Mamba 6800 or 8000 ?

[Diesel72]

So I have decided to get a brushless system for my rc18t, and have come to realize that I know precious little about electric vehicles at all! So, after a fair amount or searching, I have decided on a Mamba w/6800 or 8000. I have 7 cell gp1100 batteries on the way, so I have good batteries (I'll be getting some 5 cell packs made up too, for the m18 I'm gonna get).

So the real question is; is there a benefit to one or the other of these motors? I know that the 8000 will have more top end with the same batteries, but does it sacrifice torque? If the 6800 has better torque, I might stick with it...

[strodedawg]

i run the 6800 and it runs great. the 7 cell pack and the 8000 might make the 18t uncontrollable without a good control of the throttle. the first night i ran the brushless i did horrible as i was not used to the increased power and speed. just a thought.

[kcobra]

I went with the 8000 in my RC18T last weekend. I just bumped the throttle down to about 60% and it worked well. At 100% it would just get away from me to quickly.

[studysession]

I run a 8000 in my Micro RS4 and love it. It is crazy fast.

[ducati777]

Uhhh why does anyone think the 6800 has more torque?

I'm speaking theory here, but I'm betting the 6800 simply uses more windings, its a higher turn motor. It'll make less power, less torque, and use less energy. Thus the tradeoff isn't more torque less rpm, its less power more run time.

I did a little math on the 8000 and with a 8 cell pack, 12 tooth pinion, optional 60 tooth spur, you're lookin at 45 mph... That pretty quick for any rc, and probably stupid fast for the rc18t. 6 cell should be about 34 mph on the same gearing, which sounds about right.

My only question is what sort of run times does a 8000 get? I'd like to get at least 10 minutes out of the car, and I'm thinkin I might have to go 6800 to get it.... Anyone wanna relate run times?

[studysession]

I get 15 - 20 minutes on my 8000 using 6 GP1100 cell's. It is a crazy fast motor. I would not bother with the 6800 or anything else lower. The 8000 has pleanty of torque for a 1/18 scale MT. I have seen other use them with no problems.

[ducati777]

Crap study.... Thats good news man, I knew brushless was more efficient, but ididn't know if the 8000 would draw so much power that run time would really drop off.

Mmmmm drooling over the 8000....... I really want one.

[ElectricThunder]

Ducati- A general rule of thumb for BL motors (and brushed for that matter) is the higher the turns, the more torque there is. A higher Kv means torque must be sacrificed. Kt and Kv are constants. When one goes up, the other goes down, or some jargin like that. Higher Kt= lower Kv, and vice versa. But then to make up for torque you can use a larger rotor...yada yada yada. I kinda forgot why I just wrote this post... :eek:

Anyways, if you're gonna use a BL in the RC18T, I've heard that it's weakest drive train components are it's drive cups, and that people shred them slamming it from forward into reverse, and vice versa. Other than that, go for the 8000 :cool:

[ducati777]

I just bought the 18T for myself as a christmas present. Merry christmas to me!!!

I'm feeling a lil guilty about springing for the 8k mamba right now, and plus I'll need the aluminum cv's... and I just got the aluminum shocks...

Gotta pace myself!!! Phew, one thing at a time... probably cv's first, as the truck will be useless if the mamba just shreds the stockers....

But back in physics we did equations on electric motors. And when talking about a standard brushed motor, voltage will dictate rpm of the motor... just saying more volts results in high rpm... not higher rpm per volt or anything...

Anyway the equation for the electric field had volts times amps in it. V=IR, P=IV.... So in that case you could increase turns, which increases impedance, and thus decreases amps and electric field... thus less power. Or you could increase diameter of the windings to decrease imedance, increase the field and thus rpm/torque....

But I'll freely admit I don't know a whole lot about the world of brushless setups. Its new to me, and I can't wait to get my hands on some. The video of the MP777 with a brushless/lipo setup was sick, I'm trying to do that on a small scale with the RC18T...

[studysession]

It depends on how hard I hit the throttle. At half throttle my Micro RS4 does 35MPh with a 15t pinion. I am afraid to go any faster.

