Noobie to Brushless, need little help/advice!
 

hey guys,
i have a E-Maxx that has seen A TON of abuse and has some good mods to it. i just wasnt with the power i was getting with te stock motors so i turned to brushless. im over on rccrawler and savage-central a lot. i posted a thread on rccrawler and they got me started. they told me to go with the castle creations speed control(as i can see is very popular on here) and they told me to run a feiago motor. i started looking around and i noticed that there are a ton of feiago 540 size motors. so this is were i need you help. what motor do i go with?

i mainly race with my club(just short track J style or similar) and some bashing. when i get my motor i expect to do a lot more bashing. so basicaly a all around set up. and what is a rough estimate on gearing that i should run? thanks in advance!!!!!

Welcome to the forum Mudrunner!

Here is an interesting read, i think it will answer most of your questions.

http://www.rc-monster.com/forum/showthread.php?t=5115

If any question remains unanswered; Feel free to ask!

o man, long read. ill get back to ya in a bit!

i read that. i didnt have very many questions to start with besides a sugested motor. i read through the whole page and then did the sugested motor chart thing. when i entered everything it didnt give me a certin motor. all it said was that my motor may over heat. so what motor should i go with?

I assume you were using the "motor selector"? If it came up with the overheating warning, your required RPM based on the values you entered must have been over 40,000. And the reason why it came up with no motors is because there were no matches (kv wise) based on the weight of the vehicle and the required kv to reach your desired speed.

What values were you entering? (Hint: use the "Export Values" button on the webpage, highlight the data, and paste it here in a post).

this is wat i came up with,
Vehicle Weight (approx): 15
Desired top speed in MPH: 50
Differential Ratio: 2.8461538461538463
Transmission Ratio: 2.769230769230769
Additional Ratio: 1
Spur Tooth Count: 64
Pinion Tooth Count: 20
Battery Voltage: 7.2
Tire Diameter (inches): 5.75
Total Ratio: 25.2213 : 1
Tire Circumference: 18.064 inches (458.83 mm)
Required Motor RPM: 73719.725 RPM
Required Motor KV: 10238.851 RPM/V
Good Motor Choices: No motors of this class fit the parameters you entered.
Better Motor Choices: No motors of this class fit the parameters you entered.
Best Motor Choices: No motors of this class fit the parameters you entered.



this is a rough guess. being that i dont now the weight of the vechile, top speed, what transmission gear(1st or 2nd), Spur and Pinion tooth and what tire size ill be running.

I see a couple of problems there.
- Your voltage is too low at 7.2v. You should enter 14.4 for 2x6cells packs, or 16.8 for 2x7cell packs. Because the voltage is so low, the motor kv has to be extremely high to compensate.
- You want a 15lb truck to go 50mph! Wow. While possible, you're gonna need some serious power.
- It looks like you chose 1st gear as the tranny ratio. You're gonna be hard-pressed to get 50mph in first gear. Imagine what 2nd gear would do!

Most people lock their trannys in second gear - BL has so much power that first gear is useless unless you want to go very slow a lot.

I entered some more reasonable values and came up with this:

Vehicle Weight (approx): 15
Desired top speed in MPH: 45
Differential Ratio: 2.8461538461538462
Transmission Ratio: 1.7222222222222223
Additional Ratio: 1
Spur Tooth Count: 64
Pinion Tooth Count: 22
Battery Voltage: 16.8
Tire Diameter (inches): 5.75
Total Ratio: 14.25952 : 1
Tire Circumference: 18.064 inches (458.83 mm)
Required Motor RPM: 37511.425 RPM
Required Motor KV: 2232.823 RPM/V
Good Motor Choices: BK Wanderer 7 XL (kv=2145)
Better Motor Choices: No motors of this class fit the parameters you entered.
Best Motor Choices: Neu 1515 1y (kv=2200) LMT 1940/7 (kv=2239) LMT 1950/6 (kv=2178)

ok, so that sounds better. i didnt think about have 2 packs. i only thought what one pack was, oppps!! i had no idea how much my truck weighs. its basically a bone stock e-maxx. i have pro-line power stroke shock, titanium turnbuckles, mip cvds on all four corners(not centers) and its got Maximizer diff in the rear(soon to be in front also). do you have a link to any of thoughs motors? preferably a site that takes paypal echeck or ebay? thanks for the help!!!

If your run 5S lipo, it will be much easier to acheive the 50mph.

i cant run lipos. 1. i dont have the charger for them and 2. the club leader said we cant run them, hes seen wat they can do.

Hmmm.... How about this site!:018:

http://www.rc-monster.com/proddetail...540C_XL&cat=20

People are paranoid about lipos cuz of the old horror stories. I agree they should be treated with respect, but as long as you pay attention to what your doing and use common sense you wont have nay issues.

IMO most of the lipo scare stories came from a couple years back when people had no clue what they were doing. CHargers are better now and so is the knowledge of lipo.

If Lipo is still out, check into the A123 Li-Ion cells. Safe and high power.

Remember... A brushless setup is only as good as the power you supply it.

to start off with, whats the difference between the 7XL, 8XL and the 9XL?

and our club has sent out trucks 60ft in the air, YES 60ft! on average they see about 20-30 so the shock of the landings my cause a big boom:004:

I agree with jhautz about the lipo thing somewhat. I have some now and am still paranoid about them, but I do think that the technology and understanding has advanced quite a bit since the horror stories. Some people have even tried to blow some by deliberate mischarging/running them over (yes, you CHC :)) and they puffed, but that's it. But, no matter what, the owner of the track sets the rules so that's that.

