View Full Version : Gas speed Eletric speed
With would be easir to obtain a realy high top speed, Gas or eletric because the eletric has alot higher RPM and but seem's easy to burn up at high speeds, or gas with lower RPM but alot more power to get it moving.
corvette66
06-10-2004, 04:30 PM
My mom wears shinny shoes.
glassdoctor
06-10-2004, 10:01 PM
You're killin me, hee hee....
Mike Keeney
06-10-2004, 11:39 PM
Well I for one think that a nitro car will be the winner. But that's only cause that's what I'm bringing.
However, all the BS stops when the green flag drops. :eek:
Mike
Maxxcrazy
06-11-2004, 10:02 PM
I think electric would be easier to make go fast because all you need to do is add more cells. More volts=More RPM. That is, as long as the motor doesn't blow up
Chris LaPanse
06-11-2004, 10:06 PM
or if the SC doesn't get fried from the current
Nitro41
06-11-2004, 10:15 PM
An electric drivetrain weighs less, and has higer rpm, so I'm going with electric. (even though it can stay at top speed for only a few seconds)
the record of 111 mph was it reached by gas or eletric?
-mg
racerrandy
06-14-2004, 08:55 PM
It was electric. If you go to the start of the first thread you can click on the link and read all about it.
Chris Collens ran 112 in a speed run some time ago as well. It was a electric dragster running a 13x5 with 17 cells. This was on a 300 foot timed speed event.
Heavy Throttle
06-15-2004, 09:29 AM
Who needs a Speed Control, just hot wire that sucker to the motor and use a servo that will activate a switch to allow 100% battery power to the motor. Just use a regular 4 cell reciever setup for the radio gear in the car and walla. Smokin some tires...
DualBL
06-15-2004, 09:37 AM
^^ wouldn't work.
if you have enough power to get up to 150mph, and you try to unload it all at once, you'll certainly have enough power to break traction, and thrash your car.
-Nick
MegaMe
06-15-2004, 11:03 AM
i think he has a point - if you take it one step further a brushed motor on lots of cells with a mechanical speed control with some custom resistors (read massive heat sinked) could work IMO... but if you read my post in the stickied thread then you want to make sure that you wouldnt have to lift off the throttle for the corners...
dont know where you could get resistors like that though... as they would need to dissipate a couple of hundred watts i would have thought... hmm what do people use for battery dischargers??? :)
then again how much do high powered brushed esc's cost anyway???
would be a cheap way to put in an entry... if you could work out the bugs...
born2rc
06-15-2004, 12:38 PM
For electric all you need is 6 cells, on the way to the motor you put in a step-up transformer, all that would happen is your runtime would die.
racerrandy
06-15-2004, 05:31 PM
I wouldn't say it won't work, the 112 mph pass by Chris Collins was with a microswitch. It just wouldn't be the best for going around corners. Of course everybody is assuming that going around the corners is the only way its going to be done.
That 112 mph pass was done on a 300' standing start course, if you have 600 to 800 feet you'll get alot more speed.
Later,Randy
Martin Lee
06-16-2004, 06:55 PM
How about a potentiometer? When the knob is turned full clockwise, it has a very high resistance. When the know is turned full anticlockwise it has zero resistance (or close enough).
kenzo_1
06-16-2004, 07:50 PM
Potentiometer? Would be easier than building a mechanical speed control (basically a rheostat). I would love to try it out for myself if I could get one that could take the current and not fry.
Build one? Couldent you just use a small stock machanical speed control?
MegaMe
06-16-2004, 11:02 PM
it aint that simple... any potentiometer that i know of cant handle anywhere near the current required to operate an rc car...
secondly low resistance when the potentiometer is not nearly "low" enough... you see the specs of esc's that say they have an internal resistance of like .0something ohms, and why do you think people use fatass wires instead of little thin ones??? whereas a potentiometer set to 0 might have a resistance of 1 or 2 ohms... at currents that rc cars use - even tiny resistances will create lots of heat and wasted power... and massivly slow the car down.
btw if you did want to use a switch to power the car you would have to make sure the switch was beefy enought to handle the current running through it.
edit: with a mechanical speed control - you could probably use a stock one provided it made a really good connection - again because we want it to be low resistance - but you would need different resistors that could handle the massive power being dissapated through them.. think of a normal speed control rated at what 18 turns at 6 cells... now run it on 18 cells or something and then as in this instance power dissapated is proportional to voltage squared so you will need to dissapate 9 times the power...
the good thing is that i dont think it would be that hard to make custom resistors... i think just fat copper wire in a zigzag pattern strapped to the back of a big heatsink (like a computer heatsink) could do the trick (just make sure that the wire is electrically insulated from the heatsink so it dosent short circuit :) ) - although it would be a lot of trial and error to get the low power setting(s) to the speed you wanted.
i'm not sure about it though - i think they could work but i dont know how big a heatsink or how much wire you could need, or what thickness of wire would be best. the good thing is that probably the worst thing that could happen is that you destroy the resistor you have made if it dosent work right - so you pull it apart and try different wire :)
thats a good idea. I have a traxxas speed control and heatsunk its with 2cm by length 7cm and 1cm high. only used it twice.
Martin Lee
06-17-2004, 04:41 PM
Just use a beefy pot then, or even a rheo.
only thing about the machanical speed control is that they weigh more and the have a tendency to mess up some how.
only thing about the machanical speed control is that they weigh more and the have a tendency to mess up some how.
Some one said adout getting the highest speed with going around corners wouldent that kinda eliminate drag racers then?
Soupisgoodfood
06-25-2004, 10:10 AM
If you want to handle lots of power cheaply. I think the best way would be to use 3-5 microswitches. Each microswitch would only be connected to a few of the cells. Then arrange it somehow so that further around the serve horn rotates, the more microswitches it turns on.
dead-bird
06-26-2004, 02:25 PM
If one is intent on a mechanical speed control device, slot car controllers are much the same as the mechanical speed controllers in older RC cars. They can however sink much more current. A 100 watt, 1 ohm resister can sink quite a lot. Also a series of forward biased diodes work well as a stepped controller and are smaller/ lighter than the resister. The final link is a silver plated contact set that totally bypasses the controller supplying the motor with all available current. This might be a low budget alternative but I would worry about vibration and reliability in a complex mechanical device. There are a lot of wires and a few moving parts.