Brushless Rock Crawler
 

I'm thinking about building a brushless powered rock crawler.

I want to use one motor.
2 or 3 cell LiPo.
I have the gearbox and axles figured out.

I need some recomendations on a motor. I see the lehner's go up to 40 turn with a very low kv rating around 700 rpm per volt. I rely don't want to spend that kind of money on a crawler. Does Feigao have an equivilant, or a BK wanderer? I can't find the specs or a list of the availble Feigao's or BK's. Other than what Mike has or carries.

Will these low rpm motors have lots of torque?
Can I get away with a lower rated speed controller?

If you want torque, you need to get a XL size of wanderer (about the same as Feigao), Mike can get them. You can gain lots of torque by gearing the truck a bit taller and use a higher KV rated motor. that XL is made till 625 rpm/v rating, they cost about 100 dollars. they are powerfull for sure.. How long do you want it to drive? gearing it higher, makes you able to drive a bit more precise

What kind of final drive ratio are you going to be running? You may want to consider a higher end motor to like the lehner. It has less cogging than the xl motors. Plus the lower(higher Numerically) you gear the less problems you have with cogging. Just a thought.

Do you think if I went with the wanderer "S" in a lower turn, like 10-15 an geared it for a top speed of 2-3 mph, I wouldn't need the torque of the XL?

I'm hoping that with the ultra low gearing, cogging won't be a problem, although most of the driving in crawling is done with the throttle bearly cracked.

A lower turn motor would be better to give me a broader rpm range to work with.

Where can I find the specs on the wanderers, Mike shows 6-12 turn. What turns do they come in?

The other option I'm keeping open is puting a High/Low range in the tranny. So I can quickly move around and position the truck then shift into granny low to crawl.

What's the least inexpensive controller I can get away with running?

if thats ALL you would do with it them i think the 7020 or the mgm 80 would be fine.

-corey

Here is the RPM information from BK Electronics for the 20 Series motors that Mike will be carrying. It's a screenshot because they don't have normal HTML or text on their site. Mike will probably only be stocking between 4 and 7 different winds, but he'll be able to get you any motor you want from BK.

<img src="http://i20.photobucket.com/albums/b239/1joeyoung/RC-Monster/BK_Wanderer_S20_RPM.jpg" alt="Image hosted by Photobucket.com">

with the gearing you have got in mind, and the speed, you can use the 7020.

Can you get a large spur?

I would go with a 380 motor if I were you and gear extremely low. 500 watts would give you well over 150 pounds of torque at the wheels and have a max speed of 3 mph. The 540 motors would just heat up since there wouldn't be much of a load on them.

Huh, What do you mean by heat up since there wouldnt be much load on them? And if someone wanted they could have put a fan on the motor, wouldnt the 380 sized motor overheat faster though?

Iwould look at maybe a 15L or higher turn. I have run a 14 l on a maxx with no problems. you put 12 cells on it with low gearing heatsink on motor it should be no worries. That would produce more torque and enough power for smooth operation. May look at someting like the lehner xl 1200 as well.

if u want the best setup, it would have to be hv-maxx! I got one if ur itnerested Very smooth accerlatiron. Much bett er then my 9l

a 14xl would kick some butt for a crawler to. have awesom power and run time.

I would not use a 380 motor. the S serie or the hvmaxx is also a good choice.

This is some good advice. The reason being that if a BL motor is undergeared, it will run inefficiently, and will heat up. So, if you have a larger motor, it will require more of a load.

The HV-Maxx on a low cell count (6 cells?) could work very well. Being sensored, you don't have to worry about cogging.

Thanks for the info.

I'll be using a planetary type transmision with stackable sections. If I want lower gears, just add another section of planetaries. It should be easy to gear the final drive to whatever motor I end up going with.

What's the Kv rating on the HVMAXX? and how big is the can compared to the "S" series?

The unloaded kv is 4400, but loaded is closer to 3000. It is 2.84" long x 1.41" diameter. Feigao S series are 1.97" long x 1.41" diameter.

How bout a novak 5800 or a LRP Sphere and Neo?

Both are rated for 7 cells (8.4V) so I could use a 2 cell lipo (7.4V). If geared for a crawl, either one should give me lots of torque, smooth throttle responce, and good run times.

Any other sugestions?

I'd recommend sensored over sensorless for this. Any of the Novak or LRP systems would work, but bear in mind they have a pretty high kv so would need to be geared accordingly. The GTB can safely be ran on 2s lipo as well I've read. The GTB with the 8.5 motor would be a good combo for your project in my opinion.

i would personally go with the hv-maxx as it will provide more torque than the gtbs.

