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Old 06-02-2007, 04:52 PM   #1396
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TallyRC-I will be glad to test that hardcoat. I think I found some steel 12 tooth pinions of the proper length. Send me a PM if you ever get set up over there.

Mamba Max and Novak Velocity 3.5R
First the good news. I ran the car with the Mamba controller and the Novak 3.5 geared 90/12 just like I like. I ran it 4 minutes on a timer to check my battery temp as this was the limiting factor previously with the Max Amp Packs. I was using the Thunder Power Pack this time. The car was really fast. With this motor I can reach full throttle on the straight at about 1/4 the way because of the good weight transfer. Wicked Fast acceleration follows. With the 4.5 I was near 1/2 track before I could apply serious throttle. Temps were good. Motor at 167F. Battery at 125 F. Mamba at 150F which it has never exceeded.

Second run went 2 minutes and 20 seconds and the car stopped. The wires to the motor had come unsoldered. Two at the speed control, one at the motor. This is usually accompanied by a dead speed control. I resoldered. The car went about 10 feet and unsoldered again. TOAST.
I'll do some testing at home. I suspect the controller died as a recent internal inspection of the motor wires showed the wire insulation to be in very good shape. I backordered the LRP TC spec with the LRP 3.5 motor as the package seems to be the first that will be available. Sadly I am without backup due to a slow return of my GTB. It has been about a month now since I sent mine in for a non Warantee replacement.

At home, I have resoldered the wires. I took off the Mamba case to be able to do a better job from the bottom. There are no signs of internal damage. The system is working on the bench. I'll have to road test it again. The windings on the motor all measure the same .3 ohm. There are no motor shorts to the can. This is a bit baffling. Some extra friction could have caused the first meltdown at 2 minutes 30 seconds. But the second time it only ran 10 seconds before meltdown indicating a motor or speed control problem.

Rubber Sealed Motor Bearing
I installed one of the Boca yellow sealed bearings before the run. The pinionless motor spun up very nicely. The car was as fast as ever. I don't think you would notice this extra friction at all.

I completed test of the $1 Avid RC bearings in my 4.5R and 3.5R. The one in the 4.5R was very black inside, worn wobbly and gritty after 15 runs or so. It was failed. It is lubed with grease of which there was plenty left. The 3.5R motor put 16 runs on its mate. It was still OK, but when I removed it, it was just a little gritty inside. The grease was still clean. Failure from the grit soon to follow.

Last edited by John Stranahan; 06-03-2007 at 06:39 AM.
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Old 06-02-2007, 08:30 PM   #1397
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Exactly - and since most people, when they drive, have spin problems when they roll on the throttle and the rears want to spin, giving more forward grip (as opposed to rear grip) is a recipe for spinning out.

Oval is completely different from road-course. Oval can heat the tires and get purples to feel like greens. . . (exageration! ) and once you're at speed, you're pretty much at speed. In addition, Oval uses a LOT of adjustments to fine tune a specific movement.

Road-course has to deal with more variables and really has to deal with on-throttle spins. A forward-rake may be fine for Oval, but it's murder for Road-Course. With Road-Course, we tend to fight for rear traction on exit - we can't run those massive wings that Oval runs.

So - I'll qualify my advice to Road-Course applications - but it's still valid. Get forward rake on a Road-Course car and expect to spin out unless you are Deific with your throttle control. . .
I think that there are better ways of making this type of adjustment than raking the chassis rearward.

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Old 06-03-2007, 07:07 AM   #1398
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The windings on the motor all measure the same .3 ohm.

What does your meter say when you touch the two leads together?? You might want to try measuring the resistance from each motor wire to the case of the motor. This "ground fault" type of failure can be harder to find.
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Old 06-03-2007, 08:36 AM   #1399
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Kufman-I zeroed the meter with the leads touching. The .3 ohm should be pretty accurate I tested each lead to the case and got no continuity. Greater than 100 ohm. I did have a tire slightly rubbing in the corners from two loose screws. This could explain the first desoldering incident but not the second after only a 10 second run. More tests to come in the driveway today.
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Old 06-03-2007, 12:16 PM   #1400
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Hmmmm very intereseting. Is the controller really hot when this happens?? This is starting to sound like a break over in one of the FETs. Has it been the same two phases that come unsoldered each time?
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Old 06-03-2007, 02:01 PM   #1401
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Hmmmm very intereseting. Is the controller really hot when this happens?? This is starting to sound like a break over in one of the FETs. Has it been the same two phases that come unsoldered each time?
The controller is not hot. That is what I think it is. An internal break over in the controller. Same two wires.

It worked fine on the drive way but its hard to give it much throttle there.
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Old 06-03-2007, 02:02 PM   #1402
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Originally Posted by THE DARKSIDE View Post
I think that there are better ways of making this type of adjustment than raking the chassis rearward.

-E
I agree - I'm just saying that, just as you almost never, ever, want toe-out on the rear, you almost never, ever, want FORWARD rake - keep it level or slightly rearward.

There ARE some things that you just don't want to do:

Positive caster
Toe-out on the rear
zero droop
etc.

I would just add forward rake to that on a live-axle road-course car.
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Old 06-03-2007, 09:31 PM   #1403
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The controller is not hot. That is what I think it is. An internal break over in the controller. Same two wires.

