Need help picking BL motor for Emaxx - RC-Monster Forums

sleebus.jones · 11:30 AM

I've seen the insane BL setups out there and decided I have to have one. Not only that, I bought my buddie's Emaxx when he went to the Revo, and it'd be fun to whup oup on him with his old truck! :D

I currently have a stock Emaxx, except for:

1. Steel CVD set coming in the mail
2. I'm running 14 3300 mAh NiMH cells

I'm going to replace the idler gear in the tranny as I understand that's going to be my next failure point. A Robinson slipper will most likely follow after I clean all the teeth off of the spur. :Love:

My goals are:

1. More power (duh!)
2. Longer runtime
3. Speed isn't the main goal :eek: (unbelivable, i know!) I certainly don't want to go any slower than stock, but it would be nice to beat up on my buddy's Revo with his old electric truck!
4. Staying with NiMH. LiPO is awesome but I've already got 4 packs of the NiMH, with another set on the way. I've got the Duratrax Intellipeak twin charger, and I'm really not ready to drop the major $$ that's required to convert to LiPo. Maybe when the prices come down to earth, but not right now.
5. Purpose of the truck is a general use basher, not racing.

I'm pretty much set on the Feigao motors, as they are at a comfortable price point to purchase and/or replace and seem to be a pretty good motor. Right?

So with that said, I'm planning on a 9L and the warrior 9920 controller. Is this going to deliver what I want? If I go to a 8L or 7L, is that going to kill my runtime? Should I be looking at the XL, or is that even worse on the runtime? I'd be real happy being able to acheive Revo speeds, but not at the cost of reducing my runtime of my curent brushed setup. I'm looking to run longer, not shorter.

To be honest, I run my truck out in front of the house, but it gets the most use when I go out camping on the weekends in the state parks. Speed really isn't important there, as I'd just be running over little kids. :L: That's the reason for looking for good runtime -- most of my running about is done at low speeds, I generally don't switch out of first a whole lot. Also, racing isn't that important. Mainly because the off-road monster truck racing scene in Houston seems to be completely non-existant. The few groups that i've uncovered have more freaking drama than LiveJournal, MySpace and a full set of soap operas rolled together. I can do without that mess!

I appreciate any help you folks can give me. I come from the days of the Tamia Super Champ (my first real R/C!) and the RC10. It's amazing to see what these RTR rigs are capable right out of the box....and even more amazing with a few proper tweaks!

Sleebus

Dafni · 12.08.2005, 11:09 AM

Hi and welcome to the forum, sleebus.

I would suggest an XL, then.
If you're main goal is runtime, get a 9XL, and if you want speed, get a 7XL. 8XL for something in the middle.
(assuming you want to stick with 14 cells)

I run a 7XL on 14 cells on my Revo, and I like it alot.

Also, I would suggest the strobe slipper over the robinson. Just a thought.

DAF

sleebus.jones · 12.08.2005, 11:28 AM

Thanks for the welcome. :)

I admit i'm a bit confused on the motor specs, so maybe you can help clear this up....

8L: KV Rating: 3072 Max Amps: 77
8XL: KV Rating: 2084 Max Amps: 83

Looking at this with my ignorant eyes, it seems to me at first glance that the XL is a less efficient motor. I do know the XL is a longer can, which gives you more torque, so I guess I could gear it up and gain speed that way?

Speaking of which....what kind of roll-out should I be aiming for that keeps everything from catching on fire? :eek:

Sleebus

squeeforever · 12.08.2005, 08:52 PM

the 8xl will allow you to gear higher for more speed and will also be in a lower rpm range thus it will give alot longer runtimes and be more efficient because at high rpms it runs less efficient. 8xl all the way. just dont forget about the rc-monster heatsink/clamp

-corey

coolhandcountry · 12.08.2005, 09:00 PM

welcome seelbus. The 8xl will be a better motor than the 8l. You will have less heat problems with the 8xl over the 8l. Can run a lot more cells on it as well. I am not sure on your drive line so you may want to consider this. I can get good run time on a 9xl as well. Check out the website i have started with pics and such of my truck. I have some video of a 9xl.

