Cooling a Mac hub motor

[ohzee]

I actually have the same type of issue with my Mac. Ive also ran it at 24s so I have beat the crap out of it.

In the process of fixing a new mac 8t with a new stator/axle that will fit in my mid drive.

I really wish I could find a DD motor of the same size as this thing has to many limits for myself.

 

[cal3thousand]

I actually have the same type of issue with my Mac. Ive also ran it at 24s so I have beat the crap out of it.

In the process of fixing a new mac 8t with a new stator/axle that will fit in my mid drive.

I really wish I could find a DD motor of the same size as this thing has to many limits for myself.

Same size how? diameter wise?

 

[cwah]

The new Macs with composite gears do make more noise than the older ones, and definitely more noise than a DD. Overall they are still very quiet compared to old Currie style motors with steel gears (think of a powerdrill).

I wouldn't call the Mac sound a bad sound. It's most noticeable if you get a tailwind on a hill. Maybe take a video of yours?

Had a problem with my controller with reverse polarity (http://endless-sphere.com/forums/viewtopic.php?f=2&t=41825). As soon as this gets fixed I'll post a video of the mac

 

[ohzee]

Yea that would work in my urbancommuter kit. I am told an aotema would work , but it needs a modified axle.

 

[Stryker16]

Cellman installed the temp sensor which one is connected to one of the hall wires (I think) and the other wire comes out of the 6th unused slot in the hall plug. So using a voltmeter on these leads, you will get a readout of 1v = 100 deg Celsius. I have my bike setup with my multimeter strapped in my front basket, with leads connected. All I do is turn it on to check the temp. A smaller voltmeter would be nice, but I can't seem to find such a thing.The highest I've seen in .87. If I go over 80, I tend to try riding slower to let it cool. I'm pretty sure I'm babying the motor, but I like things to last. The controller is another story, I don't have a temp sensor and it can get quite hot too. Time will tell if it's an issue I guess.

can you tell me which wires to test with the multimeter? i have tried and tried getting a voltage off of the hall sensor connector and keep getting voltages of 3.5, 4.5, etc and at room temp i should be getting around .23 volts

 

[itchynackers]

Don't forget that the motor is seeing much higher than 90°F ambient temps. A foot above the road on a Texas summer day, I'd add 20 degrees and that might not be enough.

MWKeefer has been using oil for cooling and lubrication in his geared hubbies for years. Makes them more quiet too. Look up his discussion from a couple of years ago. FWIW, his testing came up with no significant benefit for DD's.

Hopefully my liquid cooled motor that made it up Pikes will count as "significant benefit" one of these days.

 

[Stryker16]

Cellman installed the temp sensor which one is connected to one of the hall wires (I think) and the other wire comes out of the 6th unused slot in the hall plug. So using a voltmeter on these leads, you will get a readout of 1v = 100 deg Celsius. I have my bike setup with my multimeter strapped in my front basket, with leads connected. All I do is turn it on to check the temp. A smaller voltmeter would be nice, but I can't seem to find such a thing.The highest I've seen in .87. If I go over 80, I tend to try riding slower to let it cool. I'm pretty sure I'm babying the motor, but I like things to last. The controller is another story, I don't have a temp sensor and it can get quite hot too. Time will tell if it's an issue I guess.

can you tell me which wires to test with the multimeter? i have tried and tried getting a voltage off of the hall sensor connector and keep getting voltages of 3.5, 4.5, etc and at room temp i should be getting around .23 volts

well paul got back to me last night and it seems as though the 'unused' wire and the ground wire on the halls are the two i should be probing. problem is i am getting 3.5 volts from these wires anyone have any ideas what is going on? i guess I'll have to open the motor up and look at the sensor and see if it is connected properly/and or defective

 

[veloman]

Stryker, ask Paul if he calibrated it to 1v = 100c


Well I just did 44 miles this morning (average air temps around 80-85 F on the way home. I pedalled a lot to make sure I had enough range. I ended up averaging 18.2mph and just 14wh/mile. The trip out was easy, tailwind and motor stayed around 60 C, I averaged 10wh/mile. The return trip back included carrying a mtn bike on my back, and into the headwind. Motor temps quickly went above 80 C and I had to stop twice for 10 minutes to let it cool down. Max temps were 87 C, averaging about 19wh/mile or just 360 watts battery power. I rarely pulled more than 700 or 800watts during this ride.

