MM/Feigao cogging
 

I've been running my truggy since I converted it and I've been having a problem with stripping spurs. At first I thought that it was due to the chassis flex; although I didn't know how this could be since my motor mount is mounted to the center diff mount.

Today, while I was playing around with the Muggy with my son driving his Monster GT (brushless of course), I nailed the throttle from a dead stop and it cogged so violently that it stripped the spur gear. I've never had that happen before, but then again, I've never nailed it from a dead stop either. I'm running with no punch control, lowest timing, and high start power.

I also have to say that I'm running way over geared. I think I'm over geared anyway. I still have the stock Muggy tires on it running 14/46 gearing, which is what I was running in my buggy, so I figure I must be over geared.

Anyway, has anyone else experienced anything like this. Could it be due to the over gearing? That's the only thing that I can figure because when I stipped the other spurs, the truck was too far away to see or hear if it was cogging.

I haven't heard anyone having any trouble with 2-pole motors of any kind. Overgearing might put too much of a load on the motor and the ESC can't get the motor turning fast enough to get a rotor position. I'd also crank up the punch control and reduce start power. Even doing this, I haven't seen noticeable decrease in performance. Actually, it might help it run better since it's not working so hard. What motor (wind) was this BTW?

I get a cog every once in a while but nothing that is violent

I've never had this problem before with the MM. I don't have any problems at all with my Monster GT conversion, but that is geared very conservatively.

I suspect that the gear is just way too tall on the Muggy, so I'll have to try out a smaller pinions, when they get there.

Until then, I'd try reducing the start power and turn down the punch (increase punch control) as it will be easier on the ESC...

Brian,

To make matters worse, I just got back from my LHS and all they had was a 44T spur. My order from Mike won't be in for another few days. I'm gonna run the punch control at 100%, timing on lowest, with the lowest start power setting and see what that does.

Well, at least all those adjustments will let you know if you're on the right track. Changing the spur will only make it better. A side benefit to changing those settings is that you'll probably have more runtime since the batts aren't being forced to pump out so much current in bursts.

I tried all of those settings and they did help. What I'd really like to know, though, is whether over gearing can/will cause cogging? I'm asking because I didn't have any such trouble with my buggy conversion, but have had this trouble with the Muggy. All of my connections are now hard wired, except the deans going to the battery. I'm wondering if I have a cold joint someplace, but if I did, wouldn't I be having the problem all of the time rather than intermittently?

I liked all of the lowered settings, but I think that there is too much punch control. I'm going to work my way down with it, until I get to a happy medium. I'm hoping that my order of pinions gets here tomorrow. I have a 10, 12, and 14 on the way. Should I have gotten some of the odd sizes too. I just figured that going every other step should be good. Sorry for all of the elementary questions, but I'm really new to trucks and don't want to assume anything.

Overgearing will definitely give you more cogging! On all ESCs, not just the MM.
Back in the BK Warrior days I used to judge my gearing by the amount of cogg I'd get at super low speeds :)

While the Muggy is called a MT, it is really built like a truggy. Most MT have the spur/pinion, and tranny, and the diff to reduce ratios. From the pics of the Muggy, there is no tranny, so you lose whatever ratio there. Then, the tires are kinda big. The diameter of the tires actually has a lot to do with gearing. So basically, you have a relatively heavy truck that is geared tall. If you have a high kv motor (like a 7xl or equivalent) it may be trying to do too much with too little gear reduction. The MM should be fine at 100A, but I wonder what kind of currents you are pulling in bursts? Maybe it's too much due to the motor wind coupled with the weight/gearing of the truck?

Or, maybe your batteries are dropping voltage too much under the heavy load? Are you using NiXX or Lipos? If lipos, you can tell if it's an LVC issue by temporarily lowering or disabling the low voltage cutoff. If it operates fine, then you batt voltage is dipping below cutoff when you really gun it. And that may be a wiring, connector, and/or battery issue.

Just a thought... I have had very severe cogging several times... but it never did any harm to the gears. The only time I have ever stripped a gear is when the motor slipped and loosened the mesh.

I don't see how cogging could strip a gear because... although it sounds bad... there really isn't much power put down. The motor does kick back and forth kinda violently sometimes but I would not think it's moving enough to do damage.

I wonder if the cogging I see on the 4 pole motors is a little different?

GD: I think the Neu issue is because of the relatively high inductance of the coils since they have quite a low turn count compared to a Feigao. Or maybe the software has trouble reading the level/duration of the feedback pulses.

