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the amps, the amps!

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Old 03-18-2017, 10:10 AM
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Default the amps, the amps!

Hello guys just getting back into the hobby after a long time gone.
So I jumped in head first and bought a B6d. Im looking to run modified off road with a trinity monster 8.5 I also bought a motor analyzer to help dial in my motors the problem Im having is I cant find ANYTHING that shows what amps is proper for a said turn motor. Ie. what amp should a 17.5 pull vs an 8.5 or 10.5 for that matter. I also have a T5 with a reedy 17.5 in it with the hopes of running stock off road with it.
basically I went from brushed to gas and now learning the brushless and really need help getting the learning curve shortened.
Thanks in advance
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Old 03-18-2017, 01:19 PM
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Originally Posted by Nutty B6 View Post
Hello guys just getting back into the hobby after a long time gone.
So I jumped in head first and bought a B6d. Im looking to run modified off road with a trinity monster 8.5 I also bought a motor analyzer to help dial in my motors the problem Im having is I cant find ANYTHING that shows what amps is proper for a said turn motor. Ie. what amp should a 17.5 pull vs an 8.5 or 10.5 for that matter. I also have a T5 with a reedy 17.5 in it with the hopes of running stock off road with it.
basically I went from brushed to gas and now learning the brushless and really need help getting the learning curve shortened.
Thanks in advance
Where did you get the motor analyzer. Been looking for one.
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Old 03-18-2017, 01:48 PM
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Get the analyzer from RC Juice.

Mod motors are typically not tuned on the analyzer. The analyzer are usually not rated for less than 13.5 or 10.5 turn motors. Additionally, you can run boost on the ESC in a modified class. So set the motor mechanical timing to 30 degrees, gear for infield punch, and add boost if you need a little more speed on the straight.
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Old 03-18-2017, 03:56 PM
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Originally Posted by Nutty B6 View Post
Hello guys just getting back into the hobby after a long time gone.
So I jumped in head first and bought a B6d. Im looking to run modified off road with a trinity monster 8.5 I also bought a motor analyzer to help dial in my motors the problem Im having is I cant find ANYTHING that shows what amps is proper for a said turn motor. Ie. what amp should a 17.5 pull vs an 8.5 or 10.5 for that matter. I also have a T5 with a reedy 17.5 in it with the hopes of running stock off road with it.
basically I went from brushed to gas and now learning the brushless and really need help getting the learning curve shortened.
Thanks in advance

What do you need the amps for?

I've messed around with measuring 1/8 scale amp draw on a truggy, and I saw peak amp draw of nearly 100A (@14.4v, aka "4s") from average quality Lipo batteries. The lipos could deliver more current than that, although I believe this was approaching being an unhealthy load on the batteries.

By comparison, when I took a stab at indoor oval 1/10 scale, I was drawing something like 26amps on a 13.5 tekin redline (high rpm) motor.

The reason why I was testing amp draw on my truggy was because I was concerned my batteries were getting prematurely damaged by excessive current draw. With a big motor and a heavy truck, it is possible to damage batteries, if their internal resistance is too high.

But that reason is irrelevant in 1/10, as far as I can tell. The motors are smaller and they draw a lot less current, so any lipo should be able to provide more than enough amperage. (I'm not sure about low turn motors, like a 2.5t...but I feel pretty confident saying they don't draw 100A.)



That's the only reason I can think of for testing amp draw on a brushless RC. Maybe that is a big change from what you are used to? The whole appeal of brushless is the "plug and play", low maintenance benefit of brushless. I've heard rumors of how people used to have to endlessly fiddle with their brushed motors back in the day to get max performance out of them. But with brushless, you might oil the bearings occasionally. That's about all you can do. If the can isn't sealed, you might occasionally clean it out? But mostly there isn't anything serviceable on a brushless motor.


But if you are interested, there is still a good amount of voodoo, black magic, and witchcraft that goes on in the hobby!

People do things like pre-heat their batteries, because a warm battery is more efficient...therefore they have less voltage drop at a given load...which means more RPMs. And people over-charge batteries slightly, again, to get higher volts, and therefore more RPMs. And whether it makes any difference, it's hard to say...but some people buy new batteries constantly, thinking that the brand new battery is magically faster. (But logically speaking, and as long as charge/ discharge rate is reasonable, a battery used 5x or even 10x should be exactly the same as a brand new pack...the natural sample variation between packs will be greater than any loss experienced over the first handful of cycles. I'm pretty sure, but I'm not an engineer.
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Old 03-18-2017, 09:27 PM
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Generally 17.5 motors are tuned for max horsepower while modified motors are tuned for smoothness and drivability. Sorry to say it but a motorlyzer isn't going to do you much good on in regards to mod tuning. There are a lot of factors to tuning for mod. If you're getting in to brushless modified I would recommend the following as a starting tuning guide:

