OK, I'm ready to order a motor. Gotta do it. The conversion is keeping me up at night. Just take a look at the time stamp on this post. :)

I just want to make sure that I have things right. I was considering either the 10L or the 7XL. If I go with the 7XL, I'll be rewarded with cooler temps and longer runtimes, is that right? I'll be running on 4S lipo. BTW, what sort of runtimes do you think I'll get on 4Ah 4S packs?

As I said, I'll be running this in an 1/8 scale buggy. It has a stock 46t spur. What pinion should I get? The longest straight on my track is 160' long and I want to keep up with (preferably pass) a nitro buggy with a Novarossi 21-5 on it. I'm figuring that I should gear for about 40 mph, maybe a tad bit more.

And...does anyone know how to harden a mod 1 pinion. RC Monster is out of the hardened pinions and I can't wait.

Well, I'm not sure if you thought of the current draw of the 7XL.

The 7XL is pretty close in KV to the 10L. However, the problem then is that it is a 95A draw motor. You are running at the ragged edge of the limits of the ESC at that point. Also, a 4Ah pack (assuming it's 20C) ain't gonna feed that motor, because you're looking at 80A continuous out of that pack. To me, the 7XL seems to be asking a lot of the pack and ESC...I may be wrong, I'm sure someone will tell me if I am. :)

I think I'd get the 8XL, which is 83A, pretty darn close to the current capability of the 4Ah pack and definitely easier on the ESC. Personally, I'd prefer a R/C that's slightly slower, but doesn't catch on fire! :005:

Or maybe I'm just screwed in the head with my above thought process? :032:

As for the pinion, search tower for "century motor gear 1.0"



Sleebus

Are you running a single 4S pack or two 4S packs? I ask because on a single 4S pack and a 7XL you can overheat the Lipo pack at towards the end of the run. I know this from experience. I've puffed a couple of doing exactly that. so if your running a single 4S, do like Sleebus says I would go with 10L, 8XL or even 9XL. If you are running two 4S packs I think you might be able to get away with a 7XL, but even so, I would still recommend a 8XL. It is worth it to get the right motor so you don't have to spend a lot of time and money messing around with gearing, fans and ultimately other motors.

For what it's worth, the 8XL and 9XL are closer in kv to the Neu motors many of us are running. 1700-2000kv.

You are correct in saying that the 7XL can draw quite a bit of current, but it will not pull that current all the time. Just think; if a motor pulled even 80A all the time on a 4Ah pack, runtime would only be 3 minutes! Since most of us get runtimes of at least 10 minutes, the current has to be an average of 24A. Of course, there will be peaks when you take off from a standstill or accelerate heavily where motor current will exceed 100A, but all our car ESC (MM included) is made to take those peaks and more provided the duty cycle is relatively short.

Thanks for all of the comments. Of course, I'm confused again. I've done research on this forum and found multiple references to the advantages of running the 7XL, which included better torque, more efficient running, cooler running AND longer runtimes. The longer runtimes is what threw me, because the 7XL is a 7 turn motor and in my experience, 7 turn motors DRAW CURRENT. I was confused, but figured that there must have been something that I just didn't understand, yet. Still, the max current rating issue was still hanging in the back of my mind. I hope that someone can shed some light on this issue.

As for the batteries, a single 4S pack would be the easiest for me. I've also been considering a 4S2P 6Ah pack. A 20C 4S pack should be able to handle 80A constant. The 4S2P pack should be able to handle the current draw easily. I was going to run MaxAmps packs, but they kind of dropped the ball on my last order. It seems that they are running behind on orders and the delivery time is kind of up in the air. I ordered two packs on the 18th and they were just shipped today. Maybe I'm spoiled, but that's too long for me. In fact, I don't even need those packs any longer. OK, I'm going off on a tangent now. Anyway, I might have to get the mount down before I settle on the battery configuration.

As for the gearing on the kv of the motor, I'm still thinking in terms of nitro engines turning at 40,000 rpms. I'm just learning that I don't have to spin an electric motor that fast. Are you guys just running the ultra low kv motors and gearing up?

