FastGT94

iTrader: (1)

So I made a rookie mistake and ran my buggy about 20 minutes instead of 6. (Trinity Monster Max 13.5)

As a result, the motor was too hot to touch and a very light whisp of smoke came from it.

After letting it cool, it ran fine the rest of the day and I was keeping up decently with a 2wd buggy running a 13.5, but this was my first time out with the motor and I have no clue if its performing to its max potential now that I overheated it once.

I spoke to trinity who recommended testing the rotor for its strength, but I have no clue how to do this. Would the test where you verify voltage across all leads while spinning the motor with a drill be a good indicator of rotor strength?

Sorry for a rookie question but trying to tell if I hurt the motor or not without a motor or rotor analyzer.

Thanks!

Jwilliams5

iTrader: (27)

They make rotor testing tools specifically for rc. But the meter for the rotor is just an over priced gauss meter. I wouldn’t recommend trying to use the motor to make power the way you described. One mishap can fry it for sure. Arcing across the poles isn’t good. If your motor ran fine but did smoke it’s likely the plastic insulater ring and/ or the protective coating on the copper windings. There really isn’t a great way to tell how much longer the motor can run without smoking your motor or the esc and motor. It’s a run at your own risk type of deal, your rotor is probably fine as well as maybe your stator. But I would personally buy another stator and just install the rotor,sensor board, and end plates onto it. Basically giving you a new motor at a much cheaper price point.

Roelof

If 20 minutes was killing the motor than 5 minutes will be harmfull as well.

FastGT94

iTrader: (1)

Hi there, not sure I understand. Is this a statement about overall temps/setup? After 5-10 minutes the motor was warm but I could easily touch it and not let go vs 20-25 minutes where I could barely touch it for more than a quick moment.

FastGT94

iTrader: (1)

Thanks, I'll see if a Monster Max 13.5 stator is available yet. Can't find one to "order" on the team trinity site.

billdelong

iTrader: (33)

I've got this same 13.5T Monster Max in my EB410 and for 5 min quals (without a fan) I was reading 160° off the track with 24/81 gearing. After the 8 min mains I was reading 180° and during practice I ran to LVC (roughly 15 min) it got up to 200°... I've since installed a fan and try not to run to LVC anymore, since then my temps are coming off around 140° with the same gearing regardless of run time.

Ironically, the motor doesn't seem quite as fast after getting it up to 200°, though it's still faster than pretty much everyone else's motor at my club... not sure if the lower temps are slowing it down, if it's just in my head or if I damaged either the rotor/stator.... when I start losing position then I'll consider swapping some parts out to see if that makes any difference.

Jwilliams5

iTrader: (27)

What roelof is trying to say is that your timing, gearing or overall setup is a bit off. Not the entire cars setup, just the motor and gearing part. I don’t know what buggy your running or the overall weight. But if it were me I’d start with the recommended gearing with moderate timing in the motor. Say, 40-45* to start. Run a couple mins(2) then temp the motor, repeat this until you reach the maximum race time for your class. Let everything cool down, charge up a battery and if the temps were stable run for 4 mins then temp and then again repeat this until you reach your maximum race time for your class. If temps were still stable then you can start tuning the gear and timing. I personally start with the gearing. I gear till it tops out roughly 1/2-3/4 way down the straight. For 2wd 3/4 for 4wd 1/2 down the straight. Keeping a check on temps as I go. After I find the correct gearing I’ll tune my timing. I start with the correct gear and drop the pinion (1 tooth for 2wd, 2 teeth for 4wd) then I advance my timing roughly 2 degrees. Keeping a check on temps I set my timing to the power or power band I need for a particular layout or track, all while taking into account temps. I hope this helps you tune your motor. This is in no way the only way, it’s just what I do it to keep from over timing/gearing my cars out of the gate. I generally have the same base setup no matter which motor I am tuning, but I use this as a baseline. Then fine tune it to my current needs on track!

FastGT94

iTrader: (1)

Thanks for clarifying!

I'll get a temp gun and check it out next time out but I do know it runs a lot cooler when less than 10 min. That is with a 26/78 gearing on my B64D that has no weight reduction and a 4600mAh battery pack.

Additionally, I read that the winding wires in the stator are 220C rated. Does that not mean that they resist melting up to 220 degrees Celsius?

In that case, I highly doubt the motor got to over 420 degrees F in 20-25 min... and I'd think the stator is fine... but of course have no way to verify. I'm going to at least take things apart and make sure the insulator plate didn't start to melt and the rotor doesn't have any signs of cracking.

Waiting on Trinity to get back to me regarding buying another Monster Stator to see I can replace for about $25 like the other ones cost on their page

Jwilliams5

iTrader: (27)

Yea the 220c rating is the usable heat range of the wire. Not the usable heat range of the motor. I promise you your motor will never meet 420*. It will melt way before then. It’s also a sales gimmick, like Ricky bobby endorsing anything lol. The gearing sounds about right for a 13.5 spec 4wd car. Although it’s a bit on the low side meaning it’s for a really fast track with fast sweeping turns and large straights, and few or no 180’s. If that sounds like the track your running on the you shouldn’t need a bunch of time tuning the gear or timing. If your track has shorter straights, not really fast or flowing sweeper turns with a bunch of 180’s then you should raise your spur up some to maybe the 81. Another good way to tell if you need a larger spur is if you find yourself using the brakes a lot in a stock class. This usually means the track is tighter and less flowing. It isn’t a bad thing. Just another “feel” towards tuning your car. Also since it’s a b64d, you should add a fan at the back of your motor. I place mine 10mm away from the endbell, and 5mm off center towards the side of the car. You can place it anywhere, or anyway you want. But this has proven to cool my cars better than any other ways I have tried. Again 10mm away then 5mm offset to the left or passenger side of the car. Double sided tape may suffice depending on how you jump your car. But most use a mount an drill the chassis for it.

