Fun, Learning, Friendship and Mutual Respect
START  HERE


Unregistered
Go Back   HeliFreak > R/C Helicopter Support > 250 Class Electric Helicopters


250 Class Electric Helicopters 250 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar.


View Poll Results: What is the weight of your 250?
less than 320g 54 17.31%
320g to 340g 103 33.01%
340g to 360g 92 29.49%
More than 360g 65 20.83%
Multiple Choice Poll. Voters: 312. You may not vote on this poll

Reply
 
Thread Tools Display Modes
Old 06-23-2016, 05:52 PM   #221
CraigHB
Registered Users
 

Join Date: Dec 2014
Location: Reno Nevada
Default

You can actually shut off the over-current detection through the CastleLink software. In that case it will put out current until the switches burn out. You wouldn't know it until the ESC quits working permanently. Still I believe in having some head room. I'd rather take the weight penalty and provide some margin to be assured things will stay cool. It's also better for efficiency. I get pretty good flight times with the motor and ESC I'm using even though it adds 15 or 20g.

For example the motor I'm using has about 30mΩ resistance compared to 75mΩ for the stock motor. At 20A that's 30W wasted in copper loss for the Align motor versus 12W wasted for the 4000Kv motor I'm using. There's also the difference in heating which further adds to the disparity in resistance. All in all it's enough of a difference to have a pretty noticable impact on flight time. The same is true for the ESC, the Talon 25 has lower resistance than the Talon 15, but not to the same degree as the motors.

Another limitation comes with the Kv of the motor. The best you can do is about 90% nominal voltage times Kv. On 3S the stock 3600Kv motor even with a 16T pinion is not going be able to put out more than about 4800 rpm head speed and that will fall off as the battery discharges and voltage gets lower. The only way to increase speed after that is to increase Kv with a motor rewind or use a higher voltage battery. Anyone who is saying you can get 5500 rpm head speed with the stock motor on 3S is either full or it or has found a way to defy the laws of physics.

There's also the issue of gearing. Surely you could go even higher than 16T to get a speed theoretically higher, but that just won't work. You get to a point where torque delivered to the rotor is not adequate to overcome drag created by increasing head speed. There's also the electrical issue of increasing currents as torque demands increase. There's a point of no return where current keeps going up without any increase in torque. As it is the stock gearing takes it to the limit at 8:1. With the bigger, higher torque motor I could probably run 7.5:1, but I won't go that tall. The torque for it really isn't there even with a bigger motor. Running that tall ratio takes a bite out of efficiency since you get to where current goes up with less increase in torque.

Last edited by CraigHB; 06-23-2016 at 07:20 PM..
CraigHB is offline        Reply With Quote
Old 06-23-2016, 08:28 PM   #222
Number
Registered Users
 

Join Date: Jun 2015
Location: Missouri
Default

I have a 14T pinion. You know of a higher Kv motor with a 2.5 shaft?
Number is offline        Reply With Quote
Old 06-24-2016, 01:02 PM   #223
CraigHB
Registered Users
 

Join Date: Dec 2014
Location: Reno Nevada
Default

I don't have anything to recommend other than motor I'm using. Motors and pinions for the 250 are hard to find. The shaft sizes are not common and the 0.4 mod pinions are not common. The motor I'm using actually has a 2.3mm shaft and I was able to find a 0.4 mod 15T pinion for it. I have pinions smaller and larger for that motor, but as I said I would not run any taller than the stock ratio. Though for really high head speeds you have to go taller to keep motor rpm in the correct range.

It's important for efficiency to run motor rpms 70 to 90% of nominal voltage times Kv. You also want the motor to spin 30k to 40k rpm, lower for bigger motors higher for smaller motors. If motor rpm is too low efficiency may suffer, if motor rpm is too high bearings can wear quickly and vibration may be excessive.

It's not always easy to find a motor with ideal Kv you need for the speed you want to run. About the only way to get things perfect is to find a motor that's right in terms of mechanical fit and rewind it yourself for the Kv you want. I actually rewound the motor I'm running. It was originally 3400 Kv and I rewound it to 4000 Kv.

