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dgray56
Guest
It was not my intent to create a controversy or offend anyone with my casual post; however in my haste it would appear that I have done just that. Please allow me to explain. I will start by addressing your response and end by explaining in more detail my original statements.
Yes, with the standard 10 tooth front sprocket and a 36 tooth rear sprocket in a single drive ratio configuration, it is not only doubtful that this engine would power any bicycle to over 50 mph, it is not possible. Using a 12 tooth front sprocket and a 32 tooth rear sprocket 50 mph is not only possible, it reduces top end rpm's considerably for nominal power output (average speeds of between 30 and 35 mph). No, I was not abusing this engine, and have actually expended considerable time and effort to improve this power plant to determine if factory modifications would be feasible within the manufacture's cost constraints. Driving the engine at high (not excessive) rpm's for extended periods of time (1 to 2 hours) is part of my test plan to expose possible component failure, e.g. improve durability.
Allow me to introduce myself. Without going into exhaustive details about my education, background or other self indulgent displays of bragging rights, suffice to say that I'm a fairly qualified mechanical engineer. I have earned several graduate degrees in advanced science, have a considerable background in many fields of engineering, and have been modifying internal combustion engines (2 and 4 stroke; considerably bigger and far more complex than this particular power plant) for the better part of 4 decades. Now that, that is out of the way please allow me to explain my previous statements.
I have been searching for a cheap, lightweight, efficient power plant for a specific task. Not finding off the shelf components up to spec., I have been looking for something that can be practically modified (by this I mean inexpensively and simply improved) to meet the following requirement:
Power a practical vehicle with a single adult passenger, 3000 miles, in 30 days or less while consuming, 50 gallons of pump gasoline or less. This vehicle can not experience any major failures during this journey and all of the fuel and passenger supplies must be loaded on the vehicle from the start. Sounds simple doesn't it? It's not. Many have tried, but no one has yet succeeded. Not even close.
The two (2) stroke power plant in question started out as a promising candidate, however after extensive testing, I discovered the following issues that although correctible individually, represented a sum total of problems that clearly indicated low quality manufacturing and an unacceptable cost of improvement for "my specific" application:
1.)Engine surface machining is extremely poor and engine gasket material of very low quality, resulting in numerous compression leaks. Corrective action required re-machining of cylinder and cylinder head surfaces, and engine case center seal surface, and improved gasket material.
2.)Magneto is of low quality with the windings not properly sealed allowing moisture to corrode and decay windings and welds. This unit is also highly prone to heat damage from extended operating times, (greater than 1 hour at nominal power output). Further, the only alignment provided with this design is a function of the four (4) mounting screws, which can and eventually will allow for contact between the center magnet and the armature as the engine wears (from inherent vibration). A satisfactory correction was not found for this issue.
3.)The sealed and specific ignition module is prone to damage from vibration. Corrective action: shock mounting and modification of spark lead connection to prevent separation with silicone water sealing.
4.)Carburetor is of fair quality, however the choke mechanism can wear and loosen over time, allowing the choke to engage and significantly alter the fuel mixture while operating at nominal power output. Corrective action required a redesign of the choke mechanism.
5.)The entire engine is balanced so poorly as to introduce considerable vibration and loss of overall performance. Correction required extensive internal component modification.
6.)Piston wrist pin clearance is too high allowing for piston slap that will eventually cause engine seizure under load or at high rpm's. See item (5) for corrective action.
7.)Intake and exhaust ports are not properly located in the cylinder allowing for high temperature and/or high rpm pre-ignition. Not correctable without casting a new cylinder and machining for replacement intake and exhaust mounts.
8.)Fly wheel, needle bearing and connecting rod assembly are all prone to oil starvation after extended operating times. Not corrected. Engine candidate abandoned.
Granted, this application is far beyond what normal users will be expecting from this power plant; however, the items described above represent "poor quality control" undeniably and further, represent issues that will affect even the standard user application over time.
In short, all I was trying to say was simply this:
There are better power plants available for a motorized bicycle application, period.
It is possible that the units I received and tested are somehow inferior to the units the vast majority of enthusiasts are obtaining. I doubt this, but even if these units are "defective", the overall design of this engine, from a specific "design perspective" does not lend itself to long term, durable and reliable use in a low maintenance rough duty application of any kind.
Your mileage may vary, and probably will. Again, my intent is not now and was not previously to offend anyone or encourage even the slightest controversy. With this I will close and withdraw from any future forbearance of opinion or thought to this forum.
