The cooked MAC repair thread!

[Spicerack]

Thanks for the info Paul- I shall get onto it in the next couple of days and see if I can get the old halls out. Yes, I'll take care with the motor- I've been told it can be very painful if you get bits trapped in there

As you can see peeps, this is why you should buy Cellman stuff- you know that you're going to get good support...

[Spicerack]

Hi Paul,

Is there any chance Paul you could install a temp sensor and some kind of display so we could know when to stop? That might save a lot of motors. But I've put 3500 watts into the phase wires and not got them hot, warm but not hot!

I shall be installing my own temp guage. Just a simple lcd display one- ebay for a few bucks. I'm drilling another hole in the axle from the other side- one phase, hall lines and temp sender line in one side and two phases in the other. Phase wires will be unneccessarily large at 10 awg. I'm only doing the temp thing out of curiosity- once I've got my amps in check it will be fine. Most people won't need to know as long as they are sensible and don't overvolt their motor. Not sure how many of those people exist on ES...

[Lebowski]

Is the new EB3 a sensorred or sensorless controller ? Do you offer sensorless for the Mac ?

[o00scorpion00o]

Hi Paul,

Is there any chance Paul you could install a temp sensor and some kind of display so we could know when to stop? That might save a lot of motors. But I've put 3500 watts into the phase wires and not got them hot, warm but not hot!

I shall be installing my own temp guage. Just a simple lcd display one- ebay for a few bucks. I'm drilling another hole in the axle from the other side- one phase, hall lines and temp sender line in one side and two phases in the other. Phase wires will be unneccessarily large at 10 awg. I'm only doing the temp thing out of curiosity- once I've got my amps in check it will be fine. Most people won't need to know as long as they are sensible and don't overvolt their motor. Not sure how many of those people exist on ES...

Well to be honest, my 320 rpm mac never got hot only on one hill for a few miles at full throttle 32 mph, I was astonished how fast it can climb hills, the mac is so powerful at 3.5kw makes the magic pie seem a lot slower for the same power!

I think more voltage is better than current in some applications, because 3500 watts on 60 volts is around 60 amps battery current and 3500 watts on 36 volts would be 97 amps, that's a hell of a lot of extra current, and at 36 volts the motor has a greater chance of bogging down, creating even more heat. So I think 60 volts is a sweat spot for the mac, by my experience, I have not burnt the windings at all they look as new!

I damaged the clutch and key way, but Paul has (or nearly has) a new axle with a much tighter key way fit, I'm not sure yet if he has the newer design clutch ?

I know Paul does not recommend the mac above 52 volts, but I think I would rather more volts than dump more current. With the mac you need a lot less current than with direct drive for the same torque, so I think people automatically assume they need the same power with the geared hub!

I did a range test one day with the mac, no pedalling at all at 20 mph and got 25 miles out of 8.5ah, that's impressive!

[fechter]

I'm only doing the temp thing out of curiosity- once I've got my amps in check it will be fine. Most people won't need to know as long as they are sensible and don't overvolt their motor. Not sure how many of those people exist on ES...

Nobody I can think of. Temperature sensors are cheap anyway.
Ideally the sensor should be tied into the controller to start lowering the current limit when it approaches the maximum allowable temperature. This will allow the maximum possible power without melting anything.

[stripedtuna]

Ideally the sensor should be tied into the controller to start lowering the current limit when it approaches the maximum allowable temperature. This will allow the maximum possible power without melting anything.

What a great idea..

[Spicerack]

Yes it is a good idea. I shall be linking mine in to a light processing unit, central neural net and an electro-mechanical throttle limiter. So if I see the temp get high, I'll think "oh sheet" and close the throttle!

Happy new year everyone by the way!

[stripedtuna]

a light processing unit, central neural net and an electro-mechanical throttle limiter.

Lol,

took me a few minutes to get it.. im a bit slow after a few cold ones..

Happy new year too mate.. good luck with the Mac fix too..

Cheers,

Tuna..

[cell_man]

I have done some investigations into temperature sensors and there is a sensor available with a linear dc output proportional to the temperature, driven from 5V so I assume it could use the 5V hall supply, but haven't tried it yet. I do intend to get some and start having a play with these. The new CA has an option to fit a pot onto the 5V supply that allows the speed or current limit to be adjusted on the fly. Can you see where this might be going....

Like I said I do now have a few of the double width stators available. I will try to arrange the parts to get a couple of prototype motors up and running. Maybe use a welded clutch as I think such a motor would likely be a bit too much for a standard clutch. Standard 500W stator is 21mm wide, these doubled up stators are 42mm. If you maintain the number of turns, a wider stator will be slower all things else being equal than a thinner stator, so I'm guessing this double width stator might be better used on higher voltage, or it will end up being a crazy small number of turns and therefore a hard load for the controller. Higher voltage will keep current levels more reasonable, so giving the phase wires an easier time as that is a bit of a bottleneck.

