My BL Revo project

[BrianG]

Hello all, I just registered here and thought I'd start off by posting my BL project. I'm coming over from the Traxxas forum (via Dafni's suggestion). Anyway, here's my project:

When I first decided to get my first "real" R/C a while back (almost a year ago), I was torn between the E-Maxx and the Revo. I really wanted electric, but also loved the design of the Revo. Well, I've had plenty of fun with my Nitro Revo, but now have decided to build an electric one this time.

I want to take a minute to thank Dafni for inspiration to tackle this project and have "borrowed" many of his ideas in my design.

I could have bought a rolling chassis off eBay, but thought it would be way more fun to build from scratch. Plus, building from scratch let me get the exact hop-ups I wanted right off. After a few weeks of collecting parts and re-configuring the chassis, here is my semi-final result:











Hop-ups so far:
- Ti GTR checks
- RPM A-arms - originally blue, but dyed black (changed my mind about the color after I bought them).
- Aluminum pushrods.
- P2 rockers.

The chassis was fun. I pretty much cut and grinded off all chassis side pieces except for the steering servo areas. I decided to paint the chassis and battery tray supports black (yeah, I know it will chip off) and am pretty happy with how it looks.

I then used some 1/8" aluminum angle stock (1.5" X 1.5") for the battery trays. I cut the bottom side of the tray to 1" wide to better fit the battery.

The battery tray supports are 1" wide X 1/8" thick aluminum bars I bent using my vise (arg, hard to get a precise bend!). I wanted them thick to take a beating without bending. Yeah, it adds weight, but it's aluminum. I mounted them all using nuts and bolts (using threadlocker) for easy maintenance or replacement.

The battery tray pads are simply craft foam glued with shoe-goo. The batteries are held down with velcro.

Again borrowing from Dafni's design, I will be using an E-Maxx tranny. A little fiddling with the chassis was needed to get it to mount right (not shown in the pics). I'm still not sure if I want to go with a single speed tranny or dual speed. Either way, I'm not really sure what spur/pinion or tranny hopups to get - I guess I'll have to experiment.

Now I'm shopping around for a brushless motor/ESC. I like the price and performance of the Feigao 540 9L motor (2731kV, 68A, 12-16 cells) and Warrior 9920 99A controller. I want a motor and controller that has quite a bit of torque - high top speed is not a real concern. I plan to bash and maybe do some rock crawling, so low speed control and torque with no cogging is what I'm after. I also want something reliable.

It will probably be until after tax-time before I get the motor/ESC, tires/rims (planning on beadlock rims), better batteries, and radio/Rx system, so it will pretty much stay this way for a while. I'll update this as I progress.

[squeeforever]

personally i would go with something like the 7xl or maybe a 6xl if you plan on staying with 12 or 14 cells. the 9l can be run on 12-14 cells and occcasionally 16 but its pushing it.
as for the tranny i would go with the gorillamaxx single speed conversion and a steel idler from mike. that setup is near bulletproof.
also, a word to the wise, i would replace those stock tamiya connectors with deans ultra and put the packs in side-by-side.

-corey

[BrianG]

I plan on sticking to 12 cells, but may eventually move to LiPoly later on when the price drops a bit (and safety issues resolved).

I was looking at the 9L simply because it would be at the low end of the cell count and I'd have a little room to "grow" in case I decide to go higher later on. If I run the 6xl (95A) or 7xl (110A), won't the current be too high for the BK Warrior 9920 rated only for 99A? I don't like pushing electronics to their max ratings for longevity's sake.

As for the maxx tranny, I was toying with the single speed version, but since I'm new to this, was wondering if the top speed would be high enough. The only reason I'd do 2 speed was so I could have a spur/pinion setup that's good for torque and then switch to 2nd for times I want to go faster. If I go single speed, I'd have to find a compromise in gearing between speed and power right?

Yeah, I plan to replace those Tamiya connectors - I was just using those as a visual aid and because they are really used for the EZStart on my Nitro Revo. I plan on getting new batts and definitely using Deans plugs. What do you mean by "side-by-side"? I do plan on running both packs in series (for ~14v total) if that's what you mean.

