Which is quieter, MAC or BMC?

[neithermovingnorstill]

Hi,
I wonder if anyone has experience with both MAC and BMC motors who could give me an idea of which is noisier?

I have watched vids on youtube but it's hard to tell with all the wind noise and different cameras, and I searched google/forums, but it's not something that has come up to my knowledge.

Thanks

 

[neptronix]

Same gear size and shape, same outer planetary ring size, stator is virtually identical if not 100% identical..

If there is a difference, it is not going to be easily noticeable.

 

[spinningmagnets]

"Geared hub motors: BMC vs MAC Shanghai" 3-page breakdown with pics of the guts....
http://endless-sphere.com/forums/viewtopic.php?f=4&t=22103

edit: a post from Aug 9, 2012 http://endless-sphere.com/forums/viewtopic.php?f=6&t=42509#p621514

I'm running a MAC gear cluster in my front BMC and it's noisier and the clutch seizes while the BMC v4 'blue gear' cluster on the rear wheel just keeps on running perfectly. I think I'm going to pull the MAC cluster and go with a BMC

 

[neptronix]

Caution: that thread is rather ancient. Both motors have had improvements since then, particularly in the clutch and gear sections.

 

[cal3thousand]

Newer gear materials are quieter too

 

[neithermovingnorstill]

Thanks.
Yeah, I'm aware that they are pretty close, maybe there's no noticable difference.
I still might go with a DD, but there are the obvious drawbacks. (climbing, weight, coasting drag)
I think it might be possible to use a cooling system with a geared motor, and then insulate it with a sound barrier material, but that is entering uncharted territory. Which doesn't scare me, but I can just picture working on it for months and months.

 

[Kin]

I think it might be possible to use a cooling system with a geared motor, and then insulate it with a sound barrier material, but that is entering uncharted territory. Which doesn't scare me, but I can just picture working on it for months and months.

The nature of sound isolating materials is that they're either
A) heavy materials, with moderately insulating properties.
In which case, you have added a lot of rotational inertia to your wheel, and a bit of thermal insulation.

Or,

B) Foam-type materials, typically functional only for high pitch stuff (or maybe it's low pitch? But my intuition says high pitch).
In which case, you have added a lot of thermal insulation.

Unless you had a liquid based cooling system that went in and then out of the sound barrier situation, you would have cooling issues. This might not be an issue if you're only running at 500 watts, but if you're pushing the higher wattage, it's no good.



I am very curious whether or not active noise canceling would be possible. I don't understand sound engineering. It's super cool, but totally out of my ballpark. I don't know if it would be effective in the open-environment, but I have seen the kind of press releases for some open environment noise canceling techniques. But that might not be on the hobbyist level. I know noise canceling is totally possible on the DIY level for headphones, though.

It's also worth talking to the few people who have filled their hubbies with oil. I would imagine liquid would damper the vibrational sounds, which I guess are mostly coming from the gears. You might find noise reduction if you have a very heavily filled oil cooling setup. You will loose some efficiency when you load a lot of oil, though. But I would think it's not that big of a deal with a light oil.

 

[999zip999]

I got a mac clutch for my bmc600 hs and had to clean up the plastic hair before install.

 

[neithermovingnorstill]

Kin, thanks, it's almost entirely high pitched sound that I am concerned with, the gear grinding noise doesn't bother me, so the light weight/foam route should work for the noise.
As for the cooling, that's where it gets complicated. I'm going to put a pin in sound insulation for now.

I did already post on the oil-cooled thread re dampening the sound with oil/coolant, we'll see what people say their experiences have been.
I would expect it to help a bit too. I'm willing to take an efficiency hit for the sound improvement, part of the thrill of the ride is being less polluting than a gas bike; it's not so fun if I'm making noise pollution as well.

 

[Lebowski]

Kin, thanks, it's almost entirely high pitched sound that I am concerned with, the gear grinding noise doesn't bother me, so the light weight/foam route should work for the noise.
As for the cooling, that's where it gets complicated. I'm going to put a pin in sound insulation for now.

I did already post on the oil-cooled thread re dampening the sound with oil/coolant, we'll see what people say their experiences have been.
I would expect it to help a bit too. I'm willing to take an efficiency hit for the sound improvement, part of the thrill of the ride is being less polluting than a gas bike; it's not so fun if I'm making noise pollution as well.

The typical high pitched sound of an electric motor is caused by the controller. A simple china controller
will make the high pitched noise, a good vector controlled one with sine-wave output will be quiet.

