Another Motorgrader

[DRohacek]

Originally Posted by CADplans

Powering the front axle will be eazy-peazy,,,

Simply design the drive of the pump/hydraulic motor to be a little too fast(10-15%) at working speed.
The front axle has to be designed for a single speed, or else the pump will need to be variable displacement
(VD means BIG $$$$ ,, and hard to operate considering the 10 other levers you will already be trying to move correctly,, )

The trick will be to use a VERY low pressure, so that the excess flow will simply go past the pressure relief valve .

You can get the power you want by using a large hydraulic motor, and matching pump.


The pressure has to be low (less than 650 psi) so as to not heat the hydraulic oil too much.
So, you need to buy a hydraulic motor that will give the speed and torque you want when operated at 650 psi.

Now you know the pump size (displacement in cubic inches per revolution)

The pump that you select will simply be sized to give the flow needed to rotate the hydraulic motor at the correct speed.

There is no other spec for a single stage gear pump, only the GPM at engine speed.
I do not know of a pump that is not rated for the pressure that you will be using, so GPM is the only spec for the single stage gear pump.

(The higher the pressure, the greater the heating of oil as it goes past the relief valve)

I simply explained the drive system that was used on an early rear wheel assist conversion for a two wheel drive combine,,
that was used to convert the 2WD combine to 4WD at the lowest possible cost.

I read about it somewhere,, but, that was the "pre-internet" era,,

Actually the front axle will be variable speed because the hydraulic motor will be controlled by a speed and direction control. The pump has little to do with it other than supply oil pressure at a constant level. Any excess pressure/volume is routed to the return line, through the oil cooler and back to the reservoir by the speed controller.

[DRohacek]

Fired up the grader today testing the switch wires. Everything was perfect. No mystery smoke which is a good thing. While is was on the stand I decided to test the rears and attempt synchronization. The back hydro is not moving. Not sure what that is all about yet. I purchased the rear from two different places as pieces so I never saw them run. Only one of the rears has automatic relief valves so I switched those to the rear hydro because the engine sits over them and there is no good way to use manual valves there. The front rear that originally had those valves now has the manual valves and operates as it should. I think I will move the manual valves back to the rear just to see if that makes any difference.

On a different note I had only planned to check the wiring and makes sure the engine was running properly but when everything went along without a hitch I decided to engage the belt tightener just to test the rears. My brain fog apparently had not cleared yet as I forgot that I had the return fluid line removed from the spool valves. In case anyone needs to know the charge pump will produce enough pressure to spray about 15 feet across your garage. At least I feel like the system is flushed pretty well now.

[DRohacek]

I had built the perfect battery box and tucked it down between the frame rails and was just as happy as I could be with how nicely it all fit into the tight spot. Putting my metal brake to work I was impressed with the finished product as the battery was a nice tight slip fit into the box. As I tried to start that big ole 58 cubic inch opposed Kohler it was obvious that a garden tractor battery was not going to work. So now my beautifully hand crafted battery box lays in my pile of "i'll use that some day parts" in the corner of my garage and I had to find a different spot for a full size group 27 battery. Oh well minor issue.

[DRohacek]

Attachment 107784Attachment 107781I am not making a lot of progress with installing the hydraulics because of back ordered parts. The spool valves are 1/2 inch BSPP that I am converting to JIC6.
Those pieces are back ordered keeping me from installing the hoses to the spool valves. I worked on getting the hood closer to what I want. The grill and hood are from a 100 and so the hood narrows sharply at the rear. That would not be a big deal if I were using a single cylinder engine. The opposed twin is very wide and so as the hood gets closer to the bulkhead it is just too narrow. I had to split the hood, cut a new center section and also extend it about 6 inches. I finished the bulkhead and plan on gluing a rubber trunk seal around where the hood mates to seal it and stop vibration harmonics. I probably should have just bent a new hood because the bondo work to hid everything is not my best subject. I have a friend that says he doesn't mind body work. I think this is his job! A few pictures as I keep moving a bit at a time.

By the way the knee surgery went well and I expect to be back to work in another week. I am pain free and have 100% mobility!

[DRohacek]

I keep forgetting to rotate the images.

[DRohacek]

Under it's own power and hydraulic completed. The hood is not completed. Some body work still needed and some sheet metal work still to be done before painting.

[DRohacek]

[ATTACH]Attachment 108731[/ATTACH]Attachment 108731
Got some paint on it while the weather is decent.
Not finished but I won't have time to get to it again until it's too cold to paint.

[DRohacek]

Back inside until I have time to get back to it.

[DRohacek]

One more picture for now. Those vice grips have been on there so long that I need to give them a part number.

[Getter-Done]

Great Job



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