Thanks, I appreciate the input!

[crazyjr]

Welcome BrianG. Hope you enjoy it here.

I love the stealth look, you need a black body and wheels

The 9920 can handle the 7xl, but the 6xl maybe too much. the 7xl has more power than a 9l with similar speeds with same gearing

[squeeforever]

i am pretty sure the 6xl will be within the 9920s limits. remember the ratings arent always what they say and have many variables. also, with brusless i wouldnt worry about low end torq for crawling. in 2nd gear it would still have PLENTY! my maxx in second gear would pull the wheels when i nailed it at 30mph!
also, when i say side-by-side i mean get rid of the battery tubes and put the side-by-side and use battery bars.

-corey

[BrianG]

Cool, maybe I will look into the 7xl. It's rated for 95 max amps, which is a bit close to the 9920's max rating of 99, even taking into account some variation in max values. But, if you experts say it will work relaibly and not overheat/overload, who am I to disagree? :)

I've read a bit about BL motor parameters in general, so I know that Max_RPM = kV * Total_batt_voltage, but is there a parameter that shows the torque rating? I've seen some motors do list the spec, but most don't. Is there a way to calculate it? For example, take the Feigao chart, there are columns for "Max Amps", "Resistance", "RPM/V", and "IO(A)" - nothing about torque. Also, what is the "IO(A)" rating?

Also, I notice all BL motors have three main wires (sensor wires excluded for those models). I assume this is because the motor coils are in delta configuration?

Sorry if these are noob questions. If you can just bear with me, I promise I'll try to stop asking stupid questions. :)

Crazyjr,

Thanks for the welcome! I like the black look too. Unfortunately, the chassis is simply painted, and will chip off the first time I take it out and beat on it. Someday, I'll have one anodized or powder coated for a better finish. I figure normal "chrome" or "brushed" finished wheels and black tires will still look good. I kept the battery tray the natural aluminum for some contrast. I already have a stock black series Revo body.

[crazyjr]

Yeah, but i'm talking stealth. The brushed would work to.

[Dafni]

Hey Brain, glad you found your way here. Welcome to the RCM board!

Again, thanks for the shout-out. I'm happy if I have been of some inspiration. It's nice to be known for something.

There is no such thing as a stupid question, and feel free to ask whatever you want to know. Every BL related question will find an answer here. This forum is full of knowledge, and we are blessed with very nice members here.

I can tell you from experience, the 9920 can handle the 7XL no problem. I always have fans on my stuff, just in case.

DAF

[nbcaznmaster]

aww! his chassis looks sooo nice and neat! mines ugly and deformed....

[BrianG]

dafni,

Thanks!

I see you're pretty popular around here! I guess if i'm going to choose a design to emulate, it's gotta be from someone popular!

Like I said, I read some FAQ pages on BL motors and understand them for the most part, except for the questions I asked above.

I've read a bit about BL motor parameters in general, so I know that Max_RPM = kV * Total_batt_voltage, but is there a parameter that shows the torque rating? I've seen some motors do list the spec, but most don't. Is there a way to calculate it? For example, take the Feigao chart, there are columns for "Max Amps", "Resistance", "RPM/V", and "IO(A)" - nothing about torque. Also, what is the "IO(A)" rating?

Also, I notice all BL motors have three main wires (sensor wires excluded for those models). I assume this is because the motor coils are in delta configuration?

nbcazmaster,
You should've seen the chassis before the paint! It was all scratched and dinged up from working on it. It's amazing what a little filing/dremeling and paint can hide! ;)


Now for more questions:

- As stated before, I'll be going with an Emaxx tranny. I've heard people talk about making the emaxx tranny one speed. To do this, while being able to take the torque or the BL, this is what I've come up with for parts:
Idler Gear: http://www.rc-monster.com/proddetail...03idler&cat=40
GMaxx Conversion: http://www.rc-monster.com/proddetail...R-AL-WS&cat=10
Would I use stock parts for the other tranny gears?

- What is recommended for a slipper system that is durable and relatively trouble-free?

