Would a D6 9U generator hydraulic pump fit on D4 7U?

Hello,

One of my D4 7U's is in need of a hydraulic pump to run it's dozer blade. I have a BeeGee pump that I was planning to install for this purpose but I found yesterday that a friend of mine has a D6 9U farm cat with bad engines that has a hydraulic pump fitted to the generator mount. Would this bolt up directly to my D4 7U? I'll have to fab up a different rear support mount I'm sure (and make it look decent) but this pump would be my preference over the BeeGee pump hanging off the rear of the machine. I know i would be losing my generator but I plan to use a deep cycle 12V for the direct pony start and I would keep all the parts in case I wanted to go back to original later.

I also might see if i can get the seat tank off the 9U and put on this D4 that has a smashed side tank, I'm pretty sure I've seen the wider D6 seat tank installed on D4's before and it looks "ok".

Here is a picture of the D6 9U pump;

[attachment=47240]D69U-Pump1.jpg[/attachment]

Here is a picture of my D4 7U generator;

[attachment=47241]D47U-Generator1.jpg[/attachment]

Thanks,
Jordan

Really Unique and Nice job that hydraulic pump setup!
Definitely Kudos' to the guy that dreamed that one up!
I like it! 🤘

Yes very neat work someone has done.

My guess is the drive gear will not be the same but you have one on the 7u generator.

Looking at the D6 pump it is on the small side. Will make you blade move very slow.The Cat pumps where from 30+ to almost 60 GPM,would guess the one pictured to be 15 or maybe less. I am using 2 9u D6's with that size pump very nice for farm implements but way low for dozer rams from when tractor was built.


But I am interested in how the alternator is powered on the D6.

There is enough room on the pump drive shaft to mount a "V" belt pulley to run an alternator. You might need a three wire alternator to get it to start charging at low RPMs, but that wouldn't be difficult.

[quote="Ray54"]Yes very neat work someone has done.

My guess is the drive gear will not be the same but you have one on the 7u generator.

Looking at the D6 pump it is on the small side. Will make you blade move very slow.The Cat pumps where from 30+ to almost 60 GPM,would guess the one pictured to be 15 or maybe less. I am using 2 9u D6's with that size pump very nice for farm implements but way low for dozer rams from when tractor was built.


But I am interested in how the alternator is powered on the D6.[/quote]

Thanks. I thought about the size issue also. I'm not sure what model the pump is, I'll take a closer look and find out. The blade I have has the older style, large cylinders. Would changing to more modern, smaller cylinders speed things up?

[attachment=47247]1949-D47U.jpg[/attachment]

I'll also take pictures of the alternator setup next time I'm there.

Thanks,
Jordan

that small pump may have too much pressure for the big old cylinders, if you installed smaller cylinders, it would spped it up, and the pressure differences might allow for proper push/pull forces.

the large cylinders with high flow low pressure systems were used to get enough surface area of the pistons to lift the blade or to push the blade down. the newer lower flow high pressure system, you can change to a smaller cylinder and still achieve the same force as it is a function of pressure multiplied by the effective area of the piston to equal the force applied.

for example, a cylinder with an area of 6 square inches and 3000 psi can generate a force of 18000 lbs, to get the same force from a pump that only provides 1000 psi of pressure would require a a piston with the effective area of 18 square inches.

area of a circle can be found using the following equation a=pi*(r*r). {sorry, don't know how to make the pi symbol or the squared symbol on a computer}

so if the diameter of the piston is 4 inches, the radius would be 2 inches. for basic math, pi is equivalent to 3.14

therefore
a= pi*(r*r)
a=3.14 * (2"*2")
a=3.14 * 4" square
a=12.56" squared.

so a 4 inch diameter cylinder has an effective area of the piston of 12.56 square inches.

so at 1000 psi the 4 inch cylinder can exert 12560 lbs
at 2000 psi it can exert 25120 lbs
and at 3000 psi it can exert 37680 lbs of force.

speed of a cylinder is determined by the volume of flow that the pump can produce. if the volume of the cylinder is 2 gallons, and the pump can produce 2 gpm, then it would take one minute to fully stroke the cylinder, if you double the pump flow to 4 gpm, it would take 30 seconds to stroke the cylinder. if you reduced the volume of the cylinder by half to 1 gallon and had a pump that produced 4 gpm, it would take 15 seconds to stroke the cylinder.

to find the volume of the cylinder, mulitply the area by the length of the stroke. this will give you cubic volume, then convert the volume to gallons or litres and you now know the volume.

the rod side of the cylinder is slightly more complex as you have to subtract the area of the rod from the piston area to find the effective area of the piston for the oil to push against and create the force. you have to subtract the volume of the cylinder rod from the cylinder volume on the piston side to determine the volume on that side of the cylinder. a non-balanced cylinder will always have less force when retracting the rod, and it will do it faster as less oil has to be pumped into the rod side of the cylinder.

hydraulic excavators use this theory to maximize the productivity. the digging functions, bucket curl, arm in, and boom up all use the large side of the cylinder to maximize force to better penetrate the ground and lift the material. the return functions all use the rod side of the cylinder so you can return to diggin faster. boom down, stick out and bucket un-curl are usually low load situations and they are fast and have less force requirements.

The generator drive is certainly geared up to turn faster than the engine, so the pump may not be as undersized as it appears at first glance. The solution to the pressure problem is a relief valve setting. I doubt there is a modern pump that limits pressure developed on its own, or an old one for that matter, unless its worn badly. So there should be a relief valve on the system to protect the cylinders at end of stroke or other overload situations..... as well as the gear drive components. The generator drive was certainly not ever loaded to that degree just turning the generator.

I have an old LaPlant Choate scraper that I run with farm tractors with high pressure hydraulics. Got along fine for years until the apron lift cable broke and the ejector cylinder could not push the dirt out. It swelled the cylinder barrel. We had it repaired by welding in another barrel and make sure the cable is in good shape anymore! This brings up the point that the pressure developed in the system is determined by the load on the cylinders. So the system may not develop full pressure until the cylinder reaches end of stroke if the loads are normal for the design.

Thanks for all of the information! The point about the generator drive not being designed for the type of load a pump could possibly put on it use does concern me, I would hate to grenade the gears and cause a major issue but if a relieve valve could protect it from that then maybe it would be OK.

Roger thanks for the all the information regarding hydraulics, that will go along ways in getting things figured out for this one and my other D4, it is very slow to run it's blade, it has a crank driven vain pump on the front and uses the older style big cylinders also. I've considered changing the cylinders on it to make it function a little better. One of these rainy days I'll get the specs on the pump and pencil out the system to see what needs changed to fix all of that also.

https://photos.app.goo.gl/UQOAt7ZXc06IvPhy1

[attachment=47343]1953-D4-1.jpg[/attachment]

I have a D2 that has a small Gresen TB 6 (I believe it is a 6) vain pump (smaller than my D4s) and smaller cylinders and it's blade operates almost too quickly but has lots of power to pick the cat right up off the ground so it obviously has a more efficient pump/cylinder setup.

https://photos.app.goo.gl/sNzq3uoZrIfvsMvt2

[attachment=47344]3-Cats.jpg[/attachment]

Thanks,
Jordan