Hi all,
I introduced myself over here, thought I'd take a bit of time and introduce you to my more-or-less continuous R&D powered bike project. This nuttiness has been going since about 2002.
TourSleazy (TS) is so named because it is inspired by the TourEasy LWB layout but built mainly out of junk. It started life with solid suspension front and rear,
but when my knees complained, TS sprouted a Honda G100, 97cc sidevalve engine. Riding the bike in its early human powered configuration dictated that rear suspension was necessary to cope with marginal roads at high speeds (for a bicycle, that is). I cut up a junked MTB with a cantilever rear suspension and grafted that into TS's frame.
There's numerous ways to transmit drive to the rear wheel on a motorised bike, some better than others. Tyre friction drives are the least desirable because of tyre wear and drive wheel slippage when there is moisture or other contaminants on the tyre tread surface. Drive sprockets clamped to wheel spokes IMNSFHO are downright unsafe, though I'm quite aware that a number of kits use this method. Spoke breakage looks like too real a possibility for my tastes.
While it would be much more mechanically complex than other means, I concluded that the safest, most durable and efficient way to transmit drive to the rear wheel was via the existing chain and sprockets. This would also facilitate the use of the derailleur's wide range of ratios with engine drive. Pedal and engine drive would both go via the single drive chain.
Isolating the engine drive from the pedal drive (so pedals don't spin when the engine is driving the bike and the pedals don't unnecessarily spin the primary drive) and combining the drive forces turned into quite a bit of an engineering challenge for this non-engineer. I came up with a differential drive system which allows drive either from the engine, the pedals or both simultaneously, in any proportion. This is accomplished by way of a 5/8" shaft running in ball bearings which are fitted to the former BB shell in the rear suspension's cantilever.
On the engine drive side of the shaft is a BMX-type freewheel, fitted via a custom machined adapter (33mm fine thread to 5/8" keyed shaft). There's an 84T (bout 10" dia) sprocket for #35 chain bolted between the teeth of the sprocket on the engine drive side- a chain runs from the 'dinner plate' sprocket to the centrif clutch on the engine. The LH side freewheel does not have to be modified to run 'left handed' as the shaft adapter allows use of an ordinary freewheel.
On the other side of the shaft, there's two more freewheels mounted on another custom machined 33mm threaded->5/8" keyed shaft adapter. A 5-speed rear wheel cluster fitted to the outside end of the shaft isolates the shaft's rotation from the pedal drive. If the engine is not running, pedal drive spins the jackshaft but the freewheel on the 'dinner plate' prevents the engine's primary drive and clutch driven cup from being spun.
Another BMX freewheel with an 18T sprocket suiting derailleur chain, is used to transmit drive to the rear wheel. This one doesn't really need to be an operating freewheel, could be a sprocket simply fixed to the 33mm>5/8" shaft adapter. The freewheel action of the derailleur cluster in the rear wheel makes this drive freewheel redundant- it's just a convenient way to fit a sprocket to the 5/8" jackshaft.
One of the biggest challenges in motorised bike construction is getting sufficient gear reduction in the engine driveline so the engine is running close to its torque peak when the bike is at ordinary bicycle road speeds (up to 50km/h). Small 2-cycle (ie weedwacker) and 4-cycle engines (ie GX31) operate at 7200rpm. Not only did I not want a tiny little engine on the bike screaming at high revs, I found that fitting sufficient gear reduction for an engine turning 7200rpm would take more than chains and sprockets, given the possibilities of readily available components and the size of existing sprocks on the centrif clutch and rear wheel. It would take a gear reduction box, heavy and expensive. So, I selected a slightly larger but slower spinning engine than most builders employ. I found a 2nd hand Honda G100, 4-stroke 97cc sidevalve motor which runs at 3600rpm and worked that into the design. Bonuses are that the Honda motor can sit for months unused yet start on the 1st or 2nd pull, every single time. The sidevalve (flathead) engine design favours high torque at relatively low RPM on the torque curve, meaning the engine works better running slower- and quieter.
All well and good- until out on the road, of course!
In practise, TS is great to ride, until one is tempted to run it as fast as it can go. At ordinary bike speeds (40km/h and under), the drive system behaves very well.
