Got my 9920/XL1600...
 

I got my 9920 and XL1600 today and installed them without any problem. When I first saw the size of the 1600, I was thinking "how can this be faster than 2 775s?" Well faster is an understatement...it screams! I laid rubber on the basement floor! I have a fan aimed at the motor to cool it. I'll post pics when I re-do my PolyMaxx page.

Here are my initial impressions from going dual 775s to brushless:

-The brushless is much more quiet than dual 775s. I kinda liked the intimidating noise of the 775s but it's definitely cool to have a stealthy speed machine too.

-It is a lot easier on the batteries than dual 775s...I haven't tripped my 30amp breaker yet even at full throttle in second gear, so this thing is not drawing much considering the power output.

-It does have minor cogging when crawling a hill very slowly...didn't have any of this on the 775s, but this truck is meant to go fast so I don't care much.

-The breaks take getting used to...on my previous setup, breaks were controlled with my 4th channel.

Depending on your radio, you can dial out some brakes. I usually cut the braking power in half so it slows more controllably. With enough voltage, the xl1600 will easily outperform a pair of brushed motors!

dido. mike, what does a.r.c. and e.p.a. stand for? (settings on my radio) also, how do you turn down the braking on a airtronics cx2p?

EPA means end point adjustment. This controls the travel of the servo on steering(dial out more or less) and the throttle. Adjust the brakes by setting the EPA on the throttle channel(you can usually adjujst throttle and brake EPA independanlty byt squeezing the trigger or applying the brakes while you are programming).

Finally, some pics! I updated my PolyMaxx page on Fastmhz.com where you can see more pics and information:

http://kmcsonline.com/casemod/emaxx/PolyMaxx2.jpg

that 30 amp breaker is meant as a fuse?

Yup, it's essentially an auto-reset fuse, so when it trips, a few seconds later power is automatically restored without having to put in a new fuse. I haven't tripped it yet with my brushless setup, but did trip it a few times with the dual 775s. Protects the motor, esc and polys from damage should something happen to stall the rotor.

might be dangerous for you esc. If it brakes the circuit, the voltage in your esc is getting higher than it may be. The esc needs to be loaded with the low internal resistance of the batteries to brake. once this ressistance is endless, the energy can no longer be stored in the batteries, and may cause a peakvoltage in the controller, which can be damaged from that. I would never run a fuse/breaker in my circuit.

That's VERY interesting information...seems like a catch 22...no fuse, possibly damage motor, lipos and esc...with a fuse, possible damage the esc if power is cut while breaking...is there any way to get the best of both worlds?

There are some kind of diodes out there that short when a certain voltage is reached. My idea was to use those diodes on the side of the batterie or on the side of the 3 wires of the motor. That way the whole circuit stays save. It are very fast things, the peaks will be absorbed and i know that they are available in very powerfull, yet small casings. If you don't know what diodes those are please let me know, i can ask a friend of mine..

Personally, I don't think the fuse device is necessary. It is a neat idea, but that motor on your setup is very safe. The controller has locked rotor detection so if it gets stuck, the controller will let you know.

Wow - thanks for all the feedback guys - I'm learning a lot. 3 things:

1. I'm interested in those diodes, and I'm sure I have some if I know what to look for.

2. How will the controller let me know it is stalled? Wouldn't it still over-draw my polys for a few seconds?

3. When the breaker trips, everything on the truck loses power, including the receiver and BEC. Wouldn't this prevent me from breaking and causing harm?


This stuff is much different than brushed technology!

Serum can give you the details on the diode(or his friend can).

The controller won't start if it is locked. It wouldn't be a matter of seconds- less than a second.

If the truck loses everything, then the controller should be safe, but......no steering and no brakes may cause you to break when you crash into something or worse, drive into the lake!

that would suck.

how fast is it

If you're wanting to know how much current you are drawing and peak voltage I sugges that you visit this site

www.rc-cars-planes.com

I have one for my electric planes and found that it has been invaluable for knowing current draw and setup for different gear ratios and props (pinion/ spur equiv) and ensuring that I am not overdrawing on my lipos.

I don't think you need you need to worry about any safetyissues about your controller/setup.. Beacause you are running a safe setup. I will talk to my friend tomorrow, asking him about those diodes. Funny thing; when i mentioned this to schulze, all of a sudden the language barrier was too big to discuss anything like this.... How odd..

Now that I've had a chance to give this new setup some good runs I've noticed a interesting heat issue. After a hard run, the motor can is just warm to the touch, never really hot, but if you touch the end of the armature where it sticks out of the bearing in the back, it's so hot you can't touch it for > 2 seconds.

Should this concern me? It's geared 72/20 right now.

how fast is it?

Sounds pretty hot. Some of this heat is likely from the magnet, as well as a small amount of heat from the pinion/spur mesh. Have you installed a fan? It si difficult to get an accurate temp reading on the shaft itself, but keeping the can as cool as possible will help keep the shaft cooler as well. Not a huge concern, but cooler is always better.

It's geared for torque and runtime, not speed. With my current gearing of 72/20 and 6" tires it runs around 35mph.

I do have a fan on it as seen in my pic further up the thread. I just ordered some smaller pinions and will gear a little less since I sure as heck can't control it at 35mph anyway.

You have nothing to worry about. No need to gear down, either.