safe setup for a MMP?

[Semi Pro]

so here is my set up on my twinforce i built for my GF to drive when we go out bashing, i am wondering if i can get away with useing a MMP instead of an MMM.

im not going to lie, its a big heavy truck, but is set up to go slow and it will have about 60-70% punch control and medium start power

fully loaded and ready to run it 12.286 lbs and is geared for 32mph


here's the facts from brians calculator

Differential Ratio: 3.3076923076923075
Transmission Ratio: 2.36
Other Ratio: 1
Spur Tooth Count: 50
Pinion Tooth Count: 25
Total Voltage: 14.8
Motor KV: 1650
Tire Diameter (inches): 7
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0.01
Spur/Pinion Ratio: 2 : 1
Total Ratio: 15.61231 : 1
Tire Circumference (inches): 21.99 inches (558.58 mm)
Rollout: 1.41:1
Total Motor Speed: 24420 RPM
Vehicle Speed: 32.57 mph (52.32 km/h)
Effective KV Value: 1650
KT constant: 0.82 oz-in/A
Time to Get to Top Speed: 4sec
Usable Output Power: 343.39 watts (0.46 HP)
Input Power Required: 538.66 watts (0.72 HP)
Input Current Required: 36.4 amps
Motor Torque: 0.16 ft-lbs
Axle Torque: 2.47 ft-lbs
Average Acceleration: 3.58 inches/sec
Acceleration Force: 19.93 meters/sec^2
Acceleration Gs: 0.36 G
Required Motor RPM: 23990 rpm
Required Motor KV: 1621
KT constant: 0.83 oz-in/A


here are the batterys - 2 5200mah 30c packs for 14.8v
http://www.hobbyking.com/hobbyking/s...dProduct=10277

so judge and jurry, is the mmp going to be ok, or do i need to use a MMM?

[suicideneil]

I'd say MMM would be better- 30mph isnt blazing fast but with a ~12lb truck it sure feels like it is. What motor is that you're using?

[BrianG]

I agree. For one thing, the motor speed is kinda low for the speed you are getting. If I had to use a MMPro on a heavy truck like that, I would use at least 5s, and gear down for the same speed. Same power but lower current because voltage went up, and load went down (gearing).

[Semi Pro]

Originally Posted by BrianG

I agree. For one thing, the motor speed is kinda low for the speed you are getting. If I had to use a MMPro on a heavy truck like that, I would use at least 5s, and gear down for the same speed. Same power but lower current because voltage went up, and load went down (gearing).

if it were for me i agree it would be on 6cell geared down but i dont want it to accel to quickly, it's for a girl and maybe afew of my buddys who dont have rc's to drive

the motor is a Nue 1515 2.5D finned, i have the batterys allready and i dont want to change the stock battery trays to fit bigger packs

[BrianG]

How about running ESC settings at minimum? 100% punch control, lowest timing, dial in an exponential throttle curve. Then, set the radio EPA to ~75%.

MMP and a MMM are going for around the same cost on Ebay, within 20$ . You could basically just switch them out. Just an idea as that sure seems like alot of truck :)

[suicideneil]

Oh yeah, well be needing pictures too- its da law

[glassdoctor]

13lbs does concern me, but other than that I think you will be fine. I would gear it down a little, to just under 30mph. 25-30 is still fast for a girl LOL

I have run a truggy like that before with this same motor, and a MM, geared for 30. It was pretty heavy too, around 11lbs with a gigantic 4s 12,000mah battery. I had no issues with that setup. Even racing for 30min, everything stayed @ 150*

[Semi Pro]

Originally Posted by suicideneil

Oh yeah, well be needing pictures too- its da law

i know, i didnt post pics because i havent decided what color to paint the body yet (its really up to the girl and she is thinking blue or silver)


thats a good poing about gearing it alittle lower, the fast is i have the motor and the batterys all sittling around doing nothing, i know its not an ideal setup but im trying not to spend alot on this truck

the reason i as thinking of useing the mmp is that if she doesnt use the truck enuff i can always jack the esc and drop it in my mini revo or build a 6cell touring car( that project will get done this year one way or the other)

[Thomas Porfert]

It will probably be okay if you don't make long runs with the settings turned way down like BrianG suggested. A MMM would be a safer bet, but not as versatile in case it doesn't get used. Those batteries should get the job done, a newer (not worn out) set would be helpful. You may think about setting a 3.2 or even 3.3 volt per cell cut-off. Also be sure to keep an eye on esc temps. I wouldn't be surprised to see the fan kick on after heavy bashing for long durations; but if you allow some airflow under the body, it shouldn't be a problem.

It would be nice to have a data logger or watt meter to measure the current draw under heavy acceleration. There are going to be some pretty big amp surges getting that thing moving; I would suggest avoiding any tall grass and mud. Like others suggested, I would recommend that you drop the pinion down a bit. If everything runs cool on the lower gearing and you want more speed, you can always move back up. It's easier to put on a pinion than it is put the magic smoke back in the controller.

We really only intended the Max Pro to be used with buggies; but I think
the conservative setup and having the settings turned down will work just fine. Can't wait to see some pictures or even some video of it in action. Good luck!

Thomas Porfert
Castle Tech Support

[Semi Pro]

Originally Posted by Thomas Porfert

It will probably be okay if you don't make long runs with the settings turned way down like BrianG suggested. A MMM would be a safer bet, but not as versatile in case it doesn't get used. Those batteries should get the job done, a newer (not worn out) set would be helpful. You may think about setting a 3.2 or even 3.3 volt per cell cut-off. Also be sure to keep an eye on esc temps. I wouldn't be surprised to see the fan kick on after heavy bashing for long durations; but if you allow some airflow under the body, it shouldn't be a problem.

It would be nice to have a data logger or watt meter to measure the current draw under heavy acceleration. There are going to be some pretty big amp surges getting that thing moving; I would suggest avoiding any tall grass and mud. Like others suggested, I would recommend that you drop the pinion down a bit. If everything runs cool on the lower gearing and you want more speed, you can always move back up. It's easier to put on a pinion than it is put the magic smoke back in the controller.

We really only intended the Max Pro to be used with buggies; but I think
the conservative setup and having the settings turned down will work just fine. Can't wait to see some pictures or even some video of it in action. Good luck!

Thomas Porfert
Castle Tech Support

thanks for posting Thomas

i will start it with a lower gearing and watch the temps, the way the truck sits its going to get great air flow, my lipo's are bran new and im glad the here that they will be enuff....... funny to think of 30c all little these days