Managed to thermal my Mamba Max 6900

[rccardude04]

Yeah, I don't know how either. It's previously ran about 160-170 degrees, and now my ESC thermals and the motor is up around 225. Too hot. Way too hot. I changed to the new style XL5/VXL slipper clutch and the darn thing gets hot. I've changed nothing else but the gear cover. Yes the mesh is good.
Any thoughts? I guess the spur is a different size.. 86 instead of 87. But big deal, right? Maybe I need to gear down more...
-Eric

[SS Pede]

Might want to try gearing down. I hear you sometimes need to do that with the higher kV Mambas on off-road vehicles. I don't know why suddenly you're having problems though, when you didn't before.

[rccardude04]

Yeah, I don't know either. Especially since it was a little cooler today than last time I ran it. I almost got the 4600 for this thing instead of the 6900 but we had the 6900 in stock more recently than the 4600 and I know how castle tends to change their ESCs slightly every once in a while so I got the 6900. I wonder if I shouldn't try to find a slower motor. The thing will wheelie whenever you want it to. Goes faster than the aerodynamics of the truck will allow. It's silly!
-Eric

[GSMnow]

What size pinion are you running? What spur exactly? What is the internal trans ratio? How tall are your tires?

DO the math and figure out the theoretical speed. Assuming 6 cell NiXx pack, you have about 7 volts once it winds out (5 to 6 volts while accelerating) so you have a possible top RPM around 6900 x 7 = 48,000 rpm give or take. On just 6 cells, gear it for about 40 mph for open area bashing and on a track, gear it so you can go full throttle and top it out on the fastest long straight. I am running just a 5700 on 6 cells and I run a 15 to 86 with a 2.55 trans and 4 inch tires for a theoretical speed of
7 x 5700 = 39,900 rpm topped out (no load on motor actually does go over 44,000)
39,900 / 14.62 final drive ratio (86 / 15 x 2.55) = 2,729 wheel rpm
2,729 x 12.56 (inches per tire revolution 4 x pi) = 34,295 inches per minute
34,295 / 1,056 (MPH / inches per minute) = 32.5 mph quite fast on a tight track with a 120 foot straight.

I have had it geared as high as 45 mph, and YES it still pulls wheelies, but it runs much hotter, much shorter run time, and much harder to drive on track. Gearing it slower was a big win win win. It runs for 12 to 14 minutes on a pack of IB4200's in full race conditions on a medium tight track. I can use full trigger without losing it on the front straight, and it will go from stopped to clearing the triple jump in just 8 feet of track. Adjust your slipper for the degree of wheelies you like. I run mine so it just Go can't quite lift the front tires from a stop, but from a 20 mph roll it does. Go figure?

[GSMnow]

What size pinion are you running? What spur exactly? What is the internal trans ratio? How tall are your tires?

DO the math and figure out the theoretical speed. Assuming 6 cell NiXx pack, you have about 7 volts once it winds out (5 to 6 volts while accelerating) so you have a possible top RPM around 6900 x 7 = 48,000 rpm give or take. On just 6 cells, gear it for about 40 mph for open area bashing and on a track, gear it so you can go full throttle and top it out on the fastest long straight. I am running just a 5700 on 6 cells and I run a 15 to 86 with a 2.55 trans and 4 inch tires for a theoretical speed of
7 x 5700 = 39,900 rpm topped out (no load on motor actually does go over 44,000)
39,900 / 14.62 final drive ratio (86 / 15 x 2.55) = 2,729 wheel rpm
2,729 x 12.56 (inches per tire revolution 4 x pi) = 34,295 inches per minute
34,295 / 1,056 (MPH / inches per minute) = 32.5 mph quite fast on a tight track with a 120 foot straight.

I have had it geared as high as 45 mph, and YES it still pulls wheelies, but it runs much hotter, much shorter run time, and much harder to drive on track. Gearing it slower was a big win win win. It runs for 12 to 14 minutes on a pack of IB4200's in full race conditions on a medium tight track. I can use full trigger without losing it on the front straight, and it will go from stopped to clearing the triple jump in just 8 feet of track. Adjust your slipper for the degree of wheelies you like. I run mine so it just Go can't quite lift the front tires from a stop, but from a 20 mph roll it does. Go figure?

