rk295

Hi,

I'm just building up my first touring car which I plan to run in the 17.5 blinky class. I see some of the blinky approved ESCs are 60A - is that enough or will a TC draw more power and need a bigger ESC?

r.

bd007

iTrader: (12)

Enough to run but won’t be fast or punchy enough.

the rc guy

60 amps will be fine.. since most motors people recommend 5-6 amp on the dyno with no load

gigaplex

iTrader: (2)

Those two numbers have nothing to do with each other.

5-6A on the "dyno" (actually an analyser) is a no-load current draw at steady state. The motor will draw a lot more current than that during acceleration, and it'll draw way more current than that when it's carrying a load.

jgil089

Yep 60amp is fine for a 17.5T touring car. I've heard a lot of different theories about how the ESC amps matter, but basically the ESC is a conduit, it doesnt push current into a motor or anything. A 17.5T won't draw huge current in blinky racing, so as long as you have a decent battery then it'll be fine.

A 160amp ESC might be faster, but not becuse its rated at 160amp, its because it is higher spec and will probably be made with better quality components and have lower internal resistance. For your first car you won't notice the difference.

I'm assuming your new to racing since its your first TC, so I would start with the 60amp ESC and when you are a consistent driver and chasing the fast guys then spend some money on new motor and ESC.

rk295

Thanks for the replies, thats all very helpful to know.

jgil089, it is my first touring you are correct. I race buggies normally, but just as I was about to hit buy on my 'usual' 120A ESC, I noticed it wasn't on the BRCA homologation list!

I was thinking of the Hobbywing XERUN XR10 which seems to be sensibly priced for a beginner and Blinky approved, just wanted to check the Amp rating was sufficient

Bry195

That is correct. why does 6 amps (unloaded) work for so many people on track if its a recommendation for setting timing on an unloaded motor?

gigaplex

iTrader: (2)

The majority of older motors (before everyone jumped on the short stack bandwagon) were track tested to find an optimal setting, then measured on an analyser to check the current draw. In general they drew in the ballpark of 6A. It was a pretty good rule of thumb back then, but with the shorter stack motors it's not always (but sometimes is) a good starting point. I think the Team Scream motors from a year or 2 ago were particularly sensitive, I've seen reports of them performing far better at the 3-4A range.

r_lud

Run the hobbywing juststock its fine got same good results on Nick Adams dyno compared to a hobbywing v3.1 just when braking the brake fade abit at low rpm but we’re still better then a lot of £100 plus esc . Also u shouldn’t be braking that hard in blinky all about keeping speed in the corners

but if u can maybe the hobbywing stockspec as has more options

I have juststock stockspec and xr10 pro g1 and g2
and only need the pros for mod

Bry195

this makes sense as to how it came about.

how much torque does it take to keep a motor spinning at a constant speed with no load?

I know you arent an advocate for the 6 amp method and neither am I. 6 amps at 8 volts and a resistance of x =allot of watts. if the torque required to maintain a speed is lower than the demand then where is something like 48 watts going? is there a significant amount of this 48 watts being converted to mechanical power? is this procedure is used (6 amp method) and it happens to coincide with peak efficiency of the motor how will it affect using it on track? what if it lands on peak power or lands on a terrible efficiency zone?

6 amps below 10k is almost all heat. there isnt a significant connection between the 48 watts being consumed and the power coming out because there is no torque. 6 amps works because it is directly tied to heat and has nothing to do with adjusting the power out. This wasnt an attempt to make it appear you believe in the 6 amp method. You can continue to disagree and claim you know better but can you debunk my explanation about heat? My point isnt that you can only have a max of 6 amps waste heat but since the number was generated on track over time its waste heat plus the waste of a motor running through efficiency curves on track.

gigaplex

iTrader: (2)

A steady-state no-load current draw of 6A is ~48W of pure heat (and some noise), since it's doing no mechanical work. By definition, since it's not accelerating, there's no net torque, so the only torque being generated is overcoming internal resistances.

