E- revo gearing questions
 

I plan on getting an e-revo, and will be running a quark 125b w/ 7xl...... any suggestions for gearing

What kind of battery setup were you looking at? I've read that the 7xl runs pretty hot, so you would probably be best off to gear for ~40mph.

2s2p (4s) maxxamps 8000 lipo's.....i ran this setup with no issues on my gmaxx & it weighed about 11lbs....

Go to this site and plug in some values.
http://scriptasylum.com/rc_speed/_top_speed.html

Front/Rear Differential Gear Ratio: "Traxxas Revo"
Transmission Gear Ratio: E-maxx (3905) 1-Speed or 2-Speed 2nd Gear"
Spur gear: Assuming you're going to be using 32p (0.8mod); 54 56, 58, 62, 65, 68(Stock)
Pinion gear: These can be had from tower, impaktrc, rc-monster, kershawdesign. (Stock is 19t)


This is what you might be looking at:

Differential Ratio: 2.8461538461538463
Transmission Ratio: 1.8333333333333335
Other Ratio: 1
Spur Tooth Count: 54
Pinion Tooth Count: 19
Total Voltage: 14.8
Motor KV: 2382
Tire Diameter (inches): 5.75
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0
Spur/Pinion Ratio: 2.84 : 1
Total Ratio: 14.82996 : 1
Tire Circumference (inches): 18.06 inches (458.83 mm)
Total Motor Speed: 35253.6 RPM
Vehicle Speed: 40.66 mph (65.32 km/h)
Estimated Adjusted Speed: 39 mph (62 km/h) - 5% loss
Effective KV Value: 2382

You makee a mistake on the spur gear , the stock e-revo spur gear is 68T, mod .8.
So with your 4s li-po, gear it with a 23T 32pitch pinion, and you'll be in the 39-40m/h:wink:

On my e-revo, on 6s, with badland tire (5.85" OD) i'll use a 22T pinion.

You'll be ditching that 7xl right quick, if it lasts long enough ;). It's too hot a motor for something heavy as a Revo. 8xl even runs too hot on 4s in my Revo. My 9xl on 4s is good for only about 15 minutes before it's too warm for comfort.

J.

Maybee you was over geared with your 9XL, because i've run it in a 11.6lbs truggy with excellent result.
DOn,t think an electric revo weight more than 11 lbs.

Well here is all the info in one shot
quark 125b
7xl
2s2p (4s) 8000 maxamps lipo
badland tires

so i should gear it the following
23t pinion
68t spur

feigaos will stay cool if you can run them in a meat locker....:lol:

Yeah i do know that 68T is the stock spur, but i was using a 54T spur that traxxas makes for the jato. Since a spur is cheaper than a pinion, i thought i would suggest another spur(~$3) instead of another pinion(~$12).

that spur would be too small for anything Emaxx wise, you'd need a 28 to a 30 tooth pinion to get any mesh and the gearing would be too much for even the most powerful setups

From a few trials with the E-Revo, don't gear for 40mph with the stock tires. My first gearing was 24/68 on a 1515 running at about 30,000rpm geared for 35mph - at 35 mph the stock tires balloon enough (about a full 2" in diameter)to make the speed closer to 50mph+ and will drop your overall ratio tremendously and you will get some serious heat (got up to 180* on a 1515 in 10 minutes - a 7XL would become a griddle)

I just switched out to a 1515 running at ~36,000rpm on 6S and geared it at 18/62 with the Badlands MT (again ~35mph) and it was running much smoother and motor temps around ~130*.

The badlands do not balloon much at all. The Talons are cookie cutters - if you gear for 40 you're going to balloon close to 55-60mph gearing with the tire expansion.

I would say to gear up to closer to 30-32mph and with a little tire ballooning you'll be around high 30's. When you get better tires you can then gear back down to a 20-22T pinion.

The stock tire on my e-revo is in the garbage:lol: I've put half offset Ofna wheel with proline bowties MTR.
I've a Neu 1515 2.5d/f with 6s, gear 24/68 and i'am about in the 40/42mph range.
If i put y badlands on it, i switch for a 22T pinion to campansate for the extra .15" diameter and weight.:wink:

I'm going to ebay mine to some poor schmoo along with the titans, esc, radio and receiver.

Same motor/bat setup as me, but I dropped the spur to 62 to make use of the low-CG mount. I feel I could go up from 18/62 to 20/62 with now problems as well with the badlands tires. That puts me at the same ratio as you with th 22/68.

That just feels like a nice range for a MT. No need to try and go 50 in a truck..... More fun to go a little slower and use it on the bumps like it was made to do.