Metal Thickness?

   / Metal Thickness? #71  
I’m a fan of Frankensteining parts together. I’d hit a machinery or farm auction or two and buy some ratted out pieces of equipment with the potentially functional parts I need and mod it onto another piece of equipment.

I’m envisioning a backhoe on the back of a small pickup or 4x4 vehicle. LOL

A truck backhoe might be useful to a few trades that only need to dig one hole in one spot but the poor maneuverability of that would leave it very near worthless.
 
   / Metal Thickness? #74  
Don’t tease us, show us some pics!!!
I posted this thread about 9y ago. Still works well, but need to upgrade to electric fuel pump. Kinda like to replace it with a 4x4 Workman or ProGator.....

To reuse "junk", I made the deck of the box from a Ford Ranger box, the hyd cyl was the first dump cyl on my concrete mixer, the PS pump stolen off an Infiniti Q45. The Weber carb I had to buy (used for $100). I used a new Grammer tractor suspension seat.
 
   / Metal Thickness? #75  
Heck Northern Tool sells a nice little mini - excavator. Brand new for $18K.

I'm all for the "Build it yourself" mentality. There was a member here from Eastern Europe that built a curved boom backhoe and started (I don't know if he finished) an excavator. Both rivalled the best you can find on the commercial market. But this member was no hobbyist fabricator. His skill in design, fabrication and welding was nothing short of amazing.

You just said you have a cheap welder and aren't the best. I'm going to assume your skill set is in the same realm as mine. Capable of a decent repair, maybe some light fab work, etc. I'm proposing a middle ground. Why not find a digger like WranglerX linked and fabricate a vehicle (track or wheeled) under it? At least 60% of the rig will then be built for you already.
The hobby press was selling a small self-manufactured backhoe plan 30 years ago. You could build that one. If you are going to all the trouble of designing a machine, use CAD and end up with a set of saleable drawings.
Why do you need it to be self propelled. The above plans had two unpowered wheels and a third foot. You could move it by raising the foot by pressing the bucket against the ground and moving the boom.
An alternative to rental is buying one used, using it, and then reselling it. What if you spent every waking hour for a couple of years on your project plus a bundle on materials, and did not end up with a useable machine?
 
   / Metal Thickness? #76  
RENT ONE. Renting one 10 times will be cheaper and better than building one.
2'x4' base is ridiculously small. Digging flower beds?
 
   / Metal Thickness? #77  
Couple hundred?! Its $500 a day, or $2000 a week, and you have to put your name on a waiting list where you get notified the evening prior to the machine delivered.
AND! If you don't have a 1 ton truck and trailer, you have to pay the $500 delivery fee. I live within viewing distance of the rental yard, and they wont let me drive it here; but when they deliver it, they drive it. Jerks



;-)



Calling this thing an excavator is a huge stretch. More like a power assisted shovel.
Now, Aside from the drive train, which I said I was ditching anyway - I could buy all the material, hydraulics, plasma cutter, a better welder, and a predator engine to power the thing, and still be well under the price of a new one.
Not only that, I think if I did use 1/4" material, and it bent, I would still have money left over to build version 2 out of thicker stuff.



Maybe the scale of the thing isn't coming across. The operator platform (or cab?) is less than 2'x4'
I put the images into Fusion 360, and calibrated using the known base dimensions to get the dimensions of the boom and arm, I don't remember what they are, but the boom is just under 3' long. Where its pictured driving into the van, at that stance its probably 7' long.

I agree on the money spent on every aspect of equipment, but this is not a John Deer or a Caterpillar, or even a Kubota. This is a cheaply made Chinese machine, being exported and rebranded all over the world. (except the US it seems)
Those aren't the cast iron track rollers you would find on a bobcat, those are stamped and formed steel rollers. It does have a steel cog wheel, but not the same quality you would find on a US machine - but it doesn't need to be. Each one is only responsible for moving a couple hundred pounds, unlike a Bobcat, where its closer to 7000 pounds.

