Not happy with Brushless Jato :(

Well, converted my Jato to brushless last night in a few hours.

For the innitial attempt I used:
-Mamba Max speed controller
-Mamba Max 7700Kv motor
-17t pinion
-55t spur
-Venom 7.2v 3300mAh pack

All of the above was brand new..

Anyways, I got everything setup and ready to rock, calibrated the ESC... Went for the first test spin around the shop, first thing I noticed was the motor sounded very weak and was obviously not getting anywhere near the RPM that my 18th scale Mamba's were getting.

Continued driving, still not impressed. I was probably getting 25-30mph top speed, if that.

After a total of about 30 seconds of driving, the truck stopped dead. No response at all......

After some looking into the problem, the BRAND NEW, 30 seconds of use speed controller is completely DEAD! :mad:1

I fired off an email to Castle Creations in regards to warranty. I am expecting it to be replaced no charge!

Anyways, I'm hoping someone can re-assure me that this thing WILL be faster than the 25-30mph I saw during the innitial test drive... I'm really hoping the bunk ESC was severely limiting performance, and that I didn't waste $300 on a slow ass setup..:031:

In all reality, I only make changes if I expect them to make the truck/car faster... I'm really hoping for this thing to be faster than my Jato 3.3 was.



Also, just reading Castle's website last night, the 7700Kv motor will not do 3s lipo, which was my plan. The 7.2v pack was really just for testing purpose untill I can spend $200 on a phenominal lipo pack...

In all reality, I am aiming for a minimum of 70MPH with the BL setup... I my 3.3 did 110km/h or roughly 65mph being chased down a highway in a car...

If I can't run 3S lipo on the 7700, what other motor can I upgrade to to get me to my minimum of 70mph goal on 3S lipo?

[sleebus.jones]

Yeah, I always try to do my research before I buy, not after. ;)

It's not surprising that you aren't getting the RPM of what you get out of the 1/18th scale stuff. An 8000Kv on 3S will hit 88,000 RPM. The Mamba Max motors are limited at 65,000 RPM, which is in their online information. They also say that the fastest motor isn't the 7700, but the 5600. Also, with a high Kv motor, you need a pack that's up to the task, bare minimum GP3300's. I'm not sure what's in the venom packs.

When you noticed the motor seemed very weak, that was your cue to stop, not to keep driving! I've had hands on 3 Mamba Maxes, and i've never been able to make them die in 30 seconds. Your experience is very atypical.

[BrianG]

Yeah, that's very atypical.

I'm using the 4600 and it is insane! I tried 14 cells a while ago and destroyed the rear tires. On my typical 2s, it is quite strong, but only goes 45-47mph. I've never had it thermal on me either...

Originally Posted by sleebus.jones

Yeah, I always try to do my research before I buy, not after. ;)

It's not surprising that you aren't getting the RPM of what you get out of the 1/18th scale stuff. An 8000Kv on 3S will hit 88,000 RPM. The Mamba Max motors are limited at 65,000 RPM, which is in their online information. They also say that the fastest motor isn't the 7700, but the 5600. Also, with a high Kv motor, you need a pack that's up to the task, bare minimum GP3300's. I'm not sure what's in the venom packs.

When you noticed the motor seemed very weak, that was your cue to stop, not to keep driving! I've had hands on 3 Mamba Maxes, and i've never been able to make them die in 30 seconds. Your experience is very atypical.

After more research, I'm going to buy the 5700kv motor as well... Seems like with more voltage, it's the more logical choice for speed..


Just for the record, the ESC, motor or battery were NOT even warm, so they definatly did no overheat!


I've got a spare ported and polished XTM 457 laying around, maybe that should go in the Jato instead :p

[Serum]

I think your batteries are not up the task.

I would personally take a less high kv motor to do the job.

[glassdoctor]

I think you are overgeared and like Serum said, the batteries are probably a weak link. I'm assuming they are the stick packs....

Try gearing it much lower and see what happens. The 7700 is very fast so if it's only hitting 25-30mph then it's bogged down bad or the batteries are junk.

And if this is the case, then that would also explain the esc suicide...

Originally Posted by glassdoctor

I think you are overgeared and like Serum said, the batteries are probably a weak link. I'm assuming they are the stick packs....

Try gearing it much lower and see what happens. The 7700 is very fast so if it's only hitting 25-30mph then it's bogged down bad or the batteries are junk.

And if this is the case, then that would also explain the esc suicide...

Even with NO load on the motor (just free spinning), it just didn't sound right.. Nowhere near the RPM that my 18th's are getting..... Like, not even half, I'd be surprised if the motor was passing 20k rpm...

By gearing it down, do you mean smaller pinion gear?

well ur batteries are just about the most crappy pack u could have, so get some ib or gp batts and there will be a big difference

and then to reach youre insane speed u will have to use a 3 cell lipo and the 5700kv mm and then u should be good

[BrianG]

@fiero_silva: I think I also posted a response over at the Traxxas forums.

You can gear down by going with a smaller pinion or larger spur. If you divide the tooth count of the spur by the pinion, you get a ratio. Larger ratios are lower geared and lower ratios are geared taller.

According to my calculations, you should be able to reach ~50mph in first gear and 66mph in second with 6 cells, and no tire ballooning. So, something is definitely wrong.

Generally, it is advisable to use a lower KV motor and higher voltage. The current requirement would be less. Some vehicles are difficult to use anything more than 6 cells, but since the Jato is custom, it shouldn't be difficult to use 3s-4s.

And yes, battery quality is a big factor in performance. So, get high quality GP cells or good lipos capable of ~100A continuous for best results.

Will the 5700kv mamba and speed controller take 4s lipo?

Originally Posted by BrianG

According to my calculations, you should be able to reach ~50mph in first gear and 66mph in second with 6 cells, and no tire ballooning. So, something is definitely wrong.

Where are you getting those numbers from? Using the link in your sig, I'm getting 55mph as top speed in 2nd gear with my current setup. I think the only thing that could be different is tire diameter... I don't have my truck in front of me, so I used 3.5".... What are you using?

[BrianG]

4.2" tire. Maybe that's not right...

[coolhandcountry]

It sounds like a definite problem some where. Just finding it is the key.
Is the battery pack still good?

Originally Posted by coolhandcountry

It sounds like a definite problem some where. Just finding it is the key.
Is the battery pack still good?

Battery pack checks out fine with a multimeter. As I said, it was brand new for this setup...

I'm strongly suspecting the ESC was bunk... Even on the 3300mAh battery pack and the gearing I was using, performance should have been far better than it was...

[squeeforever]

I have heard of one other Mamba ESC going out in 30 seconds...It was a member here. Here is a link to his thread about it....