cyclone with nylon gears

[dustyearlobe]

just thought i would throw this out there ,just made some nylon gears for the planetary box just about 3x louder)
if any one has any idears as it works ,but was kind of thinking it would reduce noise .
mind you i have only tryed it under load with the brake on

 

[IdleMind]

I would also expect nylon to be quieter. How did you make the gears, was the nylon neat or glass reinforced. Plastic gear teeth will deflect under load so even when they roll together smoothly when you turn them by hand, they can behave like cogs when running under load. Often the tooth tips are slightly reduced to allow extra clearance as they come into engagement.

 

[dustyearlobe]

i used gear cutter and indexing whell to get the spacing ,felt nice and smooth when it wasnt conected to the motor .
The nylon wasnt mixed with glass or any thing .
im going to try and build a gear box with reductions (chains and sprockets)see how this go,s ,realy love my bike but the noise at WOT graits after a while.
I think im right in saying its about 8/1 reduction

 

[Miles]

I think im right in saying its about 8/1 reduction

9.333333333333333333333333.........:1

Or 9 1/3 : 1 to be precise

 

[Byte]

I don't have bike experience with this, but I know RC cars with nylon gears are MUCH quieter than steel gears. So I think there is something wrong with the nylon gears?

 

[IdleMind]

I am impressed that you made your own gears. I believe if the original metal gears were made to closer tolerances they would be much quieter and even better if made from a strong reinforced plastic. I just don't think you can duplicate the exact gear specs and make them more accurately than the originals. Nice try and good luck.

 

[Knowledgethirst]

Another approach would be to use the steel gear to cast a polyurethane mold, then cast a hard polyurethane gear in the mold.
I've not used PU in this way but I have a very experienced contact who speaks very casually of this process.
I'm currently pressing him for a demo but he is too busy to expect this to happen soon.

 

[solar.g]

In car gearboxes straight cut gears are noisier than helical cut ones.
If you can make nylon gears, can you make helical gears, metal ones?
You'd have to make a new motor-shaft gear too, though.

 

[Miles]

You'd have to make a new motor-shaft gear too, though.

You'd have to make a completely new gearbox...............

 

[dustyearlobe]

yes i think the problem is the tolerances (i,ll stick some pics up soon )luckly iv got two motors so lots of face space with out the gear boxs to make a reduction box .
i have seen some gears and chain (6mm and 8mm pitch with 6mm centers)on ebay with various sizes ,should be able to get close to pedaling cadence also with this (two stage reduction to 14t freewheel)hardest part is going to be getting the gears to fit over the star drive like shafts on the motors with out any play,its a shame i didnt have a a spare dead motor ,i could then use the shaft as a broach to fine tune any first cutts(life can be so cruel).
i do like the idear of molding the gears ,not sure if any resins ect would be strong enough.
helicut gears are a little to involved for me right now ,maybe cyclon (or headline)will give this a try at some point ?
I dont suppose you know the reduction needed for a decently close to peddaling cadence Miles ,it would be a bit of guess work for me right now

 

[Miles]

I dont suppose you know the reduction needed for a decently close to peddaling cadence Miles ,it would be a bit of guess work for me right now

You don't know the motor speed?

 

[spinningmagnets]

I've always felt it was a "missed opportunity" that the MAC geared hub has straight-cut gears. They are clearly marketed as an upgrade in power and quality over the ubiquitous Bafang-BPM (millions of BPM's made as the default choice on generic China-made E-bikes). For a small increase in price, the MAC could have had helical gears.

When looking at the secondary reduction on the Bafang-BBS02, I at first assumed that the teeth were straight-cut, but a closer inspection shows they are helical, and even though the angle of the teeth is only very slight, it clearly has a significant effect on how quietly the system runs.

 

[dustyearlobe]

I dont suppose you know the reduction needed for a decently close to peddaling cadence Miles ,it would be a bit of guess work for me right now

You don't know the motor speed?

umm no ,lazyness on my part i would asume ,little reserch prob wouldnt go a miss but i have 2x 1200w cyclones running 12s and have no idea of the kv(some ideas need certain answers,i just havnt got round to asking the questions)

 

[Miles]

It's probably around 2500rpm, in which case you'd need a reduction of at least 25:1. So, 2 stages of 5:1.

