Another MBX6T Race Build.
 

Well, based on the current performance and recent development of brushless setups along with the quality conversions being offered today I decided it was time to get back to racing. I've been away from racing for several years now (~5'ish) so it was refreshing to see where things have come. Coming from a custom hyper7 extended, UE VBS/Racer-X setup years ago it was also nice to see the quality kit Mugen has put together. Very impressive indeed.

So based on my plans to build a racer I went with the mbx6t, RCM brushless conversion, Slipperential, Tekin RX8/1700kw truggy setup, lightweight driveline components, AKA's (cityblocks), etc.

Right now I'm trying to decide on batts. Planning on going with Hyperions but not sure on capacity or cell count. Originally I based the motor size on a 5S app for racing. I'd like smooth power with something in reserve without really overpowering the chassis/track. I'm thinking 5S is where I want to be for this app (shooting for 9'ish lb truck rtr).

The other concern is capacity. For a race setup, 2x-things to consider. Capacity and weight (for me anyway). I'm planning on having to run with the Nitro guys so a batt change will be in the cards for me. That being said, I don't want to stuff 6k worth of capacity into the truck due to weight.

Thinking 3000-4000 is where I want to be. Based on the specs from Hyperion, looks like roughly a 4.86oz savings from the 5k to the 4200mah setup (5S). Going down to the 3300mah setup saves me an additional 3.56oz and the 3000mah setup is another 1.41oz lighter still. Assuming the heats are ~5min plus warm up and additional lap and mains are in the 15-20min range, what are you guys who race running?

Pics to come tonight. :mdr:

Good choice man! I converted a 6T at the end of last summer (pre m-spec). Everything went together beautifully and converted smoothly. I have been running the rx8 2000 combo on 4s. Yesterday at the track I did 16 minutes from start to cut-off (full-on race conditions. No letting off at all). That was on Flightmax 5800's. I have been contemplating a 5s set-up, but am still happy with the performance and runtime of my 4s set-up.

The 6T with the slipper and Mike's battery tray are hard to beat. Get the Hotwire so you can really customize that esc. Everything is so predictable while driving. Here are pics of mine and the track I race at (that's a 25' double in the foreground). Also Running the 4.0 Calibers and Revolvers this year, those are bashing Panthers on there now, because the track has yet to be groomed this season.

http://i255.photobucket.com/albums/h...g?t=1269886580
http://i255.photobucket.com/albums/h...g?t=1269886620
http://i255.photobucket.com/albums/h...g?t=1269886692
http://i255.photobucket.com/albums/h...g?t=1269886615

Tedo,

Thanks for the response. I had actually been following your build here for a bit. Very very similar to what I'm putting together.

I planned on going with 5S solely for the efficiency boost plus it allows me to run a lower kv motor so a little more torque/less work/heat. At least that's the concept right now.

Mike's setup has been great to work with. Simple mod from my end (I did all the custom machining on my hyper7 conversion) so this was an easy bolt together option. Overall, the layout is clean and simple. Battery tray is large enough to offer options regardless of setup and the motor mount works perfectly for my needs. Hopefully it'll translate to fast laps and an easy to drive truck.

Love your body choice too ;) Same setup as mine actually. lol

How have you found the slipper to work for you? Being a mechanical designer, I can really appreciate the concept especially for direct drive guys. Any driveline protection is good protection provided it doesn't make it less reliable. I'd actually like to see Mike incorporate the Mugen outdrives for a small weight reduction (anything helps).

Overall, seems like your getting decent battery life based on what looks like a very fast track layout. Hoping I can get similar from a slightly more efficient setup running on 5S.

Truck looks wicked!

You should be able to use your Mugen outdrives (and many others for that matter) with the Slipperential. I'm not sure what outdrives come with the Slipperential, but the inner diameter was too small for my CVD shafts so I used my stock Caster ones (basically same as MBX5T) and they fit fine.

The slipper is a must. I was driving a converted 5T w/o a slipper and I separated a few rotors. Then again, it was the early days of the T8's (Tekin always took care of me, and had me running by the following weekend). You can adjust it throughout the day once the track starts getting loomier. Plus with the throttle profiles on the RX8 your motor stays very, very happy. I haven't run a fan since late September, and the hottest my electronics have gotten are 120 F. Pretty damn good. I am also geared conservatively. Started out 17 x 46, now I am at 15 x 46. The difference from 39-36mph is barely noticeable at our track. I can still dust the nitros before their clutches spool up (maybe a little exaggerated, but you get the point).

