Cole Trickle

Hmmm, I think the point are obvious....

In those touring cars, we got several rotating components: 2 diffs, an armature and 4 wheels. The gyroscopic effect of each of those compononents are way larger than the gyroscopic effect of a spur gear.

Reducing the size of the spur gear by 10 teeths, will theoretically have an effect. However, compared to the other rotating components, the effect are almost invisible....

The motor represent approx. 10% of the total running weight. So I have absolutely no doubt: Lowering the motor and thus the CG, are much more important.

schumacher

cole,

your getting confused between gyroscopic forces and moments of inertia.

moment of inertia is a measure of how much energy you need to give an object to get it rotating.

gyroscopic forces are those which resist turning. This is how your pushbike stays upright, the gyroscopic forces hold the thing upright.

Do you seriously think lowering your motor mount is going to give you more punch?

it won't. might give you better handling but thats dependent on your car, my Yok, TC3's etc have the motor in the same place so in that respect using a smaller spur gear is more efficient.

sanj

Cole Trickle

True, I mixed it up. I meant moments of inertia. But it changes nothing. The advantage of lowering inertia by using a smaller spur, are still extremely small, compared to the moments of inertia in the other parts I mentioned.

I've never said that lowering the motor will give more punch. But it improves handling, and that are much more important than a theoretical lower moment of inertia.

Cole Trickle

You're right about that the CG only are affected on some cars (I've already mentioned that earlier). The motor always change position, when gear mesh are adjusted, only the direction differs. On a TC3, the motor gets closer to the center, when using a smaller spur, so in this case you'll get the advantage of weight more centralized. If I'm right about the Yoke, the motor will move in the front/rear direction, thus again affect the handling.

John Stranahan

iTrader: (27)

The efficiency of a spur pinion gear is affected some by the angle at which the teeth make contact. This loss from angles that don't act exactly on the circumference as well as frictional losses produce a 3-5% efficiency loss with each set of gears. This is why pan cars are faster accelerating than cars with a transmission. There is probably a good balance between the efficiency losses which are higher with a smaller spur and increased rotational inertia which are higher with a bigger spur. Manufactures don't use tiny spurs for this reason.

Most RC cars that I have run will not tolerate a ten tooth change in the 48 pitch spur due to lack of adjustablility in the motor support or lack of availability of the small spur.

Cole Trickle

Hi there

Some new thoughts on this...

Racing in stock, with plenty of capasity, is there any reason to NOT use the lowest possible frequency, to gain as much punch as possibly? Im' thinking of 244 Hz...

Some have mentioned comm wear. If I usually use approx. 4 kHz and are happy with cutting the comm every 10-15 runs, how many runs would I be able to do with 244 Hz?

Thanks.

Mabuchi540

No matter the acceleration advantages/theories etc about this issue surely the main advantage of a smaller spur/pinion to obtain the same ratio is not in the get up and go department but in the OMG I need to stop department.

Terry_S

iTrader: (3)

I see this is quite an old thread (2003!) things have moved on with competition ESC designs.

The new ESC I'm involved with developing has what we call a 'Dual Active' response where the drive frequency is actively adjusted along with the throttle response according to the throttle input and the current draw of the motor. The result is improved performance without significant additional comm wear!

Joe B

iTrader: (1)

Yea dosn't the quantum 2 have a similar set up(reactive software or something)........From what Iv'e seen ,I still perfer an adjustable one, with whats out there now anyway........

Terry_S

iTrader: (3)

The Quantum2 is one of a few ESC's that adjust the drive frequency. It's usually a 'stepped' change in frequency (quite large steps) or a fixed programmed frequency change (preset or user defined) according to the throttle position. Rather crude and limited in the performance advantage gained.

The best solution I would suggest is the option to select a fixed but adjustable drive frequency or an 'active' frequency or various other user programmable options.

The proof in the end is the performance on-track, in the end nothing else matters.

Cole Trickle

Well, actually the CS Rocket MAX was avaible when this thread was started. And it also have auto variable drive frequency.

Terry_S

iTrader: (3)

Yes variable frequency and auto variable frequency have been around for a while now, however that's only a part of the operation of an ESC there is also the throttle response to consider and how it works with the varying frequency. The Q2 varies the frequency in response to the load on the motor, that's useful but it's how effectively it does this that's important and effects the performance you get on the track.

Terry_S

iTrader: (3)

I say yes a lower drive frequency makes a difference and it could be worth looking at other ESC's. Maybe users of KO and Keyence ESC's could also help you with their findings?


Less runs than 10-15 I'd say, most likely a lot less.

asw7576

When we race modified 8T last year, my friend can't get full 5 minutes. His car crawled over 4 minutes..... the battery was depleted.

After thorough inspection, he forgot to re-program drive frequency from stock to modified, or something like 2 KHz to 16 KHz ( don't know exact number in his ESC ).

After reprogramming the battery could last nicely just close to 5 minutes..... slightly crawl though.

Some says, lower drive freq. gives the most punch, but I can't hardly notice it at higher freq.

Cole Trickle

Thanks, I've always wondered by what principle the QC2 worked with. The Rocket Max reacts based upon how fast you move thr trigger - fast movement translates into acceleration, thus low frequency, while slow movements translates into high freq., smoothnes. But perhaps you already know that

I'm wondering about LRP IPC SR and v7.1; Both are operating at 3140 Hz, but the SR is supposed to have more punch (for stock) than the 7.1. Can someone explain how this happens?