Hi All,
I am in the final stages of planning for my first build and have several question regarding final belt drive systems, similar to those used on the 1911/12 Indian Belt Drive Single and the 1910 Harley Davidson.
Basic Components
The bike will be powered by Honda GX160 or clone. The governor will remain as 3600 rpm is more than enough for this style of bike. This bike is intended to be for cruising and minimal stop / start riding. Having said that, there will be times where slow speeds are required in busy traffic areas. I will use wide 26 inch rims with 90mm sturmey archer front drum brake hub and either a 70mm sturmey archer drum hub or coaster brake for the rear.
The engine will be mounted with the cylinder more upright than standard to add to the appearance of the bike and to better fit into the vintage styled loop frame. I have searched the internet and cannot find any negative comments about increasing the angle of the cylinder, apart from a slightly higher oil level in the sump.
I intend to use a belt drive directly from the engine crankshaft to the rear rim. From my research, the flat belt would be a better option that the A or B section V belts. The reasoning is twofold; a flat belt has better grip and flexibility around a smaller drive sprocket (less than 3 inches), and the flat belt may provide better slip for when the clutch is disengaged. V belts would provide superior grip, but free-wheeling when the idler clutch is released may be an issue.
Thanks to JPilot's gear calculator, I propose to use one of the following sprocket options to obtain the desired gearing.
Option 1 - 9.60:1
Front sprocket - 2.5 inches
Rear sprocket - 24 inches
Clutch engagement speed (1500 rpm) at 12 mph
Top speed (governed 3600 rpm) at 29 mph
Option 2 - 8.00:1
Front sprocket - 3 inches
Rear sprocket - 24 inches
Clutch engagement speed (1500 rpm) at 14.5 mph
Top speed (governed 3600 rpm) at 34.8 mph
A review of the 1912 Indian discusses the clutch as follows, "if the jockey wheel was dropped completely down, the belt would slip over the pulleys, just like being in neutral, and grip could be gradually increased as necessary, or a partial-slip condition used in case of difficult terrain".
My questions refer to the slippage of this style of clutch. Fully released and fully locked should be easily achieved by the use of a lever and spring loaded mechanism that provides sufficient tension without stressing the belt. The partial slip setting is where I am uncertain about the effectiveness of the drivability. Partial engagement would enable some slip and a setting could be made to lock the clutch in 50% engagement for slow riding. In theory engine idle rpm ( or slightly above) and an amount of clutch slip below the 100% clutch lockup should enable slower bike speed.
Do any members have experience with this style of clutch and provide some information on the nature of how this would work in real conditions? If this slipping of the clutch is effective, could it also be used as a standard form of clutch / drive engagement from a standing start? Would the engine idle rpm need to be raised to provide a rpm buffer to compensate for the additional load from the engagement?
Any information would be greatly appreciated.
I am in the final stages of planning for my first build and have several question regarding final belt drive systems, similar to those used on the 1911/12 Indian Belt Drive Single and the 1910 Harley Davidson.
Basic Components
The bike will be powered by Honda GX160 or clone. The governor will remain as 3600 rpm is more than enough for this style of bike. This bike is intended to be for cruising and minimal stop / start riding. Having said that, there will be times where slow speeds are required in busy traffic areas. I will use wide 26 inch rims with 90mm sturmey archer front drum brake hub and either a 70mm sturmey archer drum hub or coaster brake for the rear.
The engine will be mounted with the cylinder more upright than standard to add to the appearance of the bike and to better fit into the vintage styled loop frame. I have searched the internet and cannot find any negative comments about increasing the angle of the cylinder, apart from a slightly higher oil level in the sump.
I intend to use a belt drive directly from the engine crankshaft to the rear rim. From my research, the flat belt would be a better option that the A or B section V belts. The reasoning is twofold; a flat belt has better grip and flexibility around a smaller drive sprocket (less than 3 inches), and the flat belt may provide better slip for when the clutch is disengaged. V belts would provide superior grip, but free-wheeling when the idler clutch is released may be an issue.
Thanks to JPilot's gear calculator, I propose to use one of the following sprocket options to obtain the desired gearing.
Option 1 - 9.60:1
Front sprocket - 2.5 inches
Rear sprocket - 24 inches
Clutch engagement speed (1500 rpm) at 12 mph
Top speed (governed 3600 rpm) at 29 mph
Option 2 - 8.00:1
Front sprocket - 3 inches
Rear sprocket - 24 inches
Clutch engagement speed (1500 rpm) at 14.5 mph
Top speed (governed 3600 rpm) at 34.8 mph
A review of the 1912 Indian discusses the clutch as follows, "if the jockey wheel was dropped completely down, the belt would slip over the pulleys, just like being in neutral, and grip could be gradually increased as necessary, or a partial-slip condition used in case of difficult terrain".
My questions refer to the slippage of this style of clutch. Fully released and fully locked should be easily achieved by the use of a lever and spring loaded mechanism that provides sufficient tension without stressing the belt. The partial slip setting is where I am uncertain about the effectiveness of the drivability. Partial engagement would enable some slip and a setting could be made to lock the clutch in 50% engagement for slow riding. In theory engine idle rpm ( or slightly above) and an amount of clutch slip below the 100% clutch lockup should enable slower bike speed.
Do any members have experience with this style of clutch and provide some information on the nature of how this would work in real conditions? If this slipping of the clutch is effective, could it also be used as a standard form of clutch / drive engagement from a standing start? Would the engine idle rpm need to be raised to provide a rpm buffer to compensate for the additional load from the engagement?
Any information would be greatly appreciated.
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