However, when pushed to 55-60km/h in 7th gear, the final drive chain is on the smallest sprocket on the rear derailleur. This means that the chain is being held in tension only by the derailleur tensioner and is really quite floppy.
This becomes a problem on rough roads, where the drive chain tends to jump off the driving sprocket on the jackshaft. I added a tensioner on the 'pull' side of the final drive chain, which aligns the chain before it gets to the driving sprocket. Works very well- but the plastic idler wheels on the tensioner get chewed up very quickly (about 200-300km per set of idler wheels).
TS is torn down at this moment, clamped up in the workstand, getting a new front frame section to suit a suspension/disc brake front end, shown here in mockup.
The driveline problem is going to be sorted while it's there. To eliminate the slacky drive chain, I was thinking about fitting a 3 to 7 speed internally geared rear hub, but @Alaskavan brilliantly suggested the NuVinci CVT hub.
I'm investigating both options, as they would eliminate the need for a chain tensioner in the final drive. I can also fit a larger sprocket to whatever size sprock is supplied on either the NuVinci or traditional internally geared hub, to slow the bike down a bit and improve hillclimbing abilty. I just need to do some research on exactly how much torque these hubs can be expected to handle. Hard info to come by as the makers of these hubs are not usually interested in supplying information for non-standard applications of their products.
I also have a Comet 'Torq-A-Verter' TAV-30 belt-type torque converter sitting on the shelf, bought for another project, but it may have an application in TS's driveline. If I were to fit the TAV in TS's primary drive, replacing the centrif clutch but driving the existing 84T dinner-plate drive reduction sprocket on the jackshaft, it would add another 2:1 reduction multiplication (when the engine is running wide open- the TAV is 0.92:1, a bit of overdrive, at lower RPMs), increasing the primary driveline reduction to 14:1. 1st gear would then be about a 28:1 reduction with the engine on the 3600RPM governor, making for SERIOUSLY stump-pulling hillclimbing power, necessary for my new mountainous surrounds. I'd prefer to reserve the TAV for the other project, but we'll see where I wind up.
Thanks for suffering through the long post, but I'm catching you up on the last 6 years.
I'm happy to answer questions about TS but I'm happier yet to get good suggestions for improvements.
I introduced myself over here, thought I'd take a bit of time and introduce you to my more-or-less continuous R&D powered bike project. This nuttiness has been going since about 2002.
TourSleazy (TS) is so named because it is inspired by the TourEasy LWB layout but built mainly out of junk. It started life with solid suspension front and rear,
but when my knees complained, TS sprouted a Honda G100, 97cc sidevalve engine. Riding the bike in its early human powered configuration dictated that rear suspension was necessary to cope with marginal roads at high speeds (for a bicycle, that is). I cut up a junked MTB with a cantilever rear suspension and grafted that into TS's frame.
There's numerous ways to transmit drive to the rear wheel on a motorised bike, some better than others. Tyre friction drives are the least desirable because of tyre wear and drive wheel slippage when there is moisture or other contaminants on the tyre tread surface. Drive sprockets clamped to wheel spokes IMNSFHO are downright unsafe, though I'm quite aware that a number of kits use this method. Spoke breakage looks like too real a possibility for my tastes.
While it would be much more mechanically complex than other means, I concluded that the safest, most durable and efficient way to transmit drive to the rear wheel was via the existing chain and sprockets. This would also facilitate the use of the derailleur's wide range of ratios with engine drive. Pedal and engine drive would both go via the single drive chain.
Isolating the engine drive from the pedal drive (so pedals don't spin when the engine is driving the bike and the pedals don't unnecessarily spin the primary drive) and combining the drive forces turned into quite a bit of an engineering challenge for this non-engineer. I came up with a differential drive system which allows drive either from the engine, the pedals or both simultaneously, in any proportion. This is accomplished by way of a 5/8" shaft running in ball bearings which are fitted to the former BB shell in the rear suspension's cantilever.
On the engine drive side of the shaft is a BMX-type freewheel, fitted via a custom machined adapter (33mm fine thread to 5/8" keyed shaft). There's an 84T (bout 10" dia) sprocket for #35 chain bolted between the teeth of the sprocket on the engine drive side- a chain runs from the 'dinner plate' sprocket to the centrif clutch on the engine. The LH side freewheel does not have to be modified to run 'left handed' as the shaft adapter allows use of an ordinary freewheel.
