Going Brushless, What are my options

[miata_speed85]

I'm looking to go Brushless as stated for a Tamiya M04, what are my best options in a reasonable price range for an ESC. I was thinking the Venelion combo, but I WANNA GO FAST:cool:... REALLY FAST. Help please.

[Mister-T]

Mamba max 5700 with 3S lipo could do the job

[miata_speed85]

So i just bought a Sidewinder ESC and temporarily a speed gem pyrite 10T double brushed motor. What is the best option with a 7.2 V 6 cell in terms of power output to longevity when it comes to brushless

[rccardude04]

Not sure why you'd buy a sidewinder ESC and then a brushed motor for it. The whole combo with motor is under 150 bucks. That combo must have been at least 100.
-Eric

[Bnoland]

Isn't the M04 a RWD car? That should be interesting brushless depending on the motor you go with.

[miata_speed85]

Well i just couldn't see myself going brushless yet... i'm rather new to r/c and i fired one motor already so i learned about gearing. And now i want to step up speed, my bandit is getting pretty boring around 35-40 with a speed gem 12T double geared 23/86 it's just on the edge of being to hot but it's still within safe range. And with my road car i'm just interested in hauling a$$. So for now i can safely control my speed. I promise with a brushless i'd just max gear it and hit a wall or flip it, and have to rebuild. But a brushless is an option in the next couple of months. Plus there's always the fact that I'm deployed right now, and If i buy brushless i'm goin to kick myself if i don't blow it out enough and fry it out. Not sure if' you're aware, but the sand in the middle east is highly metallic, and anything that has to do with electronics gets angry... quick. But I do see myself breaking down soon, i'm already looking. So if i were to go really fast what is the fastest motor/ approx gearing ratio that the sidewinder can handle?

[miata_speed85]

And yes it is rear wheel drive, Did i mention that I'm an avid drifter as well, so all that nice Brushless tourqe should make things interesting. I'll let you know how it goes though. Thanks for the help.

[rccardude04]

If you gear the brushless properly, it won't be any faster than what you have now. Also, the castle motors are fairly well sealed so you have less of a risk of frying it than a brushed motor. I understand the fear, but I think you'd have better luck with a brushless system.
Not to mention the general lack of maintenance. :) That's always nice.
And yeah, drifting with brushless should be a very enjoyable experience.
I need to get a touring car. :( lol
-Eric

[Bnoland]

If you gear the brushless properly, it won't be any faster than what you have now. Also, the castle motors are fairly well sealed so you have less of a risk of frying it than a brushed motor. I understand the fear, but I think you'd have better luck with a brushless system.
Not to mention the general lack of maintenance. :) That's always nice.
And yeah, drifting with brushless should be a very enjoyable experience.
I need to get a touring car. :( lol
-Eric


Agreed.. generally the brushless motor is less to keep up than a brushed.

[GSMnow]

I would get the Castle CM36 4600 or 5700 motor. I ran a 5700 on a Mamba Max in my Losi XXX-T and it's now in my XXX-4. Same motor, over a year of hard racing on it. Still runs great. Use a little RTV around the wires, and lock tite the 6 tiny screws, and you can forget about the motor. At most a drop of oil on the bearings when you are bored and have nothing to do.

In a touring car, on NiXx cells, or 2S, you may want the 5700 for the rpm, but if you can manage a 3S LiPo later, the 4600 will be the extreme screamer. Even on 2S or NiXx it will make a ton of torque, but you might have to gear it pretty high. Figure what motor rpm you need to go 40-45 mph and see if the gearng will work out. On 2S the 4600 will hit about 33,000 rpm. On 3S it is close to 50,000. The 5700 on 2S runs just over 40,000.

[miata_speed85]

I just bought a C4 big stick, i'm not sure of the quality, but it's a product by Dynamite, so it should fair well. I just got my Tamiya M04 assembled and running with a 12t double speed gem. and the drifting is outstanding. I started out without the foam in the tires, and it just spun around, after i put the hard foam in the control during a slide is outstanding. I absolutly love it, now i just can't wait to get my brushless in. i also noticed that I will need to turn the 3 holes into a slot so my gearing options are better. does anyone have a good gearing option that works for a 5700 Kv brushless. I'm looking forward to fast runs when the motor gets in. Thank you for all your input so far and any further input that you may have.

-Adam

[ElectricThunder]

Whatever will get you at around an 7.5:1 FDR is probably a nice start (will be powerful and fast probably in a 2wd car though!). I run close to a 7.5:1 FDR in a TT-01 (4wd and not 2wd, so more motor stress and load) and it's QUICK. Probably tops out at around 40 on 2s lipo too, but this is running a Novak 5800. I have used my 5700 motor in it before though, at the same exact gearing, and WHOA. It was a beasty little car. Probably about the same top end, maybe a touch faster, but way too much torque. Probably could use a larger pinion. I'd need a smaller spur to take advantage of taller gearing though.

[miata_speed85]

sounds good. the only thing i don't like about the m04 is the lack of gearing options, specifically the spur gear, I haven't even seen anything above stock. and metal gear options, forget about it, i looked for days, but i was talking to Eric (rccardude04) and he said his M03 has no problems with plastic. so i figured what the hell, ordered 3 sets just in case, it will be interesting whenever the motor gets here, but the one thing about being deployed is the mail service takes FOREVER, and my patience is certainly starting to wear thin. Well thanks for the help, I'll let you know how it turns out. How well do the brushless motors do on high gearing in terms of heat problems. I know that my 12 turn doesn't really enjoy running about a 19 pinion, stock spur, but i hit it on 23 to push it, lets just say it hauls a fair amount of ass, and it doesn't get to angry as long as i don't stop and go alot. so circuit racing or continuous drifting is fine. and if i do have to stop it's all about the gradual start.

[ElectricThunder]

The tamiya plastic drivetrains are MONSTROUS! My tt-01 has a stock drivetrain, and I do some nasty nasty things to it. No breakage yet. Just make sure you use some of that anti-wear grease the comes with the kit to keep the gears running smoothly, and you should have zero problems.

The teeth on the diff gears in my TT-01 are friggin' HYOOOGE. I don't think I've broken a single part on that car yet, and I've hit mail box poles too flying through the air after hitting a street reflector.

