Project outrunner e-savage

[Pedebeater]

I was inspired to do something like this by a friend who has an outrunner warhead (Takedown). He helped me out a lot with picking out the right motors. If I did this I would be using it as a direct drive setup. So I would not have to use the center tranny. Using outrunners can have many advantages. Such as loads of torque while still having amazing top end speed, efficiency, and less heat.

Here they are!
http://www.hobbycity.com/hobbycity/s...idProduct=4658

http://www.hobbycity.com/hobbycity/s...idProduct=4912

I would also like to know more information on outrunners in general. Like should I be basing my decision mainly on length or width?



I have not seen this done to a e-savage yet and would love to do something new. So please let me know what you think.

[Takedown]

Finally you got this posted! Took you awhile to get accepted. Anyways, when do you plan to order "a motor"? I would like to know so I will know how much time Ill have to do some research for you. The turnigy 42-40B 900kv looks great. I have the 50-55 600kv and I love it. I just got done making my motor mount and will shoot you some pics later.

Good luck on the build!

[suicideneil]

I would be inclined to say take a look at Sike, Linc and BL powers threads- mucho info to be gleaned.

[Takedown]

Originally Posted by suicideneil

I would be inclined to say take a look at Sike, Linc and BL powers threads- mucho info to be gleaned.

Yep I would reccomend you talk to Sike. He is such a help. He's somewhat guiding me threw my warhead build.

[Pedebeater]

Thank you for all of the responses, i will be sure to talk to sike. As for "when" it might be a while, gotta prepare my truck before I get the motor. I also think that Turnigy 42-40 900kv looks great.


Thank you for all of the suggestions and please keep them coming.

[lincpimp]

I would first decide what battery and esc you will use. This will determine what motor (kv) you will need. I would say that the 42-40 looks good, but at 900kv ma be a bit too fast. Overall truck speed of around 40mph is good to aim for. Much more and it becomes difficult to drive. Also keep in mind that your only method of altering speed will be changing tire height. You may be able to change the diff ratio, I ma not too familiar with the e-savage. Generally a longer stator will offer more torque than a shorter one. And a smaller diameter motor will spin up faster than a larger diameter. The 40mm (or so) diamter outrunner seem to be the best choice for a 10th scale mt direct drive setup. Most have 6mm shafts, as do most center driveshaft, like the revo sliders, so installing them is easier. Also motor weight is a consideration, as JRH mentioned in another thread. A lighter motor is not necessarily a good thing for this application.

To sum it all up, a good match of battery, esc, and motor is required and more though is required to get this. Not as easy as just picking something and figuring out the gearing to make it work!

[sikeston34m]

Wow, this kinda thing seems to be catching on!

[sikeston34m]

Originally Posted by Pedebeater

I was inspired to do something like this by a friend who has an outrunner warhead (Takedown). He helped me out a lot with picking out the right motors. If I did this I would be using it as a direct drive setup. So I would not have to use the center tranny. Using outrunners can have many advantages. Such as loads of torque while still having amazing top end speed, efficiency, and less heat.

Here they are!
http://www.hobbycity.com/hobbycity/s...idProduct=4658

http://www.hobbycity.com/hobbycity/s...idProduct=4912

I would also like to know more information on outrunners in general. Like should I be basing my decision mainly on length or width?



I have not seen this done to a e-savage yet and would love to do something new. So please let me know what you think.

IMO, both of those outrunners are too small to go Direct Drive with.

Gotta keep in mind the size of the load that you're asking this to start up under. Weight of the truck and the gearing + tire size you're going to use.

What gear ratio does your Savage use? Tire Size? Vehicle Weight?

As a general rule of thumb, here's how the power output of outrunner vary..

Higher kv = lower torque
Lower kv = higher torque
Large stator diameter = lower kv + higher torque
Longer stator length = lower kv + higher torque

If you go too high with the kv, you will have startup cogging and over heating. I would suggest somewhere between 400kv and 700kv for Direct Drive.

It's a balancing act to choose the right motor for the application.

Choose something with at least a 40mm stator diameter and at least a 20mm stator length.

Neo magnets make more power also.

[Takedown]

Sike, the motor's chosen their are actually going to be overkill because their both equivalent to .30 glow engines. Thats more than the stock savage X. That is going to really push the e-savage to its limits.

