5 cell + mamba 25 in a tenth scale for racing?

[BP-Revo]

Yea...Novak has an ESC capable of like 700amps for a 1/10 scale car...(its a brushed ESC) but I think that proves enough as to how much power can be drawn...

I am not saying this will work ,but I'm sure it is not that far of. Novak makes oversize speedos so that resistence is extremely low for that little edge in spec racing classes. Not many 10th scale batts I know of can support 700amps for any length of time. Most of novaks stuff is for 6 round cells, higher voltage setups only reguire a fraction of the amps.

ignoring eficiancey and other small variables brushless motors tend to follow some basic rules.

- more kv = less in.oz./amp torque (per amp)
- more kv in same size motor can handle more amps
- motors reach max eficiency at a voltage that puts them near there rpm limit
- smaller diameter motors can handle more rpm
- small motors and large motors make equal torque per amp if the kv are equal, however the larger motors tend to handle more amps


my MM 5700 makes aprox. .24 in.oz. of torque per amp I average less than 34 amp racing.

the 2700 kv small motor makes .5 in.oz./amp. So less than half the amps are required to make the same amount of torque

I would be running the 2700 on 2.5 times the voltage (6-cell nimh to 5 cell lipo). so the 2700 would be spinning the same rpm as a 6750 rpm motor on 2s = I can gear down a couple more teeth = even less amps required

new systeme would make the car weigh 20% less = 20% less amps needed.

I know this is pushing the limits, gearing for a particular track will be critical, and maybe not even worth it, but it is not that far off. Any constructive criticism is welcome, I am asking for it. Eagle tree graphs of hot 18TH scale cars or race condition 10th scales with a breif description of running conditions would be extremely usefull. Serums #'s for his monster are appriciated; there is a huge difference between the weight of it and my little car, but still worth considering. Shooting me down because Novak rated a speedo at 700 amps is not very constructive.

jhautz thanks for the positive response I'd love to see more info on that xxx4 setup

I'd like to hear more opinions on wether or not higher voltage feels smoother, that is a big part of the reson for wanting this setup. I already have an M.M. running in the car. 2 or 3s M.M. and 400 size motor would be almost as light as 25 (with heat sink, ubec, and equal watt/hr 5s) and really safe and easy.
My only real experience between voltages has been 2s and 3s with a 4100, 6800, 8000 in an 18t. Lower kv motors seem smoother and higher voltage seems crisper. Maybe the 2s bat. was just a little weak for the higher kv or taller gearing, want others opinions.

[jhautz]

Originally Posted by Cheater

jhautz thanks for the positive response I'd love to see more info on that xxx4 setup

Im on the road for work this week. I'll see what i can dig up when I get home this weekend. No gauranties, its been a while, but I. Do remember having a picture and saw it run with my own eyes.

[BP-Revo]

Originally Posted by Cheater

Shooting me down because Novak rated a speedo at 700 amps is not very constructive.

I wasn't "shooting you down," just simply using a sledge hammer. :018: Just kidding lol :005:

I was just agreeing with the post before my (Serum's) that stated 25amps is too little for a 1/10 scale...

I was just pointing out the vastly high amp rating on a popular brand of 1/10 scale speeds controls (even though it is brushed).

However, it seems like you have given this considerable thought and have calculated it down...so I guess it's worth a try. A mamba ESC is only like 80 bucks in the end, so its not exactly a wallet buster, but its not something I would recommend.

I would like to point out one thing. On the CC website, I read somewhere that using the M25 ESC on 3S Lipo with the 8000kv motor voids the warranty...while with the MM it says you are not supposed to use 3S on the 7700kv because the RPM would be too high for the motor, but the ESC is fine. So, I'm not sure you can overtax a M25 like you can a MM...

It seems to me an MM has much more research put into it than the M25, because (supposedly, from what I have heard) the M25 coggs a bit at startup with the 8000kv motor, but the MM doesn't cog at all with any motor...

Well, whether you decide to do it or not, good luck...

*cocks gun...takes aim* lol...couldn't resist...

found something today http://www.megamotorusa.com/
acn 22/10/2E & 22/10/5 both come with mamba-25 for
10th & 12th scale.


here are some more novak #s
- 4300 super sport = 175 watt motor, 225 controler this system wins alot on our tracks. It is not the fastest, but fast enough and easy to drive
-novak has a brushed 1620 amp 6 cell nimh controller (the gtb)

[Serum]

Still not a setup i will advice you, but i am not stopping you...

on 5S the 2400 rpm/v motor will fry that esc at the first run..

[danverz]

Hi,
I agree with Serum. I won't use a mamba 25 on a 1/10 car.
In my past experience I saw 100A on a 1/10 car with a 2S lipo.
I also like to say the Quark 33 is able to be pushed to 50 and has surely more
current capabilities than the mamba one.
Yes I know you want to use an HV setup, and this will keep Amperes lower,
anyway I do not think this is a good choice.

Ciao,
Daniele

[jhautz]

Here are pictures of that xxx4-G+ with the Quark33 and the neu. I found in an old email that it was an Neu 1105. Thats a really small motor. He ran a 2100mah Lipo pack. Basically a 1/18th setup, but the xxx4-G+ is so light because its all graphite that it weighs the same as a Losi Mini LST which runs fine on a heavy duty 1/18th setup. He claimes his buggy was running 1lb lighter than his buddies xxx4 with a Novak GTB 4.5 and 6cell and had better acceleration. Also claimed a 30 minute run time, which I have a hard time believing on only 2100mah pack.