On the other side of the shaft, there's two more freewheels mounted on another custom machined 33mm threaded->5/8" keyed shaft adapter. A 5-speed rear wheel cluster fitted to the outside end of the shaft isolates the shaft's rotation from the pedal drive. If the engine is not running, pedal drive spins the jackshaft but the freewheel on the 'dinner plate' prevents the engine's primary drive and clutch driven cup from being spun.
Another BMX freewheel with an 18T sprocket suiting derailleur chain, is used to transmit drive to the rear wheel. This one doesn't really need to be an operating freewheel, could be a sprocket simply fixed to the 33mm>5/8" shaft adapter. The freewheel action of the derailleur cluster in the rear wheel makes this drive freewheel redundant- it's just a convenient way to fit a sprocket to the 5/8" jackshaft.
One of the biggest challenges in motorised bike construction is getting sufficient gear reduction in the engine driveline so the engine is running close to its torque peak when the bike is at ordinary bicycle road speeds (up to 50km/h). Small 2-cycle (ie weedwacker) and 4-cycle engines (ie GX31) operate at 7200rpm. Not only did I not want a tiny little engine on the bike screaming at high revs, I found that fitting sufficient gear reduction for an engine turning 7200rpm would take more than chains and sprockets, given the possibilities of readily available components and the size of existing sprocks on the centrif clutch and rear wheel. It would take a gear reduction box, heavy and expensive. So, I selected a slightly larger but slower spinning engine than most builders employ. I found a 2nd hand Honda G100, 4-stroke 97cc sidevalve motor which runs at 3600rpm and worked that into the design. Bonuses are that the Honda motor can sit for months unused yet start on the 1st or 2nd pull, every single time. The sidevalve (flathead) engine design favours high torque at relatively low RPM on the torque curve, meaning the engine works better running slower- and quieter.
All well and good- until out on the road, of course!
In practise, TS is great to ride, until one is tempted to run it as fast as it can go. At ordinary bike speeds (40km/h and under), the drive system behaves very well.
However, when pushed to 55-60km/h in 7th gear, the final drive chain is on the smallest sprocket on the rear derailleur. This means that the chain is being held in tension only by the derailleur tensioner and is really quite floppy.
This becomes a problem on rough roads, where the drive chain tends to jump off the driving sprocket on the jackshaft. I added a tensioner on the 'pull' side of the final drive chain, which aligns the chain before it gets to the driving sprocket. Works very well- but the plastic idler wheels on the tensioner get chewed up very quickly (about 200-300km per set of idler wheels).
TS is torn down at this moment, clamped up in the workstand, getting a new front frame section to suit a suspension/disc brake front end, shown here in mockup.
The driveline problem is going to be sorted while it's there. To eliminate the slacky drive chain, I was thinking about fitting a 3 to 7 speed internally geared rear hub, but @Alaskavan brilliantly suggested the NuVinci CVT hub.
I'm investigating both options, as they would eliminate the need for a chain tensioner in the final drive. I can also fit a larger sprocket to whatever size sprock is supplied on either the NuVinci or traditional internally geared hub, to slow the bike down a bit and improve hillclimbing abilty. I just need to do some research on exactly how much torque these hubs can be expected to handle. Hard info to come by as the makers of these hubs are not usually interested in supplying information for non-standard applications of their products.
I also have a Comet 'Torq-A-Verter' TAV-30 belt-type torque converter sitting on the shelf, bought for another project, but it may have an application in TS's driveline. If I were to fit the TAV in TS's primary drive, replacing the centrif clutch but driving the existing 84T dinner-plate drive reduction sprocket on the jackshaft, it would add another 2:1 reduction multiplication (when the engine is running wide open- the TAV is 0.92:1, a bit of overdrive, at lower RPMs), increasing the primary driveline reduction to 14:1. 1st gear would then be about a 28:1 reduction with the engine on the 3600RPM governor, making for SERIOUSLY stump-pulling hillclimbing power, necessary for my new mountainous surrounds. I'd prefer to reserve the TAV for the other project, but we'll see where I wind up.
Thanks for suffering through the long post, but I'm catching you up on the last 6 years.
I'm happy to answer questions about TS but I'm happier yet to get good suggestions for improvements.
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