RunRyder RC
 9  Topic Subscribe
WATCH
 2 pages [ <<    <     1     ( 2 )    >    >> ] 2064 views POST REPLY
Scorpion Power Scorpion Power
Helicopter
e-
Blade
Other › Why the DD Tail Motor Burns Up
11-28-2007 02:34 PM  9 years agoPost 21
DeaninMilwaukee

rrNovice

milwaukee WI

My Posts: All  Forum  Topic

"JMO, Why would you use the stock geared
tail(pos) with a DD motor?
Bob"

"see to me that is still not good enough....if you fly a few batteries everyday then 20 hrs is less than a month of flying especially with weekend hours"

I went this route because I was getting only 5-6 hours from the stock tailmotors.
I admit mine work harder than most because my blade is heavy and also because I'm running brushless with a 2200 headspeed. Still, 5 hours was just ridiculous, and the DD motors cost the same and last 4x as long, plus have a small performance gain.

"the dual rates suggestion doesn't make any sense to me either....if you are going through all the trouble to go DD for more tail authority, then limiting your tail response with the TX...whats the point??"

Agreed, why bother changing at all. this solution was just floated as a way to make the dd motors last.

PM  EMAIL  Attn:RR  Quote
11-28-2007 02:38 PM  9 years agoPost 22
fenderstrat

rrProfessor

Aston,Pa

My Posts: All  Forum  Topic

this solution was just floated as a way to make the dd motors last.
agreed......there has to be some way to get these motors to last more than a couple of weeks

maybe your idea is it...DD type motor with gearing so the motor does not have to pull as many amps to get the same rpm

Compass helis Support Team
PerformancePlusRC field rep
Mini Titan/SE
TEAM KBDD

PM  EMAIL  GALLERY  Attn:RR  Quote
11-28-2007 02:46 PM  9 years agoPost 23
tutelar-rc

rrKey Veteran

Nobleton, Ontario - Canada

My Posts: All  Forum  Topic

BP Hobbies has a similar motor rated at 8.4V for only $4.03...

[http://www.bphobbies.com/view.asp?i...d=U227032&img=l]

I have 2 of these, but have not flown them since I went to BL at that time (bought them as spares if I have a problem with the BL - not required yet). The pictures & video to start this topic are actually the BP Hobbies motor.

At $4 or $10 per motor, a BL upgrade quickly pays for itself...

PM  EMAIL  GALLERY  Attn:RR  Quote
11-28-2007 03:01 PM  9 years agoPost 24
tutelar-rc

rrKey Veteran

Nobleton, Ontario - Canada

My Posts: All  Forum  Topic

maybe your idea is it...DD type motor with gearing so the motor does not have to pull as many amps to get the same rpm
Actually, gearing reduces the blade rpm allowing for a larger propeller.

I would think that whether you use either:
  • high blade rpm and smaller blade, or
  • low blade rpm and larger blade
the thrust per current draw (amp) will be about the same.
(Obviously totally ignoring efficiency losses, which I am not qualified to talk to...)

IMO if you are not burning up DD motors as fast, then the tail authority is not as good.

PM  EMAIL  GALLERY  Attn:RR  Quote
11-28-2007 04:49 PM  9 years agoPost 25
dignlivn

rrApprentice

Cullowhee,NC.

My Posts: All  Forum  Topic

Am I the only one running a stock
8T brushed main motor with the DD
tail ? My Head speed is at the low
end of the spectrum.

Bob

dignlivn

PM  EMAIL  GALLERY  Attn:RR  Quote
11-28-2007 06:27 PM  9 years agoPost 26
tutelar-rc

rrKey Veteran

Nobleton, Ontario - Canada

My Posts: All  Forum  Topic

I was. I made the following improvements to bump the headspeed a little and to get a little more climb-out:
- advance the timing on the main motor
- go back to flat bottomed blades
- increase to a 10tooth pinion
Note: if you are going to make these changes, make sure you use the paper clip mod so you do not burn up your 3-in-1 or 4-in-1 in a crash.

A very enjoyable flying experience, I was doing loops, rolls, and flips quite easily with this setup. This heli is now with my brother and he is learning to fly with it.

I switched to BL to avoid the concern of motors burning out.

If I had it to do over (hindsight is always 20/20?), I would:
- stay stock main, advance the timing
- add HH gyro (cheap Esky or Telebee)
- switch to DD tail, when original burns out
- switch to 2.4gHz radio if stock radio glitches out

Get good at all flying modes, including mild 3D, then make a serious decision as to which heli model/fuel type/etc I really want to fly.

PM  EMAIL  GALLERY  Attn:RR  Quote
11-29-2007 02:12 AM  9 years agoPost 27
DeaninMilwaukee

rrNovice

milwaukee WI

My Posts: All  Forum  Topic

"Actually, gearing reduces the blade rpm allowing for a larger propeller.
I would think that whether you use either:[list]
[*] high blade rpm and smaller blade, or
[*] low blade rpm and larger blade
the thrust per current draw (amp) will be about the same.
(Obviously totally ignoring efficiency losses, which I am not qualified to talk to...)"

