Beam needed for 20 ft 3 pt hitch seed drill

[Jmsteel]

I am looking to build a 3 point hitch air seeder. My plan is to build it 20 feet long with the hitch in the middle. The openers will be a disc opener with a 450 lbs trip which I am planning to space them at 6 inches. As the openers are built to attach to a 4x4 box steel beam, I am wondering if it would be possible to have that much force on the beam without bending?

 

[ChemAir]

Can you show a diagram with the beam, the locations of the three support points, and the loads over the beam width? And if there are additional supports/wheels, etc.

Also, there are more than one kind of 4x4 box steel. What thickness are you looking at?

 

[berkeman]

I am looking to build a 3 point hitch air seeder. My plan is to build it 20 feet long with the hitch in the middle. The openers will be a disc opener with a 450 lbs trip which I am planning to space them at 6 inches. As the openers are built to attach to a 4x4 box steel beam, I am wondering if it would be possible to have that much force on the beam without bending?

Welcome to the PF.

Are you asking about something like this?

http://static.auctionservices.com/images/689053/John_Deere_515_Grain_Drill_large.jpg

 

[Jmsteel]

Welcome to the PF.

Are you asking about something like this?

http://static.auctionservices.com/images/689053/John_Deere_515_Grain_Drill_large.jpg
View attachment 223753

Yes, very similar but the grain box would be something similar to this in the middle.
https://www.fennigequipment.com/images/product-images/1655_Valmar_Aerway_Mount_400.jpg

I was thinking more along this design.

 

[JBA]

I think we need to know more about the "disc openers with a 450 lb trip". How do the openers operate and how would their tripping force affect the beam?

In reality, we really need to see a conceptual drawing or sketch of the whole unit you are planning to build.

 

[256bits]

I am looking to build a 3 point hitch air seeder. My plan is to build it 20 feet long with the hitch in the middle. The openers will be a disc opener with a 450 lbs trip which I am planning to space them at 6 inches. As the openers are built to attach to a 4x4 box steel beam, I am wondering if it would be possible to have that much force on the beam without bending?

Just refresh a bit.
The 450 pound trip is what?
The supposedly maximum rearward force on a disk set from an obstacle in the ground?
Spring loaded ?
If all disc(s) encounter an obstacle?

beam 4 inch, thickness ??, material steel??

How much soil penetration force - is that to be provided by the weight of the machine, along with the 3-point hitch.
That will depend upon the soil compactness, and the end disc( s) could have a problem if the soil is not loose enough.
End disc(s) may seed at a different ( less ) depth than right behind the 3-point.

There will be vertical as well as a horizontal force on the beam, and both should be looked at in regards to the beam's rigidity.

 

[Jmsteel]

Just refresh a bit.
The 450 pound trip is what?
The supposedly maximum rearward force on a disk set from an obstacle in the ground?
Spring loaded ?
If all disc(s) encounter an obstacle?

beam 4 inch, thickness ??, material steel??

How much soil penetration force - is that to be provided by the weight of the machine, along with the 3-point hitch.
That will depend upon the soil compactness, and the end disc( s) could have a problem if the soil is not loose enough.
End disc(s) may seed at a different ( less ) depth than right behind the 3-point.

There will be vertical as well as a horizontal force on the beam, and both should be looked at in regards to the beam's rigidity.

Ok so here is a link to the openers I was thinking of using as I can find a few used to cut costs.
https://www.bourgault.com/product/e...-25-mrb-ii-fertilizer-application-system.aspx

These are spring loaded and I would not think all discs would hit an obstacle at the same time, but more likely the right (or left) end ones hit an obstacle and the rest do not.

The beam thickness is basically the question I am looking for answers on. I would think 1/4 inch thickness would be enough from other prictures I have seen, but am not sure.

ground penetration force, I am not certain but our current air drill has similar trips with 4 inch boot openers (4 inch wide that come to a cutting point) and they do not trip very often.

I understand depth issues maybe a problem however, that would be set by 3 point hitch level and tractor wheels. There are not many hills to change depth levels on my land.

 

[JBA]

As per ChemAir's (#4 post) we still have to know the locations (w/ dimensions) of the carrying connections on this cross bar.

Also, for the sake of a reasonably safe stress analysis of the beam some estimate of the expected soil resistance operating load on the operating discs at the time one of the discs hits an obstacle and experiences the 450 lb trip loading; otherwise the only safe analysis is one that assumes a simultaneous 450 lb load on all discs (which I admit is an overkill).

 

[Jmsteel]

So to reply to the chemair questions

The beam would be 20 front sure on thickness but hoping 1/4 inch would work.
The hitch would be 4 ft wide and centred on the beam. This would leave 8 ft on either side.
Spacing for discs I was thinking 6 inches but could go to 7.5 if needed.

I hope this clarifies things more.

 

[256bits]

I understand depth issues maybe a problem however, that would be set by 3 point hitch level and tractor wheels. There are not many hills to change depth levels on my land.

Kudos. Flat land is a definite bonus.

