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Old Jan 15, 2005, 12:37 AM
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Durban, South Africa
Joined Feb 2004
60 Posts
Lipo wiped out!

Took my Reno Racer racer up earlier today. It is powered by a 3s2p 2200mAh lipo pack, with Skyborne 14 speed controller and a Hacker Sprint motor.
This plane REALLY moves, it's like a bullet (used to be!)
Had been flying for about five minutes when the motor went to full power. I lost control over the throttle control completely. So I thought, the best action would be to just run the battery down at full throttle, as the ESC has a lipo motor cutout. I climb the plane up high, for an easy glide in, then 30 seconds later I lose all control and the Reno Racer goes straight into the ground at full throttle. What a terrible sound, and pieces flying in all directions.
The amazing thing is, the lipo looks wrecked, see the picture below.
I decide to play it safe, and do as all of the threads have suggested, and move the battery to an open space for 30 minutes. Nothing happens, good.
Another amazing thing is nothing leaked out, even though I can see inside the cell, and it still has an 11.5 volt charge!
I realise now that the ESC decided to un-solder itself in the air, as can be seen by the solder spattered inside the nose cowling. I can't figure this out, as the ESC is rated for 14 amps, and I have statically tested with a meter at full throttle on the gound and only 10.5 amps was being drawn. Maybe the speed controller was just faulty.
The motor still has both it's brushes attached, and was still screaming at full speed on impact.
Does anybody have any ideas?
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Old Jan 15, 2005, 04:46 AM
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vintage1's Avatar
East Anglia, UK
Joined Sep 2002
29,689 Posts
Afetr a similar thing happened to me, I cut up pieces of an old EPP plane and put then betweebn the battery and the motor to prevent the battery damage you have.
As to why it happened? enclosed fuselage and no cooling and maybe a motor that needed a drop of oil on its bearings could have been drawing more current than you think, and the ESC geting hotter.
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Old Jan 15, 2005, 06:15 AM
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Durban, South Africa
Joined Feb 2004
60 Posts
The foam between the pack and motor is a good idea, it might just save my pack next time.
And I suspect you are right, the ESC was stuck to the underside of the top of the fuse, and probably did not get enough cooling air.
Amazing how hot it got, I examined it after posting, and most of the solder on the board has gone, it just melted away.

Thanks for the input.
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Old Jan 15, 2005, 08:37 AM
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mlehman's Avatar
United States, FL, Cape Coral
Joined Jun 2002
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That is a shame..I love my reno racer..



Mike
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Old Jan 15, 2005, 08:47 AM
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JoeC's Avatar
Long Island
Joined Oct 2003
199 Posts
While you should have had more cooling, the source of the heat may not have been the motor current. The fets driving the motor are used in switch mode. They are either on or off so they don't tend to generate a lot of heat unless you run it at full throttle all the time, and draw the max current.

Your problem might have been the number of servos. The regulator for the radio/servos is linear. That means that the heat it generates is equal to the amount of current draw times the input voltage minus the output voltage. If you have 4 servos in that plane and it's fast so it generates high loads on the servos, thay can draw quite a bit of current, over .5A each. (The stall currrent on an HS55 is around an amp) If you figure it out thats: (Using 10V for the battery under load)

(.5 * 4) * (10 - 5) = 10W

10 watts is a lot of heat on a small ESC board, especially with too little cooling. One thing you should do before flying a new setup is to check the heat on the ESC after twidling the sticks around for a while when it's on the ground. Don't run the motor, that will lower the battery voltage. Make sure all the control linkages are moving freely, without any binding.

You will be suprised how quickly the ESC will heat up just from the servo loads.
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Old Jan 15, 2005, 11:31 AM
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Durban, South Africa
Joined Feb 2004
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Hi Mike, a big shame, but luckily I have another Reno Racer still in the box. Will start building it tomorrow. This plane has so impressed me, after hanging on my wall for over a year I decided to give it another go, and it's very, very fast and aerobatic.
With a Hacker Sprint 400 motor, a GWS 5x4.3 prop and a pack of 3s2p 2200 lipos the Racer achieves full on vertical.
And thanks for the tip JoeC, I will definitely try the servo only trick. The Reno Racer only has three servos, but you never know, anything to calm the nerves down a bit and prevent another big bang...
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Old Jan 15, 2005, 11:42 AM
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United States, FL, Cape Coral
Joined Jun 2002
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I only use 2 servos on my Reno..The rudder isn`t used. I also used hot glue to assemble mine..that stuff really sticks to the plastic fuse. I had to drop down to an APC 4.5-4.1 prop on the stock motor with a 3s TP2100 pack to keep the amps down ..I now use an older Astro 020 pylon motor and an APC 4.5-4.1 prop..

Mike
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Old Jan 16, 2005, 09:35 AM
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Durban, South Africa
Joined Feb 2004
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Hi Mike,
I find the rudder handy for doing stall turns, and with my new lipoly's I can fly the Reno knife edge, where you also need the rudder.
I also have landing gear, so it's nice to have a steerable tail wheel when taxiing.
Clive

Thats's interesting to know, about the hot glue, thanks. I tried, and failed to get anything to stick to the fuse.
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Old Jan 16, 2005, 09:44 AM
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United States, FL, Cape Coral
Joined Jun 2002
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I used the hot glue to reinforce the area around the rear wing saddle beside the wood plate..the reno is a little weak there

I just hand launch mine.with the lipo it launches well.I just speed around with mine for a couple mins then go back to a 3D plane..then back to the Reno..it is a nice change of pace
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Old Jan 16, 2005, 11:39 AM
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San Jose Ca / RSA flyer
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Left Hand Temperature Control

I would say the brushes disintegrated in the motor by too much throttle by your " LEFT HAND " not using temperature control, Vinnie will tell U .
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Old Jan 16, 2005, 12:37 PM
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Durban, South Africa
Joined Feb 2004
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I had to stiffen the wing saddle with balsa. as well, but ended up putting small screws through the fuse into the wood.

The brushes are both still in place...
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