1/6 Losi Hummer (CC1717) Build

[brian015]

1/6 Losi Hummer (CC1717) Build

With Castle selling their 1717’s for a bargain recently, I decided to plan a build that would make the most of one of these motors:




Since the 1717 is almost as large (20oz) as my Neu 1527 (21.8oz), I figured I could plan another larger-scale build in the 16-20lb range. I again will make use of the Losi LST2/Muggy platform because I have seen that it is quite capable in a truck this size. If you haven’t seen it, here’s my previous large-scale build:

http://www.rc-monster.com/forum/showthread.php?t=26979

The first thing I had to consider with the 1717 is that it has a relatively high kv and a larger diameter than the 15-series. For both of these reasons, I looked for a center diff with a larger spur gear and decided on the AE RC8T that comes with a 54t spur. I want to have gearing options for 6s-8s and for both MT and 1/5 scale tires. Playing with the top-speed estimator, I was happy with the gearing options available with the 54t spur. For example, with 1/5 scale tires and running on 8s, I could use a 12t pinion and get a top speed around 51mph (I’ll be running 45/11 Muggy diffs):

Differential Ratio: 4.090909090909091
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 54
Pinion Tooth Count: 12
Total Voltage: 29.60
Motor KV: 1580
Tire Diameter (inches): 6.8
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 4.5 : 1
Total Ratio: 18.40909 : 1
Tire Circumference (inches): 21.36 inches (542.62 mm)
Rollout: 1.16:1
Total Motor Speed: 46768 RPM
Vehicle Speed: 51.39 mph (82.56 km/h)
Effective KV Value: 1580
KT constant: 0.86 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...


Or, with MT Badlands on 6s, I could use a 19t pinion and get a top speed of 52mph:

Differential Ratio: 4.090909090909091
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 54
Pinion Tooth Count: 19
Total Voltage: 22.20
Motor KV: 1580
Tire Diameter (inches): 5.84
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 2.84 : 1
Total Ratio: 11.62679 : 1
Tire Circumference (inches): 18.35 inches (466.01 mm)
Rollout: 1.58:1
Total Motor Speed: 35076 RPM
Vehicle Speed: 52.41 mph (84.2 km/h)
Effective KV Value: 1580
KT constant: 0.86 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...

And therefore, any setup I’d want to use with this would be possible with pinions in the range 12-20t. I know that 8s puts the 1717 slightly over its max rpm of 45,000 – but others have been doing it, so I’ll possibly give it a try.

I’d like to have reverse and esc braking, so I’ll either run 6s through a MMM or pick up a Mamba XL to run either 6s or 8s.


Next, I looked into various bodies for this and found myself looking at extra large 1/8 scale or 1/6 scale bodies with wheelbases from 16-18 inches. I don’t want to go as large as 1/5 scale with this because it would likely become too heavy for the 1717. I really liked the FG Jeep body, but found that it is currently unavailable in the US. Since I wanted to do something a little different than a pick-up body, I settled on the FG Hummer body. I like the size and the look of it. It has a wheelbase of 17.5 inches, so that’s the wheelbase I’ll build my truck to have:



The FG truck itself with the Hummer body definitely has the monster truck look with very large tires and a wide stance:



I’m thinking right now of setting mine up initially at least with a more scale-size tire look. I’ve mocked it up with MT Badlands:




I might end up going with larger tires, but we’ll see.

Anyway, that’s the start of this project – I’m in no hurry with it, but hopefully will have it done sometime this summer to be able to run it in the nice weather.