Start-Up torque

[toastedhead]

Ive got a truck with an automatice transmission. Im trying to figure out how much torque will be delivered to a coupler if I engage the PTO at 800 RPMs.

Im trying to work this out - I dont need to know anything about what Im driving do I? I just need to know the power output of the engine.

The engine is coupled to a Vane Pump by a shaft and TB Woods coupler. I want to know if that coupler will break.

Today is a brain fart day. I dont know whats going on.

 

[eromlignod]

The shaft torque is entirely decided by the load up until you reach the maximum that the motor can produce (hp). An internal combustion engine can't have a locked rotor because it cuts off the supply of fuel and stalls the motor. You can put a big load or a small load; the motor just sucks more gas to maintain the same rpm for the larger load. That's why you have do depress the accelerator more when you go uphill.

The maximum torque that the engine *can* produce is a function of its rpm and horsepower rating. There is a graph of the output torque, which varies with speed for an internal combustion engine. Usually the peak torque is at a fairly high rpm (maybe 5000 or more). I'm talking about the output of the engine at the spline, before the transmission (tachometer reading).

If you can figure out what hp you are running at and convert that to ft-lbs/s (multiply by 550), and you can convert your output rpm (800) to radians-per-second, then the theoretical max. torque (lb-ft) is the power divided by the rotational speed. Since there are losses in the transmission, you will see less torque than this at your coupling. You should still double or triple this figure for a safety factor when sizing your output train.

Don
Kansas City

 

[toastedhead]

Wait, Im trying to figure out start-up torque. Instantaneous.

 

[MikeHalloran]

Depends on the load, e.g. what the vane pump is pushing against.

Easy way; just use a coupling that comes stock with the larger shaft size.



Mike Halloran
Pembroke Pines, FL, USA