It's one of two things:
1) I am babying the motor and I should let it go to 100-110 C and not worry.
or
2) This motor's average output rating is FAR BELOW 500watts, when the ambient temperature is reasonable 80-85 degrees F.

I'm really getting soured on the Mac, for any sustained riding. It just seems like it can't handle any real distances, at least not in summer. I am planning on getting a 9c DD to not worry about temps at my low-medium power levels. If I run 600watts average battery power on the Mac at an average of 25mph, after 12 minutes it's near 80 C.

 

[alfantastic]

For Pete's sake stop worrying man and just enjoy riding yer bike.
I've been running my MAC fairly hard for the last 1000 miles, peaking 1500 watts.
If she blows, she blows :lol:

 

[veloman]

Sorry, I don't want to ruin a $375 motor. I use it for transportation and it does really well, even when it does get to 94 C, it didn't feel weaker. You talk about power, but that doesn't mean much. What temps are you seeing? I run 1300w peak normally.

I'm sure the high temps make the gears wear more, but who knows if it amounts to anything. It seems no one really knows the safe limits as it is. Something in the 90-110 C range.

 

[alfantastic]

Sorry, I don't want to ruin a $375 motor. I use it for transportation and it does really well, even when it does get to 94 C, it didn't feel weaker. You talk about power, but that doesn't mean much. What temps are you seeing? I run 1300w peak normally.

I'm sure the high temps make the gears wear more, but who knows if it amounts to anything. It seems no one really knows the safe limits as it is. Something in the 90-110 C range.

Fully understand mate, I only use mine for a bit of fun, so not too fussed if it pops.
I do have complete faith in the composite gears though, and I reckon they can stand up to a fair bit of abuse and heat.
Unfortunately my 10T doesn't have the temperature mod, but I do labor it regularly up a couple of 15% hills for about a minute at a time and it's still not bit the dust.
I think the key to longevity on the MACs at all power levels is gentle and progressive use of the throttle.
I never fully open the throttle, unless the bike is travelling at least 10 mph.

I've probably just jinxed my bike...... tomorrow BANG

 

[veloman]

Yeah, I always ease into the throttle, and I have the phase amps set as low as possible to reduce starting torque (still kicks you off the line).

Back to how to cool a Mac - drill 2 holes in the freewheel side, sized to perfectly fit some rubber plugs. Keep the plugs in (keep out dirt/rain) except for when you hit 75+ C. No need to have them out all the time, at least for me. Most night rides and most of my trips are short enough that I don't go above 80. Why risk letting dirt in when not necessary? But it's no question there needs to be some venting. It just smothers itself with no air circulation.

I will try this using my old cracked side cover and see how it goes.

 

[Stryker16]

Stryker, ask Paul if he calibrated it to 1v = 100c

his response was ' If it is not reading the correct value, it may not have been connected properly or it may be faulty. I'm sorry, if you can have a quick look and see what you can find. It only has 3 wires, 5V, 0V and signal output.'

so i guess i will have to open her up because i have tested the connection 5 times now and it keeps reading 3.5v ill open tomm night and see if something looks obvious but not sure right now. just wondered if it had happened to anyone who installed a LM35 before.

 

[Stryker16]

just an FYI in case this ever happens to anyone else. vsupply was hooked to center pin which is v out (and v out was hooked to ground, ground hooked to v supply)

 

[Kin]

If you need to calibrate the temp sensor, leave it in an temperature controlled room, then compare the measurement to a known to be good temp sensor. A lot of voltmeters have one built in.


Subbing this thread to see if anything new comes up about cooling the MAC

 

[bionicdan]

A smaller voltmeter would be nice, but I can't seem to find such a thing.

Hows that for small
http://www.ebay.co.uk/itm/270982507618?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
or blue
http://www.ebay.co.uk/itm/200861232970?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
or housed
http://www.ebay.co.uk/itm/290717802952?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

This is what I have bought for my mac when it arrives

I would quite like some 8mmx4 holes inbetween the spokes with a vent directing air inside the hub as the wheel rotates forward with mesh to inhibit large debris. Maybe lined up with the spinning stator/magnet part. I often picked up what looked like magnetic stones on magnets as a kid just on the roadside.

