Small 4-stroke, cordless drill gearbox, flywheel

In summary, the conversation discusses the suitability of using a gearbox from a cordless or wired drill for a small 4-stroke engine with a maximum power of 750 watts. It is suggested that a gearbox from a 3000 watt electrical tool may be needed, and the effect of flywheel mass is also considered. The application for this setup is for a bicycle, with a specific terrain and power requirements. Concerns about the durability of the gearbox and the accuracy of calculations based on the bicycle wheel's measurement are also mentioned.
  • #1
thorpie
15
0
I would like to know whether a gearbox (reducer) designed for an electric motor is suitable for the same powered 4-stroke engine.
The most common, and therefore inexpensive, gearboxes are on drills, either cordless or wired.
A small 4 stroke engine gives a maximum power of 750 watts. Would a gearbox off a 750 watt drill be suitable? or does the 4 stroke engine only powering 1/4 of the time mean that a gearbox off a 3000 watt electrical tool is needed?
I also assume that the flywheel mass will have some effect on this, could anyone explain what effect the flywheel mass would have?
Literature on cordless drills don't generally show a wattage, for the larger ones a torque of 30 nm is shown. The small 1 hp (750 watt) 4-strokes have a maximum torque of 1 nm. As I am seeking a reduction of 27:1, which would give an output torque of 26 nm, I was wondering whether these gearboxes would be OK
Many Thanks
 
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  • #2
What is your application?
 
  • #3
Bicycle, but I am aiming at the best assistance possible from 1 litre of fuel over 1,000 km. I need the right terrain, with just 2 gradients, 0.8% downhilll (unpowered, 90% of the time) and 5% uphill (powered, 10% of the time). With the right terrain this provides a constant speed of 21 km/hr, so the engine has increased the speed from 16 km/hr to 21 km/hr and overcome the tyranny of hills.
I am also having trouble identifying a jump start clutch at the back wheel - I can't afford to consistently lose the energy driving a chain and half a clutch away from the bike hub. The average assistance provided is only 40 watts, so a loss of 10 watts is huge, a loss of 20 watts means you may as well not bother with the engine!
 
  • #4
Just double check the speeds that both are required to run at.
 
  • #5
Engine at 4500 - 5000 rpm (BSFC of 408 g/litre). 26" external diameter bicycle wheel at 168.7 rpm gives 21 km/hr. Reduction needed 26.7:1.
I can get 2.5:1 from the chain drive, if necessary. So I need somewhere in the range 11:1 to 27:1 from the gearbox. Single stage planetary's go up to 12:1, unsure what they are in drills.
 
  • #6
thorpie said:
I also assume that the flywheel mass will have some effect on this, could anyone explain what effect the flywheel mass would have?

From a practical standpoint, the flywheel dampens the power pulses. Kind of a "shock absorber" between the crankshaft and gears.
 
  • #7
Just a thought... a gearbox from a drill is likely not rated for continuous maximum force. You might want to include a healthy safety factor into your working load.
 
  • #8
thorpie said:
Engine at 4500 - 5000 rpm (BSFC of 408 g/litre). 26" external diameter bicycle wheel at 168.7 rpm gives 21 km/hr. Reduction needed 26.7:1.
I can get 2.5:1 from the chain drive, if necessary. So I need somewhere in the range 11:1 to 27:1 from the gearbox. Single stage planetary's go up to 12:1, unsure what they are in drills.
You may want to measure the bicycle wheel, the measurement on the sidewall doesn't usually reflect the actual diameter of a complete wheel. I just thought I'd point that out because that would greatly effect your calculations.
 

1. What is a small 4-stroke engine?

A small 4-stroke engine is a type of internal combustion engine that operates on a four-stroke cycle, which involves four distinct processes (intake, compression, power, and exhaust) to convert fuel into power. These engines are commonly used in lawn mowers, generators, and other small machines.

2. How does a cordless drill gearbox work?

A cordless drill gearbox is a mechanical device that uses a series of gears to transmit and control power from the drill's motor to the chuck. When the trigger is pulled, the motor rotates a small gear that meshes with a larger gear, transferring power and increasing torque. The gears continue to rotate until the desired speed is achieved.

3. What is the purpose of a flywheel in a cordless drill gearbox?

A flywheel is a heavy, rotating wheel that is used to store and release energy in a cordless drill gearbox. It helps to maintain a constant speed and absorb sudden changes in torque, providing a more stable and smooth operation. The flywheel also helps to extend the life of the gearbox by reducing wear and tear on the gears.

4. Can a cordless drill gearbox be repaired?

In most cases, a cordless drill gearbox can be repaired. It is important to properly diagnose the issue and determine if it is a problem with the gears, bearings, or other components. If the gears are damaged, they can be replaced, but if the gearbox is severely damaged, it may need to be replaced entirely.

5. Are there any maintenance tips for a small 4-stroke engine with a cordless drill gearbox?

Yes, there are a few maintenance tips for a small 4-stroke engine with a cordless drill gearbox. Regularly check and change the oil, clean or replace the air filter, and inspect and tighten any loose bolts or screws. It is also important to store the drill in a dry place and avoid exposing it to extreme temperatures or moisture.

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