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thread on pulling board

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smdv806

12-21-2007 20:05:23




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I would like to see an organized mathematical proof for this.

It was said that a 450 motor put into a M chassis would dyno differently than it would in the 450 chassis because the pto gearing is different? I thought horsepower was horsepower. Someone smart needs to explain this.




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Walter r. Davies

12-22-2007 09:54:18




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 Re: thread on pulling board in reply to smdv806, 12-21-2007 20:05:23  
The gearing from the engine speed to the PTO speed will effect the HP rating. Just like when you shift gears from 1st to 5th you get more HP at the wheels in 1st than you do in 5th.

To get actual engine HP you need to remove the engine and hook direct to the Dyno with no gearing.
Walt



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ChadS

12-22-2007 06:51:25




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 Re: thread on pulling board in reply to smdv806, 12-21-2007 20:05:23  
Simple, take a M, put it on a dyno, add a digital tach or whatever you got,,, set the dyno at 540, then read the rpm. Do the same for the 400-450. Bout 150-200 rpm difference in the engine speed, no matter how it was tuned, the engine speeds were not the same acording to a tach.
Last year, we built a 175 for a 350,,,, I put the engine in a SH chassis, dyno, and it was 47 hp. Took the same engine, dropped it into the 350. The 350 had no live hyd, (removed) dyno hp was 40 hp out of the exact same engine. Rpm was also different, cause the SH ran slower rpm wise then the 350. Its not much of a ratio difference,,, and only an engine tach, and a pto tach will tell what the actual differences would be,, but, there is a difference.
Another exapmle of the ratio chages was the 350 utility rated at over 2200 rpm!! Yet, at 2200+ rpm or whatever they are set at,, the pto is slowed down to make the engine speed faster to run a higher rpm, and still not overspeed the pto. if they left the ratio the same speed as the H and ran the engine at 2200, the pto speed will be over 700 pto rpm. quite a difference in pto rpm speed IF they never chaged anything at all.
Pullers, well they like to brag on how much power an engine makes by itself,,,, and those readings they take are not rated rpm for a tractor. More like high performance race cars,,, where the spin em til they find what they are looking for. Most cases, 500 engine rpm or more over rated rpm to get the big numbers. Our shop, has always pto dyno tuned engines,,, so no matter what,, the power it puts out is rated rpm for that chassis, and its speced out for 540 pto speed for that model. I keep the tractor in the pulling, cause not all pulling tractors, only see track duty, most do both, work and play and they use the pto!
Find a pto tach, an engine tach, and the models mentioned above and do some tests. I did, but you can lead a horse to water, but dont mean, the horse will take a drink. But, we try like heck. Have a good day. ChadS

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RodInNS

12-22-2007 06:13:56




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 Re: thread on pulling board in reply to smdv806, 12-21-2007 20:05:23  
Yes, HP is HP. I didn't read the other thread so I don't know what the arguement was....
but look at it this way. If you're measuring maximum power, the only difference between the chassis's you would see is the difference in parasitic loss from one chassis to another. That's all. If you were talking about power at a certain speed, then there could be differences depending on the PTO gearing from one chassis to the other. If for instance one chassis required an engine RPM of 2500 to get 540 on the PTO, and it's original engine was matched to give maximum power at 2500... that will work. However, if you stick an engine in there that makes it's power at 1800, running it out to 2500 to get 540... it might run out of wind and not have any power.
That's an example of how you can make them TEST different.... but on a simple basis of maximum power at whatever speed maximum power occours, there would probably not be a statistical difference.

Rod

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Lee in Iowa

12-22-2007 06:37:27




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 Re: thread on pulling board in reply to RodInNS, 12-22-2007 06:13:56  
Would there be any difference in the parasitic loss between the two tractors because one is independent pto and one isn't? If there is I don't imagine it would be too much. Lee



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RodInNS

12-22-2007 14:48:17




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 Re: thread on pulling board in reply to Lee in Iowa, 12-22-2007 06:37:27  
Yes, there would no doubt be some difference between an Ind PTO and a dry clutch PTO. The independant PTO has a heavy clutch housing, dragging in oil all the time so it would probably drag a small amount more.
The other factor is the actual gearing that transmits power from the engine to the output shaft. Some tractors have a straight through design in the top shaft of the transmission and then step down at the rear of the tractor. Others step down in the front of the transmission. Perhaps some more are a straight drive from the engine right out the back... but I'm not sure about that. All of those designs will have a varying degree of loss.
As an example, the old Fords would lose probably about 8-10 hp from the engine's gross through to the PTO. The newer, larger tractors would lose closer to 20 through their drivetrain. Two different designs; two differing amounts of parasitic loss.

Rod

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JHH

12-22-2007 04:25:54




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 Re: thread on pulling board in reply to Mark-Mi, 12-21-2007 20:05:23  
Horsepower is a function of speed and torque. Dynos measure torque (although most have a scale calibrated to read hp at a given speed, ie 540 or 1000 rpm). If the speed varies from that which the scale is calibrated it is not accurate and needs to be converted. That being said any engine will make the same hp at any given engine rpm with only very very slight differences for friction because of differences in gear train no mater what chassis it is installed in.

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NIndianaDan

12-22-2007 04:02:33




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 Re: thread on pulling board in reply to smdv806, 12-21-2007 20:05:23  
Motors are designed to make max power at a certain RPM. A 450 motor hooked to a M's pto gearing..... will mean that the 450 motor running at lower speed (to get 540 rpm at the pto)... is probably not running at the 450 motors designed rpm to make max power.



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buickanddeere

12-22-2007 01:55:32




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 Re: thread on pulling board in reply to smdv806, 12-21-2007 20:05:23  
What is crankshaft rpm in a M at 540rpm pto? What is crankshaft rpm in a 450 at 540 rpm pto?



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Bill(Wis)

12-22-2007 05:26:27




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 Re: thread on pulling board in reply to buickanddeere, 12-22-2007 01:55:32  
The Farmall M with gasoline engine and the Farmall 450 Diesel were both rated at 1450 Engine RPM and 540 PTO RPM.



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RobMD

12-21-2007 20:35:58




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 Re: thread on pulling board in reply to smdv806, 12-21-2007 20:05:23  
Here is my guess... what's the max speed for the farmall M? something on the order of 1800 rpms?? if so, putting a 2100 rpm 450 engine in a farmall M might mean that the 540 rpm pto will be exceeded when going 2100 rpm. The 450 was geared so that full power at 2100 rpm occured at 540 rpms?

I don't really know the max rpms of both tractors, but that's my point, max engine speed for power take off could vary.

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RustyFarmall

12-21-2007 20:29:48




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 Re: thread on pulling board in reply to smdv806, 12-21-2007 20:05:23  
Might be a little bit of difference, but not enough to make you or break you. If there is any difference, the 450 engine in the M chassis should put out slightly more HP because you don't have the drag of the hydraulic pump.



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in-too-deep

12-21-2007 20:20:35




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 Re: thread on pulling board in reply to smdv806, 12-21-2007 20:05:23  
How could it be geared different? No matter how you slice it, approx. 2100 RPM is going to be geared down to approx. 540 RPM. It may take more gears in a 450 or M, but not enough to create enough drag to make it dyno different. If it had a hydraulic-driven PTO that'd be different, but it doesn't, so it isn't. I dunno. I think a little pride is coming into play with statement.



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