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question and tips from a new one

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by adgun, Apr 24, 2008.

  1. egoexpress

    egoexpress Active Member

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    If we really would like to work out another actuator, the concept has to be really sophisticating this time. I dont want to make another toy, that looks pretty cool like our stepper actuator, but ends up in being too slow and too weak.

    I dont think that we will be able to achieve speeds above 150mm/s with metric screws and steppers.
    Your concept for the linear acutator seems to be good, but you wont be able to use steppers, if the screw pitch is 5mm.

    In that case (5mm pitch) you have to use fast DC motors, and gear them perhaps via a belt and pulleys probably.

    I think you should go for DC motors, and try to assemble such a linear DC actuator with metric or screws. As well the interface (Thanos AMC1.5), to control them, is available yet.

    If you rather want to use steppers, then you should use ball-screws with a pitch >10mm.

    I know the specs of the FD and SCN5. I just wanted you to see what you have to achieve, when you want to build something serious.


    Regards
    Christian
  2. Cubane

    Cubane New Member

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    I have the link at home but I remember the specs of the actuators on the Force Dynamics 301 being a range of 450mm(18 inches) and a speed of 600mm/s (24inches/s). If someone comes up with or find a good solution for linear actuators being able to support the large weight it would be awesome. I am looking at what type of simulator to build and something like the 301 would be great. Failing that I think it will have to be the same as tronicgr's.
  3. adgun

    adgun Active Member

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    The second time i was submiting a big repley, got a panda update and must start over again.


    First off all, the screw pitch can't be more than 10mm fore a scn5.
    Rolling reducers are the best but you have to stall,with sliding ones you can stall,but they are less efficient so you
    need more power.
    With sliding screws you must stay under 1500rpm,so you need lever arms to speed up (2e drawing)
    The more lower rpm the better it is.
    There are cheape electric car jacks from China,they are 150 watt (more than most whipper motors)and the arms are bolted on,you can make your one arms ,and make what you want(speed and travel), with inn there powerlimits.

    There is only one thing to look after:The jacks are made only to push,it can by possible that you blow the shaft out when puhling
    to avoid that ,weld ore gluw a bold on The shaft as near as possible to the pulley.

    Cristian asked my to take a look at the FD405 and that i will tell what i did see.
    The only inportend thing i read the tooth angle is 18 degrade from there shafts (meby its possible to find out witch shaft they are using ,when somebody now a site with technical drawings from roller shafts ,please post it)so we can find the pitch.
    When I see there arms i say it,s basic ,when you make your own actuators you must avoid turning within the actuator
    (normaly it's made on the inside)I did that with the wheels from Thanos on the out side ,they do the same.
    Because they use two monting points on the downside it must stand in X/Y as position(with a wheel from Thanos you don't have to.)there arms are big with litlle depth ,that means small diameter from motor.
    What they did on the inside i explane from my last drowing.
    The hole backplate is there monting plate(by me a T profile) ,they taken of the wheel from the metal tube and put a shaft in it.
    They slided 2 acial bearingblocks over the shaft,and rived them on the montingplate,this way you don't need the giding
    bearing in the tube.
    On there monting plate it's easy to make it belt driven.
    What they made is ,standard for industry.

    Cristian i totaly agree ,that if you want to start a new project ,it must be totaly worked out before you started.
    Can BDLC motors do the yob?

    regards AD
  4. adgun

    adgun Active Member

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    Hi.

    If anyone want to now how a electric cilinder works take a look at festo.com
    They have electric cilinders ,the DNCE ones they give every info you need also inside looks
    For Cristian the screw pitch started a 1,5mm ,with a pitch from 5mm they make 0,25m/sec
    They started at 560,00 euro ex. vat
    regards
    ad
  5. egoexpress

    egoexpress Active Member

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    I know quite well how linear acutators are built. I just dont know how to calculate the torque in combination with the pitch to achieve sufficient thrust.

    But if we stay at 1500 rpm, what is equal to 25rps, we would have a max speed of 125mm/s with a 5mm pitch, which is definatly too slow.

    So either we have to use a higher pitch (10-25mm), or higher rps.
    But your concept with steppers and 5mm pitch is not fast enough.

