PTO HP in different ranges.

[F15DOWNER]

Hi
I just purchased a generator head that I would like to run with my tractor. The gen head needs to turn at 1800 RPM. Does it make a difference in PTO HP within the 3 ranges?
I don't want to set it up at a 2:1 ratio in range 2 and not have enough power to run it.

Question 2
At what Engine RPM do you reach the rated PTO speed?

Thanks
Tom

 

[Mickey_Fx]

Sure would have helped if you had given some important info. What size generator? What model tractor?

Generator size will determine how much power is needed to produce full A.C. power. Tractor model number will tell us how much power you have available and potentially what PTO gear range you need to produce adequate power and adequate speed.

 

[SATOHBULL]

The HP is the same at all speeds. HP is just torque applied over time. As the speed increases the torque will decrease but HP stays the same. Well, there might be some frictional loses, but not much.

All the compact diesels I've looked at develop rated pto speeds between 2000 and 2600 RPM. As the earlier responder mentioned, with your tractor info you can get a much more accurate answer.

 

[roxynoodle]

His user name says FX15D owner. On my 1510 first speed on the PTO generates 540 at 2200 rpm. On speed 2 it generates 1000 at the PTO. My owner's manual says that the third PTO speed will be whatever the engine speed is (must be a straight 1:1 gear ratio). So based on that I would think use 3rd speed on the PTO and set engine throttle at 1800rpm? I don't know that your PTO is set up the same as mine though.

 

[Tom_Veatch]

...
So based on that I would think use 3rd speed on the PTO and set engine throttle at 1800rpm? I don't know that your PTO is set up the same as mine though.

Those PTO speeds match what's stated in the manual for my 2220D and occur at about 2250 engine rpm.

If F15DOWNER is going to direct drive the generator head, the 3rd Range 1800 RPM option is probably the best, if not the only, option. To get 1800 at the PTO in either 1st or 2nd PTO Range, the engine would have to be run well above redline. He could also get there in Range 4, if he has it, which, according to my manual, is "slightly overdrive".

But, there is the question of power available at the 1800 RPM speed. The engine develops peak power at a specific rpm. The power developed at any other speed will be less. I suspect that the PTO gearing is designed (or should be) to run the PTO at it's standard rpm (540, 1000, etc.) with the engine at, or near, it's peak power RPM. Running at 1800 RPM may reduce the amount of power available below what F15DOWNER is expecting.

My recommendation would be to insert step-up gearing ahead of the gen head and step the PTO rpm up from either 540 or 1000 to the needed 1800 at the generator. Then he could run the tractor at the (assumed) best power RPM of the tractor and get the speed he needs at the generator with the maximum available power.

 

[F15DOWNER]

Sorry for the confusion. The model is F15D which is around 18HP according to Hoye's web site, which I have great confidence is right.
The generator is a 10K.
My PTO is three speed, 600, 916, 1200 roughly
My plan was not to run it direct, but a 2:1 or 3:1 or something in between, ratio depending on the outcome of this conversation.

After hearing what I have so far I think I will run 916 PTO speed and select a ratio that will give me 1800 RPM at about 2200 engine RPM which should be real close to 2:1.

I know that 10K is pushing it on HP, that is why I'm doing my homework, with the people that I am very confident that know.

I would rather have a generator that runs under the rated output with this tractor so when I upgrade the tractor sometime in the future it will be just right. (hopefully soon)

Thanks for the reply's so far and if anybody else has any input I will be very grateful.

Where are you soundguy? I always look forward to your input.

Thanks again
Tom

 

[Tom_Veatch]

...
After hearing what I have so far I think I will run 916 PTO speed and select a ratio that will give me 1800 RPM at about 2200 engine RPM which should be real close to 2:1.
...

Sounds like a plan to me. Should get you real close, and you can fine tune operating speeds using the generator meter(s) and the tractor throttle.

The "book" says about 1/2 KW per HP. That's a rule of thumb to take into account inefficiences in converting the tractor power to electrical power. Depending on the efficiencies (or lack thereof) in your particular setup you may do better than that - or you may do worse. But I don't think an 18 PTO HP tractor is terribly mismatched to a 10KVA generator. If you find it bogging your tractor down, you can always turn off a light or two, sequence or schedule the loads, etc.

 

[kenmac]

Is your genset 10k running or surge ? the rule of thumb is 2 engine hp per gen kw.so you'er close on engine hp. Just my opinion but, I think hp still makes a difference even with 3 ranges. When you start to load the gen is when you will need the hp.I think you will do ok you'er only 2 hp off .Not ideal but, should work.

 

[Cord]

If he uses a belt drive, he'll proably loose more than 2hp in it. My pto tops out at 1200rpm, so if he can truly hit 1800 in high, then that would be his most efficient speed.

 

[normde2001]

Sorry for the confusion. The model is F15D which is around 18HP according to Hoye's web site, which I have great confidence is right.
The generator is a 10K.
My PTO is three speed, 600, 916, 1200 roughly
My plan was not to run it direct, but a 2:1 or 3:1 or something in between, ratio depending on the outcome of this conversation.

After hearing what I have so far I think I will run 916 PTO speed and select a ratio that will give me 1800 RPM at about 2200 engine RPM which should be real close to 2:1.

I know that 10K is pushing it on HP, that is why I'm doing my homework, with the people that I am very confident that know.

I would rather have a generator that runs under the rated output with this tractor so when I upgrade the tractor sometime in the future it will be just right. (hopefully soon)

Thanks for the reply's so far and if anybody else has any input I will be very grateful.

Where are you soundguy? I always look forward to your input.

