Backhoe Design Ideas

[charlz]

The b670 on my b7100 runs off a pto pump... pretty sure it is in the 4-5 gpm range and I run it about mid-rpm's any more than that (or if you try using as different pto speed) and it tends to make the hoe slam around a bit.

My front end loader runs off a similar sized pump on the front pto.

It definitely is a little slow when trying to scrape a flat bottom but most of the time you are using bucket curl with a little crowd to remove max dirt and speed is fine. I would like stronger swing cylinders and in fact I just repacked them so we will see how much of a difference that makes. All the cylinders are in the 2.0 to 2.5 range.

The shorter the reach the more often you have to re-position when trenching. A 5' trench with my 6' hoe would be pretty slow going with lots of repositioning.

I believe I have posted various pics of my hoe so if you search through my posts you should be able to find them.

If your ever in the Boise area and want to dig some holes to get a feel for this size hoe let me know

 

[dfkrug]

The curved boom is now the standard. Its advantages include digging deeper and closer to the machine, more compact, stronger, and better aesthetics.

Yes, curved is now the standard. The Kioti KB2475 is a much improved
hoe, in every way EXCEPT for the forces it delivers (and the price I am sure).
The new hoe is now beefier and offers seat-accessible transport locks for the
boom AND the outriggers. TYM has the same hoe, but it does not deliver
greater dipper digging forces over the old KB2375.

 

[Iplayfarmer]

Yes, curved is now the standard. The Kioti KB2475 is a much improved
hoe, in every way EXCEPT for the forces it delivers (and the price I am sure).
The new hoe is now beefier and offers seat-accessible transport locks for the
boom AND the outriggers. TYM has the same hoe, but it does not deliver
greater dipper digging forces over the old KB2375.

I like the look of the curved boom. If it's becoming the new standard, I guess that the benefits are generally outweighing and drawbacks.

 

[JoelD]

That calculator is a neat thing. So my bucket cylinder using 24 inch stroke will only take 3.9 seconds to extend and 2.4 seconds retract. Thats with a 2" cylinder and 5GPM pump. For my needs that will be pretty fast. We are talking homemade backhoes. Note the one on the Harbor Freight site has a 2.5GPM pump. With the same pump a 6inch cylinder would take 34 seconds to extend so yes that would be slow.

I ran my caddigger on about 5 gpm or so and was too fast for my budies to have any fun with as it was jerky for them. I had many hours on the machine and was used to it, I did install drilled out blunt fittings though to slow the swing a little.

My 628 was not the large version, 5 foot digging depth, so the cyls. were not big, but the 5 gpm was more than enough for me.

I ran a pump off the PTO, which I built up a mounting bracket for. My tractor only put out about 2 gpm or so for the 3 pt.

Joel

 

[JoelD]

Where are you finding used PTO pumps for $100? If I could find that kind of a deal, I might just go with it.

One of the reasons I'm thinking of going with the mid PTO is that I may convert the loader to run off it too. I have nothing else that I'm running off the mid PTO, and I'd probably just disable the seat safety and leave it hooked up permanently. Then I could use the rear PTO for the tiller or bush-hog without needing to remove the loader.

As far as clearance goes, I'll have to measure. I'm already pretty low due to mounting the Loader subframe under the front wheel drive shaft. The surplus center pumps are about 5 inches, and I think I'd have the clearance. The only thing I'm still unsure of is how to adapt from the splined shaft of the mid PTO to the Pump.

I suppose I could figure my onboard pump output by timing my loader arms. What's a typical time for a backhoe boom cylinder to fully extend or retract?

For about a 100 I bought a pump from surplus, used a coupler to couple to my PTO shaft and then welded up a bracket for it to line up with the PTO shaft and keep the pump from spinning. Never a problem in approximately 3 years of use. No need for a dedicated PTO pump, those things are big money.

Joel

 

[Iplayfarmer]

For about a 100 I bought a pump from surplus, used a coupler to couple to my PTO shaft and then welded up a bracket for it to line up with the PTO shaft and keep the pump from spinning. Never a problem in approximately 3 years of use. No need for a dedicated PTO pump, those things are big money.

Joel

Okay, now that makes sense. I thought you were getting a dedicated PTO pump for $100. I was ready to offer we go into business together.

I did some figuring on my tractor by timing the loader. I timed the loader lift and curl cylinders extending and retracting, and in all situations I calculated I'm getting about 3 GPM. Then I went to YouTube and timed a bunch of different mini backhoes as they moved around. I'd watch a video until I saw a full retraction or extension of a cylinder, then back it up and time it while I replayed it. Based on my calculations with the cylinders I have, I'll be about the same speed as most of these mini hoes. I may be a little slower, but not much.

I did make one decision, though. I have a matched set of 2 3/4" cylinders that I was going to use for the boom and dipper; but based on my calculations, I think I'll try to trade them for 2" cylinders. It cuts the extend time from 8.2 seconds to 4.4 seconds. I think that the speed will be more useful than the force.

 

[john_bud]

Okay, now that makes sense. I thought you were getting a dedicated PTO pump for $100. I was ready to offer we go into business together.

I did some figuring on my tractor by timing the loader. I timed the loader lift and curl cylinders extending and retracting, and in all situations I calculated I'm getting about 3 GPM. Then I went to YouTube and timed a bunch of different mini backhoes as they moved around. I'd watch a video until I saw a full retraction or extension of a cylinder, then back it up and time it while I replayed it. Based on my calculations with the cylinders I have, I'll be about the same speed as most of these mini hoes. I may be a little slower, but not much.

I did make one decision, though. I have a matched set of 2 3/4" cylinders that I was going to use for the boom and dipper; but based on my calculations, I think I'll try to trade them for 2" cylinders. It cuts the extend time from 8.2 seconds to 4.4 seconds. I think that the speed will be more useful than the force.

I dunno - I had a guy offer me a rear pto pump for $100 just about 6 months ago. Didn't need it. Craigslist and eby have them on occasion at that price.

You should calculate the forces with the different cylinder sizes. It stinks to get a full bucket and not be able to lift it or place it.

jb

 

[JoelD]

The pump really is the key, another thing you need to think hard about is the relief valve preasure on your tractor's pump. My little tractor was running somewhere south of 2000psi. I needed closer to 3000 for my backhoe, that was another reason for mounting up the PTO pump. Another reason for me was I did not want to run the wear and tear on my tractor's pump, big money to replace. Yet another reason was my tractor's oil capacity was not quite enough, when running the backhoe I think the oil would've gotten too hot.

I found a number of advantages of keeping the oil system seperate from my tractor.

Joel

 

[JoelD]

Here's some pictures.

 

[Iplayfarmer]

I dunno - I had a guy offer me a rear pto pump for $100 just about 6 months ago. Didn't need it. Craigslist and eby have them on occasion at that price.

You should calculate the forces with the different cylinder sizes. It stinks to get a full bucket and not be able to lift it or place it.

jb

I'll have to keep my eyes open for a pump. The new cylinders will cost almost $200. I suppose if I can get a pump with 5-8 GPM flow for that price it would be a better option.

In the mean time, I'm back to designing the actual structure of the backhoe. I'm going with the curved boom.