    I think the car jacks wont be a good idea. We talked about them some time ago. Perhaps it would work, but I wont like to try it out, as it seems not sophisticated enough.
    But if you are convinced in this concept, dont hesitate.

    I think we should work out the linear actuator concept.

    BLDC and AC motors arent supported yet. But Thanos is working on AC afaik.

    Regards
    Christian
  6. adgun

    adgun Active Member

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    THe formula i used ,they use it for cnc.
    When you want formula,s for the motors Take a look at FESTO.com ,you can find them there.
    I can give you more formula's ,but it's only in dutch.
    The stepper motor i refered to gives 0,2 at 1800rpm ,and with 48volt the same by 3000rpm.
    With the first given formula it means 250mm/sec 23kgf by 48 volt.
    I dont recomend this because the shaft wights 0,9kg spinning with 3000rpm you need a lot to stop this.
    It's like driving your car with a caravan with gone brakes behinde you.
    I dit give only a example with the drawing and have taken that shaft becouse he costs 65,00 euro with nuth.
    Its allways better to keep your revs down(with a big shaft pitch)but you have to pay mutch more.
    You understand now how the FD actuators work ,when you make a drawing and phone a sireus motor suplyer
    they will tell you witch motor you need.
    regards AD
  7. egoexpress

    egoexpress Active Member

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    Well,

    if we want to talk about 300-600cm linerar acutators, and if we want to stay under 1500rpm, then the calculation is the following:

    max 1500rpm/60 -> max 25 rps

    25 rps * P-5mm = 125mm/s -> quite slow
    25 rps * P-10mm = 250mm/s -> ok for GA flight sims
    25 rps * P-15mm = 375mm/s -> good
    25 rps * P-20mm = 500mm/s -> very good
    25 rps * P-25mm = 625mm/s ~ speed in the FD league

    Either we use higher rps, or higher pitch. Higher pitch requires alot of torque. Higher rps causes alot of mass inertia. -> Dilemma :D

    Regards
    Christian
  8. adgun

    adgun Active Member

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    Hi
    It possible that the torque stays the same.
    You can win a lot when you make the roller shaft hollow.
    When i ment formula,s fore motors at festo ,I ment the formula,s for mas interia/stopping/accelerating.
    I leaved school 25 jears aggow and can't make them anny more.
    Will you take a look.

    regards AD
  9. wannabeaflyer

    wannabeaflyer Active Member

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  10. egoexpress

    egoexpress Active Member

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    Depends on its purpose. Lead screw assemblies are slow, but ok for GA flight simulators perhaps.
    But be sure the nut is big enough, as lead screws tend to wear out quite fast, if you put alot of load on them.

    Regards
    Christian
  11. adgun

    adgun Active Member

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    Hi wannabeaflyer
    I see your post now.
    I must go to Azia and will be gone fore 2 weeks max.
    I reply when i am back :hi:
    regards Ad
  12. wannabeaflyer

    wannabeaflyer Active Member

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    :hi: Ok Ad look forward to Bouncing some ideas off you when you get back who knows we may come up with something that will help us all Fingers crossed ( May not be SCN5 standard But im sure there is a comprimise for other options out there somewhere ) have a good trip 8)
  13. adgun

    adgun Active Member

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    Hi wannabeaflyer
    Iám back
    I did take a look to your posted site,but with tr12x3 screws you can't get much speed
    (pitch to small and limited rpm)
    I made some drawings from some ideas i have
    Drawing 1: ballscrew actuator, motor not worked out.
    Drawing 2: Chain actuator ,far cheaper, meaby stepper range.
    Drawing 3: gearbox option with brake.
    Fore this i used the Banebots planetarygears they can handle 115nm max.
    They have great shaft options, and support blocks and are cheap.
    http://www.banebots.com there big series.
    Drawing 4: Some explaning when you,re working with arms,there is a catch with it, i hope i made it clear
    with the drawing


