Three-Point Hitch Question

[Roy]

Observed something about my 3-pt the other day. While being raised, a force is applied (of course, no surprises there), but when lowering, no force is applied (simply limits the speed of the ascent, but does not apply any force the downward movement). My question, is this the way all tractor 3-point hydraulics work?

I just always assumed that there was some residual force applied. Now, I can understand why no downward pressure is exerted (unlike a FEL, where it is required), but at the same time it amazes me that ground-breaking implements (tillers, plows, sub-soilers) work so well.


Roy

 

[Billc]

Roy, there are some that do have downward presure, but don't know the names. Most don't have downward pressure.

When I use my disc or plug aerator I have to stack rocks on top of the implement to get some down pressure.

Bill Cook

 

[AndyR]

Roy, As Bill pointed out, many attachments make use of additional weights for down pressure. On a compact tractor you need to be espcially aware of your lifting capacities - it's not just an issue of the total weight but the moment arm(physics class!/w3tcompact/icons/tongue.gif ) . In other words, if I have a scarifier AND a York rake attached behind it I need to figure the weight of each and multiply the weight of the york rake (assuming rigid attachment) by the distance. Just like a big lever trying to lift the front of your tracor and bend your rear axle at the same time. Don't panic, just do the math.

As for down pressure, my old Farmall Super-C has an aftermarket 3ph that is driven by the rockshafts forward of the operator. The manuals point out that you can change a rear tire by using the down-pressure to lift the tractor and then blocking it. Nice feature but it can be hazardous if you don't pay attention.

"Beer is proof that God loves us and wants us to be happy." - Ben Franklin

 

[Thomas]

Gravity consider your down ward pressure,and if you notice on a cold day and the hydraulic fluid not up to temp yet raising attachment seem to take longer than on a warm summer day on a cold start.
The lenght of the attachment from the 3pt hitch also play a part on how fast the attachment lower its self.

I guess by now your spring raking just about done and mowing just around the corner...still have 9'foot snow banks up here in the pucker brush. /w3tcompact/icons/crazy.gif


Thomas..NH /w3tcompact/icons/wink.gif

 

[TraderMark]

Roy,
Most tillage implements are designed to pull themselves into the ground. The angle of ground contact and the shape of the plow itself is made to pull the plow deeper. The 3pt hitch's job is to hold it up and not let it go too deep. Look at a turnplow or a susoiler or a cultivator and look at the angle where the plow contacts the soil and you'll see what I mean. Also, the top link adjustment helps to make the implement more or less aggressive. Usually.... shortening the top link points the implement tip downward more, making it more aggressive and lengthening the top link lets the implement rest more on its "heel" and be less aggressive.
Hope that makes sense./w3tcompact/icons/laugh.gif

 

[Roy]

Thanks to all. I do understand, it just amazes me. But I guess that it really shouldn't, since the basic tools (like plows) were all originally designed to work by horse/oxen draw.

AndyR; You pointed out something about the Farmall that was on my mind at the time I was posting the original question. Gee.. wouldn't it be nice if the back could be raised to change a tire or attach chains (without a backhoe) like the FEL can be used for the front end.


Roy