To me, AAngel's issue sounds more like inadequate power whether from the batteries themselves or a weak solder joint somewhere, or a matter of the ESC pulling so much current when he "guns it".

GD,

I believe that what I'm experiencing is different from what you are with the Neu motor. I believe (for what it's worth) that you are experiencing a "communitcation" problem of sorts between the motor and MM. I think that what I'm getting is a case of the motor expecting the truck to be moving and it isn't. When mine cogged that last time, violent is an understatement. I thought for sure that I had cooked my MM. It did, indeed, strip the spur upon cogging.

I'm running 4S lipo, and I don't think it's the battery. I was running a Kokam 4800 pack and it is a beast of a battery. It'll dump current at will. I wish I had some sort of data logger so that I could see what's going on. All I do know is that with the same gearing in my buggy, the problem (cogging) is almost non existent. I hope it is just that my tires are just way too big for the gearing. It must be like running a 20T pinion in a buggy.

The funny thing is that my buddy was doing the same thing (stripping spurs) with his 8ight. We had just assumed that rocks were eating the gears. We were running 16/46 gearing, but he was having more of a cogging problem than I was. He never did try a smaller pinion because he liked the performance. I wonder if his internal diff ratio was different from mine. On the track, his buggy with the 8XL running 16/46 was equally as fast an my buggy running 14/46 with the 7XL. Coming into the straight, it was really a matter of who got out of the turn first that determined who was first at the end of the straight. In know that he was running a slightly larger pinion, but I don't think that two teeth should have made his buggy that fast.

I'm hoping that it is just the gearing. I'm waiting for the postman right now. I hope he has my pinions so that I can try a 10T with the 44T spur. Better yet, I hope that my order from Mike comes in too, so that I can try the 10T pinion with the 46T spur.

If that doesn't do it, all I can assume is that I have a bad connection someplace, although I went through everything with my Fluke DMM and did not detect any measureable resistance. I do remember that when I soldered the 12 gauge wires onto this particular controller, my 700* tip for my metcal was on its last leg.

BTW, considering the size of the ground plane on this MM and its heat sinking ability, I wonder if going with an 800* tip wouldn't be better for soldering on the wires. I don't own a tip that gets that hot, but I was kind of struggling with the 700* tip.

OK, I got my pinions and spurs in. I put the 10T pinion on with a 46T spur. Just trying it out, I programmed the MM with the lowest timing setting, the lowest start power, and 50% punch control. It was much better, but it still cogged. It cogged badly enough to strip another spur gear.

I'm finding all of this pretty disconcerting. I wonder if it is just the sheer mass of the tires. Maybe it's time to just invest in a Quark/Neu combo; or maybe a Compro/Neu combo.

The thought of a cold solder joint someplace keeps popping into my mind, but I'd think that if that was it, I'd have some other symptoms manifesting themselves. Like hot wires/connectors, or something else overheating, but all is running well as long as I'm moving, or once I get moving.

I'm kinda surprised really; you geared it down and lowered all the power settings and it still cogged. Did you try the idea of lowering/shutting off the LVC just in case the battery voltage is sagging and tripping the LVC? Of course you don't want to run like this all the time, but it's a troubleshooting step.

The Quark has been cog-free in both my vehicles (Hyper8 and Revo), but it costs about as much as two MM's and it's not without problems of its own. IMO it needs additional cooling, is kinda big, and it doesn't do 6s well. But it can run anything and is silky smooth.

AA, I have no answer for why the MM would decide to cog... it's been very rare in these setups.

BUT, once it did cog that bad... something may have gone wrong in the esc... like fried caps or something. Try swapping out the MM and see if the porblem follows the esc or the truck.

I had a MM cog real bad once and after than it was a constant problem... it smoked something cause it was unusable after that even though it did continute to operate (never smoked literally). I still need to send that one in to get fixed...

AAngel, what motor are you running? Depending on the motor you may still be over geared. Or what GD said.



On my CRT I'm running 9/51 on 4s with a 2200kv Neu motor/ Quark esc. It runs really good and fast. I can tell I'm a little over geared though. It was fine while the outdoor temps were low, but now that it's getting warmer I can go about 10 - 12 minutes before it thermals. I really should have gotten a much lower kv motor and I would have been fine.

