My BL Revo project
 

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:


http://bgosselin.home.mchsi.com/e-revo/e-revo_top.jpg


http://bgosselin.home.mchsi.com/e-revo/e-revo_side.jpg


http://bgosselin.home.mchsi.com/e-re...evo_bottom.jpg


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.

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

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!

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

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

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.

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

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

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

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.


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!

: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

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

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]

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

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!

Cool Mr. "T" is back!:L:

A few more questions:

Question 1
I was looking at the G-Maxx single speed tranny product (http://www.rc-monster.com/proddetail...R-AL-WS&cat=47) and it looks like it removes the rear shell half. Does the removal of four mounting screw points compromise the mounting strength of the tranny itself? I'm concerned that the weight of the BL motor and ESC (mounted to the other "Mickey-Mouse ear") when landing from a jump would be too much for just one half (4 screws) of the normal tranny mounts and break something.


Question 2
Dafni, in a previous post, you said:

Are these the items you mean?

Ofna Spur: http://www.rc-monster.com/proddetail.php?prod=ofn30110
Mod1 gear: http://www.rc-monster.com/gears.php (9th item down)
Strobe adapter: http://www.rc-monster.com/proddetail...od=Slipper-Kit


Question 3
Last question. The BK Warrior 9920 has a built-in BEC. Does anyone know if it is a linear regulator or switching DC-DC type? The heatsink on that controller looks a bit small and linear BEC regulators create too much heat. Using 12 cells, the 6v regulator power dissipation at 3 amps draw would be about 25 watts! That little heatsink on the controller would barely be enough just for the BEC, let alone the ESC if it was a linear regulator. At any rate, I'll probably upgrade the heatsink on the ESC anyway so I won't need a fan. Hepefully it isn't thermal epoxied on.

well i think the heat sinks are fairly easy to remove but i wouldnt recommend it. with a fan it would be fine. also, if your worried about the bec on the controller mike has a ubec in the store for $35. as for the g-maxx single speed conversion, i wouldnt even worry about it. if you are really concerned about it though you can also get the flm cnc'd tranny case. the half is only $40 i think. and yes, those are the items daf ment.

-corey

The only reason to replace the heatsink was to be able to do without a fan altogether. Adding a fan just adds to the wire count, weight, and one more thing to break.

I'm not really worried about the BEC, I was just curious. THe more I think about it, the more I'm sure it has to be a switching. After all, why would a company go through the trouble of making all the PWM circuits, just to use a linear BEC regulator? I was just hoping for a confirmation that's all.

I think I will get the CNC's case - that should appease my worries. :)

When Daf told me what I'd need, I had a bit of trouble deciphering it. I mean, the lingo is probably old hat to the experts, but I'm just starting out with this electric stuff. At least I tried to find the answers on my own, I just didn't want to buy stuff I won't/can't use.

Thanks for the answers...I can go to sleep now. :)

Still awake? :)

Probably it wasn't just the electro lingo, but also my harsh dialect;)

The items you mentioned (slipper) are correct, but for a Feigao motor, you would need the 5mm bore pinions.

The loss of the 4 mounting holes if you go GMaxx single speed is also a concern to me. If you want, you can ask mike if he can get you just the coupler. Then you could keep both halfes, but you would need some kind of spacer for the output shaft.

I don't know exactly about the BEC. Most of us disable it anyway, and use Koolflights UBEC. I would advise you to get one as well.

For the other boys: If Brian is only looking for 25mph-ish, how about a 9XL on 12 cells?? Should give nice runtimes.

25 mph is doible with 9xl on 12 cells gp3300 is about 15 min worth of run time. I don't think the batts was the best though.

This is a great idea IMO.The FLM half case would likely stand up well to the leverage of the bigger motors but i'd like the extra security.

I was wondering whether to make a rear motor holder for XL motor or whether the optional e-maxx motor plate is strong enough.It's 4mm thick.Has anyone ever bent one of these?

Edit;also thought about maybe using the unused side of the motor plate to triangulate it with an alloy brace.

I haven't had any troubles with the 4 screw mounting holes on my truck - I use the g-maxx motor mount, though. I only used 4 screws when I had the full tranny case as well, though. The coupler is available seperately if you want the extra security, as dafni pointed out(I did this as well, when I first got the single speed-I installed it at the track and didn't have my dremel to modify the top shaft so I only installed the coupler with some extra bearings as a spacer into the full tranny case).

Gustav - The 4mm motor plate is most likely plenty strong, but the longer motor could always stand some rear support IMO. Two 3mm screws , each with 3-5 threads are holding the entire motor in some harsh conditions. I have never had a failure in this area, but it always made me think that more support at the rear of the motor would be best.

I am almost positive it is a linear regulator. If it were switching, then you would be able to use it for higher cell counts (BK says 12 cells max with BEC). Also, the regulator is on the underside of the controller, and it doesn't contact a heatsink.

All,

Thanks for the responses.

Looks like I'll be getting the full CNC'd metal tranny case and devising some sort of lightweight spacer where needed.

