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Old Jan 14, 2012, 07:36 PM
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Blade 120SR: Scale Bodies

Throughout the 680+ page Blade 120 SR thread (with over 10,000 replies!) there are quite a few posts about fitting scale bodies, but it's high time to have a thread dedicated to this endeavor.

The fantastic 120 SR has been out for over 1.5 years; that the main thread continues to attract multiple daily posts speaks to it's winning combination of durability and excellent flight characteristics right out of the box, with only relatively minor performance gains to be found through modifications.

Still, some like me can't resist trying to make the 120 look more like a real helicopter. The stock body (while durable, light, and by no means ugly) just doesn't cut it.

There are a number of scale bodies made for other helis with similar ~12.5"/320mm main rotor diameter (like the CX2/3, LamaV4, Kestrel etc) that can be fairly easily adapted to the 120.

Feel free to post questions, or what you've done or plan to do!

ridgewalker made a beautiful CX2 Jet Ranger body work with the 120: http://www.rcgroups.com/forums/showp...postcount=1577
As did Mr. Firemouth http://www.rcgroups.com/forums/showp...postcount=8610

Fabio1970 adapted a sweet Kestel 500SX fuse (all-in weight 141g!) and posted excellent in-flight videos:
http://www.rcgroups.com/forums/showp...4&postcount=11

bulbsrtw printed, folded, fitted and flew a very convincing paper(!) AH-1S Cobra, $10 plans available here: http://www.modeltek.com/cardcobra.html

JLT GTI used a Bell 412 TwinHuey originally intended for the ESky Lama A300: http://www.rcgroups.com/forums/showt...1293580&page=4
http://www.rcgroups.com/forums/showp...6&postcount=63

scottgregory74 fitted a UH-1 Huey from a coax here: http://www.rcgroups.com/forums/showt...hlight=awesome

tracknoob has a great looking MIA MD500E here: http://www.rcgroups.com/forums/showp...&postcount=558

Mad-heli-genius Erdnuckel has a bada$$ SH-60 Seahawk on the way from heli-scale-quality.com in Germany and promised to post details on his experiences.

Did I miss any others?

Tonight I flew my 112.5g Robinson 120 SR for the first time.
Mods:
- Xtreme 120 motor soldered directly to PCB leads (eliminated 1.5g in wire and plugs)
- Rakon swash (looks great, and double ball joints on the servo-to-swash links for extra adjustability, but otherwise no real performance gain IMO)
- Tiger 600mAH battery. I will likely cut the very long lead down on these once final placement is determined.

Initial impressions are VERY satisfactory, will be moreso after the following tweaks:
- Center of Gravity (cg) is a bit too far back. Flew well with a 6g washer taped to the nose, will remove the 0.7g PCB cover, plastic tail motor cage, move battery as far forward as possible etc to reduce the need for ballast. Maybe mount my keychain cam to the nose?
- with tail motor ~25mm further away from frame vs. stock the tail prop could be cut down a little bit so yaw response isn't quite so dramatic
- I melted/burned holes in the body's tail to accept the tail motor, and right now just have the motor 'strapped' in with a strip of electrical tape. Need to figure out a more permanent, better looking solution.

Even so, she looks AWESOME in the air, flies basically like a stock 120SR, and I'm not tempted to try anything too radical for fear of crashing, so I can work on my basic (i.e. scale) flying skills



Body mounts will likely need lengthening for whatever you chose. The 2mm carbon rod you'll need to make use of the stock frame holes is available online or at a well-stocked LHS .



CG will be a critical factor. Many scale bodies have elaborate tails, unlike the stock blade, so care will need to be taken to move the frame back in the body, shift the battery as far forward as possible, and maybe even add ballast to the nose.

Be careful to mount the frame high enough so the flybar won't strike the body.

I don't know the max weight the stock 120 can lift, but I ran a test with the stock motor and it easily lifted the 15.2g Robinson body:



With an Xtreme motor even 25g bodies like the Dauphin shouldn't be a problem. That Fabio's 141g Hughes 120 flies quite nicely shows that she can handle quite a bit!

The stock 120 weighs 106g all-in.
Stock 120 body and tailfin weigh 6.7g

I bought 3 bodies from XHeli:
$13.50 Dauphin, 22.3g (remove fake tail rotor and LED): http://www.xheli.com/ek1-0604.html
$12.95 Robinson, 15.2g: http://www.xheli.com/ek1-0556.html
$3.30 Eurocopter 20.6g:
http://www.xheli.com/ek1-0696.html





For landing gear I ended up using ~$6 Blade CX3 parts found at the local hobby store.
The 120's LG mounting holes don't quite match up. For L/R you can just enlarge the outside of the holes in the rear gear crossmember a little bit (I heated an old 1/16 drill bit with a torch, melted the holes 'outwards' a little bit and then cleaned up with Exacto knife) and use aluminum bolts after tapping the frame mounts, or other methods. Front/back the CX3 gear mounts are about 15mm longer than the 120 frame, so I cut down the battery holder and drilled holes for aluminum screws as shown here:



Dream Heli Products also makes nice looking, Hughes-type gear for the CX3 that could be adapted to work:


I decided to use the CX3 gear for the first go, we'll see how durable they are (skids screw to the supports vs. fully molded plastic with the DHP).

You could also stay with the stock LG. They don't look very scale but if you're unsure it wouldn't be bad to fit a body around the frame, flybar/blades and tail motor, make sure she flies, and worry about the gear later.

Let's see what you can do, or already did!




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Last edited by Kurt; Jan 21, 2012 at 09:23 AM. Reason: updated with links to tracknoob, JLT GTI, and scottgregory74's helis
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Old Jan 16, 2012, 05:42 PM
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United States, TX, Houston
Joined Sep 2003
1,868 Posts
Not my best day as a pilot, but had a couple fun flights outside today:

Blade 120SR Robinson outdoor (HD) (3 min 43 sec)


Also tested the Eurocopter body on the frame while I was working on it over the weekend. Fit very well!
I almost have enough parts to build another flyable 120 chassis for this body, just need a main shaft, flybar, and of course another (nose bleed-pricey) PCB....
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Old Jan 18, 2012, 03:58 PM
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United States, TX, Houston
Joined Sep 2003
1,868 Posts
Fabbed up a new battery mount out of I-section polystyrene, shortened the leads on 3 Tiger batteries and had a few good flights (and a couple crashes) today. Body is holding up well to the knocks!

Also edited the first post to include links to posts I found with excellent scale bodies by tracknoob, JLT GTI, and scottgregory74.


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