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danidani
12-01-2011, 06:55 AM
Dear friends, I wrote from Italy.
I am a traxxas fan :)
Sorry if I open a duplicated thread but I did some calculations in order to find the theoretical max speed of this special car.
I considered
pinion 34
spur 46
tires diameter 4,29''
motor 1650 kv
nominal voltage 22,2 V
overal drive ratio 9,36
With this parameters I found a speed max of 80 kph

Instead considering an overall drive ratio of 3,459 I found 161 kph (+100 mph)
Where is my mistake?

Thank you so much for your help
dani

tbonemcniel
12-01-2011, 06:58 AM
Differential ratio of 2.85?

danidani
12-01-2011, 07:14 AM
hi tbonemcniel, thank you for your reply. I have the traxxas e-revo 5608 and considering an Overall Drive Ratio: *18.83 (stock, out-of-box) , I obtain 18.83/(65/18)=> reduction ratio 5,214 and I found the correct max speed of my e-revo. Well...
Anyway, Overall Drive Ratio =18,83 for e-revo is a total drive ratio considering also the differential ratio (please tell me if I write something wrong).
In other words I thinked the declared value Overall Drive Ratio parameter for x0-1 could be the total drive ratio as declared in the datasheet....

ksb51rl
12-01-2011, 09:28 AM
Using a maximum voltage of 25.2 volts, I find a maximum theoretical velocity of 137.81 mph or 221.38 km/h.
Why would you use nominal voltage?

danidani
12-01-2011, 10:04 AM
I could to use 25,2 (max voltage) ok but the result could not to change significantly.
Anyway, can you please explain me as you obtained this value? Thanks

tbonemcniel
12-01-2011, 10:04 AM
Ignoring all this talk of final drive, but instead using a diff ratio of 2.846, pinion/spur of 34/46, 3.7v per cell at 6 cell, 1650kv motor, with a 4.29" tall tire (no ballooning taken into account, hopefully true with this belted tire), I got a theoretical max speed of 121mph. Using max Lipo voltage I get 138mph.

Does this help you any?

danidani
12-01-2011, 10:14 AM
Yes, using 2.846 as reduction ratio I found 138 mph :) . Anyway I don't understand why in the datasheet is reported Overall Drive Ratio: *9.36 not 2,846....

ksb51rl
12-01-2011, 10:20 AM
I believe the problem may be in the transmission. The XO-1 does not have one. The only way I can arrive at close to an 80 km/h terminal velocity is to use a Revo second gear ratio instead of the correct transmission ratio of 1:1.
Another possibility:
9.36 ratio is with stock gearing, not 34/46. Traxxas claims 50 mph or 80 km/h with this gearing. Does this sound familiar? :)

danidani
12-01-2011, 10:31 AM
yes now is all clear :) thank you so much :)

ducati777
12-01-2011, 11:20 AM
9.36 INCLUDES the diff, and p/spur.... Also I agree with nominal voltage, you can't assume your batteries are going to hold 25.2 volts at full throttle.

Thus you're doubling your reduction in the math.

I did the same thing yesterday, figured it'll do 50 mph stock. Plenty for bashing. But then if you want, you can up the gearing, unlock the ESC and have at it....

It just seems like people expect this car to burst out of the packaging at 100 mph if you just look at it. Its not that easy....