On-road BL project

[glassdoctor]

nice.

Can you have the battery laying flat on the chassis... regular style 6 cell pack? The MM should be able to fit next to the motor... it's smaller than I expected.

I got mine at Hobby Haven last week.

[BrianG]

You live in Des Moines too?

The batts might be able to fit flat along the motor mount, but I made the holder for a 2s2p eMoli pack, but happens to fit a hump 6-cell NiMH pack as well. That's why I made the holder walls angled. Even then, the dirt guards on the sides angle up and there are screw lumps where they mount to the chassis and they get in the way. You'd have to raise the battery holder bottom about 9mm to clear the screw lumps and angles. For strength, everything is mounted to the Al bottom, not on the plastic dirt guards.

[BrianG]

Sweet!

I've been visiting the Castle Creations site every couple of days hoping that the "Product is currently back ordered approximately 3 weeks" notice would be gone. Well, I got tired of waiting and checking so I placed an order through them for the 4600 system. I just got an email saying it was shipping today! Yippee! :dft003:

[BrianG]

BTW: What size shaft do the Mamba Max motors use? It looks like 1/8", but I want to be sure before I order a pinion...

[MetalMan]

It's 1/8".

[BrianG]

It's finally done! :027:

I got the 4600 package in the other day and also got a pinion. I have it all hooked up now and I must say I am quite impressed! I haven't done any speed runs but I know it's fast and the torque is crazy. I had to adjust the torque curve to keep from spinning out on startup.

The Mamba Max ESC is tiny and is easy to mount. I had to shorten the motor wires 4" total to keep it neat and tidy. The USB interface and software couldn't be better IMO. Sure beats programming with the Tx only. Cogging is VERY minimal and only at extremely slow speeds under load (trying to go over something). I'd say it's equal or better than the Quark for cogging. The only problem I have is that the ESC gets to about 130 degrees, which is a little too hot for my liking especially since I haven't run it hard yet. I am using the built-in BEC so that makes a difference. To test how much of the heat the BEC causes, I ran the steering servo (85 oz-in Spektrum servo) back and forth continuously without running the main motor and the heatsink gets to about 90 degrees. So, I think I'll get a digital UBEC to keep the heat load off the ESC, especially since I'm thinking of going 3s.

I brought the Jato to work and played around for about 15 minutes, then brought it home and played around in my basement for another 30 minutes on a makeshift "track" consisting of various boxes and other obstacles. The thing literally turns on a dime. I then charged the e-moli 2s2p (6Ah) pack and only put 2.6Ah in it. That's less than half discharged for 3/4 hour of runtime. Not too bad. That equates to an average current draw of about 3.5A. Seems a bit low, but I was also running about 1/2 throttle tops in spurts. I'll be happy to get 40 minutes of parking-lot bashing time or 30 minutes race time, which I think is easily attainable.

The whole Jato is 2166g (4.78lbs), and 400g (~1lb) of that is the batteries. If I go with 2s1p setup, I can get the weight down to 4.3lbs. I'm using 54T/22T gearing for a total reduction of 9.64:1. The weight distribution keeps the front-end down to tame wheelies, so I'm not sure how it will do at jumping. I didn't design it for that, but I'm curious.

Overall, it's a blast to drive. It's lighter to carry around than the Revo, easier to charge, and smaller (easier to drive in smaller areas), so I can see myself playing with the Jato more than the Revo. I may take it to the track at my LHS (HobbyHaven) sometime before I wear the tires down to slicks. :)

[MetalMan]

An ESC temp of 130 isn't bad at all. At that point you shouldn't worry - the thermal protection doesn't even kick in until about 230 deg. My Mamba Max with 5700 motor regularly runs at 150-165 even with no air cooling on 2s Lipo, and the motor has gotten to about 160.

[BrianG]

Wow, I guess I am OK then. I just don't like heat in my electronics - I get upset if my Athlon64 CPU gets above 113 degrees! I'll get a better feel for the real temps when I take it out and really put it through its paces at full speed. When I got the ESC I figured since the battery voltage at 2s wouldn't be high enough to cause the BEC to heat up too much. But that MM heatsink is sooo tiny! Makes my Quark look like a monster!

Even though my 2s2p emoli pack seems to hold up very well, I am a bit concerned about them. When I try to charge them at 6A (1C), I get a "voltage too high" alarm on my Hyperion 7i, even when hooked to the balancer. What I do to counteract this is charge at 6A until the voltage gets to ~8.3, then I lower it to 5A. This makes the voltage go down to ~8.0v. I again wait until the voltage reaches ~8.35 and then lower it to 4A, which reduces the voltage to 8.0v again. I keep doing this until I get down to 3A at which time it will charge properly without the alarm. During this, the LBA10 balancer LEDs flash for each cell at various times meaning the cell voltage is too high or each cell is out of balance. So, what I think happens is that the charger gets to 8.38-8.39v while the balancer is discharging and when the cells become OK, the reduced balancer discharge load causes the charger voltage to increase a little to the alarm stage. That's why my procedure, as tedious as it is, works. It is always right at the point where the charger switches from constant current to constant voltage mode. Is this common for people with emolis?

[Ozark-al]

congrats on your finished project. I would love to see the Jato run at Hobby Haven sometime. If there is anyway to let me know when you might be over there that would be cool.

[Mike.L]

any finished pictues brian?? should be pritty quick!

[glassdoctor]

Ozark

So that makes 3 of us here from Des Moines? You hang out at Haven?

[BrianG]

Ozark: I usually throw the Jato in the car when I go to work "just in case", but I never know when I'll go. It depends on when I get out of work and the weather. HH is not exactly on my way home since I work right near the Target over by the Grimes exit and live on the east side, but I'll try (although today is rainy so it won't be today)...

Mike: Thanks for reminding me! I want to take some before I get it all banged and scratched up. I even got a new dig camera to take nice crisp pictures. :) I'll see if I can post a couple tonight...

[Mike.L]

mmmmmmmmmmmm crisp pictures:D:D

[BrianG]

Finished product:

awesome dude!!! makes me want to convert a jato........