Obviously it's going to draw more under load and while accelerating. The real questions are, how much more, and how much of that is mechanical work? A single no-load current value won't tell you that. To answer that, you need a proper dyno, or alternatively cut some laps and compare lap times vs temperature.

Using a reference no-load current value is only useful if someone else has done the work to figure out an optimal setting for the particular motor you're using, and you're just trying to replicate their setting.

Juan Aveytia

I use both the hobbywing 160A speedo and the 60A just stock speedo. The more expensive speedo has a smoother throttle feel. But the just stock is great. Lap times are the same. Punch is the same out of the corners. Top speed feels he same. If you want to Save money, your really not limiting yourself using the Just stock speedo.

Bry195

thats correct as I stated up until you say no load is of no use.

2 guys go to a short track and run laps that are fast and the motor DOESNT OVERHEAT at 5 amps but does at 6.
They then take the same motor to a long track and find 5 amps doesnt generate enough power so they go to 6 and it doesnt overheat.

now we calculate or run a dyno and find that the efficiency looks like this


5000 rpm =40% efficiency 10000 = 60% 15000=10% at 42 degrees of timing and to run a ten second lap the motor needs to average 7500 rpm. what is your average efficiency?

so now we go to another track that requires an average rpm of 12500. we set the timing to 52 and the efficiency looks like this, 5000=30% 10000=45% 15000=30%.

with the low timing on track 2 what is going to happen and how do you respond? yes you go to 52 because on the average you spend more time at 12500 than 7500.

with high timing on track 1 whats going to happen?
why does the test that was done years ago on an unloaded motor work? because when they did the testing they ran on track 1 and 2 which means the 5 amp and 6 amp number takes into account the average time a motor spends working under load and then tested it unloaded. There are a million examples why 3.8 might work better but all of them come from someone doing a loaded test to a heat limit and then checking the info unloaded.

the 5-6 amp method does not replace timing and gearing and backing down when you hit the temp limit but those 5-6 amps are a starting point based on testing different motors on different track under different conditions to an average rpm. if the efficiency curves from the original test motors are similar and the thermal capacity are similar then the mechanical work is arbitrary because its assumed. Find a motor with a different curve and you will find a motor that the no load amps will be different.

gigaplex

iTrader: (2)

That's not too different to what I said though.

Starting with 5-6A and tuning from there because you know that it has already been track tested (either with the same motor, or with a similar performing motor) is not that different to just starting with a known good endbell timing value. Personally, I'll use the endbell that the manufacturer set as default as a starting point, but it doesn't really matter where you start, it matters where you end.

The problem is, most advocates of the 6A method just set the motor to 6A and run it like that. The Nick Adams reviews in particular will set every single motor to 6A and compare them at that setting, which heavily favours motors that work better at those timing settings.

nexxus

iTrader: (315)

Ok lets summarise:

Yes in normal circumstances 60A is fine for Blinky, *But* if your motor is screwed (ie stator busted or solder bridging two phases) it WILL pull more amps and can potentially blow the ESC. A 5.5 turn motor free revving on your desk will pull less amps than a 21.5 in your TC on the track. Amp load is what is key and there are more factors than you can point a stick at here. Drivetrain efficiency, car weight, motor condition, even battery condition will affect ripple current.

Setting at 6A on your analyser, is essentially being a lemming. If you want to race like a mindless drone, have at it, Nick Adams is king, all hail...... you get the idea.

The most vocal self proclaimed experts on here also frequent the B main in antiquated and poorly maintained cars that probably should be kept in the car park. TT-01? Not quite, I think I heard TC4, which was a great car 15 YEARS AGO

And remember, you're asking a bunch of people behind a computer to tell you how to play toy cars. Sorry but it is what it is. Don't over think this s@it, All the motor tuning in the world and super low resistance ESC is worthless if you bin it first corner.