The Mac is a 16 pole motor as is the BMC and Ezee. Bafang and most other small geared hubs are 8 pole. there is a 5:1 gear reduction to figure in to. The high frequencies (80 cycles per wheel revolution) and the relatively small teeth in the stator means that the flux density in the stator can be quite high. This is why the Mac et all tend to have quite high no load current, it's also why they have good low down torque, you win some, you lose some. Stator losses cause heat in the stator and means that the motors are practically limited by stator losses to a maximum wheel rpm of about 550-600rpm. A higher grade stator material will have less stator losses, so should run cooler and be more efficient, at least at higher speeds. It can maybe also allow other aspects of the motor to be optimised as the stator is no longer the limiting factor, which could possibly further improve efficiency and therefore power handling. Anyways, as soon as these new stators arrive I will get some wound and see if theory follows through with hard figures produced on the dyno. I'm no motor expert, far from it, I have a lot I need to learn, but I have always liked to tinker and make the best of things. The Mac is already a nice little motor, but if it can be better even if it does add a little additional cost, it's all good IMO.

The EB3 I sell are all with sensors, but sensorless is available in the EB3. The Mac is a 16 pole motor, and I don't think sensorless controllers work very well with them, although there is no reason a very good sensorless couldn't work perfectly. Andy is I think the only person that I can think of that has burned the phase wires like this and it was only this that resulted in the damage to both halls and the controller. I've abused a Mac pretty bad to where the windings were very discoloured and smelly and the windings finally gave up, but the hall sensors still worked ok. Mac use the Honeywell ss41 sensors, they can take some abuse. I have had very few hall sensor issues with the Mac and most of those were not due to heat damage, almost always another cause.

[Lebowski]

The Mac is a 16 pole motor, and I don't think sensorless controllers work very well with them, although there is no reason a very good sensorless couldn't work perfectly.

Now this is a challenge have to get my hands on one of these ...

16 magnets and a 5:1 ratio, doesn't that give 40 cycles per wheel revolution ? Does the mac have 16 magnets or 32 ?

A crazy small amount of windings, there's a second challenge I got my
controller to work with 5 windings per phase (on only 3 of the 12 teeth)
in a small RC motor...

viewtopic.php?f=30&t=34231&p=510965#p510516

[o00scorpion00o]

Interesting stuff Paul,

The double width stator, I take it that will substantially improve torque, with similar top speed ?

The mac is a great motor, And I can't wait to fix mine!

The biggest thing is the clutch, axle and keyway. 2 keyways I think would really help.

Paul do you have any more information on the bmc V4 clutch ? It looks like it can take a lot of power, can you get your hands on them ?

Welding the clutch is fine, obviously you loose free wheel, but I love the fact the mac is small and lighter and I can pedal.

[Spicerack]

Took the motor a bit more apart so here's some pics. Great info there btw Paul!






You can see the brown scuff mark on the bottom right of the picture. This is where a few of the windings have been rubbing. I may give this area a little tickle on the lathe. Probably related to overheating the windings which would have made them grow a bit and touch the casing.


You can see a few of the rubbed winding wires here. The winding wires should be a nice coppery colour too, not the dark brown I turned them!

I quite amused by the fact that I'm the first one to abuse a Mac this badly! That must make me special or something.

[The Mighty Volt]

Slightly off topic but this concerns a cell_man product, namely the 24v Ananda, I was just wondering what the voltage and amperage limits of this motor might me, i was hoping to run it at around 750w {36v 20a} with peaks of 50A just for fun, and just for a few seconds too.

[stripedtuna]

Wow...

nice quality pics mate. Far out...

So you reckon running too much power through the motor could cause the windings to swelll enough to rub the case? Such a close clearance these things must have.

Anyway, i didn't find the pics of working Mac pulled apart, but did find another cooked one..

bigmac.jpg (30.22 KiB) Viewed 705 times

Now thats the cooked Big Mac i'd rather have in my garage..

Are you going to have a go at rewinding it?

Cheers,

Ed.

[Spicerack]

mmmmm Maccas......

Ed, I'm going to try to not rewind the motor at the moment- I'll give it all another coat of winding varnish and replace the halls and wiring. If I do have to rewind then I will but I'd really rather not- have you seen how many teeth there are on that stator?

[stripedtuna]

Fair enough..

Rewinding does look like a lot of effort..
Probably better to do some more overtime at work and earn the money for another wound stator, now that i give it some thought.. lol
Hope your fix works mate.. been watching this story from the beginning.. In fact your original build thread was one that helped my decision on my first build..

As long you fix the clearance between the winding and the case, i reckon you got a good chance of winning..

ANyway,, I am definitely learning heaps from your thread..

Thanks,

Ed.

[Spicerack]

Fair enough..

