Motor started to sound like it was full of a bag of rocks on the way home Friday. Turned off the motor and pedaled it home... Planetary gears shredded. Glad it's a $20 fix not a $400 fix lol.
Posted by Carbsv2@reddit | ebikes | View on Reddit | 66 comments
Exactly what the title says. 'bout halfway home motor started grinding hard. Turned off the motor and limped home. Incredibly pleased it's just the planetary gears and not a full motor replacement.
hurgahdurbah@reddit
Why are they made of plastic and not metal?
tk42111@reddit
So when they fail the motor stays fine
hurgahdurbah@reddit
So kinda like a physical fuse?
Hashtag_Labotomy@reddit
How you are thinking about it, yes. In reality it's kind of like a clutch, in the way that it's meant to wear down and only take so much abuse. A fuse blows when it's limits are reached. In a hub motor you already know it's limits, the amount of power in and out of the controller. So if everything is working as it should, a fuse should never pop. These will break regardless because they are intended to be the piece that takes the beating to prevent the motor from breaking the expensive metal components over time. A.manual transmission may have 5 clutch replacements before it breaks, but if an automatic transmission breaks the whole thing has to be replaced or torn down and fixed. The nylon gears are that part like a manual transmission has.
wlexxx2@reddit
bad solution!
Hidden-Sky@reddit
Well the other option is using a metal gear, which will still shred itself slowly while also shredding the non-replaceable gears around itself, and filling the space with abrasive metal shavings instead of self-lubricating nylon threads.
wlexxx2@reddit
why is the only option 'shredding' in a year or 2?
car transmissions have tons more power flowing, and last 200,000 miles
Hidden-Sky@reddit
Shredding is always inevitable when there is metal to metal contact. Particles are shed, these particles become obstructions, they dig their own little pits into the surface of the metal as they get caught between teeth.
I didn't give a 2 year timeframe as the lifetime limit for such motors, that was only an example of a timeframe in which I'd be really upset if the motor had to be replaced.
Car transmissions are made to be regularly maintained and use fluid which is replaced. They use large, heavily machined parts and helical gears, which evenly distribute load and reduce shock effect between teeth as they mesh.
Ebike motors use spur gears which lack such benefits, so they are more prone to wear. They're also much smaller and not as heavily built.
Typical RPMs for ebike motors are also higher than cars - the sun gear would be going about 3,000 to 5,000 RPM continuously, whereas a car's RPM would normally not exceed 3,500 RPM if you drive like a sane person.
It's the combination of these factors which reduce ebike motor lifespan.
Look man, I understand maybe you want to argue that the nylon gear is some kinda stupid scam to make us keep buying gears every now and then, but the fact is they're so cheap and easy to replace, and you only do it every few thousand miles. You will spend more on chains and oil and derailleurs and brakes than you will ever spend on nylon gears. And they're self-lubricating, which metal is not.
wlexxx2@reddit
great - my ebike broke and i am back to acoustic, which is going fine
Hidden-Sky@reddit
If reliability is what you're after, go for a Class 2 with hub motor rather than mid-drive.
Less strain on your chain.
If your motor fails, obviously you can still pedal home.
If your chain or derailleur or whatever breaks, you can still use the motor and throttle to get home.
wlexxx2@reddit
class 2 would be more power than class 1 though
don;t the mid drives have all metal gear boxes?
plus costing about twice as much per bike
Hidden-Sky@reddit
Class 1 and 2 have the same speed limit (20mph) but class 2 has the throttle.
Mid drives have metal gearboxes, but they also usually have a plastic motor reduction gear.
The gearbox gears are larger than the planetary gears, so they actually can be built tougher and they also spin at a lower RPM thanks to the motor reduction gear before them. Which, again, is plastic.
wlexxx2@reddit
would you say the mid drives use plastic as a 'mechanical fuse'?,
or some kind of self destructing but self-lubing purpose?
or is plastic just the cheapest thing that works?
Hidden-Sky@reddit
They all use them as a "mechanical fuse" - mid drives and hub drives alike.
That's one of the main purposes of plastic gears. Protect the expensive metal gears, while being cheap to replace.
stormdelta@reddit
To add on to that, if your goal is minimal maintenance, the alternative is direct drive hubs that don't use gearing at all.
The downside is they are larger, heavier, less efficient, and require more power for equivalent torque.
I use direct hubs specifically for having as little maintenance as possible and was okay with those to trade-offs.
