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View Full Version : Sensored vs Sensorless, observation


GSMnow
07-12-2009, 01:59 AM
Well, the qualifying is done at the 12th annual Hot Rod Hobbies Shootout.

I ran poorly, but it was total fun, and we still have the mains all day tomorrow. Now to the reason for this post.

I decided to race in 13.5 truck and 13.5 4WD. This posed a problem as I only have one 13.5 motor/ESC setup.

I hav read a ton about how people say sensored is for racing and sensorless is for bashing etc. I will say right off the Mamba Max ESC does not like 13.5 ROAR legal motors. The Novak motor I was loaned work far better than my Losi motor, but it still not very good on startup. For these higher resistance low KV motors, the sensors make them start, no matter what. For a sensorless ESC to run start these motors well, would take a very different approach. I will be sending some thoughts to Castle about it. Twice in my 4th qualifier, I got caught up near a hil, and the marshal was nice enough to set me on the up grade, OUCH, the car WOULD NOT pull up the hill from a stop.

Once the car is rolling though, even from a very slow speed, the Mamba Max ESC was much nicer to drive than the Losi Xcelorin sensored setup. The power band is smoother, the control is more precise, the top end seemed to pull higher, and the brakes were far stronger. I found myself driving the MM much omre, havng to control the throttle and keep the tires on the edge of grip, where the truck with the Losi sysem just seemed a bit under powered. I was able to use much more throttle more of the time, to the point I was full trigger far more on track, but I still wanted a bit more punch. All in all, the motors both ran very well so far, I just have the 4WD SS main and the triple main for the Old guys. Yup, only one heat of the geezer class, so it is an "A" main right there with same 3 run format as the big dogs.

After this weekend of racing it is very clear why a hybrid ESC will end up being best. The Losi sensored ESC only has an advantage from a dead stop. Even from the slowest corner on the track, the Mamba Max pulled smoother and harder than the sensored ESC and, at any speed past a very slow crawl the Mamba Max ran very delicate and precise. The hybrid using sensors to get rolling and sensorless smarts for the rest of the power curve sure seeks like a bet of both worlds setup. The sensored Losi system has no trigger feel. It is numb and not responsive. The Max power output of both systems was probably very close. With the tight schedule, I was not able to swap the ESC's for a final test, but I did run the very same motor on both systems t get a feel for the ESC difference. My 4WD and my truck are nearly the same in weight, but the MM 13.5 could clear both triples every lap, but the Losi Xcelorin ESC and 13.5 mot just could not do it after about 5 laps, and even when it was fresh, the Losi system just barely made it where the MM had to be pedaled to not land wide, past the down side of the 3rd hill.

All in all, except for the startup, the MM does a far better job of pulling the motor around. I can't wait until the MM Pro comes out with the sensor port. That should make for one wild drive. Sensored does have an edge for startup, especially in bad situations, such as rolling backwards. I sure hope I don't have bad issues in my main tomorrow, I just need it to stay rolling forwards and not crash. Yeah, like that is going to happen. My old reflexes and depth perception certainly kept me from doing better, and my poor showing does not reflect the ability of the ESC's or my vehicles.

Sensorless works great, if they could just make it start a 13.5 motor better.

ta_man
07-12-2009, 11:38 PM
I have run a Novak 8.5 brsuhless with a Castle Sidewinder ESC and I also thought it ran better than with a Novak sensored ESC.

GSMnow
07-13-2009, 01:25 AM
The mains are done. I ran my best times of the whole weekend in the final mains. I have mixed feelings about the 4WD. Had I run this good, I probably would have been in the next higher main, but then I probably would have been out of the trophies.As it turned out, I got a solid 2nd place in the D main. Yes, the D. Oh well. I ran a full lap more than I did in qualifying, and my times were all much more consistent, though my fastest lap was only 0.5 seconds faster, they were all much closer to that.

The Mamba Max did catch me out one time big though. I spun out in a turn after a jump and it just sat and stuttered, the marshal picked it up and was about to put me behind the wal, but then the wheel spun up in the air, so he went to put me down, where it just stuttered again. OUCH!. I finaly yelled, give it a push. He did, it took off, and I ran the rest of the race strong, with no more hang ups. Motor temp hit 185F with the air temp at 105F in the shade. It only took 1400 mah to recharge the pack to full after 2 warm up laps and a 6 minute race. WOW the setup is very efficient.

