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Old Sep 14, 2010, 10:45 PM
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Efficiencies among the Micros : When to MOD and not to MOD

Allow me to start this thread and possibly a venue of sharing the experiences gained on modding those micro helis (since we are in micro heli forum anyway). I think a lot can be discussed here specifically answering the question why do we need to modify the stock and why do we simply need to leave alone some of the stock configuration. Or when does a mod become efficient or simply become a bling ?;

1. Going Brushless or leaving the stock motor alone. When is brushless better and when is the stock motor better ? Bigger Motors or smaller and lighter motors ?

2. Hiller Only, Bell Head, or Bell Hiller ?
3. Modifying the rotor cyclics for more pitch or just the stock subtle cyclic ?
4. Lipo Battery - More weight but better C's, Less weight and Less C's ?
5. Lightweight for more punch or make it heavier for stability ?
6. Stock swash, modified swash ?
7. Stock paddles, lighter paddles, or heavier paddles ?
8. Flybarless, or the flybarred version ?
9. metal bearings, ceramic bearings, etc ?
10. light plastic polymer frames, aluminum frames ?
11. Metal Head, stock plastic polymer head ?

and so on ..


Let me first start with the brushless mod. I find modifying the walkera 4#3 range of helis to brushless particularly the main motor more efficient. However, making the tail brushless makes the heli less efficient and sluggish specially if its a direct drive fixed pitched although it extends the life of the heli when going brushless all the way. But do we sacrifice the flight characteristics of the heli just to extend the life of those motors ?

A brushless direct drive tail with a variable pitch tail blade however is a different story.


I find modifying the MSR to brushless highly inefficient due it its cog and weight sensitivity.

I find modifhing the Solo Pro to brushless highly inefficient with the same reason as the MSR as the stock motors are already efficient on its own.

What do you guys think ?
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Old Sep 14, 2010, 11:01 PM
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I prefer to modify the rotor cyclics, the batteries are cheap so I have a few of each to suit what I'm looking for (lightweight or longer flying times), I like lightweight to the fullest, longer flight times and more punch! Modified swash all the way! I prefer stock flybar weight or I add screws to the end of flybar for more stable flight in windy conditions. I like plastic parts cause of the weight savings and they are cheap, unless a carbon or cnc part provides more performance.
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Old Sep 14, 2010, 11:12 PM
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Originally Posted by slo-fly View Post
I prefer to modify the rotor cyclics, the batteries are cheap so I have a few of each to suit what I'm looking for (lightweight or longer flying times), I like lightweight to the fullest, longer flight times and more punch! Modified swash all the way! I prefer stock flybar weight or I add screws to the end of flybar for more stable flight in windy conditions. I like plastic parts cause of the weight savings and they are cheap, unless a carbon or cnc part provides more performance.

and that is another question actually. Do the micro CNC head upgrades provide a gain in performance or just another weight load for the already small motor ?
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Old Sep 15, 2010, 12:00 AM
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EQ, I think what you are doing is a great idea and much appreciated because it educates and puts newbies like me on a faster track.

However, you are giving us the correct answers but not too much reasoning. Newbies knowing the correct answer is valuable, but I think knowing the reasoning is more valuable.

Example:

"I find modifying the walkera 4#3 range of helis to brushless particularly the main motor more efficient."

I've read enough posts recently, that this seems to be a popular "opinion" among the experienced micro pilots. So you give the popular correct answer. But why is that the preferred answer?

From what I've read elsewhere (no direct knowledge myself), these may be some of the reasons(?):

Walkera Brushed micro Motors have cheap flimsy cat-whisker brushes, not rugged, and burn/melt easily. Most likely failure of micro Walkera heli with Brushed Main Motor is Brushed Motor. Average life of Walkera micro Brushed Main Motor is 15 flights? I saw a mod you posted where you showed how to replace the 4#3 Main Motor's whisker brushes with carbon brushes - another one of your good ideas! You stated that the improved carbon brushed motors were getting excellent life spans (over 50/100 flights?).

Brushless Motors don't have brushes, therefore aren't prone to brush failures. Have a history of getting 100's (?) of flights between failures?

I haven't read this, but from reading your above first post, it sounds as if the negative aspects of Brushless Motors is that they weigh more than Brushed Motors (you claim Brushless Motors make tail sluggish - why? - I'm guessing weight?).

Why better to have Brushless Main, but Brushed Tail?

Guesses:

Main Motors must provide the most "horsepower" and therefore use a lot of current, for reliability (long life) this requires "strong" brushes or something that can handle a lot of current. This comes at a price: Brushless Motors weigh more? (if so why?) When all the pros and cons are added, Brushless Main Motors provide more pro than con.

