Tractor backhoe - homemade

[BFreaky]

Square tubing is the past. With curved boom design you get light but strong boom and it looks alot better. Well I could post cad drawnings, but the size of this machine would not suit your needs... It's not all that hard to draw it, these are simple 2D drawnings. First of all you need to determine boom lenght you want to build, then you can design everything else.

 

[Renze]

Bfreaky, how are you going to make the upper and lower plate of the boom in a curve ? have them rolled, or just clamp 4 or 5mm plates against the vertical, laser cut, curved plates with strong vise grips ?

 

[BFreaky]

Bfreaky, how are you going to make the upper and lower plate of the boom in a curve ? have them rolled, or just clamp 4 or 5mm plates against the vertical, laser cut, curved plates with strong vise grips ?

I will take them to a nearby shop and have them cold rolled. Then I will weld one end and clamp&weld them step by step.
Plates at dipper and boom swing connection will be made out of 25 mm metal. Similar to the drawning at the 1. page of this topic.

 

[Renze]

I will take them to a nearby shop and have them cold rolled. Then I will weld one end and clamp&weld them step by step.
Plates at dipper and boom swing connection will be made out of 25 mm metal. Similar to the drawning at the 1. page of this topic.

Yes, but the main boom profile, what material thickness did you take ? I would love to see how you end up tacking the boom profile together, i mean, what turns out the most practical way...

 

[BFreaky]

Yes, but the main boom profile, what material thickness did you take ? I would love to see how you end up tacking the boom profile together, i mean, what turns out the most practical way...

Vertical plates will be made out of 6 mm (maybe even 8 mm), and horizontal out of 10 mm. Maximum reach on the end of the bucket wil be 5.5 meters (measured from the center of king pin) so I think it's necessary to put thicker material. Also, sadly, it won't be made out of Domex because it's too expensive here...

 

[allen6634]

Another possibility is to offer the plans and all the parts as a complete do-it yourself kit. Similar to what EA has been talking about doing with their attachments. I would imagine with a well designed backhoe and website you would be able to sell a number of kits every year. I bet there are members here who would be interested in such a kit. I realize this would be a lot more work than simply selling your plans. You'd have to run the numbers and see what would be more profitable plans or kits or maybe both.

i know that i would be interested in a kit, because finding the steel and having it cut would make it more trouble than it would be worth.

 

[Renze]

Vertical plates will be made out of 6 mm (maybe even 8 mm), and horizontal out of 10 mm. Maximum reach on the end of the bucket wil be 5.5 meters (measured from the center of king pin) so I think it's necessary to put thicker material. Also, sadly, it won't be made out of Domex because it's too expensive here...

So you stick with St.52.3 (or S355 ??)

Thats half the strength of Domex 700 or Naxtra 70. So you need double the material thickness than a Takeuchi excavator boom made out of these high strength steels. Estimating from the bend radius of the boom of 3t excavator booms, i guess they are made of 4 to 5mm steel, so your 8 to 10mm should be about right...

 

[BFreaky]

So you stick with St.52.3 (or S355 ??)

Thats half the strength of Domex 700 or Naxtra 70. So you need double the material thickness than a Takeuchi excavator boom made out of these high strength steels. Estimating from the bend radius of the boom of 3t excavator booms, i guess they are made of 4 to 5mm steel, so your 8 to 10mm should be about right...

Yes, it will be St52.3, nothing less than that. I'm still negotiating about Domex 550 MC...there is one sheet which could go at a smaller price....but don't know yet...it all depends on the seller. The idea is to make the boom as light as possible...but not too expensive. Buckets will be made out of Hardox 500, that's already arranged

 

[dfkrug]

Square tubing is the past. With curved boom design you get light but strong boom
and it looks alot better.

I agree! A "box beam" of thinner steel can be made quite a bit stronger than a "dimensional beam",
and weigh a lot less.

I think you can make a very strong boom out of 1/8" (3+mm) mild steel, like A36, with laminated
sections around all the pivot points. You CNC-cut the sides out of a full plate, then stitch-weld the top and
bottom out of, say 4 or 5" wide plate. Easy to bend, manually, as you add each weld.