Rewinding does look like a lot of effort..
Probably better to do some more overtime at work and earn the money for another wound stator, now that i give it some thought.. lol

Unfortunately all my overtime at the moment is so I can buy more RC toys (1/5 brushless buggy from Hobbyking, more Helicopters etc etc). My wife thinks it's money for the house/holidays/kids but she is wrong.

In fact your original build thread was one that helped my decision on my first build..

Don't know why! My build is nothing compared to most on here- there are some really really awesome bikes out there. I now want a mac powered, cromotor powered, mid drive setup and friction drive lightweight commuter in my stable! Dammn you ES!

As long you fix the clearance between the winding and the case, i reckon you got a good chance of winning..

Have big metal lathe in my shed. There will be no clearance issues.

ANyway,, I am definitely learning heaps from your thread..

Thanks,

Ed.

Thanks to other knowledgable people like Paul- he is a wealth of knowledge- especially on the MACs.

[neptronix]

Thanks for the info Paul, I can't wait..

No clutch on the BIG MAC will make for a lot of motor drag, but when you're trying to brake from over 30mph, It will be very welcome to help stop you And if you're going to go under 35mph regularly, just stick with the regular MAC motor..

Andy, I do think you are the first to beat one up like this. I have ran 4kW a few times, but never for longer than ~10 mins, and never on a hill. I think the heat just gradually builds up without you knowing about it.

It's good that something went before the windings. A rewind would have been interesting, but oh well

[Spicerack]

Ok, thinking caps on please.

What is the definitive way to test windings?

What I'm getting at is that it looks like some of the winding varnish has melted and run off the wires- so there may be shorts between wires as they are wound around the stator teeth. I don't want to fix it all up with modded axle, new hals and wires etc if the windings are compromised and it makes less power.

At the moment, I have tested between the phases and stator- no shorts there. Each phase to the other two gives me pretty much short circuit (0.4 ohms on my mid-range meter) which I thought was about right? Is there any other way to see if the windings really are ok?

[Spicerack]

Ok. Axle time.




Note I am wearing the appropriate safety footwear for using machinery.



Still needs a little bit of smoothing with a die grinder/dremel.

Certainly not a job for a novice though. I am lucky enough to have a decent lathe and other tools. The only thing I don't have is a cnc mill but it's on the list!

[fechter]

Shorts between turns will be hard to detect. A fancy inductance meter would be one way.
Another way is to install the rotor and spin it. If there are shorted turns, there will be a lot of drag when spinning the rotor. The shorted winding will get hot if you spin it hard enough.

My experience is shorts almost always happen between the windings and the laminations and rarely between turns, so if you have no continuity between windings and laminations, that's a good sign.

[Spicerack]

Thanks Fechter- the motor certainly wasn't cogging badly and was spinning ok, just not under its own power. I'll probably repair what I can see and go from there.

[Spicerack]

The halls pcb comes off pretty easily. Use a very small gas torch to cook the epoxy coat which will then peel off. Desoldered, bit more heat to soften the epoxy holding the halls in and they're out too.


In with the new


Yes the crusty looking cap will be getting replaced!

Ready for soldering and epoxying everything together.

[Spicerack]

Finally got a little bit more done on the motor

Got all the wires through- two phase and temp sender in one side and one phase and halls in the other. Since this photo I machined a wire slot in the newly drilled side of the axle.

You also need to widen the slot in the aluminium stator locating plate for the new bigger wires. I did this with a dremel and die grinder in less than a minute.

Everything then got a liberal coat of clear high temp engine enamel-couldn't be bothered trying to find winding varnish and this stuff will do a good job- rated to way higher temps than it will see (now that I know what's going on in there)



Bit fiddly to get the wires sitting neatly in the motor with it all back together but there it is- clears the side cover nicely and everything will be held down with epoxy. Yes the blue phase connection will get a bit of heatshrink as well.... Note the temp sender about 5 o'clock [EDIT: I've since replaced this with a higher temp unit as this one maxed out at 70 celcius.Duh. See page ?6?]. The phase wires are all Hobbyking Turnigy 10g with the silicone stripped off and replaced with heatshrink. Tight fit but they are in! You def need to drill the axle both sides for this mod. I so hope the motor still works!

[fechter]

That looks brutal

I'd suggest testing continuity from the end of the hall cable to the pads for the hall pins to make sure they all made a connection.

There isn't much clearance for the wires and they tend to rub against the rotor. I like your epoxy approach to hold them down. I hate stuffing the wires though that 90 deg. bend in the hole. I wish they could have run them in a slot along the outside of the axle like an X5 motor.

I was tempted to make a ring of holes in the rotor that sort of line up with the windings to allow air to pass through. If there is enough clearance, there could be some vanes along the edge of the holes to turn it into sort of a fan when it spins. This would help tranfer heat away from the windings and to the outer case where it can be dissipated.