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Thread: DIY TIG Pedal

  1. #31
    Join Date
    Sep 2009
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    Default DIY TIG Pedal

    Tonight I set about doing a few more bits. My time is going to be limited over the next few weeks with a garden reno so want to keep things going with a few bits at night.

    Tonight was making the pivot bolts. I want to replace the bolts with something that will let me key to the pedal and yet bolt up to the frame.

    I trimmed down the original bar in the lathe, turned one end down to 8mm, flipped it and threaded the other end M12. Then I got some larger stock and made some heads:



    The plan was to weld them together. So they got a clean and put in my drill press vice ready for TIG welding:



    Annoyingly the TIG pedal wouldn’t trigger remote mode, but not to worry, dialled the machine in to 95A and went to town:



    Back in the lathe to tidy up the ends and they’re almost done.

    669372AF-35FD-4DE7-A5B5-66D3738496FB.jpg

    I will drill a 3mm hole at the top of the heads and weld in a 3mm pin. This pin will locate in a hole in the pedal and key the shaft to it. I have some nylocks on hand to set the tension and have a plan to make lever arm bolts for the inside which will drive the pedal spring action.

  2. #32
    Join Date
    Mar 2011
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    Southern Flinders Ranges
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    Nice work, I like it.

    Might think about following your lead in a couple of months over winter and make a new one for my machine, although compact will be the nature of the brief for that, the OEM one I have is similar size to what you are building and I find it a little cumbersome at times.

  3. #33
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    Sep 2009
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    Default DIY TIG Pedal

    3mm holes drilled using the mill and a collet block to get the exact same spot on both bolts. Then I chucked a 3mm bolt in the lathe and turned the head off. Using a nut on the end I popped it in my drill press vice ready for TIG welding:

    1B4E1269-68DE-45C2-AFD0-36C45EE4FE24.jpg

    A3EF137A-6883-45B7-833D-1D124E4E2EDA.jpg

    Back in the lathe to clean up the ends again.

    381A17D6-00EB-4F4F-AE81-2C3325747AE2.jpg

    Nearly done. The fit was perfect, really tight and zero slop. The threads provided a little wiggle room and I’m sure they’ll be sturdy enough. In the end I trimmed them down to about 3mm of length so they didn’t foul the TIG pedal body. They sit nice and flush:

    486D864D-85A0-4EB5-9EC1-BB2D98B72DD6.jpg

    DACD0372-3504-4ADA-B275-F63536186BD1.jpg

    This is before trimming but gives an idea of how I’m going to try to spring action the pedal:

    C99B3C57-01A2-4869-B8AF-17A8FEBB6BAD.jpg

    I have Nylocks for the inside but for the moment I have regular nuts on until I’m ready to put it together properly. The nylocks will let me set the pedal friction level without having them back out.

    E91D2461-2913-43A1-AB08-18B74C22F2B4.jpg

    4DA77AE0-516C-4A8E-814E-3B37C47DC048.jpg

    So the pedal is keyed to each shaft. Now the question is how do I twist the shaft. Step 1 was to put a threaded extension in the lathe and turn the ends down to 18mm round:

    C363E639-2149-4CC5-AA44-6229763E4F15.jpg

    The piece above will be split down the middle and will have a piece of bar welded on:

    990F5F04-A2FF-4E13-B260-2BA226FA6071.jpg

    This bar will be shaped to provide leverage on each side and a third nut will lock this lever to the shaft in the right place.

    2E308AB3-71B1-4836-8F37-A850BA115EC9.jpg

    I have some more mechanisms to make to finish off this idea but it’s getting closer.

  4. #34
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    Sep 2009
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    Managed to make up the arms for the pedal mechanism this evening. Used the dowel to set the parts in the mill to get a radius around the ends:

    6F8724CB-DB7F-47BE-9AE4-D7225BD43825.jpg

    Welded on a rod at one end and then welded them to the nuts I made. Here you can see they have been double nutted to lock them to the shaft:

    361C12B4-2356-45A4-9B97-F13C54AD506A.jpg

    They work perfectly but they are far from elegant. Because of that I’m going to ditch them. Only about an hours work wasted.

    Im going to look to cross drill the main bolts instead and have a threaded rod run through them. This will be much neater, be simpler to install, and provide more clearance to the top cover on the lower frame too.

    I hate to ditch something that works, but if it doesn’t look right, generally I feel a better option is just around the corner.

  5. #35
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    My Tapatalk free picture uploads have ended for the month so I’m loading pics via my phone to the forum direct. Anyone know why it’s rotating some of the pictures? They’re not like that on my phone DIY TIG Pedal

  6. #36
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    Turns out 12 months of non activity gives you the chance to rethink some things and refine the build a bit DIY TIG Pedal

    Either way I’ve finished the bulk of the build, just need to wire it up, add aluminium panels for the exterior and paint the chassis.

    I haven’t tested it yet welding (obviously) but the action is beautiful. Very sturdy and solid.

    The latest incarnation has the pedal flipped. This allows the foot to sit flatter and is a little more comfortable. It’s also means I was able to simplify the return spring mechanism by incorporating it in to the potentiometer. Builders string holding it together at the moment but may have to switch to heavy duty fishing line of that doesn’t last.

    The rerun spring is also a bit on the heavy side, bearable but it may be better with a softer one. Easy replacement.