I just remembered, I did see a 2.5mm shaft motor with higher Kv that might work, though it might be too wide, this one; http://www.scorpionsystem.com/catalo...HK-2206-3900KV
CraigHB is offline        Reply With Quote
Old 06-24-2016, 01:29 PM   #224
Number
Registered Users
 

Join Date: Jun 2015
Location: Missouri
Default

The 2206 was designed for the 250, it would be perfect. But, it's really expensive, so I haven't bought one.
Number is offline        Reply With Quote
Old 06-24-2016, 06:17 PM   #225
nflanagin
Registered Users
 

Join Date: Oct 2010
Location: Northbrook, IL
Default

The scorpion is rated:
Max Continuous Current14 Amps
Max Continuous Power150 Watts

The align is rated:
Max Continuous Current: 16/24A (5 sec.)
Max Output Power: 170/250W (5 sec.)

The align motor is more powerful. But, I do use the pinion pack.
http://www.scorpionsystem.com/catalo...ar_1/04pinion/

which has a 14t, 15t and 16t mod .4
__________________
Agile 5.5, X5, Trex 450proV2, 250DFC #309
nflanagin is offline        Reply With Quote
Old 06-25-2016, 03:27 AM   #226
CraigHB
Registered Users
 

Join Date: Dec 2014
Location: Reno Nevada
Default

You can't always compare manufacturer ratings since they don't always use the same standards. I'd say the Align motor may or may not be more powerful, you'd have to bench test them next to each other to get a reliable comparison. The Scorpion motor does have higher Kv which will provide an increase in head speed 400 to 450 rpm depending on gearing. Also motor power is a function of Kv. Higher Kv increases current demand and thereby power.

Stator size is usually a good gauge for torque output of a motor. In this case it's 22mm x 6mm for the Scorpion motor versus 19mm x 8mm for the Align motor. In terms of volume they're almost identical.

I just checked on my 250 since it's sitting next to me on my desk right now.The width of the frame is barely over 28mm so it would be a tight fit. There's a chance it may not clear. Possibly a little filing on the frame cutouts might be required.
CraigHB is offline        Reply With Quote
Old 06-25-2016, 12:42 PM   #227
Number
Registered Users
 

Join Date: Jun 2015
Location: Missouri
Default

This is Scorpion motor.

All I'm saying is, there's no way you could do this with the Align 250 motor.
Number is offline        Reply With Quote
Old 06-25-2016, 09:04 PM   #228
CraigHB
Registered Users
 

Join Date: Dec 2014
Location: Reno Nevada
Default

Finally got a nice calm day and flew the 250 through all its packs. First real test with the Lynx servos. No issues, the heli actually feels better. Had to turn gains up a tad, but after I got it adjusted it feels really nice, tighter more precise.

That was 36g of unneeded weight I got rid of going with the Lynx servos. Plus I lost 10g by ditching the case for the BeastX and another 8g with the plastic canopy. So it's a ~lot~ faster after losing that dead weight. I actually like the plastic canopy better, it's easier to get on and off. That fiberglass canopy was kind of a bear.
CraigHB is offline        Reply With Quote
Old 06-25-2016, 09:42 PM   #229
HeliLust
Registered Users
 

Join Date: Jan 2015
Location: Central New Mexico
Default

Awesome, I'm glad you got to test I was thinking of doing the same thing with the lynx servos, but decided not to.

I've ditched the canopy all together for the time being but I have a plastic full fuse being made up for it special. I still don't quite have mine dialed in but it's getting close. I like the lightweight build it crashes like a feather. I've even had a couple emergency auto's that came out unscathed with it and one that broke a landing gear strut.
__________________
Helis: Trex 250, Oxy3 +, 450 se v2, 450 pro, 470, 480N, 500 ESP, 700N
Team Align Enterprise Hobby Facebook Align Part Finder
HeliLust is offline        Reply With Quote
Old 06-26-2016, 02:46 AM   #230
CraigHB
Registered Users
 

Join Date: Dec 2014
Location: Reno Nevada
Default

I had a hard landing out flying today, thought I might have cracked the landing gear but it didn't. Probably would have at its previous weight.

