Bosch bearings

[mfj197]

Not sure about the impact of a small front ring on chain/ring wear, but I agree it's unlikely to be possible to change the gearing from that end.

There are a few alternative front sprockets for the Bosch system. Martin at e-bikeshop sells a 15t (equivalent to 37.5t after the 2.5x gearing), an 18t (45t equivalent) and a 20t (50t equivalent). The KTM and Haibike cross bikes come with the 18t sprocket whereas the MTBs generally have the 15t one.

Had my own chain come off on Monday, on my road bike...

Michael

 

[tillson]

How do we get a Mk2 if nobody buys the Mk1's.

Someone will always buy the Mk1s, it's just not going to be me. There will be plenty of Mk1 buyers camped out on the streets very soon. They will be outside Apple stores and eager to hand over their cash for the Mk1 iWatch.

 

[tillson]

Also it's almost impossible for the chain to jump off which is an intermittent problem on all bikes.

The chain inevitably jumps to the inside and jams around the bottom bracket.

Jamming is increased by the forward motion of the pedals, albeit they swiftly grind to a halt.

I've seen instances where the chain has had to be snipped to free it.

It can certainly finish your ride unless someone happens by with a very beefy screwdriver or pry bar.

I must be really lucky because this has never happened to me and I cycle a few thousand miles a year. These days the mileage is split between my ebike which has a Panasonic motor and 8 Speed hub gears (never had a problem), and a Cube road bike which has derailleurs, which again have never exhibited the chain jamming problem.

I had absolutely no idea how massive the chain jumping / jamming issue was, so massive in fact that it has required a radical re-think of bicycle transmission. Appalling, dreadful transmission which we have apparently been suffering for decades, finally solved by Bosch. Thank you Bosch for finally righting this flaw in the humble bicycle.

 

[flecc]

But as I've posted, implemented by Bosch not particularly for bicycle reasons but for e-unit efficiency. The chainwheel motor drive units like the Bosch have been suffering some loss of efficiency due to the multi-stage gearing necessary to reduce the motor speed to the very low chainwheel speed.

This made their efficiency compare badly with the new Panasonic unit which, due to it's separate very small motor drive sprocket needed only a single stage gear reduction, something which Panasonic had been using in their promotional material.

The bicycle benefits I listed previously, which are very real, are a welcome bonus, in exchange for a slight loss of rider efficiency which with e-assistance is trivial.

The conservatism of British cyclists will tend to blind them to the cycling advantages. Not being utility cyclists they usually don't want chaincases or even chainguards, but the huge cycling markets elsewhere often do and will appreciate the improvements to these that a small chainwheel can bring. And of course when not using chain shielding they won't appreciate the scale of difficulties that a derailled front chain can bring, as experienced by Phill whose post I linked to above. True utility cyclist who use their bikes continuously without special preparation also appreciate the lack of personal soiling that a small chainwheel brings, even without cycle clips.

So I don't blame Bosch designing for where nearly all their e-bike sales are, rather than the tiny British market.

Small chainwheels are not unknown in the cycling market anyway. The Sunrace Sturmey 8 speed hub gear necessitates use of a small chainwheel, the front and rear sprockets similar in size. Once again that is for efficiency and cycling reasons, since it has it's direct drive in bottom gear to maximise the rider's efficiency when the going is toughest, up steep hills.

That means all the other gears are higher, so with a normal large chainwheel there would be no low gears and impossibly high gears at the other end. Hence the small chainwheel which brings the other advantages mentioned previously.

Those who've seen my posting input through the life of this forum will know how scornful I've been about the many silly attempts to improve upon the near perfect design of the diamond frame bike. Not being a bigot, that doesn't prevent me from recognising the very rare occasion when something really does bring an overall advantage to an e-bike when all factors are considered. This by Bosch is one such.

For those either blind to the advantages or who who have no use for them, fine, buy something else, there's now an abundance of large chainwheel crank drives available.
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[tillson]

I'm all for innovation and development, where innovation and development are necessary. I think that the problem I have with the Bosch small drive sprocket is that it addresses issues which I have never experienced, or found to be an inconvenience. That said, maybe they screwed up the Mk1 motor and made it such that the chain can jump and get stuck between the frame and chain wheel. Does the Impulse motor do the same, or is this a feature which is exclusive to Bosch? So perhaps the workaround in the form of a tiny chain wheel is one solution.

I'll accept that a sufficient number of people manage to wrap their trousers up in the chain to make the Bosch Mk2 a good idea. I'm not one of them and I don't know anyone who is, but clearly they must exist.

 

[flecc]

Well, I've linked you to those who can suffer the chain off problem and assure you that it is not uncommon in normal unpowered cycling as well as in various e-bikes, not just Bosch and not just crank drives.

It's far more common with derailleurs and is caused by a variety of conditions which I well understand, some of which can occur to anyone in a completely random fashion, others more likely due to particular cycling characteristics, others due to terrain conditions. It follows that some will never suffer a single occurrence while others will suffer it on enough occasions to make it a nuisance.

In efficiency gaining terms the Bosch solution is better for many than the Panasonic one on their later higher powered units units, which as you will have seen in here, have suffered numerous small motor sprocket/idler/chain path problems which have been difficult to overcome when they've occurred. There won't be any such problem on the Mk 2 Bosch.

I haven't mentioned trousers getting caught up in chainwheels, only the very real soiling from contact. If you think that doesn't exist, perhaps you could tell me why cycle clips have been on the market and sold in large quantities for over a century?
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[KTM Bike Industries UK]

Bikes have had chainrings getting smaller and smaller for the last 10 years for a number of reasons. The two main ones, are smaller = Lighter, and smaller = less material, which means cheaper.

The other reason about Bosch, is because of motor gearing, which has already been discussed.

I'm afraid Flecc, it has ZERO to do with trousers or anything like that.

Brands over the past 15 years now fit guards to the outer chain ring which means you don't need to worry about trouser clips anymore.

http://www.britishcycling.org.uk/commuting/article/trav20091020-Daily-Commuting-Tip--Save-your-Trousers--0

 

[flecc]

I'm afraid Flecc, it has ZERO to do with trousers or anything like that.

Brands over the past 15 years now fit guards to the outer chain ring which means you don't need to worry about trouser clips anymore.

Which are far from being fully effective, trouser clips still stocked and selling in consequence. I didn't say this was a reason for Bosch to adopt a smaller chainring, I listed it among others as an incidental welcome advantage and have repeated that since.

In that respect it does have something to do with trousers, the world being somewhat larger than the viewpoint of Bosch.

Click the following link and scroll down to see all the models illustrating what the sensible Dutch think about chainwheel guard rings on utility bikes. Batavus
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