Backhoe attachment, on a trailer. Making it a towable!

[Biohazarus]

Hi there, I do not have a tractor but need a digger. (Don't ask why, I just need, OK):laughing:
Was looking at towable one and thinking I can "easily-ish" build one.
Then started to look at used backhoe attachment on kijiji.

Looks like I could get one for cheaper then the hydraulic and control. Not taking about material and design issues.
So wondering if anyone have the similar idea about building a trailer mounted with hydraulic pump/motor, around a "off the shelf" backhoe attachment.
This could be extended to be a 3 point trailer on which I could eventually mount any 3 point attachment, but I don't have any, and read that 3 point might not be the best for backhoe as weaker...

Since I don't have a tractor, I am free to find any backhoe attachment "size", but can someone shine some light:
1) am I stupid / pioneer (hard to differentiate sometime)
2) What size motor pump should I get? When attachment is meant for, let say a 30hp tractor, should I get a 30hp motor or power at pump is not as much as tractor rating?

 

[fried1765]

Hi there, I do not have a tractor but need a digger. (Don't ask why, I just need, OK):laughing:
Was looking at towable one and thinking I can "easily-ish" build one.
Then started to look at used backhoe attachment on kijiji.

Looks like I could get one for cheaper then the hydraulic and control. Not taking about material and design issues.
So wondering if anyone have the similar idea about building a trailer mounted with hydraulic pump/motor, around a "off the shelf" backhoe attachment.
This could be extended to be a 3 point trailer on which I could eventually mount any 3 point attachment, but I don't have any, and read that 3 point might not be the best for backhoe as weaker...

Since I don't have a tractor, I am free to find any backhoe attachment "size", but can someone shine some light:
1) am I stupid / pioneer (hard to differentiate sometime)
2) What size motor pump should I get? When attachment is meant for, let say a 30hp tractor, should I get a 30hp motor or power at pump is not as much as tractor rating?

My experience with attempts at reinventing the wheel, have never worked out.
Do you really want to spend your time and money on a prototype that will have zero resale value?

 

[GLyford]

You could start with one of these...wouldn't take much AT ALL to get it to be what you want:

9 HP Towable Backhoe

14.5 FPT Towable Backhoe | DR Power Equipment



Or you could use established and tested plans (CADplans is also on TBN, btw):

CADDiggers
You can get all the metal pieces and parts together as a kit from MetKit Corp - Home Page

 

[frugalangler]

Sometimes when resources such as $$ are limited, create your own is a valid approach! Necessity is the mother of invention, or in this case cloning, if one patterns a build after something that exists already (there are already some successful tow-able diggers) and can source the components used cheaply, and has the fabrication capability (backyard shade-tree shop and skills) then I'd say go for it, but ---------- be very conscious of safety factors, since you're likely not going to have engineering software to compute stress points, etc, over build to a considerable level.

Sometimes I actually do this type of thing just to prove to my self I CAN DO IT! Satisfaction factor!

If you go about it, please document and seek advise, hopefully someone will provide some decent suggestive guidance, \

Good luck in you adventure.

 

[aczlan]

2) What size motor pump should I get? When attachment is meant for, let say a 30hp tractor, should I get a 30hp motor or power at pump is not as much as tractor rating?

You need to know how many gallons per minute of hydraulic flow the attachment is rated for and at what pressure.
Then you can use one of the many hydraulic calculators out there to see what size motor and pump you will need.

Aaron Z

 

[davedj1]

Find an old Jeep and mount one on the back, run the pump off the pto on the transmission. Growing up here in farm country every other place you looked there was a truck or Jeep of some sort with a backhoe attachment on the back of it. This was long before mini excavators.

 

[countrybumpkin]

Here is a video of one built by a guy.

Homemade backhoe / toe behind - YouTube

 

[BrokenTrack]

Hi there, I do not have a tractor but need a digger. (Don't ask why, I just need, OK):laughing:
Was looking at towable one and thinking I can "easily-ish" build one.
Then started to look at used backhoe attachment on kijiji.