Hidden-Sky@reddit
I am hesitant to go for a direct drive for those reasons, and also I hear they're difficult to pedal without motor power.
stormdelta@reddit
There's drag on the motor that wouldn't be there on a geared hub or mid-drive, that's true. It's offset somewhat on mine due to my controller supporting virtual freewheeling - it puts a trickle of power into the motor (like 8-20W variable on speed) to offset that slight drag.
wlexxx2@reddit
my point is actually - how much would it cost to make it last 25,000 miles?
the nylon just seems to be a way to keep initial price low, while not really saying what you are giving up, for saving the $30 or whatever
Hidden-Sky@reddit
You want it to last 25,000 miles without servicing, you mean?
A miracle, really. Nothing on a bike is made to last 25,000 miles without service, except the frame and maybe the rims and spokes.
If you wanna amend that to "make the motor last 25,000 parts without swapping any gears", then that means first using metal gears, then reopening the motor periodically to clean out the metal dust and replace lubricant probably every 1 to 2 years.
Then you ride the bike carefully and be sure not to accelerate as the rear wheel hits any hard bumps.
Now maybe it will last 25,000 miles.
You're still opening that motor back up every now and then, there's no getting around that. And you're buying lubricant fluid. Maybe you save like $30 in the long run, but your motor is still going to give out sooner than normal as oil cannot replace the shock-absorbing properties of nylon.
Do you really think that on a machine like an ebike - which is made of many bearings and cogs and chains and wires and batteries and a motor that already has one or more steel gears - manufacturers are somehow able to reduce pricing in any meaningful way by swapping one set of metal gears for nylon gears?
On bikes that can cost upwards of 2 grand?
Are you serious?
"We're going to use actual, well-made parts for most of the bike, but we'll just swap this one set of metal gears for nylon ones so we can bring the initial price down from $1,999 to $1,969!"
unseenmover@reddit
its referred to as "non interference" in that its designed to fail and not take the rest of the motor with it. Like a timing belt on a car..
rvralph803@reddit
They do make metal planetary replacements. However the nylon ones are designed to fail to protect the more important parts.
Extension-Version813@reddit
Mechanical fuses are probably one of the most important items on modern machines
Carbsv2@reddit (OP)
I've recently learned this! Makes alot of sense given how cheap the nylon ones are. Have nylon replacements on the way. Rather replace them biannually as regular maintenance than the sun or ring gear, or the motor itself.
Get_Fuckin_Dabbed_On@reddit
For what its worth I replaced my plastic gears with metal ones and haven't had any issues. Nylon softens when it gets warm, gets brittle when cold, and slightly weaker when exposed to water or humidity.
I get the theory that the nylon gears act like a mechanical fuse, but they always fail due to a defect or temperature. All the more important parts are metal anyway, and a regular hub motor wont produce enough torque to break anything if the wheel is restricted.
OhDavidMyNacho@reddit
Nylon also self lubricates
rvralph803@reddit
They say brass does too. I mean it is used in bushings.
wlexxx2@reddit
yes by consuming itself!
Hidden-Sky@reddit
As designed.
The other option is shredding itself and the less replaceable gears around itself slowly, and "self-lubricating" itself with abrasive metal shavings.
rvralph803@reddit
Eventually your sun gear won't be so sunny. 😕
Get_Fuckin_Dabbed_On@reddit
This was my old bike with a 3kw cyclone mid drive kit, put over 2000 miles on it and it was fine. Everything else on the bike broke eventually lol, normal bikes aren't made to handle 3kw of power, especially the drive system 😆
Hidden-Sky@reddit
2000 miles ain't a lot for bike lifetime. I'd be real upset if an irreplaceable ring gear wore out around then, forcing a motor replacement on an expensive bike.
Then again, Cyclone kits were cheap. If it were a Bosch, I'd think twice...
Carbsv2@reddit (OP)
I'm rough on it, I'd rather replace the nylon gears than risk shredding the sun or ring gear, or frying the coils
Ohm_Slaw_@reddit
That's a good plan, smart.
That is, BTW, the nastiest looking set of planetary gears I've ever seen. :)
tk42111@reddit
Oh man i blew one up so bad, one gear broke in half and shredded the other 2. This one’s close though!
Carbsv2@reddit (OP)
Lol, Thanks?
Ceverok1987@reddit
This is making me think about getting replacements ready preemptively. How many miles did you have on it, which setting do you normally run in, etc?
Carbsv2@reddit (OP)
4000km, PAS5 in good conditions PAS3 in icy conditions. Been riding 25km round trip every work day.
kazuviking@reddit
Brass gears with Mobile grease 28. It would still act as a fuse but would last way way more.