- If I do stick with a single speed tranny, I want to find a pinion/spur tooth count that will give me lots of power, no more than 25ish MPH, and not cause motor overheating. If this is not attainable, I'll probably stick with a two speed tranny providing I can find the parts to build one strong enough.

Thanks in advance!

[Dafni]

:L: Well, I dunno about popular, but thank you. I guess people remember me for my Revo design, and it's an honour for me to be recognized for something.

We have some other famous peeps here, I can tell you. Serum is the Savage guru, and he did a nice HB Lightning conversion. Batfish has a BL Jato and MGT, and Coolhancountry also has a MGT and is a regular poster here. And of course, RC-Monster Mike, the boss. He can get you everything you need for your RCs, and ships stuff super fast. Like I said, lotsa nice guys, and we know each other quite well. (just don't mind our asian kid LOL)


As for tranny, with the G conversion and the steel idler you're indeed set. The rest can be stock parts. This will give you an almost bulletproof tranny.
First gear is not really needed with BL anyway. And you can loose a servo.

The slipper of choice would be the Strobe adapter with an Ofna spur. (Mod1 gear, nice and strong)

Runtime and temps depend on motor choice and cell count. The most important question here is your budget. If you're looking for a real hi-end BL, there's almost no limit.

As for the 3 wires, Serum once posted a nice animated diagram. Maybe he can link us up.
Basically, there is a winding between all three wires.

Later
DAF

[nbcaznmaster]

What you mean not popular! u and serums are the most poular guys!!lol! Everyone admires u and your rc CARS!!!

[BrianG]

Originally posted by Dafni
:L: Well, I dunno about popular, but thank you. I guess people remember me for my Revo design, and it's an honour for me to be recognized for something.

We have some other famous peeps here, I can tell you. Serum is the Savage guru, and he did a nice HB Lightning conversion. Batfish has a BL Jato and MGT, and Coolhancountry also has a MGT and is a regular poster here. Like I said, lotsa nice guys, and we now each other quite well. (just don't mind our asian kid LOL)

As for tranny, with the G conversion and the steel idler you're indeed set. The rest can be stock parts. This will give you an almost bulletproof tranny.
First gear is not really needed with BL anyway. And you can loose a servo.

The slipper of choice would be the Strobe adapter with an Ofna spur. (Mod1 gear, nice and strong)

Runtime and temps depend on motor choice and cell count. The most important question here is your budget. If you're looking for a real hi-end BL, there's almost no limit.

As for the 3 wires, Serum once posted a nice animated diagram. Maybe he can link us up.
Basically, there is a winding between all three wires.

Later
DAF

Thanks for the info. My budget is not limitless, but I understand that it is cheaper to do it right the first time than to do it cheap and have to do it again.

[offtopic]
A little off topic (and because I want to contribute too!): If there is a coil between each wire junction, that is a delta 3-phase configuration, which is also how a car alternator is wired and how utility AC electricity is transmitted over long distances - except BL motors use PWM DC instead of sine wave AC. However, there is no common reference point in delta. The other 3-phase setup is Y configuration. Basically picture a coil on each "leg" of the Y. The three ends are the "hot" wires and the center junction is the common reference (or "ground") point. Same number of coils though.
[/offtopic]

[Dafni]

I would say, if you wanna stick to 12 cells, a Feigao Nemesis XL (or BK Wanderer XL, same thing basically) would be a nice motor that should last you a long time.
If you want speed over runtime, go 7XL. And if you want more runtime, go for a 8XL.

Those motors, along with a 99amp warrior, have the ability to handle higher cell counts. If you want to upgrade later on. The 7XL runs fine on 12-18 cells they say. For me, 14 is just right, 16 for the occasional rush.

If you a RCM heatsink/motorclamp, those motors are nice and save. Not much worries with heat. I would bet the Novak would get old for you quite quick. Most people do.

DAF

[nbcaznmaster]

Yep! like mine! i had it fo how long? 7 days? i didnt even run it on my revo and i got boreed! got a 9920 with 9L like 2 days ago!