Also, I am on my second outdrives. The fist ones ovaled out (weak materials in the early versions), and Mike sent me 2 new ones for free. They are beefier than the stock 6t cups, but with our brushless power, I am okay having a little insurance. Plus we can save weight elsewhere: tires and batteries. Everything on the stock mbx6t is pretty damn good out of the box, and not many things to upgrade, if at all.

Oh, stock up on the 5 x 21 bearings (the weird size ones in the hubs), those get gritty all the time which increases rolling resistance, which decreased run time.

Get some pics up!

The stock ones on the 6T are not compatible with the slipperential. Mike's new hardened ones are the ticket.

Not working. The Mugen (MBX6 version) has a smaller dia. Both the outdrive shafts and pins are smaller so they don't work with the end plates of the slipperential (or larger spider gears). Unfortunately I tore them both down trying to make it work. No luck....

The other issue I had was one similarly reported here. One of the outdrive pins is/was too long. I did preassemble them prior to installing the plates to the diff housing but it actually didn't fit in the slot of the large spinder. I had to knock off roughly ~.060" to make it work.

Otherwise, went together smoothly...

So are you talking about the big boys that hold the drive pins in the cvd's? Those are some odd bearings. Can't wait to see what those cost... lol

Since your truck seems well sorted, how are you finding the handling on it compared to the nitro guys? I'd assume from everything I've seen, they really put power to the ground but I've yet to see someone putting down good consistent laps (least via video's). Overall, hpw does brushless truely hold it's own out there? I was originally going to stay nitro but just felt like going brushless was something I wanted to give a go. Seems like there are a lot of pluses once one gets them setup.

Yes, the inner bearings. Actually Avid has them for $1 a piece. I got the rubber / metal shielded ones. Put the rubber outside facing, and the metal side inner facing.

Man, as far as handling and holding it's own—there is no stopping it! The only other truggy that can touch it at our track is my friend's 2.0 (he is also the best driver). On one of my good days, If I am out front, no one can catch up unless I screw up (which happens to all of us). I guess this year there is a Z01T and a RC8T CE now... we will see what happens there, should be a good fight.

Bottom line, it holds it's own if not exceeds the nitros. The acceleration is instant and smooth. Very predictable every time. I also have slightly thicker shock oil than stock. I personally like that set-up, and I built my diffs 10/7/3K. All of these things come into play with the handling, and of course it's always different per track, and driver's preference.

I just got a Flip Minnow HD (I designed some of the graphics), so I will get some vid up in the next couple of weeks.

Again, great choice.

Ted,

Definately sounds like it should be able to put it down with the nitro boys. lol I actually raced 12th scale 6-cell mod about 15 years ago and it's been nitro ever since so this is a step in a different direction, one which I'm very much looking forward to.

I'm hoping I can get it setup pretty neutral initially and tune from there. I'd expect the 1700kw 5S setup to provide some pretty solid motor regardless of track size. Hoping the Tekin setup does what I'd expect it too. Seems like quality kit overall.

Love your truck. I'm actually in CT so I'm sure I'll see a few of the guys around here :yes:

Pics in the am. Cable at work :grrrrrr:

Update!
 

Well, finally got some the truck together. Took me a few days longer as I was waiting on a few pieces.

Overall, the build was smooth. Mugen has done a great job as has Mike with his clean integration of a brushless setup. No real surprises at all. I still need to revisit my ESC wrie routing and get my antenna sorted but figured I'd grab some snaps.

Overdue pics :mdr:

http://i23.photobucket.com/albums/b3...9/DSC_6649.jpg
http://i23.photobucket.com/albums/b3...9/DSC_6650.jpg
http://i23.photobucket.com/albums/b3...9/DSC_6652.jpg

Hyperion charger should be here Wednesday along with a few other goodies. Got my batts all wired with TRX connectors (prefer over all my deans stuff). ESC is cal'd and truck has moved under it's own power. :party:

Nice to see my M8 and KO digital still serving the cause. Also got my Spektrum module in and setup. Should work well.

Few things this week. Need to mod my 400watt Corsair Power Supply for charger duty and get my proline bulldog painted! Can't wait to get this out this week for some shake down runs!

