So, why not have a CVT style gearbox system with two opposing tapered rollers with one being the input the other the output and some kind of flexible rubber belt joining the two?

These have been made before sadly the requirement is quite a bit of pressure between the intermediate roller input and output

1. on top of this you need to somehow disengage one of the rollers to slide it sideways or the actuator must overcome these forces and shunt something sideways, never a good plan or have some kind of linkage to bring it in to contact precicely ,and keep that rigid too ….you see the cascading effect the gearbox is already getting complicated and stiffer and heavier

2.1 the belt usually sits between an input pulley and an expanding and contracting pair of pulleys which are a further distance apart in low and closer together in high this means as they pinch the drive belt it rides up the tapered cone pulleys altering the ratio

CVTs are normally run at constant speed also its very odd hearing a car just revving its tits off/droning along

2.2 the pressures involved mean a stiff casing is required for the bearings and to keep those things locked down tight

2.3 to run a belt on rollers would twist at its extremes and you need to deliver torque , to get enough tension on the belt go back to 1. and see how much tension you actually need to put a belt on a smooth pulley to transmit the torque to move a bike they are pretty shite at torque low down which is what legs make , its a tiny little highly loaded belt and no you cant put scerations on the belt – a la gates because it tapers

3. soft squidgy transfer rollers have been tried and eat themselve and deposit themselves on either the drive or output roller very rapidly causing wear

4. hard as **** transfer rollers have been tried and cost more than a real live baby jesus to produce.

5 transfer fluid has been tried, this is not the same as Atomatic transmission fluid…. Oils like Shell morlina have a very high pressure rating but do not lubricate at all . Traditional Gears tend to work in a very basic sinusoidal way to a degree they only transmit power over a pressure angle on the gear each tooth might be 15 or so degrees a bit like a cam and that pressure needs lubricating as the faces slide across one and other (this isnt a cover all of all types of gears as there are many types that comes with pros and cons but the pinnion we took to pieces here and stored for scrap future examination now i know its faults …..why i mentioned the oil is that mechanics tend to go oooh arrgh ATF its exactly the same stuff….er no its not and so you end up with loads of completely **** worn out bits for anything that relies on traction fluids …i can tell you this because every colchester chipmaster thats ever had one of these morons near it now has a knackered Kopp VARIATOR

which brings us to

the Nuvinci which uses a special traction fluid which is effectively a miniature KOPP variator from the 50s as used in lots of machine tools and just like machine tools they weigh more than a ton, maybe …well not at all but they arent going on weight weenies any time soon

finally Oils which provide traction are like ethanol if theres a crack in the casting they will find a way to get out and then you need to start sealing things to take this into account

i might do the goods and bads of Pinion tomorrow i fuckingn hate writing stuff

ps good job Ben It seems gearboxes are the future of COMMUTER type bikes it would be great if someone made a hole in the top so you could just put an extra gear in and connect the motor instant e bike……

might do the goods and bads of Pinion tomorrow i fuckingn hate writing stuff

Write it – I’d be interested.

bencooper – Member

Thanks

Sorry, I didn’t mean to be rude. I like the bike from a practical point of view just the headtube made me think it was BIG.

Write it – I’d be interested

Me too. My test ride on 18 bikes demo has left me wanting a pinion bike. Weight and the shifter are the common complaints and for me the benefits outweigh these. The P.12 has a 600% range, when 12 speed Shimano XT comes out it won’t match that and will probably weigh even more 🙂

Sorry, I didn’t mean to be rude.

I didn’t think you were 😀

It’s not conventional geometry – 68deg ST for instance – but it works for this person. And I liked it when I test-rode it too.

Ben have you ever fitted a nuvinci 360 to a Brompton? (I’ve a hub left over from my cargo bike and have been considering using one of your 135mm rear triangles)

Not yet, though will do a belt drive version in a couple of weeks. I can’t see any reason it won’t fit, might need a little bogging of the tensioner, that’s all.

Ben, excellent I’ll be in touch to order some bits when I’m back from my travels