But yeah it is nice. I think 15 - 20 minutes is good enough for runtimes. With my speed cars my batteries are dead in less than 1 minute. With my 1/10 scale touring cars I get almost 10 minutes. So when I was getting almost 20 minutes run time with the MRS4 and the Mamba 8000 - I thought it was great.

http://studysession.com/Car-MicroRS4.html

SS

[OptimaMan]

Hey Ducati777: I have a mini T when geared FDR of 12.5:1 using the stock tires, I get a true speed of 38 mph (radar gun verified many times). My batteries are some real cheapo 11.1 volt LiPo packs that drop down to 8.9 volts during those runs. If I had higher discharge LiPos in my mini T, I'd be in the mid 40's mph. My pinion is 13 and spur is 60 and the tranny ratio is about 2.7:1 I believe. I'm using the Mamba 8000.

With regards to torque: More winds = more torque/amp. However, having less turns and using thicker wire, it'll draw more amps so actually torque is probably similar. Higher kV motor will just be more powerful given the same voltage hands down. When I used to have my HiMaxx 5400 motor (5400 kV) with the same gearing, I used to get 29 mph with 11.1 volts (voltage drop was less because I was using better batteries before and motor draws less current).

I was ---> <---- that close to getting the RC18T. When I saw all the possible upgrades, then I realized it'll be another money pit so I didn't get it. More importantly, they didn't have any lipos that were thin enough to fit into that battery tray so I wouldn't be able to use LiPos.

[ducati777]

"I was ---> <---- that close "

Thats funny stuff. I've been punching up number in excel on possible speed numbers, and you're reports are close to what I was calculating. I think I'd be happy with 30ish mph... But I keep thinking about the 8k mamba I saw in a mini T, the guy couldn't keep the front end down. Any speed it seemed to wheelie at will and I was hooked on the idea.

It would be nice if the rc18 would wheelie, but its weight bias is a lot different.

As far as Lipos... I'm certainly curious about them but I don't see them in my future. It would require 2 packs probably, and a charger... which is just another chunk o cash. I think I'll stick to my 1100 packs... Especially if I can get more than 10 minutes out of them.

But this is all really good information guys. I think you've convinced me that I need the 8k. I do wonder how well the driveline will hold up... but ball diffs and aluminum dogbones should be a good start.

[SpEEdyBL]

Take the SS5800 and SS4300 for example. They both have 0.45 in/oz/amp of torque. However, the 5800 will draw more amps to reach its higher rpm, therefore it will have more torque.

With a given voltage input, it may seem like the higher turn motor has more torque due to less voltage drop under loads. The higher turn might also have a higher accel/speed ratio, but try decreasing the gear ratio of the higher turn motor until the top speeds of both motors are identical. The higher turn motor will definately accelerate slower since it's less powerful than the high turn motor. If that statement was false. Low turn motors would be pointless.

What gives higher turn motors an advantage is the higher cell count they can handle (to reach the power of the higher turn), which also provides longer runtimes and better effiecency.

So yeah. The 8000 will have plenty of torque. My friend has one, and it' uncontrolable.

[starluckrc]

OptimaMan said it best so far. Kv and kv are inversely proportional. All motors in a given series (i.e. Hacker C40-**T) have the same total power and torque and rpm output. They use different voltages and currents to reach maximum rpm. The lower kv motor will use less current, and the higher kv motor will use less voltage but require more current. On the same voltage, provided that everything in the system is up to par, the higher kv motor will have more rpm and torque than the lower kv motor. All generalizations of course.

[suprapimp22]

Niether of them have that great of torque. In a carpet track i run at, there is a 6800 and a 8k in mini-t's....I run brushed and beat them almost any time....they are either to fast....or cogging, they just dont run good in general on small tracks.

But if your jsut going for bahsing get a mamba 8000kv.


Check out www.one18th.com, they might be able to help you better there.

[Rotgut]

I use the 6800 in my Mini-t and think it's great. I wanted the 8000, but thought it would be to hot for a 2wd 1/18th scale. I might get the 8000 for the RC18T because it a 4wd mini. It will probably work better.

[pinolelst]

Just an FYI.I clocked my rc18t today with a bushnell speedster radar gun at 49 mph.mamba 8000 stock pinion and stock spur gear on 11.1 volt lipos (a weary 1500mah 10c discharge pack from one of my planes) .It was just slightly uphill on rough pavement and I'd left my rear wing on.I imagine with a 16 tooth,no wing and smoother surface 60 mph could be hit

[pinolelst]

uploaded a clip of it being clocked at 46 and then 49 mph in case anyones interested
http://www.******.net/view_single.php?medid=45053

[OptimaMan]

pinolelst: That's awesome dude! I used a 1100 mah 11.1 volt pack and it had too much voltage drop for me. Which pack did you use? I found that the Thunder Power 2100 were the closest fit - but they stick out just a couple of mm so I wasn't able to find decent LiPos to fit (that's the real reason I didn't get the RC18T). Did you have to modify the chassis? What's the FDR of a stock RC18T?

