[XAP]Bob wrote:Can't see what action moving the motor away is providing either. Can't even see what *direction* the motor would move
If I am understanding it right, the motor is at the other end of the loop of chain & the springs in the above mechanism act as a chain tensioner. If you move the motor end closer the segments spring out to take up the extra chain length & in doing so form an effectively larger sprocket.
As a side note, I think with this design there will be problems with slippage as the teeth do not cover 180 degrees, so there will be times when no teeth are in contact with the chain unless you plan to use some sort of jockey wheel arrangement to increase the chain wrap.
Rick.
Ah, so this is an INPUT sprocket. I assumed that it was the output of the motor (or a chainring if you will)
Presumably you could effect the same by having a moveable idler on the "slack" side of the chain.
A shortcut has to be a challenge, otherwise it would just be the way.No situation is so dire that panic cannot make it worse. There are two kinds of people in this world: those can extrapolate from incomplete data.
Sorry Bob - yeah. If you were to do a bike version the idler on the slack side would be a good place to put the "gear cable" (considering you can't exactly start swinging the axle or the bottom bracket around). This design, modified for a bike crank, would give 33% range with 9 steps, might be practical to fill in the big gaps in a sturmey 3 speed.... Nah - a deraillieur's better isn't it.....
If you used a grippy belt rather than a chain (or toothed belt), you could do this rather more easily...
Are these cars powered by fuel or electricity? (Just curious like, but if not mistaken, motors don't need gearing as the torque doesn't vary over RPM range. Maybe. ).
bobc wrote:Sorry Bob - yeah. If you were to do a bike version the idler on the slack side would be a good place to put the "gear cable" (considering you can't exactly start swinging the axle or the bottom bracket around). This design, modified for a bike crank, would give 33% range with 9 steps, might be practical to fill in the big gaps in a sturmey 3 speed.... Nah - a deraillieur's better isn't it.....
I was hoping it might make an interesting "outer" chainring... Although the derailleur might need some thought, sliding up the post as the "gear" is changed...
A shortcut has to be a challenge, otherwise it would just be the way.No situation is so dire that panic cannot make it worse. There are two kinds of people in this world: those can extrapolate from incomplete data.
mrjemm - look at www.greenpower.co.uk it's a schools STEM enrichment organisation & they use a wheelchair motor and a couple of 35Ah 12V lead acid batteries. Our cars at the moment are Dougal and Brian. Fairly big rule changes this year mean we need to re-evaluate our transmission choices. Our school is Sandbach High for girls www.cauc-f24.org. There are about 500 registered teams, a good proportion of whom get out and race at local heats & the national finals in October. We should be visible at the Sandbach festival of transport on Sunday if anyone drops by for a looksee
Test assembly on its test jig (has motor mount & ratio change mechanics on an old decking board....) Actually looks OK so far........ bit more fettling to do & then get it on the dyno...... there might be a bit of a youtube vid of that...
A shortcut has to be a challenge, otherwise it would just be the way.No situation is so dire that panic cannot make it worse. There are two kinds of people in this world: those can extrapolate from incomplete data.
"Maybe trim some of thise bolts?" ah- those sticky out bolts will have elastic bands on to pretension the chain...... this is a sqaulid prototype after all....
Just a bit of progress - assembled and operating now; I've had to fettle a few things + I still need to add some small nuts/bolts near the end of the lobes to locate 'em sideways, otherwise it's all doing pretty much what it should, & the dodgy crank handle gear change mechanism is also doing its thing. I need some more elastic bands too - I only had one in the house. Perhaps I'll replace them with springs eventually......
bobc wrote:Just a bit of progress - assembled and operating now; I've had to fettle a few things + I still need to add some small nuts/bolts near the end of the lobes to locate 'em sideways, otherwise it's all doing pretty much what it should, & the dodgy crank handle gear change mechanism is also doing its thing. I need some more elastic bands too - I only had one in the house. Perhaps I'll replace them with springs eventually......
Can you pop up a video when you get a chance. I'm intrigued...
A shortcut has to be a challenge, otherwise it would just be the way.No situation is so dire that panic cannot make it worse. There are two kinds of people in this world: those can extrapolate from incomplete data.
OK, it's not really ready for the world to see yet, but here it is changing gear for me. I have to remake some of the innards & the motor position has to be just right for each gear & it will need to be run in a bit but the potential is there https://www.youtube.com/watch?v=BHjM0Ol ... e=youtu.be
Progress, sprocket working much more nicely now after some adjustment & fettling & remake of the expanding lobes (these now feature better chain location & sideways position control at the lobe tips) The plan is to try it in a car in fixed gear position on tuesday, see if it's reasonable. If it works OK the motor position will eventually be automatically servo controlled to set the gearing in the car.
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