Oh hold on I live in england and its 3 degrees in my house right now, thats my cooling method cruddy weather lol

 

[Spicerack]

I know it's an older thread...but it's been relivened so I'll add my bit.

I tried air cooling and found it made no difference. Our problem is the gears- you don't want dust in there as it will wear the gears down, so I put foam filters in the inlet holes (which had scoops on to try and force the air in).

I've oil cooled mine (in sig) and have very little leakage and it allows me to maintain 2Kw and run at 70-80 celcius.

 

[bionicdan]

Now I have seen the oil cooled discussion I think that looks like a good idea cheers (more sleepless nights thinking).

I would like to drill out a single hole between the spokes and then slightly dremmel a v shaped oil catchment channel inside. Then up to 3 or 4 twelve inch coils of 6mm copper pipe attached to the spokes. The centrifugal and rotational force should create positive pressure that spits it back in the cassette/gear side onto the coils. Perhaps via 6mm rubber tubing to avoid touching the cassette while trying to get down behind it to the center where its needed. I might find something ring like to try to distribute the oil onto several areas of the coils. But hope the pressure from the spirals spinning will push it out at a fast rate to cover everything. I might do a test with fishtank air hose filled with water and my bike upside down to see how far it squirts oh er.

Have you ever used a water barrel walker pump at camping places. it looks like a grass flattener but has coils of hose inside that pumps the water out as you walk. Looks a bit like this

Then you would only need enough oil roughly to fill the copper pipes. It might be less likely to leak out and move the heat from the hub entirely rather than trying to pass it to the body where the composite gears contact.

Then a second vent to release pressure is fed into a very small catchment tank that can be aligned above the wheel over night so the few drops that went astray go back inside. So the tank would have two pipes, an air inlet (plus minor oil drips) and an air outlet only. If the air output release hose was fed into the center of the tiny tank, air could escape while retaining oil. Might have to make it, or modify an inline fuel filter but something of this shape and size

Once I have my motor and test it up my 400feet 18% hills I may not have to worry but I do like my stuff to last as long as possible. I would rather take it apart once every three years to replace oil (or just install the system) than every year to replace parts.

Has anyone decided if these oils degrade the coil lamination stuff yet?

 

[Spicerack]

My motor has been runnin oil for nearly a year with no dramas.

As for your plans, gee whizz. You don't like the kiss principle much, do ya!

I really can't be bothered thinking about if your idea works as the way I did it (and multiple others have) works. I'm not being rude- just trying to save you a stack of time!

Ultimately of course if you want to push for more power then the little mac is not the right choice- a bigger dd is the go for that.

 

[veloman]

Its good to read more about this. I am back riding the Mac as its mostly under 75 degrees outside. Love the acceleration of these...

Btw, I'm not running any torque arms on my rear Mac, 1350watt peak, steel dropouts.

 

[bionicdan]

My motor has been runnin oil for nearly a year with no dramas.

As for your plans, gee whizz. You don't like the kiss principle much, do ya!

I really can't be bothered thinking about if your idea works as the way I did it (and multiple others have) works. I'm not being rude- just trying to save you a stack of time!

Ultimately of course if you want to push for more power then the little mac is not the right choice- a bigger dd is the go for that.

Kiss is nescessary for people with limited time or patience or a perfectly infallible idea that the average person can do (maybe with a how-to with pics for people not so good at envisaging things from text). I have lots of both after being laid off work forever so have time to experiment. Plus I like to do what no one else seems to have to see how it works. Im not saying the simple idea is bad but I seriously dont want loads of oil sat in a hub ready to flow out like I have seen most do at some point because I didnt seal something quite right. While 3 out of 4 people are displaying pics of oil all over the brake and tyres I cant do this. Once I see an article that clearly shows the process that has been proven several times I would be happy to give it a go. So if I need any cooling when I get my motor I want to try minimal pooling of oil in the body and most of it contained in the pipes outside the hub. There it can be cooled and pumped back to where its needed.

In the uk you can get into trouble for having big direct motors but there seems to be a loophole. Although the bike cannot be powered over around 200-250w on the road, I have read articles suggesting that they could not be prosecuted if it was not powered on at the time and didnt surpass weight limits.

