structural torsion bear - interest check calculations?

Hello all

I think I have managed to calculate to specify structural members bearing torsion.

I needed "torsion" for the proposed new mechanical part of my rod-mill

I did all my study off the Wikipedia page

I ran through the "turbo-generator shaft" example - got the same 69cm answer for the diameter of what might be the shaft of the 1GW steam-turbo-generator of a nuclear powerstation.

Anyone interested to see my workings and advise / mentor?

All is in "flat" text. Calculations done using the Lisp of the emacs text-processor - all seen "in-line" in the "flat text".

Regards, Rich S.

------------------------------------------ I limit my designs to my amateur ability to analyze them. I use on-line calculators so I don't forget anything, and a maximum rotating shaft stress of half the ultimate tensile strength, which was verbal advice. Usually they confirm my paper calculations pretty closely.

Thanks for the pragmatic "how to get things done" advice.

I "confess" if I come across an on-line calculator I use it as one means to check if my answer is what others get. Rourke has a many-terms probably empirical mathematical expression for getting "within 5%" the torsion constant of a rectangular shape - and I found an online calculator, which enabled me to do some random spot-checks - my function concurred with the online calculator :-)

I also manually once-off key into a calculator as another longstop check. Sometimes have to note the result of "intermediate" calculation of terms then key back in those terms later when bringing them all together in one. "Just" try to use different methods so there is no propensity for the same systematic error to recur and give false validation.

Hello all

I think I have managed to calculate to specify structural members bearing torsion.

I needed "torsion" for the proposed new mechanical part of my rod-mill

I did all my study off the Wikipedia page

I ran through the "turbo-generator shaft" example - got the same 69cm answer for the diameter of what might be the shaft of the 1GW steam-turbo-generator of a nuclear powerstation.

Anyone interested to see my workings and advise / mentor?

All is in "flat" text. Calculations done using the Lisp of the emacs text-processor - all seen "in-line" in the "flat text".

Regards, Rich S.

----------------------------------------- I suspect the limiting condition may be a combination of drive torsion plus cyclical stress from beam loading of the rods between the drum rollers and the pillow blocks. Analysis of cantilevered shafts or those in a rolling mill might apply. A simple fix is supporting rollers under the drum rollers. They could be the bare outer races of ball bearings, as used on the blade guides of metal-cutting bandsaws. In bearing specs R is for rubber seals, S for metal shields which have less friction but let fine dust in.

On a cost sensitive design without machining ability you may end up with a shaft size for which you can find the drive connection, bearings and drum rollers to fit. Then you need to know only the minimum size and exceed it. With machining ability you can turn the shaft end smaller and make custom sleeve bushings for larger bores and inch/metric conversions, and use second hand parts that are still available because other tinkerers couldn't.

The lathe limits are the distance between centers for shorter shafts and the spindle center bore for longer ones. My lathe will take ~35mm diameter through the spindle and ~500mm length between the spindle and tailstock. It's a good size for experimental prototypes and demonstration models but not to build or repair production machinery. My vertical knee mill with a 6" x 24" table is similarly limited to smaller work. They let me demonstrate ideas I can't and don't want to manufacture.

It might not be evident that pillow (plummer) blocks may mount the bearing in a spherical shell that can compensate for shaft to base misalignment. They can be tightly fitted and stiff.

Hopefully I've "got" those things.

As my rod-mill is only 240mm dia. external (/ 240 25.4) ;; 9.448818897637796

Lathe - yes - the size of the bore through headstock for long rods.

For this job, between-centres length is going to be the restriction for most "hobby" / small lathes (* 19 25.4) ;; 482.59999999999997 The shaft will be about 650mm long. That is definitely an "outsourced" job. Fortunately found local machine-shop and then have friend who has good industrial lathe.

Pillow-bearings / plumber-blocks - why are popular... Mass-produced with that precision feature of the spherical self-alignment feature so that will find its own good alignment between two plumber-blocks...

All this has been the learning-curve. Reason I am not being too hard on myself about why it has all taken so long. Another "discovery" is that electric motors come in a series of standard "frame sizes" and gearboxes are matched to fit - obviously the bigger the motor the more power and the bigger the gearbox needed, so yes you get a corresponding series of gearbox sizes. Etc., etc.

I have come quite a journey.

