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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. Okay...first you need to get your sketch right...it is important on this as the overhang (the "loading doorway") is a counterbalance that ensures the load is only applied in the correct way against the rollers....don't forget the cantilever masses either. Once you add the counterbalance the rollers will be loaded in the correct way and it should simply be a case of taking moments - both sides as a double check. Good luck
  2. It is difficult to say for certain, but normally in motors of any sort, the windings overheat and the varnish breaks-down (either burns off or melts) resulting in localised short circuits, identifiable by reduced resistance. ...I could be wrong, but your figures seem to back this up!
  3. One of the most popular - with huge amounts of evidence on its accuracy - is ANSYS....but there are many: COMSOL and NASTRAN at two others I've used int eh past...all three are excellent! Be warned through....FEA (or FEM as you term it - "Analysis" or "Modelling" depending on the acronym used...same thing though) is fraught with dangers! if the constraints are set incorrectly, you can get figures that look right and even seem right, but are completely wrong! NAFEMS - the regulatory body for Finite Element Modelling - recommends NEVER undertaking FEA until the hand calculations have been undertaken first...it is the only real way to ensure the results are within the expected range! Good luck!
  4. Okay....this is a bit of a role reversal....I'm far more used to offering guidance and answers than asking the questions, but here it goes.... Can anyone give a reference to a good, easy-to-follow(!), text of Taylor and Binomial expansion of Differential equations? Specifically that used in "Variational Calculus". This is something I have covered in the dim and distant past...and as the saying goes..."it's not what you know, its what you think you know and don't realise you have forgotten!"...alas, it appears I have forgotten! I have some texts on the subject, but alas insufficient to clear my mental block! Many thanks to all!
  5. Hi there! This is definitely NOT advisable! The roof is calculated out for the wind loading and the snow loading (as appropriate) with a margin of safety....it is NOT designed to be loaded in addition to this...not without appropriate calculation and checks! If you add static loading to the roof, it significantly lowers the design load of the structure from "environmental Factors"...basically, if it snows, it could collapse, if it is windy it could collapse and if there is a sandstorm (as appropriate) - Insurance would not pay out in a failure of this nature (not to mention the risk to those within). To give an example...In Southern UK, a high risk structure I calculated recently has a design snow load (although it hasn't really snowed here for 30 years...) of 2kN/m^2 ...it doesn't really sound a lot...but looking at the size of your roof...that's a huge loading! Contextually, 2kN is only 200kg per m^2...which is carried on each beam for the span...from your picture it looks like the beam supports about 4 m^2 for every metre length ....add to that, every time you drill the beam (assuming you're not using rod-lugs) you add a stress concentrator in the hole itself. The safety factor is added to the maximum load for the structure...but you have already significantly increased the static load of the structure, so your roof safety factors MUST be shot to pieces! It could well be fine, but get a structural engineer to look at this and recalculate...it will cover all eventualities, your insurance will be happy and you will have the comfort blanket of the calculations to help you sleep soundly at night! Good luck Bruce
  6. Very simple....no snow loading, so.... ...Determine your static load by means of "worst case hail or sand loading"...corrected for angle of roof. Calculate your bend as a simply supported beam (Roark's formulae by Young is a good source for bending...) and add additional support and reinforcement as required to ensure within your tolerance (may be local building regs. or use Eurocodes or US codes as a guide if not available - there are more favourable ways of getting a headache than having a roof fall on your head!). Calculate the vector loading from a single side of the truss...using a simple moment calculation and the worst case loading figures. Repeat this fir wind loading... when fitting hte trusses, ensure that they are bolted to the walls a ways down from the roof-line....the roof itself will act like an aeroplane wing in high winds....you have to counter this with the weight of the wall holding it in position...but hte most important part for Mexico.... ENSURE YOU ALLOW EXPANSION IN YOUR FIXINGS!!! Basically, the roof will expand and contract in the sun and at night when the temperature drops...if it is bolted directly to the walls, they will push out when it gets hot, crack and fail! Rest the truss on the walls and strap on with metal loops...the truss will slide on the walls without laterally loading them, ensuring longevity and still be fixed in place! Good luck!
  7. What you seek is a pipe flaring tool - sometimes known as a pipe swaging tool...they are commonly mechanical, but are available in hydraulic...I haven't seen a pneumatic version, but there is no reason why this shouldn't be available too...particularly for use around Oxygen pipework (hydrocarbons spontaneously ignite in oxygen so you would avoid the use of hydraulics in case of an oil leak). Hope this helps
  8. hmm...not quite following this...can you write the equation mathematically using brackets to ensure clarity...?
  9. 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?
  10. With some bearings, plastic has a reduced coefficient of friction (but only on low loading)
  11. 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).
  12. hmm...is it a hydrogen fuel cell, or an alkaline fuel cell...? An Alkaline one is a chemical-cell battery...!
  13. 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"!
  14. 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
  15. 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?
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