HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jan 14, 2005, 11:52 AM
Registered User
WreckRman2's Avatar
United States, FL, Apopka
Joined Mar 2002
1,674 Posts
How many teeth on the main gear for the Trex 450?

How many teeth on the main gear for the Trex 450?

What head speed are most of you guys running?


I'm just trying to figure out what kv motor would be best and with what pinion just doing some basic math.
WreckRman2 is offline Find More Posts by WreckRman2
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 14, 2005, 12:07 PM
Registered User
GGoodrum's Avatar
South Orange County, CA
Joined Mar 2003
7,994 Posts
150T.

With a Neumotor 1105/3Y (3500 kv) and a TP1320, we get a headspeed aroud 2700 with a 9T pinion.

-- Gary
GGoodrum is offline Find More Posts by GGoodrum
Reply With Quote
Old Jan 14, 2005, 12:23 PM
Registered User
WreckRman2's Avatar
United States, FL, Apopka
Joined Mar 2002
1,674 Posts
What is the desired head speed for sport flying? I ran 2400 on my Shogun.
WreckRman2 is offline Find More Posts by WreckRman2
Reply With Quote
Old Jan 14, 2005, 12:29 PM
Registered User
WreckRman2's Avatar
United States, FL, Apopka
Joined Mar 2002
1,674 Posts
Razor 2500 at 3850kv

150 tooth main and a 10 tooth pinion
15 to 1

3850kv x 11.1v = 42735rpms / 15 = 2849 head speed

150 tooth main and a 9 tooth pinion
16.6 to 1

3850kv x 11.1v = 42735rpms / 16.6 = 2574 head speed

150 tooth main and a 8 tooth pinion
18.75 to 1

3850kv x 11.1v = 42735rpms / 18.75 = 2279 head speed
WreckRman2 is offline Find More Posts by WreckRman2
Reply With Quote
Old Jan 14, 2005, 12:36 PM
Registered User
WreckRman2's Avatar
United States, FL, Apopka
Joined Mar 2002
1,674 Posts
Now I see why people are using a 12-14 tooth pinion with those low kv motors.
WreckRman2 is offline Find More Posts by WreckRman2
Reply With Quote
Old Jan 14, 2005, 12:43 PM
Registered User
College Park, MD
Joined Sep 2002
4,714 Posts
Trying to equate the Kv of a motor with the actual head speed of the heli is wishful thinking. It's a measure of the no load speed.

And saying that a 3s lipo will put out 11.1 volts under a heavy load is also wishful thinking.

You'll most likely see a voltage of 10 volts under load and the Kv is probably at least 10-30% less under load.

The numbers you list are interesting to look at but are certainly not realistic. I'm using a Himax 2025-4200 with 8 tooth pinion and 3s Lipos in my T-Rex and the calculated head speed is 2466 RPM. The max I've measured is only 2000 RPM. And the motor runs pretty hot even with the 8 tooth pinion. It's 160 degrees after just a few minutes of indoor hovering.

Here's a head speed estimator:
http://www.e-helis.com/helicalc.php
thunder1 is online now Find More Posts by thunder1
Reply With Quote
Old Jan 14, 2005, 01:12 PM
Registered User
San Carlos, California, United States
Joined May 2002
7,640 Posts
Quote:
Originally Posted by GGoodrum
150T.

With a Neumotor 1105/3Y (3500 kv) and a TP1320, we get a headspeed aroud 2700 with a 9T pinion.

-- Gary
Is this on 3s or 4s Lipo?

Toshi
TMorita is offline Find More Posts by TMorita
Reply With Quote
Old Jan 14, 2005, 01:27 PM
Registered User
United States, FL, Dunedin
Joined Nov 2003
138 Posts
Batteries

When BATTERIES think TANIC or APOGEE they're like running 30% TP'S are like 10% the rest are like FIA fuel if you can relate to glow power i can't say that about polyqest i haven't tried then
Dunedinflyer is offline Find More Posts by Dunedinflyer
Last edited by Dunedinflyer; Jan 14, 2005 at 01:30 PM.
Reply With Quote
Old Jan 14, 2005, 02:01 PM
Registered User
College Park, MD
Joined Sep 2002
4,714 Posts
Dunedinflyer, I agree. The main difference seems to be the capacity rating. I've never gotten close to the rated capacity at even low current drains on the TP and Kokam packs I've used. But the Tanics and Apogees, they deliver like the US postal service, rain, sleet or snow;-)