With memory returning after the grim part of just surviving, a friend and I were laughing as it came back to me about, having adjusted a milling-machine properly there was swarf "hosing" across the workshop and bouncing off the wall at about a 3-inch diameter place 2~1/2ft off the floor and cascading around the workshop floor - on a machine which had only in that location been known to clatter and produce puffs of dust and sparks. The poor technician - scientific but not mechanical - grasped for hair he hadn't got and looked anguished to put it mildly - crying out "You can't use it like that!". A time-served machinist technician who had come to be my guardian-angel said firmly on the contrary that is how it should work. A researcher who was a former marine engineer on tankers also chipped (?!) in saying likewise. Well the poor technician we couldn't "rehabilitate him into society". We had to get the sales rep. for the tool company to come along, who politely and with detail explained this was the only way to use the tooling. I had never met the tooling before, but sensed what it wanted and the timeserved machinist was behind my back ready to call "stop" if needed.

There were others where I laughed about being back in the headspace of confidence and "going for it". As for the "liquid nitrogen temperature machining" :-) One grizzly looking industrial metallurgist stalled to a stop with jaw dropped when he saw the shaper with cold steam pouring everywhere. When I explained "..." briefly he responded "I can see WHAT it is you are doing. I just can't believe someone would actual do IT!". He'd advised me on weld hydrogen in steels giving me some first pointers. What he could see was that I had made a deduction about how you could investigate it and was giving it a go. Later I was not supposed to hear when he chided my supervisor "So now then who's insane?!" as the shaper smoothly trouble-free shaved away cuts, running "hands-off" on auto-feed when it was found that there were no problems doing what I visualised, with the tool sloshing back and forth through the liquid nitrogen shaving the metal at that temperature (it "freezes" the weld hydrogen in-place, "stopping the clock" - so you can do things to perpare samples). In many ways what I am going through is reconnecting after so many injuries and such an oddessy.

To an extent, the "post-industrial" "sensibleness" which excluded me from this new "sensible" economy has come to this "nose-dive crash" where a nation of about 150million people is 4X out-producing a combined bloc of about 800million people (Europe and the USA). "financialised" for more than a generation and incapable of "regrouping" (?). We can make admonishing statements, proclaim we identify and prove damning malfeasance, stand firm and wag our finger at said identified miscreant

- and be completely ignored and stepped around because it's all backed-up by absolutely nothing. To an extent, seeing this endpoint come, as anticipated, has been a validation.

So yes, on with the rod-mill :-)

Regards,

All this has been the learning-curve. Reason I am not being too hard on myself about why it has all taken so long. Another "discovery" is that electric motors come in a series of standard "frame sizes" and gearboxes are matched to fit - obviously the bigger the motor the more power and the bigger the gearbox needed, so yes you get a corresponding series of gearbox sizes. Etc., etc.

I have come quite a journey.

---------------------------------------------

With my formal education interrupted by the Vietnam draft and my natural tendency being hands-on I decided to become the broadly skilled assistant who turns theoretical proposals into functioning hardware. I was lucky to find a company that would educate me as an apprentice machine builder and designer and learned many of the mechanical and electrical practical details with assistance, plus reading manufacturer's application literature which was a great help.

A chemist may work alone so we learned the hands-on techniques such as weighing, titrating and polishing and etching metal samples for microscopic examination. It appears that electrical and mechanical engineers can keep their hands clean if they choose, I did a job for a Ph.D who didn't know that resistors have tolerances, he asked for 8 digit precision from an op amp circuit, and for a mechanical engineer and professor who didn't know about press-in thread inserts for sheet metal and thus over-designed robotics. Few could solder well or make a square cut with a hacksaw.

"Jim Wilkins" snipped-for-privacy@gmail.com writes: ...

That is definitely an "outsourced" job. Fortunately found local machine-shop and then have friend who has good industrial lathe.

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I found that I'd be lucky to get what I carefully specified (TL;DR) and could forget about anything I’d merely hoped for. My small jobs were always lower priority than bigger jobs for regular customers. Without understanding machining I didn't know the easy versus hard ways to do things. I took a night class but it didn't cover enough of the quirks of my R&D assignments which were always about something not done before. That's why I bought a lathe and mill once I owned a house to put them in. Being non-salaried I could charge for the time I spent on them iteratively machining and redesigning parts. For me that can be easier than fully designing them on paper, as the incomplete part suggests improvements, and a modification in the evening may make testing easier the next day.

I'm in the midst of outsourcing work I don't trust my ability for now, the mild steel flanges rusted off the manifold pipe where it connects to the catalytic converter, and off the exit from the OEM converter. I bought an aftermarket converter locally and machined a mechanically clamped substitute for the manifold flange. The connection is a graphite donut gasketed swivel joint to isolate the engine's motion in its mounts from the exhaust. I just replaced those mounts because the engine had destroyed one and torn the other.