    Here it is in all its glory:



    I used 2.4mm TIG wire to make hooks on either end of the string. The return mechanism and potentiometer are done by the same string. The spring is heavy but a lot lighter than the original eBay foot pedal I bought. Plus a lot sturdier.



    Switch is controlled via a switch on the rear:



    With some paint and Alu panels I’m sure if will look great.

  7. #37
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    Oct 2011
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    Yup. That looks solid!

    Can't quite see all of it, but it looks like you have the pot screwed to a piece of steel, then the pulley and then another bush. Pots like that won't do well with a side load (we are testing some at work at the moment - guess how I know they don't like side load...). You may be better off putting a shaft through with a bush on either end and securing the pot further along so it only ever gets a rotary load on it.

    Michael

  8. #38
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    Ah poop. That’s annoying. I might see how long it takes to fail, then do as you say and make a shaft that the pot attaches to.

  9. #39
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    Hi Neevo,

    The reason that your pictures are being rotated by the forum is because the phone embeds data about the orientation of the phone. This is the "EXIF" information stored with the picture. The forum uses that data to set the picture up the same way as the phone when it was taken.

    To get rid of it you must edit the picture and re-save it ! I usually crop the picture and save it before submitting it to the forum.

    As an aside the EXIF information stores a lot more data besides orientation.
    Best Regards:
    Baron J.

  10. #40
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    Dec 2018
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    NSW
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    The part that made me wonder how it will work / fail is the string on the pot. Namely if the string slips on the pot, the signal will not match the pedal position. maybe knurling it will provide better traction? Maybe it won't even be a problem in the grand scheme of things. But when it slips and messes up a critical weld, you'll be cursing (I know I would).

    As a point of reference, this is how some of the other machines/pedals do it:

    BOC 185A acdc:
    Uses 2 pots for setting Low value (starting amps) and a high peak amperage. The pot for this is a 10K linear pot (Imagine a pot like on a linear slider on an old Hi-Fi volume / balance fader).






    For a pot, this is pretty easy to interface with 'as is'- as long as your pedal has a suitable throw, and enough mechanical stops to prevent the pot from getting creamed when you 'send it'.

    Kemppi Foot pedal (model R11)
    This one uses a linear pot again, but with a plunger type. This silver threaded knob at the top of the pic allows the pot 'start value' to be set (eg allowing a degree of foot pedal travel before amps begins to rise). This is a stout bit of gear. Very smooth operation. The box pictured bolts to the pedal proper, and is the brains of the operation- the parts not pictured are springs and pedal surface.


    EWM Tetrix foot pedal
    My latest machine- the OE pedal for this is bombproof. All cast steel, weighs about 5kg.
    Big heavy spring turns rack gear, which drives spur gear on a large 10K rotary pot. A cam assembly with grub screw on the spur gear allows for phasing of the momentary switch for the HF start side of things (seen between 2 pieces of shielding plastic).

  11. #41
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    Been following this thread with interest!
    I have connected my effort in the following circuit - and would like some critique, because it has for some reason slightly increased the indicated minimum current of my welder....
    pedal connection.jpg
    To use the welder without foot pedal, I fitted a 5-pin connector on the torch cable which connects the hand switch on the torch and shorts the bottom and third from bottom pin, to reconnect the inbuilt potentiometer by itself again.
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  12. #42
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    Hi Joe,

    The two resistances are in parallel ! So the total resistance is halved. That is assuming that the internal pot is set to max resistance.
    Best Regards:
    Baron J.

  13. #43
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    My pulley has 2 cross drilled holes in it and the string has a knot around this part to stop the string from slipping. I tested it and it’s pretty solid. The only concern I have is the string snapping.

    If that happens I will swap it out for heavy duty fishing line I think. I have some stainless rope (thin) but I can’t figure out a way to terminate it.

  14. #44
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    I made a lot of progress today and I hope it’s now at a point where it just needs final assembly.

    First up I set about painting the chassis and pedal. Went for the same machine grey I used on my welding cart:



    I’ve already drilled all the Alu panels ready for riveting to the chassis. The bottom panel will be screwed to the chassis for access.

    The Alu panels were all cut and drilled. I sanded them for a clean and relatively uniform look.



    Then I set about wiring the internals. I think I have it correct but will need to wait for the chassis to dry before I can check. I also have a new flexible cable coming for the pedal as the trailer cable I used on the old one is too stiff.




    So some assembly required before I can check to see how it’s all working. I will also add some grip to the pedal as I suspect the Alu panel will be a bit too slick. Thinking of adding on top some rubber texture.

  15. #45
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    Quote Originally Posted by BaronJ View Post
    Hi Joe,

    The two resistances are in parallel ! So the total resistance is halved. That is assuming that the internal pot is set to max resistance.
    John, the current control is done by voltage, not resistance. So the panel resistor is set to the maximum voltage for the job (originally going straight to the control module - 5Vmax) and the pedal resistor now divides that to whatever you want at the time between 0V and Vmax set at the panel.
    You are correct though that they are effectively in parallel when both are at maximum. That still sends 5V to the control module though, doesn't it?
    I actually tried with two 5k pots because of the fact that it was only showing 0.5kOhm between the source and ground in that configuration, but it changed nothing. That told me that the voltage didn't 'break down' when going across 500Ohm - at 10mA. I guess the pots could get a bit warmer at 50mW?
    Any better ideas? Always willing to learn from you!
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

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