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Old Feb 20, 2012, 02:25 PM
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Build Log
120 SR Brushless Conversion - Part 1

I basically followed the MCPx brushless mod setup with a few minor differences. The mcpx uses a .3 Mod pinon (I think) but for the SR 120 we need a .4 Mod pinion. The mcpx guys swap to the SR 120 tail so we are good there.

There are a few different ways the mcpx guys are wiring things up, specifically where they are wiring in the theSteve converter. The easiest and they way I have it for now is to run the blue(-) and Yellow(+) soldered to a jst connector and plugged in where the brushed motor was. The red and white wires go to the servo plug of the esc and match the wire colors of the esc. The esc has a mini servo connector, I had some on hand so I used one to make the connection between the theSteve and the esc. For power the esc needs to be connected directly to the battery leads, the esc uses a walkera Micro Plug. I have some batteries that had the right female connector so I salvaged one and soldered the leads to the battery lugs on the 5-in-1 (this is the only permanent alteration to the electronics).

The current motor is from a walkera V100D. I just drilled some new holes and mounted it. Hard part is swapping the pinion gear. The shaft is 1.5 mm and easy to bend a pinion puller is required. Even then it's no picnic. If you can find a micro brushless without a pinion I'd recommend it.

Todo:
I think I am way over geared, the pinion I have is a 14 tooth and I think it is overworking the motor which is too hot to touch after a few minutes of flight. The motor is a $5 used motor I got on ebay so it might of been overheating before. Now that I know this will work I'll probably buy a better motor. I need to try the resistor mod that the mcpx guys do to see if it smooths out the throttle curve at start up. I'll probably solder everything directly to the 5-in-1 to get rid of the plugs and extra wire.


Parts:
theSteve Converter
Heli-Max Brushless ESC Novus FP/CP HMXM3005
HM-V100D03BL-Z-07: Brushless Motor for Walkera V100D03BL Helicopters (see issues above)
Female Jst (salvage)
Female walkera Micro Plug (salvage)
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Last edited by Zr_Flyer; May 20, 2012 at 04:44 PM.
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Old Apr 09, 2012, 06:15 AM
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I tried to do something similar using an "Xtreme brushed to brushless converter" and an "Aeolian XP-7A" ESC. Unfortunately I cannot get it to work: The ESC always initializes with a "low" throttle signal - even when I am on "full" throttle (consequently I also cannot get the ESC into programming mode). Meanwhile I got two sets of converter/ESC and they both show the same behavior :-( Any ideas what might be the problem?
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Old Apr 09, 2012, 09:14 AM
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Hi,

I ran into the same problem. I was able to get my esc into programming mode by adjusting the throttle end point above 100% on my TX but then I was not able to get any further because it would not send a 0% signal to the esc. I figure if I really want to program my esc I will need a programming card or will plug it into one of my 6 channel Rx's. The way it is the default values on the esc are working for me, most default to normal start, no brake etc. which is what we want, I just wanted to play with the timing on mine.

I need to update on my progress soon, I have mine flying pretty well. I finally got an 8 tooth pinion that works pretty good.
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Old Apr 24, 2012, 07:47 PM
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Hey, thanks, Zr, for this info. I was trying to determine what size brushless I should invest in. Did you have a lot of room with mounting this motor? It doesn't look too big.

Sax
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Old Apr 25, 2012, 04:52 PM
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There is plenty of room. There is an issue with this size motor in that the mounting holes are close together and fall right on the edges of the existing pinion hole. I ended up making my one base out of a trex 250 gyro plate, works pretty well and snapped into the 120 frame with very little modification. If you're going with 2S there are more options for motors, like maybe the 130x one.
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Old Apr 25, 2012, 06:13 PM
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Oh, that's good. That's a fiberglass or CG plate?
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Old Apr 25, 2012, 07:59 PM
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It's carbon fiber.
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Old Apr 25, 2012, 09:03 PM
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It's carbon fiber.
That's what I meant--not CG, CF. Was it shaped to fit as you show in the picture or did you trim it?
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Old Apr 25, 2012, 11:12 PM
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The 250 gyro tray is not trimmed at all, I was amazed at how good of a fit it was, the rear of the plate has those indents that lined up perfectly with the curve of the 120 frame, it actually snaps in there and holds. Only mod is the hole and slots to mount the motor.

The 120 frame is modified, first by gravity, I had a battery tray attached to the front of the frame holding a 850mah battery and it snapped off at the landing gear holders on a hard landing... Then to get the gyro tray to sit flush I removed some of the lip on the underside of the frame. I used 3 small screws to attach the plate to the 120 frame, 1 in the back and 1 ea. to the frame near the front landing gear holders.
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Old May 14, 2012, 08:31 PM
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The 250 gyro tray is not trimmed at all, I was amazed at how good of a fit it was, the rear of the plate has those indents that lined up perfectly with the curve of the 120 frame, it actually snaps in there and holds. Only mod is the hole and slots to mount the motor.

The 120 frame is modified, first by gravity, I had a battery tray attached to the front of the frame holding a 850mah battery and it snapped off at the landing gear holders on a hard landing... Then to get the gyro tray to sit flush I removed some of the lip on the underside of the frame. I used 3 small screws to attach the plate to the 120 frame, 1 in the back and 1 ea. to the frame near the front landing gear holders.
I went ahead and ordered the gyro tray as it would cost as much or more to start with a uncut square. I'm excited to get all the parts together because I think I'm going to really make this a super heli. I've been trying and trying to figure out what motor would be an upgrade for the tail. I think that I've decided that the mCP X main motor may work. Have you tried any other tail motors?

Sax
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Old May 15, 2012, 07:22 PM
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Cool, I think the tray will work well for you. I haven't really thought much about the tail motor, as it is the tail works pretty good with the stocker. Many of the modded mcpx's that have gone bl are running the 120 tail motor. I do have a 5 amp esc laying around, maybe I'll see if I can scavenge a motor from a cd rom.

As it is the 120 is flying ok but I am having problems with the low end of the power curve, if I want to lower the altitude most of the time the motor stops and I have to gun it to stay in the air. It's like an on off switch. I've ordered this 2s motor http://www.hobbyhot.com/SWANGHOBBY-3...ess-Motor.html , should be here this weekend. It has a 2mm shaft so it will be much easier to try different pinions and ratios.
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Old May 15, 2012, 07:36 PM
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You are going to think that I'm nuts (I am ), but this is what I ordered for a motor. As I said earlier, I'm going 2S on this baby along with micro servos and separate RX, ESC and gyro. I'm cranking this puppy up to max!!! I do like the motor you ordered. Please let me know how it works because I think I could upgrade another with that one.
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Old May 15, 2012, 11:10 PM
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You are going to think that I'm nuts (I am ),
Haha, agreed

Looks like you should be able to make it fit, can't wait to see this monster.
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Old May 16, 2012, 07:04 AM
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Haha, agreed

Looks like you should be able to make it fit, can't to see this monster.
Yeah - My intent is to a) use my old CX3 parts and b) lift the UH-60 Blackhawk body I had for it. I could not get my other heli to work right and the stock 120 is weak. So, there I go!
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