Cost estimation of large size rack and pinion using a lead screw

[MechEn9ineer]

TL;DR Summary

Evaluation of concept idea for lifting 750 ton using rack and pinion combined with lead screw

Hi everyone,

I am in concept phase of designing a lifting mean for 750 ton, I have many ideas using hydraulics which I could cost estimate online. However, one of the ideas is using rack and pinion combined with lead screw with its sizes determined from rough stress calculations. So, does anyone have an idea how to cost estimate the following?

1) Screw and nut
- Diameter = 160 mm
- Length < 1 m
- Lead angle = 10 degrees
- Yield stress > 235 MPa

2) Rack and Pinion
- Module = 40
- No. of teeth = 10
- Pinion thickness = 200 mm
- Pressure angle = 20 degrees
- Rack Length = 8 meter
- Yield stress > 235 MPa

 

[jrmichler]

Is this a homework problem? Because it looks like one. If so, we can move it.

BTW, some very quick calculations show that your design cannot possibly work.

I am not aware of any good ways to cost estimate machine parts that are far removed from standard production parts. That's because the cost is a function of the capability of the particular machine shop, your design specifications and tolerances, and their willingness to do the job.

 

[Baluncore]

Welcome to PF.

A rack and pinion is not a sensible solution to a 750 tonne problem. Everything is working against it. No mechanical advantage is gained by a rack and pinion. The pinion caries the total load on one tooth. The pinion must be wide and perfectly aligned with the rack. To get greater tooth area in contact, the pinion evolves to be an acme nut, while the rack becomes an acme screw, which makes it a screw jack.

The biggest vertical-axis screw jacks, available off-the-shelf for industrial applications, have an acme thread that does not rotate. The acme nut is internal to the housing, in the form of a worm wheel, driven by a horizontal-axis worm screw. IIRC, the ones I used were limited to one hundred tonnes. It seems hydraulics has taken over by about 1000 kN ≈ 100 tonnes
https://www.powerjacks.com/products/screw-jacks

For 750 tonnes, the obvious solution is hydraulic.

 

[MechEn9ineer]

Is this a homework problem? Because it looks like one. If so, we can move it.

BTW, some very quick calculations show that your design cannot possibly work.

I am not aware of any good ways to cost estimate machine parts that are far removed from standard production parts. That's because the cost is a function of the capability of the particular machine shop, your design specifications and tolerances, and their willingness to do the job.

Hi Jrmichler,
It is not a home work, it is an acutual adjustment to spmt (Self-propelled modular transporter) with two saddles lifting 1500 T wind turbine monopile.
Thanks for the answer, it is unpractical idea but if cost was way less than hydraulics then I would try to go further with it.

 

[MechEn9ineer]

Welcome to PF.

A rack and pinion is not a sensible solution to a 750 tonne problem. Everything is working against it. No mechanical advantage is gained by a rack and pinion. The pinion caries the total load on one tooth. The pinion must be wide and perfectly aligned with the rack. To get greater tooth area in contact, the pinion evolves to be an acme nut, while the rack becomes an acme screw, which makes it a screw jack.

The biggest vertical-axis screw jacks, available off-the-shelf for industrial applications, have an acme thread that does not rotate. The acme nut is internal to the housing, in the form of a worm wheel, driven by a horizontal-axis worm screw. IIRC, the ones I used were limited to one hundred tonnes. It seems hydraulics has taken over by about 1000 kN ≈ 100 tonnes
https://www.powerjacks.com/products/screw-jacks

For 750 tonnes, the obvious solution is hydraulic.

Totally agree, clearly explained!

 

[Uncanny3]

-so gear the hydraulics down,
lift it slowly
...very many pistons/cylinders
can lift it with gear boxes and hydraulic pumps
I've seen 1000 kg on one piston

you will have to lift and lift that, wherever you're going with it
wow!

 

[Tom.G]

On an associated subject, the Port of Long Beach in California is planning a new pier where LARGE wind turbines can be assembled, then towed to the NorthWest coast of the USA. Up there the wind is particularly strong, reliable, and peaks in the late afternoon/evening, around peak usage hours.

The project consists of dumping much dirt/rocks in an unused area of the harbor and renting assembly areas to various turbine manufacturers... and it is adjacent to the deep-water port entrance, which is inside a massive breakwater. (The port originated as the home of the U.S. Navy West Coast Fleet, which moved to San Diego many years ago.)

They expect about 2 years to build each turbine.

This is still in the planning and environmental impact stage but the locals seem enthusiastic or at least accepting.

https://polb.com/port-info/news-and...event-on-ports-pier-wind-proposal-01-08-2024/

Cheers,
Tom

 

[Uncanny3]

if I understand right this heavy industrial proposal(and the experience here of others is more relative I'm, sure),
you may have to create linear bearings of some sort for the hydraulic lifter,
I'm not sure what they are most forthrightly. -if this is the next part of the problem.
it seems we need to lift <1 meter. They can be rollers of fat sort on columns of some kind non-specifically. Does anyone have a more direct linear bearing? -wishing success

edit: I thought of a slot, and is it lifted from underneath or on chain from above(as my inexperienced thought led)?