I would shoot for a 40mph top speed at the most, especially for track use. Consider a stock emaxx goes about 25mph IIRC, doubling the speed to 50 would just be insane, especially in a monster truck. And I don't even want to think about the damage from a crash at that speed! :) Anyway, 35-40mph would be much more attainable using regular cells, and you'll get better runtime since you won't need such a powerful system.

And the motors in the "motor selector" are all available here. :)

The number is the number of turns of wire in the motor. More turns means the motor spins less rpms per volt. Less turns means a faster motor. The XL part refers to the length of the motor. And you do want an XL for a larger truck like a Maxx. You pick the motor turns by the amount of battery voltage you plan to use while keeping the max total RPMs to about 35k.

OK... I wouldnt send my lipos 60 ft in the air either. That falls in the ''use common sense'' clause.:005: A123 cells are still very viable for you though. Just as durable and safe as the old NiMH cells, but capable of putting out much more current.



As an addition to brians last post:

Generally a motor with more winds will generate more torque with less rpm on the same voltage. Also with the same load (ie. gearing) it will draw less current which translates into a cooler running system and longer run times but lower top speeds.

im currently running 2 6 cell packs, GP 3300's at an average of 1.179 AV. so what would suit my need?

1.179 Av?

thats wat it says on the battery. when i bought them the hobby shop guy said the higher the number the better punch ill get. so i dont now wat exactly that means.

Oh, ok, I see now. Probably the voltage it maintains under a specific load (probably 30A).

I'd just get an 7XL or 8XL then. The 7xl will be faster but will have less runtime. The 8xl will be a little slower but will increase runtime. I was using an 8XL with 12 cells in a Revo conversion and it was quite fast - not 50mph though. If speed is your thing, then get the 7XL.

**Whistles Innocently** I'm aiming for 50mph in my G2R lol...but then again I've had my G2R up to 40 and it felt so planted 50 will be fine.

But I have to agree crashes at those speeds aren't pretty.

lol. I never said there wasn't a crazy fool or two who wouldn't try it. ;)

What do you plan to do to get it there? I hope those new Revo diffs come out soon for your sake! :)

Stock Revo diffs are amazingly strong my friend :)

Not only that, but I'm surprisingly easy on drivetrains...Never stripped a spur in my life! My T-Maxx spur has 6 gallons+ on it. *knock on wood*

1950/6 Hi-Amp on my current Lipos (2x 2S2P 8K's Maxamps) with whatever ESC. I think I'll just try a MM...should be fine. Someone is running 4S on a 1950/7 without a problem, and a bunch of people run 5S with 7XL's and 8XL's, which probably draws more amps, so I should be fine. Plus, 4S is techincally within spec of the MM ESC.

Stock revo diffs are poop.

Remember you are running a tiny setup on yours.

If you build them in aluminum (the diffs) with proper shimming they can last a while, but they are not considered amazingly strong. Mike mentioned that racers replace the diffs after the race with new ones, just in case.. Meaning they don't put a lot of faith in them.

Well, take this form someone who has ran stock diffs on all of his trucks. I'm lucky with drivetrains...and I'm going to stick to that until the 1950 proves me wrong (not doubting that it will).

Plus, I don't know that they are "poop." They are not a strong as 1/8 diffs, yes, but they make T-Maxx diffs look like they were pulled from a radio shack car.

We'll see what happens. I'll report my experiences :) Upgrading from an HV to a 1950 is a big deal for me :D

you are using plastic cups/housings?

Maybe....:032: lol

Yea, I am...I have a feeling those will be the first to go.

I think I'll end up getting RR Ring and Pinion and some Aluminum Cup and Housings and shim it (if I ever blow the stock diffs - again, still operating under my little lala-land dream here). I think that'd be pretty strong, no?

Just how powerful is a 1950? Any analogies that I can compare this to?

MetalMan is running a 7XL on 5S A123 in his Revo and he has never had a diff problem and he's running stock diffs, but then agian he has a slipperential in his (his own slipperential).

Come on Rene, don't sugarcoat it; tell us how you really feel! ;)

I've never blown a Revo diff yet, but I do have my start power set to low. They are weak though; only two satellite gears in a plastic cup. I know I'll be one of the first to pick up one of those upgrades Revo diffs that Mike is working on...

Lol Brian..

I guess i can put more effort in choosing more uncolored and decorating words to describe how i feel about these 1/10th diffs..

lol. No, I think your words are just fine. You very clearly expressed your opinion about those diffs with no room for confusion due to misinterpretation. :)

how speed and run time difference are we talking? i have a feeling ill get the 8xl to keep run times up. i also read that the A123 Lipos are that great. Xtremerc cars tested them and they said yes they are strong but dont match the power of regular lipos. can you guys fill me in on these? and if i remember right, they some with a charger too?!?! maybe a link?!

The A123 cells are rather neat. They are not as fragile as lipo's. Thoug they drop in voltage pretty bad under a high load, which makes them less powerfull than enerland lipo's

BTW, their name is not lipo, it's lithium ion.

Plug the values of your setup into the speed calculator thingy to get an idea about the speed difference.

Runtime is highly variable - driving style, temps, terrain, weight, etc all play a role in runtime and is impossible to calculate accurately.

sorry, im not real up todate on my terms:dft012: maybe ill just stick with my GP's

I am using the GP's also.. they are great for everyday bashing/driving.

ok, cool. then ill just stick with them and get me a motor and ill be good!

Save your money on the RR ring and pinion and just get a good alumunim cup and housing. The RR ring and pinion doesnt last any better than the traxxas hard gears, and the traxxas gears are half the cost.