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Old 2012.08.06, 10:54 AM   #1
HammondCheese
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Atomic Motors - Recommended Gear Ratios

Hi,
I noticed that the details provided for the 17mm stock plus motor (MO-028) by stockists often includes recommended gear ratios for both 2wd and awd applications. I'm assuming that these were provided by Atomic. Are there any officially (or semi official) recommended ratios that have been made available for the other motors? Specifically I'm looking for ones for the rest of the 17mm series and the ASF Spec MO-033 for both 2wd and 4wd. I suspect an optimistically long gearing selection on my behalf (awd vs t2plus)contributed to a partial meltdown on the weekend. These numbers may help me (and maybe others) choose more wisely in the future.

Thanks

John
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Old 2012.08.11, 11:16 PM   #2
Felix2010
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The T2+ is 35t with Neo magnets. A similar motor is the Atomic CHILI, and Atomic recommends for the AWD gear ratio of 6.38:1 to 5.34:1. The Chili is slightly faster due to advanced-brush timing design. But the T2+ on an AWD will eat low gear ratios up and give you both torque and speed.

With gear ratios higher than 5.00:1 with the AWD the T2+ will actually lose performance .

And you run the risk of chassis failure due to heat (Even if your FET's can take the heat, the chassis and PCB cannot handle ultra-high temps 150*f+.

Properly breaking in your motor's bearings (degreasing them + lubing them with high-end lube like Acer lube); And Adjusting for perfect alignment of motor can with endbell, and breaking-in brushes all can dramatically reduce motor Amp draw and allow gear ratio's of =>4.5 to be used for extra high speed tracks.
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Old 2012.08.12, 11:36 PM   #3
herman
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Quote:
With gear ratios higher than 5.00:1 with the AWD the T2+ will actually lose performance .
hmm... kinda confused here... do you mean lower than 5.00:1?
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Old 2012.08.12, 11:54 PM   #4
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with a lower gear ratio you will get better performance. IE: more torque and more speed. After you put your gear ratio higher than 5:1 you will get less of these things.
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Old 2012.08.13, 10:03 AM   #5
Felix2010
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Quote:
Originally Posted by herman View Post
hmm... kinda confused here... do you mean lower than 5.00:1?
I'm used to calling gear ratios by the 1:1 car gear ratio, meaning 1st, 2nd,3rd, 4th = Higher gear ratio, lower XX:1 ratio. My bad for any confusion herman
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Old 2012.08.13, 11:36 AM   #6
HammondCheese
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Quote:
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The T2+ is 35t with Neo magnets. A similar motor is the Atomic CHILI, and Atomic recommends for the AWD gear ratio of 6.38:1 to 5.34:1. .........
........
And you run the risk of chassis failure due to heat (Even if your FET's can take the heat, the chassis and PCB cannot handle ultra-high temps 150*f+.

Properly breaking in your motor's bearings .....
Thanks for the tips Felix. I was running 5.34:1 when it all went pear shaped, when I decide to give the t2+ another go I'll probaly start off somewhere around 6:1 and see how it goes after a few laps.

And yes, as you suggested the melting was in the cover over the fets and possibly a little bit of solder once the cover had collapsed on the fets I think- all of this in about 10 laps. Car was still running though. Only way I found out before it got worse was I flipped and popped the shell off......
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Old 2012.08.14, 06:28 AM   #7
herman
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no worries felix2010... still a newbie when it comes to these gear ratios...

i do know that lower toothed pinions have longer run times, better acceleration (more torque) but lower top speed

conversely higher toothed pinions have shorter run times, lower acceleration (less torque) but higher top speed

lower toothed pinions produce higher gear ratios (53/6 = 8.83:1) compared to higher toothed pinions (provided that the spur gear is the same - 53/9 = 5.8:1)

so a gear ratio of 6.38:1 to 5.34:1 should be fine...
and anything lower than 5.0:1 (i.e. 53/12 = 4.41:1) will loose performance?

i think that these motors are torquey and lower pinions (higher gear ratios) may overload the electronics and cause them to fry... can anybody confirm this?
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Old 2012.08.14, 07:17 AM   #8
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no worries felix2010... still a newbie when it comes to these gear ratios...

i do know that lower toothed pinions have longer run times, better acceleration (more torque) but lower top speed

conversely higher toothed pinions have shorter run times, lower acceleration (less torque) but higher top speed

lower toothed pinions produce higher gear ratios (53/6 = 8.83:1) compared to higher toothed pinions (provided that the spur gear is the same - 53/9 = 5.8:1)

so a gear ratio of 6.38:1 to 5.34:1 should be fine...
and anything lower than 5.0:1 (i.e. 53/12 = 4.41:1) will loose performance?

i think that these motors are torquey and lower pinions (higher gear ratios) may overload the electronics and cause them to fry... can anybody confirm this?
I'm not an Expert's-Expert, so i may be wrong a little or a lot: But ,using lower #'d pinions (Producing high gear ratio's 6-7(+):1) will actually be less work for the FET's / electronics due to the "sweet spot" for efficiency falling in the smaller-sized, lower-#'d pinion gears. Using a tall High'd pinion gear on this motor will cause tremendous current draws during stop/accelerating and hard throttle use. These spikes caused by motor strain from too-tall a pinion gear is what pop-fries FET's and eats chassis plastic for breakfast...
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Old 2012.08.15, 03:09 AM   #9
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ah ha... that's why my old unfetted mr01 (yes folks that is not a typo...) board blew...

i was using a 10T pinion on it and it was quite fast and quick... unfortunately... the fets blew after a while... (this was a loong time ago)

thanks for the info... so getting back to the question...

anything lower than 5.0:1 (i.e. 53/12 = 4.41:1) compared to say 53/9 = 5.8:1 will loose performance?

or probably run the risk of blown fets? unless properly fetted (meaning stacking them or changing out the stock fets to better ones) that is
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Old 2012.08.15, 03:46 AM   #10
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For AWD: Running lower than 5.0:1 gear ratio (such as 4.5:1) with a 35t motor with Neo magnets (T2+ or CHILI) if you run hard (Hard acceleration/deceleration and starts/stops) you will definitely cause a lot of heat to be generated by the FET's. The FETs will keep pumping out the Amps until failure or to the point of chassis melting and FET damage or even FET solder softening to where the solder melts and re-freezes on the board >>where you get things like side-ways FETS on blown boards and missing FETs that actually melted right-off the PCB...

I guess a better way to put it is, unless you're racing on a HUGE track, then 5.0:1 gear ratios or lower will most-likely cost you performance. The one case for low-ratio gearing with fast RPM motors is when you can actually use the extra HP produced (HUGE track).

For 2WD: You can definitely run lower than 5.0:1 (Like 4.5:1) gear ratio's using a similar 35t/NEO-mag motor. Less resistance in the 2WD drivetrain, and lighter. Just don't go to high of pinion (BIG pinion) like 14/53 or 12/52 or else you'll heat the FETs fast; If you have a lot of grip on your track too, this friction causes more current flow due to higher % power-demand on-power and thus produces PCB/solder/MOSFET failure & chassis distortion/melting.
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Old 2012.08.15, 04:34 AM   #11
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cool... i just gave 53/12 as an example (to compute for a lower gear ratio)...
thanks for the additional info...
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