Getting ready for .5 conversion

[FullMetalGrave]

Hi All,

I am getting ready to do a .5 crt conversion (still need to buy the car) and I have a few questions before I get started. I have a Mamba 4600 motor and Mamba Max esc that I would like to use so here are my questions:

1. To my understanding, the Mamba motor shaft is 1/8". After looking on this site at pinions, the only 1/8" pinion I see is the 32 pitch one for the E-Maxx. Will that work on the .5 crt or do I need a different pinion? I was just going to use the stock center diff and not change anything.

2. After reading a lot of posts, I see that the Mamba combo may have some issues with heat or not being strong enough. I am looking at running either a 2s or 3s lipo. What are the potential problems?

I won't be racing the car, just bashing with it. I appreciate any help.

[BrianG]

Welcome to the forums!

1. You can use any motor with a 1/8" shaft along with a bore reducer. The pitch for the CRT.5 is Mod1, so 32p won't work. Also, if you plan to stick to using the steel spur, you are going to want the hardened pinions.

2. Yes, the Mamba motors aren't robust enough to drive this without causing undue heat. A "true" S size motor is better (the MM motors are shorter and have less coils inside), or an L motor.. If you really want to use the MM motor, expect the motor and ESC to get kinda warm, especially in summer. Also, use a pinion no larger than 12T and stay with the stock size tires.

[FullMetalGrave]

Thanks for the welcome and the quick reply :)

Oh ok, thanks for clearing that up. I was seeing "Mod1" around but didn't understand. I thought it had something to do with the hardness of the pinion.

I know that I would definately like to play with the tire/wheel combinations and possibly end up with the extended chassis kit so I think I need a better motor that the MM. I don't want to be limited to a stock sized truck. Can you recommend a motor that would work well? I'm going to try squeezing a 6000-8000mah lipo into it for max run times. I think I understand that the more cells the cooler the motor runs...so a 3s would be the best bet? Sorry for the noob questions. My electrics all have Mamba's in them so this is a whole new world.

[BrianG]

Yeah, 3s on an 8L motor would be good, especially since you plan to play around with the tire size and make it generally larger. Also, a larger motor will be less sensitive to gearing changes.

[FullMetalGrave]

The other issue I have been reading about is "overdrawing" the pack. Do you think with an 8L, mamba esc and a 3s lipo I would have that issue? I have been using li-mn packs from Apogee and really liking them, here is what I was thinking of using in this setup before I went to a bigger Maxamps lipo (not even sure if the 8000mah will fit yet) https://pfmdistribution.com/secure/s...d=231&catid=57

[ilpufxit]

I have a Neu 5000mah 3s pack in mine. It absolutely screams but it's way too heavy to be practical. Extra weight causes breakage issues, trust me. With good quality lipos and a good motor, you should get good runtime and raging speed on a much smaller 3s.

Heck, mine with a 10.5 motor and a 2s lipo was good geared for about 30..... It was light, and wasnt over powered, but if I had the money it would be over powered lol....

I highly recommend the EXT chassis, its VERY nice

[Arct1k]

This is my setup... Works well with MM 7L


Differential Ratio: 3.25
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 16
Total Voltage: 11.1
Motor KV: 3511
Tire Diameter (inches): 3.75
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.0059
Spur/Pinion Ratio: 2.88 : 1
Total Ratio: 9.34375 : 1
Tire Circumference (inches): 11.78 inches (299.24mm)
Total Motor Speed: 38972.1 RPM
Vehicle Speed: 46.53 MPH (74.75km/h)
Effective Speed Rate: 4.19mph/V (6.73kmh/V)
Effective KV Value: 3511

[FullMetalGrave]

Would 9L or more be better? I found a bunch of Feigao's and they are all the same price. The range is 8L motors up to 14L that I can choose from. Also, I would like 3s (for speed/power), but it's not necessary if the 2s pack will perform well. I currently have a 2s 5800mah limn for my stampede that I can test with. I only need it to hit 35-45mph, but the runtime is what I'm after. I would like to try to get 30-45min per pack if at all possible.

[Arct1k]

I'd look for a 5mm 7/8L esp if you ever want to run 2s

Yeah, a 10.5 is around 4000 Kv give or take

Its a perfect 2s motor..... But I think 3s and a 8, or 9L would be perfect

[FullMetalGrave]

Then it sounds like the 8L is my best bet for 2s and 3s batts. Thanks for all the replies. This build should be interesting once I get the parts ordered.

Id order the one you can find the easiest.... But it sounds like you have that covered as well =)

Good luck with the conversion, and make sure theres pics

And BTW, welcome to the forums

I was just curious, in my crt .5 i'm running a Feigao 8L with my mamba, and currently using a maxamp 3s 6000mah, for racing on the track, but my question is would it be a worth it to try to drop to a 2s, or would the amp draw on my setup be to much for the 2s?

[Finnster]

The amp draw will be independent on the number of cells. It goes up a bit w/ more cells, but the change in power is from the voltage. If the pack is capable @3S, then the same cells in 2S would be fine.

I too would think again about the weight. A 3S 8000mah pack is really heavy. 4S 8000 packs are used in 1/8th scale conversions twice the size. If its really heavy the truck will drive poorly, be unbalanced, and break/wear parts quicker. I would try to stay under 250-300g at the most for the pack for the CRT .5. Its a pretty small truck, it quite a bit smaller than a 1/10 scale. Personally I wouldn't go over ~3200 cells for a 3S setup. At that point its better to just change packs. Also, if you have less weight, you need less motor and also keep things cooler.