Tail Motors don't need to provide as much "horsepower" and therefore don't use much current, don't need "strong" brushes or something that can handle a lot of current. Brushed micro Tail Motors have an avergae life span of 100's(?) of flights before failure. No need to use heavier more reliable Motor, and having heavier Tail Motor is much worse than having heavier Main Motor because of the different effect a weight has depending on where it is placed along a see-saw.

These are all guesses on my part, and I may be way off base in these "conclusions" I've come up with, especially when I have no facts (All I'm doing is trying to connect the "dots").

The only thing I know is mSR Main Motor is brushed, and mine has lasted a few hundred (~500?) flights between failures; whereas, Walkera has a history of lasting ~15? flights (I bought my first Brushed Walkera 4#3A a week ago, and 3 days later (~15 flights) needed a new Main Motor!! I don't know why such a difference between mSR and Walkera except mSR = 30g, 4#3A = 45g (50% heavier), AND 4#3A sounds faster, and feels faster, more powerful than mSR, so I'm guessing it is because MUCH more current going through same size whisker/brush.

In my opinion, it appears: mSR = good whisker design for low current application
Walkera = bad whisker design choice for high current application.
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Old Sep 15, 2010, 12:03 AM
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I haven't noticed a difference in the performance of the mh cnc head on the msr. One thing I do know from drag racing is about sprung and unsprung weight. Any weight added to the rotating force is much greater than dead weight. It's so minimal I don't think it really makes a huge difference but something to think about once you add weight to any rotating force.
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Old Sep 15, 2010, 12:15 AM
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ok. for the tail going brushless specially on a direct drive. A brushless motor has a large casing where the magnets attached. That casing with the magnets tend to become a natural flywheel. If you are using that configuration on a tail with specifically varying the speed just to manage the yaw axis, it will take some time for the motor to accelerate or de-accelerate thus making the tail a little bit sluggish. Although motor is very strong, your rudder will not be crisp. Those small coreless motors stand a chance over the brushless ones when used as a direct drive tail rotor as there is minimal core weight - mostly the copper wiring thus making the tail more crisp and less of the rudder overshoot/undershoot.


Plus the fact that anything "weight-y" added on the tail dampens your elevator cyclic control. Best to keep the tail light. However, elevator tail damping can be counteracted by a "wider" diameter main rotor (which is another story).


A brushless variable pitched tail rotor (the ones whose blade pitch are controlled by a tail servo) on the other hand does not suffer from those slow acceleration / de-acceleration issues as the the speed of the motor are kept mostly constant and only the pitch varies thus resulting to a much 'crispier' tail.
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Old Sep 15, 2010, 12:18 AM
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Quote:
Originally Posted by slo-fly View Post
I haven't noticed a difference in the performance of the mh cnc head on the msr. One thing I do know from drag racing is about sprung and unsprung weight. Any weight added to the rotating force is much greater than dead weight. It's so minimal I don't think it really makes a huge difference but something to think about once you add weight to any rotating force.
Right on that one!

One of my experiments for example with LEDs added on the tip of a rotating rotor blade that even a small surface mount LED can actually create a significant difference on the rotor cyclic response than putting the same LEDs on the heli chassis/casing.
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Old Sep 15, 2010, 12:25 AM
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Thanks for the Tail Motor explanation. It was like having a light turned on in a dark room.

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Old Sep 15, 2010, 01:56 AM
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other factors to consider is the state of the electricals during hover and fast forward flight. Do you know that the heli consumes less current on FFF than on hovering ?
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Old Sep 15, 2010, 02:35 AM
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I noticed that I use less throttle on forward flights and flying in the wind.
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Old Sep 15, 2010, 03:32 AM
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Originally Posted by EQMOD View Post
other factors to consider is the state of the electricals during hover and fast forward flight. Do you know that the heli consumes less current on FFF than on hovering ?
An interesting bit of info, just like a real heli

Some helis have wheels instead of skids and some pilots do "rolling" takeoffs when at high altitude (thin air, needs more power) or with heavy cargo. The rotor disc seems to act a bit like a wing and produce more lift when moving.

Some of my personal opinions on the items in the list:

1. I agree that brushless main and stock brushed tail (or variable pitch with DD brushless or shaft drive) on 4#3 sized and bigger helis is best, not worth switching to brushless on mCX or mSR size / weight helis.

2. Depends on desired characteristics... I like full Bell-Hiller or even flybarless for the quick response time. Bell-Hiller is still stable enough for most situations, too. Beginners may prefer the slower Bell or Hiller only configuration. In my opinion it is worth converting to Bell-Hiller if you are not at beginner stage any more, but with more parts there is also more to go wrong / maintain.

4. It's a balance.. Find the lightest LiPo which still gives enough C and mAh for your style of flying and desired flight times. They don't have to be exclusive, there are some great lightweight high C LiPos available now.

5. Light weight for me Always try to make my helis light as possible, more efficiency, longer flight times. Can be just as stable if set up correctly, but more responsive.