TMorita, If a 3s TP1320 can deliver enough juice to a T-Rex to get the head spinning 2700 RPM I'd be really surprised.
thunder1 is online now Find More Posts by thunder1
Reply With Quote
Old Jan 14, 2005, 02:09 PM
Registered User
United States, FL, Dunedin
Joined Nov 2003
138 Posts
even at o pitch mayme at 10degrees negative full power from 500 ft
Dunedinflyer is offline Find More Posts by Dunedinflyer
Reply With Quote
Old Jan 14, 2005, 02:29 PM
Registered User
College Park, MD
Joined Sep 2002
4,714 Posts
Quote:
Originally Posted by Dunedinflyer
even at o pitch mayme at 10degrees negative full power from 500 ft
Ha! Maybe through a wormhole!
thunder1 is online now Find More Posts by thunder1
Reply With Quote
Old Jan 14, 2005, 04:13 PM
Registered User
WreckRman2's Avatar
United States, FL, Apopka
Joined Mar 2002
1,674 Posts
Quote:
Originally Posted by thunder1
Trying to equate the Kv of a motor with the actual head speed of the heli is wishful thinking. It's a measure of the no load speed.

And saying that a 3s lipo will put out 11.1 volts under a heavy load is also wishful thinking.

You'll most likely see a voltage of 10 volts under load and the Kv is probably at least 10-30% less under load.

The numbers you list are interesting to look at but are certainly not realistic. I'm using a Himax 2025-4200 with 8 tooth pinion and 3s Lipos in my T-Rex and the calculated head speed is 2466 RPM. The max I've measured is only 2000 RPM. And the motor runs pretty hot even with the 8 tooth pinion. It's 160 degrees after just a few minutes of indoor hovering.

Here's a head speed estimator:
http://www.e-helis.com/helicalc.php

Say what ya want but that equation was dead on perfect with my Shogun... granted I use Apogee packs that can keep up and deliver whatever the motor asks too. Sure the crappy Kokam packs may not keep up but the Apogee's have no problems.

Also note that thos number are true for running with zero pitch or no load on the blades. I ran my Shogun with a Himaxx 2025-3200 and a 10t pinion. At 100% throttle it would turn 2800 on the head speed. I ran it in high governor mode with the throttle backed down so that it maintained a constant 2400 on the head speed. It was the sweetest running spot I found for the Shogun and I tested many, many setups. This is why I'm having a hard time deciding on another Shogun or the Trex 450.
WreckRman2 is offline Find More Posts by WreckRman2
Reply With Quote
Old Jan 14, 2005, 04:19 PM
Registered User
WreckRman2's Avatar
United States, FL, Apopka
Joined Mar 2002
1,674 Posts
Quote:
Originally Posted by Dunedinflyer
When BATTERIES think TANIC or APOGEE they're like running 30% TP'S are like 10% the rest are like FIA fuel if you can relate to glow power i can't say that about polyqest i haven't tried then

Amen to that... if you ask me Apogee is by far the best pack on the market.

As for the TP 1320's... do this. Discharge the pack at a 1amp discharge and tell me how many mah's it takes out. Thunder Power packs are still 8C packs... but they are able to claim 10C because the 1320's are actually 1550-1600 packs. 1600 at 8C is about 13amps.... or 1320 at 10C. It's just a numbers game.
WreckRman2 is offline Find More Posts by WreckRman2
Reply With Quote
Old Jan 14, 2005, 05:18 PM
Registered User
Joined Dec 2002
663 Posts
Quote:
Originally Posted by GGoodrum
150T.

With a Neumotor 1105/3Y (3500 kv) and a TP1320, we get a headspeed aroud 2700 with a 9T pinion.

-- Gary
What blades are you using?
I believe the stock wood blades rated at only 2400 rpm!!
tanasit is offline Find More Posts by tanasit
Reply With Quote
Old Jan 14, 2005, 08:58 PM
Registered User
WreckRman2's Avatar
United States, FL, Apopka
Joined Mar 2002
1,674 Posts
What head speed are most of you guys running on the Trex?
WreckRman2 is offline Find More Posts by WreckRman2
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion What kind of gear for Trex 450? larsen2000 Mini Helis 2 Oct 30, 2006 02:59 PM
Discussion hummingbird 3Dpro, how many teeth on main gear? aftica Micro Helis 2 Mar 11, 2006 09:25 PM
How many teeth on shogun belt drive pulleys? msg73 Mini Helis 1 Nov 03, 2004 11:16 PM
How many teeth on the main gear of a hornet? UAVProducts Micro Helis 1 Sep 27, 2004 11:12 AM
How many teeth on the main gear of a zoom? UAVProducts Mini Helis 2 Mar 10, 2004 04:33 PM