Keep up the good work.

 

[BFreaky]

I agree! A "box beam" of thinner steel can be made quite a bit stronger than a "dimensional beam",
and weigh a lot less.

I think you can make a very strong boom out of 1/8" (3+mm) mild steel, like A36, with laminated
sections around all the pivot points. You CNC-cut the sides out of a full plate, then stitch-weld the top and
bottom out of, say 4 or 5" wide plate. Easy to bend, manually, as you add each weld.

Keep up the good work.

That's true, but I think 3 mm is not strong enough...reach of the backhoe from swing point to the tip of the bucket teeth will be 5.5 m, that's 18 feet...
It has to be stronger or it could bend. Main boom cylinder develops a force of 20.72 tonnes at 200 bar of pressure. I can't go under 6 & 10 mm plates...

 

[CanuckPT]

One more voice adding to the appreciation of the incredible design & execution you are performing! I truly appreciate in others skills that I do not possess! I know we all have our niches in life (professionally & with recreational pursuits) and I'm proud of the skills I do have but man do I ever love to watch these fabrications unfold before my eyes in threads like this as well as 4Shorts thread on his BX25 mods!! Keep it coming!!!

 

[traktorz]

Tractor backhoe questions

1.
I'm curious to know if your going any standarsized route with respect to the bucket mount.

I can tell that in Sweden, today even the very small digging machines get a standadized quick attach mount, S30 up to S120, where the digits indicates the diameter of the attaching pins, 30mm up to 120 mm. Some of the smaller do come in various pin lengths, S30/150 and S30/180, 150 or 180mm. I'm not sure how widely spread this standard is within EU though.

2.
I anticipate you're going to run the backhoe from the tractors main seat, since frequent hopping between the backhoes seat and the tractors seat is a pain, especially with our small Chinese made backhoe. I didn't see any footsteps on your structure, so I guess you have the valve block remotely operated from the backhoe.

3.
Another pain with the Chinese made backhoes is the Metric Thread O-ring Flat Seal Hydraulic Hose Fittings (Chinese standard), since their press fittings are very rare in the western world.

Here I'm curious of your choice of standards for all the backhoes hydraulics. Maybe your choice of reusing old cylinders has already set your choice?

4.
Regarding restrictors and flow control, for our Chinese backhoe the hydraulic hose for lowering the boom has a restrictor at the cylinder port.

Here I'm curious what functions your are trimming the hydraulic behaviour of. Maybe the boom swing near the end positions need some flow control too? Will you allow 180 degrees boom swing?

Ref:
♦ Symmetriska snabbfästen för grävmaskiner (S-standard).
http://www.maskinleverantorerna.se/...rdisering snabbfasten slutrapport 2011-06.pdf
♦ ENGCON Quick hitch
http://engcon.se/en/engcon.html

CHINESE TRACTOR WORLD FORUMS - The Achilles heel of Chinese Backhoes
CHINESE TRACTOR WORLD FORUMS - LW-7 BH
http://www.tractorbynet.com/forums/chinese-tractors/213751-metric-thread-o-ring-flat.html

 

[dfkrug]

That's true, but I think 3 mm is not strong enough...reach of the backhoe from
swing point to the tip of the bucket teeth will be 5.5 m, that's 18 feet...
It has to be stronger or it could bend. Main boom cylinder develops a force of 20.72 tonnes at 200 bar of
pressure. I can't go under 6 & 10 mm plates...

18 feet?! That's beyond even BT1200 territory (M59 photo). I will bet that the boom section in the photo,
where the big 'KUBOTA' logo is, has plate thickness of no more than 3/16"....

 

[Renze]

18 feet?! That's beyond even BT1200 territory (M59 photo). I will bet that the boom section in the photo,
where the big 'KUBOTA' logo is, has plate thickness of no more than 3/16"....

