RunRyder - What head speed does the T-REX like

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e-Align T-REX 450-500-600 > What head speed does the T-REX like

motorbikemike
Senior Heliman
Location: aurora CO

I am at about 2400 at 0 pitch with a 2025-4200 and an 8 tooth pinion and the stock wood blades. The heli seems to have ok power but I think it wants more pitch. If I increase the pitch on the blade grips I cant get enough pitch for inverted. I had it set at 9 on top and 9 on bottom(with my MJP carbon pitch gauge) but it would just slowly climb so I poped the links off the grips and turned them in 1and a half turnes each and it was much better but I lost pitch on the bottom. I am at max EPA and my pitch curve is 0 25 50 75 100. I wonder if I am just to heavy? I am using

TP 2100
S BEC
HS 56's all the way around
2025-4200
berg rec.
GY 240 gyro
Mike

11-09-2004 Over year old.

twinsticks
Senior Heliman
Location: South Jersey

I just bought a trex-x and it says on the box 3 D 21 bearings this is not the latest model?

11-10-2004 Over year old.

motorbikemike
Senior Heliman
Location: aurora CO

I think it is the new kit? I just got it 2 day's ago from MODEFOS and it say's it it the new kit's on his site. I will look at the align site to see what I can come up with. All I can say about this kit so far is WOW! The tail is ROCK solid and so is the rest of the heli! It is a little heavy but I am running the 2100 also. I think the 1320 gen 2 will be much better.
Mike

11-10-2004 Over year old.

twinsticks
Senior Heliman
Location: South Jersey

That is were I bought mine from also MODEFOS
Great service .Checked alaign web site it says 21 bearings 3 d

11-10-2004 Over year old.

errolw98
Heliman
Location: Central Point, OR, USA

Head Speed Questions

I am trying to figure out what is the best combination for the T-Rex.
The overwhelming number of motors alone is staggering.

I have been playing with several combinations with a very cool spreadsheet program that can be downloaded free here.

http://www.rcgroups.com/forums/show...66&page=1&pp=15

It is a quite sophisticated spreadsheet program that the author continually updates. Those of you that know what you are doing will really like this spread sheet but I am lacking some information to use it with real accuracy.

What is a good target headspeed for the T-Rex 450X for sport and for 3D flying. Some of the battery, motor, pinion combos mentioned here on RR will have a head speed in excess of 3000 RPM.

Example from the spread sheet, (Hacker B20 15L at 3704 Kv, cc25, 3s1p TP-G2-2100 at 11.4V, 12T pinion = 3111 rotor head RPM at hover)
Change to an 8T pinion and the hover headspeed goes to 2074 RPM at hover but looses considerable Watts of power available at a given head speed. I am not sure if an 8T pinion for the 150T TREX main gear even exists or how much this would shorten the gear life. I realize these are just calculations and not real world observations so I am asking for a bit of help here.

Where does this helicoptor like it's head speed?
What would be wrong with running it at 2000 RPM, 3000 RPM or 4000 RPM? Does more rotor head speed = more power and better flying or just more danger and wear and tear.

I know the earlier 450 model had an overspeeding tail rotor problem that has been fixed with the 450X upgrade kit. It seems to me that the same potential for this overspeeding exists if I install a higher Kv motor with enough battery and large pinion to spin it.

Obviously I am new to both electrics and the finer points of helicopters. They are easily mastered in RFG2 where nothing ever really goes wrong.

11-10-2004 Over year old.

HOMEPAGE

Modefo's Heli's
Senior Heliman
Location: Littlerock CA

Its says 3D on the box not 30.

11-10-2004 Over year old.

Chaisit
Senior Heliman
Location: Thailand

Where do you find 12T or 8T pinion?

11-10-2004 Over year old.

motorbikemike
Senior Heliman
Location: aurora CO

I got my 8 tooth from xtreemproducts. It is the like 90 brand and it woks great.
Mike

11-10-2004 Over year old.

t3k
Senior Heliman
Location: NJ, USA

errolw98,
Crunch the spreasheet with the B20-18L and see what the HS will be. Its a 3000KV Motor with loads of tourque.

11-10-2004 Over year old.

errolw98
Heliman
Location: Central Point, OR, USA

T-Rex Head Speed

t3k,
Quote
"errolw98,
Crunch the spreasheet with the B20-18L and see what the HS will be. Its a 3000KV Motor with loads of tourque"

Ok, Using the B20-18L @ its listed 3086 Kv, with all the same equipment listed above I get the following @ 50 W/lb Hover power, 100 W/lb Average power and 125 W/lb Peak power for a 587g AUW TREX. Is this an achievable AUW?

8T = 1697 RPM, w/50 w/lb available @ 1697
9T = 1909 RPM, w/50 W/lb available @ 1909
10T= 2121 RPM, w/50 W/lb available @ 2121
11T = 2333 RPM, w/50 w/lb available @ 2323
12T = 2545 RPM, w/50 W/lb available @ 2545
13T = 2758 RPM, w/50 W/lb available @ 2758

This motor looks quite strong but leaves me with more questions as does the Align motor at 2800 Kv and a 13T pinion.

These are the numbers from the spreadsheet for a B20-18L w/13T @ 2758 RPM minimum headspeed. The RPM drops are the only thing that change with a pinion change. The rest remain constant from 8T to 13T in the spreadsheet when the minimum headspeed is changed to the 50 W/lb or hover RPM.

Power Level 50W/lb 100W/lb 125W/lb Unit
(65W) (129W) (162W)
Rotor Speed 2758 2495 2333 RPM
RPM Drop from Hover NA 263 424 RPM
NA 9.5 15.4 %
Motor Speed 31817 28785 26922 RPM
Battery Current 6.9 14.7 19.5 A
3.3 7.0 9.3 C
Efficiency 84.3 78.8 74.2 %
Motor Loss 4.1 11.5 18.8 W/oz
Battery Loss 0.2 1.1 2.0 W/oz
Flight Time 18.3 8.6 6.5 minutes

Power System Weight 204 g
Power System Cost $282

I hope these come over on the post correctly it looks like the columns will be lost so consider there are three basic power columns at 50 W/lb, 100 W/lb and 125 W/lb respectively

The two constants that change these numbers for a given power system are AUW and Minimum (or target) headspeed. If a minimum headspeed of 2000 RPM is left constant, the available W/lb change dramatically (get stronger) as you increase pinion tooth count. So, do you use your throttle curve to have hover at the minimum headspeed and increase it from there in positive and negative pitch to 100% which appears to overspeed the head?

In order to use this spreadsheet properly you need to know what the target headspeed should be. That is what I am struggling with at this time.
Should it be 1700, 2000, 2500 RPM? I just don't know. What are you getting in real life with your respective setups?

Thanks,

errolw98

Life is short, Fly hard and enjoy.

11-10-2004 Over year old.

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e-Align T-REX 450-500-600 > What head speed does the T-REX like

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