Cooling a Mac hub motor

[veloman]

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.

[cwah]

This analog voltmeter is the smallest I've found to fit this requirement:

http://www.ebay.co.uk/itm/YS-50-DC-0-2V ... 1290wt_789

Not the smallest but quite small and lightweight (57g), and should be way smaller than a multimeter.

[veloman]

It looks about 1/3 the size of my voltmeter.

I did a distance test just now, since I'm worried there is a problem with my battery. After 13 miles in 96 F deg heat, the motor temps hit 94 deg C. This is at 21wh/mile. This is ridiculous IMO. There is just no cooling happening, unless I go downhill at <200watts and over 25mph. It just saturates and saturates.

Looks like I need to ride a 9c when it's above 85 and I need to do more than 7 miles at any reasonable speed. Not that I am having motor issues, the power still feels fine. But at 94, things are getting very close to the danger zone IMO. Not all of us ride in 70 degree temps and have few stops to heat the motor. Riding in rush hour traffic, you can't baby it, and there's a lot of stop and go.

[cwah]

I'm surprised your mac motor get so hot so easily. Do you have the right calibration from your cycle analyst?

My little direct drive hub (24V 250W of 4.6kg) handle 2500W peak and 600W continuous without breaking a sweat. The motor is barely warm after 20-30 mn ride.

Have you tried to touch the motor to feel the temp?

[veloman]

What is your ambient temperature?


I don't have a CA hooked up. There is a temp sensor installed as described a few posts above.

It doesn't get hot right away, but it just keeps going up without cooling off. I was only running 1250w peak today too.

I do touch the motor and it feels hot when it's in the 70,80,90 deg range. Not hot enough to burn me, but hot.

[cwah]

I live in london, so the local temperature is quite low. Around 15-25C most of the time. And very often raining

Just wondering if one of the sensor doesn't read correctly, either in term of power usage or if the temp meter is wrong.

[veloman]

I live in london, so the local temperature is quite low. Around 15-25C most of the time. And very often raining

Just wondering if one of the sensor doesn't read correctly, either in term of power usage or if the temp meter is wrong.

Well it sounds like it's a matter of ambient temperature. I didn't have such high temps when it was below 80 F here.

I'm certain my power usage is correct, it matches my controller settings and my performance calculations on hills.

[John in CR]

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.

[cwah]

My mac motor 8T at 74V is really noisy with strident noise. Not very agreable. Is it normal? I have a very nice sound with my DD motor, but on the mac it seems different.

[veloman]

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?

[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 (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

[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