All correct except the last. Thrust per current draw is NOT the same.

All things being equal, a bigger prop spinning slower is more efficient than a small prop spinning fast, and will use much less power to do the same job.

This is why 3d airplanes use great big slow turning props.

I ran a motocalc program using a known rpm I saw with my geared setup of abut 5200 rpm with the stock 5" prop and compared it to what it would take to see the same thrust wth the 3x2 the DD setups, both using the same DD motor on 3 cells:

3x2 DD = 2.3 amps and 5.2 oz thrust
5x4 geared = 0.9 amps and 4.9 oz thrust

The calc program is'nt perfect, but is close and lets you compare differences between setups accurately. We can surmise that geared makes about 6% less thrust, but does it at only 40% of the amps.

That explains why they hold up till the brushes finally wear out.

For grins I plugged into the system the 4.8 motor into the geared setup: 1.5 amps and 7.3 oz thrust. I have NOT tried that one in real life however so your results may vary.

Dean in Milwaukee

PM  EMAIL  Attn:RR  Quote
11-29-2007 04:41 AM  9 years agoPost 28
tutelar-rc

rrKey Veteran

Nobleton, Ontario - Canada

My Posts: All  Forum  Topic

Thanks Dean. As I said, I am not qualified to talk to the efficiency losses.

I am amazed that it makes such a big difference.

Now if we can only get a big, efficient geared tail that changes rpm quickly so it holds the tail as well as the DD tail!

As always, there are trade-offs.

BTW:
What calculated rpm did you need on the 3x2 DD tail?
What rpm and current draw would a DD 4x3 prop require?

Thanks for the info! Is there a link to the motocalc program?

PM  EMAIL  GALLERY  Attn:RR  Quote
11-29-2007 08:20 AM  9 years agoPost 29
LouInSD

rrVeteran

San Diego CA USA

My Posts: All  Forum  Topic

I agree with Tryan and Fenderstrat, its pretty much not worth the trouble...

Go BL tail or go T-Rex...

I have two T-rex 450's, a Trex 600, a pixy zap and a couple of other helis but this one collected the most dust until I went BL. Now I have problems with the HDX 300 V2 head not spinning true but other than that, Ive forgotten what it was like to have problems with the tail...I put a Logictech gyro on it and a BL tail and it flies great...about as solid as you can get without going belted tail...

I know I used to run motors that were rated for 12 volt and that solved the burning out problem but theyre hard to find and theyre mislabeled and...the problems went on and on...

Go BL tail or Go T-Rex, then you'll see what flying is all about...

PM  EMAIL  GALLERY  Attn:RR  Quote
11-29-2007 01:48 PM  9 years agoPost 30
DeaninMilwaukee

rrNovice

milwaukee WI

My Posts: All  Forum  Topic

Motocalc is a program you have to pay for, but can get for a 30 day free trial by going to motocalc.com

I use it for designing planes and they always fly well from the first flight.

The 3x2 should be ballpark 28k rpm

A 4x3 goes to: 3.7 amps and gets about 5.7 oz thrust a 17k rpm.

The motor is horribly overloaded with this prop with efficiency down around 44%.

The way find the efficent rpm range of any motor is to take its no load rpm ( kv), multiply by volts, and then use a prop that loads it to around 80% of that. If its geared, then you also divide by the gear ratio to get final output rpm.

The gws ips has a kv of 3385 rpm/volt, so 3385 x 11.1 = 37573 x .8 = 30k rpm. If the prop load is big enough to slow it to less than this, amps will go up and motor efficiency will go down. ( motor heating goes up) Go far enough and the motor fails quickly.

By contrast gearing puts motor rpm at closer to 34k, and amps drop way off because of it.

Also, with ips motors in particular, their brushes wear very fast over 2.0 amps, so thats a secondary limitation.

As an extreme example of what happens to prop efficiency as diam goes up and rpm goes down at the same power level.
Both examples using the same sp400 motor, 3s batteries and motor load, ( watts), changing only gear ratio and prop size.

ratio 2:1 prop 6x4

Batt Amps = 7.2
Input (W) = 75.2
Prop RPM = 12693
Thrust (oz) = 9.4

Now with 6.3 ratio and 12x8 prop

Batt Amps = 7.3
Input (W) = 76.0
Prop RPM = 4009
Thrust (oz) = 18.0

Notice watts are virtually identical, rpms are less than a 1/3, but thrust has almost fully doubled

Big props spinning slow just work better.

Kinda explains why main rotor sets are so big does'nt it?