It worked fine on the drive way but its hard to give it much throttle there.
john
It must be a whole bank of devices breaking over. If there was just one shorted FET, I think it would blow it right off the board before it would desolder wires. It could be a logic problem too. The processor could be telling the FET to do dumb things. Hard to say, yet interesting.
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Old 06-03-2007, 10:06 PM   #1404
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The processor could be telling the FET to do dumb things. Hard to say, yet interesting.
This is likely as the firmware was recently upgraded after a long series of succesful runs even with the same motor. The inside of the speed control looks very good. I wonder if some of these stuttering episodes are high current events. Anyway, thanks. I will test it on the track about Wednesday and give another report.
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Old 06-04-2007, 11:03 AM   #1405
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John
I think youre running a Spektrum receiver. I have seen a lot of curious things happening such as stottering and things when using a Spektrum receiver. It has to do with the ESC BEC also but some things are with any ESC. Try running a big 4700uF cap at the receiver, this helps with most issues. Best is using a Low ESR cap as used as power caps from the ESC. Im running this in all of my cars since about one year and never had a problem with the Spektrum again. Some of the problems seem ESC related on first sight but actually the receiver is the problem.

Yesterday I had the chance running my new Sphere TC Spec in my RS10G. This was using a GM 5.5T with sintered rotor and IB4200 cells on a very big track. Boy this is fast, much more fun than the brushed motors.
For the European guys, this was the same track as last years TC Euros.
The TC spec worked very good, didnt get very warm also. Programming is really easy also just the fan is a bit noisy.
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Old 06-04-2007, 11:16 AM   #1406
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John
I think youre running a Spektrum receiver. I have seen a lot of curious things happening such as stottering and things when using a Spektrum receiver. It has to do with the ESC BEC also but some things are with any ESC. Try running a big 4700uF cap at the receiver, this helps with most issues. Best is using a Low ESR cap as used as power caps from the ESC. Im running this in all of my cars since about one year and never had a problem with the Spektrum again. Some of the problems seem ESC related on first sight but actually the receiver is the problem.

Yes the old Spektrum receivers had the glitch problem mainly on carpet. we had couple people have problems on asphalt as well, So TeamGo Racing Made some power caps for us to use. and we didnt have any problems anymore. They should have it listed on their shop at www.rcteamgo.com

The new recievers are better and I didnt have any glitch problems since I swithced to the HRS version.
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Old 06-04-2007, 11:22 AM   #1407
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I have a spectrum capacitor in the box. Note that the spektrum had no problems with both a GTB controller nor an LRP controller. The pan car does not pull the big amps that a touring car does on corner exit. The big amps is what lowered the BEC voltage and caused Spektrum problems. The problem is not likely a spektrum issue based on good performace with two other controllers. I will run a 4700uFcapacitor on Wednesday just to see. My spectrum receiver is a fairly recent very small model.
John

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Old 06-04-2007, 11:34 AM   #1408
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Im not talking of the glitch problems on carpet what was solved with a newer software update. Some of the problems can happen even with the newest receivers. We had such a problem again here just 2 weeks ago what really looked like an ESC problem. After speaking with Spektrum tech here and using the big cap the problem disappeared. Using a 1000 uF cap didnt help.
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Old 06-04-2007, 10:29 PM   #1409
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Also have a go at running an extra capacitor over your ESC's battery input.
The GM ESCs suffer from all kinds of problems if you don't add enough capacitance at the input. It might also be an issue with your ESC.
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Old 06-05-2007, 12:20 AM   #1410
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Amp Max
They graciously replaced my prematurely weak battery after inspection. I tested the new battery which is their new copper connector model. Voltage was 7.25V at a 20 A discharge. 4238 mA-h (rated 4000). This was the best voltage ever for my LiPos although the Scorpion with some tinkering was the same.

Mamba Max with Capacitors
I put a 8200 uF capacitor on the Spektrum receiver. This protects it from any low voltage conditions. I put a huge Novak, approximately 9400 uF, capacitor on the Mamba Max input leads. This reduces voltage ripple at the battery and may help keep the battery and speed control cool, or it may not if it is mismatched somehow. Some of the earlier brushed speed controls did not like this treatment and ran slower.

I can tell you already that on the bench, if I roll on the throttle just so the motor will stutter. This is similar to my experience on the track. If you roll it on faster (like you would with more traction or 4-wheel drive) it does not. Battery temperature may be lowered.

Novak GTB Non Warrantee replacement
After an e-mail to prod them, Novak has shipped me a new GTB today blue label UPS. It should be here soon. That will be a happy day for me. The LRP sphere TC with an X11 3.5 motor is backordered and will ship when available. The delay was caused by me not shipping a motor in with the GTB system.

Boca Bearings
Boca has a $1.00 each line of bearings now. Some with rubber seals. I never used metal shields in the touring car, even in stock, because, frankly, they only last a week or so after they get dirty which is on first use. At this 1 week point they have more friction under load than a sealed bearing. I going to start using rubber sealed bearings on the pan car for the same reason. Some of these 1$ Boca bearings are ABEC #1 which is the lowest grade, but they do have specs available for them. I have not tested this cheaper line.

John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-mamba-max-capacitors-resized.jpg  

Last edited by John Stranahan; 06-08-2007 at 09:18 AM.
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