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power take off system of engine

power take off system of engine

power take off system of engine

I am new to automobile engineering. Currently I am dealing with engine manufacturing company to procure some engine for our forklifts . To operate the hydraulics of engine, sometimes we use PTO mounted on engine and sometimes we go for PTO mounted on transmission.
As per our forklift specification we need to have 40 hp PTO output to run our auxiliary system. When I emailed our requirement to engine manufacturing company,engineer there replied to me "The engine has limitation in accommodating hydraulic pump in the provision of timing case for PTO. The maximum design power of engine mounted PTO cannot exceed 25 HP"
My first question is
1)what does it mean by "limitation in accommodating hydraulic pump in the provision of timing case for PTO"
2)what engine data I need to calculate PTO hp of engine?
3)Can the engine output hp and engine PTO output hp, be same?
4)What difference it makes if I use engine PTO to drive auxiliary system vs transmission mounted PTO to drive auxiliary system?

Thank you in advance for answering bunch of questions.

RE: power take off system of engine

You don't need to calculate anything; you got an answer from the engine engineer; you can't pull 40HP out of the PTO you asked about. You need to ask a similar question of the transmission manufacturer.

Can you mount two 20HP pumps on two PTO ports on the engine? That's another option, if you can get the engine built that way, and the PTO drive is sturdy enough.

At one former employer, our sales wizards sold an assembly with a clutch coupled to the harmonic damper, and advertised it as capable of 350 HP, because that's what the clutch assembly was rated for, when mounted to the engine bellhousing. Unfortunately, the drive key on the front of the engine crank was only capable of 75HP at 1800rpm, so that's what the accessory adapter should have been rated at. It also made changing the fan belt a super bitch of a job, until I inserted a chain coupling in the assembly.

Basically, you need to get as much documentation as you can about the engine you're using, read it thoroughly, and then get on the phone with the engine engineer who answered you, to explore ways (s)he can help you solve your problem. Follow up with email so you'll have a record, but work together by phone to develop a solution.

Mike Halloran
Pembroke Pines, FL, USA

RE: power take off system of engine

Hello Mike,
Thank you very much for answering in both the threads. Well, I understand engine engineers's remark that I can't pull the 40 HP from the PTO. But I want to understand his technical remark ''provision of timing case for PTO''.
The engine is very compact for small size forklifts, and they offered the solution of front pulley mounted PTO if we want to pull 40 HP, but we are not willing to go for this solution.
In the second question, it was just for the sake of knowledge I would like to know if I have basic engine data. eg. rpm, power, torque. What other data I need to calculate PTO HP.
And I would be really glad if you can tell me something about 3 & 4.

RE: power take off system of engine

3) In general, no, because the primary drive flange at the bellhousing end of the engine is MUCH sturdier than the camshaft drive or the harmonic damper drive.

At the same former employer noted above, a customer wanted a simple belt drive for his hydraulic pump. A different wizard salesman didn't quite understand that, and bought an expensive OEM pump drive that took power off the camshaft gear through a window in the timing cover provided for that purpose. The customer didn't like it because it didn't have a way to declutch the pump, so we got to uninstall the gear drive, and install a third party belt drive that was declutched from the harmonic damper by displacing an idler to loosen the belt with a simple lever. We ate the cost of the gear drive, and the labor to install and remove it.

4) Engine PTO drives are usually always ON, whereas transmission PTO drives commonly have some kind of in/out arrangement that can declutch the driven unit at reasonable speed, and can be re-engaged with the engine stopped. For a forklift, you may not want to declutch the pump, ever, but _somebody_ has to check the life of all the associated bearings and gears that you will be spinning.

Equations and calculator for rpm/torque/HP can be found at:
... and a bazillion other pages.

Mike Halloran
Pembroke Pines, FL, USA

RE: power take off system of engine

Thank you, Mike, That helps lot.

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