 

[dustyearlobe]

pic of gears

 

[dustyearlobe]

wow 25/1 is a big jump from 9.3/1

 

[Miles]

wow 25/1 is a big jump from 9.3/1

What ratio did you have between the gearbox output and the cranks before?

 

[Gab]

Some things to consider, Efficiency of helical gear is less because helical gear trains have sliding contacts between the teeth which in turns produce axial thrust of gear shafts and generate more heat. So, more power loss and less efficiency. Its maybe 1-2% less efficient then strait cut gears per stage.

If you go helical in the same volume of gearbox you will not be able to get the same ratio, you will get a lower ratio, and since the ratio of 9.33 to 1 already is not high enough, you may have to add another stage,You can read below how much you will, lose 5% efficiency per stage if NON planetary gear design, or 3 % per stage if planetary design.

quote:
"A typical single-stage spur gearhead, for example, is about 90% efficient whereas a two-stage model is about 85% efficient. Most planetary gearheads are roughly 97% and 94% efficient for one and two-stage units, respectively. "
http://machinedesign.com/archive/spur-versus-planetary-gearheads-dc-servomotors

If each stage of spur gear head is 90% efficient for strait cut,then helical will be at most 89%.

So for example comparing to another popular mid drive the Bafang BBs02 has a 3 stage helical NON planetary reduction, each stage is 89% efficient STg 1 2 and 3,11% less per stage then the total efficiency multiplied = 33% total loses.

Now compare this to the cyclone 2 stage planetary, stage one is 97% 9.331 planetary strait cut and stage 2 is a chain reduction of 97% efficiency. so 3% *3% = 9% total efficiency loss. so that's a difference of over 24% !

That would explain why that kit is not as fast as it should be as their lots of losses in the gear reduction as they have sacrificed it for low noise, so you will lose a lot of speed and power if you go to a 3 stage helical compared to what you have now. Is it possible to enclose the gearbox in a noise proof enclosure ? this is often used in industrial machines to get max efficiency and lower noise.

 

[dustyearlobe]

wow 25/1 is a big jump from 9.3/1

What ratio did you have between the gearbox output and the cranks before?

standard 14t to 48t chainring

 

[Miles]

So, you had a ratio of 32:1 before. Right?

 

[dustyearlobe]

Yes ...i figured it out now ....the most i reduce to total is 37 / 1 given to room i have ,maybe a bit more if i used a larger chainring ,but dont want to do that.
11t/35t first reduction 11t/38t second reduction 14t/48t the third reduction giving total 37.52/1,but i have no idea what rpm this will give me at the chainring.
I think ive read that 75rpm is a good leg cadence at the chainring

 

[boostjuice]

I dont suppose you know the reduction needed for a decently close to peddaling cadence Miles ,it would be a bit of guess work for me right now

You don't know the motor speed?

umm no ,lazyness on my part i would asume ,little reserch prob wouldnt go a miss but i have 2x 1200w cyclones running 12s and have no idea of the kv(some ideas need certain answers,i just havnt got round to asking the questions)

These motors are ~150Kv. I find best compromise loaded rpm band to be ~50>80% of no load speed (based on balancing torque and efficiency). So for 12S lipo thats about a 3330>5330rpm powerband.

 

[dustyearlobe]

Just got in from work ,and havnt wound down yet ,but thanks for the info guys (possible gals ,who knows)i shall attack it when me heads got away from me aching body

 

[dustyearlobe]

http://youtu.be/YMkPUh0wDaostill dont know how to post direct video ,but heres a link to the three stage reduction i have made for the twin cyclon .
fyi it only lasted two miles before the second stage chain broke ,using d4 6mm pitch .to much tourqe in this stage ,could try a bigger chain but going to try belt brive ,if i can get the combo right its going to be super quiet ,the chain drive while it lasted was great ,no whinning gearboxs he he

 

[Gab]

Cool how did you make it 3 stage ? is it chain drive for each stage? Do you have any photos of the gearbox ?