From my experences. you can run a brushless motor under geared if you run a low cell count and a high turn motor. This in turn keeps the rpm down and the heat factor. The sensored is a good option. May look at the aevox motors for that or novak. Keep in mind of what shaft you will need as well for pinion selection. good luck on project.

I don't know that you could get it geared down enough without going to a airplane reduction like a GD600 or something, it might have a lot of torque, but you just don't need the rpm. For right now, brushed is FINE for crawling, in fact, I'd say it's even better. The main motor that most guys run is the Integy 55x1 comm lathe motor (slow, but tons of torque), and for $20 a motor, why wouldn't you go with it. The brush wear is non existant, and they take beating after beating on Clod gearboxes that slam against the rocks.

Oh yeah, one other thing. Anyone ever see the vids from the ORCRC (Oregon Radio Controlled Rock Crawlers) gang? One thing they're always doing is playing in or around water on darn near every course. The trucks are repeatedly rolled into puddles, driven through mini ponds to get to the next obstacle, and generally beaten senseless. I would keep my $200+ bl systems as far away from a crawler as possible, and I'm just fine with running a Super Rooster and dual 55t lathe motors.

If you haven't already, check out www.rccrawler.com for any other info on both this topic (johnrobholmes had a bl crawler) or any other random crawler question.

I know the integy 55 turn lathe motor is a commonly used crawler motor. I was just wanting to do something different. I like brushless for the low maintinance. I have a SS5800 I could steal out of my XXX-4 G+, won't be racing that till spring. And It's kinda been shelved since I got my X-5.

I've been to rccrawler, I like the vids people post in the forums. As far as running in water, my truck will never see that. I can't abuse my stuff like that. Some of those video's on there they drive completly uderwater for a short time. Looks cool util you have to replace all your electronics cuz your waterproofing job wasn't as good as you thought it was, LOL.

Most of the crawler out there are clodbuster axle based. I want to build a shafty. One motor with at gearbox and front and rear drivshafts to a solid axle setup.

I'm gonna need a 1/8" shaft for the pinion I'll have to use. So it looks like I'll be going with the novak setup, the 5800 or maybe the 4300. It would require less gear reduction in the trasmission to get the crawl speeds I'm looking for.

Thanks for all the help, I'm a long way from where I started, wanting to use a 40t bl thinking it would be comparable in torque and rpm to a 55t integy lathe motor.

I never really followed what he did, but check out johnrobholmes bl crawler project that he did, I think he used a airplane motor.

I had a SS5800 in my Pede for a while, then bumped it to my RS4MT, it was pretty "meh" once I got my Lehner 5300. :D

We all use airplane motors :L:. Some are just more car-suited than others :p.

or are it all boat motors, more car-suited...? :p

or...we could stop using "OR"s to begin the statements! lol

what I mean is that he used a smaller 380 or something close to it, maybe an outrunner.......but I got no idea.

Well, I got my planetaries yesterday.

They are a little lower than I thought and have a good sized jump when going from 2 stage to 3 stage. They have a reduction of 4.5 each.

2 stage would give me a tranny ratio of 20.25:1
3 stage would give me a tranny ratio of 91.125:1

So 3 stage planetary with a diff ratio of 3.3:1 would equal a crawl ratio of 300.71:1 :eek:

But with a hight Kv motor like the NEO at 6500 rpm/V on a 2cell LiPo with LST tires would give me a top speed of 3.30 MPH. Thats about what I'm shooting for 3-5 MPH. I might have to put a 1:2 gearset in the tranny to have a HI/LO setup so I can move around and positon a little faster and shift into LO to crawl. High gear would be 6.6mph and low would be 3.3mph.

Thats a cool idea. where did you get the planetaries

Could you take a pic of this planteries.

Yea, I'll post some pics tonight when I get off work, got to get some sleep now, got off work at midnight and it's now 6 AM :L:

3mph might be too slow, not enough wheelspin makes you rely on your tires getting a perfect hold. Not saying it's not good for your application or is bad, but my Clod with dual Integy 55t motors and 9t pinions hits maybe 6mph, and it just barely has the wheelspin to get up stuff. Granted, it's still hard for it to get stuck, but if I were you, I'd go with the "high" range.

Stayed late after work tonight and got my axles designed and drawn up. Gonna start cutting aluminum tomorow night.

Here is a pic of the planetary

http://webpages.charter.net/emagill/planetary.jpg

Looks a bit big and beefy, might wind up being heavy, but I think that'd be better for durability instead of light and weak.

The outside of the case is about the same size as a 540 motor can. It's gonna be a whole lot smaller than an emaxx or other transmision. I'm gonna put two gears the same size out the end of it so I can have the driveshaft run parallel right under the motor and planetary to the front and rear driveshafts.