bitPimps.lixlink.com

OK, though I'd jump on the old micro-t bandwagon myself! lol....

I got mine yesterday and didn't take long in busting it open to get to the goods. I've had a good look at the motor and a partial look at the electronics. More on the motor for now though....

MOTOR

The Micro-T motor has actually got some balls to it. I took it out of the chassis and put it on my ICE charger since it can do a motor break in procedure. Here's the results.

1V drive, motor would stall, not enough to start rotation.
2.4V drive, current draw = 0.36A (approx)
4.8V drive, current draw = 0.5A (approx)

Wow, now these values are read at no load. They are the values the ICE settled on at the end of a 15 minute break in. I measure both motors to check and these are the averages.

500mA drain at 4.8V with no load is a lot for what we're talking about here. Considering that a stock kyosho mini-z motor runs in at approx 350mA the Micro-T motor is quite "hot" in that sense. I see this motor easliy hitting 1.2 - 2.5A in current drain whilst being driven around. If no load current is 500mA then it makes sense for the load currents to be quite solid. I can see why Losi put a 2x2 MOSFET stack on this thing. If they are going to release a "hot" motor then god knows how much that will draw.

Here's some pics comparing the motor's size. The Micro-T motor is in the middle, the motor on the left is your typical N20 type, the motor on the right is a typical 130 sized motor. The shaft on the Micro-T motor is 1.5mm (approx, going off comparisons to other shafts).




One thing to note is that the shaft on the end of the motor is grooved to allow a nice, solid grip on the pinion gear. I had to file this down so I could remove the armature from the motor can. In doing this I made the pinion gear join loose. I used some threadlock to seal it in and it's all good now but BE WARNED! You can't take the armature out of the can without filing down the grooves on the shaft.

The armature surprised me. It seems to have some globs of glue on it, like it's been bloody balanced! lol...



I'm doing a visual guestimate but I think it's around 30 - 40 turns. That's just a guess, I ain't gonna kill this motor till the spares come in, lol...

One thing that might please the punters is that the armature is VERY similar in size to a HO Slot Car armature. This may open up opportunities to easily make modded armatures without sacrificing the original "stock" armature. I dunno yet.
There are a few little differences. The commutator on the losi motor has a slightly smaller diameter than the HO slot car armature. Also, the losi armature has 1 or 2 more laminations around the shaft making it a little longer than the HO armature.

HO motor shafts will not come with the groove in them, therefore making them a looser fit on the pinion gear, ie: "not snug". Again, shimming up the shaft with some glued on foil or threadlock may work.



The magnets in the Micro-T motor are quite strong. I would almost think neo magnet strong since I've never seen a ferrite based magnet that small with such a strong magnetic field. Not much else to say here. The magnets are clearly custom for this motor type and prolly can't be modded/swapped out easliy.

LBRC, you might like to know that those small arse bearings you sold me ages ago mate look like a perfect replacement for the metal bushing in the steel part of the motor can. The bushing in the endbell is too small to "drop in" one of those bearings unfortunately.

ELETRONICS

Some tests with my DMM showed that the MOSFETS on the top and bottom of the PCB right next to the motor wires (pink & blue) are wired up together in the format of a 2x2 MOSFET stack.

Whilst I'm yet to test signals 'n stuff, It looks pretty certain that mini-z aftermarket MOSFETs will work. You could put in a 2x2 stack of Si4562s or IRF7317's. There's no proof until it's tried of course. As I said, there are still some unknowns in regards to gate drive, gate charge times, etc, etc...

Here's what I'm talking about. This pic has been edited with the bottom side flipped up to match the top layout for the motor wires. It shows you that they're both clearly connected with a fair few via's (holes through the PCB that carry current) linking the two sides together....



More to come...... I still want to test a few more things. Maybee rewind one of the motors. We'll see.

I definately want more speed but. I mean it's a sorta "nice fast", but not "ph2t fast", if you get my drift......


ph2t.

Just the person I needed to hear from on the Micro-T!!

I might as well start selling my blood now.

Anyone need a moderately used lung? Willing to trade for a few Micro-T's.


If you've got one of these, things can ONLY GET BETTER!!

definately want more speed but. I mean it's a sorta "nice fast", but not "ph2t fast", if you get my drift......

Yeah, we've all seen ph2t fast.

Thanks for the write up. Very interesting read.

Great write up man
Just don't make it too ph2st it's pretty fast already

Stuck the motor in a Orion Motor Performance Monitor with interesting results.

4.8 volts with no load except for the sensor: 20,000 rpm, 1.4 amps

Ouch, even though the sensor wasn’t a perfect fit and I was holding the motor by hand which also tends to slow the motor down and cause the current to go up it still confirms the need for parallel mosfets, these things run hot.

I knew it! Freakin hot aren't they.

A BB mod of some kind I think will be a must. Should improve runtimes at the very least.....

I wonder what an aquaspeed motor (mini-z boat) armature just "dropped in" to the micro-t motor can would perform like?

The timing ends up being a problem; the brushes on the Aquaspeed are 90 degrees out from the magnets while the Micro-T's are inline so the comm ends up being about 30 or 45 degrees off, which is just a bit far to rotate it without breaking the wires.

Also the shaft is 3mm shorter but since the pinion is put on backwards that’s not much of a problem.

I was thinking it would be possible to throw a set of AAA li-ions in there, but seeing the high amp draw, I figure it would be better if Lipos were used.

ph2t wrote:... You could put in a 2x2 stack of Si4562s or IRF7317's. There's no proof until it's tried of course.

Tried and they work, or at least the motor turns without smoke.

Had another wheelieless wonder brought to me the car seems to have average runtimes but is a tad slower than mine and will not wheelie even with the small pinion and a 7.4 volt LiPo pack which easily sends mine into a back flip if you get aggressive with the throttle. Swapping the motor and loosening the transmission didn’t help so it seemed like a good excuse to try and see if four 4562’s would make a difference. Will have to wait until morning to see if there is any improvement, for now the motor turns and the FETs stay cool which is always a good sign.

Lead Free Solder,
With lots of room and no need to stack them it would seem easy to swap out the FETs wouldn’t it? But NOT! The problem is that the Micro-T CB is one of those nice new RoHS/ISO compliant lead-free pieces of shit, the solder has a much higher melting point making modifications and repairs difficult to say the least. As soon as people start trying things are going to get ugly, I predict a rash of lifted-pad-itis, with it’s accompanying frustrated rages and tears of morning. Ok I admit it I lifted a pad and had to repair it

LBRC wrote:Ok I admit it I lifted a pad and had to repair it

I freakin' hate that! I didn't know about that new lead free BS. Thanks for the heads up.