Modifications gone too far!

[mud4fun]

Guys, I guess I have reached the limit of mods to my thunderdragon (ref TD1 in showroom)....fitted a 14x2 motor, advanced timing for better torque, ran 8.4v thru it using a novak super rooster, using a 14t pinion - result - awesome performance, about 20% quicker around an oval test track than the same buggy fitted with the technigold. This sounds good so far.....problem was that I managed to MELT the solder contacts on the motor after just 5 mins racing so the motor leads fell off along with the capacitors EEK!

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Out of interest I ran several cars to compare performance results:

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Stock mad bull managed 23 laps/5 mins

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TB01 fully hopped up with 17T 7.2v motor ran 55 laps/5mins

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thunderdragon technigold 8.4v motor ran 57 laps/5 mins

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thunderdragon with 17T MDX3000 8.4v ran 59 laps/5mins

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thunderdragon 14x2 8.4v advanced by 5mm ran 67 laps/5mins just before it melted!

[WillyChang]

quote:Originally posted by mud4fun

...fitted a 14x2 motor,

advanced timing ...,

8.4v ...,

... 14t pinion

- result - MELT the solder contacts on the motor

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id="quote">id="quote">

Honestly, I'd rate it as "user error". [:I]

Modern mod motors aren't designed for 8.4V.

Plus when you use more volts and high gearing, you should have

decreased the timing - not increase it. Too much timing will

reduce efficiency... sucks more extra current than the

amt of extra power that comes out == HEAT.

If you're serious about idiotic horsepower, try Brushless.

[Pellandine-sports]

I hope that's supposed to be friendlier than it reads [?]

If you're still having problems then you could use silver solder instead of lead based.....silver solder has a higher melting point. However in your run, the melting of the solder might have acted like a fuse and saved you from a meltdown of geater proportions.......Do you have an emergency fish pond[?][]

[Top Force Racer]

I think the standard 60/40 solder melts at about 340 degrees F. That's pretty darn hot!

[WillyChang]

quote:Originally posted by Top Force Racer

I think the standard 60/40 solder melts at about 340 degrees F. That's pretty darn hot!

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Exactly!! [:0]

No hard feelings to anyone out there, but if your motor is getting

hotter than your soldering iron then definitely SOMETHING is wrong.

The only 2 times its happened to me was:-

1) a 540 with a shorted armature (manufacturing defect), and

2) a TechniPower with a really badly worn commutator

Mod motors do need constant maintenance.

And the hotter they get, the magnets lose strength quick too.

As for "idiotic" horsepower with no maintenance

you just can't beat Brushless. [8D]

[mud4fun]

Actually you are quite correct WillyChang, it was user error to a degree, tried the motor retarded but didn't give any performance increase so went other way which actually made a difference!. I was just pushing things a little too far to see what happened as this was a cheap old motor so I fed 8.4v thru it, it was great for 5 mins as the car was significantly faster but as with all these things speed comes at a price. I stripped the motor and the com is black. Solder certainly melted, that isn't an exageration.

[mud4fun]

I think you misunderstood the post though. This was a test to destruction anyway, it was my old thunderdragon and I wanted to take things to the limit before stripping it for parts. I always knew it was going to end up broken - it was a case of how fast could it go before it either fell apart or burst into flames......[] (The Novak ESC once more proved how good they are, it didn't overheat and works fine, I have tested it with another motor)

[mud4fun]

OK, I tested motor on bench and found the problem. One of the brushes had disintegrated so that under full throttle no power was going into the motor it was going thru the capacitor which links the positive and negative terminals. This in turn glowed red hot after just a second of throttle. This would have resulted in melted solder at the positive terminal. This also explains why the rest of the motor was only warm and the plastic chassis was undamaged! I fitted new brushes and cleaned up com and motor works fine! []

[Top Force Racer]

5mm of timing is what...approx 15 degrees? Try 20 degrees or another 3mm (approx) to eek out a few more RPMs!

[mud4fun]

LOL, TFR I think I've learn't my lesson! I'll go back to the technigold as it is the best all round package. Good power whilst retaining reliablity. Just need to get hold of some brushes for it now!

[madbad jezza]

hey guess what......

i fitted a tamiya super modified 11 turn motor to my turbo optima, and then ran it on a 2400Mah 8.4v battery pack - its went like badword!! - easilly accelerated as fast as a nitro buggy - but i also managed to melt the solder on the motor wires, causing them to fall off!. i fixed that problem, only to have the mechanical speed controller catch fire.......doh!!!!!!! - good job the bodyshell is easy to get off!.

sure is fast though, but boy does it get hot!!!!!!. with the motor timing advanced right-up, its completely mental to drive!.

fun with a capital F!. all i do now is keep a fire blanket handy whenever i use it.....

still, it,ll be good to melt snow with this winter.......

james. [)]

[WillyChang]

quote:Originally posted by madbad jezza

...i fitted a tamiya super modified 11 turn motor to my turbo optima -- melted solder

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Have a suspicion you're overgeared... that's the 1st symptom. [|)]

Bought a couple of the SuperMods this yr meself, for TCS.

