Quiet conversion kit using RC motors?

S

spike

100 W
Joined
Dec 3, 2007
Messages
102
Location
Australia
I'm looking for a quiet, lightweight, high torque kit for my next attempt at building a commuter bike. I've tried an X5, Currie (48v), Cyclone 500w, Tongxin, and Bafang. Apart from the X5, which was too heavy, and the Tongxin which was too weak, all the others are too noisy for me. I know we all have different tolerances to noise and some will be surprised that the Bafang is too noisy, but my Bafang is noisier than the modified Currie kit.

My next build will probably be a Nine Continents kit from ebikes.ca, but I also found this site for petrol bikes http://www.bikeengines.com/orderpage.htm and thought about doing the conversion using parts from that kit with an RC motor instead of a petrol motor. A belt drive without a gear box should be very quiet, but would it work? Would the speed reduction be sufficient? The motor gear has 11 teeth and the drive ring has 148 teeth. Would the motor and batteries survive without a gear box? As you can tell from the question I'm a bodger not an engineer so don't be too hard on me please :)

All the best

Spike
 
Yes, it would work but, even with an overunning clutch on the drive pulley, you would still have some drag when not running the motor. RC motors vary a lot in the sound they make but, with block commutation there's always some high pitched noise.
 
RC motors are amazingly quiet, compared to the old brushed motors.

But I can hear even my smallest one at 1000 feet, and thats with direct drive to a prop. Add in gearing or pullys and the noise will increase.

the quietest design is low rpm and direct drive, with the fewest moving parts possable. I.E., your X5, or a 40X.

You might get closer to this noise level if you incase the RC motor and the belt system in some kind of sound dampening case
 
I have the golden eagle drivetrain on my current project and it seems to work ok. I needed to add a tensioner to mine for two reasons, one the pulley didn't/wouldn't sit perfectly centered on the spokes and two I believe by adding the tensioner it increased tooth contact allowing for more torque before slipping. I haven't put a whole lot of mileage on my system due to frying the motor, but when I was riding the belt drive was pretty quiet and efficient. Really the hardest part of the system is to make sure the belt lines up perfectly otherwise the pulley on your motor will eat away at the sides of the belt.
 

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Oh, and btw the drive pulley is interesting as the website states that it has 144 teeth or something like that. What they fail to say is that the pulley is only covered halfway with teeth. The actual reduction with a 12 tooth drive pulley is more like 20:1. It ran quite well up around 35 mph with a 380kv outrunner on 26 Volts.
 
Jason,

A huge pulley like that typically uses every other tooth. That makes the pulley easier to manufacture and creates less drag. The overall ratio is calculated by dividing the diameter of the large pulley by the diameter of the smaller pulley.

Matt
 
Yeah it's certainly possible, when I poured my first pulley I had some trouble pulling it from the mold... Infact the mold was pretty well ruined by the time I got it out. This is a picture of the pulley. I poured it using epoxy with some glass fill.
 

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Ty,

It was an interesting endeavor, and it turned out a little oblong which is why I tried the golden eagle to find that it also didnt center well on my wheel. I've been talking a lot to a guy at work lately who works in our moulding department. He's amazing making full molds of actual helicopters and many of the parts inside of them for our simulators. He's shown me some of the products he's working with and soon I may make another attempt at building a pulley. This time I'd like to try a different plastic with some carbon chop for extra rigidity made to run with the 10mm polychain belts.

Btw,
I love your bike Miles very clean setup :D
 
Using a rubber mold would even allow you to be able to do a double flange without having issues pulling it out. I actually made my first mold out of MDF which I basically cut out and then affixed a belt on the inside of the outer ring to give me the teeth in the pulley. I had to cut it in half to get it out. The one problem with doing it is that the teeth come out very tight on the belt and to get the belt to settle into the teeth without incredible tension I had to go over the whole thing with a dremel and shave a little bit off of each tooth to allow the belt to fall into place. I hope this time to draw out the next one and have someone cnc it. After that I can drop the original in the liquid rubber mold and make as many as I would want.
 
Jason said:
Using a rubber mold would even allow you to be able to do a double flange without having issues pulling it out. I actually made my first mold out of MDF which I basically cut out and then affixed a belt on the inside of the outer ring to give me the teeth in the pulley. I had to cut it in half to get it out. The one problem with doing it is that the teeth come out very tight on the belt and to get the belt to settle into the teeth without incredible tension I had to go over the whole thing with a dremel and shave a little bit off of each tooth to allow the belt to fall into place.
Click to expand...