Curious what you guys are doing for general break-in on a new mill and batts? Do I need to be overly cautious initially?

Also, with the RX8, when does/should the fan come on? It runs through cal but once I get through the initial setup, it powers down. I'll assume it's temp/load dependant...????

The fan comes on on pwer up and is dependent on temp.

Awesome build. You did a great job. You will love the Slipperential.

Can't wait to see it with it lid on.

I gotta say, the metal to metal gearing is a little loud. I seem to have a touch of run out with my slipperential so my mesh is a little lose right now.

Should work though! We'll see....

Ted,

Curious what your running for esc settings on your RX8?

Well, my hotwire arrived along with my hyperion charger and a few other goodies so I should be set now.

Got the truck setup and moving under her own power yesterday for a few. So far, all seems good. I'm quite impressed with the power output of the RX8/1700kv T8 setup. Motor pulls nice and strong! Sensored operation is pretty flawless. Smooth and no transitional problems from sensored to sensorless. Just smooth buttery powa! :yes:

Brakes are a little strong. I did some slow speed setup in the house not realizing how the brakes actually work so I ended up dialing in too much brake initially. Outside at speed, the result is about 200% more brake than I need. lol So I'll be dialing those back tonight for sure.

Temps seemed to be no problem considering I was just doing very slow roll on's to give the motor/batts time to break in some. Motor was only slightly warm to the touch, batts cold, esc cold (didn't have my temp gun out with me). That being said, even with 10k center diff fluid, any dip/bump in the grass where traction is pretty serious, those cityblocks bite hard and try lifting the front end. Motor spools instantly!

I did intially have issues with the slipperential at the 1.25mm setting. Maybe it was closer to 1.5mm. Don't know but it was clearly slipping pretty heavily. Pulled out the adjuster and made a little change cranking her down and seemed to be good. Tuning to come but for now, I'm looking for only driveline protection so cranked down works (easier on the slipper too).

Per the specs, the 16/46 gearing should be good for roughly 40-43mph and it sure feels like it'll do it. I'm still grinning from the outright acceleration. Trying to be easy on it but man, even a slow'ish roll on and it just flat pulls. I had read something about someone having middle rpm throttle punch issues (maybe Wallot) but I'm just not seeing it with this one. Matter of fact, even with the default linear throttle profile, I'd say part throttle/mid rpm punch is great. Possibly overly aggressive. Serious 50-75-100% throttle punch. It will instantly over power the fronts on a hard punch even at speed. Carefull throttle application will be required.

That being said, the MBX6T is completely planted. The 10k center diff oil weight seems just about right in order to keep the truck planted without over powering the rears making it uncontrollable in a straight line. Overall tracking of the truck was nearly spot on right out of the gate. I made a few suspension setup changes before I ever even bolted on the tires to reduce camber rise in the rear as well as dropping the rear diff oil weight from 4k to 3k. Up front I adjusted the ackerman slightly for more intial steering so we'll see how that goes once I get it on the track but the truck certainly seems like it has PLENTY of steering. Moreso than any truggy I've driven to date.

My concerns about noisy driveline were unfounded as some of it was the slipperential slipping but outside, it's perfectly quiet. No problems there. Gear mesh maybe ever so slightly loose still but driveline is smooth running.

I was going to up the shock oil weights some based on what I've seen for setups out there but seems smooth right now. I'll need to get more stick time on the track to see where we are but honestly, at least thus far, I'm liking the std M-Spec setup shock wise.

Otherwise, support gear wise the ol' M8 with Spektrum mod feels great. Old school'ish now but still has a great feel. My old'ish KO Propo 2144 digi still kicks ass too. I'm shocked how quick the response is on that servo. Still.... And I think the nice constant voltage the Tekin BEC supplies off the LiPo seems to greatly aid in it's ability to do it's job. There are more powerful steering setups out there today but this thing still clearly holds it's own and based on the spec's, there still aren't too many servo's at any cost that are quicker response time wise. Impressive.

-Throttle Profile: 2
-Timing is at 0
-0 Drag Brake
-40% Brake strength
-40% Current Limiter (not so much power during acceleration)
-LVC set at 12.4 (4s)
-Geared 15/46

Just ran at the track (the track in the picture in earlier post) a few days ago and got 19 minutes of hard run-time on 5800 4s flightmax's. The track was a little drier and more forgiving than the real hard bite before when I got 16 minutes. I am pretty happy with this 4s set-up with the custom rx8 settings.

