Yes, I had quite a bit of trouble getting a decent picture as well, due to the shine.

Here is another thing to try pertaining to the brakes:
set the brake exponential to the base settings (stock settings on the radio). Then, reprogram the controller.... Then, add more brakes on the exponential. The brakes are potentially strong enough to stop very quickly, but it may take a little programming effort to find the right setting. If the controller is programmed with a high brake exponential already set, the actual braking ability may be minimized. Try this and let me know how it works out.

I got to run one pack through the buggy a few minutes ago. I'm still working on the solution to hold the batteries in, but I'm hoping I may have something worked out in the next couple days.

I did work with the brake exp. on my M8 and was able to dial in a good amount of brakes. It still doesn't have "super-brakes", but it's more than adequate for stopping the buggy quick. I'll be trying out between 75% and 100% at my local track (which we're building now) to see where to sweet spot is.

My wife was sitting with me when I ran the pack in the car and one of her first comments was "we need a bigger yard, don't we?". :)
I love my wife :)

Thanks for the idea on checking the brake exp., Mike. I did try good batteries, but they didn't seem to make any difference.

Attached is a pic of the overhead view.

I am glad you got some brake action. i don't like my brakes to lock up, but I do like to be able to slow down! So, is the wife working on that bigger yard for you!?

:)

She's not working on a bigger yard, but she wouldn't mind me buying a house with a bigger yard ;)
She's working on delivering our second daughter :)
The due date is May 5, 2005.

Just wanted to post a minor update about the buggy.

Things have been going well with the buggy and I think I have my solution for holding the batteries in. I got a 4ft piece of elbowed 1/8" aluminum from Home Depot and I'm going to cut a couple pieces out of it long enough to fit the chassis. I'll drill holes to allow me to secure it to the chassis with bolts, then secure them to each other with a threaded rod, kind of like a turnbuckle-type thing. I'll then slot the aluminum in different places to allow for velcro to hold the batteries onto the aluminum.
The weight I'm adding should bring the buggy to about 9-9.5 lbs with 16 cells. I'm hoping to cut enough out of the aluminum battery holders so that I'm adding as little weight as possible.

I'm keeping my updates going at rcpics.net:
http://www.rcpics.net/member/Batfish

One last question - I'm horrible with math, so I figure someone else can give me a hand :)
I'm running 15/46 now, what could I expect to see by way of speed increase if I go to 16/46?

Thanks.

Congrats on the pending arrival - My wife is working on my second daughter also - due may 25. She would also like a bigger house and yard - in that order. Yard / house in my order...lol - Keep us updated on the little miss - take care......

If she stays in till the 26th of may, her birthday will be on the same day as mine!

Congrats to both of you!

Yes, Joe. Congrats on the upcoming family member! For your gearing question - on 6 cells, you should see about 2 mph increase in speed by adding a tooth to your pinion. Obviously, more voltage will add speed as well (1 cell will add almost 5mph at that gearing).

Thanks for the well wishes, guys. :)
And thank you for the information on the gearing, Mike.

That goes for me as well.... :)

Another minor update today.

I started creating the battery trays for the buggy.

I'll tell ya - it's tough to make pretty stuff with a Dremel and a reciprocating saw :)

Wish I knew someone with a machine shop that was just waiting around for me to give them stuff to do for free :)

Anyways, I have a new picture up at rcpics.net.

http://www.rcpics.net/member/Batfish

Update on the family :)

My wife and new daughter are doing great :)
She's just over a week old now.

Thank you all again for the well-wishes!

Awesome
 

Good to hear everyone is doing well - my wife has 1 1/2 weeks left and she wants it out NOW - lol..

Concratulations to you and your family!

Latest Run
 

I finally got my battery trays in some type of order and was able to get everything together for a run tonight for the first time in a couple weeks.
I used two 6-cell GP3300 packs (unmatched) wired in parallel. The BEC on the Warrior was enabled and I did not use a receiver pack.
My observations:
Speed - the speed was good for my back yard. I'm pretty sure it was as quick as my stock E-Maxx on 12 GP3300 cells. I'm hoping to get to my local track and try my 8-cell packs some time this week.
Cogging - very minimal. I'm definitely happy with how it worked this time around.
Brakes - I noticed mid-way through the run that I had no brakes again. I ended up breaking one of the pickets on our picket fence! (Don't tell my wife :) ) I had set the brake exp on my M8 to 100% last time out and I'm wondering if I need to start the radio at 0% and increase it after the car is already on. Does that make sense?
Runtime - on the two 6-cell packs (peaked about a half hour or so before I started running) I got at least 10 solid minutes of running. It was probably more like 15 or so, but I didn't time it.
Heat - here's where I may have a concern. Both the motor and speed control got hotter than I expected them to. I had left my IR temp gun in the garage, so I was just touching them. The motor was definitely hot to the touch and the speed control would have burned my fingertip if I had left it there for more than a second. When I was done I brought the buggy into the garage and checked the temp. After having a couple minutes to cool down in the 50-degree weather, the motor showed 140 degrees and the ESC was at 145. On only 6 cells should either be getting that hot? The batteries were actually cooler than either the controller or the motor. I'm sure this is because they are decent cells and they were wired in parallel, but both packs were comfortably warm and nowhere near hot.

Anyway, that's my latest report. Comments? Feedback?

Thank you.

The heat is due to the amps you are drawing. On six cells, in order to make the power, the system has to draw high amps. If you cut the gearing in half and used the cells in series, the truck would run cooler AND have more power. The cells were wired in parallel, so they shared the amp draw, which no doubt minimized the temps. For the brakes, when you lost them, were they gone for the rest of the run, or did they disappear and reappear? This may be a result of the heat as well, but it is somewhat baffling.

