Save My Insanity!!

[RC-NUT]

Hey guys. I have a converted Savage X with a KD direct drive gen 2 tranny.

I need to choose a motor and I only want to use 4s. (My other RC's use 2s LiPo and I don't want to buy 3s packs just for this truck)

With that said I'm losing my mind with all of the choices and info I've read.

So far I like:
1. Castle 2650Kv
2. KD Revolver 7L 2450Kv (44 x 65mm can)

Am I on the right path or can you offer some suggestions please.

Thanks!

[magman]

castle 1717 would also work

[RC-NUT]

Now that's a 1580Kv correct? Would 4s be enough power? I noticed that motor is pretty beefy in size. (49mm x 85mm)

You'll have to pardon my ignorance. I have 22 years of RC under my belt but this brushless stuff has my head spinning!

[simplechamp]

The 1512 2650kv Castle is more of a buggy motor. I would go with a Castle 1518. Plenty of torque for a Savage and can still do just fine on 4S, and if you decide to go 5-6S later it can handle that too. Still available at the Castle sale for $65, can't beat that. You could get the 1520 or 1717 in the sale too if you decided to go BIG, but the 1518 seems like a good reasonable choice.

[RC-NUT]

Nice! Thank you. I just spent some time on the Castle site reading about those motors. Your right I can't beat that price.

If I were to stay with 4s can you tell me what the difference would be between the 1518 / 1520 / 1717? I'm guessing the 1518 you suggested would be a little faster because it has the highest Kv rating. I'm also guessing the other 2 motors would shine better with 5s or 6s?

Am I in the ball park? The 1717 is also physically larger so I wonder what effect that has?

[thzero]

On 4S? I'd go with a 1515 which is effectively what the Flux runs. A 1520 or 1717 you'd really have to gear up to get speed out of them on 4S. 1518 is probably a compromise as it requires less gearing but it is still closer to the 1520/1717 than the 1515. Run the numbers though Script Asylum's rc calc (http://scriptasylum.com/rc_speed/_top_speed.html) and see what the rough numbers come out too.

Originally Posted by RC-NUT

Nice! Thank you. I just spent some time on the Castle site reading about those motors. Your right I can't beat that price.

If I were to stay with 4s can you tell me what the difference would be between the 1518 / 1520 / 1717? I'm guessing the 1518 you suggested would be a little faster because it has the highest Kv rating. I'm also guessing the other 2 motors would shine better with 5s or 6s?

Am I in the ball park? The 1717 is also physically larger so I wonder what effect that has?

[RC-NUT]

Man that 1717 is a beast. I was just watching some video's on 6s.

I may have to buy the 1717 as well as something else.

[RC-NUT]

Castle 1518:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 49
Pinion Tooth Count: 18
Total Voltage: 14.8
Motor KV: 1800
Tire Diameter (inches): 5.5
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 2.72 : 1
Total Ratio: 9.00427 : 1
Tire Circumference (inches): 17.28 inches (438.88 mm)
Rollout: 1.92:1
Total Motor Speed: 26640 RPM
Vehicle Speed: 48.41 mph (77.76 km/h)
Effective KV Value: 1800
KT constant: 0.75 oz-in/A

[RC-NUT]

Castle 1717:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 49
Pinion Tooth Count: 18
Total Voltage: 14.8
Motor KV: 1580
Tire Diameter (inches): 5.5
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 2.72 : 1
Total Ratio: 9.00427 : 1
Tire Circumference (inches): 17.28 inches (438.88 mm)
Rollout: 1.92:1
Total Motor Speed: 23384 RPM
Vehicle Speed: 42.49 mph (68.26 km/h)
Effective KV Value: 1580
KT constant: 0.86 oz-in/A

[thzero]

2 for 1. :)

Originally Posted by RC-NUT

Man that 1717 is a beast. I was just watching some video's on 6s.

I may have to buy the 1717 as well as something else.

[RC-NUT]

Kershaw Designs is blowing out the 1717 for $179.00!!

I guess I can't argue with Castle for $70.00.

I have a feeling that speed calculator is not accurate for the simple fact I don't have the final gear radio of the KD direct drive tranny. They give the final ratios with a pinion and spur but not the tranny alone.

[lincpimp]

Motor speed is low on the 1518 on 4s. I would go with the 1515 2200kv for 4s. Your gearing will have to be very high on the 1518 on 4s and will pull alot of amps on startup. The 1518 is a 6s motor, as is the 1717. I have run all of them on 6s, including the 1515. 6s is where it is at 9ask your friens, boy!!!) but if you must run 4s go with the 1515 2200. Same motor the flux uses. Motor rpm needs to be in the mid 30k rpm range for good performace when gearing a heavy MT for 40+ mph.

This needs to be stickied. I vote for this to be stickied. Would someone near the RCM store please make a sign and picket for me, I will pay you back, promise.

[RC-NUT]

Crap. Well I placed my order yesterday for the 1518. Well I'll either spend some money on the 1515 or buy a couple of 3s packs. Probably batteries.

[Nard Cox]

Originally Posted by lincpimp

Motor speed is low on the 1518 on 4s... blabla ... Motor rpm needs to be in the mid 30k rpm range for good performace when gearing a heavy MT for 40+ mph.

I agree with the last part, so that's why 5S is also valid option (33.300rpm @ 3.7v). The 1520 and 1717 would be better off with 6S.

(very) General rule of thumb:
2200kV< = 4S
2000kv = 4S / 5S
1800kv = 5S / 6S
1600kv> = 6S

For some reason I don't like running things on the edge of their capabilities like 6S, though I think I'm going to with my 1717 in my Savy XL.

[RC-NUT]

You guys are killing me. So if I run 4s it's going to be a dog and 6s it's pushing it's limits at 39,000rpm.

What's misleading are the articles that are published on the Flux 2200 and the Flux 2350. People run the 2200 on 6s all day long and it's an animal. The 2350 is supposed to be a blast with 4s. With that said I was looking for a motor above 2200 so I could run 4s with lots of power. I was guided into a lower kv so I went with the 1800kv because it would be great on 4s and crazy on 6s. Now I'm either under powered or over powered.

I'm going to go buy a 1717 and just try both on 4s and 6s. Which ever one I don't care for I'll sell and try to break even.