Metal Thickness?

[ptsg]

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?


View attachment 773372

BxB301, I saw one of these machines on an Ag fair this summer and spent some time absorbing all the info I could. I actually saw the bigger brother that also swings the boom left/right along with the swing of the entire upper structure.

The steel used was, for the most part, 10 mm all around, with some reinforcements around the pin areas. Things like covers were 5 or 6 mm, while other stuff used 8 mm. Basically, 10 mm for the structural stuff, 8 mm for the not so much structural stuff and 5 or 6 for the rest.

As far as hydraulics go, I can only recommend that you go with a Tandem pump and use two separate valve blocks. Preferably, two 3 spool valves, mounted one on the left and other on the right. Each valve block should have a joystick for two of the spools and a lever for the other spools. The joysticks will control all the backhoe functions, while the levers will control left and right tracks. If you're planning on adding a blade and an extra function, you can get 4 spool valves.

The tandem pumps will allow you to have full flow for each track and also will allow to work more functions at the same time at the backhoe compared to using a single pump and trying to feed 4 functions at the same time.

As you found out already, not many people on this forum is supportive of this kind of projects for some reason, but please, don't get dis-encourage. I'm really looking forward on what you come up with.

I'm all for DIY projects and along with several other projects, I've built a backhoe myself and it's been awesome to have. I can beat the cr@p out of it, and if it breaks, I can fix easily. It's was a great project to get into fabrication, welding, machining, engineering, etc, specially considering I start building it being 10 or 11 years old with the help of my dad. It's been constantly evolving ever since.

Here is a link to a video of the mini excavator I saw. It's in French though but it may give you some more ideas. I believe the guy also has a video going in depth on the machine.

Oh, and another recommendation, is that you definitely build a blade. I build one for mine recently, and it's been a complete game changer. Here is a picture of mine. Not necessarily pretty, but functional.

 

[dfkrug]

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)

There are now plenty of these small Chinese mini-excavators imported into the US. Many are imported with the B&S 420cc gasoline engine and not the illegal 499cc diesel engines they usually come with. Expect to pay $10-12K retail in a metro area near you. You can import them yourself for about $7500 or so, if you have the patience to go thru the process.

All for DIY myself, I did the above 4y ago and love my XN08 mini-X. I also built the CADDigger 728 back in the 90s, and used it for trenching. Even tho I am an engineer and fabricator, I give a high value to the plans I bought, rather than figuring every design detail out for myself. The 728 featured tubing and plates with 1/4" thickness, and 1/2" plate for the swing frame. A 240V welder is a must, IMO. I used a Lincoln AC 225 buzz-box successfully, tho I have long since moved to DC (MIG and stick).

 

[BxB301]

BxB301, I saw one of these machines on an Ag fair this summer and spent some time absorbing all the info I could. I actually saw the bigger brother that also swings the boom left/right along with the swing of the entire upper structure.

The steel used was, for the most part, 10 mm all around, with some reinforcements around the pin areas. Things like covers were 5 or 6 mm, while other stuff used 8 mm. Basically, 10 mm for the structural stuff, 8 mm for the not so much structural stuff and 5 or 6 for the rest.

As far as hydraulics go, I can only recommend that you go with a Tandem pump and use two separate valve blocks. Preferably, two 3 spool valves, mounted one on the left and other on the right. Each valve block should have a joystick for two of the spools and a lever for the other spools. The joysticks will control all the backhoe functions, while the levers will control left and right tracks. If you're planning on adding a blade and an extra function, you can get 4 spool valves.

Thank you for taking the time to reply.
I was guessing it was 10 mil, thats a little thick for me to weld even with my 220v Mig.
Im not against buying a stick welder for the project though.

I don't know what he was saying in the video, but I strangely understood it.
Also, as I don't want to try to manual bed the back of the bucket, I planned on using 2" stipes to form it, glad to see that's what they did too.

 

[Vigo327]

Building a 'real' mini excavator aka one which can rotate the body continuously over the base, is not an easy thing to fully DIY because of the thing you already mentioned which i forgot the name of, which it pivots on, and carries the hydraulic circuits from the top to the bottom. It's not that it's a complicated object conceptually, it's that it's complicated to DIY one, and buying a 'real' one is pretty expensive!! Lots of people build diggers and maybe 1% of them build a machine that includes that.

But, if you don't have that then you REALLY need the boom to swing, at least. You might be interested in the case of the Ditch Witch Xt850 which mounts the digger arm on another swinging arm to achieve some of the same advantages as having a swinging boom and a rotating base.