[pinolelst]

I used an old thunder power 1500 pack that I've used in my planes and I had to mount it vertically on edge with velcro and some #64 rubber bands stretched over the top between the battery hold down body clips.Sort of MacGyverish but the body lends lateral support and I cartwheeled it once like a frisbee and it never came loose.The stock center brace has a drop to it where the receiver sits and to fit 3 cells in there you'd have to cut out the original as it's part of the diff case assembly and make a CF one to fit, without a drop to it of course .

[studysession]

I am downloading it now. If it is a good/clear video I want to host it on my site. First want to view t forst. Seems like it is taking a long time for me to download.

[pinolelst]

It's a 10mb file and is very clear since it's just a few seconds long.I maybe should've compressed it a little further

[studysession]

Cool - Yeah it should be compressed more for how short it is. ;) Good video.

How do you like the radar gun? I am getting one at the end of January / early February.

[pinolelst]

Can't beat the price as you can find them for about $130 USD

[studysession]

That what I was thinking - I emailed a few RC manufactures and asked when they test their cars what are they using for measuring speed. They pointed me to the exact same gun. Retails for like $200 but on EBay it is like $130 - $140 all day long.

I will be getting one, but have to pay for kids Christmas first. :)

I was impressed how fast that RC18T went. I laughed when it flipped on the divet in the road. The truck is very cool looking. :)

[^j!nx^]

not ot thread jack... but

is there any visual way to tell teh diffrance in the mamba motors?

[pinolelst]

Not that I can tell.If I were to buy another of different kv rating I'd mark the can myself though

[studysession]

NOPE! I think that Castle should mark them somehow - they are not marked at all.

[ducati777]

Seems a little strange doesn't it? I'd expect their orders to be prone with errors if someone mixed up a motor.

[studysession]

Shawn at Castle explained it in another thread somewhere.

[^j!nx^]

only reason i asked was I ordered a compX from tower hobbies, It wasnt shrink wraped or anything. Just seemed kinda wierd to me.

[Rotary Rocket]

I just put a 6800 in my 18T, I would NOT get an 8000 unless you plan on doing "speed" runs all day.

On 2S TP 1320 LiPos with stock gearing this truck was a rocket. Almost unctrollable (specially on dirt). A couple of times it actually wheelied!

After just one 20 minute run, all my tires are toast...this truck is going to be expensive on tires with the Mamba.

Between the Mamba, and TP 2S LiPo the truck is quite a bit lighter and was starting to "bounce" around. I switched to some Silver springs (they are softer than the stock blues), and the truck settled back down nicely.

I don't have an 8000, but it seems even the 6800 is too much for this truck.

[studysession]

Nice pic - :)

[Chase023]

Very Nice 18T

I put a 8000 in a XRAY M18 on 3 cell lipoly cells and man does it fly.. It is so fast, its hard to keep straight.. I can't even pull full throttle hardly at all.
It burns thru foams easily. I already replaced 2 sets of foams due to all the wear and tear. I need to get a radar gun to see how fast this thing runs.

I would post a pic but for some reason won't let me post my pic, only a link.

[glassdoctor]

Nice little truck. It's good to hear some reports that the Mamba has massive power.

Castle has tested the 8000 in a minit on 3s lipos at 60mph. Yet, there have been guys complaining that it's not very fast. I don't know what they are doing, but somethings wrong there. Maybe their batts are junk?

60mph is insane in a mini.

I don't see how even the 4200/5400 mamba could be "slow"... slow describes my completely stock minit!!!! :(

[studysession]

the 4200 and 5400 are still fast. Just the 8000 is even faster. I use my 8000 in a Micro RS4 and love it.

[Rotary Rocket]

Some folks are all about straight line speed, to me that gets boring after the forth or fifth pass...

I can't see how you could actually drive the 8000 (on a track or bashing) while using all its power. Try to barely use the throtle so the car/truck doesn't spin actually takes some of the fun away (my 2 cents). I like to "drive" my cars/trucks. It is nice to build your skills in driving, and sliding a car around corners, etc.

The 6800 on the dirt was uncontrolable! Trying to go up the hill it would just spin like a top. Full throtle starts on asphalt would also result in the truck becoming a top again! The truck would literally become vertical while spining on its longitudinal axis. And of course it totally roasted its tires.

