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DF Training Wheels - 5/12/2007 8:39:12 AM   
Old Man Mike


 

Posts: 267
Joined: 4/21/2007
From: Huntertown, IN, USA
Status: offline 		Well, not exactly wheels but some of you might find this little mod interesting. I've noticed that during hard landings the HD motors take a beating on the exposed bottom area where the small braided wires and capacitors are located. I've often had a motor stop working after the braided wire became mashed flat enough to restrict the spring contact. In addition, a low throttle up can tilt the DF to the point where a blade can hit the ground. Both of these problems can be solved by using four plastic film canisters which have the ends cut away and a side cut of 1/2 inch to allow it to wrap around the motor housing. A couple of wraps of Black tape keeps it snug to the motor. The picture below should explain it all. The total added weight for all four protectors is less than 3/4 ounce. I was very surprised to find that the DF actually flew more stable with these four protectors. My best hovering time in the 8' x 8' room before the mod was 1 minute. I am now able to do double that. Here is a little video of the modification in flight: DFinside

When flying outside, the protectors seem to act as a shock absorber during a hard angle landing and help to keep the rotors out of the grass during normal landings and takeoffs.

Mike


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       Post #: 1

RE: DF Training Wheels - 5/12/2007 2:53:42 PM   
kokomiko


 

Posts: 33
Joined: 9/19/2006
From: Koh Samui, THAILAND
Status: offline 		Hi Mike

I think it is not a good idea to wrap the HD motors in anything at all as they are getting very hot.
Secondly, if you crash, all the force is distributed to the one motor you hit on and will more likely break the motor mount, or even the center cross, and will also not prevent the rotors from hitting the ground.
Have a look at my solution at http://www.rcuniverse.com/forum/m_5097494/tm.htm

(in reply to Old Man Mike)
       Post #: 2

RE: DF Training Wheels - 5/12/2007 3:32:12 PM   
BB_DF



Posts: 273
Joined: 4/19/2007
From: Eagle, ID, USA
Status: offline 		Hey Mike,
Good flyin' man, in such a small area! I agree with kokomiko - the motors get hot enough already and don't need any encouragement.

When I was using the simulator I noticed it was a lot easier to fly if I sat the transmitter down on my knees, so my hands and fingers could stay relaxed. I decided to try a transmitter tray, and I really like it. A strap clipped on the front of the transmitter alone does not hold it securely enough for my liking, but the tray works perfectly. You can have the alertness of standing up with the stability of sitting down.

HERE,s where I ordered mine. I would suggest the one without the hand rests - it allows your hands to sense the edges of the transmitter, which helps maintain your stick/DF orientation, and is small and light.

Take care,
Bruce

(in reply to Old Man Mike)
       Post #: 3

RE: DF Training Wheels - 5/12/2007 8:08:36 PM   
Old Man Mike


 

Posts: 267
Joined: 4/21/2007
From: Huntertown, IN, USA
Status: offline
quote:

ORIGINAL: kokomiko

Hi Mike

I think it is not a good idea to wrap the HD motors in anything at all as they are getting very hot.
Secondly, if you crash, all the force is distributed to the one motor you hit on and will more likely break the motor mount, or even the center cross, and will also not prevent the rotors from hitting the ground.
Have a look at my solution at http://www.rcuniverse.com/forum/m_5097494/tm.htm




Kokomiko,

I'll address your second point first. When the film canisters are cut into the slitted tube form, they are quite flexible. A shock absorber works by distributing the energy of an impulse over time. That is exactly what these protectors do. During an angled crash without the protectors, the very hard motor body takes all the force impulse and trasfers it to the frame. With the protectors that force is distributed over time and is less likely to damage either the motor or the frame. I had a 45 degree crash yesterday from aprox 30 feet with absolutely no damage. While that is not absolute proof (I put my faith in engineering principles) it certainly is encouraging. Of course an large angle crash will still allow the rotors to hit. The added rotor clearance I was referring to was for normal takeoffs and landings.

As for the HD motors. First, these motors are lightly loaded without the SAVS portion installed. Mine run warm to the touch after 10 mins of flight but certainly not hot. I could detect no difference in temperature by feel with the protectors vs without them. Remember that the canisters are cut as slotted tube so there is still air flow. Since you and others questioned the heat, I will make some direct thermal coupled temperature measurement to establish the real temperature difference. My personal opinion is that you are more likely to damage the motors from a crash without the protectors than from the small increase in heat.

Mike

(in reply to kokomiko)
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RE: DF Training Wheels - 5/12/2007 9:02:54 PM   
BB_DF



Posts: 273
Joined: 4/19/2007
From: Eagle, ID, USA
Status: offline
quote:

ORIGINAL: Old Man Mike

As for the HD motors. First, these motors are lightly loaded without the SAVS portion installed. Mine run warm to the touch after 10 mins of flight but certainly not hot.


Interesting. After 10 minutes mine are too hot to touch. I actually wouldn't mind having some black anodized heat sinks on them.