1. Set your esc to 100% and calibrate your esc with your end points at 100%.

2. Dial down your throttle epa to 85%.

3. Check setup sheets and your manual for gearing recommendations regarding your wind of motor.

4. Start about two teeth lower than what others recommend and keep the the stock timing.

5. Gear up a tooth at a time, monitor Temps and feel.

6. Once the motor reaches peak performance take note of the timing, gearing, and temp.

7. Go back to stock timing and gear up a tooth. Start the process over.

8. If you do this for a couple teeth you'll get a feel for what suits you and your style of driving.

9. Don't use pro set up sheets as gospel, just a reference. Most of what they publish isn't what they run and it's not set up for your driving level or suited to how you drive.
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Old 03-18-2017, 09:53 PM
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I bought an analyzer. Don't know if it's much use other than knowing what amp draw your motors are drawing. That said different motors seem to require different amp draw. The last two tuned motors I've bought were stock team scream and Fantom. Both were pulling about 3.5 amps and were rockets. Ballistic. Yet everyone watched a video on YouTube about amp draw and is magically tuning everything at 6 amps plus. I turned Timing up that high once on my motor and it faded fast so pulled it off once I noticed. Wonder how many over times motors are being over driven right now having fans in cold weather but drawing way too much power... just my 2 cents and am sticking with the motor tuners' advice. I will take their word for it rather than my magic new 6 amp discovery from a Chinese motor analyzer. I say this as someone who spent money on all his stuff and almost bought into it
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Old 03-19-2017, 08:07 AM
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Originally Posted by JAE View Post
I bought an analyzer. Don't know if it's much use other than knowing what amp draw your motors are drawing. That said different motors seem to require different amp draw. The last two tuned motors I've bought were stock team scream and Fantom. Both were pulling about 3.5 amps and were rockets. Ballistic. Yet everyone watched a video on YouTube about amp draw and is magically tuning everything at 6 amps plus. I turned Timing up that high once on my motor and it faded fast so pulled it off once I noticed. Wonder how many over times motors are being over driven right now having fans in cold weather but drawing way too much power... just my 2 cents and am sticking with the motor tuners' advice. I will take their word for it rather than my magic new 6 amp discovery from a Chinese motor analyzer. I say this as someone who spent money on all his stuff and almost bought into it
I'm guessing the 6 amp thing is intended for 2S applications. (touring car) 1S seems to be more around the 3.0-3.5 range.
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Old 03-19-2017, 08:39 AM
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A guy I know who is fast uses something that attaches to his ESC similar to the motor analyser:

https://shop.stormerhobbies.com/product-p/samsb-001.htm

He actually tunes his motors for less amps than the 6amp setup and just adjusts gearing. Temps stay lower, etc. I beleive its 2.4 - 3.6A . His motors are fast and work well for our conditions.

I do the 6amp method on 2S 1/10 2wd buggy and its fast and no heat issues, however, on 1/10 4wd buggy I am going to go down a bit on the amps as I find I get a bit of fade if I try to step it up gearing wise to get some more speed.

Maybe do 5amps for 2wd buggy to test and 4amps on 4wd.
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Old 03-19-2017, 06:50 PM
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With an analyzer, I record a bunch of data points of power in (battery voltage x current draw) and kv for each timing mark. When you plot it, you can clearly see that at a certain timing, a motor will really start to make good rpm. Above that, you see the power go way up and the rpm barely increase. The few I've tuned have ended up more like 4.0 to 4.5 A draw at 8.4 V.

I'd really like a dyno though!
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Old 03-20-2017, 12:21 PM
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Rule of thumb a boosted 17.5 can catch a 10.5. And a boosted 10.5 can catch a 6.5.
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Old 03-20-2017, 09:18 PM
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Thanks guys for all the input! The only reason I bought the analyzer was to make sure I was getting all the motor had to offer. I have tested a couple dozen motors now some in duplicate IE same turn and make, straight out of the box they were no where near each other in rpm or timing like 10+ degrees difference and 4k rpm.
I also saw some you tube where guys were pushing 6-7 amps out of 17.5 motors.I must admit pushed me towards getting the box so I could test my motors. again Im a tinkerer from back when we had Cobra lathes to get our coms straight..lol
to date I have done what Callaway said and just went after the sweet spot as to what I consider it anyway. I have come to the same realization that most of the rpm sweet spots for 17.5 seem to be in the 4-5.5 amp area but these same motors came out of the box drawing 2.5??
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Old 03-21-2017, 10:30 AM
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Ive been running castle equipment in my cars for over a year now and they are still alive.
I would say they feel like the Tekin brushless motors back in the day because they were sensorless. They have a sensored feel to them even thou they are sensorless.
You can definitely race with a sidewinder 3 system I have three.
More expensive systems doesn't always make it better. Heck they run HobbyWing and Trackstar stuff at my track and those are even cheaper than a castle.
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