Jwilliams5

iTrader: (27)

On another note regarding temps... if your motor reads 200* on the outside. It’s more like 220-240* on the inside. Anytime your motor exceeds 160-170* your waiting the motor. Yes it will live. Yes it will still make good power. But that’s usually on the edge and totally unnecessary for club Racing. Also if you can smell it, it’s hot. Regardless of whatever temp gun you have. I gear and time my motors to about 155* max. This is with a fan or without. Any more than that and I just drop a faster motor in.

FastGT94

iTrader: (1)

Thanks, I do already have a WTF fan installed the way you said (bought one that day immediately after the first episode).

Quick point to note is my gearing at the time of overheating was 28/78, which I reduced to 26/78 for the rest of the day.

The tracks I'm typically on are on the smaller side with the exception of one clay track that has a longer straight. For the carpet track that I was on, the car didn't feel like it was accelerating at its max potential and yes, to your point, the straight isn't long at all. I was thinking of lowering the pinion to a 24 from 26 instead of increasing the spur gear to 81. Same effect right? Goal is shorter gearing (vs taller) since the top speed is less important which means I want the pinion to spin more for a single spur turn.

The timing is set at 46* which was what Eric at Team EA Motorsports validated my motor to require prior to shipping it out.

Finally, what are you using to verify that the RPMs aren't maxing out on a straight? I have a telemetry Rx/Tx but no actual telemetry setup. Do I really need to buy a RPM sensor and hook that up, or can one do this literally by ear? (if the motor's "sound" or pitch stops getting higher before halfway down the straight, for example)

Appreciate all the feedback! Its really helping a rookie like myself

Jwilliams5

iTrader: (27)

Regarding the smaller pinion is equivalent to a larger spur, yes and no. Think of it like this... if your car had gears as in shifts, it would be able to maintain a given rpm window. Our rc cars don’t have shifts. So we use total gearing for the “grey” area. Given that we have a window we need to take into account the slowest section and the fastest section. And gracefully choose our grey area. For stock class and Blinky modes these windows of rpm are very very small or short. The opposite is true for mod motors as they have more than twice the usable rpms. So for a stock class car on a relatively short straightaway, tight 180 turn track you should use a larger spur to let the motor have an easier load at the same ratio. Ergo a gas brake gas brake track. For a stock class car on a high speed, flowing sweeper, longer straightaway type track your rpm window didn’t change.. so you use a smaller spur to keep the motor happy inside its rpm window.

It’s a lot more into it than just what I’ve mentioned. But basically if your on a short, tight track go to a larger spur. If your on a large, flowing, high speed track use a smaller spur gear. Even if it happens to be the same overall ratio, the way the car will put power down will be drastically different. One gear will rev effortlessly to pull hard out of the tight corner, the other will be smoother as well as pull harder on the high speed sections.

On to knowing when it peaks out on the fastest straight... it’s a visual “feel” type of deal. You can generally tell when your car tops out anywhere. If you can’t or don’t believe you “know”... throw a crazy small pinion on and make a few laps or turns. You’ll notice how quick it tops out. Then go back to your other gear. You will instantly notice a difference in how the car is putting the power to the track as well as putting the power to good use. Yes it will be dramatic. Just don’t take real jumps with an itty bitty pinion on. Bad things may happen, shorter jumps, casing, and worse lawn darting into the face of the down ramps. It’s funny yes but could cause broken arms and more.

I would say your gearing is really close after conversing back and forth. As with the nature of stock class Racing your itching to get every bit out of the car and motor. It’s natural. So try leaving your timing alone until you find an awesome gear combo. So maybe try using an 80 or 81 at the same ratio if you can. Then try your 78 at the same ratio, then try a 76 or 75 at again the same ratio. The car should roughly be the same speed on the straight. But it will pull harder/softer on jump faces or coming out of the corners. Adjust your spur to suit your driving style to the track your running. Then play with timing. But 46* per Eric, is about where your motor pulled the hardest overall. Not the fastest, not the peak of torque, but a great blend to match your application.

Also the plastic spider gears in the diffs, plastic cross shafts in the diffs, lightweight axles and drive shafts will improve your car in the handling and acceleration an enormous amount for stock Racing.

200sxr

I have a theory that may work without a motor tester providing your ESC has some form of data logging capability.

An over-heated rotor will lose its magnetic strength and the KV will go up compared to a rotor that has not been over-heated.

For my Tekin ESC I can see the battery voltage as well as the RPM of the motor hence I can work out the KV of the motor. If the KV has gone up at the same timing then maybe the rotor has been over-heated.

Then again this will be useful if you have a base-line of the motor when it was new. I usually use a generatic motor to tester to base-line my new motors when they come out of the box.

I have an old LRP x20 13.5t motor that regularly sees just over 100 deg C at the can. Once it gets hot I can really see and feel the drop in performance. However once it cools down the performance comes back. Having said that I would not do it to a nice motor that you race with.

I sometimes wonder why "blinky" racing limits the ability to use timing in the ESC.... I can only assume blinky racing started when the average ESCs do not have the ability to change the timing have turbo mode, etc. These days pretty much every ESC has the ability to change the timing; if the class is purely governed by the turn of the motor then maybe we will not be cooking our expensive motor as often?

Jwilliams5

iTrader: (27)

Agreed. But we have to remember in open stock classes... a motor will only hold so much boost and turbo before it melts anyway. I’ve said this since I started really Racing 1/10 scale again. Let us run boost. We will see who is relying on the boost or who can really drive.

FastGT94

iTrader: (1)

Makes sense, I'll look into switching back to my 81T spur and try that out.

Thanks for the thorough replies!