sgbfly

Just some more food for thought-

Intesting pinion calculator here. Anyone got an idea on the rotor rpm for the Big Lama?

Also, interesting discussion on brushless motors cogging here

Simon

Edit: Using:

1600rpm (from lama v3 at hover)
124T main gear (guess counted 1/4)
3000kV
11.1V
80% efficiency from motor specs

we get ..........7T

omg.

sgbfly

^ Makes me think about getting some 9T pinions

?

Simon

Buz

Well, that's one of the things I don't understand either. I've been flying this type of motor in all of my helicopters. I have yet to experience a motor burnout. Yes, they get so hot you can't touch them if you just hover.... but I'm flying outside at about 45mph and the motors are much cooler. My luck may be that flying FF outdoors all the time allows more air into the cabin. Now watch. I'll go right out and burn up a motor because I said that. LOL.

I have a new trick for you guys to try. (only works outdoors)... I fly fast across my property, then suddenly pull rear cyclic, which makes the helicopter stand on it's tail. Do this at a good altitude... When it stands on it's tail, quickly give it left or right aileron and it will spin around on it's tail and head the other way. I need to get my wife to video a flight so you can see it. The rotor shaft extension is the best thing that ever happened to this BOL.
I guess I should thank Jestine for that idea.

Buzz

sgbfly

Hi Buzz,

I've got to see that! Dont delay with the vid.

Simon

Buz

Oh, this is just perfect..... it's pouring rain! I'll put a video up if/when it stops.

Buzz

erdnuckel2

Hi Simon,

just as a side note: if your 124 t main gear is the BOL one, then you are off by 4t .... I DID count the whole gear once (a few times even) while contributing to another brushless thread ....

... now if you end up at 7 teeth for the pinion (and this might pose some problem) what would be the alternative ? Running the BOL on 7.4V batteries (thats what a few guys on the german forum suggested .. of course, that would - AGAIN - spell trouble:

this would (at least I can't think of a different solution of this problem) mean, to get a mixer and a gyro to match your ESC's and ditch the 4in1 (ah 3in1) completely.Any thoughts ??

Sven

EDIT :
one of the definitely biggest advantages of this approach would be the use of larger - but lighter batteries ....

shenlonco

My Feedback: (2)

Guess it's not worth spending the extra $100.00 on the brushless version it seems to have lots of problems after reading these last few posts.........?

Buz

IMHO, the best thing for you to do is to buy a stock BOL... and the rotor extension and metal head kit. It will fly just as well, if not better than a brushless set up. There are flyers and tinker-er's with these things. I'd much rather fly than tinker.

sgbfly

Hi Sven,

Thanks for your thoughts. Can you link to the german forum please? I think if we can get the right pinion thing will be a lot better. My calculation above makes some fairly loose assumptions and I would take it all with a pinch of salt. Head speed is my worst assumption. But it does show that 11T could be wrong and less teeth is more likley better (As Peter confirms). I will probaly get Esky 9T and 10T and do comparisons.

Thanks for putting me right on the BOL main gear - I was trying to count from a picture at the time!

Simon

sgbfly

Probably not just yet. My suspicion is the brushless kit on the market at present is not properly thought out / tested. Early adopters often get a raw deal (premium prices & have to sort out the bugs).

Simon

Ps. But I do think we are close to solving it with a little input from those who are technically minded.

sgbfly

Hi Buz,

Hard to argue with that especially in comaprison to my non flyer lol. My stock motors were not great and I had 2 fail. However, when I tried to convert to brushless I reckon I had 2 sound brushed motors. I do think a sorted brushless setup will be superior - but the economics are somewhat dubious.

I enjoy tinkering - it helps me understand, BUT, I like flying better and at the moment I am sulking

Simon

erdnuckel2

Hi Simon,

as you explicitly asked for it, link to german fo rum is http://www.rclineforum.de/forum/thre...er=&page=1

Do you speak German?

The actual discussion about motors, pinions and head speed is once startin at page 5 and then later again in the mid 20's I think.

Hope that helps ...

Sven

pgroom_68

Hey again Simon,

I have just completed an 11 minute flight using the 900mAh GEPower lipo with my 10-Tooth BL motors (and yes, I even put on Esky blades just for this flight)
...but IMO getting longer flight times & more power is NOT THE POINT of running BL motors! It is great to just be able to change out any 3-cell lipo that fits in the battery area - and know that even IF it is only an Esky 850mAh (only gives me 8½ minutes of mild flight), I can watch the lipo alarm LEDs and know when to land to change this out with another Lipo.
WITHOUT any heat issues I don't have to wait for the motors (and electronics) to cool before flying away again

Peter[sm=shades_smile.gif]
P.S. I now have a bulletproof BOL again. But it took a lot of hard yakka and extra purchases ($). My advice is to avoid the Ultimate - and upgrade little by little the extended inner shaft and [link=http://www.rc711.com/shop/product_info.php?cPath=60_139&products_id=1945]better blades[/link], then BL upgrade (maybe they will be OK by then)....

sgbfly

Hi Sven,

Thanks for the link. I can just about follow written German. If I get stuck I might have to PM you

Hi Peter,

Thanks for the trouble you went to. That is a useful bench mark to me if I am worried my set up is not very efficient. I agree with the rest of your post.

I like the extreme upper bearing case - much less vibrations.

Also, during a brief hover before it all went wrong I thought the slightly heavier BL BOL was more stable in the breeze. Do you agree?