[rccardude04]

Geared 20/86, Masher 2k's and I have no idea what the traxxas electric transmission ratio is... I'll look it up.
I've heard from a couple people, and seen from experience that undergearing a brushless can cause problems also. I have not had trouble with this thing overheating before. I was able to put about 4600mAh back into the pack after the run, out of 4900, so it was almost an entire run.

I guess I didn't do very well with the setup info. I'm usually better about that :D

Mamba Max 6900
TrakPower 4900
Geared 20/86 with Masher 2k tires
Trans. ratio 2.72
I have the slipper loose enough to slip but not like it was. The only thing I changed from the last runs was the slipper. I replaced the topshaft and put the "revo" slipper on there like the newer XL5/VXL trucks come with (mine is old as hell). The old slipper would literally slip to the point of no wheelies at the beginning of the run, then heat up to about 140F before it'd hook up and let me wheelie. And I experienced the same thing you did as far as the thing not wheelying from a standstill, but it would after about a 10-20 roll.
I'm going to probably pick up a 15-17 tooth pinion tomorrow to see what happens. I have a feeling I'm just over geared and was just not being hard enough on it till this pack to notice it. I never really let the thing top out anyway so it's not like I care much about the top speed. I think I should have gotten the 4600. LOL.
-Eric

[rccardude04]

LOL. After doing your calculation from above, I get 65.8mph.
I might be overgeared.
-Eric

[rccardude04]

Wow! According to my calculations *fixes glasses,* I should be running a 12-13 tooth pinion. However, I don't want to go that low because... WOW. lol. I'm going to try a 16 and see where I get. I should have one laying around somewhere. I'll be sure to report how it goes if I ever get to drive it. lol.
Thanks!
-Eric

[chilledoutuk]

just out of interest what fdr were you running?

[rccardude04]

fdr?
I found a 17t off my old 19 turn motor. I'm going to try that. It still puts my theoretical top speed over 50mph, but it's a start.
I also found a ferrite ring that I put on my ESC signal lead. Hopefully that'll cut down on my radio interference as well. I'm sure the lower current draw will help also. :)
-Eric

[GSMnow]

He said 20 to 86 with a 2.72 trans and 5 inch tall mashers 2000's
OUCH!!!!
Looks like he did the math right.

Here is what I get
4.3 x 2.72 = 11.7 FDR
LiPO power so 7 volts EASY under load, probably close to 7.4 on a full charge. 48,300 / 11.7 = 4,129 wheel rpm at 15.7 inches per rev = 64,858 inches per minute / 1056 = 61.4 mph WOW!!!! those mashers probably balloon like mad at that speed.

I think the smallest 48 pitch pinion you can get is 14 teeth, try it.
That is still 43 mph top out, DAMN

[GSMnow]

Oh, undergearing is basically a non issue. I have run my Mamba Max 5700 motor flat out with NO LOAD for a fair amount of time and it just gets barely warm at medium timing. Set yours to lowest timing with that gearing. The only issue with unloaded motors is when the KV x volts works out to beyond safe rpm. There is a point where the motor runs warmer than the ESC, but who cares, it is not hurting it as it is still cvooler than a loaded motor, UNLESS the rpm is just too high in which case you are running too much voltage for the motor. Like the wild guys running 3S LiPo on a MM 7700.

[rccardude04]

Oh, Final drive ratio. Got'cha.
I used 7.3v, 5.0" tire diameter. The tires grow and I assume none. so that's going to be off a bit. Gives 64mph.
You can get a 12t pinion, but it gets silly. I think I might be best off with about a 15t and the lowest timing setting once again. I went ahead and set it back to normal to see what happens. It's going to need to go farther though from the sound of it.
Think this looks like too much motor?
The 4600, at 7.3v and the same tire (5.0inch), with 20/86 = 42.71mph. That'd give me some gearing room. No wonder Traxxas sells a 3500kV motor. It's about perfect. Puts it at 32mph with a 20t pinion. I think those things come with a 23 though. That puts it around 37mph. Sounds about right.
I might try to find a VERY high quality motor (hacker, lehner, etc. around or under 5000kV. How are the Cyclon car outrunners?
http://www.horizonhobby.com/Products/Default.aspx?ProdID=CYLCAR4000 It'd be cool just for the outrunner part. Durability would concern me though.
-Eric