Looks like I could get one for cheaper then the hydraulic and control. Not taking about material and design issues.
So wondering if anyone have the similar idea about building a trailer mounted with hydraulic pump/motor, around a "off the shelf" backhoe attachment.
This could be extended to be a 3 point trailer on which I could eventually mount any 3 point attachment, but I don't have any, and read that 3 point might not be the best for backhoe as weaker...

Since I don't have a tractor, I am free to find any backhoe attachment "size", but can someone shine some light:
1) am I stupid / pioneer (hard to differentiate sometime)
2) What size motor pump should I get? When attachment is meant for, let say a 30hp tractor, should I get a 30hp motor or power at pump is not as much as tractor rating?

Holy smolies man, you do not need anywhere near a 30 hp motor. I kind of have what you want to build, but mine is an off the shelf log trailer that can mount a backhoe upon it. In my case a 6.5 HP with small hydraulic pump gets the job done. It can dig anything, it just does not move fast doing it.

As for being on a trailer...it has some real limitations because while I can swing my boom around 270 degrees, I cannot dig where my trailer is. So to dig a water line lets say, I have to carefully put my trailer perpendicular with where I want to dig, then dig 180 degrees to my trailer...yes on each side. By leap frogging along the intended trench I need I can get the job done, but it is a lot of maneuvering. Sometimes I have to put down planks and back my trailer over a dug trench to get where I need to. Sometimes it is a bear to get the trailer at the right spot I need to dig!

It is nice to have kicking around though, and beats a shovel, but I am not going to dig a house foundation with it that is for sure.

If you build one, make sure you can dig 270 degrees around the back of your towable unit, and just have a tongue on it. Also only put one axle on it and not two, that way it can be self movable. Just use your backhoes to lift the dead end off the ground and then by curling in your bucket, drag the machine ahead on the wheels that are in the back. When you go to dig, the frame sticks down into the dirt and holds itself there for digging. In this way you do not need to tow yourself into position everywhere. (Mine cannot do any of this).

 

[Kernopelli]

If you want some good ideas look at Dig IT towable backhoes Lots of towable designs to look at for your design. The first pic is of a DigIt towable like mine.

 

[bcp]

http://www.tractorbynet.com/forums/build-yourself/200605-backhoe-update-im-making-progress-post3313234.html#post3313234

Bruce

 

[4570Man]

You can get by with a much smaller motor probably 5 gmp at 2500 psi would be adequate. The biggest problem I see is weight and cost. You’re going to have to add considerable ballast to make this thing something that resembles useful. Second problem is the resale value of this will be very low. The resale value of a used machine that was bought right is near 100%.

 

[4570Man]

I don’t know what your budget is, but I doubt you can pull this off for less than $5k. That would go a long ways toward an existing machine.

 

[BrokenTrack]

I don稚 know what your budget is, but I doubt you can pull this off for less than $5k. That would go a long ways toward an existing machine.

I disagree, I think a person could build a towable backhoe for well less than $5,000.

I might consider buying a woodsplitter. A decent one costs $750 and would net a person an engine, hydraulic tank, pump and one cylinder. From that a person would just need to buy 3 more hydraulic cylinders at a few hundred a piece, a 4 valve stack from Supply Center for a few hundred bucks, hoses to connect it all, then some steel to make the machine. It would be hard to give an exact figure, but I figure between $2500-$3000 to build one. Making it yourself though would enable a person to have a more capable machine.

There is something to be said for just going out and renting a machine because $3000 would get a lot of digging days out of a rented machine, but what I have found is, having a small backhoe around allows me to do the little jobs that are too big for a shovel, and yet too small for anyone else to want to come in and do.

The other thing too is, when you get attachments, you use them for a ton of stuff you never initially envisioned just because you have it.

 

[4570Man]

The op was wanting to buy a tractor backhoe and convert it to trailer mounted. I don’t see any backhoes that have potential to work again for less than $2500. The op might find a cheaper one. $2500 more to get a trailer, and the rest of the hydraulics seems reasonable.

 

[Gary Fowler]

Call me lazy , but this is what I would do. It has stabilizers to hold it in position (unlike the $3000 one) and it can move itself around. When finished just hook it to your tow vehicle and take off.

