[AT] tractor hydraulic pressure measuring? Dean

[Cecil R Bearden]

The early tractor's relief valve was replaced with the later relief 
valve with no problems.  I cannot find a reference to the pressure of 
the to-35 pressure, but the MF-35 was 2800 .  The valve was usually 
referred to 2750.  This seems to be correct in my memory of working on 
the early Ferguson and fords.   I spent a lot of hours in a tractor shop 
working on the hydraulics.   I would suggest looking to see if you have 
a control valve that has another relief in it that could be allowing the 
oil to bypass the control and go back to sump when you load it above 
1750 psi.

Early loaders had about a 2 in diameter piston in the cylinder and the 
cylinder operated at a 45 deg angle usually.   If you work on the 300 
psi difference, and take the area of the piston, it figures out to 1884 
lbs of thrust combined.  At a 45 degree angle, this would be the cosine 
of 45 (.707) x 1884 = 1331 lbs to raise a load.  This is about 1/2 yd of 
sand, and that is about what the old tractors would handle.    It sounds 
ok to me......   A large round bale or hay would be nearly flatten the 
early tires. The rear tires would have to be ballasted and then put a 
box blade on the rear also.

I am sure someone will try to  shoot holes in my figures, but it is a 
close approximation.
Cecil in OKla



On 5/22/2012 10:05 PM, Len Rugen wrote:
> On 5/22/2012 9:44 PM, Steve W. wrote:
>> John Wilkens wrote:
>>> Dean, i installed a good gauge in the pressure line and set the
>>> bucket under a heavy (too heavy) load and got a reading of 1800
>>> psi.  The empty bucket alone takes 1500 psi to lift.  This is a
>>> smallish tractor (TO 35) but doesn't 1800 lbs lift maximum seem a
>>> little woosey?    John W.
>>>
>> 1800 psi seems low for a relief pressure.
>>
>> That number is NOT the same as maximum lift though. The only real way to
>> get that number would be to measure it directly with a scale.
>>
>> That is because although you could set down and calculate out the load
>> using the psi number you also need to add in the piston diameter,
>> cylinder angle, amount of leverage that the loader has based on the
>> pivot angles of the cylinder against the pivot of the loader boom,
>> friction losses, plus a few more things.
> Well, when I saw 1800 I thought that was the working pressure for that
> age of equipment, now you have confused me :-)  My  Bush Hog M246 loader
> is only rated to lift about 1700 lbs.
>
> I would guess that this tractor would be limited by the front spindles
> and axle capacity, lots of that age stuff was broken up with heavy
> loader use.
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