    I did some asking about steppermotors, they lose speed on load,ther torque curve is inportend
    need to be flat fore accelaration.
    They told me ,allways take far more force than needed ,and you wont get disapointed.
    Whit this in mind i did take a look @ nanotec,And find low cost planetarygears (30nm max) fore 90,00 euro
    They have more steppermotors options fore the gears,And come to 30nm holding force (30kg on 10cm arm)
    and 10nm by 60rpm (10kg trust with 600mm sec ,10cm arm)fore 125,00 euro Gear and stepper.
    I cant tell you how fast they will accelarate and brake, but you have fare more trust than needed fore a simforce gt.
    Regards Ad

    Attached Files:

  14. wannabeaflyer

    wannabeaflyer Active Member

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    :hi: Ad Glad to see you back here ... nice concept drawings .. becuse of the work i did making my cnc Router iand looking ofr a better DIY actuator for initially my Fight Simulator i also designed a Actuator similar to your 4 Skecth but came unstuck when i read the stuff you wrote explaining the limitation of stepper motors speed and power wise :( but i will post my autocad inventor drawings when i get back to work on tuesday... the other design that caught my eye was the one with the chain drive, Ian at Builtforfun has published plans for this design for free and i looked at that and was trying to combine thw best elements of bothe designs into one ( with DIY Building in mind ) will post Picyures of my Z Axis of the CNC machnie later today. if you look at it and remove the stepper motor and substitute it with a DC servo Motor then i think we would get better performance and get around the problem of backdriving ( Freewheeling with power off ) gonna go take some shots to post .... Nice work
  15. wannabeaflyer

    wannabeaflyer Active Member

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    Photos of Z axis to show were not far off in Similar design ideas but you understand the maths better and thats what missing for me :uups: for the DIY builder this design is made up of mainly off shelf items ( CNC Linear rails, Mounting blocks,and ACME leadscrew ) would like to take on board your ideas and replace the stepper with a DC servoMotor arrangement as i belive this would make this a workable option for stronger and quicker DIY actuators... Feel free to voice any opinions or problems with the deisign ( CAD drawings will be posted when i get back to work ) Just re-read your post and can now see your approach makes sense . i also checked out some info on me=oer expensive linear actuators and most if not all them seem to use DC SERVO MOTORS .. question is this the missing link? as you have showm stepper motors can be cost effective but not quick enough or at top speeds they loose too much torque and can skip pulses.. is there any way we can hook up a Stepper motor with feedback to make them in effect a DC Servo motor? or is it better to just get a scooter Motor with Position feedback and gearing to give us the speed/ power we need to make the leadscrew /nut option work as in skecth 4 :highfive:

    Attached Files:

  16. adgun

    adgun Active Member

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    Hi Wannabeaflyer
    I am looking out fore your cad drawings.
    One thing to keep in mind.
    Making a actuator ,you must allways stay in line
    When you are going out of line stay in balance (thats why i use 2 pushrods)
    Ian made this mistake :explaning:The single pushrod carrys wight and pushes down,The shain is,nt inline and
    give forces to the sky,RESULT,the wooden slider want,s to turn, the holes in it will wear out, ore wurst the wood
    will split.
    Your nice cnc axis,is out balance and line to,Result it,s want to bend ,the bearingblocks will get big hits.
    The outside shafts must only be fore giding nothing more.
    Regards Ad
    :clap:
  17. wannabeaflyer

    wannabeaflyer Active Member

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    Hi Ad just been out doing more bits to my Tronic PCB .. makes sense what you have just posted 8) will modify the design to include your features and post them for you to look at ... the Z Zxis of the CNC Machine transmit the force of the leadscrew along the centerline between the 2 guide rails ( for the cnc machnie they only have light loads ) the carrier plate is missing from these picks and drawing, mind you it should ne easy enough to update the design with the mods you recommend by just adding some more Bearing mounting Blocks.. will keep you posted as to the progress on this ASAP :highfive:
  18. adgun

    adgun Active Member

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    Hi Wannabeaflyer
    There is nothing wrong with your z axis
    Force = speed x wight
    There is no speed with cnc
    It means only ,when you cut to much at one time,you wont be precice
    Regards Ad
  19. wannabeaflyer

    wannabeaflyer Active Member

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    :hi: thanks Ad for the input :highfive:

    Best Regards

    Calvin
  20. wannabeaflyer

    wannabeaflyer Active Member

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