GD, I wouldn't say that it's a constant problem, but now I'm always worried that it will happen again. I'll pull it apart and see if I can visually determine if anything is fried. If I find something, I'm sure that digikey will have it in stock. If not, I'll have to send it in and pay whatever it is that they charge.

Cart, I'm running a Feigao 7XL. I'm not having any thermal problems. It's just the cogging that's making me crazy. Once it's rolling, it's never a problems. I usually isn't a problem taking off from a dead stop either. It's just once in a while.

I suppose that it is decision time. I'm going to have to do something about this unit, but I don't like to wait, so I'll have to order something else. Do I just get another MM for ~$135, or do I bite the bullet and spend the $300+ on the Quark?

That is a tough decision. Time to list the pros and cons of each and figure out what feature/spec means the most to you...

or get the mm replacd for 50 bucks (thats castles flat free replacement no matter what happened to it rite?) and use it till the mmm:018: thats the best idea imo

I tried to contact Castle by both email and phone and no dice either way. I don't know what's up with Castle lately, but the support has been down. I guess I'll try to call them again.

Just to keep anyone interested up to date. If you are thinking of doing a Muggy (or similarly heavy truck with heavy, large tires) with a MM esc, there are a couple of things to keep in mind. Apparently, the Muggy in its stock attire is too much for the little MM on 4S to handle.

Today, I got all of the vehicles that I converted and started playing musical chairs with all of the components. I swapped motors and escs among all of them and found a couple of things. What lead me to this is an email that I got from Joe Ford. He suggested that I do what I did and suggested that, if all of the setups exhibited the same behavior, it was an off the line current draw problem.

When geared 14/46 with the stock 40 series tires, the Muggy cogged no matter what esc and motor I had in it. At 12/46 it began to run about like I wanted it to with the 8XL. At 10/46 it was acceptable with the 7XL. At 10/46 with the 8XL it was as smooth as silk, but the top end really suffered. If I had to guess, I was getting about 30 mph. Hardly nitro stomping material.

Although I emailed Castle with my results, I'm not going to hold my breathe waiting for a response. Phone calls aren't getting returned and emails take days to exchange.

At this point, I have to take a guess and say that the Mamba Max has a really hard time getting a 13lb vehicle with tires of that diameter and weight moving. I'm picking up some Maxx size wheels and Crimefighter MTRs tomorrow. Hopefully the reduced diameter and (more importantly) reduced weight of the tires will allow me to gear the Muggy for performance similar to that of my buggy on the track.

Unfortunately, before I did all of the swapping, I assumed that something was wrong with the MM and I was going to have to send it in. I ordered another to use while mine was being repaired. Now I have a MM that I have no need for, especially knowing what I now know. I could have put that money on a Quark. OK, now I'm just whining.

GD,

If you see this, did you ever try 100% punch control with your MM esc and the Neu motors? If so, what effect did that have on the cogging? Do you notice that your 1512 in the buggy cogs less than the 1515 in the truggy? Have you tried undergearing just to see what effect this has on cogging?

I was really wanting to get a new motor and considering the difficulty of getting a Lehner, I was going to go ahead and get the Neu for the truggy. I was thinking the 1700kv 1515. Now I don't know. I'm all over the place with indecision. My wife's about to kill me, because I told her that going to electric was going to SAVE money. LOL.

You sound like me. Electric is supposed to be easy. I have a pile of stuff that didn't work so well. Over the weekend I fried 2 motors somehow. One of them was a Neu 1515 2200kv. A phase wire was real loose just barely touching. Must have overheated. Now it just sputters. Oh well.
For a big boy like that you may need one of the big MGM esc's. You may run into thermal problems with the Quark even with the biggest heat sink added.

Well... I have messed with 100% punch a little, in my 8ight. It didnt do anything wierd..... only made it have lag on take-off like a rich bogging nitro.

I dont think the truggy with the 1515 is worse than the 1512 in a buggy.. but I also have the truggy geared more conservative than you... low 30s probably.

My buggy doesnt cog much at all with the motor wires soldered well... only a hard launch from a dead stop will make it cog even when geared tall. But the muggy is a different animal with those tires...

You will find the racing rubber much different I think.

My CRT weighs in at 11.5lbs with the big 12k pack...

Yeah.. this cutting edge brushless stuff can be a headache sometimes... and expensive.... but its a different pain than nitro. Nitro can be a constant all day hair pulling expereince.

brushless can be that way.. but it normally is more setup and r&d headaches at home... not surprises at the track

gd, was there a noticeable difference after you directly soldered the wires? reason I ask is I have changed all my wire to 12g, and it made a difference but i still get the occasional sputter.