What kind of speed could I expect from an 8 or 9XL on 4S lipo? Runtime on 4S 4Ah lipo? What about an 11L? Am I going to have heat issues with an 11L? Would an 11L have enough power? I need better acceleration than a nitro buggy with a hot engine (Novarossi 21-5) AND I NEED to be faster. 40 or 45 mph.

Thanks.

Or maybe an 8XL? Aahhhh, I'm about to start tearing my hair out!!!

Sounds to me like the 8XL would be a good choice. Sometimes we tend to over-analyze things. To a great extent, gearing can equalize the differences between a 7XL and 8XL. Everything is a trade-off... and like you said, a motor can't both have longer runtimes and draw more current at the same time, compared to another one.

Based on your need for speed I would say skip the 9XL.

The 7 or 8 is a toss up... I know hte 8 will have to be geared pretty high to get up to 45mph. My 1900kv motor clocks 45mph on when geared 18/46 on 4s packs. It's stupid fast even though the gearing sounds way tall. But there is a limit to how big a pinion you can put on there.

That's why I would leave the 7XL as an option if you really want to do 45mph on 4s.

So... 7 or 8? Both can be stupid fast with the proper pinion.

I would suggest putting a good 40mm fan on the esc and either a fan or heatsink on the motor.

I don't know, but I think that I have a rather unique situation. On the other hand it may not be so unique. I, personally, could be satisfied with a buggy that will run at 30 or 35 mph. In fact that's what I generally had my buggy running when I was running nitro. The standard short track setup for me was 13/46 with a Novarossi P5X. It had plenty of torque (for nitro) and it got to top speed pretty quick. That was fine and dandy when I was running in the B mains. Before I took a break from the hobby (pre-Katrina) I found myself in the A mains more and more. The guys regularly running in the A mains are hog nuts. As short as our track was, I was actually loosing time to other drivers because they had a faster engine. Besides, I'm not going through all of this trouble to wind up with a buggy that is slower than the fastest nitro buggy out there. When I was running nitro, it was not unusual for me to burn through a gallon of fuel, non stop. A testament to the reliability of the Novarossi engines. I want to be able to run as long with my electric AND be quicker and faster. What that translates to is that I don't want to have to deal with heat issues. If that is something that I won't be able to get around, then I'm going to abandon the whole thing.

I'm going to go ahead and get the 7XL. It's probably going to be the best choice, but from what I understand, I'll have to run something other than a 4S1P pack. I'll have to go to 4S2P to be able to keep up with the current demands.

OK, assuming that I go with the 7XL, do you guys have any recommendations for pinions to get to start at a speed of about 35.

BTW, will going with something like a Lehner 1930 or 1940 really make that much of a difference. I want to stick with a two pole motor for now. The only thing I've settled on is that I WILL be running a MM controller.

glassdoctor,

Is your 1900 kv motor a feigao, or is it a better motor? Do you have problems with heat?

It's the Neu 1512. It will run pretty much all day long without too much heat issue. I did get it too hot once but normally it would run all day under 180, and if there is some air getting to it I don't think it would get much over 160. That's not bad for long races.

I also have a Neu 1515 1700kv in a Jammin truggy, geared for about 30-35 mph with a single fan blowing on the motor and esc. It will run on my small track nonstop and never go over 160's. I have run it for well over 30 minutes.... it has a 12ah 4s pack.

I would really recomend a high end motor like a Neu based on what you say you want, to keep things running as cool as possible. But there does seem to be a little cogging issue with the MM/Neu combos right now. I hope this can be resolved so I can recomend it without a doubt.

I don't know what other motors are like... Pletty or Lehner I assume will run cooler like the Neu. Rotary Rocket is running a Pletty/MM combo and reports no heat, no cogging.

I would guess about a 14 would be a good gear for the 7XL, but you might want to check BrianG's speed calculator and see what the #'s say.

Sorry... all this discussion still doesn't clear things up really does it?