Don't forget I think this worked for him cuz the 1/10 he was running was so light. If you try this in a rustler or something you will likely not have the same sucess. Also notice the BIG fan over the esc in the pictures. :eek:


Why not try the Quark 33A instead of the mamba25. The Quark is at least rated for 5s Lipo and has a heatsink which I think will at least give it a chance.
http://www.quarkbrushless.com/pro_procarcontrol_33a.htm

might want to give this a quick read through...

http://forums.radiocontrolzone.com/s...+stadium+truck

Bye:018:

thanks guys for digging up the pics, and link; very inspiring!

Doing some testing of my own also. Mamba 25 does run on 5s:027: ! Current test rig is an emaxx with a 980KV Himaxx 2808 1.83 oz. 8amp. cont 12amp burst. gearing 66/12 takes of well in 2cnd gear. gearing 66/16 2cnd gear cogs terrible from dead stop, but If I take of in first just to get rolling second will pull strong from a crawl even on a hill. Testing was a gradual 6 nimh lowest gearing, 3s, 12 gp 3300, gp's + taller gearing, 5s in first, and finaly 5s in second. 5s with 66/16 cogs some even in 1st when the battery is fresh of charge:002: . With 66/12 is very smooth, but packs were not fresh, need to top of packs and test again. Top speed with 66/16 should have been around 10 mph. Motor always stays cool, speedo does good even in grass. the only times the speedo heats up are, cogging, pulling up against side of house and lighting up tires on brushed concrete (full throttle 1st gear temp gun aimed at speedo the whole time took a few seconds to come to 180, then overshot just over 200f still ok) , and climbing the hill at very low throttle inputs (full throttle repeated passes are fine even in second+tall gearing), but two crawling speed passes up the hill in second heat it up 180+. All of this testing was done with the factory shrink wrap still covering the speedo, temps recover very quickly from these situations while driving normal. I plan to put a heat sink on it if it goes beyond the testing phase. 5s definently seems hotter than 4, but air has warmed up alot to. Also I believe higher voltage brings in more amps, and when geared so as that 5s top speed matches 4s top speed amps should be close to equal will have to test more latter. 5s with lower gearing feels very smooth. tuck weighs 7lb. 7oz. with old 10c 5s 1800 + reciever pack. I think it could push 20 mph in a light 10th scale if I had enough gear. This is not the motor I intend on running; it's the only motor I have that will take 5s, just trying to get a feel.

sorry all. the 2808 was my old motor upgraded last summer to a 2812 850 kv 2.3 oz. 160 watt 28 x 29mm. 4-11amp 14amp max 15 sec. 1.6 in.oz./amp. This throws the #s of some. speed was calculated mathmaticaly @ 12mph for the 980 taking into acount a fair amount of sag for the older pack, so 10 still isn't far of. With a fresh pack 66/16 gear I can't run fast enough to keep up while holding the remote, if my hands were free I could.

***Also found another possible motor looking for opinions e-flight six-series 28x36mm 2.9 oz. 2000kv 6-pole 26amp 32amp burst 15 seconds. only listed for 3s, but 2700kv version is listed for 3s also. the 2000 on 4s would be less rpm than 2700 3s.

considering going 4s anyway 5s works, temps ok so far, but when something goes wrong (bad cog, part throttle abuse whatever it heats fast). Also I read the thread about finsters wife with the M.M. 5s failure. Also looking at flight power batts. 2170 is the smallest pack I found with 25-50c rating 4s is almost 8oz. 5s would be to much weight. According to the graphs this cell averages almost .2 volts per cell higher than there 20-30c packs. 3.5x4=14 3.3x5=16.5 only giving up 2/3's of a cell worth of voltage, and no longer pushing luck voltage wise. Thanks to Jhautz and Cemetery gates for showing me it can be acomplished on only 2 or 3s. 4s should be enough to make it exciting on our tracks.

Please give thoughts on the Six-series motor. I know the 6pole is like running a 2 pole with 3 times the kv from the speedos stand-point, but right now I'm running an out-runner (not sure how many poles, but alot, on 5s) also have seen more than one c.m.8000kv on 3s so the mm25 can keep up.

mamba 25 done. Did a 5s test with lower gearing, and freshly charged batts. Cogging not much of an issue with lower gearing, couple other quick checks ok, and staight to the hill for part throttle testing. I had already performed same test repeatedly with half charged 5s and much taller gearing. This time I expected temps to drop (lower gearing), I didn't even start up the hill and puff. It seems the fresh pack put voltage a little to high.

After this I got to talk to a very knowledgeable brushless airplane guy. Here are a few thoughts he had-
#1 - at full throttle fets don't work nearly as hard as at part throttle (what I saw in testing proved this even @ lower voltages, but went critical on higher)
#2 - out-runners are not the best motors to try to over power; they suffer iron saturation and act almost like a dead short when overloaded
#3 - cheap batts cause ripple currents ( a little spike getting through the cap would easily kill the fets., but the higher nominal voltage good batts would provide would not be good either on 5s)

So. if I want to continue I need to go with a top notch motor (Neu or mega), best quality 4s pack, and gear to use full throttle as much as possible

[jhautz]

I can already hear the ''I told you so from Serum'' :005:

But just cuz this setup failed I don't think the idea is a total failure. I actually think that you could make a small setup like this work with, as you said, '' a top quality motor'', but also try the Quark 33. It is actually rated for 5s and has a heat sink built in.