View Full Version : 300x tail upgrade for the SR ?

04-03-2012, 02:32 PM

I just did of list of part for belt drive upgrade.

We just need to know if the main shaft is still 4mm and if the tail boom is the same lenght otherwise it may be fit.

here is the parts list for only 147$ (Boom strike will hurt a lot)

BLH1651 Main Gear (2): B450/X, 300 X 9.99
BLH4513 Main tail Drive Gear (2): 300 X 7.99
BLH4514 Main Gear Hub: 300 X 4.99
BLH4521 Belt Guide Cross Member Set: 300 X 6.49
BLH4523 Tail Drive Belt: 300 X (not shown) 5.99
BLH4525 Tail Boom Brace/Support Set: 300 X 5.99
BLH4526 Tail Booms (2): 300 X 6.99
BLH4527 Tail Pushrod Support/Guide Set: 300 X 4.99
BLH4528 Tail Servo Boom Mount (2): 300 X 3.99
BLH4529 Tail Linkage/Pushrod (2): 300 X 4.99
BLH4530 Stabilizer/Fin Set, White: 300 X 5.99
BLH4531 Horizontal Stabilier/Fin Mount: 300 X 3.99
BLH4532 Tail Case: 300 X 4.99
BLH4533 Tail Rotor Pitch Lever Set: 300 X 7.99
BLH4534 Bearings 3x7x3 (2): 300 X 5.99
BLH4535 Tail Rotor Shaft and Drive Pulley (2): 300 X 4.99
BLH4536 Tail Rotor Pitch Control Slider Set: 300 X 5.99
BLH4537 Tail Rotor Blade Set: 300 X 3.99
BLH1670 Tail Rotor Blade Grip/Holder Set: B450, 300 X 4.99
BLH1612 Tail Rotor Thrust Bearings: B450, 300 X 6.99
EFLH1115 Bearing 3x6x2.5mm (2): 300 X 5.99
BLH4540 Aluminum Tail Rotor Hub Set: 300 X 3.99
EFLRDS76T 7.6-Gram Sub-Micro Digital Servo- TR 18.99

At this price I will stay with the stock tail motor.

04-03-2012, 03:15 PM
I would have thought the frames of the SR and 300X are pretty different as well. Not that I wouldn't like this mod for the SR.

04-03-2012, 04:04 PM
Sure, you might be able to do this... but why? Aren't their belt drive tail conversions already available?

R_C Addict
04-07-2012, 07:38 AM
To the Op.
There is a belt driven tail rotor kit available for around $85.00 plus shipping from
They offer everything you need to do an easy conversion.

04-07-2012, 10:41 AM
Suggestion,,heli-world has a hummingbird pro kit with a shaft drive tail.65 bucks.same size heli pretty much.
Lost my mind n bought a v40002.
Going to play around with a 12mm brushless inrunner can and see how that works.
i own a hbfp to and tail motor si cftuation has always been a hassle.Plus the esky 3 in one is not so good either.
Just like to tinker yo much i guess.saw a you tube vid that had a brushless on an sr tail with a cp tail set up.
be fairly cheap to do with a little ingenuity.

04-22-2012, 12:59 PM
I was wondering if this same thing would work as well. If it will work at least one will be able to walk in and get parts for it which is always a plus. The Boom looks larger on the 300X though and Blade never tells you the size of anything.

The SR's head speed needs to be up a little too. According to dark horse headspeed calculator, the head speed for the new 300X will be right at 2900 RPM. Thats with a 10 tooth pinion, 155 main, 4500KV motor and 3S lipo at 90% efficiency. I don't know that that is what gears the 300X has but it does have a 15.5:1 gear ratio which matches 10/155.

My SR is running 2597 head speed right now with a 10 tooth pinion, 150 main, 3S lipo 3900 KV motor at 90% efficiency.


04-30-2012, 01:13 PM
The 300 X is a scaled down 450 X and most of the shared parts are coming from this basket of parts. I don't know how feasable any of what it being talked about here is really going to be....:thumbup:

04-30-2012, 03:37 PM
Why would you want to put a belt on an SR when they are coming out with a TT tail (which performs more consistantly than a belt) on the 130X?? :confused:

I dont think you save money doing it that way neither.

05-16-2012, 10:12 AM
Why would you want to put a belt on an SR when they are coming out with a TT tail (which performs more consistantly than a belt) on the 130X?? :confused:

I dont think you save money doing it that way neither.

Who is coming out with a "TT" tail? Exscuse my ignorance but what does that acronym mean?

05-17-2012, 07:49 AM
"TT" stands for torque tube. It's like a belt tail only a geared shaft is ran down the tail to drive the rotor instead of having a belt. Blade 130X will have this tail setup

05-19-2012, 03:53 PM
I wonder if this heli can take my Scorpion 3400kv from the gaui x2 that was spinning 4000+rpm?
Based on Mr. Mel's headspeed calculator with 155 main gear mentioned above stock push fit 15 tooth pinion, 3s 90% efficiency 100% throttle i will get
Beginning rpm: 3877
Middle rpm: 3571
End rpm: 3466
That sounds good enough, as the gaui X2 was simply too balistic with 4000k rpm, and i'm assuming the 300x will need a metal head upgrade for that kind of headspeed.

05-23-2012, 02:14 PM
I found that speed calculators should only be taken lightly. Gears have different mods which in turn changes circumference, not to mention the other variables such as resistance, mass, motor timing, etc.

Freestyle's prices are in Australiana dollars, so if you are paying in US dollars, expect it to be more. Shipping is also alot from Freestyle.

Lesson learned on my end - Don't try to change the bird. You are better off buying a new one. 450 helis are very common and prices even run better than 300 sized helis for parts. You also don't have to mod much as 450 clones are a dime a dozen. $150 dollars is very close to getting you a new 450 flybar heli that will handle much better than your modified 300 that may or may not work.

05-28-2012, 01:49 PM
Understood, Gaui x2 was tached 4100, but then it was a mod 0.4 gear train, i do have some 2.3mm 0.5mod in hands already though to try with the 300x.