Brushless 1/8 Buggy

[RC-Monster Mike]

What motor did you use, starscream? The 8L is not the right motor for high cell counts in the 1/8 buggy. The 9L or 10L works with the gearing you used, but the 8L is tough to get the right ratio in a buggy using the stock spur gear.

[Batfish]

Originally posted by starscream
What is your gear ratio?
I ran my MBX-5 with a 13T pinion and a 46T spur and fried my controller in 10 minutes. This gear ratio is way too high. I temped my controller at over 200 degrees F. I fried two FETs and who knows what else. The motor was also damaged in the experiment. Luckily it didn't cost that much to repair...

I am setting up my MBX-5 with a gear ratio closer to a monster truck. I'm going to start really low and work my way up.
My first try will be a 13T pinion and a 65T spur.

Hope this helps.

Thanks, starscream. I remember your post from earlier about frying the controller, which is why I check the temps so often. So far I have not had a temp above 155, so I don't think I'm getting into the problem you had.
I do have 15/46 gearing, though. I've had this gearing right from the get-go and I'm just working on Mike's advice on getting the right brushless equipment to work with my project. So far there haven't been any thermals, just the weird brake issue.
I did buy an OFNA comp diff and the plastic spur for it. The spur is 51T, so once I get it all to fit my buggy I'll have more and better grearing options. It's going to involve moving the diff more to the center of the chassis and drilling new holes, but it shouldn't be too tough to get done.

[Batfish]

Mike,

Any word from BK about my 120 degree brake issue?
I mounted a fan, but all it did was let the controller run for about 10 minutes before hitting 120, instead of about 6 minutes.

Thank you.

[RC-Monster Mike]

No word yet. I will call and speak to them early Monday morning and see if they have a suggestion. There have been one or two other cases that I have heard of, but no one did the due diligence that you did! I will be sure to let you know when I find anything out.

[Batfish]

Thank you, Mike.

I suspect that regardless of what you find out from them it will not be something I can fix myself. Should I expect to be sending the ESC in to someone?
I know it's premature to ask since you haven't talked to them yet, but with the new kiddo here if I can get something done in my little free time (like remove the ESC) then I'll get it done ASAP :)

[RC-Monster Mike]

Best case scenario, I can fix it. Worse case scenario, I have to send it to Germany. It could be as simple as replacing one of the parts on one of the boards (most likely). Either way, the controller will have to be removed and shipped somewhere.

[Batfish]

Originally posted by RC-Monster Mike
Best case scenario, I can fix it. Worse case scenario, I have to send it to Germany. It could be as simple as replacing one of the parts on one of the boards (most likely). Either way, the controller will have to be removed and shipped somewhere.

Thanks again.

I'll work on removing it in the next day or so.

[MetalMan]

If it has to be sent back to Germany, don't expect it for a while. I burned out my 9918 back in mid December, and had it shipped right away to BK. 4 months later, BK ships it back! I have a burnt out MGM 120amp, so I will see what their servicing is like.

[Dafni]

I just sent in a 9918 with brake issues. Directly to BK.
They told me the repair should be done within 48 hours, and even confirmed this information. So I sent it in with the best hopes.

I'll keep you posted when I get it back.
(btw, it's the esc from my TF, some of you might remember the story)

[RC-Monster Mike]

I have never waited more than a month for service from BK. And this was when they were away at an event. BK has been good to me. I even had a replacement shipped before I sent the faulty one in once!

[MetalMan]

That is strange how mine took so long. Although, they did replace the broken one with a new one. The one they sent seems to have the brake problem that has been experienced. Whenever the controller gets to around 155* F, there are absolutely no brakes. At 150*, the brakes start fading. This is when it is used in my 1/8 buggy with an 8L.

[RC-Monster Mike]

I will hopefully find the cause tomorrow and let you know if it is something that can be fixed fairly easily (If I can fix this, I will). I am assuming it is one part in particular that may be failing (obviously, due to heat). I haven't had this problem on my controller at all, and most don't experience it, but I have heard of 3 or 4 with this "brake fade" issue.

[Batfish]

Originally posted by RC-Monster Mike
I will hopefully find the cause tomorrow and let you know if it is something that can be fixed fairly easily (If I can fix this, I will). I am assuming it is one part in particular that may be failing (obviously, due to heat). I haven't had this problem on my controller at all, and most don't experience it, but I have heard of 3 or 4 with this "brake fade" issue.

Mike,
Any word on the problem? I've got people at my LHS that want to see the buggy tear up the outdoor track and I'm really looking to oblige them :)

[Dafni]

The BK guy who had a look at my controller told me that I must have ran it rather hot. He said a lower gearing should take care of my problem. Strange thing: If I mount another 9918 it works flawless. :C: No reply on that, though.

BTW, I got the same results as you, brake's are fading above 50/60°C.

If I find a minute, I'll tell you the whole BK story. Gotta go now. Weekend! Yay!

[RC-Monster Mike]

Well, after some long discussion with BK, they say the problem is in the IC chips. They say there is a specification variance on these parts (not controllable) and if the ICs are on the low end of the variance, this will happen. Dafni, I mentioned your similar issue as well (they remembered your name). I think I may be able to get them replaced (and hope for better ICs on the replacement).