Thank you for your time, interest and indulgence,
Sincerely, Dr. David A. Gray,
BS IEEE, MBA, Ph.D. Electrical Engineering, Astronomical Physics, Quantum Mechanical Physics
Yes, with the standard 10 tooth front sprocket and a 36 tooth rear sprocket in a single drive ratio configuration, it is not only doubtful that this engine would power any bicycle to over 50 mph, it is not possible. Using a 12 tooth front sprocket and a 32 tooth rear sprocket 50 mph is not only possible, it reduces top end rpm's considerably for nominal power output (average speeds of between 30 and 35 mph). No, I was not abusing this engine, and have actually expended considerable time and effort to improve this power plant to determine if factory modifications would be feasible within the manufacture's cost constraints. Driving the engine at high (not excessive) rpm's for extended periods of time (1 to 2 hours) is part of my test plan to expose possible component failure, e.g. improve durability.
Allow me to introduce myself. Without going into exhaustive details about my education, background or other self indulgent displays of bragging rights, suffice to say that I'm a fairly qualified mechanical engineer. I have earned several graduate degrees in advanced science, have a considerable background in many fields of engineering, and have been modifying internal combustion engines (2 and 4 stroke; considerably bigger and far more complex than this particular power plant) for the better part of 4 decades. Now that, that is out of the way please allow me to explain my previous statements.
I have been searching for a cheap, lightweight, efficient power plant for a specific task. Not finding off the shelf components up to spec., I have been looking for something that can be practically modified (by this I mean inexpensively and simply improved) to meet the following requirement:
Power a practical vehicle with a single adult passenger, 3000 miles, in 30 days or less while consuming, 50 gallons of pump gasoline or less. This vehicle can not experience any major failures during this journey and all of the fuel and passenger supplies must be loaded on the vehicle from the start. Sounds simple doesn't it? It's not. Many have tried, but no one has yet succeeded. Not even close.
The two (2) stroke power plant in question started out as a promising candidate, however after extensive testing, I discovered the following issues that although correctible individually, represented a sum total of problems that clearly indicated low quality manufacturing and an unacceptable cost of improvement for "my specific" application:
1.)Engine surface machining is extremely poor and engine gasket material of very low quality, resulting in numerous compression leaks. Corrective action required re-machining of cylinder and cylinder head surfaces, and engine case center seal surface, and improved gasket material.
2.)Magneto is of low quality with the windings not properly sealed allowing moisture to corrode and decay windings and welds. This unit is also highly prone to heat damage from extended operating times, (greater than 1 hour at nominal power output). Further, the only alignment provided with this design is a function of the four (4) mounting screws, which can and eventually will allow for contact between the center magnet and the armature as the engine wears (from inherent vibration). A satisfactory correction was not found for this issue.
3.)The sealed and specific ignition module is prone to damage from vibration. Corrective action: shock mounting and modification of spark lead connection to prevent separation with silicone water sealing.
4.)Carburetor is of fair quality, however the choke mechanism can wear and loosen over time, allowing the choke to engage and significantly alter the fuel mixture while operating at nominal power output. Corrective action required a redesign of the choke mechanism.
5.)The entire engine is balanced so poorly as to introduce considerable vibration and loss of overall performance. Correction required extensive internal component modification.
6.)Piston wrist pin clearance is too high allowing for piston slap that will eventually cause engine seizure under load or at high rpm's. See item (5) for corrective action.
7.)Intake and exhaust ports are not properly located in the cylinder allowing for high temperature and/or high rpm pre-ignition. Not correctable without casting a new cylinder and machining for replacement intake and exhaust mounts.
8.)Fly wheel, needle bearing and connecting rod assembly are all prone to oil starvation after extended operating times. Not corrected. Engine candidate abandoned.
Granted, this application is far beyond what normal users will be expecting from this power plant; however, the items described above represent "poor quality control" undeniably and further, represent issues that will affect even the standard user application over time.
In short, all I was trying to say was simply this:
There are better power plants available for a motorized bicycle application, period.
It is possible that the units I received and tested are somehow inferior to the units the vast majority of enthusiasts are obtaining. I doubt this, but even if these units are "defective", the overall design of this engine, from a specific "design perspective" does not lend itself to long term, durable and reliable use in a low maintenance rough duty application of any kind.
Your mileage may vary, and probably will. Again, my intent is not now and was not previously to offend anyone or encourage even the slightest controversy. With this I will close and withdraw from any future forbearance of opinion or thought to this forum.
Thank you for your time, interest and indulgence,
Sincerely, Dr. David A. Gray,
BS IEEE, MBA, Ph.D. Electrical Engineering, Astronomical Physics, Quantum Mechanical Physics
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