Wraith Top Speed (Theoretical)?

[jonnycash]

Wraith Top Speed (Theoretical)

Just started into this hobby... start by calculating max top speed.

Theoretical? Certain limitations apply. Limitation may include road/trail conditions, mass (weight), supply, discharge (battery C), etc.

Example:
If an elephant sits on your wraith, no throttle push may possibly move your vehicle.

Here's my calculations....


Wraith Gearing:
20 - 28 - 52 - 13 - 38
^^^^^^^^^^^^ . ^^^^^^^
Transmission . . Axle

Stage 1 = 20:28 >> R1 = 28/20 = 1.4
Stage 2 = 28:52 >> R2 = 52/28 = 1.857142857
Stage 3 = 13:38 >> R3 = 38/13 = 2.923076923

My calculation:
Gear Ratio = 1 / (R1 x R2 x R3) = 0.131579

Axial Manual: ax90020-i002-wraith-kit.pdf
Page 41 reads 0.13 << matches my calculation.


Parameters for calculating vehicle speed:
=========================================
. . . . . . . Size : 1/10
. . . . Gear Ratio : 0.131579
. . . . . . . Spur : 80T
. . . . . . Pinion : 20T
. . . .Spur/Pinion : 4
. . . .Final Ratio : 30.4 . . (at wheel)
. . .Tire Diameter : 5.5 inch (2.2 Ripsaw Tires - R35)
Tire Circumference : 1.439897 ft


Using the values above to calculate vehicle top speed.
+--------------------------------------------------+
| Holmes Torquemaster Pro 540 | Vehicle speed (mph)|
| . . . . . . . . . . . . . . | . . . . . . . . . .|
| Motor| . .kV . .| . rpm at .| Wraith | Equivalent|
| Turn | rpm/volt | 7.4V (2S) | .1/10 .| Full-Size |
+------+----------+-----------+--------+-----------+
|. 10 .| . 6526 . |. 48292.4 .|. 25.99 | . 259.9 . |
|. 15 .| . 4317 . |. 31945.8 .|. 17.19 | . 171.9 . |
|. 17 .| . 3753 . |. 27772.2 .|. 14.95 | . 149.5 . |
|. 20 .| . 3216 . |. 23798.4 .|. 12.81 | . 128.1 . |
|. 21 .| . 3082 . |. 22806.8 .|. 12.28 | . 122.8 . |
|. 23 .| . 2790 . |. 20646.0 .|. 11.11 | . 111.1 . |
|. 25 .| . 2588 . |. 19151.2 .|. 10.31 | . 103.1 . |
|. 27 .| . 2100 . |. 15540.0 .| . 8.36 |. . 83.6 . |
|. 35 .| . 1565 . |. 11581.0 .| . 6.23 |. . 62.3 . |
|. 45 .| . 1210 . | . 8954.0 .| . 4.82 |. . 48.2 . |
|. 55 .|. . 987 . | . 7303.8 .| . 3.93 |. . 39.3 . |
|. 60 .|. . 837 . | . 6193.8 .| . 3.33 |. . 33.3 . |
+------+----------+-----------+--------+-----------+

* Using Torqemaster Pro 540 as basis;
Turn – rpm/volt values are from holmeshobbies.com
* Axial AX24003 20T Motor may not have the same kV values.


The formula:
============
Circumference = pi x Diameter; where pi = 3.14159265358979.....
Final Ratio at wheel = 1/(Pinion/Spur x 0.13)
Wraith speed in mph = (rpm @7.4V / Final Ratio) x Tire Circumference / 88

What is "88"?? Conversion: 1 mph = 88 ft/minute


Nomenclature:
=============
rpm = rounds per minute
mph = miles per hour
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[jonnycash]

Battery = 2S (7.4V) table.

Battery = 2S (7.4V) Table
+-----------------+-------------------------------------------------------+
|TorqueMaster Pro | . . Wraith Speed (mph) for each Spur/Pinion Ratio . . |
| . . . . . . . . | . . . . . . . . . . . . . . . . . . . . . . . . . . . |
| Turn | rpm/volt |. 3.50 |. 4.00 |. 4.50 |. 5.00 |. 5.50 |. 6.00 |. 6.50 |
+------+----------+-------+-------+-------+-------+-------+-------+-------+
|. 10 .| . 6526 . | 29.71 | 25.99 | 23.10 | 20.79 | 18.90 | 17.33 | 16.00 |
|. 15 .| . 4317 . | 19.65 | 17.19 | 15.28 | 13.76 | 12.51 | 11.46 | 10.58 |
|. 17 .| . 3753 . | 17.08 | 14.95 | 13.29 | 11.96 | 10.87 |. 9.97 |. 9.20 |
|. 20 .| . 3216 . | 14.64 | 12.81 | 11.39 | 10.25 |. 9.32 |. 8.54 |. 7.88 |
|. 21 .| . 3082 . | 14.03 | 12.28 | 10.91 |. 9.82 |. 8.93 |. 8.18 |. 7.55 |
|. 25 .| . 2588 . | 11.78 | 10.31 |. 9.16 |. 8.25 |. 7.50 |. 6.87 |. 6.34 |
|. 27 .| . 2100 . |. 9.56 |. 8.36 |. 7.43 |. 6.69 |. 6.08 |. 5.58 |. 5.15 |
|. 35 .| . 1565 . |. 7.12 |. 6.23 |. 5.54 |. 4.99 |. 4.53 |. 4.16 |. 3.84 |
|. 45 .| . 1210 . |. 5.51 |. 4.82 |. 4.28 |. 3.86 |. 3.51 |. 3.21 |. 2.97 |
|. 55 .| .. 987 . |. 4.49 |. 3.93 |. 3.49 |. 3.14 |. 2.86 |. 2.62 |. 2.42 |
|. 60 .| .. 837 . |. 3.81 |. 3.33 |. 2.96 |. 2.67 |. 2.42 |. 2.22 |. 2.05 |
+------+----------+-------+-------+-------+-------+-------+-------+-------+