The speed is amazing, nothing broke but you could "hear" parts getting stressed out. I think the diff yokes are the first to go, I can see them getting wear on them.

I had 3 violant crashes (the truck flipped over more than 10-20 times) at high speed, but nothing broke on the truck. :D

Biggest weak link on this truck is the semi exposed spur. Dirt gets in it in EVERY run. The second weak link is the dog bones which pop out (lost one already), but AE has CVDs on the way.

I guess if enough people call AE and complain about the exposed spur they might make some lexan covers for it.

[studysession]

In my Micro RS4 running the 8000 with 8 cells and a 11t pinion - It is not as fast like tunning on 6 cells and a 15t pinion.

If you gear it right, the 8000 motor will be fine and controlable. But if you want a lower RPM - that will be fine and I am sure you will be happy and probably even get longer run times. My experience in the past is the lower kv motors draw less amps and give longer run times.

Even though in this case my main experience with the mamba is the higher 8000kv.

Hope that helps some.

[Signats]

This thread is hilarious, nobody even asked Diesel72 how he was planning to use his rc18t.

Asphalt, carpet, dirt, sand, bash, race, speed runs, indoor at home, parking lot, street................

Let the intended use of the truck be your guide to picking the best motor.

Castle Creations has a Mamba selection guide on their web site, and it is full of excellent real world advice, and not full of testosteone driven sillyness.

http://www.castlecreations.com/documents/MambaSetups.pdf

Now that I got that off my chest my advice is:

Get an 8000 dude you can break your truck way faster with that one. Then you can come back here and tell us how rad it is to see it go up and down the street until it hits a pebble and cartwheels as parts fly off!

This may be fun for a little while but what happens when you want to use your truck for something other than speed runs? Will it be controllable on a slippery rough dirt track? Can you drive it in the living room on a rainy day when the cat is away and the mice want to play?

I don't see the versatility in the higher Kv Mambas, these tiny trucks are so easy to overpower, if you are running it on dirt that isn't really smooth or is slippery/dusty a speed 300 can be too much power, even with 4wd.

If you are planning on racing all the Mamba motors are fast enough even the 4200, just up the voltage (cells) and play with the gearing to get the speed you need. Sometimes slower is faster, suprapimp22 and Rotary Rocket are right on the money.

The plus side with a lower Kv motor is that you will have the versatility to be able to taylor the power so that the truck is under your control, and still be able to make it insanely fast when necessary.

Diesel72 how do you plan on using your rc18t?......

[Chase023]

Don't see the Versatility? Why not use less throttle, I see plenty versatility if you can learn to control your throttle habits. Versatility means capable of doing many things, and I don't see how having a higher kv motor limits that compared to a lowered, unless you behave like an on and off switch on the throttle.

It's almost like saying having a lower horsepower car has alot more versatility than a higher horsepower car. Doesn't really make sense, unless you think of in terms of absolutes, or extremes.

[Rotary Rocket]

Chaseo23, you can't compare hp with BL, apples and oranges.

The lower KV bl motors are more versitalie because you can throw more volts at them to get the desired powered, or gear up and not over heat the motor as much.

The higher KV motors in that regard are not as versitile.

[Chase023]

In that regard, I can see your point.

[pinolelst]

You guys complaining about too much hp are trigger happy.;) in my mind there's no such thing as too much power ,only too much throttle :) (or asking too much of the design)

[SpEEdyBL]

For anyone who's complaining about the 8000 having too much power, why don't you use less cells, like 4 or 5 ni-mhs? They probably wouldn't weigh more than 11.1v lipos and runtime would could be equal or greater. Then the 8000 would be controllable, and you could still have the option of using higher voltage for speed runs.

[glassdoctor]

You guys complaining about too much hp are trigger happy.;) in my mind there's no such thing as too much power ,only too much throttle :) (or asking too much of the design)

Well, I like to go by the same moto. But there's a good reason the best racers in the world don't all run a 7T mod when the race. They pick a motor wind with a wind that will be drivable and give the right powerband they want. I've run a 13X2 in my buggy when I would rather have a 9X1 strapped in for adrenaline... cause it's faster on the track, even if you are Kinwald ;)

My 4wd is another story though... almost can't have too much power. Me likey :D

Speedy that's a good point... but it probably still works better the other way, add voltage to the milder wind. More effecient, etc. But 5 cells would help tame a 8000 for sure. Will the Mamba run well on 4 cells? Cogging etc?