Thanks again
Tom

You will only have pto, (15), hp available to run the generator, giving an effective 7.5kw. If it's just a bare head, connection and gearing should be a real challenge.

 

[F15DOWNER]

You will only have pto, (15), hp available to run the generator, giving an effective 7.5kw. If it's just a bare head, connection and gearing should be a real challenge.

Norm
It is a bare head.
I work in a 500 machine, machine shop, I have 300+ straight cut gears to choose from, from an old automatic screw machine that we scrapped to achieve the ratio.
My plan was to fab a countershaft using pillow blocks and 2" square tubing, mounting the entire thing to and old dirt scoop frame. I found a PTO adapter at TSC that I'm going to bore out to the counter shaft size and have one of my guy's at work broach a keyway into.
I will probably loose some HP through the gearing, but I don't need to power a city. All I need is a backup that is capable of running a well pump, furnace blower motor, TV and a couple of lights.
I live in a very rural part of northeast Ohio and when the power goes out, they generally aren't in much of a hurry to get us back on line because of the number of people affected. So normally our power is out up to 5 hours at a time.
I probably could use a small gas generator, but I got a very good deal on this head. It cost less than a small generator 4KW and all of the parts to make the rest were picked out of the scrap pile.
Thanks all!
Tom

 

[Jagmandave]

I think a flywheel would help with the load/unload response, wouldn't it?

If you're gearing up (from 900 on the tractor PTO to 1800 at the genset) it affects torque and HP too, doesn't it? It's like trying to run up a hill in 4th gear vs 2nd............

 

[Mickey_Fx]

Tom, it sounds like you could get by with about 5kW power output or a little less. I've used my RV genset, 4kW to run the house, 1HP well pump, several refrigeration units and a few lights without difficulty.

For Yanmar first 2 digits on model number represents PTO hp.

May I suggest you give thought to not using gears and go with a belt drive. Not much diff in efficiency and most likely going to be a lot quieter. Additionally since you are not going to be taxing the generator too hard with stated loads, you have the option to "gear" the drive so engine doesn't have to run near full speed. At a latter date if load demand changes or you get another tractor, a belt drive would be easy to change drive ratios to occomodate changing conditions.

I have sim plans for a generator but was thinking of 7.5kW size. Was going to drive the unit so engine would only turn about 1200 rpm but I'm also starting out with a larger tractor and smaller generator.

 

[F15DOWNER]

Update
I traded for a 7.5KW unit. It should provide all the power I need and should fit the HP of the tractor better.
I took the advice of belt driving it.
All I have to do is build the drive unit.
I have attached my plans, anyone see any problems?
Tom

 

[Soundguy]

If you are running near rated hp / rpm.. and you do have 18 pto hp available.. then in idal terms.. you can get about 9kw out of the head. That will be reduced depending ont he connection method. as was mentioned.. belts will loose the most.. gear driving/ gearbox, the least.

In any case.. looks like you may squeeze 7-9kw out of the head, depending on how you go about it..

I think your plan with the smaller head is pretty good. One question though. Do you plan to add a front shaft support to help with the shaft side load o fthe belt on the genny shaft? Thus having hte genny pully supported on both sides of the pulley?

Soundguy

Sorry for the confusion. The model is F15D which is around 18HP according to Hoye's web site, which I have great confidence is right.
The generator is a 10K.
My PTO is three speed, 600, 916, 1200 roughly
My plan was not to run it direct, but a 2:1 or 3:1 or something in between, ratio depending on the outcome of this conversation.

After hearing what I have so far I think I will run 916 PTO speed and select a ratio that will give me 1800 RPM at about 2200 engine RPM which should be real close to 2:1.

I know that 10K is pushing it on HP, that is why I'm doing my homework, with the people that I am very confident that know.

I would rather have a generator that runs under the rated output with this tractor so when I upgrade the tractor sometime in the future it will be just right. (hopefully soon)

Thanks for the reply's so far and if anybody else has any input I will be very grateful.

Where are you soundguy? I always look forward to your input.

Thanks again
Tom

 

[F15DOWNER]

I thought about supporting the Gen shaft and I have a plan to do it, if I need to.
The shaft size is 38MM (1.496") and the front bearing is very stout, so I was hoping to get away with not doing it.
This generator is a tank. It's all cast iron, with roller bearings.
I have Applied, quoting me 2 38MM pillow blocks today, the only problem is the input shaft is kind of short, to get one on the outboard side.
Thanks
Tom

If you are running near rated hp / rpm.. and you do have 18 pto hp available.. then in idal terms.. you can get about 9kw out of the head. That will be reduced depending ont he connection method. as was mentioned.. belts will loose the most.. gear driving/ gearbox, the least.

In any case.. looks like you may squeeze 7-9kw out of the head, depending on how you go about it..

I think your plan with the smaller head is pretty good. One question though. Do you plan to add a front shaft support to help with the shaft side load o fthe belt on the genny shaft? Thus having hte genny pully supported on both sides of the pulley?

Soundguy

 

[Soundguy]

Your choice of course.. but I've seen bearing failures in side loaded belt driven apps i fthe belt tension is too high.

For limited use.. it may not be a concern.

Soundguy

 

[California]

I'm just thinking about the theoretical here - I think the reason some larger US tractors have a 1,000 rpm pto is to tradeoff a higher pto rpm for lower torque transmitted. I assume that improves reliability.

This same reasoning might apply here. Running your pto at intermediate speed is going to require a robust step-up belt system to drive a tiny pulley from a large one. But if you use the pto's highest gear then the pulleys will be similar (3:2), and at the higher driveshaft rpm there will be less torque stress to design for in building the coupling, and also the mounting.

Is there a Mechanical Engineer in the audience?