6. Depends if the stock swash is weak or has some fault. Otherwise don't change it.

10. Carbon fibre frames Light and strong. Problem is you have to design / build your own at really small scale as there aren't many kits available.

11. Only go to metal if the plastic flexes too much (mushy feeling or slow response, etc.) or is too weak. Plastic heads are lighter and absorb more impact in crashes so it doesn't transfer to the rest of the heli and break something else.

Peace, hope this helps someone to decide which mods are worth doing. -Oobly
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Old Sep 15, 2010, 06:05 AM
Did you check the FAQ already?
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Lipo's, never go for less C. Since most stock batteries are fairly standard, at least on MSR/Solo Pro sized birds, another battery will usually have higher C at the same weight. For instance, Solo Pro stock batts are 3.8 grams but about 15C or so. Intellect 130 is 4.0 grams, so a little heavier, but because it's a true 25C battery, flight times are longer and with much more power.

I generally prefer mods that are reversible, so a swash with more throws sounds nice. Or ceramic bearings. If you don't like the results, change them back to stock and you're done.
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Old Sep 15, 2010, 10:14 AM
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Lipo's, never go for less C. Since most stock batteries are fairly standard, at least on MSR/Solo Pro sized birds, another battery will usually have higher C at the same weight. For instance, Solo Pro stock batts are 3.8 grams but about 15C or so. Intellect 130 is 4.0 grams, so a little heavier, but because it's a true 25C battery, flight times are longer and with much more power.

This is one question i've been pondering since the day i fabricated the 4 channel picooz. The setup is quite unusual as the platform is weight sensitive. A small amount of weight added creates a significant effect on flight characterstics and flight time. On the picooz setup for example, i use a lipo battery with a smaller C rating, flight time is longer. However if i use a higher C rating lipo (which is obviously heavier than the lower C rating lipo), the flight time is much shorter due to the added weight.

I wonder how much flight time gained on a Solo pro with a 15C lipo vs a 25C ? And because the 25C battery is a little heavier, flight characteristics should be affected right ?

Quote:
Originally Posted by SoloPro View Post

I generally prefer mods that are reversible, so a swash with more throws sounds nice. Or ceramic bearings. If you don't like the results, change them back to stock and you're done.
Ditto. In the case of the short-arm swash mod, i never took off the stock arms and simply added (CA'ed) a couple of shorter arms on the side so that i can choose anytime the preferred flight response -either stock or simply aggresive.
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Old Sep 15, 2010, 10:20 AM
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Originally Posted by oobly View Post

11. Only go to metal if the plastic flexes too much (mushy feeling or slow response, etc.) or is too weak. Plastic heads are lighter and absorb more impact in crashes so it doesn't transfer to the rest of the heli and break something else.
Right, forward flight helps on the lift thus less power required to maintain altitude.

One the plastic flexure side, was there ever a part (on the msr or solo pro )that 'flexes' significantly that will affect flight characteristics ?. The last time i did a metal head on the MSR for example, was not for flexure issues but as a venue for me to trim the sides of the grip to allow me to move the grip linkages balls inwards thus amplifying the swash data.
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Old Sep 15, 2010, 11:38 AM
Did you check the FAQ already?
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Quote:
Originally Posted by EQMOD View Post
This is one question i've been pondering since the day i fabricated the 4 channel picooz. The setup is quite unusual as the platform is weight sensitive. A small amount of weight added creates a significant effect on flight characterstics and flight time. On the picooz setup for example, i use a lipo battery with a smaller C rating, flight time is longer. However if i use a higher C rating lipo (which is obviously heavier than the lower C rating lipo), the flight time is much shorter due to the added weight.

I wonder how much flight time gained on a Solo pro with a 15C lipo vs a 25C ? And because the 25C battery is a little heavier, flight characteristics should be affected right ?


It's a balance. I tried Intellect 130 and 160. The 160 gave almost 8 minutes, while stock will get to 5:30 to 6:00 minutes, but you can feel the extra weight (4.7 grams against 3.8 for stock battteries)

The Intellect 130 is just 4 grams, so the weight gain is minimal. I don't get longer flight than stock, since both are about the same capacity, and you can't get more mah from a battery than it can contain, obviously. But with the 25C Intellect you have way more climb power, and that makes the heli actually feel lighter than with stock. So if the added weight of a high C lipo is minimal, the positive effect upon "horsepower" it has, more than compensates for the little extra weight.

Best would be a lighter lipo with higher C, naturally. And for a moment it seemed like Thunderpower had this with the 125 mah batteries they now have, but it seems they don't reach the same power level as the Intellect and Hyperion. So even though they weigh less than stock, they perform less than the heavier 130s.

Now if someone would be able to match the Hyperions in punch and at a lower weight than stock, that would be awesome. That way you will get longer flights, because the heli is lighter, and have an even better power to weight ratio because of the true 25C performance.
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