And for brushless stuff, they tend to do cope better with higher gearing. They have a wider range in general for gearing since they produce so much torque and power more efficiently. You can still overgear and overheat them though, so it is wise to take some caution in gearing. You don't want the motor to exceed 200F; once it does that, the rotor will demag, and then it will be a vicious cycle of overheating and more demagging.

I agree with the gearing options too... I get a little annoyed when I only have 4 diferent ratios I can run...hmph. Got it running like a champ though, so it's not all bad. I want a faster motor though....haha!

[miata_speed85]

You can never be hapy with what you got, the only thing i don't like about the M04 is that there is no light kit for it, so i'm goin to have to find something for it. like i said though i'm going to take the 6 holes that are in it and connect them into an arc so it makes more ratios possible. What do you think about that, match the hole size and put washers in since the screws aren't really all that great, it will take some time though. actually now that i think of it will it jepordize the integrity of the gear box with the screws free instead of going down the individual screw shafts? Well i'll prob start at about 17 and go up from there, or down... probably up though. YOU CAN NEVER GO FAST ENOUGH, until the car rattles apart or flips when you try to turn.

[ElectricThunder]

I'm not sure how the M04 gearbox/motor plate is designed, but if you think structural integrity may be sacrificed, don't do that...lol. My TT-01 has the metal motor mount, so it's a bit tough to dremel the holes out, but I may do it with the stock plastic one that's laying around since it really doesn't have a whole lot of stuff to do with the chassis, but it may weaken the acutal motor mount (the plastic version at least).

[miata_speed85]

Well that's not very good... i'm not really all that fond of the way that's designed. my Bandit has the right idea. put the pinion through the hole and have one solid mount and the other on an arc. the screws are about 3/8" long and it can be geared up to about a 38/39 max... although i don't know any motor that can handle that... at least any motor that i have.

[ElectricThunder]

The kv option below what motor kv I have now of the medusa V2 brushless motor can probably handle that if I use some nice foamies on my Rustler, or if I convert it to a smaller and ligther bandit (I already run 27/87 on my Rustler with Road Rage tires, and 21/87 with Mashers without the motor getting above about 130-135F).:D I know what kind of mount design you speak of though, and I agree. The Tamiyas are aimed more at beginners though I think, and so they figure making the adjustable but not really THAT adjustable mount is a good way to keep newbs from stripping gears, which they do have a good idea there. But for guys like us who want more gearing options, it stinks (I admit, I love my TT-01, but I knew the gearing was fixed, so I probably should have bought a TC3 or something if I wanted a whole plethora of gear ranges).

Meh, I'll pop in a faster motor...lol.

[miata_speed85]

Faster motors are always an option. the one that i have is set for a gearing option with 3 holes on top and 3 on bottom. labeled 17, 19,and 20 if you know what you're doing though you can make it a little more broad by changing the holes that you use. i'm was running a 23 tooth until i had the unfortunate event with the concrete barrier. i guess a 12T with a 23 tooth at top speed gets the axle mad with full-focused impact. Granted that the car is dead, it was fun to watch. My pocket will start hurting soon. especially if i keep upgrading while I'm trying to fix. I think i'm at a stand-still for now. I've almost reached my limit. I had some issues with my Bandit too when i went to the 2.8 All-stars wrapped with foam-filled talons. the extra weight didn't get along to well with the stock titan motor and a 23/76 gear set. s#*t was melting, the label even peeled off form the heat. but like i said it was fun to go fast, besides stock sucks.

[ElectricThunder]

I'll second that: stock does suck! I have WAY too much money into both my TT-01 and Rustler...:rolleyes: They're both fast though, and haven't broken anything in about 6 months.:D RPM for the win!

[miata_speed85]

That's the only problem. Getting it to go fast is easy... Getting it not to break from the power and speed is where ther trouble comes in. I learned that with the Bandit. I've dumped plenty into it, now i'm just trying to figure out which would be more fun brushless, I'm leaning toward to M as of now, but i may change my mind. The only thing i don't like about the sidewinder though is that there are no mounts for it, and you only get one shot with the sticky tape... HELLO ZIP TIES!!! My M isn't a money pit yet, I learned the hard way, and pretty much gave my bandit to my room mate anyways.

[GSMnow]

The Parma clear mounting tape it great. Each piece of tape is only single use, but if you do need to move something, it peels off clean and leaves nothing behind. I use it on all my electronics now. I have moved my Mamba Max 3 times.

[ElectricThunder]

I use BRP double sided tape (got a little roll of it for cheap; works well). If I find them in my tool box, I prefer to use that clear gel stuff that Novak includes with their ESCs now though. That stuff is great.

[GSMnow]

The Parma tape is the clear gel type also.

[ElectricThunder]

Does it come in little squares or on a roll? I need more double sided stuff, so if I can get the parma stuff on a roll, that'd be great. If not, I'll just buy some squares then I suppose.

[miata_speed85]

All the stuff you speak of is readily available at you lhs? b/c my lhs is about 8000 miles from where I'm at now... LOL

[GSMnow]

Yes, I bought it on a roll at my LHS. It costs a little more than the black stuff, but well worth it if you ever move gear around like I do. I hated cleaning off the remains of tape the strong black stuff left. The clear Parma tape holds very tight, but when you roll it off, it leaves a clean chassis and ESC. Here is the link
http://www.shopatron.com/product/part_number=8044/137.0

[ElectricThunder]

Miata- I got the BRP stuff from my LHS, but the stuff GSM speaks of is far better, and can probably be had at your LHS if they carry Parma products. If not, you can probably source it, like from the link GSM provided.

[miata_speed85]

Sweet thanks... I'll get some and in a week it'll get here and i'll be off again. not i'm trying to figure out how to balance my chassis, since the battery in the m-chassis sits in the back, with the motor, gearbox, and any other components back there it really needs to get some weight up front. i'm thinking of ways to re-mount the battery somewhere, or move any other components that can be to the front... maybe even add some weight up front. I'll figure something out.

[miata_speed85]

So i'm still waitin on my big stick to get in, mean-while i'm disassembling my bandit to change out the rest of the parts with metal ones that i have. does anyone know where i could find metal half-shafts? it's the only part that i can't find for it. everything else... axle carriers, bellcranks, stub-axles... is now aluminum. i had to re-enforce everything after i was doin some serious bashing, so i think i'm ready for speed now. just waiting on the motor. I HATE THE MILITARY POSTAL SYSTEM!!!

