After motor Failure and then motor noise on my 19, I took matters in my own hands and have rebuilt the motor myself and for others. This is a brose issue. First, motor clearances are very sloppy... bearings to housings just drop in no press fit so the motor relies on belt tension to preload and hold the motor/planetary bearings tight to the housing. The issue is the planetary grease is not sealed and gets onto the belt so as the belt wears and loads with grease the bearings become loose in the housing and the motor rotor has no rear bearing so when the outer bearing becomes lose due to belt wear, this causes the rotor to vibrates due to the magnetic field forces. The grease saturation of the belt and stretch over time causes them to slip/break or cause noise. The other big issue is the needle bearing that supports the inner shaft as it passes threw the outer drive sprocket is not sealed and is directly exposed to outside dirt/water. If basic preventative maintenance was allowed, this motor would last forever. The ones I've rebuild are smoother/quieter than new because I use way better grease and shim for tolerances.
Main things you can do to prevent the motor from failing. First- adjust belt tension every 300 miles or so this is done externally via the Allen set screw on the bottom. 2nd get a grease gun with a needle attachment and fill the space between the crank shaft and sprocket shaft there is a fingernail thick gap there that goes straight into the needle bearing the grease will stop water-dirt from getting in there. then install a felt washer between the crank arm and sprocket shaft this will stop the dirt from contaminating the grease. Again if we were allowed to do the simple belt adjustment which takes less then a min, this alone would save 2/3 of the motor failures out there. I say allowed because they hide the belt adjustment screw under the do no open sticker on the bottom and poping that sticker could cause a warranty issue- thus the double edge sword... adjust it and don't have a failure.. or don't adust it and have a failure that warranty should cover but takes you off the trail for a few weeks? If people are interested I can make a tutorial.
PLEASE STOP!! Read this before following the above advice.
I really don't want to argue about this, or upset anyone who has put effort into trying to find issues and fixes for these motors. Hopefully most of you know me and how many of these motors I work on every day. And that I have a very long and sound mechanical engineering and design background.
I will try and explain a few of the issues picked up by Cncninja:
1, The crankshaft bearings are a smooth fit into the motor cases so that the belt cover can be removed after being fitted. If both bearings were pressed into the covers, you would have a real struggle to remove the belt cover (This is exactly the same with the Yamaha, Shimano etc.) If you look very closely at how the Brose is put together There is a spring 'wave' washer that sits in the centre of the crankshaft and pre loads the bearings against the outer covers and this is compressed as the belt cover is tightened. Most people don't realise this is what the rubber lip on the outer edge of the outer crankshaft bearing seals is for, it is to stop the bearing rotating in the cover once the cover is tightened down on it (Yamaha, Impulse, Panasonic etc. have o-rings around their bearings for the same reason). This fact is also often missed because the wave washer gets partially flattened when the crank assembly is pressed out. This should be re-set before being refitted.
2, The Brose electric motor shaft support bearing is also situated in the belt cover and again, this could not be a press fit as the belt cover must be removable. The pre-load by the belt is extremely light and Brose have now introduced an O-ring to this housing above the bearing to eliminate movement or noise.
3, The grease found in the belt area is a type of Vaseline used to lubricate the belt when it is new. There is not enough grease in the planetary gears to actually leak anywhere?
4, The motor rotor is surrounded equally on all sides by many small rare earth magnets, there are no magnetic field forces as the force is pulling from 360 degrees and neutralises any forces. If you remove the small case bearing, you will find two more below it. Once the belt cover is fitted they make an extremely strong platform for the gearing and drive belt pulleys.
5, The drive belt itself is manufactured from continuous strands of carbon fibre and is virtually stretch resistant. Carbon fibre is not generally affected by hydrocarbon, silicone or lithium based greases or oils.
6, The crankshaft needle bearing is a 2RS bearing and has a seal in each side (granted they don't work too well, but they are there)
7, The drive belt tension is absolutely critical and is factory set and tested to last the expected life of the belt (15,000km) I really would not advise poking around with an allen key unless you own a torque driver that will go down to the very, very low setting required. (The cheapest torque driver to go down to less than 0.3Nm is approx. £65.00). The torque screw is set with loctite and the screw and case thread must be cleaned thoroughly if the belt tension is going to be re-set, so all in all, not a good thing to play with.
8, As I have pleaded in many of my other posts: please don't put grease or oil in the gap between the sprocket carrier and the crankshaft! Firstly, any dirt or grit could get pushed into your crankshaft needle roller bearing. Secondly, the motor is not designed to have grease or oil in it. If and when this grease makes its way past the needle bearing it dilutes the special grease used for the sprag clutch bearings and gets into the torque sensor wiring and pick-ups. It also makes a right bloody mess that I get fed-up cleaning out!
9, Please take care when using felt washers in off-road applications. A felt washer if left dry or not changed regularly will turn into a piece of sand paper and I have seen bad damage done to crankshafts and cases where the washers have been neglected or used in the wrong circumstance.
10, Just to put it into some sort of context I have just looked at the last two months of motor repairs. I have done 37 Brose motors and only one of them was a belt failure. Most claimed belt failures are actually sprag clutch bearing failures. A clutch bearing can give the exact same symptoms of a belt failure, so most people post "belt failure" when it isn't.
Again, I honestly mean no malice in my post, and I am in no way sticking up for the Brose motor. But, as someone who does these things in their sleep, I had to say something.
Cncninja, Please feel free to contact me
[email protected] I would rather work with someone than against them.