The hotrodder-recommended welders want to replace the swivel joint with a fixed sleeve, apparently standard practice because it's easier for them than replacing a flange in proper alignment. Next time showing the torn engine mount should prove my point that this exhaust joint should remain flexible. I've been making a clamp fixture to hold the new 304 SS flange in position without blocking welding access as my current clamp does, and bought some

I've read "Not Much of an Engineer". He "came of age" in the 1960's?

Great book.

He was one of the "professional descendents" significantly of Beatrice Shilling. Who is famous for solving the carburation glitch on the R.R. Merlin engine (the engine in the "Spitfire" aircraft) in 1940. She was going around airfields during the "Battle of Britain" on her motorcycle (she was an expert - she used to race at Brooklands during the 1930's) fitting that flow-rate-control device which reduced the matter to an ignorable "pop". Which Stanley Hooker dubbed "Miss Schilling's orifice". He was from a part of the country where that is the nature of discourse...

I've read "Not Much of an Engineer". He "came of age" in the 1960's?

Great book.

He was one of the "professional descendents" significantly of Beatrice Shilling. Who is famous for solving the carburation glitch on the R.R. Merlin engine (the engine in the "Spitfire" aircraft) in 1940. She was going around airfields during the "Battle of Britain" on her motorcycle (she was an expert - she used to race at Brooklands during the 1930's) fitting that flow-rate-control device which reduced the matter to an ignorable "pop". Which Stanley Hooker dubbed "Miss Schilling's orifice". He was from a part of the country where that is the nature of discourse...

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I also read and liked Nevil Schute's "Slide Rule" which goes into how government funding brings opinionated political interference with engineering. Mitre was supposed to isolate the two but that's not possible. The Greenies here want to switch from petroleum to electricity without considering or understanding the consequences; they push for distributed alternate electricity sources but block expanding the transmission lines. A hostile foreign power could hardly imagine a better way to cripple American industry.

I assume you know about Bletchley's work, this is a US example of leading edge WW2 electronic tech:

Read R.V.Jones' book too :-) "Cockney" - never heard recordings of him speaking, but apparently he could switch back to speaking "Cockney" when playing practical jokes on folk.

The blatant fake is concealing that electricity coming into the home is only 50% of the energy value of the gas burned at the power-station. So if you got a 4-to-1 pumping ratio in the house, that's only 2-to-1 on CO2 emission. Getting 4to-1 pumping ratio is achieved by well-to-do geeks in an ideal set-up. Typical ratios are less.

Self-serving fake 2 If lowest CO2 emission were the goal - >>> run a heat-pump at the home on natural gas!!! <<< Then you are back to 100% of the heat of the gas into the home. Then any heat-pumping is a bonus.

National security - you could put other fuels down pipelines. In tough times you could gasify coal. In Britain we do have coal which is reasonably accessible.

In the "fly-over" stated in the USA, ground-source heat-pumps are reputed to work well.

Security danger 2 If the electrically powered heat pump has to "turn on a resistance-heating element to defrost the heat exchanger" the load on the electricity grid would go up about 8-fold - and this would happen simultaneously across a large proportion of installations at the same time - which would surely "crash" "the grid". People would die.

The ones who wrote that article are purveyors of a narrative. Evaluate its value - at the lowest end of the scale?

Apparently fuel-powered heat-pumps to exist for large installations - the Government does know that as seen in a report I once read - but no effort has been made to miniaturise these things - no competions, challenges to universities, etc.

Finally - if heat pumps don't work and people are forced to use resistance electric heaters you are suddenly selling twice the amount of gas and making 4X the profit on that - 8X the income - so there is good reason to have a view which has remarkable-and-surprising (!) omissions...

Regards, Rich S.

Apparently fuel-powered heat-pumps to exist for large installations - the Government does know that as seen in a report I once read - but no effort has been made to miniaturise these things - no competions, challenges to universities, etc.

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Co-generation of heat and electricity doesn't appear economically practical at the single home scale, and they are needed without delay at different times. if it seemed a possible answer I'd be exploring it. A heat pump requires electricity or engine-driven shaft rotation, the most difficult and inefficient forms of energy to produce though the most valuable. In this climate the needs for winter heating and summer air conditioning are both high and electricity and hot water are continuous. The best price I've seen for reputable(?) LiFePO4 batteries to provide a continuous supply from intermittent generation is over $200 per kilowatt stored, before installation. Look at how much you use per day.

