Completely homemade excavator

[snowb]

VERY COOL! This is very ambitious and you seem to be chugging along, this gives me some guilt about letting my own larger projects grow stagnant. You inspire me. Thank you for sharing.


I am curious about your hydraulic system design. By my rough estimate, 19GPM @ 3,000PSI would require at least 40HP. Since you're using a 15hp engine I assume you are using 19GPM at lower pressure (for fast transit) OR 3,000PSI for digging/pushing, but not both at the same time. In my experience this kind of arrangement is addressed with load sensing valves that control the displacement (swashplate angle) of the pump. These systems get pretty complicated pretty quickly. I have pondered simpler ways to do it, and I'm curious if you've found one of these simpler ways, or if you're using load sensing. Actually I'm just curious in general, about all of it, mostly the hydraulics.

Thanks,

For example a KX71 excavator has a total hydraulic flow of 35GPM with a 27HP motor but does not use all at the same time at maximum force. As for shoveling it uses only 5 GPM, the engine runs in neutral, despite everything the operator does not have the choice to increase the engine speed to have a good shoveling speed.


On my excavator I have an adjustable valve to divert a percentage of the flow rate of 12.7GPM directly to the tank without pressure build-up. I would have all the flow I wanted in shoveling mode without increasing the engine speed, because 5GPM / 3000PSI does not require a lot of power (9HP is sufficient, it is not 3000psi continuously)
I have used this system on my 2 previous excavators and it is wonderful to be able to adjust the speed beyond the engine speed.
The 6.3 GPM auxiliary will be used to give an acceleration of 2km / h no matter what percentage of flow the 12.7 will be adjusted. To use 19gpm at 6 km / h I would not need 3000PSI to move on normal terrain without pushing sand with the blade. If I need to push the 6.3 will not be activated.
My experience with diesel engine pumps has shown me that we can use a flow 30% higher than the rule of 3GPM for 6.5HP, if the pump does not work continuously close to 3000PSI.

 

[snowb]

Snowb,
Awesome project. Are the trailer wheels and tires gonna be your idler wheel at the tensioner? Also, can you show more photos and information on your Kubota crawler lift? That little thing looks awesome.
hugs, Brandi

Thanks,

the dozer snowblower blade rear lift bucket https://www.mytractorforum.com/threads/mini-dozer.738865/


Yes they a trailer hub with shortess possible axe. The wheel is a plain steel disc for correctly guide the track in the central groove

 

[bindian]

Which is pretty much what itç—´ supposed to do. Is lifting the rear 1/4 inch vs 2 feet any different?

The biggest and most damaging thing is the center of gravity of the machine shifts. The more it is lifted at the rear, the more the center of gravity (and mass of weight) moves forward. Get center of gravity (CG) too far forward and components and parts are subject to forces they are not designed to withstand and they become overstressed.

Not so stubble is seals on tensioners can blow and you throw a track.

Stubble, like the CG moving forward, is balanced weight on the turntable moving to one side and prematurely wearing out turntable bearings. It all adds up to $$$$ for repairs. It does matter, if you are paying the bills.
Brandi

 

[LD1]

The biggest and most damaging thing is the center of gravity of the machine shifts. The more it is lifted at the rear, the more the center of gravity (and mass of weight) moves forward. Get center of gravity (CG) too far forward and components and parts are subject to forces they are not designed to withstand and they become overstressed.

Not so stubble is seals on tensioners can blow and you throw a track.

Stubble, like the CG moving forward, is balanced weight on the turntable moving to one side and prematurely wearing out turntable bearings. It all adds up to $$$$ for repairs. It does matter, if you are paying the bills.
Brandi

I wouldn't exactly call what he did, for a picture, as abuse.

IF that is done every time, and allowed to slam back down from several feet...sure.

But the machines are built to handle this. Id really hate to see you on one being paid hourly

 

[4570Man]

I wouldn't exactly call what he did, for a picture, as abuse.

IF that is done every time, and allowed to slam back down from several feet...sure.

But the machines are built to handle this. Id really hate to see you on one being paid hourly

You’re right that letting it drop and slam back down is by far the hardest thing about doing that which I’m pretty careful not to do. Lifting it the first 1/4” is the hardest part. It gets easier to lift the higher it goes. And the blade has like a 4” or 5” cylinder that’s pretty much a straight push without mechanical loss. It’s not working very hard to hold the whole machine.

 

[bindian]

I wouldn't exactly call what he did, for a picture, as abuse.

IF that is done every time, and allowed to slam back down from several feet...sure.

But the machines are built to handle this. Id really hate to see you on one being paid hourly

Yeah, there always a chance there might be damage you haven't seen and doing stuff like raising the rear end on purpose just might snap that unseen damage.
If someone was paying me hourly to run one, I wouldn't be raising the rear end a foot or so off the ground. But I would be pushing the machine to it's limits. Then again.................I wouldn't be paying the $$$$ repairs either.
hugs, Brandi

 

[4570Man]

The hydraulic limitation of the machine was reached at the point the tracks lifted at all. Pulling it more at least until the oil starvation point which is a lot more than a foot high doesn’t cause any more stress.

 

[bindian]

This excavator is only 2400lbs and has a reach of approximately 12 feet from the front axles. There is still a way to work without overturning, even if it is not the heaviest in relation to its reach, in addition the ground is super soft there, it only holds by the grass.

So you built this "Caterpillar" also? Simply amazing
hugs, Brandi

 

[bindian]

Thanks,

the dozer snowblower blade rear lift bucket https://www.mytractorforum.com/threads/mini-dozer.738865/


Yes they a trailer hub with shortess possible axe. The wheel is a plain steel disc for correctly guide the track in the central groove

This build is awesome also. To bad photo bucket puts those banners on the photos. They make it hard to focus and see the detail well.
hugs, Brandi

 

[snowb]

The casings which pass through the center of rotation all have a live swivle so that they do not twist on themselves with each rotation, of course the rotation is limited to 420degree so as not to do everything on itself which would cause a kink between the guts. There was very little space to put the pipes and 8 rotating joints in the center, no room to put 1 more. Protection plate below.

Difficult to make equipment of this size in this garage, impossible to turn the frame with arms to check the movement of the pipes.