[ElectricThunder]

Never seen metal half shafts for the bandit. For my Rustler, I just did a steel dogbone upgrade (I hated the CVDs that I got for it). Haven't broken or twisted a universal since switching to the CVDs/Steel dogbones though.:D

I would leave the halfshafts as plastic and just buy a 6 pack of 'em. It's best to have an easy to replace weak link. I'd rather replace dogbones than idler gears or spider gears. Or you can try the dogbone upgrade; not sure what length bone you'll need though, as the Rustler has longer suspension arms than the bandit.

[miata_speed85]

well back to brushless. Got my motor in today... I'm impressed. running 23/90. I'm thinking about switching the spur back to the 76/ It hauls a$$ though. I had to put it in my bandit as my M04 is still dead. The only down side is that i'm still waiting on my battery tabs to come in for the ESC so i'm running straight wire into a molex... which takes bumps out of the equation since it just pops the connection. in about a day it should be here, I'll weld it up and not have to deal with the "turbo lag" any more. it really doesn't like the power draw of going from reverse to forward, or goingto full throttle. gotta kinda ease it on. I'll keep you posted, Right now i'm probably running around 50-55 right now, hoping to reach 70 soon.

[ElectricThunder]

70 is definitely attainable in a bandit. The M04 is probably going to be nuts.:D

I finally got my replacement motor for my Trinity NOW, and I forgot how fast and fun it is. Handles well too.

[miata_speed85]

the M should be interesting with the low grip road over here, I'm going to buy a mamba max for my traxxas so i can go faster in that, and then move my current set-up over to the M. So is there a motor limit on the mamba? If not I'm thinking bigger is better... it's so ghetto right now though. I have zip-ties holding a flashlight standing up in the back so i can see it at night (the only time i really get to run) But it's fun. I"l going to change to a 31/76 gearing tonight, if nothing else then for about 5 mins just to see how fast it goes, I'm not seeing it being healthy, but it won't hurt for a minute or two... just to see. I just have to resist temptation to run the battery out. The only problem with that is the slot for the motor mount doesn't swing far enough to handle the 31... which is why i have to step down to the 76 tooth spur again. FUN TIME

[ElectricThunder]

The mamba max is 100 amps continuous, and a crap ton surge. You can probably run a 3.5 turn sensored motor on the mamba max and it'd probably be fine. Considering the mamba motors are capable of about 700 watts of power quite easily, the mamba can handle most anything that is 540 size and an S size can probably.

It's a tough little controller, and people use the thing in 1/8 conversions on 4s lipo, so I'd say it can handle pretty much whatever you can think of.:D

31/76 is probably going to make things hot; especially if you run it during the day. If it's for a speed run though, it'll probably hold up fine. Just monitor your temperatures and make sure the motor does not exceed 180F (200 is the max limit, but I find that if you can get it to 180, you can probably get it to 200 in just a few more minutes).

[miata_speed85]

like i said. i just want to rip it down the road, shut it down and gear it back. It's funny b/c i don't realize how fast i'm going until it wizzes past me... what is the 5700 in terms of turns? i'm looking to go to the 7?00 kv motor with the max... should be fun. what's a reasonable price for a lipo battery/ charger? I've dumped enough money on the cars already... i'm just worried about it fitting in the slots for the batteries.

[ElectricThunder]

I have no idea how many turns any of the mamba motors are. That's something that has eluded my knowledge....:(

With lipos, expect to pay about 100 bucks for a good 2s pack (neu energy 5000mah 20C packs are about 100 bucks off of RC monster for example). As for a charger, it depends on what route you go. For a decent one, expect to pay about another 100 bucks plus a balancer (whether that be the astroflight blinky, which I have, or something you can wire in so that the pack balances as it charges). You can get balance chargers for about 140 bucks with the balancer built into the charger though IIRC.

[miata_speed85]

so the lipo packs are just a more steady voltage flow. I keep seeing people saying the lipo is the way to go, but everything i see, they have the same specs as NiMH batts. Doesn't really seem to cost effective. If i go to the mamba though, i'm looking at the 7700 combo, b/c like i said... Always gotta look to go faster. I wish i had a speedo/ radar, i regeared last night and it's sort of a blur now, well not really but compared to what it did out of the box, it's exponentially faster.

[ElectricThunder]

Lipos act much different than NiMH. For one, they handle higher discharge rates far better depending on pack's spec (for example, a 4600mah 20C lipo is good for 92 amps continuous, but a comparative NiMH would probably get quite warm under the same conditions). Lipo has less internal resistance, which helps them discharge such higher currents readily. Also, because of that lower resistance, their voltage at a given load stays higher than NiMH, so you get more power out of the pack. Lipo tends to way about half a pound lighter if you compare it to its Sub C counterpart. Lipos also have longer cycle life compared to NiMH.

Lipo isn't all boogity boogity like some people make it out to seem. Any battery can hurt you or do damage, so any battery needs to be treated with respect and proper care.

[miata_speed85]

so what would i be looking for if i wanted something to fit in the same space as a 6 cell NiMH pack? The problem i have is the ESC placement on the Traxxas limits battery space. and the M has a molded slot in the chassis for a battery... Oh and geared 31/76 doesn't really heat up the motor if i ease up to top speed, and stay in a steady path of travel. so for now it stays.

[ElectricThunder]

Most ROAR legal packs fit in about the same area as a 6 cell NiMH pack. Those tend to have hard cases too. Neu Energy (enerland cells) has a 2s 5000mah 20C pack in a hard case. It's probably about the same size as a 6 cell NiMH. The pack may be a bit taller due to the hard case though.

You can also go with packs just wrapped in shrink too. There's tons of those out there. I would suggest, if you're on a budget, to try out the Elite 4500 25C 2s packs from cheapbatterypacks.com. It's about 65 bucks for a 2s pack there.

