Direct Drive to Diff E Revo Build

[sikeston34m]

Originally Posted by suicideneil

Hmm, it seems like getting hold of that heatshrink will be very difficult since I in the Uk- they do ship overseas, but the prices for the rolls big enough for what I want are rather high..... I wouldnt mind some of that blue, 2 metres should be plenty. PM time me thinks.

SuicideNeil, You have a PM.

For you other United States Peeps, I posted the Auction. I'll fix you up.

Thanks.

[zeropointbug]

Neil... there MUST be shrink tubing in UK, just keep looking.

[sikeston34m]

Originally Posted by zeropointbug

Neil... there MUST be shrink tubing in UK, just keep looking.

It would probably be cheaper, over seas shipping is pretty expensive.

[DrKnow65]

sikeston34m what auction? where?

[sikeston34m]

Originally Posted by DrKnow65

sikeston34m what auction? where?

Go to Ebay, type in "battery shrink" in the search box. I'm the colorful guy at the bottom.

[DrKnow65]

Congrats, you just made the "favorite sellers" list.

Back to topic, if this setup is requiring gear reduction, what KV motor would you have gone with instead? (interested for a someday revo, more interested in a tomarrow kind of direct drive hyper7) or would these be two entirly different KV needs???

[sikeston34m]

Originally Posted by DrKnow65

Congrats, you just made the "favorite sellers" list.

Back to topic, if this setup is requiring gear reduction, what KV motor would you have gone with instead? (interested for a someday revo, more interested in a tomarrow kind of direct drive hyper7) or would these be two entirly different KV needs???

Thank You!

I feel like I chose the best KV available that would fit the space/shaft size.

The lower the KV rating, the more torque they are supposed to have. This AXI 4130 is rated for up to 8 Series Lipo in an airplane. On a HV (8 series or more) setup with the 4.3:1 gear ratio diffs, I think this setup would absolutely scream. The plastic shafts would snap quickly, severe tire swelling, hard to control, good things like that. LOL

The problem with the higher gearing is, the ESC isn't reading the EMF feedback properly because there isn't enough feedback from the motor at low rpm's. I feel like this is the source of the cogging. I think Brian, (a very intelligent person) is right about this.

I wanted to try this with the stock diff gearing. I have at least learned something about the lower rpm threshold for EMF feedback and sensorless control.

On 6S2P A123, the motor, is on the lower end of it's recommended voltage range. Maybe 18 volts loaded. On 8 Series Lipo (around 30 volts loaded), it would be much stronger. But this exceeds the voltage limits of my Quark and I don't want to blow it.

It looks like this project is stalled waiting on the Hybrid diffs for now. But when I do get them, I will first try the 4130 again before switching to the higher kv 4120 motor. It should be interesting and hopefully show more about the behavior of these motors.

[DrKnow65]

Ohhhhhhh I see, I missed the whole 8S-6S thing... and never put togeather the gears with the cogging (feeling like I need to go back and re-read the thread) I have watched it for awhile and read all the posts but I must have been too busy looking at the photo's :)

[johnrobholmes]

Originally Posted by BrianG

Isn't there some kind of rule-of-thumb that states the motor has to spin a certain minimum percentage of its kv rating for the ESC to get the proper back-EMF pulses?

Patrick del Castillo told me it was 10% of the kv. With a rollout of 6.5 inches that would put this rig at a min speed of .3 mph or so, but I would at least double that figure or more to be conservative. The startup speed of the ESC is not the same as the minimum sensing speed however, so it might be trying to start the motor up much faster. Once you put the new diffs in your startup issues should go away, especially when you volt up.


Volting up right now might even help the startup, if only making it more abrupt and violent.


I really dig the build, I love how low and clean it looks. I still want to try this, but I sold my revo a while back and the emaxx isn't getting parted out yet. I have a 3032 I want to try, should be about like a 4020

[sikeston34m]

Originally Posted by johnrobholmes

Patrick del Castillo told me it was 10% of the kv. With a rollout of 6.5 inches that would put this rig at a min speed of .3 mph or so, but I would at least double that figure or more to be conservative. The startup speed of the ESC is not the same as the minimum sensing speed however, so it might be trying to start the motor up much faster. Once you put the new diffs in your startup issues should go away, especially when you volt up.


