wow! and some questions...

[ozdave]

Well finally got my little project finished and all i can say is wow! its faster than I expected it to be :)

I've got a 9920 with 540c 8xl. So far have only been able to run on 12 cells and its a lot faster than stock on 14!! but i have a few observations.

The grub screw on my pinion continually came loose which was a pain to fix in the field. Not a big drama to fix and I figure some loctite will sort it out but is this normal? i did it up pretty tight and have a decent notch on the motor shaft.

It cogs quite a lot at low speed on the 12 cells, the batteries I have are gp3300's (the others are IB4200) Once i put some throttle on it goes away and I havent yet tried on 14 but should this be expected on 12 cells?

Recommended slipper tightness? I've tried a few settings tight then back off 1/4 turn and also 1/2 turn but it will flip far too easily, either with wot or hitting the brakes. will loosening soften this effect like it did with the stock slipper or will the power just mean i shred the slipper pads

Brakes. The brakes on the 9920 seem pretty much an instant reverse and not very gradual like with the evx. I followed the programming instructions in Mikes sticky thread. Is this normal or should i reprogram to get more granularity in it?

I cant wait to get this out for a run with the nitro boys :)

[BrianG]

Yes, lock-tite will work. Some people can get away without it, but it won't hurt to use some.

Are you sure it's actually cogging? On the BKs, it will cogg a little at really low speeds because the ESC is having trouble finding the rotor position. Once you get some speed, it runs fine (as you've seen). You can minimize this a little by gearing down so the motor isn't as loaded, but you'll lose top speed obviously.

With BL, a slipper is more to protect the drive train from sudden changes (like landing from a jump WOT) rather than to control a launch. If you loosen it enough to have a gentle launch, it will slip too much. Most tighten it so it doesn't slip at all under normal running.

Set the reverse/brake EPA of your radio (if possible) down to like 60%. That should help tame them a bit.

[ozdave]

No im not sure its actually cogging, i just assumed thats what it was doing. sounds about right as to what your saying though Brian and its probably not

Ok I only have a traxxas TQ3 so i'm pretty sure i cant change the EPA?

[bdebde]

I manage to use the slipper for traction control in my HPI MT2 (no center diff, just the slipper). If I set the slipper per the manual, the slightest blip of the throttle will send it into backflips (Mamba Max 5700 on 3s). I have the slipper set to the point where the front end won't come up under full throttle unless I hit a bump. I do need to replace slipper pads every so often, not bad though.

I have the slipper set to the point where the front end won't come up under full throttle unless I hit a bump. I do need to replace slipper pads every so often, not bad though.

I'm surprised that the pads on the slipper don't need to be changed more often with the slipper being that loose. Have you noticed how hot the slipper gets with it's adjusted like that?

[BrianG]

Originally Posted by ozdave

Ok I only have a traxxas TQ3 so i'm pretty sure i cant change the EPA?

No, you can't change the EPA. I'd say you have a few choices to tame the breaks:
- Get a new radio that has EPA.
- Use mechanical brakes (servo/disc brakes) that you can adjust mechanically.
- Simply ease up on the brake. :)

[ozdave]

Thanks Brian, I figure its just a case of retraining my throttle finger for now :)

Also on the cogging at low speed i mentioned earlier. You said "on the BK's" does that mean that other ESC's wont do this? Is it a traight of the BK?

Thanks

[BrianG]

The BKs tend to cogg a little at very low speeds (<2-3mph). This is simply due to their software. They are a solid performer, but pretty simple programming-wise. After all, most people don't have BL to go slow. :)

[bdebde]

Originally Posted by AAngel

I'm surprised that the pads on the slipper don't need to be changed more often with the slipper being that loose. Have you noticed how hot the slipper gets with it's adjusted like that?

It does get pretty warm, but I usually don't drive it more than 30-40 min straight (usually less). It really isn't that "loose", only slips for several feet when you really nail it. I got the 4 wheel drive MT2 after having a 10T forever (figured brushless would be to much for 2 wheel drive), and I sure didn't want the front wheels in the air all the time (or be on my lid, lol). It took a while to even get the MT2 dialed to hook up with the 5700 on 3s. Now it launches like a rocket though!

I am just suprised that no manufacturer has yet (that I know of) put current limiting on brushless esc's for traction control. All the better brushed ones of days past used current limiting. And punch control is not the same thing. Current limiting would likely keep lipos happier and motors cooler.

[BrianG]

It's kinda difficult to use current limiting in BL. The only way to truly limit the current is to have the ESC "read" how much is being pulled and then reduce the throttle based on this reading. This is usually done by inserting some device inline with the power (shunt resistor or feedback coil), which would rob power no matter what. So, ESCs try to do this indirectly through some kind of "start power" setting or throttle curve programming (MM), or by selecting different grades of battery (Quark).

[nativepaul]

The Castle Creations Phoenix ESCs for my planes have current limiting, although its for ESC protection not traction controll ie, its only programable for hard, soft or off at the rating of the controller, instead of limiting at a programable ampage.