Author Topic: Serco 8000 PTO Rating (Read 950 times)

appalachianlggr · « **on:** July 24, 2018, 01:22:08 PM »

Hello all,

This is my first post on this forum and I thought somebody might have knowledge on some self-loader information I'm trying to figure out. I paired a 1984 Western Star (w/ 3406B CAT motor) to a 2004 Serco 8000 knuckle-boom loader and wanted to know what the horsepower rating might be for the Power Take Off and hydraulic pump.

The truck has a 13-speed Eaton Fuller Road ranger with a cable type PTO. Is there even a horsepower rating for these loaders and pump? I'm just trying to make sure the PTO I have is good for the hydraulic pump I'm using to power the loader. The guy I bought the truck off of and the guy I bought the loader off of seem to think it will be just fine. I was told to lock the throttle at about 1200RPM and should be good!! Being new to self-loading trucks I need educated. Any help would be appreciated. Thank you.

Firewoodjoe · « **Reply #1 on:** July 24, 2018, 08:32:50 PM »

It shouldn’t make any differance. There’s reliefs on the valve bank for power. Your just basically giving speed to the pump. 1200 may be high. Our sercos are high volume pumps and run 900. Most guys bump to 1000. Good luck.

2308500 · « **Reply #2 on:** July 24, 2018, 09:25:16 PM »

we run a bigger chelsea pto than the common size. almost triple the money but built to take the torque. the bearings do not last in the smaller series. we had one go after 10 months and take a trans out (ouch). horsepower rating on the serco 8500 which we run can be in the high 60 to 70 range under full load. i believe ours is running at 117%overdrive on an 18 speed 500 cummins,

if you try to overdrive them too much, under constant working conditions, the engine fights too much to try to maintain rpm and engine speed bounces from too slow to too high (400 rpm range)when we first tried about 130 percent. for moderate use the smaller series will do fine but on a high use unit i wouldnt risk it

Firewoodjoe · « **Reply #3 on:** July 25, 2018, 04:47:53 AM »

That’s what we have are 8500 and a lot of guys are going 1050. I’ve never heard of a hp rating. Interesting. Our engines are 550hp 18 speed. We’ve also never had a pto take out a tranny but always put new ptos on when a tranny goes. Pto being on the bottom gets all the metal.

2308500 · « **Reply #4 on:** July 25, 2018, 06:26:05 AM »

bearings go in the pto then the grit gets spread throughout the transmission. saw it firsthand this spring. pulled all the rollers (all mostly intact) out of trans with a magnet. flushed with oil then filled with new synthetic and new pto. got lucky on that one

2308500 · « **Reply #5 on:** July 25, 2018, 06:27:25 AM »

if you look into the chelsea pto catalog there are recommended horsepower ratings

appalachianlggr · « **Reply #6 on:** July 28, 2018, 12:56:38 PM »

Thanks for your input. I'll definitely see how she runs at around 900rpm's before I bump up. I would like to think that could save some on fuel too. Can you explain what do you mean when you say yours is running at 117% overdrive on an 18 speed 500 cummins? Also, how would you know what series/size PTO you would have.

appalachianlggr · « **Reply #7 on:** July 28, 2018, 01:01:19 PM »

If I understand correctly it's the percentage of what the engine speed possibly?

mike_belben · « **Reply #8 on:** July 30, 2018, 11:15:53 AM »

I dont have eatons spread sheet anymore but most trans have a PTO speed of like 70-80% of input shaft speed/engine rpm. Then youd have to look at the pto mfr rating as to if its 1:1 or .9 or 1.2 etc of pto shaft speed.

Figuring power available to the loader would be a chore. Youd have to see what your engine makes at the RPM you are running. The pto being gear drive is gonna transfer probably 99% of that engine energy to the fluid but the hydraulic system is gonna drop quite a bit of power as heat. New tight pump/motor pairs will be around 80% efficient so youd have a wildcard there. Old can be 60% efficient and the rest leaking thru case drains back to tank.

And it all really doesnt matter too much. Custom rigging hydraulics is a trial and error game that the manufacturer does for you if you buy new, or you do for you when piece mealing stuff together. If you set up your loader and its not fast enough you need more flow, raise the rpm. If doing this makes the engine hunt on the governor, your pumps cubic displacement is too large for the pressure that your relief valve is calling for. Basically the load is demanding more Input HP than the engine makes at that rpm so it lugs down and the governor says hey, we need more fuel to maintain set rpm.

A big pump is like 2.90 rears in a offroad truck when you need 4.11s. Stepping down on the pump's displacement will spread the work over more pistons and reduce the load, like going to deeper gears. Youd just raise the idle speed until you found the right flow for the new pump that doesnt make the governor hunt around. Lowering pressure is probably not an option but it would also reduce input power demands and smoothen out the rpm.

Regarding fuel consumption, i dont care what anyone or any rpm chart says. You will get lowest brake specific fuel consumption at the lowest EGT and boost that you can make this thing work at. Lugging down engine at low speed always runs hotter than letting it rev higher and running less load on each power cycle. Rpm spreads the load across more strokes, like having 50 friends help carry the couch instead of two. I can hit 1300F+ if i dont drop gears on my biggest climbs. I can climb that same hill in the middle of cooking summer day fully loaded at 850 EGT by never letting boost break 15psi.. Just keep dropping gears and tolerate running slower until i crest the top, nice and cool. High rpm, low load. This also generates lots of fan speed and coolant flow with less heat input to the water jacket. Heat is the devil of all industrial process.

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