Hello and welcome to our community! Is this your first visit?
Register
Page 5 of 5 FirstFirst ... 345
Results 41 to 48 of 48

Thread: Rix sa3

  1. #41
    Established TDF Member
    Join Date
    Jun 2014
    Location
    Broadway Cotswolds
    Posts
    1,614
    Likes (Given)
    178
    Likes (Received)
    750
    Quote Originally Posted by jamesp View Post
    Clue was Jellical, as in TS Elliot.
    I know and mine was "Evanjellical"

  2. #42
    Established TDF Member
    Join Date
    Jun 2014
    Location
    Broadway Cotswolds
    Posts
    1,614
    Likes (Given)
    178
    Likes (Received)
    750
    Quote Originally Posted by jamesp View Post
    OK, elaborate on the UN threads please.

    Metric is flat crest, full rad root, 60> angle.

    UN (C or F) is flat crest, flat root and 60> angle.

    UNR have a full continuous rad in the root.

    BSW (pre or post metal saving) is crude on a good day, and BSF can be found under the fossil layer.
    Heck and here's me thinking that the Whitworth thread form was a 55° angle

    That is unless your 60> could be interpreted as a 60< then I guess were almost there.
    Last edited by iain/hsm; 06-01-2021 at 12:41 PM.

  3. #43
    Established TDF Member jamesp's Avatar
    Join Date
    Dec 2012
    Location
    Wrexham
    Posts
    5,043
    Likes (Given)
    2673
    Likes (Received)
    1821
    Quote Originally Posted by iain/hsm View Post
    Heck and here's me thinking that the Whitworth thread form was a 55° angle

    That is unless your 60> could be interpreted as a 60< then I guess were almost there.
    ACME is 29.5, and Metric Trapezoidal is 30.
    Also irrelevant to the question.

    I only quoted UN and Metric at 60, as they are the same thread angle; and they were the thread forms you were comparing.

    Now you do a tangent onto BSW and avoid the question.

    So back to the question of why?

    If you want to tangent back onto other thread forms, go ahead, kind of home turf for me.

  4. #44
    Established TDF Member
    Join Date
    Jun 2014
    Location
    Broadway Cotswolds
    Posts
    1,614
    Likes (Given)
    178
    Likes (Received)
    750
    Quote Originally Posted by jamesp View Post
    ACME is 29.5, and Metric Trapezoidal is 30.
    Also irrelevant to the question.

    I only quoted UN and Metric at 60, as they are the same thread angle; and they were the thread forms you were comparing.

    Now you do a tangent onto BSW and avoid the question.

    So back to the question of why?

    If you want to tangent back onto other thread forms, go ahead, kind of home turf for me.
    Heck James you really need to get out more. A lot more.

    The thread is about the SA3 and SA6 I dont think the reader is too worried about how much screwing you do.

  5. #45
    Established TDF Member
    Join Date
    Dec 2012
    Location
    NW UK
    Posts
    1,726
    Likes (Given)
    510
    Likes (Received)
    664
    Quote Originally Posted by iain/hsm View Post
    Additional weight saving is also being considered using an aluminium crankshaft opposed to stainless
    That seems like a considerable step backwards for a few grands worth of machine.

  6. #46
    Established TDF Member
    Join Date
    Jun 2014
    Location
    Broadway Cotswolds
    Posts
    1,614
    Likes (Given)
    178
    Likes (Received)
    750
    Quote Originally Posted by WFO View Post
    That seems like a considerable step backwards for a few grands worth of machine.
    I hear what your saying but its it does resolve a number of build options to improve the all up weight questions. For starters it reduces weight and this is a real issue for folk requiring the biggest portable compressor at the lightest possible weight rarther than a luggable one.

    More bang for your buck so to speak but most folk kick off by asking how long does it take to fill a cylinder (define size) Only then by it's weight followed by the idea of it being oil free that you can also mount it upside down on the roof in the engine compartment of the catamaran with the chemical filter, air intake filter and filling attachments out on board or on deck cabin. And the option that if you go at 1500 RPM you can run it off the motors secondary output shaft with an Anderton clutch.

    Flow rates being dependant on motor size and RPM as well as the discharge pressure required
    But with options to run from 300 RPM up to 1500 RPM the motor size and weight is also a consideration say 1 BHP to 5 BHP.

    Two other considerations you need to be aware of in that its not like a conventinal compressor design with the con rods opposed at 90 degrees to the drive shaft where you need plenty of "meat" to reduce shaft flexing like on a race car engine.

    These oil free designs use the military "Swash Plate" principle similar to a helicoptesr and a good quality aircraft approved 7075-T6 aluminium would be more than able to handle the rod loads and as there is no deflection on the shaft with its axial thrust load than the conventional radial you could make it out of one of the modern polymers and get away with it but for the cost.

    The other factor to consider is that most high performance small air compressors are used on aircraft mostly military where lightweight and performace is critical.

    Making in stainless is easier, machine it, clean it, mic it up, and use it as opposed to Aluminium with its Machine, clean, mic it up, ship to platers, anodize it , ship it back, mic it up again after plating before you can use it.

    The pulley also adds another problem if changing from nickel plated steel to aluminium unless you go direct drive in that the weight of the pulley balance counter acts with the movement of the 1st stage piston and balances out the weights between the drive end and the cooling fan end with its swash plate.

