On-road BL project

[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!

[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...

[glassdoctor]

Ozark

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

[Mike.L]

mmmmmmmmmmmm crisp pictures:D:D

[BrianG]

Finished product:

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

[BrianG]

Thanks!

[glassdoctor]

Brian... you work at H.T. by Target?

If it works out, stop by HH with the Jato next wednesday night. I'm usually there by about 6... races at 7:00.

Just ask where the guy with the BL 1/8 is.... :027:

[BrianG]

I work near HobbyTown (about 1/2 mile away).

[Mike.L]

looks nice brian whats the next project!?

[BrianG]

I don't know. I kinda like the Jato because it is easier to handle inside the house for rainy day "bashing". The Revo is great for outside where room is unlimited. I was thinking maybe an RC18, but it might be too small.

I was also thinking of making a "muscle car". It would be another 2WD vehicle meant for drag racing or pulling. Most of it would be custom built with maybe some parts from a current vehicle, like suspension. I figure a STRONG diff would be in order of course. I was toying with the idea of a planetary inline gearbox so the motor would be in front with a driveshaft directly to the rear like a real vehicle, but I don't know if those gearboxes could take the abuse (and they're expensive). That would leave plenty of room on the sides for batteries and would allow me to tune weight distribution by sliding them forward or backwards.

I ran the Jato around a parking lot today and it is quite fast, at least 35-40 mph. It handles VERY well. I had a blast. The rear tires are getting a little worn already, but I finally figured out how to control the throttle to prevent spinouts. I was able to run for about 35 minutes at high speeds, and that was after playing around with it inside work and demo-ing it at my nearby LHS (HobbyTown). SO, I'm happy with the runtime.