Backhoe Design Ideas

[dfkrug]

Here are some rough draft drawings from Sketchup. Big thanks to FlatheadYoungin for telling me the easy way to export .jpeg images.

Based on the dimensions in the drawing and the cylinders that I plan to use, I figure the digging depth with be a little over 9'. The reach will be almost exactly 10', and the transport height will be below my ROPS.

The other decision I've made is to use 1 1/2 inch solid square stock to insert into the 2 inch tubes of my subframe to connect the backhoe to the subframe. I'm figuring to have them go about a foot in with a pin on each side to hold it in. I did make one side shorter than the other. The thinking there is that I can get one side inserted into the tube, and then line up the other side. I hate having to line up two sides simultaneously. (Anyone tried to re-hang a gate by yourself?)

Comments, concerns and criticisms are welcome at this point. It's easy to change a drawing, but the real thing will be a lot harder to change.

Nice Sketchup drawings. I played with that app for a bit....I even imported a
DXF file. I see that you have to pay the $500 upgrade to get it to WRITE
DXF or DWG files. JPGs no problem, as you did.

RE your subframe, the best approach is a 4-pt setup, where the tractor
side is always on the tractor, yet does not interfere with the 3-pt or gives
you lousy ground clearance.

There is a reason you do not see tight-fitting self-aligning mounts like what
you describe. You are asking too much of your mount when it is constraining
in all dimensions. Alignment will have to be perfect before the mating parts
will slide together. With a 4-pt mount, the lower pin/saddle alignment
provides alignment in only 2 dimensions (up/down & left-right), leaving the
rotation angle to be constrained by the top 2 pins. My suggestion is to
go to a tractor dealer and study a commercial TLB, or at least one of the
very modern 4-pt setups.

 

[Iplayfarmer]

Nice Sketchup drawings. I played with that app for a bit....I even imported a
DXF file. I see that you have to pay the $500 upgrade to get it to WRITE
DXF or DWG files. JPGs no problem, as you did.

RE your subframe, the best approach is a 4-pt setup, where the tractor
side is always on the tractor, yet does not interfere with the 3-pt or gives
you lousy ground clearance.

There is a reason you do not see tight-fitting self-aligning mounts like what
you describe. You are asking too much of your mount when it is constraining
in all dimensions. Alignment will have to be perfect before the mating parts
will slide together. With a 4-pt mount, the lower pin/saddle alignment
provides alignment in only 2 dimensions (up/down & left-right), leaving the
rotation angle to be constrained by the top 2 pins. My suggestion is to
go to a tractor dealer and study a commercial TLB, or at least one of the
very modern 4-pt setups.

I'm still considering something like that. All I'd do in that situation is put some kind of a 4 pt. plate on the inch and a half shafts. As I've studied drawings and parts diagrams of the 4 point setups they all tie back to two subrame members anyway.

The other thing I've looked at is tieing into the ROPS higher up somehow. If I did that, I'd want to do it so that I didn't have to drill or weld on the ROPS.

Edit: If anyone has pics of their subframe on their tractor without the backhoe, that would help me a lot in the design process.

 

[GT2]

Good point. I hadn't thought of that. I suppose if 4" isn't going to hold then 12" wouldn't do any better.

I'm assuming that by "plate the sides, top, and bottom of the receivers" you mean to add some metal to the outsides to strengthen it up a bit?

Exactly, Your just thickening the walls of the tubes, and adding meat around the pin holes.
I guess if you already have, like a 1/4" wall receiver you might not have to add plating. Not sure what you have.

 

[Iplayfarmer]

Here's another question to be contemplating while you're evaluating my drawing...

What size hydraulic hose do I need? Planning for the future up to a 8 gpm pump, will 1/4" be big enough hose or do I need to go to 3/8". Are there any online calculators that will tell me this. I'd be running about 2000 psi.

 

[Renze]

8 gallon is 30 liter, according to Google.

I would definately go with 3/8

I run a 32 liter pump on our Zetor, and when i checked the fluid chart in one of my school books, at this volume a 1/2" pressure line and 3/4 return line would be best. (Working lines to cylinders can stay the way they are, at 3/8" )

I did bend a 3/4" hard line to run directly off the pump to the valves but havent got time to install it.