I gave serious thought to both building a digger, and buying a towable before coming into a crazy deal on my small tractor backhoe. Even since owning that i have given serious thought to buying a tiny Chinese mini-ex. But for me the option which ticks the most boxes without involving a stupid amount of money for an upgrade i don't 'need' (my tractor backhoe works fine) is simply to build a backhoe type attachment for the front of my tiny skid steer (ford cl20 clone). I don't need the rotating base enough to want to take up that fight. I have no issue with putting myself through the build of the digger arm assembly itself.

 

[BxB301]

That Ditch Witch
That Ditch Witch looks like an interesting machine, but after owning a ditch witch, I don't think I will want one again.
Parts are available, but with many very unique parts they are only available from them for $$$$$$.
Like my Case loader - 0 parts availability. You are making anything you will need.

And yeah, the rotating is a problem. Well, rotating is easy, itse self propelled that is the problem.
You need that rotary union/valve/manifold AND a slew ring bearing large enough for it to pass through.
Those 2 needed parts, used, run about $700-1500 for the manifold, and $800-1200 for the bearing. When you're almost $3k into your build for 2 parts, it would be ridiculous to build your own when just for a pinch more you can import a Chinses machine.
Ive already purchased a bearing, and its load capabilities are impressive (posted below) but it'll never allow for a rotary manifold inside.
I could probably get a single acting cylinder to use a front blade, connected to a single hydraulic swivel, but anything more is just silly.

Moment – 900,000 ft-lbs
Thrust – 1,150,000 lbs
Radial – 230,000 lbs

 

[dfkrug]

Yeah that rotary valve that goes between a mini-X house and track frame is not something we normally run into. Might be called a "distribution valve".

I bought my first Chinese mini-X to modify and customize. And repair, if necessary. I bought a bunch of spares at the time, but mostly I have not needed them.

I am prepared to remove and service the house bearing and distribution valve if I have to, but so far, my machine has proven to be reliable. I have reached out to other local owners of these machines, but have heard of few failures. The original diesel engines are not good (if you sneaked one into the US), but the gasoline thumpers are cheap and reliable.

I DO wish my machine had hydraulic braking valves on the wheel motors. Direct-acting track drive motors really need this for safe use. All the name-brand 1-ton units have planetary final drives to avoid this problem, apparently.

 

[DaBear3428]

I was thinking about using the same material on the whole thing (or, "body)
I have about 2 sqft of 5/8th plate, anything else I would need to buy.
Local metal shop doesn't have scrap, and only sell 4x8 sheets. One sheet should do it, and given the cost, I only want to buy one.
It looks like they did the same thing here, as the boom and base are all the same thickness.

Ill be using it in the Arizona sand to dig trenches for sprinkler pipe, and a future block wall footing. Past that, just random digging projects.
I have a ditch witch now, but its absolutely miserable in the sand. Its like Atreyu trying to pull the horse out of the mud in The Neverending Story.
I've thought about mounting a winch to it, so it can pull itself along. If I can successfully build this, selling that clunker should mostly pay for it.

A mini excavator would 100% serve me better, but they are $20,000 on the cheap side; but most listing I see are $28k+
Even used Bobcates are over $30k locally.
Give the cost, storage, upkeep, this tiny machine would serve me better.
(also, this new is about $14,000 + shipping and import)

Pic here, looks a bit thicker than 1/4"
I like that the hydraulic tank is the seat, but I don't see a filter....

View attachment 773396

have you thought about a subsoiler mod to install the sprinkler pipe? and just rent a mini for the foundation work.

 

[4570Man]

You need that rotary union/valve/manifold AND a slew ring bearing large enough for it to pass through.
Those 2 needed parts, used, run about $700-1500 for the manifold, and $800-1200 for the bearing. When you're almost $3k into your build for 2 parts, it would be ridiculous to build your own when just for a pinch more you can import a Chinses machine.

You’ve just discovered why most people don’t think building a machine is a good idea. And some people call them naysayers or Debbi downers. But the facts don’t lie. $3000 for 2 fairly crucial parts. And you don’t have tracks, track rollers, track motors, valve banks, hoses, pumps, the engine, cylinders, or the bulk steel. All of that stuff is expensive.

 

[thebmrust]

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

 

[dfkrug]

....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

Yeah, amazing what kind of payload you can handle with one of those 1-ton PUs.

Fixing/modifying/repurposing damaged equipment is a very resourceful way to go. You should see my Suzuki Samurai dumptruck.

Makes me think of a hoarder guy I know who used to buy (but rarely fix or sell) excavators. Lots of them. The 2020 wildfires in Santa Cruz County burned up his collection, and sadly they all got scrapped.