Volting up right now might even help the startup, if only making it more abrupt and violent.


I really dig the build, I love how low and clean it looks. I still want to try this, but I sold my revo a while back and the emaxx isn't getting parted out yet. I have a 3032 I want to try, should be about like a 4020

Aaaaaaaah, so there's some confirmation about what's going on here! I'm VERY sure that with lower gearing, this thing is going to be a BEAST!

The reason why I want to switch to the 4120/14 is the higher kv to work with the Quark. It will have more than enough torque to work with the lower gearing.

I'm wondering something about the new 4120 motor. It's 15mm shorter than the 4130. Is there enough room to put the mechanical brake back in there and go with a HV forward only ESC? An ESC like the Phoenix HV 110amp version might be a good choice then. The Voltage could be cranked up as high as motor temps would allow. I think that would be pretty high, since this setup gets rid of the heat well. Is there such a bracket for the brakes though? Before it was mounted on the transmission, which is obsolete with this setup.

Thanks for your compliments. The low center of gravity that this has, REALLY sticks it to the ground. It's gonna high speed corner VERY well. I know on gravel, I could turn the wheel sharp at 30+ mph and it would just go round and round like it was on ice, instead of tripping/flipping over it's front tires. LOL

I don't think I like the Revo tires very well. Will prolly be changing out to something else. The E maxx's gator tires grip really well for off road.

John, I'm sure you are looking at the Scorpion 3032, correct? I put a 3032/10 in a Direct drive to transmission setup in an E maxx. It was a great performer for the first pack.

You gotta think about how much we are pushing, jerking, and tugging on that stator with this type setup. I ripped the stator from the bearing holder. In other words, the stator spun loose and ripped the windings from the power leads.

At the factory, sometimes I think they don't loctite the stator on both ends. This appeared to be the case. Even on the AXI 4130 that is in this one. Same thing. A prop doesn't have brakes like we use constantly or the resistence of acceleration that we are asking.

I used Red Loctite between the stator and the bearing holder on the endbell side. I had to slow "bake" it at 100 degrees for about 6 hours to get it to set. Green Loctite is the Better choice. It weeps into the microscopic holes and sets quicker with no temperature increase. I would make a puddle there and it would soak in, then I would do it again. About 3 "puddles" soaked into that crack, so I think the void was completely filled.

I know you plan a custom wind, I just don't want you to learn the hard way like I did. Let me know how it works out.

[sikeston34m]

Waahhooooooo Mike is gonna build me some Hybrid Diffs!

Seems like the 4.3:1 ratio was the least in demand, so he thinks he has some gears laying around and he's gonna check on the rest.

Me thinks this project won't be held up for long.

[johnrobholmes]

Yes, I am talking about the scorpion motors. I have a few built ones and a single kit here. I was planning on changing the magnets around and seeing how it would act at about 2000kv, but the ring bearing won't like the high rpms. 1000kv or less would be the ticket, it should really be ran close to 6s lipo instead of the 4s max that they are wound for.

[sikeston34m]

Originally Posted by johnrobholmes

Yes, I am talking about the scorpion motors. I have a few built ones and a single kit here. I was planning on changing the magnets around and seeing how it would act at about 2000kv, but the ring bearing won't like the high rpms. 1000kv or less would be the ticket, it should really be ran close to 6s lipo instead of the 4s max that they are wound for.

I have a 3032-12 on hand with the ring bearing. Is the ring bearing a press fit?

I didn't wanna just put it in a press without knowing, and break something.

[johnrobholmes]

Yeah, the ring bearing is a press fit into both the can and the faceplate. It takes a hammer to get the motor apart once it is together. You have a bearing press? Also, the rear of the can is just pressed onto the backside fan plate in some cases, make sure to check that and seep some locktight in.

[sikeston34m]

Originally Posted by johnrobholmes

Yeah, the ring bearing is a press fit into both the can and the faceplate. It takes a hammer to get the motor apart once it is together. You have a bearing press? Also, the rear of the can is just pressed onto the backside fan plate in some cases, make sure to check that and seep some locktight in.

I use a drill press with a 4 or 5 mm rod. Just prop it up in a vise the way I need it or use blocks.

I can put quite alot of pressure on one this way.