[GSMnow]

That cyclon looks like a very nice motopr. It certainly will make the torque you are looking for with those big Masher 2000's. The only issue might be starting it smooth with the Mamba Max ESC. I have seen various posts where some say they run fine to un-driveable with multi pole / outrunner / lamination stator motors etc. I guess the degree of success has to do with the particular setup and the "pickiness" of the driver. I have not tried other motors on mine yet. I keep eyeing a Novak SS4300 but I know there are issues that Castle is trying to work out with Novak motors specifically, so I then looked to the Orion/Peak motors but they are just like the Novaks internally (Built to the goofy ROA rules) but again some say they work other say forget it. And outrunners are inside out Novaks with multi poles.

For reduced torque, easier driving on tight tracks I am looking at a 380 sized airplane motor, 380/10 turn 4040KV, but it is only rated at 18 amps cont. with no burst rating. My 4200 mah packs last 12 minutes so I am averaging about 21 amps. And with the smaller 380 can I should be able to heat sink it better. Best part, the motor is $40

Just doing a quick search, I came up with this
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXLWZ7&P=6
540 sized, but with a 5mm shaft. 3300KV 45 amps const. 100 amp surge. Rated to 4S LiPo where it will make 833 watts OVER 1HP!!!
On 2S LiPo it is 7.4 x 45 = 333 watts constant, and 700 watts peak, WOW!!
That is a lot of motor for $70

[rccardude04]

Trust me, I have no problem with torque. The thing has WAY too much already.
That motor looks pretty insane but I'm trying to go for less horsepower here. LOL.
Somebody also told me to look at the Hacker C40-10T. Do you happen to know anywhere to find the specs of their motors? They just rate them in turns and tell you they're expensive, but don't give ANYTHING technical. What about an equivalent Lehner or anything else?
If all else fails, I could just pick up the 4600 and call it good. But that's no fun! :D
-Eric

[GSMnow]

I am looking into Great Planes Ammo series motors. They have a few very nice 380 sized motors that might work out for a car to make less torque than the Mamba Max CM36's. A 10 turn 380 comes out ro about 4000 KV and will take about 40 amps cont. 70 amp surge.

Check out this one
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXLWY5&P=FR
Here is the whole page to choose from
http://www2.towerhobbies.com/cgi-bin/WTI0094p?&N=N&P=FR&F=%20%20GPMG4565&L=GPMG5135&C=GHGGPM
Keep browsing around there and the value of some of these motors is amazing. The 36mm motors (about 540 sized) have some serious power numbers.

[rccardude04]

What size are the 540s anyway? 36mm with 1/8 shaft is what would be the most useful if I'm not mistaken. Too bad 5mm shaft pinions are a little hard to find. That Ammo motor would be awesome.
-Eric

[rccardude04]

Another random thought here... The smaller pinion, should also help keep the thing from cogging at partial throttle, no? It tends to do it sometimes a little more than I would expect. If you really punch it, of course it goes. But I wonder if the smaller pinion won't make it easier for the thing to start spinning.
-Eric

[chilledoutuk]

what you want is a plettenberg extreme. there not cheap but then nothing worth having is.

[rccardude04]

I just put her down to 17/86 - speed calculator says 51.2. It still gets about 170 on the motor but still only about half a pack or less. It's dark and I have no lights. I bought a 13t pinion but the darn thing is too small and it won't mesh. Looks like the smallest I can go is 14 with the 86 which puts my mph right above 40. I'm going to turn down the timing back to lowest and see what it does at work tomorrow. Might get lucky and this will work (17/86).
-Eric

[ta_man]

If you change back to the original style Traxxas slipper, you can use spurs meant for Associated pan cars and get as large as 96T spur:

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXS466&P=7

Whether it fits your gear cover or not is a separate issue. Before you say it is impossible. I'll tell you I have done just this, though with the equivalent Duratrax brand spur gear.

