Low power quiet motor design

[veloman]

Small geared hub motors are very quiet, by using non-metalic gear reduction. Why can't a motor such as the my1018z have such quiet gears? The output torque is even lower since the power is similar with a higher rpm.

It seems quite difficult to mount a hub motor as a mid-drive, but it's easily with the my1018z types. The noise just ruins those motors, otherwise they'd be great.

 

[amberwolf]

You could replace one of the gears with nylon or other plastic gears if you like. It is even possible to do it by hand, if you clamp together the original gear (removed from the assembly) to the piece of plastic you are going to cut into the new gear, and then file the plastic to the same shape. Be a PITA, but it can be done.

I don't know which gear would be better as plastic, the larger or smaller.

 

[neptronix]

Brushed, with metal gears, driving a chain. Perfect recipe for a noisy motor!

You may wanna consider running a small geared motor as a mid drive. If you can cut the RPM by 1/3rd to the cranks, it would work quite well.

I've thought about doing this myself.

 

[veloman]

I may do that. 250rpm/3 = 80rpm at cranks. 45/15 reduction = 3.

They key will be mounting the hub securely and dealing with the wide axle between your legs

edit: I probably won't do this. I"m hoping that 48v will be a lot more fun on the little geared motor (cautiously fun.... not pegging it up super steep hills with no assist).

 

[Rassy]

This discussion touches close to my current mid-drive setup. At 48V the ratio between the crank and the motor is 3.5:1. The slow wind 9C 6X10 is quiet, the loudest part being the eno freewheel. At slow speeds I have to be using the motor to be stealthy. At speeds over 10 MPH the road noise is greater than the eno. I read somewhere that the new 9C's are even quieter.

Anyway, with so many motors out there, isn't there a non-hub motor that shares the good characteristics of the 6X10 but has less weight and a smaller diameter, along with a more conventional mounting design than a hub motor? I could have (almost did) reduced the diameter by an inch be shaving off the spoke flanges, but not much weight would be involved. No reason in my mind the motor couldn't be an in-runner, which if I understand correctly in simple terms would mean the shaft spins instead of the can.

 

[amberwolf]

Brushed powerchair motors are usually lighter and smaller and easier to mount than the hubs, but the right-angle gearboxes on them weigh as much (or more) as the the motors themselves, making them then weigh more than the typical 9C-type hub.

STill, easier to mount as a BB drive on a typical bike. Reasonably quiet, though not as quiet as a DD hub, nor as efficient, power-wise.


Lots of brushed motor options that will work easily enough for this type of thing, but many of the powerful brushless ones that are lighter also get that way by being really high RPM, and that requries a separate reduction system to get it down to crank speeds. More weight, complexity, etc.

That's the problem with small motors. Either they are lower RPM and also lower power, or they are higher RPM and need reductions that weigh more than they do to hook change that speed into torque.

 

[veloman]

Yes, this is true, but that my1018z motor has the power I want, acceptable weight, it just uses metal gears. Since geared hub motors use nylon gears and experience more torque - I think such gearing reduction could be acheived with that above motor and vastly less noise.

Perhaps the manufacturer didn't care about noise, only durability, and therefore went with metal gears.


I think there is a market for such a motor. But then again, not many consumers want to build custom ebikes with mid-drives like us.....lol. The tried and true geared hub motor works pretty well though. Will see how it goes on 48v.

 

[Miles]

Since geared hub motors use nylon gears and experience more torque - I think such gearing reduction could be acheived with that above motor and vastly less noise.

Bear in mind that torque in the geared hub motors is split between the three or four planet gears. The MY1018z only has a single torque path....

 

[TylerDurden]

Electric chainsaws regularly have a large plastic straight cut gear. Metal motor shaft & metal gear drives big plastic gear. You gotta abuse the saw to trash the plastic one. (Letting dirt remain inside is not so good.) Mine has been well used since '99.

The little MY1018s are nice, but damn those straight gears. Helical gears would have been a home-run: sturdy and quiet.

 

[dumbass]

Electric chainsaws regularly have a large plastic straight cut gear. Metal motor shaft & metal gear drives big plastic gear. You gotta abuse the saw to trash the plastic one. (Letting dirt remain inside is not so good.) Mine has been well used since '99.

The little MY1018s are nice, but damn those straight gears. Helical gears would have been a home-run: sturdy and quiet.

I posted on this before. You are correct Currie's gearbox uses 2 metal gears. I think the small gear is actually machined onto the armature shaft so if you were to change one to plastic it would have to be the big one. You are also correct that they are helical but I don't know that I would call the a straight cut gear ether. I normally consider a straight cut gear as being cut at a 90 degree to the shaft whereas, these are cut at a 45 degree angle. But as I said they are not helical.