-yah hydraulic A-frame, lifting on chains(or straps) from above, with a series of immensely tank slots for central linear bearing at the apex -the thought. Collars on the ram's end rose joint location, holding it onto the many slots(as many slots as opposing rams(or 4 per ram pair, alternately). Triangular crane cross bracing (perpendicular to the A-frames), to stop the immense axial tilt, which wants to go parallel to the pole, and domino the A-frames . I think with difficulty that could work, building a structure. If this was multiple you could re-use the structure, otherwise, the lift costs a number of strong A-frame truss, axial cross bracing, unarguably strong slots and the mighty rams, which are synchronized or minutely stepped

My edit takes in Tom's comment, that yes, I have seen somewhat such straps used. A very strong material for them is polyester for one of the woven materials

 

[Tom.G]

...is it lifted from underneath or on chain from above(as my inexperienced thought led)?

Rather than chains, heavy lifts are often done with synthetic fabric straps. This avoids the concentration of force you get from the smaller contact area of chain links.

Cheers,
Tom

 

[gmax137]

Is the task to lift it up and onto the transporter, or is it to pick it up off the transporter?

 

[Baluncore]

My edit takes in Tom's comment, that yes, I have seen somewhat such straps used. A very strong material for them is polyester for one of the woven materials

We use Kevlar, inside a woven polyester sleeve, that protects the Kevlar fibres.

 

[MechEn9ineer]

Is the task to lift it up and onto the transporter, or is it to pick it up off the transporter?

The task is to lift it 500 mm while transportaion on the SPMT so the task here is not picking it up.

 

[Uncanny3]

could you use a multiplicity of joined heavy jack units(there may be some product)? -perhaps

 

[MechEn9ineer]

So far I am thinking of four cylinders per each saddle with pinned end connection to relief rods from reaction moments (sketch attached but without accurate relative dimensions). Also for the hydraulic circuit I will add LHV (Load holding valve) with a directional valve to ensure safety and provide flexible heights.

I don't have experience in lifting, so I would like to know your opinions on drawbacks of this approach and your recommendations.

Reflecting back on estimating the large gear prices for the firstly unfavorable idea, I tried statistical regression from prices available online for other gears sizes and I got a strong correlation to predict large gear prices using two variables (volume (reflecting material cost) and circular pitch (reflecting machining cost)). Still I will go with hydraulics forsure.

 

[Ranger Mike]

You said - I am in concept phase of designing a lifting mean for 750 ton, I have many ideas using hydraulics which I could cost estimate online. ok. is this the problem statement?

It is not a home work, it is an acutual adjustment to spmt (Self-propelled modular transporter) with two saddles lifting 1500 T wind turbine monopile.
Thanks for the answer, it is unpractical idea but if cost was way less than hydraulics then I would try to go further with it.

Just consider Work = Force times Distance = Energy
Being an old race car builder, look at the factors in the equation, regardless of the method you decide.
The mechanism will have to be anchored so it does not rip out if the mass is too great. This is then nil in the cost equation.
This leaves force required times a distance. In this case Area. How much tooth area is required to equal the same area of a pulley? What is more commonly available on the market ? Pulley or custom rack and pinion with tooth area to be able to do the work? Big cost difference. Next look at the power required to move linear rack and pinion versus the force multiplier of the multi pulley system.
The idea of a simple machine originated with the Greek philosopher Archimedes around the 3rd century BC, who studied the Archimedean simple machines: lever, pulley, and screw. He discovered the principle of mechanical advantage in the lever.

Simple is always best...

built the pyramids

Ancient Technology of the Pyramid Builders: The Proto-Pulley | Ancient Architects We look at the pyramids of Egypt and the enormous stone blocks that make up the core masonry, and even though there are some great explanations for how it was done, such as the work of architect Jean-Pierre Houdin, who has studied every detail of the Great Pyramid for the past 22 years, many of us still can’t fathom how such blocks of stone ... www.youtube.com

https://www.physicsforums.com/threads/calculating-actual-weight-lifted-on-a-pulley-weight-
1000 ton boat lift



machine.952667/

 

[Baluncore]

..., many of us still can’t fathom how such blocks of stone ...

It amazes me to see modern pictures of boats, bringing stones down the Nile, with the stone supported, top-heavy on the deck.
The stone could have been slung under a significantly smaller and inherently stable raft, where the partial buoyancy of the stone would have worked to advantage.
All distance transport could then be done by river and by canal, with a string of those rafts, by one crew. The unloaded rafts would be recycled for reuse.

Offshore wind turbines could benefit from a similar analysis. It will depend on the wind turbine destination.
The buoyancy of solid steel underwater is not as advantageous as stone. But if bulkheads could be installed in the steel cylinders, the game then changes. Ballast could change the depth and trim of the cylinder. The cylinder can be transported horizontally, to be stood on end, like an oil platform, then sunk in place.

