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Mechanical Engineering

G B Reid MIMechE, SIMarEST

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G B Reid MIMechE, SIMarEST last won the day on December 19 2019

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About G B Reid MIMechE, SIMarEST

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    Benfleet, England
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    Mechanical engineering "generalist", experience in Design (industrial, mechanical, aerospace grade components), Rail, Underground, defence, process flow optimisation, Project Engineering and Mechanical Systems 3D CAD user (various) since 1992. Electrical design installation and verification.

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  1. this image is not of high enough resolution to analyse...but it does look like a combination of cyclical crack propagation (fatigue) and overheating...can you upload a high res image in jpeg?
  2. With some bearings, plastic has a reduced coefficient of friction (but only on low loading)
  3. It looks like you are working out E...although this is not clear...am I correct...? If so, all answers should be roughly the same (albeit within a noticeable margin).
  4. hmm...is it a hydrogen fuel cell, or an alkaline fuel cell...? An Alkaline one is a chemical-cell battery...!
  5. There are some good answers to this here....yet no-one has mentioned the resistivity to UV ageing! Carbon black also acts as a UV inhibitor, dramatically enhancing the life of the tyre...try placing a rubber band in direct sunlight and see how quickly it embrittles! Yes, its use probably did predate the awareness of UV embrittlement, but it is still an incredibly important "happy coincidence"!
  6. A robot is a machine than can undertake actions on behalf of a human and is ideal for repetitive, accurate tasks...they can be fixed to a desk or mobile. Anything automated is - by definition - a robot if it fits the above criteria...e.g a motorised spit is a robot for turning meat over a heater....it is basic and limited in function, but it is a robot. I think ....in the modern world we are all getting a little confused! A high functioning automated robot would be a self-drive car...a low functioning robot something like the DaVincci Robot used in surgery...which is merely used to enhance control as a movement reducer (albeit on a highly controllable scale)...it is operated directly by a human surgeon and scales his movements to enhance control during surgery...despite its high capital cost, this has proven exceptionally cost effective as a result of reduced complication rates and enhanced recovery. The self-drive car would be high functioning mobile, the daVincci, low functioning fixed. Hope this helps
  7. Hi Tom, Unfortunately, there terms "clamp" and "movable in all directions" when combined with CNC are just too ambiguous...is it a mill, a lathe, a jig-borer a press-brake, a sheet metal punch, an electronics placer....the list is endless as far a s CNC is concerned. Ball joints are good ...but only up to a point;...they are restricted in control...a slider with a 360 rotator fixed on the bolt-axis can have exactly the same results especially when three are assembled together on perpendicular planes...and can offer control too... Can you give a bit more detail?
  8. hmm - initially I'd be reliant on the forge test sheets - if you request when you purchase it is easy for the manufacturer/distributor to supply. If they are not available, its a testing machine, but that's not ideal...different forms have differing specs for the same material due to crystalline structure, cooling factors, work hardening, area in billet the sample taken from and any number of additional affecting criteria!
  9. It would be down to the individual engineer... to explain: All calculations would have to be redone from scratch, assumptions checked, design verified. It is entirely possible that the engineer could find a better, more efficient/more appropriate/ more cost effective/safer method for doing the same thing...meaning the whole lot has to be redone. The costs would likely be about the same (due to the above) whether he originates or checks. hope this helps
  10. No problem! Use hydraulically operated levers and hydraulics themselves... Natural spring or diverted stream from a river via a mechanism operated 'diversions' to control either raise or lower (I.e. in 'lower' position until lowered and then the diversion...well, er...'diverts' to the 'raise' position). It would be an entertaining project to be involved in, but quite achievable. Oh - I watched with the sound off (in office with boss opposite...oops!) - so couldn't hear the wolves....but again could be operated by air displacement from a sealed-sump the reservoir...so again, yes, quite simply!
  11. Okay...I might be misinterpreting this....but a Mechanical one DEFINITELY rather than relying on "wishful thinking"... Ahh...did you mean a 'rotary' or 'static'...? in which case a rotary! That said, it MUST be selected appropriately (there's loads of variations) and installed both properly and carefully!
  12. It depends entirely on the geometry and loading of each pin....they all need to be calculated out as if there is no other present and the material selected as appropriate...they will only shear when they exceed their individual shear loading...take care to ensure double shear is calculated where appropriate.
  13. no matter how willing anyone is to help, it would be useful to know the field....are you building a pet cage, or a bridge, is it an economics project or a hairstyle trend development?
  14. Hi Dr D - I do hope you are well! The glass is an example of easily relatable "brittleness" rather than a "material example" (everyone knows glass breaks when hit...).....that said...the "supercooled fluid" is still a philosophical argument that has never - IMHO - achieved a conclusion one way or the other. Warmest wishes and Season's greetings to all! May 2020 bring success and happiness to all!
  15. It can always be calculated by looking at the section modulus. maximum stress = My/I where M is the Moment at the point being calculated y is half (assuming round) the diameter I is the section modulus (sometimes "Z")...I used to use Z, now almost always use I for some reason...(?!?)...same variable though! for round bar/tube the section modulus (I) is pi(D^4 - d^4)/64 Pi = 3.1415926....etc D = outer diameter d = inner diameter (if present or = 0 if not) As you can see from the formula...for the same weight there would have to be a relatively large increase in diameter...ultimately, the larger the diameter the lower the stress whether it be solid or hollow. If it is hollow, the diameter increases significantly for a much lower ultimate stress in bending...the "^4" has a huge effect! The rigidity is directly proportional to the stress for any given material...the larger the I/Z, the lower the realised stress. Hope this helps
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