Considering you're running the 7700 (so I've gathered from your last post at least), and you're limited to 2s (from a warranty and safety standpoint), I think it's best to get a battery with about 100 amps continuous as a rating. Even higher would be better, especially at that gearing for a 7700! I wouldn't be worried about the motor so much as the poor battery that has to supply the current for such gearing! The motor will probably get hot if you get over ambitious and run it for more than a few minutes and actually bash around with it. I'd suggest also to not run such high gearing with such a "hot" motor on a regular basis. It may work great now, but considering it's probably pulling huge current to create torque to move those big gears, a lot more amperage is flowing through everything, and that may wear things out faster since they're being subjected to a higher load over a more consistent time period. I can understand speed run purposes (if you're REALLY interested in speed for your bandit, high voltage, low kv setups offer some SERIOUS power and speed potential).

But anyways, snoop around on towerhobbies or any other hobby sites or whatever you have access to and see if you can find a lipo that suits your liking and has similar dimensions to a 6 cell NiMH pack. Then, if you want, check back here and post your findings, and I'm sure someone can help you pick out a good pack that will serve you well. I'll be glad to help out. And share my experiences with you for brushless and lipo setups.

[miata_speed85]

i just bought a couple 1600 2s packs and a balance charger by trinity, as i purchased these before your post i'll have to look at the cheappacks site. Now i thought that the higher the kv that higher kv = higher speed, but from what you're saying now is that i could get higher top-end with a 4600 kv motor? Speaking of the bandit and bashing... as of now i am only running on pavement, as i know from previous experience that high gearing and bashing is bad. if i were to bash i'd lower the gearing back down to 20/90 for higher torque... that much i can understand. I think that i will be on a standstill until the lipo packs get here with my TRA connectors, and i get those soldered on. All my parts for my m-chassis got here yesterday, so i'm going to get started on puttingthat back together and run that brushed for now. Thanks for all your help, I'm still a noob but you're definitely helping me gain knowledge and experience. I appreciate your willingness to share your insights... regardless of the random questions i post.

[ElectricThunder]

Higher kv does not mean higher speed if you know how to set up a lower kv motor on the right voltage. On a set voltage, like 7 volts, the higher kv will tend to be faster, yes, but if you open up the possibility to say 11.1 volts (3s lipo), a lower kv motor will not only be more efficient, but will be able to spin a respectable amount of RPMs while still having the gearing flexibility that lower kv motors have. A high kv motor cannot take near as much voltage due to physical forces acting on the rotor that tend to make the rotor tear itself apart. The more voltage you pump through a motor on a set load, the more current it draws too (this is why lower kv setups tend to be more efficient; they don't need to draw as much current to create the same amount of torque).

The take home point for motors is that there are two ways to go about getting a specific speed. High kv, low voltage, high current (tends to generate heat!), and tiny pinion gear............OR, low kv, higher voltage, lower current, and a larger pinion gear depending on how fast the motor is spinning and pretty much dependant on batteries' and ESC's capabilities and how fast you want to go.

Lower kv and higher voltage offers more flexibility, efficiency, and overall available power (think of it in terms of the batteries; a 7.4 volt 100 amp cont. pack is 740 watts optimistically, whereas an 11.1 volt 100 amp continuous pack can theoretically put out 1110 watts). You also get more power output from the same input for high voltage, low kv setups because if efficiency increases, that means that less and less of the input wattage is being lost in the form of heat, so the motor effectively puts out a little more power.

By that same token, you CAN see higher currents in a high voltage setup as well. Voltage divided by resistance equals current, soooo, if we keep the same resistance (such as using the same motor kv on 11.1v and 14.8v), the setup on 14.8v will draw more current if A) the motor kv is not changed and B) if gearing is left unchanged.

I'm probably getting ahead of myself and this is probably more than you'd care to know right now (plus it's 2:30 in the morning so I'm falling asleep fast...lol).

Next, what do you plan to use the 1600 packs in? I can guarantee that they will not be able to supply the necessary current that a 5700 or 7700 setup requires, and if anything, you will damage the packs. Battery selection is possibly the most important part of selecting a proper setup IMO. It's right up there with motor selection, but if your batteries can't supply the juice the motor wants/needs, then your ideal motor is as good as a paperweight for the performance you wish to see.

[miata_speed85]

Ok so I canceled the current oder on the 1600 packs for 2 4800 2s packs, what are the Tap options for? i tried looking into it but they seems to talk around it everywhere i looked. i think that i should be set now... it's just a waiting game now... as always.

[ElectricThunder]

Taps are just a way to measure the cells' voltage individually. They are also used for balancing lipos (keeping a pack in balance is quite important). Lipo cells need to be within a certain voltage of one another so that one cell doesn't get prematurely discharged due to the other cell having more capacity and thus a higher voltage under load.

The align and/or JST taps are pretty versatile, but if you get a balancer such as the astroflight blinky, most connectors physically fit just fine (as long as the space between pins is .1mm). Some oddball ones may require rewiring though, like the Thunderpower taps (they should still physically fit on an astroflight blinky, but the actual wiring order is different).

[miata_speed85]

this is all very helpful information. I'm kinda speed reading it now, since i'm at work, but when i get a chance to look at it later i'll be able to absorb it. I understand everything that you're saying since i am in communications and deal with electronics almost daily. we don't apply the current, voltage and resistance, but it has been taught to us when we were in the school house.

[miata_speed85]

well $137 later i got what i need, and about $80 at amazon i got my charger... should be set when it gets here... this is the part i hate though, the waiting and impatience that i have... it should be worth it though.

[ElectricThunder]

It's fascinating stuff when you get to see the real world results in our cars and trucks. Anyways, take time to soak in everything.

The hardest part IMO is coordinating how fast you want to go, what motor you want to run, and what battery you want to run. If you can nail two of those three things down, the third will follow suit. Usually, the first thing is how fast you want to go, and then work it out from there. Find out wheel RPM necessary, and then go through a few different gearings to get a few different kvs, figure out voltage necessary to spin the motors to the given RPMs necessary, and then you should have a few nice little choices to check out.

[GSMnow]

1600 LiPo packs will not be enough current for a 1/10 setup, maybe if you used 2 in parallel, but even then... What is the C rating of those? At 20C they would be able to handle 32 amps, great for a 1/18, not 1/10. I am running 20C 3000 packs from Max Amps and they are getting too hott pushing my Mamba Max 5700 in a Losi XXX-4.

