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e-Minicopter Joker > MJ2 Crash Avoided?
 
 
500Driver
Senior Heliman
Location: Gulf Breeze, FL

Noobs,

I'm speaking for myself...but likely a good group of others as well when I say this:

I'm glad you're staying with the MJ2! Your insights, photos, tips, tricks, etc. have been a HUGE help to a 'noob' like me.

THANK YOU!

When in doubt...auto out
07-21-2008 10:38 PM
 
 
keithm
Senior Heliman
Location: Ocala, FL

Pletti temps

Nooobs wrote:
Quote 
The Pletti ran hotter than the 32-4. Maybe it was my setup. I couldn't touch the motor after flights.

Just flew MJ2 with a 91F ambient temperature. after 10 minutes, (bare helicopter - no mount) the hottest point on the Pletti was 144F, on the 40-160 ESC 129F and on the A123 pack 105F. Sounds like yours must be much hotter.

I'm either not getting the power that you are or something is set differently on yours. After the flight, I put about 7250mah back into the 9200mah Tanic A123 pack.
07-22-2008 12:13 AM
 
 
phil007Senior Heliman - Location: Austin, Texas -
Keith,

Your temps look the same as my friend with the J2 but are you battery numbers and amp draw correct? Is it a 12s4p pack?

- 10 minute flight
- 7250mah
- 9200mah Tanic A123 pack


My MJ1 loaded up at 17lbs flying for about 8 minutes is pulling 4,162mA from a 12s2p A123 battery pack.



Phil
07-22-2008 01:24 AM
HOMEPAGE  
 
 
keithmSenior Heliman - Location: Ocala, FL -
Hi Phil:

I hope we aren't comparing apples and oranges. I have the cell in the photo. My understanding is that each of the paralleled cells is 4600mah for a total of 9200mah. If the pack takes a 7500mah recharge after a 10 minute flight, the model has "consumed" 750mah per minute. This MJ2 also weighs in at 17 lbs. If you put back 4162mah after 8 minutes, you are"consuming" 520mah per minute.

Considering my Trex 450 which is very small compared to the MJ2 puts back about 1700 after 6 minutes which is 283 per minute, I would think your MJ would not be as efficient as you describe.

Perhaps we are comparing diffeent values or I've got something wrong. Ideas??

Keith

07-22-2008 02:32 AM
 
 
rroback
Elite Veteran
Location: Irvine (UCI), Ca

a123 are 2300mah cells. 12s2p packs is 4600mah. I've got 3 of those.... I haven't fully tested my maxi on a123, but 8 minute flights seems a little long, although it would be great if I could achieve that without lipo.

Rhett... I can't fly, luckily the HC Profi Can!
07-22-2008 03:06 AM
 
 
nooobs
Key Veteran
Location: Toronto, Canada

500Driver

YOU'RE WELCOME! We're all in this together. It has been less than a year since I built and flew my first heli. Without the help of many people here I'd still be trying to figure out manuals. I'm just sharing my experiences whether it's good or bad so others may learn from my failures and successes. Yes I'm glad I stayed but you can understand the frustration after having six crashes already this year. I could have had a Profi by now... LOL ...cause that's how much I've spent on repairs...


Keith

Yes I was getting 144°F (62°C) on the Pletti. Too hot to touch. And that's just hovering around.

Flew today to compare. After a 10 minute hover the 32-4 was only 32°C (89°F), PowerJazz at 31°C (87°F) and Lipos were 39°C (102°F). Way cool!

Temperature today was 24°C (75°F).
07-22-2008 03:53 AM
HOMEPAGE  
 
 
fergus
Veteran
Location: Ireland

You have soemthing wrong there Keith. The packs are 4600mAh capacity so no way they could take 7500 back in. Count the cells in your pack. You should get 24 if its 12s2p.

My Joker2 without mount and running 710mm blades and much higher headspeed than the maxis will do over 8mins of spirited sport flying on 12s2p A123 consuming about the same as Phil sees on his 17Ib maxi.

How did you arrive at the figure of 7500 for a recharge. What charging setup have you?

Phil: Great chart. What happened after 5mins - You got bored and decided to flip it didn't you

Regards

Fergus
07-22-2008 04:23 AM
 
 
keithm
Senior Heliman
Location: Ocala, FL

Duhhh... I'm charging the pack as two parallel 6 cell packs with a harness set up by Tanic using a TP1010C charger and 210 balancer. This setup then must read twice the MAH reading so my 7500mah is divided by two or 3750mah for a 10 minute flight with mostly hovering and forward flight. This seems more reasonable based on what Phil and Fergus say..

Nooobs.. You must not have asbestos lined fingers.. 144F isn't hot!

Seriously - sounds like your setup runs way cool. Wish it was 24C (75F) here this time of the year.
07-22-2008 04:56 AM
 
 
fergus
Veteran
Location: Ireland

yep thats it Keith. You are charging as 6s4p (9200mAh) and flying as 12s2p (4600mAh) so dividing the results of the charge on the 1010C by two will give you the correct mAh reading

Regards

Fergus
07-22-2008 05:09 AM
 
 
phil007
Senior Heliman
Location: Austin, Texas

Quote 
Phil: Great chart. What happened after 5mins - You got bored and decided to flip it didn't you
Flipping a 17lb Maxi!

This was one of my stress tests to see what flight times I could get hovering with the A123 pack. I hovered with a few quick climbs until the packs dumped to see how high the amps would peak. I'd say a 5 minute flight would be enough time to get the picture and land while keeping a few minutes as a safety margin.

Quote 
Yes I was getting 144°F (62°C) on the Pletti. Too hot to touch.
Too hot to touch??? Here in Texas my car steering wheel is hotter than that when I leave work at lunch!

Now that your Joker is flying again come on down to Texas on October 10,11, and 12th for the AP conference. It's time for you to start taking aerial pictures! I ordered the parts for my mount Friday.

Phil
07-22-2008 06:21 AM
HOMEPAGE  
 
 
nooobs
Key Veteran
Location: Toronto, Canada

I really would love to come down but my MJ2 crashes has really set me back huge... Unless I win the lotto or something...
07-22-2008 07:20 AM
HOMEPAGE  
 
 
daytonabeach
Key Veteran
Location: Oslo, Norway

Phil, i see your headspeed are around 1450rpm, what pinion size do you have?

Chris

Never argue with an idiot, he'll drag you down to his level and beat you with experience...
07-22-2008 08:13 AM
HOMEPAGE  
 
 
phil007
Senior Heliman
Location: Austin, Texas

Quote 
Phil, i see your headspeed are around 1450rpm, what pinion size do you have?
I just checked to verify that it's a 20. It's running at 100% so I'll slow it down to about 1350.


Quote 
You you must look on your actro for a small end play of the bell, about 0.1-0.2mm (that you just can feel it). When the motor becomes warmer during flight the aluminium made bearing body is becoming longer than the shaft, so you can get a thrust force on the bearings that can cause a lot of friction and heat. So when you have washers between snap ring and front bearing adjust the play there if necessary. If not then replace the snap ring thru an 8 mm bush between bearing and gear wheel.

If you have that end play I assume your belt is tightened too strong.
And when it is currently very hot in Texas an additional electric fan is never a bad idea.

Gerd...thanks for that information and I'll take a close look at it. I'm also flying a MJ1 without the belt.

Phil
07-23-2008 02:34 AM
HOMEPAGE  
 
 
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