[rccardude04]

Well, I would go back to the stock setup but I switched because it wasn't possible to tighten the slipper enough. A friend of mine had the same problem so I went to the new style and it works just fine. I can actually go to a 90t spur with this setup but I don't think it's going to fit under my purdy blue rpm cover. Plus, that'd put me slightly undergeared for bashing. If I was racing the thing I would do it in a heartbeat.
Good thought though. I also thought about going to 32p for durability reasons before I switched the slipper. I think I could still but I could definitely not run the cover.
-Eric

[GSMnow]

14 to 86 will get you in the ball park. Still very high for the Masher tires, but at least the motor should get out of it's own way. You really do have too high of a KV for your application. If Traxxas does make a bigger spur for your slipper, go for it.

On another note, you may have overheated the rotor in the motor enough to weaken the magnet a tick. This will make it run hotter as you will need more current to make the same torque. Just like the bonded vs sintered rotors in the Novaks. I weakened my 5700 a little and it shows as more heat, but it also made it a little easier to drive with the softer torque curve, but the change was not really enough. A weakened rotor also makes for a higher KV. You can measure it with an accerate volt meter and frequency counter (or tachometer). My 5700 measures almost 5800 now, not much of a change, but it shows.

[rccardude04]

Yeah I know what heat can/does do to magnets. Traxxas sells bigger spurs but they won't fit under the gear cover. I'm going with 15/86. The 17t didn't overheat in the parking lot after about 3/4 pack of hard running (well, as hard as you can drive a stampede in a parking lot). In fact, I could hold my finger on the motor/esc both for a few seconds before going "alright that's getting uncomfortable." I think this 15/86 combo and the low timing will do the trick. If not, I'll be getting a 4600 probably. Longer runtime that way anywho. :D
-Eric

[rccardude04]

The car runs even better with the 15t and low motor timing, and that's as far as I am going to be able to go with it. I'd say I'm happy, at least for now.
My other problem is still glitching. The stupid thing is still having radio problems. I'm using my Futaba 3PJS with the PCM receiver, which has NEVER glitched in anything before, and now I'm getting about 50-100' before I have problems with the thing locking out (holds throttle/steering positions and runs into cars) and general loss of signal (failsafe mode). I have the wires twisted TIGHTLY on the battery, esc, and motor leads. I have a Ferrite ring on the esc receiver lead placed as close to the receiver as possible. I even bought one of those spektrum capacitors thinking it might be a low BEC voltage, but none of those have really seemed to help. The receiver on a Stampede is right between the steering servo and the battery. The battery leads come out right behind the receiver and I am also running a pretty burly digital steering servo (94758). Any other ideas? I have never had radio trouble with this setup before now.
-Eric

[SS Pede]

I was able to eliminate most of the glitching with my Stampede by moving the antenna forward. I put a new hole in the body at the base of the windshield, and mounted the antenna tube to the front body post (well, not the post itself but the brace that the posts stick up off of).

Maybe it's just me, but I kind of feel like the Stampede's chassis is laid out in such a way that it makes glitching more likely. I know a fairly significant number of people (myself included) had issues with their Novak SS5800 glitching in their Stampedes, even though it never seemed to be such a big problem in other vehicles.

[rccardude04]

Unfortunately, I already got the antenna mounted towards the front.
I might have to find another vehicle for the brushless if this continues like it is and just put a good brushed setup in the pede. It's getting ridiculous.
-Eric

[rccardude04]

I drove a stock VXL with the Traxxas radio and the 11.1v 5000 maxamps lipo. It doesn't glitch.
Figure that out.
-Eric

[Ball Racing]

I have the vlx stampede, but have a mm7700 motor in in with stock tires, and 14 90 gearing, and a orion lipo 7.4 pack.

Run it in the low cut grass until almost the pack is gone, and the motor is about 175, and speed control has been as high as 185, and battery 129 degrees.

Stupid fast, uncrontolable, really no fun..

[rccardude04]

Yeah, the 15 tooth pinion works awesome. Tonight, no overheating after almost a full pack. Actually, I could hold my fingers on it for a couple seconds with no problem.
The glitching problem *appears* to be gone now that I've turned the battery around and slotted the RPM ESC mount. We'll see tomorrow.
-Eric