Unless you are at the thermal current limit of the motor, the KV will not change the total power that much. Im the case of the Castle CM36 motors, they will all easilly handle 500 watts, more than most batteries will take for constant running. What this means, is you just choose the motor KV to get the RPM you need to work with the gearing in your car/truck. You take your battery voltage and multiply by the KV and figure back what gear ratio you need to hit the desired tire speed. On a 6 cell NiMh pack, gear it for about 35 mph and it should run solid. With a smaller 2S LiPo, you can go to a bit over 40 mph. Now the motors also have an rpm limit. The 4600 and 5700 will be safe on 3S LiPo, the 6900 and 7700 will not be reliable at 3S because the rpm is over the rating of the bearings and rotor magnet. It will not live long. On 3S the 4600 and 5700 turn about the rpm of the 6900 and 7700 respectively, but are now able to handle over 700 watts, same current, more voltage. This means you can gear for over 60 mph on 3S for the same motor heat.

If you have a very good battery pack, the 7700 on 2S or 6-7-8 NiMh cells, can be geared to go a little faster than the 4600 or 5700 because it has a bit less internal resistance, so it will not get as hot when pushed hard, but the currend demand is very high. You really need like a 6000 LiPo to get it all. Unless you have rules limiting the voltage, the 3S 5700 (or even 4600) will run much better than a 7700 on 2S.

From my experience with brushless so far, you are best off picking the motor KV so that you can pull full trigger, and hold it until the motor actually does top out before you get to the end of the straight. If you are geared to high to use that, gear down, and if you can't gear down, your motor KV is too high. Open area bashing, sure you can run higher speeds, but on a race track, having a car faster than the fastest possible section of the track, is not just a waste, it is much harder to drive on the track. I started out setup for 45 mph in a 2WD stadium truck, it was near impossible to make a good lap. I was being beat by all the 19 turn guys. When I slowed it down to 36 mph, my lap times dropped, and I have 2 series trophies now. I moved the 5700 system into the XXX-4 buggy, and I am now running 40 mph, and it is hairy, but fun. I have a little 16 tooth pinion to a 94 spur in there. The 5700 on 2S LiPo is a very serious power house. My truck is going to be getting a ROAR legal 13.5 for super stock. 2WD needs more finesse than the raw power of the 5700. And then I can run 2 classes as well.

[ElectricThunder]

I don't think he's racing at all. I think he just wants sheer speed and straight line fun. At least this is what I've gathered.

[miata_speed85]

seems like you hit that one right on the head. i have a brushed motor that i can swap out for bashing but when i got my brushless in I just enjoy going fast. I'm relatively new to RC so i still get happy with sheer straight line speed. i take it to the edge of my radio range and turn it around, and bring it right back to the range limit in the opposite direction. i have a 2/3 mile long straight and flat track we use for our physical training tests, so as long as no one is on it, it's perfect for what i need. and it keeps me from getting yelled at by the MP's for driving in the middle of the street.

[ElectricThunder]

Kinda like what I do. I'll just run the RCs all over the street and in the back yard and the big ditch behind the house. I jump the Rustler all the time with some Mashers on it, and put it through its paces.

My TT-01 I reserve for parking lots. If I was super ambitious, I could probably use it for racing with a few tweaks here and there, but I have no desire to race. Too many rules that restrict me, and I hate that. The whole reason I got into the hobby was for no restrictions on power output, tire selection, battery selection, etc. If I want 1 kilowatt of power for my truck, then darn it I'm gonna run 1 kilowatt worth of power!:D

Baseball fields are the best with the offroad trucks btw! Rooster tails are so much fun....:D

[GSMnow]

miata_speed85... It would certainly be interesting to run a data logger on a car setup like yours. I wonder if you are ever topping out the rpm with gearing like that on the 7700. Rolling the throttle on slow does help lower the peak currents to lower the temp. That technique is used by most of the fast guys at the Car Action fastest RC car shootout. But if the drag of the car makes the wattage demand greater than the battery capability, you could be dragging your pack down to 4 volts instead of 7. Going with a smaller pinion might actually make for a higher top speed. And a battery that can't put out enough current for the motor demand will certainly make the motor run much cooler too. My motor temp went up quite a bit when I went to a strong LiPo.

I forgot which chassis you had the 7700 in, but on 2S LiPo, the 7700 turns over 53000 rpm. 31:76 turns the spur at 21,618. I will guess at a 2.5 trans ratio and 3 inch tires. 8647 tire rpm. That works out to 77 mph. That is not going to happen on 2S unless there is either a serious tail wind, or the car has no aero drag, and the chassis is dead on perfect frictionless. Going to a 24 tooth pinion will probably go just as fast. And it will accelerate much quicker too. Of course, if your final trans ratio is much different than 2.5, or if your tires are smaller, you can go a little higher. The idea here is, gearing for 60 mph at volts x KV is still pushing the limits for 2S.

[miata_speed85]

it's a 5700, i'm not on the 7700 yet, and i don't see myself doing it now that i can achieve top speed with a smaller motor... Thanks for all the info....

[miata_speed85]

the 57 is in my traxxas bandit. I just got my M04 up and running again, the only downfall is the servo i have is meant to be mounted upside-down, and consequently left was right and visa-versa... after countless hours of figuring things out, i ended up disconnecting the steering linkage, i turned the center piece 180 deg. and had to saw away at the chassis. So there was a mess of shredded plastic everywhere. The downside with that is that i did it all with a double-toothed leatherman saw. Well the project is complete now and my most extensive modification to the cars yet... i must say that with my lack of tools, i'm rather proud of the way it turned out. I should be alright as long as i don't hit anything at high speeds, otherwise the chassis mods might have made it a little weaker than i would have liked... The best alternative to mounting... especially if it's permanent... SUPER GLUE.

[miata_speed85]

GSM could you post the equations you used to figure that out? Or is any of it was rough guesstimation, then how you came up with that. thank you.