The 7XL is relatively cheap... so if it burns up then you will know for sure. ;)

I'm tired of thinking about all of this. I need this thing to go fast. It was pretty fast as a nitro, and I need it to be faster. What would be the point if it wasn't faster? I'm thinking that I'm going to go with a 9L. I could be wrong, but common sense is telling me that the 7XL is too much motor. The lower wind motor is going to give me less runtime and less speed. The 9L on 4S will spin at about the same rpms as my nitro and if it will run cool with a 13t pinion, then that would put me at a good starting point. What I mean by cool is within spec.

If it overheats on the above setup and I can't run it the way I want to, I'll just go back to nitro.

There's one thing that I don't understand about these brushless motors. That is their ability to generate torque. Does the torque go up as you reduce the number of winds, or is the ability to generate torque a constant among a line of motors? I mean, do all L can motors generate the same amount of torque with the number of winds affecting only the number of rpms/v?

The 7XL isn't too much motor, it's controllable power in a buggy. I used it on 14 cells in my Mugen, and pretty much loved that setup. On one hand, you say that you want to go 30-35 mph just like your nitro buggy, while in the last post you say' i need it to be faster' i don't think that speed is the thing you need. it's acceleration that's the most important. (so traction and torque are important) a 50 mph truck can loose a race from a 10mph truck, if you catch my drift..

The 8XL will give you more runtimes, and can be geared a tad higher than the 7XL while the 7XL will drain the batteries quicker.

The 7XL is an impressive motor, it runs like crazy, and can't be beaten by it's cheap price. If it's geared properly it won't run too hot. and if you want to play it safe, get a rc-monster motor-clamp/heatsink. (which is a wise thing to buy anyway)

Thanks for all of the advise guys. I think that something about the torque that these motors generate has dawned on me and I think I have a better understanding of what I need.

The only thing that's keeping me from going with the 7XL is the low turn of the motor. I really want the runtime. Again, my choices boil down to either the 7XL or the 10L.

I would just jump on the 7XL, but the 10L is still lurking in my mind. I keep coming back to the fact that I'm going to be running this in an eight pound buggy. Not a 10+ pound monster truck. I'm wondering if I really need the torque of the XL motor. I really hate to keep going back and forth with this, but I'm really limited on battery. I made a motor mount tonight. I used an Emaxx mount. Not the stock one, but the optional one. It's about 4mm thick and is OK. It looks nice. I just ordered some 7075 aluminum plate cut to 2.25x3" to make a better mount. I got 1/4" and 3/16" thickness to see which works best. Anyway, after I set everything up, it appears that I won't be able to go with a dual battery setup, because if I do, I won't be able to really protect the batts from the bumps and bruises that come with racing. It looks like I'll have to go with a single 4S pack. Due to weight, I'm figuring it's either going to have to be a 4S 8Ah pack or a 4S2P 6Ah pack. The limited capacity has me worried about runtime.

Has anyone actually run a 10L in a buggy? I'd like to know how it went.

There is no way to know definitively if a given setup will work ok, be fast enough, or be perfect, etc... it may come down to how you drive and what the track is like. The same setup might work great in one situation but overheat in another with the exact same car.

Let me add to the total confusion :) I have not run a 10L and I only testran the 9L. What I have run the most is a frankenstein motor... that is part Hacker and part Feigao. It's a 12L but it may not run like a normal 12L, but I have no idea. It seems to be faster than it should be... in fact the 9L felt pretty similar when I ran it.

Anyway, I raced the "12L" hybrid and it was fast at 11/46... and easily thte fastest car on the track at 13/46. It was retarded fast as I was told a couple of times. I think the MM could handle this motor esp if I put a fan on the MM. But this motor would thermal a MGM 120 and Mtroniks Truck, which I ran with the built-in bec. That could have been the problem with the Mtroniks.

Hope this helps.... I guess if you keep the buggy as light as possible I can understand going with the L over the XL. You should be able to get it under 7.5lbs with a 4000 pack. Both my cars are right at 8 lbs.. the Kyosho on 6000mah and the 8ight on 8000mah.