Thermoelectric and small turbines are far too inefficient, piston power not far behind. Grid power benefits from the complex engineering practical at large scales. Without it, as with steam locomotives, fuel efficiency is very low.

When I was involved with the Milstar satellite network a request came through to develop a 50W fuel powered generator to power laptops and satcom radio terminals in the field, ie Iraq. That's about 1/15 HP. They used to have a soldier-cranked one.

All I could contribute was a WW2 dynamotor 24V to high voltage converter for aircraft radios, to show 50W done with conventional copper windings and iron laminations. Later I worked with Segway motors of somewhat smaller size and considerably higher power (proprietary info) due to advanced magnets. I have some discarded prototype motors without the safety disconnect to use as DC generators, perhaps hand cranked or with a windmill or model heat engine. I haven't because one $50 solar panel produces as much or more power than a human can continuously, estimated at 75W.

The better emergency solution is a little Honda generator I bought reasonably and fixed, and for which I made a gas tank pressurizer to prime and fully drain it for safe indoor storage. It can charge used time-expired hospital VRLA batteries that I couldn't claim as a Form 5695 tax deduction, unlike batteries bought new and subject to tighter IRS rules. After a storm my time is more valuable clearing snow / ice from the driveway.

Motor powers pump ("compressor").

It "only" has to achieve 1-to-{approaching2} to beat 1-to-4 of a an "immaculate installation" mains-electricity powered heat pump. (not the full 2-to-1 because the heat from the motor also goes into the house) If I reckon this correctly. The energy security of having motor-powered heat pumps with different fuels would surely be an advantage. I would gladly have some sort of heat-pump running from my central-heating oil if it saved energy and fuel costs. Suppose it were a little turbine of absymal efficiency - all its exhaust heat worked or wasted goes into the house then anything it heat-pumps is a bonus. Have I got something wrong here?

The electricity "grid" here is very fragile. We in our village had a three-day power cut last winter. We have enough population to have traffic queues at juntions and into towns during "rush hour". In Britain most homes have "TN-C-S" earthing. That is otherwise known as "PME" - Protective Multiple Earthing. The Earth is provided by the substations. In Cornwall they dare not do that - you can only have "TN-C-S" where the cables are underground, secure and protected. IN Cornwall most are on poles and pylons. The risk of losing your Earth while some power is getting through is too high. I am painting a picture of a fragile supply?

I haven't researched this much I admit.

Hinckley Point C is years in build and you have a feeling these "huge" nuclear power stations are not the answer. Seemingly lofty dreams strung on lamentable realities.

Like it...

The electricity "grid" here is very fragile. We in our village had a three-day power cut last winter.

---------------------- I've lost power for over a week several times, after ice storms brought down trees onto power lines. Trees next to the road are too risky for us to cut down as they grow and lean into the opening, and quite expensive to hire out if a crane must take branches down sequentially, often the case near houses. Many people have portable or permanent generators and roof solar is fairly common here. Although winters can be Norwegian our latitude is slightly south of Marseilles.

For watching and recording TV I have an antenna and low power demand laptops running Windows 7 Media center, with USB TV tuners. The microwave, coffee pot and main refrigerator are on grid power though the refrigerator can start and run from an APC1400 sine UPS during an outage or a storm when late night lightning or grid loss is likely, and the others briefly from a generator.

An inverter that senses load and shuts off when not needed would increase battery life, the APC's ~50W idle power nearly equals the compact fridge's draw. But the APC was free (to fix). Some models of UPS are intentionally crippled against long term misuse on battery power, especially those that lack a fan and can overheat with battery capacity larger than designed for. A smaller one of mine shuts off after 30 minutes on battery.

I first added a sink spray hose to the shower head with a Y adapter to wash the wife's dog during cold weather, and we liked it for ourselves enough to remove the fixed head. Unlike commercial units it shuts off when released, saving expensive electrically heated water. The extended hose reaches and helps clean the sink and toilet. The house was all electric, the cost of winter heat is why I bought the wood stove. One KWH costs $0.21, it has peaked over $0.30. Those who signed up for various percentages of alternate energy pay more to feel superior.

The long haired dog tolerated the bath as long as her head was outside the curtain, she was willing to learn only what was mutually agreeable, yawning or howling offended her dignity, and no perfumed shampoo. She learned to "Shake!" water off on command, in the tub and not again until outdoors. It was funny when people asked her to "shake" expecting a raised paw. She'd do that as well on a "Paw" command, with much swapping while trying to remember right vs left. Golden retrievers can be smart and eager to be appreciated but have their limits, for her about 30 words and phrases. I've read that monkeys aren't much better, dogs just don't have the hands or facial muscles.