[GSMnow]

In a perfect world with no losses, the motor would reach a top speed determined by multiplying the batery voltage and the KV. So a 5700 KV at 7.4 volts would hit 42,180 rpm. On a full charge, a LiPo will actually be over 8 volts, but due to internal resistance, ESC resistance, motor resistance, etc. You get a more realistic useable voltage of about 7 volts to the motor. So 7 x 5700 = 39,900 rpm is a closer guess. Let's say your trans has an internal ratio of 2.55 (My XXX-T MF2 truck) and your tires are 4 inches high. You figure out that you want to go 35 mph for a rough top speed. 35 mph is 35 x 5280 = 184,800 feet per hour. Divide that by 60 to get 3080 feet per minute. Take the tire height x pi (3.1416) and you get a roll out of 12.566inches per rev / 12 = 1.05 feet. 3080 / 1.05 = 2933 wheel rpm. Multiply by the trans ratio 2.55 to get 7480 rpm at the spur gear. We already figured the 5700 motor will be turning 39,900 rpm, so divide that by 7480 and we need a pinion to spur ratio of 5.334 to 1. I use an 87 tooth spur so 87 / 5.334 = 16.31 tooth pinion. I used anything form a 15 to an 18 depending on track conditions and layout. And you can get a very rough idea of speed with each gear once you find one by taking your calc'd speed divided by the pinion you got. 35 / 16.31 = 2.15. So with this spur, I will go 2.15 mph for each pinion tooth. So with the 18 on there, I should hit 18 x 2.15 = 38.7 mph, and the 15 should go 15 x 2.15 = 32.25 mph. Your speed will vary from this due to voltage of the battery due to charge level and temp, and also from tire growth at rpm, but it will get you in the ball park. Gear for your desired (realistic) speed, and then fine tune with motor temp from there.

My current setup in the 4WD is 17 to 94 and 2.1 trans ratio with 3.2 inch tires.

(39,900 / 94) x 17 = 7216 rpm at the spur
7216 / 2.1 = 3436 rpm at the tires
3.2 inch tires x 3.1416 = 10.05 inch / 12 = 0.838 foot
3436 x .838 = 2880 feet per minute x 60 = 172800 feet per hour
172800 / 5280 = 32.73 mph.

Due to tire growth it is actually hitting closer to 36 mph, and it is hitting this very quickly. I would like to go up about 2 teeth, but my 20C 3000mAh LiPo's are getting too hot.

What are you using for a radio system? It has been a long time since I saw a transmitter that didn't have some way to reverse the servo travels. Sometimes it is a hidden switch, or a menu setting. On my old Futaba Magnum Jr the swithes were in the botom of the antenna storage slot. On an RTR Duratrax radio, it has switches right next to the trim knobs. In a serious pinch, you can open up the TX and switch the outer two wires on the steering pot. On both of my Losi's, there is no way I could flip the steering by puting the linkage on the other side. There is just no room for anything like that.

[miata_speed85]

I'm just using the TQ that came with my RTR bandit... it works, and gets the job done, I'm not looking to get t odeep in when I'm over here due to the limited time i get off to run it, and restrictions of places to run... b4 it was great and no one bothered me but when i got clocked by the MP's doin 60 they got kinda pissed and kicked me off the road. I can't wait for my LiPo's though... i just hope that either the charger gets here first or they both come on the same day. Nothing is worse than waiting for that last part to get it all together. I waited 2 weeks for my servo/receiver. In terms of the servo. It's all good now. I redrilled mounting holes for the servo, moved it forward and flipped the linkage... There's barely enough room for it to clear the servo box, but it works, and i'm rather satisfied. I just wish i had a dremel... Good thing my room mate just bought one, I'll be able to clean up my rough hack jobs and make i look pretty again... not that it matters when the body goes on. Thanks for the walk-through on the speed calc, I'll add it to excel... make it nice and easy... It's actually rather simple after it's laid out... I worked mine out with a 31/76 and it's about and with a circumference of 1.204 ft (4.6 diameter) works out to just over 81 MPH... but like you said i'm sure my lipos will get hot but my NiMh are pretty warm with that, but i'll tell you what if i hit 81 I'll be stoked... thanks for the help

[GSMnow]

WOW! that is geared very high for a 5700 on 2S. The current will be insane. On even the best NiMh poacks, the voltage will drag down, probably to more like 5 volts under a load like that, and the motor will get hot if you do have a pack to supply the current. I would not go any bigger than a 21 tooth pinion. In a big enough area, that works out to 55 mph which is still really pushing it. For speeds over 45 mph, you really should be running 3S LiPo and gear it for more motor rpm.

[miata_speed85]

Now what if i would connect 2 7.2 NiMh packs in series... push it up to 14.4... well more like 12 i would then be able to provide a voltage and current possible for running the brushless... correct? Well as stated before i was doing speed runs. i usually have mine geared around 24/90 The motor has been staying cool on full throttle... even with 24/76 it wasn't to hot to hold.

[GSMnow]

12 cells of NiMh in series is fine on the 5700 motor and the ESC, but your BEC will run hot, especially if you have a high torque steering servo. You may want to run an external BEC at that voltage just to keep the inside of the ESC cooler. With that much voltage, you will really have to go smaller on the pinion gear. And how much bigger of a spur can you fit? Gear it for 12 volts to run 60 mph, and it will be a blur. The motor shuld actually run much cooler with the higher voltage. You will get over 1HP at under 65 amps. To get 1 HP on a strong 2S LiPo takes over 100 amps. The top speed competition cars were running 6S and 8S LiPo's (22.2 or 29.6 volts) on larger helicopter motors around 2000 KV. Only 50 to 60,000 rpm with a ton of torque. Nic Case's car ran close to a 1:1 from the motor to spur in a converted Nitro TC3 to top 130 mph. Of course, there are not many car ESC's that will do that, he used a Castle Creations Pheonix HV110 airplane ESC. The New Castle Mamba Monster will do 6S (22.2 volts) at 200 amps. With a 2200 KV motor, it will put you right up there on power.

[miata_speed85]

I might have to look into the airplane ESC's when i get back home... over here it's way to dusty to go any faster than i am already without sacrificing control... and at least back home i can go to an abandoned air strip, or very large parking lot. i know that the sidewinder has a voltage limit of 15, are there respective voltage limits on motors as well, or will it take whatever the ESC throws at it? And what is the result of running LiPo with brused set-ups? not that it's needed but if i'm going lipo i might as well do it to everything...

