Hey -- what's the purpose of that giant 50-gallon drum size cap on the Novak GTB ?? Is it needed for 4-cell brushless ??

Thx

Jeff, Bob Wright says he don't run any cap on his, I've been thinking of taking mine off

Jeff, Bob Wright says he don't run any cap on his, I've been thinking of taking mine off

I was wondering about that -- the GTB has at tag on the wires that says DO NOT run it without the cap, and the instructions say that at least 3 times.

So.... why is it on there and why does Novak get so hyper about saying it MUST be connected ??

Good Question but I'm surely not smart enough to answer it

I doubt it does much with a 4300 and i'm going to try running without it this weekend, but I know that when you run the GTB with the motors it was designed to. the 5.5 and such, that cap get's HOT so it has to be doing something.

OK -- I'm going to be running it with the 13.5 in stock -- not even the 4300.

So you think it has something to do with heat dissipation rather than a performance issue ??

Jeff, Bob Wright says he don't run any cap on his, I've been thinking of taking mine off

I took the cap off before I even put the thing in the car.I also removed that huge heatsink and covered the top with a piece of .020 lexan. Ran at the Triclone in the heat and hung a big gear on the 4300 with no ill effect. There are several others running this way also,Hays JR,Butch Thompson and I believe Phil Beardshear. If you plan on running the 13.5 I see no reason to have either the cap or the heatsink on the speedo.

I took the cap off before I even put the thing in the car.I also removed that huge heatsink and covered the top with a piece of .020 lexan. Ran at the Triclone in the heat and hung a big gear on the 4300 with no ill effect. There are several others running this way also,Hays JR,Butch Thompson and I believe Phil Beardshear. If you plan on running the 13.5 I see no reason to have either the cap or the heatsink on the speedo.


Thx Bob -- well then exactly what does it DO ???

We tried running without it (Jamie Hanson & I) in 4-cell 4300 and both of us managed
to thermal. . . .

You should run it.

All a capacitor does is store energy until the throttle is pressed again, its kinda like a booster, throttle on and all energy goes to motor, throttle off and energy builds in the capacitor then with the pull of the trigger all energy is again sent to motor...........

It does not ever appear to be that great of a difference but I don't think it would have any effect on THERMAL if you had it or not...............

SOLID TRIGGER no need, On Off Trigger could help out.............

NOW NO HEAT SINK ON IT MAY CONTRIBUTE TO THERMAL

All a capacitor does is store energy until the throttle is pressed again, its kinda like a booster, throttle on and all energy goes to motor, throttle off and energy builds in the capacitor then with the pull of the trigger all energy is again sent to motor...........

It does not ever appear to be that great of a difference but I don't think it would have any effect on THERMAL if you had it or not...............

SOLID TRIGGER no need, On Off Trigger could help out.............

NOW NO HEAT SINK IT MAY CONTRIBUTE TO THERMAL


OK. thx.

So why is Novak so insistent that the cap be used ???

OK. thx.

So why is Novak so insistent that the cap be used ???
My Guess.... its a CYA statement to avoid all the phonecalls/emails they'd get if the power did "drop out" and cogging/lag started.

As John said above, I had tried the speedo without the cap and it shut down due to heat. On a track like triclone, it may not be as much of an issue because of the constant throttle. I do think you will have to run the cap on a track where you are on and off the gas much more.

http://en.wikipedia.org/wiki/Capacitors

Here you go the Encyclopedia Version of Capacitors.......

Very informative!!!!!!!!!!!!!!!!!!!!!!!!!!

As John said above, I had tried the speedo without the cap and it shut down due to heat. On a track like triclone, it may not be as much of an issue because of the constant throttle. I do think you will have to run the cap on a track where you are on and off the gas much more.

If the blue wire is disconnected thermaling the motor is not an issue. I've never checked the temp of the speedo but I would doubt that it would heat up enough to go into thermal shut down. It hasn't been an issue for me.

What kind of track did you and John have a problem on? I'm assuming from you post it was a short track with a ton of bite where you had to lift. Were you on pink/purple tire combination?

i know on the non brushless gtx they say all the stuff run with cap donte rmove but i have had mine off for 3 races know and lap times are still the same...

All a capacitor does is store energy until the throttle is pressed again, its kinda like a booster, throttle on and all energy goes to motor, throttle off and energy builds in the capacitor then with the pull of the trigger all energy is again sent to motor...........

It does not ever appear to be that great of a difference but I don't think it would have any effect on THERMAL if you had it or not...............

SOLID TRIGGER no need, On Off Trigger could help out.............