[sikeston34m]

Originally Posted by Takedown

Sike, the motor's chosen their are actually going to be overkill because their both equivalent to .30 glow engines. Thats more than the stock savage X. That is going to really push the e-savage to its limits.

Overkill? If that's what you want to believe, you will be going through alot of motors.

It doesn't matter what their "glow engine" equal is advertised as being. A Glow engine setup has a clutch and this type doesn't.

These are Delta wound motors, and if the case diameter isn't at least in the 50mm range, then it isn't large enough in Diameter to produce the necessary torque to start in a Direct Drive Application. If you want to run through a gear box for some added gear reduction, then we can talk smaller outrunners.

Added gear reduction multiplies the torque and helps remove the resistive load from the motor.

A smaller higher kv motor will burn up quickly.

I don't mean to sound rude, but I've tested different motors for over a year now. The experience I have, didn't come without burning a few up.

Direct Drive is very demanding in the motor/ESC department.

Since a typical diff is going to have something like a 3.85:1 gear ratio. Combine that with a 5.75" diameter tire. You're talking about 4 1/2" of vehicle travel for EACH turn of the motor. It is true that outrunners make 5 to 7 times the torque of a comparable size inrunner, BUT this amount of vehicle roll per revolution is a huge load.

Again I say, 40mm stator diameter and at least 20mm in stator length.

[Takedown]

Originally Posted by sikeston34m

Overkill? If that's what you want to believe, you will be going through alot of motors.

It doesn't matter what their "glow engine" equal is advertised as being. A Glow engine setup has a clutch and this type doesn't.

These are Delta wound motors, and if the case diameter isn't at least in the 50mm range, then it isn't large enough in Diameter to produce the necessary torque to start in a Direct Drive Application. If you want to run through a gear box for some added gear reduction, then we can talk smaller outrunners.

Added gear reduction multiplies the torque and helps remove the resistive load from the motor.

A smaller higher kv motor will burn up quickly.

I don't mean to sound rude, but I've tested different motors for over a year now. The experience I have, didn't come without burning a few up.

Direct Drive is very demanding in the motor/ESC department.

Since a typical diff is going to have something like a 3.85:1 gear ratio. Combine that with a 5.75" diameter tire. You're talking about 4 1/2" of vehicle travel for EACH turn of the motor. It is true that outrunners make 5 to 7 times the torque of a comparable size inrunner, BUT this amount of vehicle roll per revolution is a huge load.

Again I say, 40mm stator diameter and at least 20mm in stator length.

Not to oppose you but do you know how light the e-savage is? With this setup it will lose more weight theirfore making the already light e-savage even lighter. It will weigh around 8lbs when finished.

[sikeston34m]

Ok, Good luck with your build

[Takedown]

Originally Posted by sikeston34m

Ok, Good luck with your build

Im really not trying to stand up to you its just I think he'll get some pretty darn good preformance from those motors. I'll see if I can surprise you.

[MetalMan]

Keep in mind that those glow "equivalents" are for airplane engines, not car engines. The engines we use in cars are quite a bit higher performance than the airplane engines of the same displacement.

I agree with Sike, those motors are too small. I was looking into a motor for my Revo, and was looking for something containing a stator with dimensions of about 40mm diameter x 30mm length.

[lincpimp]

I will put money on the fact that the e savage will be no lighter than my hacker emaxx. Listen to sike, he knows what he is talking about!

In any case, whatever the mfg says about glow motor equivalentcy (sp?), you are asking this motor to start with a heavy load. The mfg rates an outrunner with a prop. We do not use props in car (well I have!). Keep in mind the roll out of the gearing and the load imposed on the motor. Not to mention the voltage and current spikes thru the esc.

JRH made a good point with motor weights. Plus you need a decent sized lower kv motor to make this work. I am seeing that 4s is just not really the best way to go with outrunners. Motor voltage, lower kv, and less amp draw makes for a better system, inrunner or outrunner.

An electric vehicle will weigh slightly more than a gas vehicle, if you intend to reap the benifits of electric (longer runtimes). I am sure that you can find a good 25--30c lipo in the 2500 mah range that will give you comparable runtimes to a single tank nitro run, and weigh in similar.