[GSMnow]

The voltage limit of a motor is usually the rpm limit of the bearings or rotating parts coming apart. Very low KV motor may have a limit of ho high the voltage can get before arc over between windings, but even the tiniest motor probably would not arc over until 150 volts. RPM is the big concern with most car motors. The Castle CM36 motors are safe to about 70,000 rpm. 15.2 volts on the 4600, 12.3 volts on the 5700, 10.2 volts on the 6900, and 9.1 volts on the 7700. So as you can see, 4S on the 4600 is right there, 3S for the 5700, and 2S on the 6900 and 7700. You may get away with a little more, but then you are out of warranty and there is a chance of the rotor blowing apart and destroying the whole motor.

[GSMnow]

And... Brush motors do respond well to LiPo with a bit more power, but it also makes them eat the brushes faster from the greater current when loaded at lower rpms. The battery voltage of a strong LiPo does not dip near as much as most NiXx cells, so the current surges can be quite a bit higher.

[miata_speed85]

Well outstanding... I figured it would be ok. What I was worried about was motor life, Now that I know that it won't kill it then I'll just have to purchase some brushes, or find a brushless motor/ ESC combo to run with. There's a good chance I'll just keep that little bugger brushed for now, granted i can keep the same speeds if i geared it right, but then I'd get excessive torque in exchange, and like i stated before, dust and torque not a good combo, I have a difficult enough time trying not to hit stuff top speed as it is.

[miata_speed85]

Brushless is the sh*t with the Lipo packs... I'm amazed at the difference the packs make, but it's amazing. I just got it out for the first time last night, and I loved it... Now i just have to remember to gear it back down...

[miata_speed85]

So apparently going to brushless with Lipo isn't exactly all that kind to the idler gear on the Traxxas... it sure did love to do wheelies from a rolling start though. I was lifting the front end up from about half throttle. When i tried to pull a rooster-tail in the sand it kinda got angry at me. I shaved about half the teeth off. I found out that the VXL's have a metal idler gear, with the same teeth, so it's on the way. in the mean time my room mate sold me his stampede for $100... which i s pretty sweet deal, except for the fact that i have a real basher now, and i'll want to hook it up. I can't have 2 cars that haul a$$ and then get one that is bone stock, it's no fun, the later would collect dust. So brushless conversion... prob 4WD conv. too. It should be interesting what comes of it, if nothing else I'll send it home to my girl to mess with the dogs. But back to brushless. right now i geared back down to 18/90, everything's staying cool, so that's a bonus. The charger/balancer i bought is painfully slow though. It took some 5 hours to charge a 7.4 V 4800 pack. but is it normal for it to use the tap as a charging point. I understand that it's for balancing purposes, so i'm assuming that it does double duty with that. I bought a new charger the other day... well b/c i just can't wait 5 hours for a battery to charge up. One question though, are there any storage procedures for a Lipo pack, or can i just got ahead and leave it on a shelf... I was reading about a guy puting it in a plastic bag and burying it in a planter... And what about discharging. Enough babble, there's little of importance in here. just keeping y'all posted on progress, and trying to tie up some loose ends with the Lipo thing. Appreciate it.

[GSMnow]

The balance ports on most packs should have no problem handling 2 amps. As long as it is a fairly slow charge (over 3 hours on your 4800) the balance port should be fine. As the pack tops out under CC/CV charging, the current falls very low, so the balancing is still very accurate. At higher current, the resistance of the thin balance wires could put in a bit of error and allow some imbalance. Most LiPo's are only rated to a max charge rate of 1C, which in theory would mean 1 hour, but you only get about 80% in the hour due to the falling current when the voltage tops to 4.2 per cell. You can certainly take it off the charger and go running at that point, and just get 80% run time with no harm done to anything. The last 20% will take well about 20 minutes depending on the charger and pack. Some very high quality packs will take up to a 2C charge. I have gone as high as 5 amps on my 3000 packs, but it does not cut the charge time very much because it just reaches 8.4 volts (4.2 x2S) sooner and has to still lower the current to keep the pack at 4.2 per cell. At 5 amps, a full 3000 mAh charge is still taking about an hour. The pack stays dead cold, but I don't make a habit of it, high charge rates will greatly shorten the number of cycles you will get out of the pack. I had to at my last race, with only 5 heats I needed a pack ready in 50 minutes. I have 2 packs that I alternate. I can run for 10+ minutes, let it cool 20 and be back out with the second pack for 10 again, but then I need to wait 40 minutes for the first pack again. With 2 charges at 5 amps (1.66C), I could make a 10 minute run, about every 40 minutes. You just need to be sure the pack is cool before starting the charge.

As for storage...
The best recomendation is to put about 1/2 to 3/4 charge into them so that they have plenty of time to not self discharge below 3 volts per cell, and even with extreme temperature changes, they won't exceed 4.2 volts per cell. I store mine at about 4 volts per cell, and then top them off the night before going racing. If they will sit more than a wek, it is a good idea to just check the voltage of each cell at the balance port. Any cell under 3.5 volts should get some charge, and the cells should be balanced for longest life.

[JEAM]

About battery-packs getting warm I have a question !
Am I correct its also the "other way around" ? What I mean is when you should be able to cool the batteries during driving, the runtimes will increase ???

[ElectricThunder]

Something to remember about batteries is that they produce a current and voltage through chemical reactions. If the battery pack is cooled to a certain point, the chemical reaction is not being carried out fast nor efficiently (and in some cases, the required activation energy may be so high that the battery will just poop out; say the electrolyte in the battery freezes for example). Of course a battery runs cooler when load that is placed on it is lesser than normal. If you have a battery pack that has to crank out 50 amps continuous versus 10 amps continuous, the latter is probably going to run cooler and have a longer run time provided we use the same pack for either setup.

So....it's hard to give a definite answer to that because there's a few reasons why a battery may run hot or cold or warm. And that temperature at which it runs at certainly affects performance, and the cause of the temperature (especially if it's load related) will affect runtime.

It'd be interesting to see how different temperatures affect runtime on the same exact setup. I'm willing to bet that a warmer climate lowers runtime due to higher temperature of all components, and thus slightly more resistance, more heat, and so less efficiency (this is compared to a significantly cooler climate, say by around 15-20 degrees fahrenheit).