(in reply to Old Man Mike)
       Post #: 5

RE: DF Training Wheels - 5/13/2007 5:55:18 AM   
Sky High



Posts: 1514
Joined: 12/3/2005
From: Atlanta, GA, USA
Status: offline 		Old Man Mike, couldn't you at least punch random holes in those cannisters with some hole punchers? I bet the plastic is thin enough for one to penetrate. DFI sells heat sinks for our motors. I used to fly with them but quit to save on weight as light as they are. I also didn't think they made enough different to matter. There is a thread discussing how someone actually performed a test with and without sinks with a heat measurer and said that the sinks did reduce heat when used.

_____________________________

Up there, you don''t have time to think, if you think, you''re dead!
Never mess with a pilot having more rotors than yo

(in reply to BB_DF)
       Post #: 6

RE: DF Training Wheels - 5/13/2007 6:00:30 AM   
BB_DF



Posts: 273
Joined: 4/19/2007
From: Eagle, ID, USA
Status: offline 		I thought the heat sinks were not available for the HD motors, though the black color will radiate heat better than silver. They do seem to cool down pretty quickly.

(in reply to Sky High)
       Post #: 7

RE: DF Training Wheels - 5/13/2007 7:02:57 AM   
Sky High



Posts: 1514
Joined: 12/3/2005
From: Atlanta, GA, USA
Status: offline 		I assume they would fit both because the HD motors fit the same motor mounts.

_____________________________

Up there, you don''t have time to think, if you think, you''re dead!
Never mess with a pilot having more rotors than yo

(in reply to BB_DF)
       Post #: 8

RE: DF Training Wheels - 5/13/2007 7:14:50 AM   
BB_DF



Posts: 273
Joined: 4/19/2007
From: Eagle, ID, USA
Status: offline
quote:

ORIGINAL: Sky High

I assume they would fit both because the HD motors fit the same motor mounts.


You would think so, but they only have one heat sink and it says this at the bottom of the page:

Note: These heatsinks will work with the standard silver motors used on the Draganflyer VTi and VTi Pro.
Will not work on SAVS heavy duty motors.

(in reply to Sky High)
       Post #: 9

RE: DF Training Wheels - 5/13/2007 10:18:49 AM   
kokomiko


 

Posts: 33
Joined: 9/19/2006
From: Koh Samui, THAILAND
Status: offline 		Old Man Mike

Hm...after a battery worth of flight (8-12 minutes) my HD motors are also to hot to touch as BB_DF mentioned (I think it depends also on the weather conditions because when you (or the Ti) have to fight against wind, or it is very hot outside, the motors have to work harder). But it will be interesting to see the results after the measurements.

BB_DF
I bought the heat thinks (the green ones) but could not use them because they are to long? and stand over by app. 3mm, therefore touching the power connections and the capacitors.
You could cut of a quarter to shorten them though, but the combined weight of them is 37grams also!

(in reply to BB_DF)
       Post #: 10

RE: DF Training Wheels - 5/13/2007 11:39:53 AM   
Old Man Mike


 

Posts: 267
Joined: 4/21/2007
From: Huntertown, IN, USA
Status: offline 		Ok guys, I spent some time today testing with a thermalcouple attached to one of the motors and a temperature monitor mounted to the battery platform (see attached). Here are the results:

No Motor Protectors after 1 min flight (average of 3):
- 11 F deg rise at end of 1 min
- 17 F deg rise (peak) aprox 1 min later after motor shutoff

With Motor Protectors after 1 min flight (average of 3):
- 14 F deg rise at end of 1 min
- 21 F deg rise (peak) aprox 1 min later after motor shutoff

After looking more closely at the the motor design, I can see that the real cooling comes from the air passing thru the motor. Heatsinking the motor case does very little to cool down the temperature of the motor windings and magnets since there is a high thermal resistance between those components and the case. The protectors do not restrict the air flow thru the motor which is why there is only a 3 to 4 degree increase of motor temperature. Notice that there the temperature rise after stopping the motors is about twice the increase from adding the protectors. If you really want to reduce the maximum temperature levels for the motors just spray some compressed air into the top of each motor after landing. I tried this and it immediately stopped the post flight temperature rise.

By the way, I was able to fly inside my 8' x 8' test area for a continuous 5 mins with the motor protectors. I could only do a little over 1 minute without the protectors due to higher instability (I need to understand if this is due to the added weight at each motor or if there is some aerodynamic effect of the tubes that increase the stability). Anyway the temperature rise peak after the 5 min flight was 44 degrees. I believe that 140 degrees is the approximate point at which motor life begins to suffer so flying in the upper 90's might become a problem. Again, you can help things a lot by just spraying compressed air in the tops of the motors after landing.

Finally, I think that a small funnel expansion at the top of the protectors might actually provide increased cooling compared to no protectors. Not sure how it could be fabricated. But for the time being, I'm sticking with this simple approach to protecting the DF during the hard landings along with gaining that additional stability.