Okay, so I'll get better temps with 8-cell packs? Good :)
Temps have to stay safe for at least 15 minutes of racing.
Speaking of heat, what's the "safe" upper-range for the 8L and the Warrior 9918?

As for the brakes, I didn't even try to use them for the first 5 minutes. The brakes did not work at all when I tried to use them. It wasn't that I lost them, they just didn't work when I tried. I would push the throttle to full reverse, the buggy would cruise to a stop, then reverse would kick in. No brakes. As long as the weather is good tomorrow, I'll try what I was thinking with setting the radio to 0% before turning the buggy on, then increasing brake exp on the radio and see if it works.

I have new information regarding the brake problem.

Using my IR temp gun I've determined that the Warrior stops braking when it reaches 120 degrees.

Here's some information as to how I arrived at that conclusion.

Batteries: I ruled out the possibility of bad batteries by running these configurations - (1) 6-cell GP3300 sport pack, (2) 6-cell GP3300 sport packs in parallel, (1) 8-cell IB3600 pack in an MEC solderless power tube, (1) 6-cell GP3300 side-by-side matched pack. In other words, I've tried 7 different battery combinations with 5 different pack configurations, 3 different pack assemblies, 3 different pack manufacturers, 2 different cell types, and both matched and un-matched cells. I think that rules out that the batteries may be a problem.

Motor: The Feigao 8L was at different temps each time I noticed the brakes failing. 100, 113, 98, 128, 130, etc...

Radio: I had my M8 set at 75% brake exp the entire time and did not change it either while the buggy was on or while it was off. There was no change in the radio configuration between the times the brakes worked and the times they did not.

Speed Control: The Warrior 9918 was measured for temp by pointing my IR temp monitor at the heatsink. Brakes worked fine at the following temperatures: 65, 88, 91, 98, 112, 116, 118. Brakes did not work at all at the following temperatures: 122, 125, 130, 134, 140.

To test this, I drove my buggy in my back yard at at least 1/2 throttle (as fast as I could in my small yard, at least). I would drive for maybe 20'-100' or so and try to apply the brakes. I measured temps when the brakes were working; each time the temp was 118 or lower. I also measured temps when the brakes were failing; each time the temp was 122 or higher. When I took the measurement of 125, I stopped the buggy and let the ESC cool to 116, then drove forward about 15' and applied the brakes; the brakes worked. I then drove about 100' and tried the brakes; they did not work and the ESC measured 122 degrees.

Lastly, my Warrior has the first two digits on the sticker blacked out with what looks like magic marker. So it's *blackspot*18. Is this indicative of something? I was under the assumption it was just one of those mis-labelled controllers I read about in another post, so Mike may have just blacked out the 70 so customers wouldn't think they were ripped off. If that isn't the case, please let me know.

So my new question is: What do I do next?

Thank you.

That is very interesting info, Joe. I will try to contact BK and see if they have some comment on this. There must be a component that is overheating and causing the failure and I will try to see what it could be. In the meantime, I would try a fan over the controller heatsink to keep it cool.
There were quite a few mislabeled controllers, and I sincerely doubt the sticker is any more than a coincidence. If your controller has 4 caps and two boards, it is the 9918 controller with the wrong sticker.

Thanks, Mike. Let me know what you find out.

I have a few 12v CPU fans around. I'll set one up on the controller and see if that helps keep the temp below 120. The fan won't spin very fast since I only run 6 or 8 cells, but it's something to try.

My concern at this point (aside from the obvious) is that the controller gets to 120 in less than 5 minutes running in my back yard. It's got no chance of keeping brakes during a 15 minute race at that rate. I'm hopeful the fan will help while you find out from BK what's going on.

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.

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.

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.

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.

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.

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 :)

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.

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.

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)

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!

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.

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 :)

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!

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).

Hmm, good to hear, Mike. Talk to you about that later on.
I have a 9918 which I can send into the thermal abyss without any trace of brake fade, this confirms their theory.

New Update
 

Just throwing another update at this thread.

I've finally decided that, rather than trying to force a different center diff (one from the OFNA Ultra MBX) into the Hyper 7 by drilling even more holes into the chassis, I'd sell the Hyper 7 and actually buy an Ultra MBX. So, the Hyper 7 is sold and my MBX will be here this week.
My pinion/spur ratio will immediately change from 15/46 to 15/51, using the plastic spur gear from OFNA. Also, with the plastic gear I can go as low as 10t for the pinion from Mike.
These changes are for the better all around, since I was able to pick up an RTR MBX with a complete second chassis roller for the same price I sold the Hyper 7 TQ for.
I was able to satisfy my curiosity on if/how to make it work with the Hyper 7 and now I'm getting ready to make the MBX an actual racer so I can get out with the nitros before the end of the season :)
I expect to have another update for this thread this coming weekend, as long as I receive the buggy.

Mike, I saw in here that you said running 14 cells in series on the XL 2000 would hit 30mph correct? Would it be possible, and safe to run an XL 2400 on 12 cells in series with an MGM 80? Im just asking, because ordering a controller for $200 to handle a motor that my controller should be able to do currently is a little iffy. Otherwise I'm happy to purchase a BK 9920 I guess.

Ohh, and for the mbx r2, I found coldfusion was willing and planning to make delrin spurs, so no worries on the metal pinions

I got my MBX pros from my ebay purchase a couple days ago, but it's been too hot and humid to do anything with them yet. I'm hoping to have one up and running with the MGM 12012 and Feigao 8L with 4s lipo by the end of the week.

Sounds sweet, I hope to have an mbx r2 roller with motor mount and 2 delrin spurs in my hands after my vacation in a week. Looking for something to run around the newly built and groomed park.