STIHL_Resolve5198@reddit
Planned obsolescence done right, not as a scheme to buy more a planned venture to make ebikes more usable
kazuviking@reddit
With metal gears you would have to replace the entire thing and not just the planetary gears.
Carbsv2@reddit (OP)
The great thing is that, even IF i had to replace the motor, or even the whole bike, it's still way cheaper than operating a car and driving every day. I could buy 3 or 4 bikes a year for what it costs to pay a car payment and operate it for a year.
jim914@reddit
When I was buying my e-bike conversion kit I had a choice of the pricier geared hub touted as the new and improved version or the direct drive hub which was heavier and a cheaper price because they were clearing inventory. I started researching both and found out those plastic gears tend to break often especially if they are ridden hard or under heavy load for extended periods. Knowing I’d be using it on a heavy city style bike and I wanted to be able to use throttle a lot of the time I chose the direct drive style and I’ve never had to service my hub other than once in six years time I had it off the bike to change tires and opened it just to check it and decided to pack the bearings with fresh grease but it was not a necessity just a precaution.
stormdelta@reddit
Yeah, direct drive hub is great if your priority is low maintenance and simplicity, I love mine.
The downsides are they're heavier and less efficient, and you need more power for decent torque.
jim914@reddit
But I ride mainly city streets no hills so more torque means nothing to me in fact I may have to consider getting out my copy of the settings because in my area they recently refused the speed limits for e-bikes and if they start enforcing it I’ll need to set my speed limiter again. I currently have it set wide open because the bike can barely get to 25 mph which is fine for my needs but the new limit is 20 mph for all e-bikes. I’ll take less maintenance and no break downs any day the extra weight is easy to deal with!
FatFrenchFry@reddit
I had no idea they made Nylon gear sets for motors... I've only ever seen metal planetary gears in bike motors. Yet again, I've only ever opened like 2 or 3 bike motors. And 2 of them were for a surron.
Veganarchy-Zetetic@reddit
'Using white lithium grease on nylon gears is generally discouraged because it is petroleum-based, which can break down, soften, and cause premature failure in nylon components'
Molykote PG-75 + MOBIL 28 grease are FAR better suited for nylon gears.
JG-at-Prime@reddit
Teef
Nummers.
Be careful to check the width, depth and “toof” count before ordering.
Be sure to check if your grease is compatible with nylon.
Assuming you choose nylon. Composit gears may be available.
Carbsv2@reddit (OP)
I most certainly did, It's a good thing to mention for others though
tokin247@reddit
Nylon saves the day again
wlexxx2@reddit
only $20 if you do it yourself
Carbsv2@reddit (OP)
I mean.. yeah?
Fair-Discipline-1005@reddit
Where did You buyed plastic planetary gears for this money?
Carbsv2@reddit (OP)
Amazon
Fair-Discipline-1005@reddit
Thanks...👍
wdaloz@reddit
Yea i had this happen but it wound up torquing the spindle and the whole thing is demolished.
Huge-Community-1324@reddit
Same issue had but didn’t know ! Wish I had known . Bike fell off because of a minor gust while on the kick stick .
Airzone_@reddit
Carbsv2@reddit (OP)
TBF I did pretty much everything that's hard on planetary gears for 4k km this year (including, but not limited to, full throttle take offs at -35 C while climbing hills).
Just going to start making planetary gear replacement part of my bi-annual maintenance. It's cheap, and not much more work since I'm taking the back wheel off twice a year to swap tires anyway.
ShredGuru@reddit
I just buy a few off Alibaba. It's a pretty easy fix.
Airzone_@reddit
Fair enough
Significant-Pen-6049@reddit
Hey good work!!
Carbsv2@reddit (OP)
Cheers!
bike2026@reddit
I'd hate taking all the spokes loose
Carbsv2@reddit (OP)
Didn't have to? The casing with the ring gear has the attached spokes. The motor was removed with a gear puller and had the clutch and gear assembly attached
Veggyhed@reddit
What motor do you use and where did you buy the replacement gears?
Carbsv2@reddit (OP)
I have a Jasion EB5 Max, same motor it came with, but I reprogrammed the controller to limit the speed to 32kph instead of 45kph. found the proper set of gears on amazon.
I know the brand has very mixed reviews but I've put 4k km on it in 11 months from +35 C to - 35 C, I've beat the shit out of it, and have been very happy.