As for the rear motor mount; I too think a rear motor brace would be nice because the XLs are kinda long. I'm sure I can come up with some sort of bracket. Does anyone know the length measurements of L and XL motors? Judging from diufferent pics, it looks like the XL is about 1/2" to 3/4" longer than the tranny case. I won't be getting the motor for a little while yet, but I can at least start on the bracket.

Judging by what others are running and such, I think I've decided on the 9XL or 8XL motor. Leaning more towards the 9XL just for longer runtimes despite the slower speed.

MetalMan,
I'm not so sure is isn't switching. The fact that there is no heatsink on the regulator circuit almost requires it be switching - there is no way such a small device could dissipate around 54w without a heatsink: worst case device dissipation @20 cells, @ 3amps = (24v - 6v) * 3amps. The heatsink for the entire device would almost be too small just for that! Anyway, I might just use a discrete BEC like Dafni suggested. It would just be nice to have the circuit as simple as possible - I'm only using one servo after all (Hitec HS-5945MB for steering).

I did a little more work this morning:

I added a receiver box which is just a RadioShack project box (item# 270-1801) cut lengthwise because it was too wide. I then glued a new backing. The top is held down with screws, I just didn't feel like putting them in. There should be enough roo for a BEC and maybe an on/off switch.

Also, I made a motor controller mount Dafni-style (once again). It is a bit thin, but seems sturdy enough. I might re-do it using 1/16" aluminum. I even found a spare grommet laying around for that finishing touch. :)

Pics:

http://bgosselin.home.mchsi.com/e-re...rmnt_rxbox.jpg

Looks good! I think the plastic tranny case looks good on your truck.

I look forward to see your motor brace, got something in the works myself. For my new Lehner 1950.

L motors are 60mm and XLs are 74mm long.

I suppose there is no black CNC tranny case? I guess I'll see how solid the plastic one is before I go out and get the CNC one.

I should've asked this last time, but do you happen to know how much each weighs (approximately)? I want to get the truck as balanced weight-wise as possible. I've even added extra mounting holes in the battery tray so I can move them back a bit in case it is too font heavy.

Thanks in advance. Now I can start fabricating a motor bracket!

is that a receiver box on teh right? Howd u get that?

Like I said in the post, I picked up a RadioShack project box (3"x2"x1"), cut it lengthwise on a hand Mitre-box because it was too wide, and shoe-goo'd a piece of plastic to the opening. The cover still comes off. I then mounted it using the servo guard screws. Also, I took my dremel with a sanding wheel and sanded a half moon hole at the bottom rear (where the battery is in the pic above) for the wires to enter.

why is the tranny case empty?

-corey

It's lighter that way. :)

Seriously, I got the halves and motor mount just so I can figure out how to adjust the chassis so it will fit and where the battery trays would go - a template of sorts. I plan on getting the gears later, which is good since I know now what I don't/do need (for the most part).

I assume you are speaking of the motors. L is 278g and XL is 370g.

Don't look yourself blind on that weight. a cool running setup is worth something too.. ;)

Thanks Dafni. Yeah, that's what I meant; the motor weight.
I see you have 7 GP3300 cells in each pack on your version. That must come really close to taking up all the room from the rear a-arms to the servo mounts in the front! I am now planning to make another set of battery trays that are a bit longer to hold 7 cells each, but it will be really tight if I make some type of end tabs to hold the batteries from sliding forwards or backwards!

Serum, I am not overly concerned about the weight itself, more about the balance of weight overall. I found my Nitro Revo to be a bit heavy in the rear left side where the motor is. I've broken two shocks because the truck tends to land on that corner. I'm trying to make it as perfectly balanced as I can.

Is there any advantage of side-by-side cell arrangment vs "tube packs"? The only one I can think of is the ability to use beefier battery bars...

The side/side vs stick thing has just been discussed. Like yesterday or so. Do a search. (sorry, but I'm to lazy right now)

You're right, 7 cells just fit inbetween the arms and servo.

lmao!

well basically it comes down to resistance. the side-by-side soldered right will have a lot lower resistance.

-corey

Thanks. I had already taken Dafni's gentle rebuke and read the thread he was talking about. :o

sorry for the slacky-ness, it was late at night :o

come on dafni! were here to help! and sometimes we must sacrifice a few hours of sleep, maybe school, and maybe food too!

I've been trying to figure out how to design a sturdy rollcage to protect the BL motor, tranny, and ESC and came up with this prototype:

http://bgosselin.home.mchsi.com/e-re...e_rollcage.jpg

It is just sitting on the battery tray mounts right now, but I plan to secure it to the back of the battery trays eventually. However, I don't want to use aluminum because a good hit will bend it (especially since the top is flat). Anyone have any ideas on what type of material to use?

I want something that is light and will be able to take an impact from landing on the lid (without bending) since I'm not a great driver. :)

I was thinking of bringing the design to a metal shop and having it made from spring steel, just not as thick or as wide. I want to make sure the design will work as intended first, so, I'm open to suggestions on how to make it better.