Need help with buggy conversion

Hey guys,

I'm new to this forum, and I've posted a similar thread on another forum, but haven't gotten much input. It seems that you guys here are hog nuts about electric/brushless.

What got me hooked is my current parking lot truck. I'm running an RC10T4 with a Mamba Max 7700 system on 3S Lipo. I haven't seen anything yet (aside from a couple of on road cars) that can even come close to keeping up.

Anyway, I'm going to convert my Sportwerks Turmoil to brushless. I know that I want to use a Mamba Max controller, so that pretty much limits me to 4S or maybe even 5S Lipo. I think I've settled on running two 2S packs in series. I'm thinking either maxamps 4Ah packs or Apogee limn 3800 packs. Haven't settled on this yet. I might go with more capacity, but I don't think I'll go with anything more than 6Ah. I want to keep the weight down, because I intend to race this buggy against the nitros.

My big question is, which motor? L or XL can? I've been told, by a reliable source, that an XL motor will overheat if I run it without enough of a load on it. So...I've been thinking about a 9 or 10L motor (feigao that is). I'll get the same rpms/v as the 7 or 8XL motors, but with much less current draw. I'm going to be running on a track with the longest straight being 160'. I figure that 40 mph might be a good target speed to shoot for. This should keep me competitive with the nitros with the hottest engines.

Oh, am I correct in understanding that I want to keep my motor in the neighborhood of 35,000 rpms at full throttle on my power source? This is what lead me to the choice of either the 9 or 10L.

I'd appreciate any advise.

Thanks.

[Sylvester]

2 2s2p 4000mah maxamps packs will be awesome with the MM, just remember to use a UBEC.

7xl would acutally be ok, and yes, the sweet spot is anything over 28K and under 40K rpms.

[MetalMan]

More input, huh :005:. (My screen name is the same across a few forums) Read the latest post in your thread on URC. You will see some extra information there :027:.

Hey MetalMan, you know what I mean. :) You were the only one that responded to that other thread.

I was hoping that others running an 1/8 scale buggy could enlighten me.

[glassdoctor]

I would recomend a Neu 1512 or 1515 and skip the L/XL altogether. :)

Shoot for a 2000kv motor and IMO it will work pretty well... L,XL,1512,1515, Lehner 1930 or 1940.... any of them.

I'm running a MM, 1512 1900kv on 4s 8000mah and it's a very nice race setup.

glassdoctor,

As much as I would like to move straight to a Neu, finances really won't allow it right now. As it is, I'm going to have to cannibalize my T4 of its MM ESC, just to get the project off of the ground. In fact, I'll likely have to run the setup on 3S Lipo for now, until I can get some 4S packs. I'm still trying to get my house rebuilt after Katrina and can't justify much of an investment in this "toy."

Anyway, I was just online at onlinemetals.com and ordered some 2.5X2.5X3/16 angle aluminum. That should be thick enough for a motor mount. I also ordered some 3/16" plate to make a replacement bracket for the top of my center diff. I'm hoping that his will be the new home for my ESC. I also ordered some 1/8" thick aluminum channel, which I hope will allow me to fashion a couple of battery trays for my lipos. I really want to protect those from damage.

As for the motor, it's looking like it's going to have to be a 10L or 7XL. I'm just not sure of which one. I understand that the XL will have more torque, but it will also draw more current, which I'm thinking will translate into more heat and less runtime. I'm figuring that the buggy is going to weigh less than 10 lbs, so maybe the 10L won't have a problem with this.

I just went out and stripped my buggy (a Sportwerks Turmoil). It isn't the greatest buggy in the world, but I can drive it and my LHS stocks the parts for it. I was considering keeping the mechanical brakes. This should relieve the motor of having to cover the braking duties. I was going to turn the diff backwards and mount the motor forward of the center diff. I was then considering using standoffs to mount a single battery tray perpendicular to the centerline of the chassis. Then I could run a single 4S Lipo pack and I think that it will still fit under the body. I hope. If I was able to do this, then I could utilize the space under the battery tray for the ESC and radio.

So guys, I need some input. Should I go with the L or XL motor? Am I wasting my time trying to keep the mechanical brakes? What about the battery on the tray on standoffs across the back?

Thanks.

[jhautz]

IMO. The L will be enough motor, but the XL will run cooler and have a little more kick to it, so XL gets my vote. I would also say that the XL would be a better chioce to run with the Mamba Max also. I have found that the MM runs better with a 2 pole motor than it does with a 4 pole motor like the Neu. Castle is working on an update for the MM to fix that, but for now I still think the XL will be a better match.

