swap in a new tail motor and see if it helps.
2. Go to an alternate tail motor setup
3. Go back to the 5A ESC.

Hi,

Have you tried limiting the pitch travel. I have reduced my pitch travel 60% and it will still blow out if you go to max pitch too quickly. However, there is still plenty of pitch punch so I might reduce the pitch travel even further. This has the added advantage of keeping the head speed higher during pitch changes (ie. reduced bogging).

Cheers,

Ibs
brianp6621
08-15-2011, 10:41 PM
Hi,

Have you tried limiting the pitch travel. I have reduced my pitch travel 60% and it will still blow out if you go to max pitch too quickly. However, there is still plenty of pitch punch so I might reduce the pitch travel even further. This has the added advantage of keeping the head speed higher during pitch changes (ie. reduced bogging).

Cheers,

Ibs

I may try that. I'm still at 75% but I think I may just have to do the tail.
brianp6621
08-18-2011, 10:51 PM
I have corrected/updated my statement above about the XP7A being the cause for major tail blowout.