Oh BTW I wanted to see if flight time improved so I ran one pack all the way to ESC low voltage cutoff at 3.4V per cell. It ran for 8 minutes 40 seconds flying mild sport. That's up almost a minute from what it was before. I normally run the timer down from 6 minutes and that now leaves the battery about 75% discharged. I don't actually like to fly much more than six minutes at a time anyway or I get tired and make mistakes. I think that's pretty good run time for an 850 mAh battery. I think I can call that an efficient setup.
CraigHB is offline        Reply With Quote
Old 09-14-2016, 05:24 PM   #231
bazsound
Registered Users
 

Join Date: Jul 2013
Location: Scotland
Default

Quote:
Originally Posted by Number View Post
This is Scorpion motor.

All I'm saying is, there's no way you could do this with the Align 250 motor.
Super Insane T-Rex 250 with 5500 RPM Headspeed - YouTube
that video look like i has beeen sped up.
bazsound is online now        Reply With Quote
Old 09-14-2016, 09:35 PM   #232
Yfbb
Registered Users
 
Posts: 1,530
 

Join Date: Apr 2011
Location: Lexington Ma United States
Default

Quote:
Originally Posted by bazsound View Post
that video look like i has beeen sped up.
Doesn't it? Thing is my 250 with the same motor and setup pretty much flies like that too. I just don't get how he does tick tocks. Mines just flops and drops. Probably a setup issue.
Yfbb is offline        Reply With Quote
Old 09-14-2016, 11:12 PM   #233
Number
Registered Users
 

Join Date: Jun 2015
Location: Missouri
Default

Definitely not sped up. The sounds are totally normal. I was able to do fast tic tocs with my 250 all day, just look for the thread "my 250 build" and the videos in it. I loved that heli, even with the Align motor.
Number is offline        Reply With Quote
Old 09-15-2016, 09:44 AM   #234
myxiplx
Registered Users
 

Join Date: Apr 2013
Location: UK
Default

Nah, not sped up, if he flew slower than that he wouldn't crash so much :-D

A lightened 250 has plenty of power to do tic-tocks, but you've got to be super precise with your timing. Mine have never been anywhere near as accurate as Keith's.
__________________
Backyard fun: Trex 250 SE with VX1e
At the field: Gaui X3 360mm + Gaui X3 380mm, with VX1n + VX1e | Trex 600N with VX1n
TX + Sims: Jeti DS14 and Realflight (Wireless)
And now a Lynx Team Pilot :-D
myxiplx is online now        Reply With Quote
Old 12-13-2016, 01:40 AM   #235
bazsound
Registered Users
 

Join Date: Jul 2013
Location: Scotland
Default

Bearing in mind this is using a super cheap not so great mechanical scale really only meant for weighting flour suger in small amouints that also doesnt like to centre very well.

After measuring multiple times, mines tlooke to be around 340g.

Im using turnigy tgy-213c servos for cyclic and turnigy tgy-306hv on the tail, Nice looking servos perform well but are heavy, cyclics are 16g each and the tail is 23g. If i moved to the 7.6g servos id save 40g right away.

Im also using the FG copterx canopy so theres some more weight i can save.

Im using a mini bar with no reciever, instead a lemon rx sat which is 3g so i saved some weight there (had an ornange rx before which was 12g)
bazsound is online now        Reply With Quote
Reply




Unregistered
Go Back   HeliFreak > R/C Helicopter Support > 250 Class Electric Helicopters


250 Class Electric Helicopters 250 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar.

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


Copyright © 2004-2016 by RCGroups.com, LLC except where otherwise indicated. The HeliFreak.com logo is a trademark of RCGroups.com, LLC.