As far as the mechanical brakes go, I think you are wasting your time. Real estate is preciuos on a buggy chassis and your buggy will not be that heavy relative to a MT and I dont hear of people having issues with the motor braking on the 11 lb revos and maxxs. So your 8.5 lb buggy should be no problem.

[glassdoctor]

Hey, the Turmoil is a pretty good buggy... it can hang with the big boys on the track. I know a sponsored guy who kicked some but with one last summer.

On 3s, my gut says go with the 10L.... I don't know if I can explain? While it may not be the perfect setup I think it will run well. The motor is the cheapest part of the project... if it's not right or you kill it, then it's a relatively small loss. And it's not like a 10L won't work... it just might run a little hotter. On 3s though, it should not be as hot... and not as fast. And on 4s, you might just need to find a "happy" gear for it.

My first conversion was an 8L on 10-11 cells. I never ran it much though because that's when my Hacker controller smoked, and by the time I had another controller I had changed the whole car and modified the motor. I took the rotor from the 8L and stuck it in a C50 Hacker can.

[sleebus.jones]

Heh, I just went through all of this with my Hyper 7 conversion. The thread is right here:

http://www.rc-monster.com/forum/showthread.php?t=5302

A gallery of pics of the conversion is here:

http://gallery.rctrack.info/sleebus_jones/Hyper7/

I went with the 10L motor for mine, and the MM controller. I'm running 11/46 right now. With the 3S 2500mAh Apogee pack in there, my speed is right around in the 26 mph range. I have put 12 cells on it, and that puts the speed in the 34 mph range. With both of these combinations, the motor and ESC stay cool. Running 12 cells, the motor gets hotter than the ESC, so I'm going to go up a few teeth to 13/46, which will put me right at 40 mph.

As it is right now, with the 3S in there it'll spin all 4 panthers on concrete with no problem. The 12 cell is pretty silly, but it's heavy (1.6# of batteries) so I'm planning on going LiPo to shave weight and add power. I'm looking at the maxamps 4S 4000mAh pack for that.

Sleeb

[glassdoctor]

I re-read your original post... so I see you will be going 4s it sounds like. I think a 10L is fine for a (relatively) light buggy, esp considering Sleebus's comments.

If you have to you can always put a sink and fan on the motor. But try it and see...

I don't want to sound wishy washy, but I was just trying to buy a motor, but all they have in the 540C is the 9L. What about that motor?

Thanks for the comments guys.

Oh, what sort of runtimes are you guys getting with your setups? I haven't settled on a particular pack configuration yet. I'm looking for that perfect compromise between weight and runtime. I was going to go with 4Ah 2S packs, but now I'm thinking that I might want to go with at least 6Ah 2S2P pakcs. I'd like to be able to run for 20 minutes. My track is going to 15 minute mains and the electrics will be required to make an obligatory pit stop, but I'd rather just make the obligatory stop and just sit there rather than actually HAVE to change batteries.

[glassdoctor]

I have a 540C 9L... I have only run test run it.... never even got a full pack on it. It is very fast on 4s... ran well I thought. It seemed to get hot quicker than my Neu 1512 but it's also a hotter wind.

I'm actually planning to put the 9L into my old buggy... it's currently sitting there but not hooked up yet.

Gear it 10/46 or 11/46 and it will be good. I don't know if 6AH will get you an honest 20 minutes but it should be close... 15 minute main no problem.

The 6000 packs are still pretty light all things considered, and pretty easy to fit in the car.

[sleebus.jones]

I believe that mtucker ran a 540C 9L. I think it got hotter than he wanted, he mounted a fan on it or something if I remember correctly. I've got the 10L with the RCM heatsink/clamp on it and even running 12 cells it just barely gets warm. Granted my gearing isn't that tall (11/46) but I'm quite pleased with the performance.

If the weather holds out, we'll be shooting video this Sunday. It'll probably go up Sunday night or Monday morning. If you want to hold off until then, you'll be able to see some picture proof.

Sleebus

With longer runtimes I couldn't get my 540c 9L not to overheat. Any over about 10 minutes it would overheat that was without fans. I tried gearing, but ultimately it still overheated. I finally gave up on it and got a Neu 1512. That was a huge difference. Ran so much cooler. I think you would have better luck with a 10L. Mike does have the 10L in stock http://www.rc-monster.com/brushlessmotors.php?pg=2 it is the 11th one down.