With so many teeth engaged, you only need an approximate profile, it has to be loose rather than tight, though... maybe build up a reasonable layer of spray paint on the teeth, and then a release agent, for another DIY attempt? :mrgreen:

I've been playing around with pulley designs today. Was thinking about designing one with variable offset via the spokes but I decided it would just be too much grief... What might be good is a pulley with a metal hub enclosing an overunning clutch and with flat spokes radiating to a moulded plastic pulley ring. It would be pretty straightforward to fit it to something like the GruBee rear hub, for example....
 
Thanks for the replies everybody. If Miles' bike was available from the LBS I would just go and buy one :mrgreen: As it is, I know my limitations and that kind of build is way beyond me :oops: . I think from what everyone has said that the noise from the RC motors rules them out for me. I might try something like Jason or Greggs design with a Hi-Koll instead though. They are very quiet without the planetary gear attachment. I just need to find a D-shaft belt drive for it and think about the motor/belt drag that Miles mentioned. I'll have a snoop around the scooter parts to see what I can find. Thanks again.
 
recumpence said:
RC motors are generaly pretty quiet. But, they are not silent. Many hub motors are quieter.

Matt
Click to expand...

CNCAddict said:
...the motor should work at any PWM you give it, and should produce a really clean BEMF signal unlike some of the other motors out there, so if you don't like the squealing just crank it up to 24khz.
Click to expand...

How quiet will Davids motor be with the PMW cranked up above the audible range?
 
Hard to say.

I can tell you that the sound my motor makes is not obtrusive in any way. Heck, I love the way it sounds!

It is not 100% stealth, though, unless it is silent. :wink:

Matt
 
Miles said:
Gregg (erth64net) has this set-up - maybe he'll comment :wink:
http://gregg.berkholtz.net/wiki/doku.php?id=recchetta
Click to expand...

Well, first I have to know you're talking about me :) Thanks for the plug Miles!

The setup continues to run great, and my wiki page (which you linked to) is where I've been putting any details that I can think of - though I can't possibly think of everything... :mrgreen:
 
Jason said:
Oh, and btw the drive pulley is interesting as the website states that it has 144 teeth or something like that. What they fail to say is that the pulley is only covered halfway with teeth. The actual reduction with a 12 tooth drive pulley is more like 20:1. It ran quite well up around 35 mph with a 380kv outrunner on 26 Volts.
Click to expand...

Well, the wheel pulley is not covered halfway, but more about 1/4-1/3 of the way on opposing sides...that way the belt always has a strong grip under a relatively-high torque load.
 
recumpence said:
Hard to say.

I can tell you that the sound my motor makes is not obtrusive in any way. Heck, I love the way it sounds!

It is not 100% stealth, though, unless it is silent. :wink:

Matt
Click to expand...

Define silent, on a bike, at 30MPH...seriously :)

At least for me, once I'm up to that speed, wind noise overwhelms the motor's whine.
 
Drunkskunk said:
RC motors are amazingly quiet, compared to the old brushed motors.

But I can hear even my smallest one at 1000 feet, and thats with direct drive to a prop. Add in gearing or pullys and the noise will increase.

the quietest design is low rpm and direct drive, with the fewest moving parts possable. I.E., your X5, or a 40X.

You might get closer to this noise level if you incase the RC motor and the belt system in some kind of sound dampening case
Click to expand...

You might have something here; two things:


  • 1) With the prop spinning, how much of that noise is the motor, and how much is the wind/prop?
    2) Acoustic waveguide...specifically, something which redirects and dampens the motor's whine, without blocking airflow. I wonder if a thing would be both viable, and even worth bothering with vs simply assembling an efficient outrunner able to run at slower RPMs.
 
erth64net said:
recumpence said:
Hard to say.

I can tell you that the sound my motor makes is not obtrusive in any way. Heck, I love the way it sounds!

It is not 100% stealth, though, unless it is silent. :wink:

Matt
Click to expand...

Define silent, on a bike, at 30MPH...seriously :)

At least for me, once I'm up to that speed, wind noise overwhelms the motor's whine.
Click to expand...

For me it isn't the noise that I can hear that is the issue. It is the noise that the pedestrians can hear that concerns me.
One aspect is the fact that useful ebikes are illegal in Australia. So my 48V 1KW bike could get me into some bother with the police. Another is that I find it attracts some nasty comments if you whiz past pedestrians on some thing that sounds like a "swarm of angry wasps". Don't remember who said that, but it describes the Cyclone motor perfectly. I'm also a sensitive soul and take the comments to heart when I shouldn't really give a sh***. :roll:
 
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