Pure Brainstorming. Outrunner experts HELP!

[trev3813]

So i have this Rs4 mt2 roller sitting here. Looking at some of the Crt.5 Outrunner builds. ok, seems pretty cool. I have a sidewinder esc, and a Spc 4600 6 cell, and upgrading to lipos soon. Looking for a mild, torquey setup. Any help?

[Metallover]

An outrunner would work great. Lots of low end and very efficient. You will want a 36mm outside diameter motor most likely. That is standard 540 motor size. The hardest part for my build was finding the right length dogbones.

I would look on hobbycity for a cheap motor that will give good power and get you what you want for the price you want. Otherwise you could look at axi, scorpion, and all those quuality manufactures and look at their selection. My motor was around $35.

[trev3813]

ok, 36 mm. if im running 2s to 3s lipo, what kv should i be looking around?

[Metallover]

I'd say 1000-1500 for just 2-3s. I used a 1100kv motor and with stock 3.2" tires it will run really fast on 4s and great on 3s. Someone else used a 1000 kv motor and I think he runs 4s.

Use mikes speed calculator. Put in your diff ratio and all the other inrunner stuff as 1. http://www.scriptasylum.com/rc_speed/_top_speed.html

Differential Ratio: 3.25
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 1
Pinion Tooth Count: 1
Total Voltage: 11.1
Motor KV: 1100
Tire Diameter (inches): 3.2
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0
Spur/Pinion Ratio: 1 : 1
Total Ratio: 3.25 : 1
Tire Circumference (inches): 10.05 inches (255.35 mm)
Total Motor Speed: 12210 RPM
Vehicle Speed: 35.77 mph (57.45 km/h)
Effective KV Value: 1100
KT constant: 1.23 oz-in/A

This is what I got running stock tires on 3s. I can run 4s with the same tires. I'll try running 3 and 4s with my new proline gladiators (m2 compound, these tires recommended) next week once I get rims and some micellaneous stuff. I'll really be pushing the limits of this motor.

[MetalMan]

Outrunners are excellent choices for lower-budget setups. For your truck, we shall determine a good kv.

Plugging the numbers into BrianG's "Parameter Solver"
Differential Ratio: 38/13 (2.923)
Transmission Ratio: 1
Spur: 1
Pinion: 1
Voltage: 7.2v (although I would use something more like 7.0v just to better estimate the loading on the battery)
Motor: leave blank, this value is what you want to find out
Tire diameter: depends on the tires you use obviously, but in general 1/10 trucks use 4" tall tires
Top speed: something like 30-35mph should be about right for a 4wd 1/10 on 6 cells

The result: a kv of ~1200 would be great.

As Metallover said, a 36mm OD is a good choice. In terms of outrunner specifications, that would mean the motor will have a stator diameter of about 28mm. As for stator length, I think 26mm should be good.
For example, the Axi 2826/8:
http://www3.towerhobbies.com/cgi-bin...?&I=LXPPX5&P=7
Its kv at 1130 is a bit on the low end for 6 cells, though.

From Hobby City, this:
http://www.hobbycity.com/hobbycity/s...r_Eq:_AXi_2826
Only problem with that is the 4mm shaft, where 5mm is more standard. 5mm is also the inner diameter of the drive cups that the dogbones go into.

[Metallover]

I got pretty much the same hobbycity motor that brian pointed out. The only differences are the 5mm shaft (good) and it supposedly has more power and is more efficient.(good) It does cost about $6 more though. (bad)

http://www.hobbycity.com/hobbycity/s...idproduct=7392

[trev3813]

1200 kv, 28mm, got it. Thanks guys, i'll be on the hunt! And thanks for the links. They help. So i'll be able to use the Sidewinder with the outrunner too?

[BL_RV0]

4mm shaft is not a problem, Mike sells a bore reducer for 4mm shafts --> 5mm pinions.
http://www.rc-monster.com/proddetail...rod=RCMreducer

[BL_RV0]

Originally Posted by trev3813

1200 kv, 28mm, got it. Thanks guys, i'll be on the hunt! And thanks for the links. They help. So i'll be able to use the Sidewinder with the outrunner too?

Yep, sidewinder works great with outrunners. Very smooth.

[trev3813]

No worries, as Metallover pointed out, http://www.hobbycity.com/hobbycity/s...idProduct=7392 has a 5mm shaft. but good thinking if i use the other motor. Awesome, the sidewinder will work!

[Metallover]

Originally Posted by trev3813

1200 kv, 28mm, got it. Thanks guys, i'll be on the hunt! And thanks for the links. They help. So i'll be able to use the Sidewinder with the outrunner too?

Sidewinder will work. My MM works flawlessly and I'm sure the Sidewinder will do the same. I don't know anyone who has done it off the top of my he.....

Wait! Htere are a bunch of people who use the sidewinder and outrunners in their crawlers. Oh yeah. I'm the best.

[trev3813]

haha, ok, looks like i will be able to salvage the rs4. I better get to work putting it back together.

[Metallover]

If you want to get a new 3s lipo -
$40 20c 5k mah http://www.hobbycity.com/hobbycity/s...idProduct=8579
$50 25c 5k mah http://www.hobbycity.com/hobbycity/s...idProduct=8583

You could probably get ~5-8 min runtimes with a battery like this
20c 2200mah http://www.hobbycity.com/hobbycity/s...idProduct=6306