    And yes its like this for every nut bolt and screw. Ask James. What kettle calling the pot LOL
    Last edited by iain/hsm; 06-01-2021 at 03:57 PM.

  7. #47
    Established TDF Member
    Join Date
    Dec 2012
    Location
    NW UK
    Posts
    1,726
    Likes (Given)
    510
    Likes (Received)
    664
    Quote Originally Posted by iain/hsm View Post
    I hear what your saying but its it does resolve a number of build options to improve the all up weight questions. For starters it reduces weight and this is a real issue for folk requiring the biggest portable compressor at the lightest possible weight rarther than a luggable one.

    More bang for your buck so to speak but most folk kick off by asking how long does it take to fill a cylinder (define size) Only then by it's weight followed by the idea of it being oil free that you can also mount it upside down on the roof in the engine compartment of the catamaran with the chemical filter, air intake filter and filling attachments out on board or on deck cabin. And the option that if you go at 1500 RPM you can run it off the motors secondary output shaft with an Anderton clutch.

    Flow rates being dependant on motor size and RPM as well as the discharge pressure required
    But with options to run from 300 RPM up to 1500 RPM the motor size and weight is also a consideration say 1 BHP to 5 BHP.

    Two other considerations you need to be aware of in that its not like a conventinal compressor design with the con rods opposed at 90 degrees to the drive shaft where you need plenty of "meat" to reduce shaft flexing like on a race car engine.

    These oil free designs use the military "Swash Plate" principle similar to a helicoptesr and a good quality aircraft approved 7075-T6 aluminium would be more than able to handle the rod loads and as there is no deflection on the shaft with its axial thrust load than the conventional radial you could make it out of one of the modern polymers and get away with it but for the cost.

    The other factor to consider is that most high performance small air compressors are used on aircraft mostly military where lightweight and performace is critical.

    Making in stainless is easier, machine it, clean it, mic it up, and use it as opposed to Aluminium with its Machine, clean, mic it up, ship to platers, anodize it , ship it back, mic it up again after plating before you can use it.

    The pulley also adds another problem if changing from nickel plated steel to aluminium unless you go direct drive in that the weight of the pulley balance counter acts with the movement of the 1st stage piston and balances out the weights between the drive end and the cooling fan end with its swash plate.

    And yes its like this for every nut bolt and screw. Ask James. What kettle calling the pot LOL
    So is the proposed ally crankshaft actually doing any cranking? Or is it more just a drive shaft that's turning the swash plate round? (I've never had one of these apart myself)
    Either way, on a component that's going to see all the resultant radial loads from the belt drive plus wear and tear over the years from strip downs, removal of pulleys etc I'd personally prefer stainless and don't really care that much for weight, I mean how much is it going to save? A kilo or two?


    P.S all sounds very mil spec and fancy talking about swash plates but the hydraulic pump on my digger is swash plate as well... in fact so is the pump in a £50 chinesium pressure washer ;-)

  8. #48
    Established TDF Member
    Join Date
    Jun 2014
    Location
    Broadway Cotswolds
    Posts
    1,614
    Likes (Given)
    178
    Likes (Received)
    750
    Quote Originally Posted by WFO View Post
    So is the proposed ally crankshaft actually doing any cranking? Or is it more just a drive shaft that's turning the swash plate round? (I've never had one of these apart myself)
    Either way, on a component that's going to see all the resultant radial loads from the belt drive plus wear and tear over the years from strip downs, removal of pulleys etc I'd personally prefer stainless and don't really care that much for weight, I mean how much is it going to save? A kilo or two?

    P.S all sounds very mil spec and fancy talking about swash plates but the hydraulic pump on my digger is swash plate as well... in fact so is the pump in a £50 chinesium pressure washer ;-)
    Heck WFO

    I thought enough was said to convince you and the helicopter example would have been enough. Please bare in mind I am not a teacher but no matter here goes nothing. To kick off your hydraulic pump on your digger and this Chinese pressure washer are no way close to the design consideration required for compressing gas with a compressible “fluid”.

    You first need to consider the swash plate dynamics in a compressor is the primary goal in achieving as close to optimal piston loading on each stage as you can for good running balance. Moreover the difference between a helicopter and a compressor swash plate is in the piston stroke on the swash plate being radial against the internal rotation on the crankshaft with the inner race of the main crankshaft bearing running at the required RPM opposed to it’s fixed non rotating outer race. Its that aspect that makes the difference.

    Although the swash plate motion is similar to that of a helicopter it is however not entirely sinusoidal And the pistons in stages 1st 2nd and 3rd are attached to the swash plate in the axial plain while the piston stroke is radial. Also that each piston stroke do not match in diameter mass (weight) and need a separate thrust rider as well as some engineering skill to gain a good distribution position on the swash plate for each stage.

    In addition for good running balance each piston moments of inertia needs to be both balanced and matched. You don’t have this consideration on your CAT pump. I hope this will do in answer to your question but if you or others would you like the full nine yards of maths we can go deeper with it if you like.

    Please rest assured that there has been a lot of engineering in this and it works. It works well and it works well for a long time. There is also a huge amount of engineering design left out that we have not yet discussed. My post was originally in reply to a question about the compressors availability. The "Kit Form" version was a disclosure of what was being discussed. I guess it has now grown legs. Iain
    Last edited by iain/hsm; 06-01-2021 at 10:02 PM.


 
Page 5 of 5 FirstFirst ... 345

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •