HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Nov 02, 2010, 07:07 AM
Registered User
Utah
Joined Sep 2009
499 Posts
Build Log
Smartmodel AH-6 Littlebird build.

Hi guys!

I'm building an AH-6 scale heli with a 5-blade head running 450 scale blades from smartmodel.

On my trial run-up, at 80% throttle and just enough pitch to make the skids light my tach was reading 1680 rpm. This seems a little slow as the things seem to be screaming along.

I use a Bantam Checkmaster II helo tach. Are the multiple blades throwing off the reading? Or am I reading a low harmonic and it's really 3360 rpm, maybe?

I'm using a blade400; stock 420 motor and main gear, a 9T pinion, 3s1p batt. I have a 2-blade tail rotor flipped to the left side of the tail boom.

Thanks ahead of time for any feedback here!

Will
Stenz28 is offline Find More Posts by Stenz28
Last edited by Stenz28; Nov 03, 2010 at 11:23 PM. Reason: Changed title and description
Reply With Quote
Sign up now
to remove ads between posts
Old Nov 02, 2010, 07:21 AM
Registered User
Singapore
Joined Jan 2004
1,830 Posts
I not sure about "Bantam Checkmaster II helo tach".. is it a optical type?

If it is optical, then u need to configure 5 blades in order to read properly.

If there is no 5 blades configuration, then u can configure lets say 4 blades instead. Then from your reading, u divided by 4 and then multiply by 5.

I flying my OH-6 with 5 blades as well. I using the Aurora Telemetry station with magnetic RPM readback. I set 1950RPM for it but I find that it is too high for my liking. I need to reduce the RPM and try it again this weekend.

SH
Super_Hornet is offline Find More Posts by Super_Hornet
Reply With Quote
Old Nov 03, 2010, 11:42 AM
Hooked on Heli's!
Chomper_Boom's Avatar
USA, NJ, Voorhees
Joined Aug 2005
303 Posts
I use the Bantam heli tach also and since it's a true optical tach with a rotating shutter, there should be nothing that you need to do to adjust for blade count. That being said, I have noticed differences of around 200 rpm or so between the Bantam and my CC Ice ESCs and EagleTree data recorders - can't say for sure which is right and which is wrong.

As a double check you can use the following to estimate the theoretical (mathematical) HS for your setup: http://dhrc.rchomepage.com/calc.htm. If I got all the details right for your setup, it's coming up with around 2440 RPM.
Chomper_Boom is offline Find More Posts by Chomper_Boom
Reply With Quote
Old Nov 03, 2010, 11:54 AM
Registered User
Lake Zurich, IL
Joined Jan 2008
5,654 Posts
Quote:
Originally Posted by Chomper_Boom View Post

As a double check you can use the following to estimate the theoretical (mathematical) HS for your setup: http://dhrc.rchomepage.com/calc.htm. If I got all the details right for your setup, it's coming up with around 2440 RPM.
140T main, 9T pinion, 3800kv
2440 rpm is assuming 80% motor eff at 100% throttle without any drag at 0 pitch, no tail belt drive loss. There is a lot of drag from the 5-blade head.

Since he said throttle was 80% : 2440*80% = 1952 rpm without any loss from blade drag and tail drive loss.
sidneyw is offline Find More Posts by sidneyw
Site Sponsor
Reply With Quote
Old Nov 03, 2010, 11:20 PM
Registered User
Utah
Joined Sep 2009
499 Posts
Hey thanks guys! I had it out for a quick test fly... I'll post the vid when I get home from work... it's not pretty!

It was a little wobbly, probably due to low headspeed and maybe too much servo travel?

Anyway after a few seconds I set down tail first and stripped the front plastic tail-drive gear! grrr!

On a different note, I almost have the Sport-Scale fuselage painted! hehe!

Thanks,

Will

P.S. Guess this thread should be changed to a build thread, huh?
Stenz28 is offline Find More Posts by Stenz28
Reply With Quote
Old Nov 05, 2010, 12:46 PM
3D and Scale RC Heli Pilot
BlackTitanium's Avatar
Monroe, WA
Joined Jan 2007
836 Posts
And why is it, that you're using a stock motor on a multi blade scale model?

Standing by to hear your smoked motor or ESC report.
BlackTitanium is offline Find More Posts by BlackTitanium
Reply With Quote
Old Nov 05, 2010, 04:43 PM
Registered User
Utah
Joined Sep 2009
499 Posts
Quote:
Originally Posted by BlackTitanium View Post
And why is it, that you're using a stock motor on a multi blade scale model?

Standing by to hear your smoked motor or ESC report.
Hmmm, because I'm a n00b and don't know that the stock motor won't work in a scale model. The only other size I have is an align 430xl. Then I have 550 sized 850kv motors.

And I am currently running a 35a and thinking about putting in a 40.

