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2011-10-23

Things getting done: The beginning of Big Motor

I unfortunately have other things to do than post on the internet but I feel obligated to update this every once in a while so for the maybe one or two people who stumble here by accident so please sit down and enjoy the beginnings of Big Motor (the motor that will supersede small motor). For a scale reference on this motor the air gap OD is 10.5" and the magnets are doubled up to for super poles with 2 magnets per pole, making this a 30 pole 36 slot machine. The model isn't fully done yet, I'm still deciding if I want to attempt getting a second stator of the same type and doing a transverse flux concentrating geometry to avoid magnet reluctance. The attempted result would be a ridiculously high flux linkage and by ridiculous, that is to say something that would just almost saturate the iron with a few 2-5mm of air gap. The operating goal of this linkage would be 1. High torque for low current (hence avoiding magnet reluctance) 2. Avoiding higher harmonics of eddy current losses induced by quickly changing back emf from the magnets (taken care of by the larger air gap). Since these goals are directly at odds with one another some FEMM simulations will be under way to see how achievable this will be. Either way enjoy the picture its Big Motors initial design without any fancy pants transversefluxyness (note: the model isnt done yet).

Big Motor....its big

2011-10-03

Power Supply and Vehicle Update

I have been quite busy with school so I'm just going to post some pretty pictures of some of the progress made towards the electric vehicle and power supply. First off here is the transformer. Because I wanted to experiment it is made of a pair of toroids. It is litzed  because this will be run at ~300kHz min making skin depth and eddy currents an issue. The turns ratio is 4:1 and its meant to operate at 120VRMS on the primary side drawing around 10A minimum.
just the primary
with the secondary

The wire is the same stuff used on my motor, its nice because the low gauge makes winding easy, however it has a gnarly polyamideimide coating with astoundingly good mechanical and electrical characteristics coating which much to my chagrin cannot be burned off in a solder pot or removed with standard solvents such as acetone. The easiest ways of removing the coating without a sketchy solvent seems to be sand paper (labor intensive) or propane (not the neatest). At the moment torching it is easiest despite the bits of semi scorched insulation it leaves behind. However to stop the thermal gradient from crawling up the wires and leaving a bunch of damaged insulation I recommend covering the wires in a wet paper towel up to where you want the insulation gone.

On the mechanical side of things I hacked apart a pair of bike frames to be used in the electric vehicle.

Initial bike frame
It is amazing how much less space a bike takes up once it has been reduced to a pile of tubes; even more amazing is the destructive power of a sawzall on a bike frame.

A pair of bikes that were attacked by a sawzall
Next step in this process is to strip the paint from the tubes so they can be cut up and welded together. To strip the paint I got some paint removal discs; they kind of make me think  a brillo pad and bunch of sanding discs tried to have kids. However after trying them out, the process is a bit more labor intensive than I want it to be and so I might resort to chemical methods.
....however work needs to get done so until next time.

2011-09-10

small motor completed with sensors

The small motor has been done for a few weeks now with hall effect sensors included. so here's a picture.

Looking back on the design its not half bad besides need for the mounting set up, next time the bearings will at least be flush with the motor face if not inset a bit. The next step in this project is to build a vehicle for this motor. I already have an idea in my head along the lines of a mini bike/ scooter, if you've ever seen The Worlds Fastest Indian this will will be a scooter more akin to the motorcycle in that movie rather than a normal bike where one sits more upright. In the mean time I have some bicycle frames to chop into usable tubing and some CADing to do. Also I have a couple side projects and random ideas to post about in the near future with include tranverse flux motors high power AC/DC converters.

2011-08-20

hall effect sensors (yay) + less abominable sprocket mount

So as this is being written those hall effect sensors in my last post are drying in place on the stator with 3 poles in between each sensor woot, hopefully I'll post pictures of that soon enough or at least in a timely manner unlike every other post on here. Those hall effect sensors aren't the only thing happening though. I got my hands on an aluminum round ... more like an aluminum patty it was .5"thick x4"diam. These flat dimensions were ideal for making something well... much more flat to replace the last janky rig. This new sprocket adapter consists of a single aluminum flange with a bit of an inset and some small standoffs, the standoffs are only needed until I get some pan head screws to inset into the base of the flange rather than the current socket cap ones.
On the new flange there are only 3 slots for screws rather than six, six is really over kill. To mill these slots I was going to try a easy method of screwing a fat bolt through the middle of the plate and sticking it in a collet block. Unfortunately that didn't quit go as planned and the adapter lost a chunk out of the side.
Top and bottom before attempt with collet block.

after indexing head and collet block
 Unfortunately the collet really needed to be cranked into the block and we were missing the proper spanner wrench to tighten it in there, as seen above the collet wasn't quite tight enough to hold that bolt. Thankfully the slotting worked just fine on an indexing head.
Sprocket adapter flangey thing from its good side
Despite having a bite out of the side it works just fine.
Anyway hopefully this glue will dry soon so I can:
A. hopefully close this motor and never open it again until it dies a fiery death from over current.
B.post about it. 

