back hoe hydrolics

[simplicityguy92]

what size hydrolic cylanders do i need for
for a backhoe with a 10 ft lift arm and 8 foot dipper
im only 15 and just learned how to fabricat so i need some help

the backhoe would be 3 pt but go on to my skidsteer with a 3pt quik hitch so

[BHD]

I have been building and fabricating for nearly 40 years now,

and I jsut finished a backhoe of my own design, I first bought 2 or 3, sets of plans and down loaded a few free plans as well, and down loaded pictures from eBay and many many pictures off the net, to study designs and ideas, and also started to collect parts manuals and part books,

also down load or get brochures from many manufactures, usually the pictures are nearly a set of plans, Grid them and then enlarge them,
How To Enlarge a Drawing Using a Grid | eHow.com
Drawing Using a Grid

if you copy an existing design you will benefit your self, by letting some one else do much of the design work,

much of the cylinder size, needs to be balanced with the strength of the materials one uses, and design, if one uses short strokes one will need larger cylinders and if one uses long stroke cylinders they can be smaller as you will have more travel and be using more leverage, and the hydraulic pressures one uses.

so to answer your question is not some thing one can do with a lot more information, and know the design and what your wanting to have for power, and abilities,

your dealing with a "large" backhoe for a home built unit with those dimensions,

but one could built it with 2,1/2" cylinders and one could built it with 5" cylinders, and both will dig, and depending on the materials one uses, you may jsut bend it in to scrap iron or it may be under powered, some will depend on the strokes you chose as well. and the leverage one designers into the machine,

again being 15, the back hoe project I jsut finished would have overwhelmed me at that age, and I do feel I have above average mechanical ability, and was a fair welder that that age.

first one needs to consider the cost, and it my be that your independent wealthy, but I used 95% scrap iron out of some old machinery to built my machine, so the steel was not much of an issue, but the hydraulics cost me close to $2000 before I was done, cylinders, valves, fittings, tubing, hoses, etc,

my recommendation is to get a set of plans if your serious, and follow them or enlarge them a few percent to get the unit your desiring,
(personally I think that may be a real challenge for you and my guess of your skills),
if your really intent on it, search EBay or wrecking or scraping yards, or other, and buy a junker and rebuilt it, new bushings and or cut our and have new bushing made and weld them in, and rebuilt the hydraulics, it will be probly be cheaper than buying steel.

IF your intent on doing this, study a multitude of designs, get basic books on basic hydraulics and principles,
and get a friend that is a good fabricator and buddy up with them so they can mentor you, and listen to there guidance, learn and learn and learn some more, study and study, you will be benefited if you have access to a machine shop as well, a minimum of a large drill press capable of drilling up to 2,1/2" holes, a set of large reamers, for reaming and aligning of the pivot points, and reaming out bushing stock, and other.

If you do one from scratch you will encounter many many obstacles in the construction of

see here is a 'lighter duty hoe" the reach is close to what your wanting to build,

Truckhoe&Towable Truckhoe - Versatile Backhoe Alternative
it is using 25 gallon a min, hydraulics
a heavy duty unit would take much more,

an unless you have a fairly hefty skid steer loader that is a lot of back hoe, and you would probly need stabilizers as well, to use it efficiency,

mine is smaller than what your design parameters are as you stated them, (not a micro) but I have it mounted on a 8000 pound 100 hp tractor, and if you do not put the stabilizers now it will shake the tractor all over, (it has a sub frame),

attached is a picture of the unit I jsut finished,

[BHD]

one other thing if you design this and or if you follow plans, make full size patterns (cardboard or ply wood) of all pieces and (use small bolts and washers) to make pivot points, and make sure all things will bend and turn and clearances will be adequate, for all bending points, room for hoses and no binding of cylinders, (you can lay out the cylinders on the floor, closed and extended) and use actual cylinders or you can make mock up cylinders out of template materials to make it in all positions, but if one does this it may eliminated some mistakes and or broken bent parts.

also when sizing your cylinders your gallons a min you have may make some difference to what is chosen, to large it will be very slow, to small it may be to fast, and be uncontrollable.

so there is a lot in how to size the cylinders.

[RonMar]

Originally Posted by simplicityguy92

what size hydrolic cylanders do i need for
for a backhoe with a 10 ft lift arm and 8 foot dipper
im only 15 and just learned how to fabricat so i need some help

the backhoe would be 3 pt but go on to my skidsteer with a 3pt quik hitch so

A backhoe with a 10' boom and an 8' dipper sounds like an awfully big backhoe to fit on a skidsteer. The structure required to keep those 2 parts from deforming when in opertion are going to make this thing VERY heavy. Not to mention the pivot structure required to swing it. I think that size backhoe would lead to a case of the tail wagging the dog. Those dimensions are what I would expect to see on a very large tractor(greater than 100HP and 3+ ton in weight?). I would think something smaller with say a 5' boom and a 4' dipper and about 6' depth of dig would be more appropriately sized to a skid steer. Something more along the lines of what you would see on a 30HP tractor.

What are you building it for? I find it best when designing something to set a performance goal, and build as necessary to reach that goal. I don't think a skidsteer is going to be an acceptable base to build a hoe with a 15' reach from, at least a hoe that will last beyond it's first use. All the forces applied on that boom need to be supported back thru the skidsteer loader arms...

Do you have anywhere around you that has backhoes such as tractor dealerships or rental stores? Go get some hands on and see how some are actually built, the thickness of the plate used, the size of the pins and pivots. There is a reason they are built like that, as the forces involved are massive, even on a small hoe.

Good Luck

[simplicityguy92]

i only used 1o ft and 8ft beacause therir easy numbers to diveid from to scale down to 5 and 4 ft for my bobcat.
iv done abit of fabricating eg. snow plow, brush forks, backblade in process, and i manuer forks in progress for my small tractor so i thought id make somethiing more comlicated for the bobcat.

[simplicityguy92]

the laying it out with cardboard is a good idea.

[wedge40]

Originally Posted by simplicityguy92

i only used 1o ft and 8ft beacause therir easy numbers to diveid from to scale down to 5 and 4 ft for my bobcat.
iv done abit of fabricating eg. snow plow, brush forks, backblade in process, and i manuer forks in progress for my small tractor so i thought id make somethiing more comlicated for the bobcat.

Good grief, can't you play video games like every other 15 year old.
I have to admit I'm a tad bit jealous as to how ambitious you are. I see a great career as a craftsman in you future.

Where do you live? I might have some work you could do for me.

And last but not least. We hear at TBN expect pictures of the project. Heck I'd like to see some of the other stuff you built.

Wedge

[3RRL]

I think it's outstanding that you want to do this...at any age!
Just be sure to get a decent design so it is structurally sound. I see you have a lot of fabricating skill, so might as well put it to good use.
Kids like you are hard to come by these days.
I predict you will end up as a very successful person, whatever you choose to do in life.

[BHD]

YOU May find this link of some help,
Free backhoe plans,
http://www.machinebuilders.net/plans...%20plans-1.pdf

[simplicityguy92]

Originally Posted by wedge40

Good grief, can't you play video games like every other 15 year old.
I have to admit I'm a tad bit jealous as to how ambitious you are. I see a great career as a craftsman in you future.

Where do you live? I might have some work you could do for me.

And last but not least. We hear at TBN expect pictures of the project. Heck I'd like to see some of the other stuff you built.

Wedge

why play videogames when i can work in the shop.