I don't even have the fan installed. Don't need it...

Pretty serious run time!

Thanks for the setting information. I need to take a good look at my setup and see if I want to current limit my setup or not. I guess I'll need to run back to back and see whether there are gains to be had.

Any need to really baby the new setup (batts /motor) or can it be driven like i stole it ;)

Yes, the brakes really need to be dialed down. Then again, I rarely ever hard brake. The guys I race with are pretty skilled drivers, so we all just freewheel around the track.

I was cautious at first for a few batteries (last year), mainly just getting the feel of the truck. It looks as if you have great solder connections, so I would push it to it's limits. Good connections are a must!

Yes, the 6t is a great handling truck. So good.

Also, you will feel a difference with the current limiter. However, the 1700 is from what I have been reading is not as aggressive as the 2000, so you may not need to use the limiter. That's what nice about the pit-tuning options.

Ted

The 1700 puts out more torque than the 2000kv and with the 5s setup vs 4s should require less battery current anyway so might not result in big current spikes. Limiting the current may/may not be necessary. Don't know...

That being said, this thing makes some steam. I raced with a mod RB Rody C5 in my truggy for a little while which is a wicked serious nitro motor. I ended up swapping that out for a modded Picco XP which was MUCH better on fuel but didn't make anywhere near the steam.... Ended up being a much better race motor though. Better in fact than my Nova P5.. This brushless might be quicker... Complete animal.

Maybe it's been a few years and I'm just not use to it anymore but this thing just flat pulls. I was seriously impressed and I have raced a LOT of stuff over the last 15+years.

In terms of break-in, I'd always run the leccy motors low voltage in water to break the brushes/com in and then clean/relube the bearing. Batts got a run or two or charge/discharge cycles before really hitting them. Being new to LiPo and Brushless, wasn't sure what is/was required.

Can't wait to get it out there. Probably some stick time over the weekend if the weather holds.

Hey Ted,

Curious on your RX8 setup. It would appear we don't have real voltage per cell control and the default is 3v/cell as Tekin has it set right now.

With the numbers your showing for run times. Are those run to the LVC? Any issues with your batts? Seems a little low from what i've read (most prefer 3.2v/cell).

Here's mine. It's running a Tekin 2000Kv motor on 5S :yes::yes:.

Drag Brake - Off
Reverse Strength - 30%
Brake Strength - 50%
Neutral Width - 20%
Motor type - BL-DL
Throttle Profile - 2
Cutoff voltage - 3.2V/Cell(16V)
Push Control - 50%
Timing Advance - 10
Current Limit - 70%
Dual Mode
Firmware Version - 200
Gearing - 46/15

Thanks George! I finally figured out the custom LVC... Was kicking my butt!

Well, finally got the truck out for some shakedown laps.

Track I ran at yesterday is actually something my buddy built on his property. Now, we're not talking full blown race track but I figured it would be nice to get the initial shakedown stuff done here. That said, the track is perfectly groomed and very very well setup. It's a little small/short for my 1/8th but some very technical stuff with some solid straights and serious flying (2x 20+ foot trips).

I've got to say, even I was fully impressed as to how this thing ran. Straight up animal! I ended up going with throttle 2 profile (less aggressive) and it proved to work very well. Regardless, that Tekin setup moves a truggy extremely well. Power is smooth and linear and MAN, is there some acceleration at hand. Running my cityblocks on a mixture of clay and high bite loom with some grass worked in there, traction was zero issue. Even with a center diffs loaded 7/10/3 I was able to get a few short wheelies on power out of a few clay corners. Acceleration is instant.

Overall balance of the truck was great honestly. Plenty of steering without being overly twitchy (top hole on ackerman). Transitions very quickly. Suspension was fantastic. Std M-Spec rates and oils. Supple and soft. The slightly lighter oils handled the high speed/high frequency stuff great without being under damped (least here anyway). Puts power down very well without being a handful to drive.

Slipperential was a slight disappointment though. Overall, it's smooth and seems to be working well functinally but I've got something up with this unit. Need to pull it down this week. Seems to have a LOT of runout. Makes me run more gear clearance than normal resulting in some noise and it seems to be wearing my pinion pretty quickly already. Clearly the gear faces aren't contacting each other squarely. Worse still is it's an occilation back and forth. Pinion shows edge tooth contact on both sides from the spur while the center looks good. Really need to get that sorted. It's pretty loud too. I also had some "clicking" which sounded odd. Not sure what it was. I did have some debris mashed into the spur so not sure if that's where it was coming from. Sounded almost diff like (tooth). I checked the 3 of them and all seem smooth. Might require more digging.