Mike





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(in reply to kokomiko)
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RE: DF Training Wheels - 5/13/2007 3:48:08 PM   
BB_DF



Posts: 273
Joined: 4/19/2007
From: Eagle, ID, USA
Status: offline
quote:

ORIGINAL: Old Man Mike

Ok guys, I spent some time today testing with a thermalcouple attached to one of the motors and a temperature monitor mounted to the battery platform (see attached). Here are the results:

No Motor Protectors after 1 min flight (average of 3):
- 11 F deg rise at end of 1 min
- 17 F deg rise (peak) aprox 1 min later after motor shutoff

With Motor Protectors after 1 min flight (average of 3):
- 14 F deg rise at end of 1 min
- 21 F deg rise (peak) aprox 1 min later after motor shutoff

After looking more closely at the the motor design, I can see that the real cooling comes from the air passing thru the motor. Heatsinking the motor case does very little to cool down the temperature of the motor windings and magnets since there is a high thermal resistance between those components and the case.


This is a valuable observation! A can of Dust-Off might help significantly prolong motor life.


quote:

ORIGINAL: Old Man Mike

By the way, I was able to fly inside my 8' x 8' test area for a continuous 5 mins with the motor protectors. I could only do a little over 1 minute without the protectors due to higher instability (I need to understand if this is due to the added weight at each motor or if there is some aerodynamic effect of the tubes that increase the stability).


Hmm, I don't know. Flying is 95% subconscious, and it might just be the new gear is giving you a bit more assurance. Learning to fly is like learning to play a musical instrument. You have to consciously analyze the process at the beginning, but eventually you have to get your conscious mind out of the picture in order to progress further. You DO have to observe, but as Sky High says, "You don't have time to think". It's a weird thing when one day you discover you already know how to fly if you can just get out of your own way. The musician hears a musical phrase in their head, and their fingers play it. The 3-D heli pilot thinks of the whole maneuver, and not each movement of the sticks. But in both these cases they practiced endlessly until they didn't have to think about it. Yitzak Perlman would practice his violin scales while watching television - heresy!

I think your best bet is to learn to use the Ti and practice outside in calm conditions. Land and rest every couple of minutes, even if everything is going fine. I think you'll find it's much easier hovering at waist level over grass because you won't be fighting your own vortices, and if you panic, just chop the throttle and land. Do what builds your confidence, even if it's just hovering nose-out for hours, but try to get a little more control each time you fly. When you use Ti, take a small thin board, like masonite, and when you set the thermal levels (throttle down & right), do it on a level spot out in your yard, away from the driveway and house. This will reduce the amount of trimming needed. You already know how to fly, what you need now is just a little more confidence.

Cheers,
Bruce





(in reply to Old Man Mike)
       Post #: 12

RE: DF Training Wheels - 5/13/2007 7:39:49 PM   
Old Man Mike


 

Posts: 267
Joined: 4/21/2007
From: Huntertown, IN, USA
Status: offline
quote:

ORIGINAL: BB_DF

Hmm, I don't know. Flying is 95% subconscious, and it might just be the new gear is giving you a bit more assurance.



I agree that this could be happening so I'm trying to come up with some sort of test to prove it. I've tried close trimming and then letting go of the joy sticks but there is too much variablity in the time before I have to return to flying it. (But I swear it seems to be a longer period with the protectors on.) One approach I am considering is to buy a Berg receiver module and record the servo outputs with a 4 channel a/d converter from that receiver while hovering the DF inside. It should then be possible to compare the peak to peak and average corrections of hovering with and without the protectors. (I guess 30+ years of engineering design is coming back to haunt me.) If this works, I will be able to make accurate measurements of any modifications made to DF relative to stability.


quote:

ORIGINAL: BB_DF

I think your best bet is to learn to use the Ti and practice outside in calm conditions. Land and rest every couple of minutes, even if everything is going fine. I think you'll find it's much easier hovering at waist level over grass because you won't be fighting your own vortices, and if you panic, just chop the throttle and land. Do what builds your confidence, even if it's just hovering nose-out for hours, but try to get a little more control each time you fly. When you use Ti, take a small thin board, like masonite, and when you set the thermal levels (throttle down & right), do it on a level spot out in your yard, away from the driveway and house. This will reduce the amount of trimming needed. You already know how to fly, what you need now is just a little more confidence.



You've just described exactly what I have been doing as often as low winds permit. I find myself now flying in active mode rather than training but still have occasions when my fingers seem to be in an ackward position or strained while doing some of the movements.

---------

Also, thanks to Sky High for the comments on my indoor flying. I've spent a lot of time reading your excellent posts.

Mike




(in reply to BB_DF)
       Post #: 13

RE: DF Training Wheels - 5/13/2007 9:18:10 PM   
BB_DF



Posts: 273
Joined: 4/19/2007
From: Eagle, ID, USA
Status: offline