[miata_speed85]

So driving in the desert when it's 115 would be say more demanding of running in a climate around say... 65 in WI. If i was bringing my car back to the states when i come home on leave I'd let you know what i found out... i might just mail it back to find out... I will say that driving during the day is much more different than driving after the sun's gone down... So your theory does make sense.

[ElectricThunder]

I wouldn't doubt that running in hotter weather shortens runtime and definitely increases temperatures of everything. I've noticed this going from a "winter" climate here in Florida (around 60s at night and mid to high 70s during the day every so often) to a hot summer climate like now (85 to 90 degrees or even more sometimes).

Ambient temperature certainly impacts performance and how everything runs for sure.

[miata_speed85]

It also depends on how you are driving as well... If i run it hard full throttle at night, it's about the same run time and temp. as running in quick short bursts during the day. Also as you already know, going from a dead stop to full creates massive power draw. So we're back to a rolling throttle increase to maintain... as well as keeping the front wheels on the ground. I try to have a general rule of thumb during the day, to smoke a cigarette while driving, and smoke another with it off in the shade. Repeat until the battery is dead. This is geared 18/90 so it's not the gearing but things do get alittle warm if i run it full and steady... during the day anyways. Your winter is like my parent's summer right now... Pretty sad.

[ElectricThunder]

I drive my truck the same all year 'round. I jam down the throttle from a dead stop all the time, try to get as many rolling wheelies as possible, and do donuts all over the place. Anything I can do to get some sort of heat out of my motor I'm using (never gets above 135F in the summer, and in temperatures of around 70 ambient, never cracks 115F).

You're right though. How you drive affects a lot of things too.

Right now it's 88F out, but with humidity, it feels like it's 90+....:( I hate muggy summer days.

[miata_speed85]

I know the feeling, the air over here is rather heavy. It's been up on average around 110. a coupe scorchers so far but since I'm near the coast i don't get the benefit of dry heat. it's about 85% humidity all day every day. well except in the morning when the humidity tops off around 95ish. enough for a good dense fog to roll in. the only thing worse than the desert is being in a muggy desert... yet it never seems to rain here :(

[JEAM]

Second reason I brought up the Temperature-issue is:
I,ve got a HPI E-Firestorm and I discovered the last battery in the pack (which is stuck in the back of the truck) has been "overcooked"

I drilled holes like "crazy" to cool the damn thing but I think its due to the construction of the car, (see pics)
If I go on drilling holes in the chassis, there,s not much left to drive with haha....

SO, PLEASE HELP ME OUT HERE GUYS,
(Its almost summer aprox. 77F, about 5 weeks we goto Italy for holiday, temps are +88F overthere !!!)

Setup: MambaMax5700 > MaxampsNiMH 7Cell > Pignion18th > Spur 87th

[JEAM]

Another 2 pics, same issue,

[GSMnow]

That end cell is probbaly damaged now. Try turning the pack around, and I bet the same cell still gets hot in front. The restricted air flow in the back bulkhead certainly didn't help, but it is not like the rest of the pack has all that great of air flow either. If that cell has lost some capacity, your charger could be overcharging that cell, waiting for the others to peak, and when you run, that cell goes dead first and goes revers polarity. And the cycle repeats. I had that happen to two packs, the cell that dies was in the middle, but it was so obvious, it got much hotter than the rest of the pack. I did end up replacing the bad cell, and I still use those packs today, but they are nothing like when they were new.

[miata_speed85]

My suggestion is that you're running brushless with NiMh. although it's not really an issue I notcied that when i was doing the same the the backs were getting warm due to the demand of the motor. I would ulimately suggest going Lipo. I was against it due to the price for a long time, but when i finally broke down it was worth it. The power increase overall made up for the extra change. Eric gave a me an outstanding site to find goodies at a low cost it's cheapbatterypacks.com, If you want top performance Lipo is the way to go. You have an option of putting in the dimensions of available space, and can go from there. you'll at least want a 2S 4800 mah. Like i said though it's a bit of cheese up front, but in the long run it pays itself off in enjoyable experiences. If i saw right you're running pretty much the same set-up that i am, and your HPI probably runs around the same weight to. I have a 5700 motor run with a castle sidewinder. I strongly suggest Lipo... it will make you smile... and it will run cooler.

GSM made some notes as well on running voltage on an earlier post somewhere around page 2 or 3. that's where most of the battery infor on this post is located. Thanks to Eric and GSM there's a lot of answers to some basic questions, as well as some detailed ones going into theoretical speed (based on gear ratios, tire size, trans ratio, motor rpm) Lots of goodies in here. Thanks to me being a noob and these guys willing to share their knowledge. take care, good luck and have a blast in Italy.

[JEAM]

Thanks, you,re right :teacher:
I,m fed up with it.......gonna plunder my bank account and get 2 Lipo,s ASAP !!!
Thinking of 2 x Maxamps 2S/6000, that will do the Job properly.
ps. I try to persuade my girlfriend take some pics when I,m bashing around in Italy haha

[miata_speed85]

If you are looking for a good deal go to cheapbatterypacks.com they are much more affordable. and it's my opinion that maxamps packs are overpriced garbage. You may not feel that way but if it's more about bang/buck. cheap battery packs is the way to go. The onlc edown-side is you need to solder your own terminals on. Whatever you decide, make sure that you get a lipo charger as well as a balancer. there are plenty of options with a broad range of cost. the cheapest i found was $38 and the most expensive so far ranges up to hundreds of dollars. Just make sure that if a balancer is not included that you find one as well. Good luck and happy bashing.

[JEAM]

I,ve simply cut the bad one off (and lost 1.2v offcourse :( )
but al least I have my "old" runtimes back.....also all cells seem to have the same temperature, tnx guys

[miata_speed85]

Well all is well in the world of R/C currently. my idler gear wasn't to happy with the torque of a brushless motor, so i got a metal 30 tooth, and a planetary gear set, with steel ring gear... Backto bashing. I really can't wait to get back home at the end of this deployment and drive this thing in grass, and dirt... rather than sand with large rocks everywhere. I did however just find a place to launch my car, and it just so happened that there is a perfect landing on the backside, so thankfully the chance of damage is greatly reduced. I'll post pics whenever i get some one to come out with me.