Another Knucklehead, built via castings, as a Draw-Tech design, upscaled

[mayhugh1]

The electric motor that I installed cannot rotate the crankshaft.
I was hoping that by powering it with 24 Volts it could start the engine, but a higher reduction ratio is needed.
I am waiting to receive a planetary gearbox to increase the torque, in the next few weeks I hope to start the Knucklehead via an electric button.

I'm surprised your motor with the 3:1 belt reduction didn't make enough torque to turn the engine over especially at 24 volts where you should have seen 30 kg-cm at the crankshaft. Are you sure the limitation wasn't your battery or the gage of the wiring or the contact resistance of the relay (or switch)? Make sure to verify the voltage at the motor's terminals as well as the motor current if at all possible. - Terry

 

[Foketry]

I'm surprised your motor with the 3:1 belt reduction didn't make enough torque to turn the engine over especially at 24 volts where you should have seen 30 kg-cm at the crankshaft. Are you sure the limitation wasn't your battery or the gage of the wiring or the contact resistance of the relay (or switch)? Make sure to verify the voltage at the motor's terminals as well as the motor current if at all possible. - Terry

I checked again with a cordless drill battery, 18 Volt, 10 A and electrical cables of adequate section but the engine does not turn.
When the piston reaches the TDC in the compression phase it does not have the strength to overcome that point. My Knucklehead has a compression ratio 10:1( effective) , the piston diameter is 36 mm (1.4 inches)
I purchased a 19:1 planetary gearbox, similar to that of cordless drills , should be the right solution.
This should allow me to use the same battery as my cordless Bosch and not have to carry around 2 heavy and bulky 12 volt lead acid batteries.
I don't have a torque meter to measure how much torque is needed, I'm just trying.

 

[Vietti]

FWIW-I built a modified Hoglet and found that my usual electric starter motor would not turn it at a 4:1 ratio. I ended up finding a larger motor. The Hoglet has a smaller bore and a lower compression ratio too.

Look forward to your experience with a planetary gearbox solution!

 

[mayhugh1]

I checked again with a cordless drill battery, 18 Volt, 10 A and electrical cables of adequate section but the engine does not turn.
When the piston reaches the TDC in the compression phase it does not have the strength to overcome that point. My Knucklehead has a compression ratio 10:1( effective) , the piston diameter is 36 mm (1.4 inches)
I purchased a 19:1 planetary gearbox, similar to that of cordless drills , should be the right solution.
This should allow me to use the same battery as my cordless Bosch and not have to carry around 2 heavy and bulky 12 volt lead acid batteries.
I don't have a torque meter to measure how much torque is needed, I'm just trying.

I think it would fine from a single 12V lead acid battery using the proper heavy gage wiring. I'm talking about one of those little 9 amp-hour batteries commonly used in UPS's. You can hold them in one hand and will deliver up to 40 amps for a short time if your starter wiring is heavy enough (use short lengths of 12 gage stranded silicone wire).

https://www.amazon.com/Mighty-Max-B...2011&s=electronics&sprefix=ups+battery&sr=1-2


https://www.amazon.com/BNTECHGO-Sil...ix=stranded+silicone+wire,aps,153&sr=8-5&th=1


Terry

 

[Vietti]

That's the wire I used and it is very nice.