So I f you are pedaling a moderately sized hub hiding behind a 225mm disc like mine and are pulled doing a speed thats roughly possible under human power its much harder to prove it was active at the time due to the free wheel. Something I couldnt do with my conhis due to the drag.

Right now people always home in on the big black thing in the wheel and had a copper hang out of his landrover to check it as he passed me but he never stopped. Obviously suggesting a band of maybe 4 pipes on the outer extremities of the spokes might be an eye catcher but again, I can legally have this installed and it is up to people of authority to prove it was active at the time. Yes officer heres the battery now watch me do 25mph with my legs.

I dont want to break the law or speed limits I just want to flatten out my 18% gradient hills like it wasnt there if possible. I ordered a 36v 10t motor with 40a max controller that I will likely set to 25a while it is standard, depending on the heat observed.

Have you heard of sleeper cars, like a honda civic 1.6 standard alloys etc but its a 3.2v6 turbo engine. I want a fairly light hub for very short mental blasts when needed and a normal feeling bike in between. DD was cheap when I needed it to be but money isnt an issue now so its time to find exactly what I want from my particular setup.

I had wanted one of these motors sensored up and very nearly pulled the trigger but then found out about the mac motors. Maybe next time http://www.hobbyking.com/hobbyking/store/__14427__Turnigy_CA120_70_Brushless_Outrunner_100cc_eq_.html

 

[ebikedelight]

Here is my preliminary custom "heatsink" for the hub motor:

It's held together by some speaker wire threaded through the holes I drilled out in each of the 50 pieces I cut from an aluminum channel. It was a lot of work, 2 hours straight, but I think will be worth it.

I don't expect a very good conduction of heat with just the bare metal touching, so I ordered some Arctic Alumina Thermal Adhesive. I will still keep the wire to prevent any chance of these heat sinks from flying off.

Has anyone ever done something like this? Am I the first?

Was this modification effective ? I like the simplicity of it....I am wondering if it would have gotten better cooling if the aluminum fins were cut to different lengths

 

[ebikedelight]

I really like the idea of the aluminum fins attached with thermal paste/ glue that Veloman has done. Its simple , not messy and would have to help dissipate heat.

Im wondering if also attaching aluminum fins to the left and right side of the hubs , near the spoke holes, where the magnets/ coils are, would provide additional heat dissipation . I also wonder if cutting each aluminum fin , to a certain style , would draw in more air or if cutting them all the same length and style , like Veloman has done, is the best method.

I would imagine that it would be best to take acetone and completely strip the pain away from the area of the hub where the aluminum fins get fastened so there isnt a layer of pain getting in the way of the heat transfer to the fins.

 

[veloman]

I didn't glue the heatsinks to my Mac yet. I tried it on an Evt scooter hub (much bigger). The thermal adhesive works great and I've yet to lose a heatsink.

I say, give it a shot. Probably won't help nearly as much as venting, but should help some. Double that surface area!

 

[ebikedelight]

I didn't glue the heatsinks to my Mac yet. I tried it on an Evt scooter hub (much bigger). The thermal adhesive works great and I've yet to lose a heatsink.

I say, give it a shot. Probably won't help nearly as much as venting, but should help some. Double that surface area!

I already ordered the thermal adhesive....and when it arrives, I am gonna do your modification. I like your idea because its not messy using oil, doesnt require drilling holes in the hub that can allow dirt/ water to get in , and your mod looks kinda cool. I am confident that it would have to help keep the hub motor cooler...just not sure by how much nor am I sure if cutting all the aluminum fins the exact same length provides the best cooling results

Im thinking of trying your mod...but instead of having all the fins with the same length vertical sides , make them so each fin on the back of each piece is 1" taller then its front fin...that way when the wheel is spinning , it may result in more air circulating around the hub/ fin grouping.

I also may place some aluminum fins on the left and right outside portion of the hub , where the magnets and coils are near the outer edges . I may cut them to be like a sideways V shape ,,like this :

< < <<<<<<<<<<<<<

and have them go circular around the outer edges of the hub,,,,maybe offset them, for better air circulation ? like this ?

< > < > < > < > < >
1- 2 -3-4 -5 - 6-7-8-9-10

maybe do that pattern and for every even numbered fin { 2-4-6-8-..etc } have it glued about 1/2" higher on the hub , then the fin in front of it , so its V opening can draw in more air.