14.5 FPT Towable Backhoe | DR Power Equipment

 

[Groo]

If you are buying a used backhoe attachment initially intended for one specific machine, match the pressure (less will drop your digging force, more could easily damage something) of the hydraulics it was intended for and go with less flow than the base machine intended. The toe behind wont have the weight of a tractor on it to keep it from jumping around, so you will want to go slower for a bit of reduced violence.
on a budget, you will definitely want open centered hydraulics, because closed centered hydraulics pretty much require a variable displacement pump, and those are much more expensive than a cheap gear pump.
Once you have a flow number you want to hit, you can calculate the pump size based on that and the engine RPM (usually 3600rpm for small stationary engine like a Briggs or cheap Chinese Honda knock-off). once you have pump size and pressure, you can find torque requirements pretty easy.
here are the pertinent calculators;
Hydraulic Motor Calculations - Womack Machine Supply Company

here is an example on choosing pump and engine;
lets say you want 2000 psi and 7 gpm.
a .5 cu-in/rev pump will give you a bit over 7 gpm at 3600rpm, so lets go with that.
here is a fairly cheap .55 cu-in rev pump that can be spun to 5000rpm and can handle 3480 psi; so that will give us a generous cushion and the pump should actually last quite well in this application.
Hydraulic Pumps | Gear Pumps | Dynamic Hydraulic Gear Pump �.55 cu.in/rev | B537177 - GlobalIndustrial.com

.55cu-in/rev needs to only spin 2940rpm to make the desired flow.

.55cu-in/rev @ 2000 psi needs 175 in-lbs or 14.6 ft-lbs.

the harbor freight 8hp engine makes 14.9 ft-lbs peak at somewhere near 2500rpm, so that would be a great match for this combo when driven directly.
8 HP (31cc) OHV Horizontal Shaft Gas Engine EPA

this combo would cost $230 for the engine and $95 for the pump, plus whatever you need to splice the two together.
another possible solution would be to use a go-cart clutch and chain to attach to two. since you would get a gear reduction when doing that, you would need a larger pump, but don't get a gear pump that would be spinning less than 900 rpm when running. they loose efficiency going too slow.
you might do a belt drive and could gear up or gear down the pump. if you speed it up, you can use a smaller cheaper pump. Just be sure you don't spin the pump faster than it is rated for at full engine speed.

ETA. don't forget filtration!

 

[texasranger556]

Its differs a lot by area. I see skid steer backhoe attachments on Craigslist in the $2000-2500 range fairly often. There is a bush hog 962 listed for $2k right now that looks in good shape but has some leaks.

 

[Reg]

Back hoes, excavators and similar devices are able to do the work that they can do largely because they have MASS against which the bucket can pull/push.

Mounting something on a trailer would put it on (relatively) squishy wheels and you would find them flexing as they absorb some of the force - then letting go when what you are digging into comes loose.
Don't count on the mass of the tow vehicle to help you out, the trailer is is attached by a hinge - a 3D hinge (ball/coupler) at that.

 

[Groo]

Back hoes, excavators and similar devices are able to do the work that they can do largely because they have MASS against which the bucket can pull/push.

Mounting something on a trailer would put it on (relatively) squishy wheels and you would find them flexing as they absorb some of the force - then letting go when what you are digging into comes loose.
Don't count on the mass of the tow vehicle to help you out, the trailer is is attached by a hinge - a 3D hinge (ball/coupler) at that.

a backhoe attachment likely has outriggers, so the back will be solid. If its got a decent sized tongue it would have loads of leverage against the ball. it could be easily useful. Like I said, I'd just go a bit slower with it.

 

[BrokenTrack]

This is more in line what I was thinking about. I still do not see more then $3000 in it, and other than the bucket curl cylinder being too short, it is a lot more capable then my Wallenstein Log Loader Backhoe because it can go deeper. The video also shows how two wheel towable machines can be moved on their own power.

Don't get me wrong, this is no Hitachi 1200, but for the money, and ease of build, I think its a very decent machine. I think if someone spent $3000 building it, they would be happy versus that of having a spade and pick axe.