I totally agree a plastic gear would likely solve the noise problem. But I think it would be near imposible to do without actually machining it. But is it really the gears making the noise? IF you remove the gearbox cover and run the motor the gears are very quiet. But as soon as you reinstall the cover there's the noise again. I have tried everything short of charging the gears to quiet these motors. While I have had some success the efford was not worth the results. Maybe one day I will try machining a plastic gear and see if it works. I could make a small fortune selling these gears for 5 bucks to all the Currie motor owners. Bob

 

[veloman]

I posted on this before. You are correct Currie's gearbox uses 2 metal gears. I think the small gear is actually machined onto the armature shaft so if you were to change one to plastic it would have to be the big one. You are also correct that they are helical but I don't know that I would call the a straight cut gear ether. I normally consider a straight cut gear as being cut at a 90 degree to the shaft whereas, these are cut at a 45 degree angle. But as I said they are not helical.

I totally agree a plastic gear would likely solve the noise problem. But I think it would be near imposible to do without actually machining it. But is it really the gears making the noise? IF you remove the gearbox cover and run the motor the gears are very quiet. But as soon as you reinstall the cover there's the noise again. I have tried everything short of charging the gears to quiet these motors. While I have had some success the efford was not worth the results. Maybe one day I will try machining a plastic gear and see if it works. I could make a small fortune selling these gears for 5 bucks to all the Currie motor owners. Bob

Please do! My mid-drive setup with this 450w motor was hauling me around at 25-30mph with moderate pedaling, and climbed any hill incredibly well. If I do this setup on a road bike with a 5lb lipo battery, put on my roadie gear... I'll be averaging over 30mph with insane efficiency and handling.

I might just do such a build and deal with the noise. It was a BLAST to ride that setup in bike gear on a 32lb mtn bike with a 14lb battery..... imagine it on a 20lb road bike with a 5lb battery

 

[dumbass]

Yeah, I don't think people give these little cheapy motors enough credit. They are good motors but the noise can be a killer. If I had a good quality indexing deviding head for my mill I would give a try at making a few different plastic gears for it. But the cost of the indexing turntable and cutters are just not worth it. It's a shame someone with the right equipment doesn't give it a shot though. Bob

 

[Miles]

Plastic gears aren't difficult to source. Not sure how long they'll last, though...... What pitch are they?

 

[liveforphysics]

If you want low power and quiet, do yourself a favor and just get a 9C.

They work.
It's cheap.
It's reliable.
It's simple.
It's heavy, but not that bad.
It's rugged.

 

[vanilla ice]

IIRC the shafts are pretty loose on these motors. It uses weak little spring washers to take up the gap between the shaft/bearing/aluminum case. Got to wonder if changing out the spring washers to something else would quiet them.

 

[veloman]

LFP - with the type of ebikes I'm mostly interested in, a 9c is much too heavy. You can't put that on a road bike, and even if you could, it would be nothing like the amazing handling and efficiency of a road bike.


I'm coming from a different perspective as most of you. If you haven't raced road bikes and felt how fast they are with even low power, and how fun they are due to their lightweight, then you won't understand why I'm so interested in adding 300-400watts to a road bike.


I want to keep my ebike as close as possible to a normal bike, just with some extra power.

Even if I could add only 100watts to my cranks on my road bike, I'd go from easy endurance pace (18mph) to near time trial pace (23mph). When cycling, the difference of 100watts applied in a efficient minimal design, is a big step.

 

[dumbass]

IIRC the shafts are pretty loose on these motors. It uses weak little spring washers to take up the gap between the shaft/bearing/aluminum case. Got to wonder if changing out the spring washers to something else would quiet them.

Ice, You would not believe how many mod attempts I have made to quite these gearboxes. I have installed higher quality bearings and added plastic spacers and plastic washers to remove vibrations and movement in the main gear. I even machined a new plastic cover because I thought the bearing to bearing was not aligned properly. Of couse no matter what you do you are always stuck with the base casting. Bottom line I do not believe the noise is actually the gears clashing together. But more a vibration caused by poor alignment of the bearings. I actually had one motor that was very quite running........until I took it off it's mounting plate and remounted it again. Then it because my loadest motor or the 4.

But while I'm not convinced the problem is actually gear noise I do feel a plastic gear would reduce the problem because plastic would not trasmit noise and even if it were to be misaligned it would still be quite running.

Bob

 

[dumbass]

If you want low power and quiet, do yourself a favor and just get a 9C.

They work.

Yes, I'm sure your correct but some of us prefer to drive through our bikes gearing.

Bob

 

[wineboyrider]

I like the loud whining sound. It makes me sound like I'm riding fast. But, I haven't rode my ezip in a while.

 

[amberwolf]

If you want low power and quiet, do yourself a favor and just get a 9C.

Yes, I'm sure your correct but some of us prefer to drive through our bikes gearing.

Or do like I am going to on the new bike, which is to drive a 9C thru the gearing. :lol:

 

[dumbass]

If you want low power and quiet, do yourself a favor and just get a 9C.

Yes, I'm sure your correct but some of us prefer to drive through our bikes gearing.

Or do like I am going to on the new bike, which is to drive a 9C thru the gearing. :lol:

No argument there. I am in process of setting up a BMC motor to replace my twin Currie motors. I'm planning to use timing pullies for gear reduction. I have the motor and the controller is in shipment. Here's the motor I'm going to use except I didn't buy it from this suppler.

Bob

http://www.thesuperkids.com/15wabmcbr24m.html