Notes:
======
1. Using Torqemaster Pro 540 as basis;
.. Turn – rpm/volt values are from holmeshobbies.com
2. Equivalent size? Multiple by 10.
.. Example: 20.79 ==> 207.9 mph at full-size.

Ratio example:
Spur = 54T; Pinion = 12T
Spur/Pinion Ratio = 54/12 = 4.5 Motor kV=3082, speed = 10.91 mph.

 

[jonnycash]

Battery = 3S (11.1V) Table

Battery = 3S (11.1V) Table
+-----------------+-------------------------------------------------------+
|TorqueMaster Pro | . . Wraith Speed (mph) for each Spur/Pinion Ratio . . |
| . . . . . . . . | . . . . . . . . . . . . . . . . . . . . . . . . . . . |
| Turn | rpm/volt |. 3.50 |. 4.00 |. 4.50 |. 5.00 |. 5.50 |. 6.00 |. 6.50 |
+------+----------+-------+-------+-------+-------+-------+-------+-------+
|. 10 .| . 6526 . | 44.56 | 38.99 | 34.66 | 31.19 | 28.36 | 25.99 | 23.99 |
|. 15 .| . 4317 . | 29.48 | 25.79 | 22.93 | 20.63 | 18.76 | 17.19 | 15.87 |
|. 17 .| . 3753 . | 25.63 | 22.42 | 19.93 | 17.94 | 16.31 | 14.95 | 13.80 |
|. 20 .| . 3216 . | 21.96 | 19.21 | 17.08 | 15.37 | 13.97 | 12.81 | 11.82 |
|. 21 .| . 3082 . | 21.04 | 18.41 | 16.37 | 14.73 | 13.39 | 12.28 | 11.33 |
|. 25 .| . 2588 . | 17.67 | 15.46 | 13.74 | 12.37 | 11.25 | 10.31 |. 9.52 |
|. 27 .| . 2100 . | 14.34 | 12.55 | 11.15 | 10.04 |. 9.12 |. 8.36 |. 7.72 |
|. 35 .| . 1565 . | 10.69 |. 9.35 |. 8.31 |. 7.48 |. 6.80 |. 6.23 |. 5.75 |
|. 45 .| . 1210 . |. 8.26 |. 7.23 |. 6.43 |. 5.78 |. 5.26 |. 4.82 |. 4.45 |
|. 55 .| .. 987 . |. 6.74 |. 5.90 |. 5.24 |. 4.72 |. 4.29 |. 3.93 |. 3.63 |
|. 60 .| .. 837 . |. 5.71 |. 5.00 |. 4.44 |. 4.00 |. 3.64 |. 3.33 |. 3.08 |
+------+----------+-------+-------+-------+-------+-------+-------+-------+

Notes:
======
1. Using Torqemaster Pro 540 as basis;
.. Turn – rpm/volt values are from holmeshobbies.com

 

[jonnycash]

References

References:

1. Speed test, done by RCCrawler at Vimeo:
Stock Axial Wraith speed test on Vimeo

2. Axial Wraith Kit doc:
http://docs.axialracing.com/instructions/ax90020-i002-wraith-kit.pdf

3. Holmes TorqueMaster Pro 540:
http://www.rccrawler.com/forum/holm...emaster-pro-handwound-brushed-540-motors.html

 

[jonnycash]

Average Human Walking speed = 4mph (google search).

I would like to ask... for trailing and some climbing, what should my Wraith max speed be?
How about between 5 and 6 mph?? Walking... 4 mph will be something like 80% throttle push for 5 mph max.

Then, I can choose my motor Turn, then Pinion/Spur accordingly.

A post has written 4 mph (max) being too slow. The posting indicated HH Expert 35T; Spur/Pinion = 80/17 = 4.71

For real size vehicle, what is typical trailing speed??

Any insights to this "comfortable" trailing speed will be greatly appreciated.



Thanks!!

 

[johnnyh66]

1:1 depends on the trail I'd say, somewhere between idle and a few mph most of the time... unless it's muddy or other loose traction situation then you'd need more speed... just like in 1:10.

5mph is good most of the time but sometimes you need that extra little bump to get over/up an obstacle.

 

[Plush]

This should go as a sticky..