Will
Stenz28 is offline Find More Posts by Stenz28
Last edited by Stenz28; Nov 05, 2010 at 04:54 PM.
Reply With Quote
Old Nov 05, 2010, 04:53 PM
Registered User
Utah
Joined Sep 2009
499 Posts
First Pictures, Head

Here's a couple of pictures of the head setup:
Stenz28 is offline Find More Posts by Stenz28
Reply With Quote
Old Nov 05, 2010, 05:02 PM
Registered User
Utah
Joined Sep 2009
499 Posts
Original Fuselage markings/colors

Here's pictures of the fuselage as it comes from Smartmodel:
Stenz28 is offline Find More Posts by Stenz28
Last edited by Stenz28; Nov 05, 2010 at 05:10 PM. Reason: Added front glass pic
Reply With Quote
Old Nov 05, 2010, 05:09 PM
Registered User
Utah
Joined Sep 2009
499 Posts
Painted and Rivets

This is actually my second attempt at rivets. I was still lazy and freehanded most of them so some are ok and some are very crooked!
Stenz28 is offline Find More Posts by Stenz28
Reply With Quote
Old Nov 05, 2010, 05:30 PM
Registered User
Utah
Joined Sep 2009
499 Posts
About the paint and it looking too shiny.

I used ultra-flat paint and it looked pretty good, very flat looking.

Then I used a flat clearcoat, which as you can see isn't very flat.
Stenz28 is offline Find More Posts by Stenz28
Reply With Quote
Old Nov 05, 2010, 05:55 PM
Redjestird Youser
SidewaysLS4's Avatar
Joined Jan 2009
3,878 Posts
Interesting, looks like the mold was adjusted. Rear skid strut hole moved back to a more-scale location. Front strut holes still too close to each other though. I'm thinking, since you have to put the wood in and are painting it...take a look at my mod thread for some ideas while you are setting that up...

http://www.rcgroups.com/forums/showthread.php?t=1273070

Nice work!
SidewaysLS4 is offline Find More Posts by SidewaysLS4
Reply With Quote
Old Nov 05, 2010, 07:12 PM
Registered User
Canada
Joined Jul 2009
6,669 Posts
Quote:
Originally Posted by Stenz28 View Post
Here's a couple of pictures of the head setup:
Some questions from a noobier noob .......................
How did you get the main rotor rotation reversed and why?
If I'm not mistaken, on my Blade 400, when I raise the left stick to increase pitch, the swash lowers. In your pictures, the way you've got the links hooked up, if you raise the stick to increase pitch, the swash lowers, wouldn't the pitch on your set-up go negative? What am I missing here?
I haven't even touched my 5-blade head yet because I'm not sure how to go about it.
xviper is offline Find More Posts by xviper
Reply With Quote
Old Nov 05, 2010, 07:57 PM
SUCK LESS
FR4-Pilot's Avatar
United States, IL, Lombard
Joined May 2009
3,511 Posts
Wow - nice job Stenz! I really like the detail you're adding with the rivets How are you creating them ?

I don't know if you are using the stock E-Flite ESC but it actually reaches max RPMs at 80% throttle instead of 100%. The last 20% of stick movement is pretty much useless if your throttle curve goes above 80. You're tach'd RPMS and calculated RPMS may not match if you assume 100% is really 100% ... I try to explain it a little better here: http://www.rcgroups.com/forums/showp...3&postcount=27

-John
FR4-Pilot is offline Find More Posts by FR4-Pilot
Last edited by FR4-Pilot; Nov 05, 2010 at 08:25 PM.
Reply With Quote
Old Nov 05, 2010, 08:36 PM
3D and Scale RC Heli Pilot
BlackTitanium's Avatar
Monroe, WA
Joined Jan 2007
836 Posts
Quote:
Originally Posted by xviper View Post
Some questions from a noobier noob .......................
How did you get the main rotor rotation reversed and why?
His blades are not reversed. The are rotating Clockwise.
The full scale heli would have counter clockwise rotation.


If I'm not mistaken, on my Blade 400, when I raise the left stick to increase pitch, the swash lowers. In your pictures, the way you've got the links hooked up, if you raise the stick to increase pitch, the swash lowers, wouldn't the pitch on your set-up go negative? What am I missing here?
1. The Blade grips are connected directly to the swash
2. The ball links are on the leading edge of the rotors.
3. Swash moves up = leading edge of rotor move up

On your flybared rotor head, you have mixing arms. The mixing arms reverse the direction of travel from swash to blade grips.


I haven't even touched my 5-blade head yet because I'm not sure how to go about it.
BlackTitanium is offline Find More Posts by BlackTitanium
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Headspeed steve107 Scale Helicopters 24 Oct 26, 2010 03:21 AM
Discussion headspeed question Jasonscott Mini Helis 7 Mar 13, 2006 02:35 PM
Discussion Headspeed Question Safety Hawk Mini Helis 13 Feb 28, 2006 04:31 PM
A question of headspeed and control. HankF Electric Heli Talk 10 Aug 16, 2004 02:43 PM
Hornet 2 Headspeed question HARRomeo Micro Helis 6 Feb 01, 2004 11:31 PM