pcnutz · 12.08.2005, 09:17 PM

hi sleebus I am new to the forum too but not to brushless e-maxx, I would suggest dumping the e-maxx less you have 1500 to drop on it. I have built 4 brushless maxx and there are to manny week points, trans diffs are the hard ones to overcome. steel idlers in your trans does help for a few runs, but if you shim your diffs and pack your trans plum full of axle greese you can get about 10 runs on a good setup. stock up on diffs and trans gears, I use tcrc diffs with kyosho harden steel tcd gear set, and ultramaxx gears in trans, neither are in prodution any more so just to fore warn you. If you want a setup for brushless I suggest the twinforce, it is more suited for brushless and pretty cheap, new they are 210$

squeeforever · 09:51 PM

its not really all that bad. 250 for flm hydrid bulks with 1/8th scale diffs, 25 steel idlers, 50-100 cvds, and 30 or 40 for a good slipper is pretty close to bullet proof.

-corey

pcnutz · 09:58 PM

I still proved to myself the e-trans is junk less you have ultramaxx kit in it, it was bad enough for me 2 buy 2 sets, just don't shift 2 much if you have only steel idles and greese

coolhandcountry · 12.08.2005, 10:15 PM

I never had a problem with my emaxx tranny with stock gears and steel idlers expect for when i ran the light weight in put shaft. They are junk in deed. I have had enough power to push my 14 lb maxx to 60 mph.

sleebus.jones · 12.09.2005, 11:08 AM

Hmmm. Coolhand, after checking out the vids of the 9XL, I think that'll do fine for what I'm looking for. What kind of gearing do you have in there? Hopefully it'll all hang together with steel CVDs, steel idler and a strobe slipper. What do you think?

Pcnutz: I'm not really looking to build some kind of insane torquemonster speedmachine, just looking to boost the performance of the Emaxx, and reap some efficiency rewards in the process. I've gone down the high-horsepower road with full scale and it does get expensive with big increases. However, moderate increases are generally within the design specs of the OEM parts. That's where I'm trying to stay. I'm thinking the 9XL will fill the bill nicely, esp with some new 4200 mAh cells. An 8XL will prolly be pushing the limits of the remaining stock parts.

Sleebus

coolhandcountry · 12.09.2005, 01:16 PM

I think in the videos i was running 16 51 gearing with a strobe slipper. I have the 1/ 8 buggy diffs to. It can handle more no problem. If you run the stock diffs you can run the same with no problems. I had a 20 51 on it at one time.

sleebus.jones · 09:43 AM

Hmmmmm. Assuming you had the stock 5.5" tires on there, that's about a 11% overdrive in 2nd gear, with a theoretical top speed of 36mph. With the 20t pinion, that's a 38% overdrive with a top speed of 45 mph.

Of course I'm also assuming you were running the stock diffs. If you were running buggy diffs with that, i'm not exactly sure how that affects the transmission drive ratio. Maybe someone can chime in on that. I'm assuming a tranny ratio of 4.895 in 2nd.

That's some pretty serious performance. Did you have any heating problems with either of those setups?

Here's another question: Since the low KV rated motors seem to run much better (cooler), wouldn't it possibly be better to go to a maybe a 10XL and gear it up to get the speed, or is there a "sweet spot" that I need to aim for?

Sleebus

coolhandcountry · 12.12.2005, 09:55 AM

From my exiperence. If you really want all that you say. The easy way is more cells. a 9xl on 14 cells verse on 18 cells is a difference. I can get longer run time faster speeds and more power. AS far as the buggy rears yes I do run them. I kept breaking up the stock diff one my set up. The buggy is 3.31 and the stock is 2.87. With the 16 51 gearing with buggy diffs it is geared almost the same as a stock emaxx. as far as heat on the 9xl. I had some heat problems on esc with 20 51 gearing but i had 18 cells on it as well. :D I like to go fast.

sleebus.jones · 12.12.2005, 10:25 AM

Heh, 20 51 and 18 cells and you had some heat problems? :D Gee, I wonder why? ;)

Yeah, I can understand the efficiencies from running higher voltage...you get the same power, with less amps, so everything should work better/cooler. Well, looks like i'll give the stock gearing a shot until it blows up. From my closest guess, it should run almost the same speeds 'cause with 16.8 volts, the 9XL gives you 35,000 RPM. That translates to 32 MPH.

From there I suppose I'll just mess with different gearing and see what kind of heat buildup I get. I wish I had access to some torque curves somewhere...I thought I've seen them someplace, but can't remember where....

Michael