Another MBX6T Race Build.

[itbvolks]

Ted,

Curious what your running for esc settings on your RX8?

[itbvolks]

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!

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.

[tedo]

Originally Posted by itbvolks

Ted,

Curious what your running for esc settings on your RX8?

-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...

[itbvolks]

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 ;)

[tedo]

Originally Posted by itbvolks

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 gains to be had.

Any need to really baby the new setup (batts /motor)?

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

[itbvolks]

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.

[itbvolks]

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).

[George16]

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

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

[itbvolks]

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

[itbvolks]

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!

[itbvolks]

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?

[tedo]

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.

[itbvolks]

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.

[Sower]

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.