Motor powers pump ("compressor").

It "only" has to achieve 1-to-{approaching2} to beat 1-to-4 of a an "immaculate installation" mains-electricity powered heat pump. (not the full 2-to-1 because the heat from the motor also goes into the house) If I reckon this correctly. The energy security of having motor-powered heat pumps with different fuels would surely be an advantage. I would gladly have some sort of heat-pump running from my central-heating oil if it saved energy and fuel costs. Suppose it were a little turbine of absymal efficiency - all its exhaust heat worked or wasted goes into the house then anything it heat-pumps is a bonus. Have I got something wrong here?

-------------------------------------- I think you are exactly right, the problems are how to build it economically and how to adjust the balance between hot air, cooled air and hot water demands. About half the fuel energy into a motor goes into the exhaust and is difficult to recover, the Titanic's turbine is a good example of capturing the energy from cylinder exhaust, and the complexity thereof even with the ocean as the cold sink. The issue is that cost and difficulty of recovery increases inversely to temperature differential, as with condensing locomotives. Stirling engines that operate on a cup of hot water have very low power compared to smaller hot-burning model airplane engines that would fall into the cup. Trevithick's and Evans' increases in steam engine pressure and temperature finally made it light and powerful enough to move practical vehicles, a century after steam power first appeared.

One might answer undependable availability. I chose locally abundant, free, renewable and cheaply storable solid fuel for heat and solar only for loads that require electricity. Today was overcast with rain and the panels produced only about 5% of their rating. Having had a few overcast days I needed to switch to a spare to avoid the freezer stopping from low voltage overnight. The batteries have and need terminal voltage meters and charge/discharge current meters to show state of charge (SOC), which isn't as evident from the almost constant voltage of an LiFePO4 as with Li-ion, AGM or flooded lead-acid.

I had a mixed breed who used to tease me by offering her left paw when i told her to shake a paw, also, the only way I could give her medication was to let her off her outdoor tether after clipping on her leash - I guess, to her, this meant that I was the boss.

I had a mixed breed who used to tease me by offering her left paw when i told her to shake a paw, also, the only way I could give her medication was to let her off her outdoor tether after clipping on her leash - I guess, to her, this meant that I was the boss.

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They are aware of the pecking order. My mother's Doberman quickly recognized me on it and did whatever I asked. It clearly knew what I wanted, simple things like go to where I pointed, lie down and stay there, as mine would. The dog understood exactly where the property boundaries were and would break off chasing a cat or squirrel at them and stand guard.

I think Mom acquired the dog from an elderly friend who could no longer keep it. It must have been well trained but not by her, she had no authority with animals, that was my job. The wild rabbits around here stop running away when they recognize me and sometimes sit nearby nibbling clover and watching me work. Maybe I'm protection from hawks.

A neighbor acquired an unruly black lab that appeared untrained, and would nip at my legs. I finally grabbed under its lower jaw and pressed the lips against the teeth while firmly telling it to stop.

The dog instantly stopped testing and respected me and would do whatever I asked. I didn't want to embarrass the owner so I took the dog for a walk in the woods to see what it knew or picked up on, such as investigate a burrow opening I pointed at, and break off running around when asked to follow me, not "heel" but pay attention and come along, my phrase was "this way". Those were things I'd taught my dog to do, normal dog actions instead of useless tricks which mine would quickly learn and then refuse to repeat. I learned when to stop asking.

Teddy Roosevelt took a vacation between being elected and assuming the Vice Presidency, hunting livestock-killing mountain lions with dogs in Colorado. The dogs were very friendly, even cuddly with humans yet rough on each other, constantly challenging for dominance. When they caught a lion, which are faster sprinters but lack a dog's endurance, the lower ranking pack members would cooperate by grabbing and pulling legs, tail, ears to immobilize it, then a strong dominant dog would close in on the head. A lion could kill a single dog easily, the pack wouldn't allow it to concentrate on one member.

Roosevelt waded into the fights and killed lions with a knife, as a bullet might hit a dog.

When Obama was on Bear Grylls' TV show his guard detail wouldn't let him step off the road.

I had a mixed breed who used to tease me by offering her left paw when i told her to shake a paw, ...

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I taught mine to shake right to right or left to left, as the person offered. That was likely what confused her/it (spayed). The same side would be easier.

On an introductory flight lesson the engineer instructor told me to turn right toward a mountain he named, that was on the left.