Hydraulic Delay on Belly Pump

Posted by Andy Martin on December 21, 2004 at 06:09:41 from (64.219.39.195):

The right port and left front are controlled by the same ball check valve. The left rear is controlled by a different ball check valve. When you try to lower a cylinder, the toggle lever which depresses the rods to lift these balls will always lift the R-LF ball first. You have to push a little harder to lift the LR ball. So what someone referred to as a "sticky" spot at the bottom is the second ball being lifted to lower the rear cultivator.

Whoever was letting down the right side only had the hoses hooked up wrong. Both front sides should have been on the front ports and the rear should be on the rear left port. Then as you enter the row you can let down the lever to lower the front and push it down to lower the rear at the proper time.

When mowing with a haybine I've noticed that sometimes the cylinder will come down until it stops, but the valve is not held open like you'd expect so if the tractor goes over a terrace the header will follow the tongue instead of the ground. To avoid this happening you have to give the lever the extra push. Sometimes this is hard to do. Inspecting a Lift-All last night I realized with the left rear port plugged it can trap oil under pressure and make it difficult to get the lever fully down because you are pushing against the ball (with pressure behind it) with less mechanical advantage than you have with the other ball. I've tried to use this "hold in position" to let a disk down without returning the hand lever to the stop but have not had any luck with the Liftall holding position like it does if you pull the lever back out part ways to the stop.

The hand lever has a lot better leverage on the R-LF ball valve than it does on the LR. The R-LF ball is right under the pivot on the toggle so it gets relieved as soon as you push the lever. The LR ball, lower in the pump housing, does not get depressed until the toggle has contacted the housing on the other end. The spring on the LR is also stiffer than the spring on the R-LF which also assists in only relieving pressure on the R-LF first.

So the unit is truly designed to let the front of a cultivator down first and the extra push will let the rear down, if it is plumbed correctly.

I have not studied the internals for one, but I also bet there is a shuttle which directs oil to the R-LF first and then to the LR after some pressure is developed by the front rams bottoming out. You probably could not detect this using two pressure gauges because they would probably stroke too closely together. I guess I'll have to hook up two cylinders to the two left ports and see if the front port cylinder comes out first.

I am continually amazed at the detail and inventiveness of the IH engineers of the 1930's.

Follow Ups:

• Re: Hydraulic Delay on Belly Pump williamf 12:01:21 12/21/04 (0)

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