1/4 is definately going to increase the heat buildup and decrease your pump life. 3/8 will do allright but half inch is best to use for the main line that feeds your valve block.

 

[Iplayfarmer]

I'm on to compiling my list of materials. I figure I need about $200 worth of hoses based on Surplus Center prices. I'll be getting a few extra cylinders from them too.

What I'm wondering right now is if there's a good online source for brass washers. I'm planning on using a 1/8" brass washer (shim) in between moving parts just to manage the wear. Is there a place I could just buy a bag of 25 or so brass washers?

I do think I'm going to have a machine shop ream my bushings for me. I'd love to buy the reamer and everything, but I know they'll do a better job.

 

[dfkrug]

I do think I'm going to have a machine shop ream my bushings for me. I'd love to buy the reamer and everything, but I know they'll do a better job.

The need to ream the bushings is not just for the proper ID, but it is to
deal with heat distortion issues you will get form welding. I certainly
needed my long 1.000" hand reamer for my CADDigger project. You can
minimize, but prob not eliminate this distortion by preheating everything.

1/4" hoses work better for the work circuits vs. 3/8". Routing is easier, they
will get pinched less, and the slight restriction they have to 4-8 GPM
flow is desirable. The SurpCntr hoses are very good. I would use 3/8" or
1/2" for the constant flow IN and OUT ports. The biggest restriction to the
constant flow of fluid will likely be thru the AUX valve PB (if you go that
route) and/or the QA connectors. 1/2" QAs will cause less fluid heating
than 3/8". The 3/8" QAs are quite restrictive.

 

[JoelD]

Nice Sketchup drawings. I played with that app for a bit....I even imported a
DXF file. I see that you have to pay the $500 upgrade to get it to WRITE
DXF or DWG files. JPGs no problem, as you did.

RE your subframe, the best approach is a 4-pt setup, where the tractor
side is always on the tractor, yet does not interfere with the 3-pt or gives
you lousy ground clearance.

There is a reason you do not see tight-fitting self-aligning mounts like what
you describe. You are asking too much of your mount when it is constraining
in all dimensions. Alignment will have to be perfect before the mating parts
will slide together. With a 4-pt mount, the lower pin/saddle alignment
provides alignment in only 2 dimensions (up/down & left-right), leaving the
rotation angle to be constrained by the top 2 pins. My suggestion is to
go to a tractor dealer and study a commercial TLB, or at least one of the
very modern 4-pt setups.

I think DF's advice is excellent, I sorted out my subframe by getting the manual for my tractor's factor backhoe frame mount and then I copied it.

My subframe used the bottom pins for the three point and then I tied into the loader cross member in the middle of the tractor.

The one thing you must not loose sight of is how you plan to get the backhoe on and off of the tractor. You can not make it in such a way that you need to precisely line anything up, otherwise you'll be spending hours with jacks and blocks trying to get things to line up. Definately study factory set ups and then copy the one that looks closest to what you've got.

Joel

 

[Iplayfarmer]

The need to ream the bushings is not just for the proper ID, but it is to
deal with heat distortion issues you will get form welding. I certainly
needed my long 1.000" hand reamer for my CADDigger project. You can
minimize, but prob not eliminate this distortion by preheating everything.

1/4" hoses work better for the work circuits vs. 3/8". Routing is easier, they
will get pinched less, and the slight restriction they have to 4-8 GPM
flow is desirable. The SurpCntr hoses are very good. I would use 3/8" or
1/2" for the constant flow IN and OUT ports. The biggest restriction to the
constant flow of fluid will likely be thru the AUX valve PB (if you go that
route) and/or the QA connectors. 1/2" QAs will cause less fluid heating
than 3/8". The 3/8" QAs are quite restrictive.

Thanks for raining on my parade. But, seriously, that's the kind of advice I want to hear now vs. after I'm half way through the build.

So, let me ask you this... Did you ream before and after, or just after? I guess what I really want to know is if having the machine shop do the reaming will make the hand reaming I have to do after welding easier.

 

[Iplayfarmer]

1/4" hoses work better for the work circuits vs. 3/8". Routing is easier, they
will get pinched less, and the slight restriction they have to 4-8 GPM
flow is desirable.

I forgot to ask this in the last reply...

Why do you say the slight restriction is desirable? Is it just a speed issue?