Thanks to you all!

Simon

pgroom_68

Hey again Simon,

Sorry, I didn't notice that the BL setup was any more weight than the brushed! I am used to changing the weights of my set-ups by placing a heavier lipo into the purpose-built lipo "braces" - and don't have a feeling of the "norm" anymore I do agree in principle though - that a little more weight down low will create a more stable BOL.......

I also have an Xtreme metal bearing housing - but haven't put it on anything yet 'cause I have been concentrating on my HBFPv2.

Peter[sm=shades_smile.gif]
P.S. I'm going now to my local indoor helimeet - see ya!
P.P.S. Thanks again Ber60 for your pic and mod!

sgbfly

Hi Sven,

Your thoughts please. Using this as a reference post near bottom @ <font size="" face="Arial,Tahoma,Helvetica" class="smallfont"><font size="" face="Arial,Tahoma,Helvetica" class="smallfont">12.07.2009 <font color="#ff0000">15:17</font></font></font>. tells me someone has measured the hovering head speed at 2000rpm.

OK, so using the calculator with 2000rpm, 128Tooth main gear, 3000kV, 11.1V, 80% efficiency = 9T

(<span style="font-size: 10pt; font-family: Verdana; color: rgb(34, 113, 160);">2000*128/3000/11.1/.8</span>) = 9.6 so 9T or 10T

Do you think this is sensible?

Simon

Beachcomber

I've only used 10 tooth pinions on my brushless motors, so don't have any comparison, but still had to turn my gain way down to eliminate tail wag. The pinions that came with my "AEO Tech" brushless kit from E-Bay were not usable because they fit onto the shaft too loosely; I had to buy separate E-Sky press-on pinions from another source.

http://www.slickzero.com/page/SRHP/P...ccess/EK1-0352
I see that web site also has 9 tooth - EK1-0351.

It's nice to not have to worry about motors getting too hot, and being able to fly multiple batteries without waiting for cool-down. Sorry, I haven't paid much attention to flight time on stock battery. I have 3, so I just land, replace battery and fly some more.

sgbfly

^ Thanks Beachcomber!

shenlonco

My Feedback: (2)

Just wondering what pinions came with the stock brushed motors?
They say they run hot would it be possible to drop a few teeth on the pinion gear and use the stock motors so everything runs cooler?

sgbfly

stock brushed motors are 11T. Maybe this is where the brushless kit has gone wrong because they have seen stock = 11T and presumed the same for brushless!

To answer your question: I dont know - you would hope Esky had already optimised that one................

I guess at hover you would want the motor operating near peak efficiency. We need more data on the stock rk-370sd-4045 motor to try and calculate an answer. Not got time to go to google now. We need to know the motor peak efficience rpm and the hover rotor head speed. Knowing the kV would be interesting.

Simon

shenlonco

My Feedback: (2)

sgbfly

OK, I have searched with google and the kV rating of the stock brushed motor is reckoned to be ~2388 - See ref 1 &amp; ref 2 and assume efficiency 80% again although it maybe less

=&gt; 12T using this (read below it seems Esky might already have gone for a safe bet - so yes you maybe right but you will lose performance)

Going back to brushless...........

An interesting read is here. In summary it says use a lower number of teeth for improved battery life (less current draw) or higher for greater head speed.

So going back to the brushless set up post .............and assuming all assumptions are reasonable

<span style="font-size: larger;"><span style="font-family: Arial;">(<span>2000*128/3000/11.1/.8</span>) = </span><span style="font-family: Arial;">9.6</span></span>

So 9T for improved battery life and reduced currentand less heat in esc etc OR 10T for a more aggressive throttle responce and head speed.

Please feal free to pick holes in my thinking - I wont learn otherwise. I hope this gives us enough info to make an informed decision when converting to brushless and choosing pinions.

Simon

Beachcomber

Shenlonco,
You bring up an interesting point. Maybe replacing the stock pinion on the stock brushed motor with the next fewer teeth available should definitely cause the motors to run cooler ... or less hot. Not sure what that would do to your head speed; worst case you would have trouble getting enough lift to take off.

Note the shaft on the stock brushed motor is 2 mm, I think.

Shaft diameter of my brushless motors from e-Bay is 2.3 mm, so you can't exchange from one to the other.

pgroom_68

Hey again guys,

The stock motor indeed does have a 2mm shaft - as does the Xtreme 380 - both are brushed motors. Although you could play with pinions for your stock motors I think it would be a futile exercise due to the fact that whatever you do brushed motors generate heaps more heat than BL motors (BTW, my BL motor shafts are 2.3mm). The main trouble with the Esky stock motors was that the early models had a temp cut-out soldered to the top of each motor and they would pick an inconvenient time to stop rotating - like when you have a 10' altitude

Also Simon, I remember reading earlier that the headspeed for BOL hover was closer to 1800 rpm than 2000. Does this make a big diff?

Peter[sm=shades_smile.gif]
P.S. Esky has not released a BL set-up for the BOL - but other "aftermarket" companies have! Egs. "Ultimate" put together by Rc711.com, and "Dual BL" put together by rtf-heli.com

pgroom_68

Hey again Simon,

You are forgetting that one of the main purposes of going BL in the first place is so it makes the flight times possible with ONE lipo obsolete - you just change them out and fly away.....
(well, it is not really picking holes - but makes the thought superfluous anyway)

Peter[sm=shades_smile.gif]
P.S. I don't think 9½-teeth is possible!?! hehehe