Savage XL outrunner conversion
 

Hi there :na:

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:
2nd: this one *klick*
with 380kv

here the results:
3rd: this one *klick*

results:
Tell me what u think is the best joice. :rules:

Thanks
Regards, DanteX (Andy)

IMO 60 mph is pretty fast for something that big on 4s. I would use the 400kv at 41mph.

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


I Will order from hobbyking saturday or sunday.

I will keep you guys updated!

Cool, it will be something different!

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.

http://home.surewest.net/~myoldjunk2...b/CIMG4017.JPG

old pic, its changed a few times since then

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.

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...

here is how it is now.

http://home.surewest.net/~myoldjunk2...b/CIMG1988.JPG

http://home.surewest.net/~myoldjunk2...b/CIMG1989.JPG

http://home.surewest.net/~myoldjunk2...b/CIMG1990.JPG

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.

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 :)

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! :rofl:

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?

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.

@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 :yipi:

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. :neutral:


regards, DanteX

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

http://home.surewest.net/~myoldjunk2...b/CIMG1991.JPG

http://home.surewest.net/~myoldjunk2...b/CIMG1992.JPG

that's a bad aaa lookin set up. Is that a nitro conversion? of course I know it's home modified.

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.

*Update*

I received the outrunner today, and it is bigger than i thought.
But it fits pretty good actually.

I started to look for an aluminum motor mount and i finally cut an old rc chassis to fit.
I bent it and drilled the holes (there were holes before too :lol: )
And here are few pics:

Before:
http://www.abload.de/img/dscn16557snc.jpg

Motor comparison: the can-motor used before and the outrunner

http://www.abload.de/img/dscn1654jolr.jpg

Then a picture after my work:

http://www.abload.de/img/dscn1656gsh2.jpg

And some detail-shots:

http://www.abload.de/img/dscn1658mr2z.jpg
http://www.abload.de/img/dscn1657jqlg.jpg
The bending looks way more worse and it really is. :whistle:

Thats all for now!

Regards, Andy :yipi:

Intresting project for sure:). Just a question, I thought the outrunner would be at least as long as the can motor? and doesn´t grass and stuff get stuck in/on the motor?:angel:

Keep up the good work! :whip:

Yes, indeed i have to think about an appropriate dust protection and cooling solution.

Why did you think so?


Q: Would it be enough if i cut a notch into the shaft of the motor instead of a end-to-end drill-hole?

Thanks
Regards, DanteX

It just felt like with a directdrive system you would be in need of a HUGE amount of torque to get the rig moving without too much cogging, and i was thinking "longer motor, more torq" so I´ve got suprised when I saw how short it was:whip:

Next week i will see how it performs and then tell you if it worked :)

Happy Easter!

Sounds good. Happy easter on you too:yipi:

If by notch you mean a flat spot to attach the drive cups, that'll work fine- maybe add a little dimple too for the setscrew to bite into.

Thanks, thats what i was talking of.

I will try it like you said!

WTF?!

Well, a few minutes ago i completed the reassembly of the savage and i did a test drive.

But this thing has no power. It can barely get speed.

If i let the wheels spin freely it balloons that much.

I think there was something wrong with the scriptasylum calculation.
I had to stop the test because the motor got almost too hot.

Any suggestions for improvement?

we put that exact same motor in an emaxx, just some advise, take it apart and reshrink the stator leads and then ca them down, or the motor will eat them for lunch

its going to cogg:lol:

its not the length it the diameter that makes a big diffrence in torque with outrunners, to not cogg you would need an outrunnertwice that size

The values you used in the calculations are correct, but physics makes the calculated speed impossible with this setup.

Look at your rollout values, they are over 6:1. This means for every 1 turn of the motor the wheel will roll 6 inches, which is WAY too much. Should be closer to between 1:1 and 2:1.

With that high rollout you will have no torque at all, even with a low-kv torque heavy motor, because there just isn't enough gear reduction. That would explain why if you pick it up off the ground and let it freewheel in the air the tires might balloon huge, but once the motor is loaded up with the truck on the ground it can't get up to speed. It would also explain why the motor got so hot.

what kv motor did you get?


we were geared for 40mph and it spun the wheels all the way to 30 on 5cell..........just didnt last long

Was the E-maxx direct drive though? You probably had a pinion/spur and transmission which all lowered the gearing.

no it was direct drive, let me see if i can find pictures for you

Differential Ratio: 3.3076923076923075 (Lst 2 Diffs)
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 1
Pinion Tooth Count: 1
Total Voltage: 18.5
Motor KV: 380
Tire Diameter (inches): 5.75
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 1 : 1
Total Ratio: 3.30769 : 1
Tire Circumference (inches): 18.06 inches (458.83 mm)
Rollout: 5.46:1
Total Motor Speed: 7030 RPM
Vehicle Speed: 36.36 mph (58.4 km/h)
Effective KV Value: 380
KT constant: 3.56 oz-in/A

Yeah I'd like to see that. Can't believe it would have enough torque at such a high rollout.

Here are a few pcis of the car and a short video:
http://www.abload.de/img/dscn1803g66i.jpg
http://www.abload.de/img/dscn180155aa.jpg
http://www.abload.de/img/dscn180225a8.jpg

Heres the video:

http://www.youtube.com/watch?v=MQDTGWeYi48
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Seems pretty quick to me. Given your description before I thought it would be much slower. Still have some concern about that rollout though. Going to need a motor with more torque to have a cool running setup. Also maybe look at lower kv, higher voltage.

Very nice!! Like you said though too slow and not enough torque. I love reading about outrunner projects!!

DanteX, how much does it weight?

If you bought a controller for 8s, I think this motor would work very well in your conversion. (If it fits) Turnigy Aerodrive XP 63-64 230kV The motor shaft is 10mm so you would probably need to turn it down, but otherwise it should have plenty of torque. Same RPM, same rollout, same speed- higher voltage, more torque, greater efficiency.

The whole thing with the time zones suck because while i am asleep you reply and i can read it next day. :(

@ Desmo: The car weighs 4,9kg (10.8lbs) RTR.

@What's_nitro?: I already bought a nice controller that can handle um to 12S Lipo and 100A! Yeah :)

But i dont want to spend so much money on a new motor. I probably will design a center diff drive for my savage or continue this build:http://www.rc-monster.com/forum/showthread.php?t=25375

Or i will buy this 5t body and strech the xl out :)
http://www.rc-fellas.com/product_inf...roducts_id=287

What do you think?

regards, DanteX

A much larger and lower kv motor should help. But I think as with my LST its to heavy. The best setup is some gear reduction. You can still use a outrunner but it just needs to be geared down. I think I'm going to put a center diff in my lst.

How would you be able to mount the output shaft on the back of this motor?

I would be interested to do a savage 8s outrunner with this and the HC 8s-12s