They're not a "bad" motor per se, but methinks there's better

ones available for same price or less from non-Tamiya brands.

But that's the most powerful motor Tamiya makes.

What I did:-

1) left the stock cables in the box... ally bullet connectors??

Skinny wires?? No thanks - I put my own fat noodles on, with

copper bullet connectors. [8D] No warming up those!

2) brushes are screwed on with eyelets - ugh! Bad conductors.

Tossed them out and put new brushes on with twin-pigtails,

soldered on to the brushhoods. Also installed a schottky diode.

The PCB with the capacitors looked serviceable.

3) cleaned & polished the insides of the brush hoods,

when I discovered the brush hoods were *loose*... [?] so

4) aligned them up, slotted the spring posts to take a

screwdriver and tightened everything well

5) cut the comm - it wasn't too bad from factory

6) ran it in for about 20 mins @ 2.4V

The thing loves to rev, and even with the lowest ratio

available on the TB (34/96) it wasn't low enough to make

best use of the torque higher-up. There's a strong surge

of power as it gets on song, so car felt like some sort of

turbo-lag machine. Had to be sympathetic on throttle to avoid

overheating (tight track). So yeah, best don't over gear it.

Not a bad motor, but probably better ones out there if

one is not forced to use Tamiya-only stuff.

[mud4fun]

Hi WillyChang, better just remind you, you can't use schottky diodes with an ESC if your using the reverse function - well, it is not recommended and I believe invalidates the warranty on Novak super roosters/roosters? (I use the recommended 3 capacitors)

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Other than that I have now followed the same advice and fitted high quality silcon leads to the motor, soldered my brush contacts on and fitted high quality solid brass bullet connectors rather than the cheap aluminium ones. I also fitted aluminium motor cooling fins to try and dissipate some heat. This all seems to have worked together to produce a smooth revving, powerful little package! []

[DJTheo]

Diods may burn if you go backwards, but don't think anything would happen to a reverse ESC, I think they are only to protect an only fwd speed ESC if somehow the car rolls back and an opposite voltage is induced, but might be wrong, as I belong to the "racing speed controller with back-EMF" and "transistorized speed controler" era [8)][]

[mud4fun]

Hi DJTheo, it was just the fact that every manual I have for Novak and Nosram ESC's has big warnings stuck everywhere not to use schottky diodes with reverse ESC's - you have to take some warnings seriously. In fact, I burnt out a Nosram Tomahawk reverse ESC only a few weeks ago while testing a motor in a car I just got from ebay. I was very silly and hadn't bothered to fit the capacitors and left the original diode in place - tomahwak went up in smoke after about 30mins.........the motor was fine, no binding gears or anything in gbox, couldn't trace the fault. This same ESC had been used many times in other cars without problem.

[sosidge]

If a schotky diode is fitted, the car won't be able to go in reverse - if you pull back on the stick, you'll either blow the diode (good), or blow the speedo (bad), I've blown a couple of diodes over the yeras by wiring it backwards on a forward-only speedo - fortunately, I use a high-end model, and the speedo has survived. Cheaper models may not be so fortunate.

[mud4fun]

LOL, I guess I pulled back on the stick and option two happened - the ESC blew up!!! was never keen on those nosram ESC's anyway...I'll stick to the novak, they seem more rugged and able to withstand a bit more abuse.

[WillyChang]

quote:Originally posted by mud4fun

Hi WillyChang, better just remind you, you can't use schottky diodes with an ESC if your using the reverse function...

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yes you are right! []

Schottky diodes make the ESC run cooler.

But I don't have any ESC with reverse that can take a 11x3 anyway,

there's not many ESC-R out there suitable for a hot mod motor

(only 1 I can think of is the top line LRP F1). Also

ESC-Rs usually have higher resistance than an fwd-only ESC.

As for motor ratings on ESC, I never trust the "max" listed and

never run motors even close to any ESC's max ratings (if any).

When at the racetrack I don't need extra issues to worry about

so playing it safe & conservative is the best scheme.

The SuperMod was run on a Novak Cyclone (no limit) whose FETs

barely got warm. Can't believe this design is 7 yrs old now!!

[mud4fun]

I ONLY use Novak now as they have proved to be very reliable. I am doing most of my 'hot' motor tests using a super rooster. As you say, the FET's are quite cool even after running a 14x2 at race speeds for 15+mins. The price of these ESC's is dropping too, I picked up a super rooster the other day for £100 and a standard rooster for £50. I know you can get 'higher' spec ESC's for less but I'd rather pay that little bit more and get the quality. In my experience Novaks claims for ratings seem reasonable. You are quite correct about making sure that the motor leads and connectors are replaced with high quality/high amp ones. Since fitting Novak silicon leads and solid brass 'solder on' bullet connectors I have noticed the ESC and leads run cooler and the motor gives better response.