Any brushless/maths experts out there.

[bigoggy]

I have a 2wd shortcourse truck, it does 33MPH, with the included 3000, 8.4v battery, and 12 turn 550, brushed motor.

How can I work out what these changes would do to the speed?

2s 5600 LIPO.

10 turn brushless motor, with 2s 5600 lipo.

10 turn brushless motor, with 3s LIPO.

Is this something that can be worked out, or is it just try it and see?

20 tooth pinion, 84 tooth spur gear.

[SteveU30]

If you know the Kv rating of the brushless motors (should be in the spec sheet) you can work it out the max RPM using the following formula:

Kv= RPM per volt.

[wolfdogstinkus]

Kv X voltage = RPM

2000KV X 7.4= 14800rpm about the same as a silver can?

A 2s lipo will make a massive difference, in my very basic tests, a 2s lipo almost doubled my top speed. although that was compared with a worn out 3000mah 7.2V Ni-mh.

Cheapest bang for buck would have to be a 3s lipo and charger, if your ESC can handle it?

[bigoggy]

Here is the motor.

[wolfdogstinkus]

3930 X 7.4 (2s lipo) = 29082rpm

3930 X 11.1V (3s lipo) = 43623 RPM

[bigoggy]

Thanks, that helps.

This LIPO and brushless stuff is hard.

Give me a Tamiya sport tuned motor, and a 5600 NIMH, I know what I'm doing then.

[wolfdogstinkus]

Wait till you try lipo though, you won't want to go back.

It's like having NOS, ok not quite laughing gas but it will make you smile. :D

Have you bought tyres yet?, you will need to. :D

[MadInventor]

Thanks, that helps.

This LIPO and brushless stuff is hard.

Give me a Tamiya sport tuned motor, and a 5600 NIMH, I know what I'm doing then.

4000KV and 3S LiPo in my gravel hound did give me something over 50mph, but I had to put TT-01 gearing in it to achieve that, and it's a lot lighter than an SCT. The 10 turn motor you have there also has a 380 sized rotor, a 4000KV 10.5T motor will have a 540 size rotor which will give you more torque, which on it's own is likely to make a difference to the speed of a heavyish SCT. If you want to go LiPo, see what the largest battery is you can fit in the vehicle (3S will give you a massive speed increase over 2S or 8.4V NiMh). To put it in perspective, a 3S LiPo running silver cans in my Jugg2 was much faster and punchier than running it on 8.4V NiMh and 19Turn racing motors. With the 3S LiPo the jug could do standing backflips on sivler cans . If nothing else, I'd simply try the existing motor with a 3S LiPo, if you have a speedo that will take 11.1V on a 10 turn brushed motor.

[berman]

Since you mentioned a "3000 8.4v and a 12t 550" I am guessing you have one of these:

Mine has 86/23 gearing and a 3800kv 4 pole and on 3s does about 80 kph (oh and wheelies )

[bigoggy]

This is the car in question.

[Klausen]

Here is a great top speed estimater.

http://www.scriptasylum.com/rc_speed/top_speed.html

[Wooders28]

I swapped to lipo and never looked back.Mainly as I went straight to 3s from a 7.2.

Struggled to find a lipo to fit a df03 chassis,but found this worked with minor alterations :-

http://www.modelsport.co.uk/orion-rocket-sport-3s-3200mah-25c-11.1v-lipo-uni-plug-/rc-car-products/373639