NOW NO HEAT SINK ON IT MAY CONTRIBUTE TO THERMAL

This is sort of correct.

The way these digital speed controls work is by switching the fets on and off very fast, the drive frequency that is talked about with these speedo's is the frequencey at which the fets are switched on and off. If you were to look at the output from these speedo's on an oscilloscope you would see a square curve. where the voltage goes from zero to full voltage back to zero to full voltage again, it would repeate that cycle at the frequency that your drive frequency is set at. Heat is generated in the nearly infinetly small time that the fet is switching from zero to full power. In a perfect world that swtich would hapen in zero time and all is well, but actually there is a huge amount of current that is required to switch from zero to 5 volts in nearly zero time and that generates heat. It is for such a small time that it really doesn't hurt things much and fets have been doing work like this for years. What the capacator does is help smooth out that transistion a little bit and help with that heat generation. If you are running at a lot of partial throttle applications then a cap would help reduce the heat generated by the fets in the speedo, but since we run wide open nearly all the time it probably doesn't matter to us. Not saying it's okay to take it off, just saying what it does.

Latemodel was correct in saying it stores energy when the throttle is lifted but it's not really when you let off the trigger, it's when the fets switch off. Same idea just way faster than we can do with our triggers.

Very good answer! The instructions clearly state it is for heat disapation.

This is sort of correct.

The way these digital speed controls work is by switching the fets on and off very fast, the drive frequency that is talked about with these speedo's is the frequencey at which the fets are switched on and off. If you were to look at the output from these speedo's on an oscilloscope you would see a square curve. where the voltage goes from zero to full voltage back to zero to full voltage again, it would repeate that cycle at the frequency that your drive frequency is set at. Heat is generated in the nearly infinetly small time that the fet is switching from zero to full power. In a perfect world that swtich would hapen in zero time and all is well, but actually there is a huge amount of current that is required to switch from zero to 5 volts in nearly zero time and that generates heat. It is for such a small time that it really doesn't hurt things much and fets have been doing work like this for years. What the capacator does is help smooth out that transistion a little bit and help with that heat generation. If you are running at a lot of partial throttle applications then a cap would help reduce the heat generated by the fets in the speedo, but since we run wide open nearly all the time it probably doesn't matter to us. Not saying it's okay to take it off, just saying what it does.

Latemodel was correct in saying it stores energy when the throttle is lifted but it's not really when you let off the trigger, it's when the fets switch off. Same idea just way faster than we can do with our triggers.

Thanks !!! this is the kind of info I was looking for.

I'm going to try running it with the cap off with the 13.5 motor and see what kind of temps the ESC gets to -- if it's not too high, I'll just run without it I think.

So if you were just oval racing and most of your racing was done in the full throttle all the time what if you just put a smaller cap on it like the lrp has or novak has some smaller ones

If you were full throttle all the time I don't think it'd matter how big a cap you have on the car, i don't think it'd get used much at all.

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This is sort of correct.

The way these digital speed controls work is by switching the fets on and off very fast, the drive frequency that is talked about with these speedo's is the frequencey at which the fets are switched on and off. If you were to look at the output from these speedo's on an oscilloscope you would see a square curve. where the voltage goes from zero to full voltage back to zero to full voltage again, it would repeate that cycle at the frequency that your drive frequency is set at. Heat is generated in the nearly infinetly small time that the fet is switching from zero to full power. In a perfect world that swtich would hapen in zero time and all is well, but actually there is a huge amount of current that is required to switch from zero to 5 volts in nearly zero time and that generates heat. It is for such a small time that it really doesn't hurt things much and fets have been doing work like this for years. What the capacator does is help smooth out that transistion a little bit and help with that heat generation. If you are running at a lot of partial throttle applications then a cap would help reduce the heat generated by the fets in the speedo, but since we run wide open nearly all the time it probably doesn't matter to us. Not saying it's okay to take it off, just saying what it does.

Latemodel was correct in saying it stores energy when the throttle is lifted but it's not really when you let off the trigger, it's when the fets switch off. Same idea just way faster than we can do with our triggers.


The cooler the FETs in the speedo the more efficient the faster your going to be its that simple.
Most guys run fans on there speedo.

I would run the BIG cap because power lost on the FETs cause by heat is exponentiational.

I see most team drivers running even bigger caps on there speedo.
Every little bit counts. Right??

I can find other areas to lighten your vehicles weight.... :)

the cap on recharges if your off throttle.. they are mainley used for sedans, or 12th scale.. or even mod.. there is very little to no difference in performance.. Ive had many esc.. Ive run the caps, and not run them, and have never had an issue either way..