Those are 180x72x31 tracks - dirt cheap ... in China.
31 being a less common size, but if you go with a 180x72x39, they are less than $80 each, unless you buy 25+ then you get the 50% off bulk price. But, shipping one set isn't cost effective compared to just buying them from someone in the US who imported hundreds of them to sell at a massive markup.
If you go with a 180x64, you get into modern snow mobile size, and more track wheel options (the more there are, the cheaper they are)

Simple fact of a 'real' machine is the quality, and mostly built to last. The manufacturing and markup on quality equipment is a whole subject by itself.
This is neither. Its a cheaply made machine with a huge markup. Most common complaint with cheap machinery is the lack of replacement parts - and there are many reasons for that which is a whole discussion by itself.



Of course. You aren't using this to break up concrete and load a dump truck.
You are using this to dig trenches for sprinkler pipe, holes for trees, and footings.
Its a small, light weight machine made for small uses.
You shouldn't compare this to anything that has more than one cylinder.



Well yeah, but that's common on most machines.



Correct. But again, you need to remember is use - light duty use. In my case its sand.



Not all rental places are created equal, at my local rental yard if it breaks, you pay for it.
They require a couple thousand dollar retainer to cover any equipment damage and mechanical failure.
This bother me, because if you are renting a machine with a few thousand hours on it, can you really be held responsible if the pump dies while you're using it?



So you think I should use 2"x3"x1/4" box for the boom & arm then?
Good luck😳
 
   / Metal Thickness? #78  
I would try a Kubota BX25D to see 8f it would do the job. I have one and it is very fun to use around a large yard, but only good for small jobs like poster described. Looks like decent used ones are $15-$20k.
 
   / Metal Thickness? #79  
This may have already been addressed and I missed it. There is more to consider than the thickness of the steel. Many parts of tractors are not made with a mild steel but a low carbon or higher alloy steel. Stronger, allowing it to be less thick and more strength. To weld those steels, there are welding filler metals (wire) designed for them. Also, how will you cut the steel into the parts needed for fabrication. Oxy/fuel torch, plasma, or commercial water jet? Then comes the handling of and jigs to hold the parts in place to be welded. Also the smaller capacity welders such as the one you listed are really not designed to do this type of job, companies will list under ideal conditions for very brief periods of time welding output. In some cases it can be "smoke and mirrors". You really need to investigate the machine and the filler metals you will be using, or you may be very displeased with the outcome.
 
   / Metal Thickness? #80  
Im going to try and build myself a mini digger, similar to the one pictured.
Its a small machine with just under a 2x4 base, powered by a Honda GX160.
Without the tracks - given the cost of the tracks, motors, roller wheels, sprockets, rotary union, and a turret bearing large enough for the union, it'll have 2 roller wheels and 2 legs.
Anywho, I was going to use 1/4" steel plate, but the pictures look like it might be a 5/16 or 3/8 (or, given the country of origin, 8 or 10mm)

Think 1/4" would work?
I have a Weld-Pack 180, which technically can weld up to 1/2", however as I'm not a pro-welder, I'm more comfortable with 1/4"; but I don't know if it'll be strong enough.
Also, cylinder bore size, should I do 2", or smaller?


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I have read through these posts and I think you should go ahead with it. You obviously have done your homework and already worked out a lot of issues. I find, though, that when costing out something like this I often underestimate the cost of all the little pieces I need to pick up, here and there….fasteners, paint, etc, etc. I always include a percentage at the end for that stuff. It’s surprising how that stuff adds up. Hydraulic hoses and fitting can add up in a hurry.
With regard to metal thickness: I feel that 1/4” plate would be adequate, as there are lots of ways to stiffen things, in strategic places, with gussets, braces, etc. You do need a certain amount of weight in the body, however, to offset the tipping moment of the load, cantilevered out front...thickness of the material they used may be thicker than structurally necessary to deal with it. Excavators have weight added to the rear of the cab for this…..something you could do, also.
You mentioned being comfortable only welding up to 1/4” plate. I assume that would be for butt joints, which I see very few of in that fabrication. I suggest you look into multi pass, weave and bevelled joints online. With your mig machine, you can weld any thickness using the correct procedure.
Its a little difficult to guess at the proper cylinder sizes you need but it would not be difficult to work out mathematically once you know the full bucket weight and the cantilevered load itself. Of course your hydraulic flow and pressure have to be taken into consideration as determinants for force and speed of operation.
I have designed a lot of hydraulic circuits and learned that there are a lot of factors to be taken into consideration.
All that being said, given your responses to some of the comments, I’m sure you can do it. I wish I lived close by, I would love to be involved.
 
 
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