Fun, Learning, Friendship and Mutual Respect
START  HERE


Unregistered
Go Back   HeliFreak > R/C Helicopter Support > Compass Model Helicopters > Atom 500


Atom 500 Compass Atom 500 Model Helicopter Discussion


Reply
 
Thread Tools Display Modes
Old 06-13-2011, 12:55 AM   #1
npomeroy
Registered Users
 
Posts: 1,925
 
My HF Map location
Join Date: Aug 2009
Location: Hawkes Bay, New Zealand
Default Atom 500 crash diagnosis

My Atom was in slow FF about 5 metres up and just dropped to the ground. I thought it rolled as it went down.

I posted details on the Skookum forum...
http://www.helifreak.com/showthread.php?t=313419
and it seemed the crash was unrelated to the SK720 controller, BEC voltage or uncommanded Tx inputs. It was possibly a servo or the servo cable. All the servos work, but 2 of them had the arms slip 90 deg on the shaft (presumably on impact but there is a question of whether one slipped in flight - I could force them around by hand against the servo torque under test).

Another possiblity occured to me hence this post:
After the crash the main shaft had about 1 cm vertical movement, i.e. the collar had been forced downwards on the main shaft by an upwards tug on the shaft. It is hard (but not impossible) to see how this could happen when the head impacted in the ground (you would think the shaft would be forced into the heli, not pulled out of it). It's possible the dying blade thrashes created "lift" against the dirt.
BUT what if the collar slipped by itself during flight? The shaft would rise; the blades would be pulled into zero or negative lift, and down she would go.

I've crashed dumb-thumbing before but an out-of-blue dump depresses me. If I can't find the cause it can happen again. Goodbye thoughts of a scale fuselage!

Any thoughts or similar experiences?

Nelson NZ
npomeroy is offline        Reply With Quote
Old 06-13-2011, 04:04 AM   #2
chopstick
Registered Users
 
Posts: 787
 

Join Date: Jul 2008
Location: the Netherlands
Default

when the bolt in the maingear is broken, there will be enough play to get 1cm as you described.
If not broken, there is not enough room between maingear/mainpulley and the frame.

You mentined a roll. I cannot figure out how an axial displacement will cause a roll.
When the main axis goed up a little bit you should notice this since the heli will probably have less pitch (FBL). With about 5 m of height, it will last only seconds before you hit the deck.
__________________
LOGO 400SE : Stretchd to LOGO 10 size :
Spartan Vortex Nano; Scorpion 3226 1230kV
SJM180 : Skookum SK540
Rigidheli.com: The place where Dutch Helipilots meet
chopstick is online now        Reply With Quote
Old 06-13-2011, 04:33 AM   #3
npomeroy
Registered Users
 
Posts: 1,925
Thread Starter Thread Starter
 
My HF Map location
Join Date: Aug 2009
Location: Hawkes Bay, New Zealand
Default

Quote:
Originally Posted by chopstick View Post
when the bolt in the maingear is broken, there will be enough play to get 1cm as you described.
If not broken, there is not enough room between maingear/mainpulley and the frame.

You mentined a roll. I cannot figure out how an axial displacement will cause a roll.
When the main axis goed up a little bit you should notice this since the heli will probably have less pitch (FBL). With about 5 m of height, it will last only seconds before you hit the deck.
Yes, I put the peices together again to check your comment, and indeed there is only about 2mm vertical play when the collar does not hold. The spindle bolt was not broken, so my memory must be bad and the vertical movement was much less than 1cm (I dismantled the parts before writing this thread).
I agree a roll is not likely to be caused by a sudden pitch loss. The SK720 playback was a bit confusing because although my memory was of the heli tipping sideways in the air as it fell, the playback looked as though it came down level (and much slower than reality) and only tipped over when it hit ground. But I am told the playback is not exact.
Thank-you for making me investigate further, because as I was playing with the main gear I felt that that the one-way bearing is gone: It feels smooth but it is now two-way! I will need to add that to my parts order.
Probably some sort of servo malfunction was the cause but it is difficult deciding what damage happened before or during the crash.

Nelson NZ
npomeroy is offline        Reply With Quote
Old 06-13-2011, 02:48 PM   #4
chopstick
Registered Users
 
Posts: 787
 

Join Date: Jul 2008
Location: the Netherlands
Default

Glad to be helpfull.
__________________
LOGO 400SE : Stretchd to LOGO 10 size :
Spartan Vortex Nano; Scorpion 3226 1230kV
SJM180 : Skookum SK540
Rigidheli.com: The place where Dutch Helipilots meet
chopstick is online now        Reply With Quote
Reply




Unregistered
Go Back   HeliFreak > R/C Helicopter Support > Compass Model Helicopters > Atom 500


Atom 500 Compass Atom 500 Model Helicopter Discussion

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 © 2004-2011 - William James - Helifreak.com