If it takes a difference I will just directly solder those too, I only have two motors (7xl and 9xl) anyways so its not like I should be changing motors that often.

thanks

Yeah I would say it makes a noticable difference... it still can cog in certain situations, but it's very controllable now. The low speed, low throttle cogging is pretty much gone. (taking off slow... easing on throttle rather than punching it form a standstill)

Before it would cog fairly often no matter how much throttle imput... now it only cogs sometimes on 'rabbit starts'... like 3/4-full throttle launches.

Once it's moving even a few inches it's very rare now to see it cog no matter how hard you punch it.

So basicly it's pretty easy to drive it without cogging... you see real quick what NOT to do. I learned to not punch it from a dead stop... that's about it.

gixxer, I was using the big 6mm connectors from Neu, but with all of the trouble I've been having, I said screw it and direct soldered all of my connections. I've found that catching a cold joint like those is pretty easy and it's just one less thing to worry about.

GD, if that is the only cogging issue you're having, I might just go ahead and order a Neu motor for my truggy. Maybe having a more efficient motor with more nuts will run better. I'm thinking 1515/2.5D for more torque. I really wish that I have a 9XL laying around so that I can try that out to see what effect a lower turn motor geared up would have.

Oh...I can't wait until the day that I have everything settled and I know that I won't have any surprises.

I was very hesitant to pull the trigger on the Quark. I know that Mike had good things to say about the Quark/Neu combo, but the thermal path worries me. The manual scared me a bit too. LOL. I also checked out the MGM controllers and the ones that I can justify spending money on really don't impress me with their specs. Maybe I should just quite all of this whining and get myself a Neu motor. At least I'll have it, even if it doesn't play nicely with my MM controller. It will give me something to look forward to in the Monster Max.

GD, that's kind of funny, with the problems you're having, because with my problem, if I punch it from a dead stop and it cogs, it strips the spur gear.

Will going with the conventional monster truck tires, if you know, make much of a difference from the 40 series tires?

gd and aangel thanks. I think I will just go ahead and solder that up directly then. It doesn't happen much now but if i can get rid of it all together that would be awesome.

one more question. how much of a difference do you think I would notice in temp if I went to a neu instead of the feiago 9xl I am running now? Right now on a 5s pack the motor is in the 160-170 range.

I don't own any "good" motors, but from what Mike tells me; going with a good motor like a Lehner or Neu will cut the temps considerably AND you won't need to run a fan.

gixxer, are you really running a MM on 5S lipo? I've been itching to go with a lower kv motor on more voltage, but thought I'd smoke the MM.

I still have a hard time saying it doesn't cog much.... but really it is better. To some it may NOT be acceptable though.

But since I hardwired the motor, I have raced with it and played in the street geared 18/46, and I did several tests rippping wheelies in the house with the eagletree etc. (creep a few inches then grab throttle....)

Occasionally it still has cogged on me unexpectedly... but it's not very often. You just have to be real quick to react... let off throttle and go again.

At that last race... it never cogged once on start up etc. Only thing funny that day was a couple times I got a 'glitch' while at speed. That's not good either but it's not a "neu' issue... I have seen the exact same thing on rare occasions with a box stock MM setup in 1/10 buggies.

I have not run the truggy or 1515 with the motor hardwired yet.... I have a Quark that I finally put in there for now, instead of selling off.

aangel, yeah I have been running it on 5s. At first i had a 4s and was running the 7xl but then picked up a 5s and went to the 9xl. I still have both motors but only run the 9xl because I got rid of the 4s pack and 5s on the 7xl would be stupid fast in my 8ight.

so far no smoke so I am happy but really dont want to recommend it because its way out of spec. I was actually going to go back to 4s because I didn't think it would hold up but so far so good. Now if they just release the MMM I wouldn't have to worry about it.

OK, after about a week, this is what it boils down to (according to Castle). This is the email that I was sent,

I may just be an idiot, but I don't know what to make of it. I can see that he is alluding to the fact that the MM is NOT meant to be run in monster trucks; but then it seems that he's saying that the problem in not being caused by the esc, but rather too much of a current demand. I don't see how the batteries could be causing this problem. I'm running Kokam packs (as I told him in a previous email). If the Kokams aren't enough, then what do I need. He also says that one way to drop current demand is to go with a LOWER voltage pack?