2011-07-31

Redoing Things, Also Woot Hall Effect Sensors

So in the last post I was describing my special abomination. But looking at it makes my inner engineer feel bad  so in the near future it will be remade using a single chunk of aluminum that the sprocket can be mounted on. Also small motor is under going a few changes do to the fat assery of the bearings there was a bit of rubbing on some heat shrink so I turned on of the plates to seat the bearing around .125" farther out from the stator. This seems to have fixed the rubbing problem. On a side note all hot glue in the motor used to hold down wires will be removed from the motor after talking to Charles about fears of oozing thermoplastics getting all over the place.

Sexy red heat shrink
But on to something not about me messing up: HALL EFFECT SENSORS (read that again with enthusiasm and a disregard for the preceding paragraph) they tell where the magnets are in the motor which is *sometimes* essential for starting a brushless motor from a dead stop. I'm going to stick hall effect sensors in my motor soon but am currently out of town so I'm ti babble about hall effect sensors for a while. Now there are sensorless motor controllers and sensorless brushless motors, however to start from a complete stand still with a large amount of inertia you want sensors. The sensorless controllers work off of the back emf from the phases, the voltage from the changing magnetic flux tells them where the magnets are and when it is appropriate to turn on a particular phase buuuut to do this you need a bit of a spin to figure out the magnet placement. Therefore in vehicles where you want to be able to start from a stop, hall effect sensors are nifty things. Timing with hall effect sensors is analogous to the timing of cam shafts in a car engine; firing all 6 pistons (or 3 phases if its a motor) at once will get you nowhere but when things are done in the proper order you get rotation.
Generally in a 3 phase sensored motor you'll have 3 sensors. Each hall effect sensors i will work with (ATS177) are effectively flip-flops with some hysteresis and can tell the direction of the magnetic flux through the sensor. Because there are 3 phases and 3 sensors we want each hall effect sensor to be 120 electrical degrees apart (not necessarily physical degrees). The difference between electrical and physical degrees for the magnets is Eelectrical.deg=Physical.deg*polepairs (start at 0 after each 360) note: there are 20 pole pairs in my small motor, because of this there are several theoretical positions to place the hall effect sensors; really though there aren't many practical places you'd want to put them. Below my crappy illustration attempts to show this (for a prettier illustration of almost exactly the same thing see Amy's blog where she pretty much did exactly what I'm about to do), Tm represents 1 magnetic period/pole pair/360 electrical degrees/ the smallest repeatable section to get the proper magnetic pattern. Each colored dot represents a theoretical place where a hall effect sensor could reside. The purple dots represent the closest theoretical placement of the sensors at 120 electrical degrees apart...give or take a bit in the picture.

Motor diagram w/ magnets and hall effect placement
 Practically we want the placement of the hall effect sensors to line up with the stator slots because we physically can't shove them into the 1mm air gap (and the stator phase windings would mess up the readings) so that leaves us two possibilities where the stars align magnet and stator phases line up at spacings of 60 and 120 physical degrees; this is respectively represented by the orange and green dots. One important thing to note is the order of the phases with the placement of the sensors. By following the orange dots clockwise the phases will go ABC but doing the same for the green dots will give ACB. This difference in pattern will make the motor spin in backwards for the same sensor pinout, but that can be fixed by switching any pair of phase wires. Oh and just a note as long as you have 3 phases everything is independent of the winding pattern  but ummmm yeah that's hall effect sensors for now. I'll post pretty pictures soon.

2011-07-14

So I haven't posted in a while buuut um yeah while away I've created some sort of abomination to show who ever reads this. On my motor with its fat ass shaft the OD of the bearings is 47mm and because it's an outrunner everything  that needs to turn must be mounted around said bearing and shafts. Its important to note that thin section bearings would have a full 15mm smaller OD...don't buy bearings at 3 am kids. In addition to the diameter issue the bearings stick out from the surface a bit this makes mounting stuff extremely awkward. Rather than being intelligent and spending a bit of money to buy a chunk of aluminum to turn down to a proper  flanged adapter to fix this, I opted for the cheap approach and used the steel cut out of my magnet can combined with a piece of aluminum scrap which was at one point roughly rectangular and 4 home made standoffs. Which when mounted on the side of the motor form a sprocket on standoffs on plate on a plate on a plate.

Le parts magnet can remnants on motor plate, with in-between plate with sprocket

By their powers combined + standoffs=inception sprocket?
Lo and behold this abomination of mechanical engineering. More later when this thing starts spinning at high rpm.