 

[neptronix]

It's really not all that loud.
People have noticed my DD motors more often than they've noticed my MAC motor.

The only method of sound dampening that would not hurt it's ability to shed heat ( which geared motors are already disadvantaged at ) is to do something like an oil fill.

 

[neptronix]

The typical high pitched sound of an electric motor is caused by the controller. A simple china controller
will make the high pitched noise, a good vector controlled one with sine-wave output will be quiet.

Well, sure, but such controllers you speak of are rather expensive in comparison, and are typically designed for high power ( motorcycle, car ) applications.. am i right?

 

[neithermovingnorstill]

A sine controller would be awesome, but are there any sine wave controllers that don't cost an arm and a leg?
They seem to be in the $500 range. Worth it if I had the dough no question.

 

[Lebowski]

A sine controller would be awesome, but are there any sine wave controllers that don't cost an arm and a leg?
They seem to be in the $500 range. Worth it if I had the dough no question.

The one I built is sine wave This is also why I know sine controllers are very quiet
Mine has the possibility to kind of 'oversteer', when this happens the sine waves are so large they
don't fit in the supply anymore and the top of the sines become flat. At this point I can hear
the high pitched noise starting...

Cost to build one yourself would be around $150 for 4115's to $200 for 4568's I guess (pcb, controller IC,
parts from digikey). Such a setup would run beautifully on 20 to 30 s (80 to 120V) and be capable
of 1 to 5 kW dependent on your cooling system building skills.

 

[Ben Wilson]

The only noise I hear from my MAC is the gears. As I ride a recumbent trike my ears close to the motor, but it doesn't sound particularly loud to me.

 

[Kin]

I can't wait until Lebowski start's kitting the pcb and processor .

I didn't realize that the frequency of switching in the controller causes the whine in the motor....Gosh, that explains why after all the talk of china controller switching causing noise, I've never heard noise emanating from the controller box >.<. I'm a fool.


I just want to add that I think foam will not work very well. I've been very discouraged from any sound isolation I've ever tried besides that which is simply damping a vibrating part. Damping a vibrating part is effective, but "wall" type sound filtering needs bulk and mass and a cleverness I don't have or most devices don't have. Maybe you can get enough isolation to satisfy you, though. I would think it install a temp sensor in your motor if you do go that route. And to read up on sound proofing.

 

[neithermovingnorstill]

Kin, thanks, I am shelving the insulation plan for now since active cooling is a bit complicated for me right now. Maybe later though. Triangular troughed foam panels can break soundwaves, but you need a 100% membrane, no gaps, like a true seal.

Ben Wilson, that's good to hear. I did listen to a couple videos, and to me a whine is audible from the macs.
Perhaps cameras isolated high frequency more than the ear. (quite possible) And when riding, your ears are facing away from the motor. It might bother folks behind you more.

Lebowski, thanks for that, I'm not sure how hard it is, but I do have some helpful local electronics wizards who could probably assist/oversee my efforts if I go that route. It's great that it's possible to get one for so much less! Since the whine is my main concern, I may be wise to put the effort into making one.

 

[Phoebus]

Never seen a MAC in use nor MAC gears in my BMC, but I can say that the BMC motors which I use are quite quiet indeed.

 

[docnjoj]

A few years ago Tyler Durden and I independently but collaboratively made large efforts to quiet the wonderful (but very noisy) MY18Z brushed geared E-zip type motors. I used aviation sound deadening and a box and he used molten lead poured into gear recesses. We also used various programs including Audiocity to get mp3 sound stuff but we were not successful at really making meaningful changes on the sound level the straight cut metal gears made. Bummer but The E-zip folks according to Darkangel went to helical gears in 2009 and apparently that made a huge reduction in the noise level.

Really the engineering for noise reduction needs to start on the front end with gearbox design. My experience with retrofit attempts really didn't help even with a fair bit of work. I'm just sayin' that if the factory folks cared about noise attenuation they will have designed it into the motor/gearbox. If not, then good luck trying to make a noisy motor quiet. Ain't gunna happen easily or cheaply. Gear material makes a huge difference but quiet gears need either softer materials (prone to mush) and helical gears may be helpful but these are not in a MAC or BMC. Those are straight cut. The redesigned MY18z has a "C" or a triangle on the cover.
otherDoc

edit: I just saw the articles about oil cooling and running quieter but we had already vented ours. Tyler's really looked good! Mine looked like beavers chewed the holes but we couldn't try oil. That might be the way on these steel and hard composite gears. ATF maybe? Hey ddk! Is your geared motor noisy?