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Savage XL outrunner conversion
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DanteX
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Talking Savage XL outrunner conversion - 02.16.2010, 05:42 PM

Hi there

I got interested about a direct drive conversion for my savage xl.

so i am looking for a suitable outrunner bl motor.
the problem is that you have to pick the right one for your conversion because of the kv rating.

i am running 4s 5000mAh and a 100A hobbkying car esc.

Well, i choose a few different types:
1st: this one *klick* with 580kv

and here the speed calculation:
Quote:
Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 1
Pinion Tooth Count: 1
Total Voltage: 16.8
Motor KV: 580
Tire Diameter (inches): 5.91
Tire Ballooning (inches): 0.5
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 1 : 1
Total Ratio: 3.30769 : 1
Tire Circumference (inches): 21.71 inches (551.39 mm)
Rollout: 6.56:1
Total Motor Speed: 9744 RPM
Vehicle Speed: 60.56 mph (97.28 km/h)
Effective KV Value: 580
KT constant: 2.33 oz-in/A
2nd: this one *klick*
with 380kv

here the results:
Quote:
Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 1
Pinion Tooth Count: 1
Total Voltage: 16.8
Motor KV: 380
Tire Diameter (inches): 5.91
Tire Ballooning (inches): 0.5
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 1 : 1
Total Ratio: 3.30769 : 1
Tire Circumference (inches): 21.71 inches (551.39 mm)
Rollout: 6.56:1
Total Motor Speed: 6384 RPM
Vehicle Speed: 39.68 mph (63.73 km/h)
Effective KV Value: 380
KT constant: 3.56 oz-in/A
3rd: this one *klick*

results:
Quote:
Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 1
Pinion Tooth Count: 1
Total Voltage: 16.8
Motor KV: 400
Tire Diameter (inches): 5.91
Tire Ballooning (inches): 0.5
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 1 : 1
Total Ratio: 3.30769 : 1
Tire Circumference (inches): 21.71 inches (551.39 mm)
Rollout: 6.56:1
Total Motor Speed: 6720 RPM
Vehicle Speed: 41.76 mph (67.09 km/h)
Effective KV Value: 400
KT constant: 3.38 oz-in/A
Tell me what u think is the best joice.

Thanks
Regards, DanteX (Andy)
   
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bruce750i
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02.17.2010, 01:20 PM

IMO 60 mph is pretty fast for something that big on 4s. I would use the 400kv at 41mph.
   
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DanteX
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02.17.2010, 02:04 PM

Yes, i totally agree with you, 41mph is enough.


I Will order from hobbyking saturday or sunday.

I will keep you guys updated!
   
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bruce750i
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02.17.2010, 03:13 PM

Cool, it will be something different!
   
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Desmo
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03.07.2010, 09:28 PM

I have an LST direct drive. I went thru 3 hobbyking motors before I got an AXI. You will want as low a kv as you can get and plan on 6s.



old pic, its changed a few times since then

Last edited by Desmo; 03.07.2010 at 09:43 PM.
   
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DanteX
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03.09.2010, 05:58 PM

Nice conversion.
I have to plan on 4S because i would need a new ESC for using 6S.

I recently bought a used Revo that will be converted to BL.
So this project has to wait until i have to order something from hobbyking.
   
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suicideneil
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03.09.2010, 07:32 PM

You'll need a new esc then. You'll need a motor with a high kv ( relatively speaking) to run 4s, and that means more current draw, especially from a standstill- cogging may become a problem is your esc isnt able to be adjusted for multiple pole outrunners...
   
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Desmo
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03.09.2010, 09:45 PM

here is how it is now.







You'll need a low KV motor and 6s or more to get it going. I tried 4s first since I already had the batteries. Smoked that motor in less than 2min. Then I went 6s and lower kv and the next motor lasted 10min. The axi with a fan is ok but it needs to be a lower kv (4130/16) or a bigger/longer motor. I even swapped the diff gears out for the muggy gears which are a lower ratio. The MGM esc cogs pretty bad and needs to go back to a dead stop allot. The MMM only cogs alittle and almost never needs to restart. once its moving it has the power to wheelie the truck on its roof.
   
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DanteX
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03.10.2010, 10:57 AM

6S? -> So i guess i have to buy a MMM or so.
Oh, no, i have to make a new battery tray when using 6S, now it is bent aluminium with foam inside for protection.


@Desmo: nice ride and thx for the pics :)

Last edited by DanteX; 03.10.2010 at 12:28 PM.
   
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Nick
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03.10.2010, 02:10 PM

Hey guys, found this a really interesting thread.

So I assume you'd need a low KV as it requires a lot more power to get the car moving being direct drive.

Quessies!
  1. How do you put the driveshaft on the back end of the motor?
  2. What are the benefits?
  3. With 300-400kv motors they must be excellent runtime and maintain very low amps?


~ Nick.

Last edited by Nick; 03.10.2010 at 02:26 PM.
   
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lincpimp
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03.10.2010, 02:48 PM

If you can get them to startup properly you will be ok.

Most outrunners have a shaft that can be pressed to stick out the front and back. That way you can install a cup for the dogbones on each end.

6s is the way to go, and I can recommend axi as a good motor choice. I have a few of the 28 and 41 series outrunners and they do very well.
   
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DanteX
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03.10.2010, 03:07 PM

@Nick:

Like lincpimp already said, you can press the shaft out, but i have to measure the diameter of the drive shaft on the stock savage transmission.

If the diameter is not the same i have to turn it down to the right measures.

I planned this conversion because of
  • the low center of gravity,
  • less gears (-> less abrasion),
  • more space in the frame for battery and electrics
  • and good looking

I have two (soon 3 with Revo conversion) projects going on, the savage and my scale crawler (ax10 with rc4wd wheels and blazer body...) and thats why i have to save the money for goodies like a good (or better) esc.


regards, DanteX

Last edited by DanteX; 03.10.2010 at 03:09 PM.
   
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Desmo
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03.10.2010, 10:48 PM

I think the drive cups I used on the axi motor are from a savage.



   
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fastlane01
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03.11.2010, 12:38 AM

that's a bad aaa lookin set up. Is that a nitro conversion? of course I know it's home modified.
   
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Desmo
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03.11.2010, 10:56 AM

Home made, it was missing the tranny and the main plate was cut up already so it wasn't a big deal to cut it up some more. Only the main chassis plate is modified.
   
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brushless, center, outrunner, savage, savage xl


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