Otherwise, was great. Little rusty to start and had some pretty big crashes :( Truck took them all though. lol Brakes were spot on at ~45 I think. Just enough without being too over the top. Enough to lock them up upon corner entry to get the truck squared up but still had good feel. Like I said, the truck transitions soooooo well. Back it in, square it off and power out. There are several technical sections requiring this tech and in particular a tough double - short run to left hand burm - zero run up little step down double to immediate land/left and power out for the big tripple. The section is tight and tough. Too hot in and you'll never get it slowed and turned. The step down double is perfectly long enough to be a PITA! No run up requires good/great punch but not so much as you could clear the whole landing/corner. The height of the landing is enough that you can't just roll it. Timing is critical to enter, jump, land and turn all at the same time. The brushless setup let me drive deep, square off the take off, quick burp and over, soft controlled landing immediately into the left and power out. MBX6T just ate it up once I got my timing. Great control.

Batt punch and life out of the Hyperion 4200's was great. I didn't time it (some starting/stopping waiting for the other guy) but seemed very very good setup 16/46. I forgot my Raytec and didn't get any temps but seemed very very good overall. Motor and batts were a little warm (guessing less than 100F). No probs there. Like I said, shorter technical track so not real long pulls but no heat.

M8 with Speky mod was great. No probs.

So, I just ordered a delrin 50T slipperential spur and I'm going to completely pull that back down and see what's going on there. Otherwise, no real setup changes required as I see it thus far.

I did see a little bit of "cogging" or low speed throttle issue with the RX8. Can't put my finger on it. Most of the time, completely smooth. Once and a while, not so much. The later seemed like later in the day and thinking it could have been directly related to driveline smoothness or binding in this case. Seemed like there were a few rocks/dirt/grit mashed into the spur affecting the smoothness of the driveline. I cleaned out several teeth once I got to the house and gave it the once over. Powered it up without tires and seemed smooth in the air with no load so hoping all is good there.

Otherwise, should be track ready!

Got to race the truck over the weekend. Went pretty well. Truck is clearly fast. Driver, not so much. lol Still working on setup and getting a feel for racing again as I've been away for several years.

Anyway, truck performed pretty well overall. I did have some motor temp issues though. Wondering if the truck is a little over-geared. Running 16/46, the motor came off at ~170F after a 10min qual. ESC was ~120F without fan and batts were about 100F.

I dropped down to a 15t pinion but temps seemed to be about the same (170 motor).

Curious if it's still over-geared some? Solder connections look solid. No real wire temp. Just hot overall.

Thoughts?

Sorry, haven't checked this thread in a while. I set my LVC in hotwire to cutoff around 3.15 per cell. Yes, and those runtimes are when my LVC kicks in.

Also, sounds like you ESC is fine, it's just your motor working overtime. Make sure nothing is binding or cogging your driveline. Any resistance will make the motor work harder. The motor will still spin at 30k rpms regardless if it's free of binds, or have crappy bearings causing resistance. Roll your trugg on the floor. It should roll very easy. Only mild resistance from the gear mess.

I run 15:46 with Mike's slipper, and my temps have been very cool.

Ya, checked all my driveline stuff. Smooth as can be.

Running the same setup right now. 15/46 with Mikes slipper.

Track is/was pretty tight/technical throughout the infield. Good straight. Loose track conditions so might have just been free revving some. I'm thinking I might go back towards the linear throttle profile to aid in mid rpm/mid throttle drive.

I also have no current limit setup right now. Timing is at zero. No drag brake or push control. LVC is set for 3.2v/cell.

Going to give the connections the once over again and see if anything sticks out.

I've been running a little too hot for my liking too. I run the 1700kv motor on 5s and today after running for about 15 minutes of race conditions my motor was 178 and the ESC was about 158. My gearing is 15/46. Not sure what the deal is. Any ideas anyone?

I raced 3 x 10min with my MBX6T with slipperential, 4s, 2000kv Hobbywing Xerun 150A. Temps were good. Max 60 degree celsius.

I even geared it with a 17t on the 3rd heats.