2011-06-23

Small Motor: IT IS FUNCTIONAL

So this took way longer than it should have but it is done. Stats: ~74rpm/V, ~.13V*s/rad, R(line to line) ~.25ohms, 30-40A max cont. 
Oh, Motor you so crazy 
So it works yay. Down side is it has quite the no load draw at first it was around 6A but then it dropped to around 4A after a bit of breaking in. This high value is probably because some of slight bearing misalignment in addition to some tight lateral forces, they could really use some wave washers right now, currently their snap rings are up against the outer motor plate while the inner ring is on a lip on the stator. That combined with the fact that one of the bearings sustained some minor injuries in a bout of stubbornness and curiosity about how tightly you can fit a bearing in a hole before it dies. When forcing a bearing into an aluminum plate this apparently occurs past the point when the aluminum is just barely flaking from being pushed out by the bearing and the bearing  almost won't rotate from all of the stresses/strains. That poor bearing's suffering will not go in vain for the limited amount of knowledge gained. All subsequent bearings I get my hands on should be thankful for its sacrifices to science. enough of that angent though, Here's a video of the motor working:
video

 Buuuuut back to the rest of the motor, here is the full stator assembly wires. The wires are in a groundless wye configuration and are all tacked down with some hot glue to keep them from rubbing on the rotor.
mmmm statory
After the assembly was completed with wires soldered and the shaft press fit and epoxied in place. All that was needed to finish up the assembly was shove the end plates on the the magnet can with the stator in the middle. Since the stator /rotor are in an unstable equilibrium its damn near impossible just to line up the screw holes without a jig by hand. I found that loosely screwing in one screw followed  by popping the whole motor in a vise with the shaft axis parallel to the vise jaws and the most displaced portion of the stator in plane with the vise jaws and then tightening them. This rotates everything about the screw until the end plates, stator and screw holes are pretty much concentric on their respective axes allowing everything to be screwed together yielding a sexy completed torque machine. More shenanigans regarding the state of this motor will be posted in the future.
The aforementioned complete sexy torque machine

EDIT: changed title

2011-06-16

Small Motor: Building for Stupid

In addition to a large motor that will be created there is a small motor in the process of being built and by small I mean relatively small like with a 4" diameter stator rather than 10.5". This stator contains 18 slots and was wound in an AaABbBCcC pattern with x10 24 gauge wires in parallel. The large number of smaller gauge wires exist because the first time winding this stator the obnoxiously stiff properties of 16 gauge wire were discovered. Thicker wire tends to bow out around the poles making tight packing of wires difficult. To accompany said stator is x20 .25"*.5"^2 magnets with an air gap of ~.75mm.

Small Stator with shaft collar insert

Here's the small stator that shiny piece of aluminum in the middle is there because I didn't have any long 1.5'' diameter chunks of metal and wasn't about to buy any. Its an epoxied press fit with a make shift key, which is a steel peg glued into a hole milled on the the border of the press fit.

Small stator with milled peg hole and peg.
To  to make the stator mechanically complete on more object is needed : a shaft and not just any shaft, a shaft built for stupid and by built for stupid that is not to imply this motor is made for someone a bit slow. By built for stupid I mean both rugged and ridiculous to a stupid extent. Why? because having ridiculously over built things gives me the same satisfied feeling as holding a sledge hammer. From a similar perspective it also allows said motor to be ridden or used 'stupidly' purposes in which a less mechanically sound object would die a horrible death. Also from a practical stand point this motor has ~15gauge equivalent and will be wound in a wye configuration and needs room for that fat hunk of copper to come out somewhere. That being said this meager motor is getting a 20mm shaft.

Magnet can, stator and shaft
By their powers combined this thing will hopefully be completed soon. 

2011-05-21

Imma make a motor :D

Motors are fun they make torque and in my experience with assorted wheeled objects the relationship has been: more torque==more fun (or pain and death) and there for more torque==more better. Transitively motors kick ass. Currently a project have going is making a brushless DC motor and have obtained 2 stators to do so.  

Smaller stator and larger stators have 4" and 10.5" OD respectively and are replacement parts for an atv and a LG washing machine which appears to have been direct drive. The large stator is actually wound really beautifully unfortunately its with single strand ~24 gauge in a groundless wye which could be used very conveniently with AC voltage supply, it also manages probably 50+ turns/pole (at least) gives a ridiculously huge torque constant which is generally a good thing; but on the down side this will make the motor will be really really slow unless it has ridiculous volts running through it but that is a pain in the ass. So in order to get high(er) power out of this motor by running it at higher RPM it will need to be rewound with some thicker gauge wire allowing approximately similar torque from more amps and a lower required voltage.

Been a while...but I have pictures



This is the first motor controller it worked wonderfully...for a while.

2011-02-10

time to babble

So in some attempt to record and make sure my own engineering and attempted EE shenanigans don't all wake from the dead like unloved robotic zombies after becoming out dated like the lost portions of Dexter's Lab and make run on sentences because who needs punctuation; this blog is being created. Whatever future people read this I hope you learn somethign from my excessive amounts of stupid and experimentation.

Also thanks charles and shane who are pretty much the reason why this blog exists and who will be linked to profusely in the future.


which brings about one of the main subject that will be on this blog MOTOR CONTROLLERS. Those things are handy as balls man you can like control motors and stuff... yeah. And ohmygod so many things can go wrong with them. Like most devices made handling large amounts of amperage and highly inductive loads there are more than enough easy ways to destroy things. That being said 2 homemade creations have already died and the importance of a remembering a fly back diode has been burned into some poor mosfet's memory for all eternity. Unfortunately it decided to take some other IC's on the board with it.

pics to come