HeadSmess
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http://www.lovejoy-inc.com/products/variable-speed-drives.aspx
was the first result from google... theres lots of them out there and ebay is a source of cheap ones, possibly. 5/8 is a standard shaft size, and most pulleys with a "standard" size shaft will already have a keyway.
theres a few varieties, some use manual shifting, such as on bandsaws and other industrial machines(that can be adjusted on the run, instantly, unlike that scooter one...but i guess you pay for them!), some are self adjusting... as the belt loads up, it tends to "sink" into the pulley sheave, and forces it apart, down into low gear, with the tensioner taking up the slack, but varying the tension on the belt, with a fairly strong spring in the pulley, will do the same thing... the pulley spring just has to be strong enough not to spread by itself under full load
i have it in a book somewhere, but im not looking for that! or scanning it if i found it... "bicyclers bible " FYI and i did once find it on the net, but...now i cant be bothered looking
it was an automatic shift CVT for a bicycle, around about 1970 judging by the books age... i shall endeavour to explain it now but
a small sprocket was driven off the chainring. this sprocket was set in slots, so if the sprocket was "locked", it would try to rotate with the chainring along these slots.
this sprocket was connected to a split/variable pulley. it had some type of wedge affair so as the sprocket and pulley tried to rotate with chainring under load (locking the sprocket basically) the pulley would spread and drive in low gear. there was obviously another pulley, that then ran chain to the rear wheel.
as the load decreases, ie... as youre getting faster and dont have to pedal so hard, it would start shifting smoothly into a higher gear, keeping the load on the pedals fairly consistent.
it would always start in high gear, but the torque created by simply taking off would always shift it to a lower gear.
yes, it was just designed for pedalling but the basic idea is quite simple really, and easily adopted to motorised power.
(i recall one person showing a picture of his leg after having a (motorised) autoshift system fail that shifted into low... allowing the engine to rev out and drive the wheel with lots of torque...really unsafe. they should always shift to high gear if anything goes wrong, just like truck, train and forklift brakes are activated by a loss of pressure... or vacuum depending on the setup)
you would want yours to have enough slack if your tensioner system broke, to either slip or yup...allow the pulley to go into high gear...
theres a chain driven CVT out there, used on industrial machines. works exactly the same way as a standard variable pulley, just uses a chain the chain is rather unique and is the key to the whole affair the pulley has teeth
and theres been plenty of weird and wonderful patents over the last 100 years or so for bicycles
was the first result from google... theres lots of them out there and ebay is a source of cheap ones, possibly. 5/8 is a standard shaft size, and most pulleys with a "standard" size shaft will already have a keyway.
theres a few varieties, some use manual shifting, such as on bandsaws and other industrial machines(that can be adjusted on the run, instantly, unlike that scooter one...but i guess you pay for them!), some are self adjusting... as the belt loads up, it tends to "sink" into the pulley sheave, and forces it apart, down into low gear, with the tensioner taking up the slack, but varying the tension on the belt, with a fairly strong spring in the pulley, will do the same thing... the pulley spring just has to be strong enough not to spread by itself under full load
i have it in a book somewhere, but im not looking for that! or scanning it if i found it... "bicyclers bible " FYI
and i did once find it on the net, but...now i cant be bothered looking it was an automatic shift CVT for a bicycle, around about 1970 judging by the books age... i shall endeavour to explain it now but
a small sprocket was driven off the chainring. this sprocket was set in slots, so if the sprocket was "locked", it would try to rotate with the chainring along these slots.
this sprocket was connected to a split/variable pulley. it had some type of wedge affair so as the sprocket and pulley tried to rotate with chainring under load (locking the sprocket basically) the pulley would spread and drive in low gear. there was obviously another pulley, that then ran chain to the rear wheel.
as the load decreases, ie... as youre getting faster and dont have to pedal so hard, it would start shifting smoothly into a higher gear, keeping the load on the pedals fairly consistent.
it would always start in high gear, but the torque created by simply taking off would always shift it to a lower gear.
yes, it was just designed for pedalling but the basic idea is quite simple really, and easily adopted to motorised power.
(i recall one person showing a picture of his leg after having a (motorised) autoshift system fail that shifted into low... allowing the engine to rev out and drive the wheel with lots of torque...really unsafe. they should always shift to high gear if anything goes wrong, just like truck, train and forklift brakes are activated by a loss of pressure... or vacuum depending on the setup)
you would want yours to have enough slack if your tensioner system broke, to either slip or yup...allow the pulley to go into high gear...
theres a chain driven CVT out there, used on industrial machines. works exactly the same way as a standard variable pulley, just uses a chain
the chain is rather unique and is the key to the whole affair the pulley has teeth and theres been plenty of weird and wonderful patents over the last 100 years or so for bicycles
