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.

 

[4570Man]

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.

 

[thebmrust]

The OP is who decides if it’s useful to him. Same as the rest of us. We have a need and buy or build. Budget, time, or profit/loss often decides the path we take.

 

[thebmrust]

You should see my Suzuki Samurai dumptruck.

Don’t tease us, show us some pics!!!

 

[dfkrug]

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.....

a homemade utility vehicle with hydraulic dump

Well, not completely homemade; I started with a Suzuki Samurai. Moving dirt around with your tractor, one loader bite at a time can be pretty inefficient and frustrating, esp when you need to move the dirt more than 100 feet or so. 500 feet, and you REALLY want a dumptruck. So.....I have...

www.tractorbynet.com

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.

 

[jamesgpeck]

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?

 

[Gord Baker]

RENT ONE. Renting one 10 times will be cheaper and better than building one.
2'x4' base is ridiculously small. Digging flower beds?

 

[lilranch2001]

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

 

[wantit]

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.

 

[Deltadart 106]

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.

 

[balsam]

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

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.