Thats 4.7mm. If its Domex 700 or Naxtra 70 or any other high strength steel, you need double the thickness in S355, or triple the thickness in standard construction steel S235...

...However... I doubt they make backhoes like these out of Domex because the filled welding wire required to weld these steels at strength, increase the cost of a tractor backhoe too much. Perhaps full size excavators have Domex booms..

Bfreaky, have you done strength calculations, or just the cylinder force ? Calculating the moment of inertia of the beam, and compare that with the cylinder force, it would make it pretty easy to tell if these booms are made of St.52.3 or Domex 700 or even Xabo 1100 (which is so exotic that its only used for high end telescopic cranes)

 

[Renze]

Re: Tractor backhoe questions

I can tell that in Sweden, today even the very small digging machines get a standadized quick attach mount, S30 up to S120, where the digits indicates the diameter of the attaching pins, 30mm up to 120 mm. Some of the smaller do come in various pin lengths, S30/150 and S30/180, 150 or 180mm. I'm not sure how widely spread this standard is within EU though.

No, its not a Europe wide system, perhaps a Scandinavia wide system. In Holland we use the Verachtert system as an industry standard. Now the patents have expired, everybody is making them.
Connect'o'maat / quick coupler | Verachtert

 

[BFreaky]

Re: Tractor backhoe questions

....? ..

1. No, since this is a prototype and it's intended for my personal use, I will make my own kind of quick coupling. After all, I will fabricate all the buckets by myself so there is no actual need for standard quick attach.
Pin size is already determined, it will be 45 mm in diameter except for the king pin which is 60 mm.

2. No, the backhoe will have it's own seat. There are several reasons for that. Main one is the inner side of tractor cab construction. Behind the seat there is a battery compartment and all the wiring, so I decided not to change that because I have no other place to put all that. The other problem is the rear cab window..it opens only 45 degrees so the frame comes in the middle of operators field of view.


3. I will use standard 1/2, 3/4 and 1" fittings and tubes. All the cylinders will get new inlets with 1/2 G thread.

4. The boom swing will have flow control valves because I've calculated the speed of cylinders and it needs to be slowed down. I'm not sure yet which type valve would be the best for this task, so any suggestons are very welcome.


Renze

No, I've just calculated cylinder strenght, cycle times and oil capacity for each one. I will use only St 52.3. I believe 6 and 10 mm would hold it all together without problems. If we compare mechanical properties of St 52.3 and Domex 550 MC it's not souch a big difference as it is in the price per kg... Maybe ST E460 is a better choice ..?

 

[Renze]

The biggest advantage of Domex is its constant material thickness, so you can make much more exact bends: I've worked for a company that made concrete moulds, they once sent a batch of 4mm plates back to the supplier because there was 0.2mm difference in thickness in the length of the plate, due to differences in the mill rolling process.

Next to that, they are rolled in both directions so the plates are equally strong in both directions. Standard plates are stronger in the rolling direction, in the length of the plate. Also they are stronger when you weld things to the surface, because a heat treatment reduces the carbon content to round bubbles, where as in normal steel, the carbon is laminated: the plates crack along these laminations when you weld a hook to it and pull...

Those are the reasons Domex is more expensive. The yield strength also depends on the material thickness, heavy plates of St.52.3 just have a yield strength of 355N/mm2, thin plates have the mentioned higher yield strengths.

Is the St E460 cheaper because it is milled unidirectional ? there should also be St E690 i believe, though we never use it.

 

[lhansman]

I can only echo the main compliments on your design and fabrication abilities. However and backhoe with a reach of 5.5m (18') is more than most full size rubber tired backhoes that do not have an extendable stick. From you drawings it looked like just a boom and stick - not an extend-a-hoe. What weight and horsepower are your Belarus tractor?

I look forward to watching the completion of this project.

Regards,

Lauren

 

[ericher69]

Are these European standard names for different grades of steel?

If so what would be the equivalent in North America ( for anyone that can answer)

 

[RobertBrown]

What weight and horsepower are your Belarus tractor?

TractorData.com Belarus 920 tractor information