Dean in Milwaukee

PM  EMAIL  Attn:RR  Quote
11-29-2007 01:55 PM  9 years agoPost 31
fenderstrat

rrProfessor

Aston,Pa

My Posts: All  Forum  Topic

Big props spinning slow just work better.
excellant explanation....also explains the stock tail set up.......it comes to this.....I think you either have to accept the Blade tail stock and enjoy it for what its worth or go BLDD....the voltage/amps/rpm/motor combo's we are trying to work with just aren't suited for what we are trying to do.....we need to be working WITH the laws of electricity not AGAINST them

one thing nobody has seemed to mention is the abuse the motor takes because of the inherent design.......for someone hovering, the motor doesn't see much voltage change...but someone doing hard flying or lots of piros.....when going from full left rudder to full right the motor goes from 0 volts to full voltage available...those little cheap brushes just cant handle too much of that....thats why some guys are having more luck......flying style has a lot to do with it

Compass helis Support Team
PerformancePlusRC field rep
Mini Titan/SE
TEAM KBDD

PM  EMAIL  GALLERY  Attn:RR  Quote
11-29-2007 05:28 PM  9 years agoPost 32
dignlivn

rrApprentice

Cullowhee,NC.

My Posts: All  Forum  Topic

[quote].......for someone hovering, the motor doesn't see much voltage change.

fender

I agree, that is what I do, a little
FF and hover. Once I get the hang of
Nose In, i'll move on to a better bird.
lol.

Bob

dignlivn

PM  EMAIL  GALLERY  Attn:RR  Quote
11-30-2007 02:31 AM  9 years agoPost 33
LouInSD

rrVeteran

San Diego CA USA

My Posts: All  Forum  Topic

Dean, you should be talking to the engineers at E-Flite. They put a big prop on a motor with the lifespan of a fruitfly.

If mounting two motors solves a problem its obvious it was engineered to fail...

PM  EMAIL  GALLERY  Attn:RR  Quote
11-30-2007 04:47 AM  9 years agoPost 34
DeaninMilwaukee

rrNovice

milwaukee WI

My Posts: All  Forum  Topic

Yup, the stock motors just not up to the job, although gearing it was the right way to go.

Its too bad you can't get it anymore, but the century high authority tailmotor ( cne253?)was basically a ips motor with the correct pinion already in place. THATS what eflite should have speced for he blade in the first place.

Dean

PM  EMAIL  Attn:RR  Quote
11-30-2007 07:18 AM  9 years agoPost 35
LouInSD

rrVeteran

San Diego CA USA

My Posts: All  Forum  Topic

Dean, I think I would agree with you if we were talking props for airplanes but on a mini/micro heli tail I think you need quick spin up and some braking so as to be able to change directions quickly. Too much mass is not a good thing when it comes to a tail prop. I dont think anyone would be capable of doing the kinds of things you see in this video with a large prop on a gearbox...

http://media.putfile.com/Hyper-BCP-Pro-10906

PM  EMAIL  GALLERY  Attn:RR  Quote
12-03-2007 03:37 AM  9 years agoPost 36
jwhitacre

rrKey Veteran

Tarentum,PA- US

My Posts: All  Forum  Topic

WOW My hat is off to that pilot. I didn't even think that the BCPP in any form was capable of some of those maneuvers.
That being said, here is the only luck I found for the tail saga.
After trying the DD thing and also a ducted fan with nothing but problems, I ended up putting a gearbox back on and using a higher voltage motor on it.

The motor in the pic is an Ikarus piccolo pro motor. It is a little pricey for a tail motor($22) but held up in the long run. Don't get me wrong, this by no means is this the great solution to the problem. It's just a suggestion that works well for sport flying.

Depleting the world of parts, one crash at a time!!

PM  EMAIL  GALLERY  Attn:RR  Quote
12-03-2007 04:52 AM  9 years agoPost 37
Helinorth

rrApprentice

Terrace Bc Canada

My Posts: All  Forum  Topic

I was looking at my heli the other day and noticed that i have been using the bec on the ics50 to run the electronics.When i originally went brushless main i was still using the 3n1 so i disconnected the bec wire on the esc.Then connected the dd with the ics50 and completely forgot to hook the main bec back up i know that 2amp esc probably shouldn't run the rec ,servos,and gyro but it has for quite sometime now without any problems.I don't do any hard 3d but lots of fff piros loops etc and after a full 10 min flight the tail mtr is just warm .I also checked the end bell and the ones we have been using are the black ones.Could this have any bearing on the improved lifespan in my application?

Ryan

PM  EMAIL  Attn:RR  Quote
WATCH
 2 pages [ <<    <     1     ( 2 )    >    >> ] 2064 views POST REPLY
Scorpion Power Scorpion Power
Helicopter
e-
Blade
Other › Why the DD Tail Motor Burns Up
 Print TOPIC  Make Suggestion 

 9  Topic Subscribe

Tuesday, October 24 - 8:54 am - Copyright © 2000-2017 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online