A change from steel, to a composite basalt-rock-wool reinforced concrete, may then be possible, that would reduce future maintenance costs. A monopile could be cast in a semicircular section dry-dock at sea level, being cyclically rotated, as it is extruded, out into a level controlled channel to the bay.

On land, a monopile could be slip-formed and extruded vertically from a circular underground foundation excavation. The lift could be done by cyclically flooding and draining a flotation chamber in the basement with water. Once grown, the basement flotation chamber, is replaced by the foot of the tower.

So, why all this heavy lifting ?

 

[sophiecentaur]

It amazes me to see modern pictures of boats, bringing stones down the Nile, with the stone supported, top-heavy on the deck.

The side-on view of all or most ancient images would ignore the use of a catamaran with two hulls and a platform between. Non-technical journalists / historians might just propagate this idea. The stones would, ideally be carried at a height suitable for both drag on - drag off handling so a carry height of just above ground level would be best. If the nile had been tidal, the changing level of the water could have been used but the only level change would have been yearly.

 

[Baluncore]

The stones would, ideally be carried at a height suitable for both drag on - drag off handling so a carry height of just above ground level would be best.

You have obviously never moved rocks in a river.
The ideal height is below the surface.

 

[Baluncore]

I agree this seems a bit off-topic at first, but it comes down to the limitations of racks and pinions, and how that leads to screw jacks, and then on to hydraulic cylinders, which is where the OP discussion had stalled.

The assumption was made that tower segments must be moved with cranes, and along the paved surface roadways. That restricts concrete construction, because concrete shells could not withstand the point-applied loads, encountered during the changes in orientation required between manufacture, transport and installation. The structures are now heavy, fabricated from thick steel, and so are expensive to manufacture, transport, and install.

The word "hydraulic" covers two fields, one is the oil under high pressure in earth moving equipment, where extreme forces, move heavy objects, slowly. The other "hydraulic" is floating displacement hulls, and raising them through locks, where the fluid pressures are very much lower, but applied to maybe half the hull area.
The Panama isthmus is crossed by the Panama Canal, where heavy boats, buoyant in water, are pulled horizontally into locks, by heavy, geared down electric locomotives, called mules, that have drive pinions running in racks along the towpath of the canal.

By handling tower sections as displacement hulls throughout the process, the problems of tower construction, transport and installation, can all change. The tower shells can be made from concrete, reinforced not with steel, but with the rock-wool rebar and mesh now available, that is made from basalt rock. Tower sections, extruded or cast, floating in canals, can be manipulated and floated to site, then tilted by blowing and flooding, to stand upright and settle onto a deep dredged foundation.

While not an immediate solution to the OPs problem, that is a possible game changer, worthy of consideration, that should be kept in mind as the construction limits are reached.

 

[sophiecentaur]

that leads to screw jacks, and then on to hydraulic cylinders, which is where the OP discussion had stalled.

This looks like an expensive job and the cheapest solution would make sense. We've been a bit round the houses in the thread and any solution needs to be 21st century. But, if the required job is restricted to something like the image, you would have a fixed bed level and length of load. I'm not clear what needs to be done with the load when it's lifted and the low loader moves away. Could it be lowered onto rests at approximate the same height as the low loader? The less overall height difference the simpler the arrangement.
A system with dedicated geometry could satisfy requirements. A system of substantial levers (beams), along the load would share the load and provide some mechanical advantage - say a factor of four or five (length ratio) and divvy up the load to allow cheaper hydraulics. I have to declare a prejudice about hydraulics which always upsets my intuition about the possible forces involved. Levers, I understand.

 

[jrmichler]

So far I am thinking of four cylinders per each saddle with pinned end connection to relief rods from reaction moments (sketch attached but without accurate relative dimensions). Also for the hydraulic circuit I will add LHV (Load holding valve) with a directional valve to ensure safety and provide flexible heights.

I don't have experience in lifting, so I would like to know your opinions on drawbacks of this approach and your recommendations.

This is a reasonable approach if all of the engineering is done correctly. If you search large hydraulic cylinders, you will find manufacturers that can make cylinders much larger than you would need. You could do it with two cylinders per saddle if that would result in a better configuration. Be careful to avoid sideways forces if using base mount cylinders.

Hydraulics is a good approach for very large loads, and when you want to load share between two hydraulic cylinders. Overload protection is a simple pressure relief valve.

For those who are interested in how the Egyptians built the pyramids, that should be a separate thread. But first read The Ancient Engineers by L. Sprague de Camp. It has a whole chapter on the Egyptian engineers, mostly about the pyramids. This is a popular book. It was first published in 1960, and is still available from Amazon.

 

[berkeman]

Thread closed for Moderation...

 

[berkeman]

Thread is reopened. An off-topic discussion about moving large rocks for ancient pyramid construction has been deleted.