High Capacity, Low C Rating = Better for 12th 'Blinky'

well that's what they seem to be finding in 12th pan cars in the UK & US of A

So will the same hold true for the Mardave on 1s, 13.5BL and cheapo esc's like the Novak GTB etc on the list?

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We've done a fair bit of comparison work over the summer between the 6000mAh 28C and 5600mAh 60C packs and the feedback we had was that, in 10.5 'blinky' the 6000mAh was better over an 8 minute run than the 5600mAh. I've spoken to SMC about this and they also report that their drivers in the US (running in similar 'blinky' classes) also prefer the 6000mAh pack. The thinking behind this is that the higher capacity means less voltage drop during a run, in 10.5 'blinky' the current draw is relatively low so the performance limiting factor is the pack voltage rather than the available current (the C rating).

Interestingly the feedback also suggests that although the 5600mAh 60C is better for mod, the difference here is very marginal and certainly less than the difference in packs in 'blinky'. Consequently if you are on a budget for cells and don't want to buy different packs for different classes then you can't do better than the 6000mAh 28C (6028SI) as it has by far the lowest RRP of any of the homologated 1 cell packs.[/qoute]

Differant motors / differant gearing = differant results so for a dave totally differant

has anyone tried it with a Dave?

chequered_flag_racing wrote:has anyone tried it with a Dave?

No because

Differant motors / differant gearing = differant results

i think if he daves ran longer his would bt a consideration

12th car 64pitch gearing is 29/100 10.5 run time is 8 minutes
Dave car 48pitch gearing is 29/70 13.5 run time is 5 minutes

then the roll out etc you cant compare it

Nothing to do with gearing it is all a function of current draw. With boosted speedos and modified you draw loads of current so the cells ability to pass current IR that is the limiting factor to performance. In 10.5 & 13.5 blinky there is not enough current draw to worry a lower c rated cell so the voltage becomes the performace defining criteria. All 1s lipos start @ 4.2v but a higher capacity pack will hold up there voltage longer into the run.

Jason

Sorry Jason but current draw is just the same as amount of energy needed to start any veichle moving be it a model car a F1 or even a Bike

We have all seen what happens when an F1 car has the wrong gear off the line it bogs down . . .
Same as a Cycleist with a 20 gear bike
You would not start a car in 5th and facing up hill so gearing plays a massive part in model cars to little and its slow to big and its bog down and then just right for an all rounder

Gazza wrote:Sorry Jason but current draw is just the same as amount of energy needed to start any veichle moving be it a model car a F1 or even a Bike

We have all seen what happens when an F1 car has the wrong gear off the line it bogs down . . .
Same as a Cycleist with a 20 gear bike
You would not start a car in 5th and facing up hill so gearing plays a massive part in model cars to little and its slow to big and its bog down and then just right for an all rounder

Assuming you're not massively over geared that is irrelevent also electric motors are the exact opposite of a IC endine as they deliver their maximum torque at 0 RPM.
Yes you draw most current from a standing start, you should only be doing that once a race

Jason

jasonb wrote: they deliver their maximum torque at 0 RPM. Jason

Say What PMSL

Jason is correct, electric motors have maximum torque at 0 rpm. I suggest you research this instead of just discounting it. You will find it is true.

It is also correct that the voltage drop is the defining factor if the motor cannot draw anywhere near the maximum C rating of the battery. With both brushed and brushless Mardaves this will be the case, though in practice I think the difference will be so slight that it will be hardly noticeable. With lighter and more powerful 12th scales it is more so.

Trev

Pmsl big time.. . At 0 rpm nothing is moving weather its electric / I.C / Steam engine

Here is just the first of the articles that shows that it is true.

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Maximum torque is when the motor is stalled i.e. at 0 rpm.

However much you try to ridicule it doesn't change the facts.

Trev

Gary,

You don't need to have anything moving to have a torque applied to it! Think of trying to undo a stuck wheelnut on your road car - you put the spanner on and apply a force / torque. You apply more and more force / torque until it eventually comes unstuck, but up to that point you are applying torque even though the nut is not moving. The nut has zero RPM...

In an electric motor the torque it produces is proportional to the strength and direction of the magnet's magnetic field versus the magnetic field the coils can produce.

The magnetic field from the magnet of any given motor I am assuming will be roughly constant (ignoring the slight drop off with temperature cycles and age...).

However, the magnetic field that a coil of wire can produce depends on the thickness of the wire, length of wire, the number of turns in the coil and, most importantly, the current flowing in the wire. Wire and coil number will be a constant for a given motor but the current WILL vary!

At zero RPM your ESC is simply dumping whatever current it can handle through a length of copper wire. In other words, the current is MASSIVE since copper has a very low electrical resistance! Several hundred amps would not be unusual but this only lasts for a split second (which is why your ESC does not go pop!). Never the less, this huge current will give you huge amounts of magnetic field in the coils and therefore maximum torque.

As soon as the motor's rotor starts spinning though it will induce a 'back electro-motove force' (emf) in the motor's coils. This back emf works against the ESC's voltage so the 'net' voltage experienced by the coils falls. A lower voltage = lower current = weaker magnetic field = less torque. This is why any motor will have a maximum RPM for any given applied voltage - the net voltage across the coils (applied voltage from cells minus back emf) will produce just enough current / magnetic field / torque to overcome bearing friction, air resistance of the spinning rotor etc...

If there was no back emf the motor would just spin faster and faster and faster to infinity....

So, electric motors do produce their maximum torque at zero RPM.

Simples. QED. The Appliance of Science...

J

No matter how you look at it 0 rpm or a stuck nut on a car if you NOT moving its zero . Now if its stalled and 0 rpm and a stuck nut and you give it force . Now that's totally different

Gazza wrote: weather

Pmsl big time.. .

try whether

What is it with these phones that change words for you when they like ....With out asking me ....