Can anyone shed some light on this? I'm really tired of trying to exchange emails and trying to get someone on the phone.

What to make of it? Spin doctor.... which is why it doesn't make much sense. It's bull#%@! ;)

Castle has this tendency... when all else fails (or they don't have an answer...) blame the batteries. They have been preaching about batteries since the Mamba25 first came out.

It's true that often the battery is the weak point/problem for many of their customers... I think they talk about inadequate batteries so much that they brainwash themselves.

I have been in contact off and on with Castle for months... and still they seems to bring up batteries quite often in babbling with me... then I remind them that for example I run a 12000 mah lipo. They say yeah that's good enough...

Referring to 1/10 cars .... thye have said on the record that a good nimh pack is just fine. (It's the stick packs and junk cells that are the problem)

IMO it's obvious the Kokam 4800 are good enough. They can flow 2-3 times the current of a nimh pack.

By Castle's own words... they say to look at whatever I see on a datalogger for peak amps, and double that for what the true micro-second current is. (they say the sample rate isn't fast enough with basic loggers to register these spikes... personally if such spikes NEVER show up on a 10 sample/sec logger... then I think such spikes don't matter. imo. )

So... even considering that, the Kokam packs are up to the task easily.

Does it ONLY have problems under full throttle lauches from a dead stop?

EDIT... gee I was kinda harsh on castle here huh? hee hee

The part about lowering the voltage makes sense; running at a lower voltage will reduce the current - assuming of course that motor, gearing, weight , etc doesn't change...

If it's a battery issue, you copuld verify that by lowering the start power, increasing punch control, and reducing the timing - all things that would cause the ESC to go gentler on the batteries.

I'm also wondering if the LVC setting is contributing to this. Even if the battery voltage doesn't drop much, heavy current on the wires, solder joints, or even on the circuit traces could conceivably drop enough voltage to trip the LVC. Has anyone tried shutting off the LVC as a test? Of course I wouldn't run this way, but it's just a test.

I had the LVC off on all those tests I ran... didn't make a difference that I could tell. But I will pay more attention in the future and see if the lvc effects cogging

Most of my cogging problems went away when I made all of the settings on the MM controller as tame as possible. With lipos, it should still rip anyway. I had bad cogging at first, now it only occurs accelerating hard from a dead stop.

This cogging problem that I am having can happen at any thing, when starting from a standstill. From slowly easing on the throttle to jamming 1/2 throttle all of a sudden. It doesn't happen everytime, but enough to be concerned about it. The trouble is that when it happens during the heat of a race or bashing session on the track, I can't always tell when the truck is cogging. I mean that I can't tell if the truck isn't moving because of cogging or if it's hung up on something; and if it is cogging and I give it too much throttle to get going again after a wipe out, I fry the spur gear.

I also don't understand the part about lower voltage getting me less of an amp draw. I thought that given a particular motor, say a 1500 watt motor, the motor can generate the power that is built to generate. So, if I'm running a 1500 watt motor, it would need to draw ~101A to make 1500 watts with a 14.8v pack. If I drop the voltage down to 11.1v, then it would need to draw 135A to make the same power, so I'm thinking that dropping the voltage would make the system draw more amps. Am I missing something or oversimplifying something?

I'm running my system with the lowest timing, lowest start power, and 0% punch control. The punch control makes the truck undriveable on our track. Our track is very tight and technical.

I have noticed that the "problem" gets better and I reduce the gearing. I'm now running a 10T pinion and it's about to a point where I could live with it, but would rather not have to. I have't temped anything yet, but I ran the hell out of the truck yesterday and the esc was noticeably way hotter than the motor, so I'm going to assume that I'm still overgeared a bit.

GD, what gearing are you running on your truggy? I'd imagine that you are running proline MT tires. Maybe the crime fighters, bow ties, or holeshots.

On a side note, GD, you were kind of rough on Castle, but the answer that I got from them was complete BS. Until a very short time ago, I was an avid fan of the Castle products, but I'm starting to change my mind. I can't get support to save my life. I'd imagine that it's because they're devoting a lot of time to the MMM project, but what happens when I need support for the MMM and they're working on the next latest and greatest thing. Am I, again, going to be left hanging for support.

Of course, I still have to keep in mind that the MM was never intended to be used in an 1/8th scale application.

the only thing i can think of is lowering the punch control.