As for the sensorless running, I found it far easier to adjust the attitude of the car in the air as well as get the perfect speed I wanted to land the jumps in the right spot and get the right line in the fast sweepers. The Mamba Max ESC has very precise delicate control compared to the Losi Xcelorin sensored ESC. My truck is about the same weight, but yes it is only 2WD, but the tires are much larger so the rotating inertia is probably pretty close. The speed control of the sensored losi is almost course and disconnected compared to the Mamba Max. On the flip side, the steering linkage setup in my truck is actually far better than the modded setup in my 4WD, so it was actually a very interesting trade off. I had very delicate exact steering in the truck, but course throttle, and then my buggy has slightly sloppy steering, but also 4WD and nice tight throttle control. Both had legal 13.5 motors, and I went 1 lap faster in the buggy than the truck, probbaly due to the 4WD letting me put down the power a bit sooner. The lap times averaged about 1 full second faster with the 4WD. Due to gearing limitations though, the top speed on the fast straight was actually a bit faster on the 2WD truck. One more tooth in the 4WD would have helped a good bit, but I couldn't get it in the tunnel on the XXX-4. I went down a tooth in the truck because of the high temps and the very short run ups to both big triples, and that made it so I could cler them for about 5 laps before the battery voltage dipped too much. After watching the winners in the 17.5 races, I picked up a very nice line for hitting them double single instead of the triple and it worked great in the truck. The 4WD had no trouble at all clearing both tripls for the entire 6 minutes race. I only doubled in the 4WD when I had a bad line coming in so I would not hit something too bad.

After this experience, I now know I NEED to buy a proper ESC that uses the sensors for starting the spec motors yet does proper dynamic timing control like the Mamba Max. How much is that MM Pro going to cost?? The Speed Passion GT or the Noseram also does it right, but they are big bucks.Same thing with the Tekin.

Another though....
Hey Castle/Patrick...
After messing with the 13.5 motor and all the settings, I have an idea that just ight start these beasts. When it is trying to start open loop, use a bit more current, say 30 amps or so, but clock from winding to winding much slower. What seems to be going on is the ESC is steping to the next winding way faster than these low KV motor could ever turn at the low current being supplied. And when I do pull more trigger, it also ramps up the clocking speed way too fast for them. Could you add a seting for low KV or give clocking rate choices to fine tune it to a motor? All it needs is a kick to get it to move and then it worked great. As it is, the version 1.17 software worked a little better than 1.21 beta.

SpEEdyBL
07-16-2009, 12:48 PM
http://www3.towerhobbies.com/cgi-bin/wti0095p?FVPROFIL=&FVSEARCH=mamba+max+pro

Too good to be true huh? I just got a tekin T8 1900kv motor, which starts up just as well as the Neu-Castle 2650 on the MMM mainly because they are the same design, both 4-pole 12 slot. But I too will get the MM pro when it comes out use the sensors.

GSMnow
07-16-2009, 07:40 PM
WOW, $128 for the MM Pro!! I will certainly be ordering one for my 4WD buggy. I know I will run 13.5 with it again, it is just about the ideal amount of power for a tight technical track. The MM 5700 motor is faster down the straight, but too much to control in the tight infield. My lap times were almost identical, the starting issues really don't show up on a good lap. I would have liked a bit more RPM, and I am hoping the timing setup on the MM can push it up a bit more, and I will be using a smaller spur next time I have the tub torn down.

rccardude04
07-17-2009, 11:06 AM
Sweet! That may be out by the time I start racing electric in 2012!

-Eric

GSMnow
07-30-2009, 01:17 PM
Tower Hobbies just put the pics of the MM Pro up on their site. Still not holding my breath though.

Back on the original thread. I did more 13.5 motor testing on the MAmba Max and I found something. It appears the blind startup routine in the Mamba Max ESC is just too fast for the low KV motors to follow which leads to the slipping and bucking as the magnetic field from the stator is spinning faster than the rotor can keep up with. I sent a detailed e-mail to Castle about my observation and hopefully they can take a look at it and make a firmware that can start the ROAR spec motors better. This sort of explains why the lower turn motors actually work better. They have a hiher KV, so they turn at a faster rate for a given drive voltage so they can keep up better with the start clocking. It also explains why the moderate to low KV 4 pole motors work better too. They are actually like a motor with twice the KV running through a 2 to 1 gear reduction, so the phase clocking can be twice as high for a given KV. My 3300 KV Medusa 4 pole starts with no complaint at all. The 13.5 is only rated at 2360 KV so it has to clock at 1/3 the rate of the Medusa and well less than 1/2 compared to my 5700.

burnineyes
08-08-2009, 04:21 AM
I can tell you the MMP is one sweet machine! You definitely want to get one of these. Your 13.5 will really wake up compared to a sensored esc AND the Mamba Max. Makes my 10.5 feel like a 6.5 on the long end, with better startup than my old GTB.