For the seeder, I was getting at consistent depth penetration for all openers across the span.
Some design considerations.
the penetration into the soil is either from the weight above the disc(s).where the hydraulic cylinder only supports some weight and the soil supports the balance.
Or an active penetration with a double acting cylinder which can push the disc(s) into the soil.
The first scenario necessitates a heavy enough machine.
for the second, a much lighter machine is possible.
One does not want the ends to droop, or flex upwards.

In either case a desire is to have across the span some minimum vertical deflection ( fractions of inch ) so that all openers penetration to the same extent into the soil.
Vertical rigidity required.

The horizontal deflection is not as critical. One could make due with inches of span deflection which would not affect the row spacing drastically.

Saying that though, one does not want the walking effect where each side of the beam from the centre shimmies back and forth. Also not affecting the row spacing per pass, but very annoying. This does have an affect upon passes being straight rather than curvy which could result in overlap and non optimum spacing between intervals of the paths.
Horizontal deflection should be minimized.
Horizontal rigidity required.

Since the beam is some feet from the ground, the openers in operation will produce a torque on the beam. Due to the torque, and it is accumulative with each opener, if say centre openers are vertical, moving towards the end of the span each opener will be at an angle to the ground meaning that they will be lesser and lessor depth than that at the centre.
Torsional rigidity required.

Of the three requirements, vertical and horizontal can be addressed with bracing. along the length of the beam.
The torsional deflection can also be addressed with bracing at selected points involving vertical members extending from the beam and having the ends of the extensions connected by wire, or stiff rods back to the 3-point hitch.

with all that bracing, it comes down to the original question of yours.
Could a simple box bean entertain all design requirements? ( without all that bracing )
What size beam?The 3-point hitch can be modeled as just a drawbar at the centre of the span for the horizontal forces, stresses and deflections.
Same for the vertical - a central force counteracting the vertical forces from the openers.
Torsional forces on the beam from the openers would be counteracted by the 3-point hitch.

Some simple beam loading apps on the internet might be able to help you out.
Otherwise hand calculations is it.

 

[Jmsteel]

Thank you that is exactly the issue. Any suggestions for reliable online calculators?

Kudos. Flat land is a definite bonus.

For the seeder, I was getting at consistent depth penetration for all openers across the span.
Some design considerations.
the penetration into the soil is either from the weight above the disc(s).where the hydraulic cylinder only supports some weight and the soil supports the balance.
Or an active penetration with a double acting cylinder which can push the disc(s) into the soil.
The first scenario necessitates a heavy enough machine.
for the second, a much lighter machine is possible.
One does not want the ends to droop, or flex upwards.

In either case a desire is to have across the span some minimum vertical deflection ( fractions of inch ) so that all openers penetration to the same extent into the soil.
Vertical rigidity required.

The horizontal deflection is not as critical. One could make due with inches of span deflection which would not affect the row spacing drastically.

Saying that though, one does not want the walking effect where each side of the beam from the centre shimmies back and forth. Also not affecting the row spacing per pass, but very annoying. This does have an affect upon passes being straight rather than curvy which could result in overlap and non optimum spacing between intervals of the paths.
Horizontal deflection should be minimized.
Horizontal rigidity required.

Since the beam is some feet from the ground, the openers in operation will produce a torque on the beam. Due to the torque, and it is accumulative with each opener, if say centre openers are vertical, moving towards the end of the span each opener will be at an angle to the ground meaning that they will be lesser and lessor depth than that at the centre.
Torsional rigidity required.

Of the three requirements, vertical and horizontal can be addressed with bracing. along the length of the beam.
The torsional deflection can also be addressed with bracing at selected points involving vertical members extending from the beam and having the ends of the extensions connected by wire, or stiff rods back to the 3-point hitch.

with all that bracing, it comes down to the original question of yours.
Could a simple box bean entertain all design requirements? ( without all that bracing )
What size beam?The 3-point hitch can be modeled as just a drawbar at the centre of the span for the horizontal forces, stresses and deflections.
Same for the vertical - a central force counteracting the vertical forces from the openers.
Torsional forces on the beam from the openers would be counteracted by the 3-point hitch.

Some simple beam loading apps on the internet might be able to help you out.
Otherwise hand calculations is it.

 

[JBA]

Jmsteel,

I n order to give you a bit of assistance with formulas, below is a screen print from an excel sheet for the beam stresses and deflections on one arm for the tripping load on a single drill for two conditions. The first is for a full vertical tripping load and the second is for the torsional stress of a full tripping load with a full frontal strike on the drill disc. The actual total arm stress for the second case would be some combination of the first bending stress combined with the torsional shearing stress. The first calculation represents the maximum condition for any single disc strike on any of the discs on the arm based upon the drill's distance from the hitch structure; but, the second calculation torsional stress,but not the angular deflection, will be the same for all discs on the arm.

Maybe these examples will give you a start and the equations required for calculating the stresses and deflections for these two conditions; even so, all of the factors and appropriate combinations of loads as discussed above by 256bits still must be determined for a complete design analysis.