Any wire EDM and Laser or electron beam welding experts on line?
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    Default Any wire EDM and Laser or electron beam welding experts on line?

    I have an Indy car gear set that I need to swap the hubs on. These gears are underdrive and I need overdrive. This car was designed to run about 240 mph at 15,000 rpm. it is getting an engine that only revs to 8600 rpm and needs to go about 180 mph. I can achieve this by making up an overdrive gearset. My plan is to cut the hub out of each gear with the smallest wire available. Then swap the hubs and electron beam or laser weld them together. These gears will be required to withstand 500 ft lb of torque, 500hp at 8600 rpm. The weld area will be about 3" in diameter and about 3/8" thick. Anyone want to tackle this job? anyone know of a company that can do this job or part of this job?

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    out of interest, what is the material? 300m?

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    Quote Originally Posted by dian View Post
    out of interest, what is the material? 300m?
    The gear was made in England by Xtrac so if it is not 300M it is very close to it.

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    Can you keep things concentric enough doing this? What about balance? Is this a common practice?

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    If you are wiring out the ID, it seems like a good idea to wire a lobed spline type shape and wire the mating part. Ideal would be to have a very slight taper, maybe .5-1 deg and a press the new hub in. Although, there is some risk of warping with this approach. A shrink fit might make more sense though as it wouldn't require any taper. You might then laser weld to stabilize the lateral direction. The weld wouldn't require a lot of penetration this way. I haven't run any numbers to look at the shear load at the interface, which should really be done. It seems like you could quickly surpass the cost of a replacement gear, but maybe these gears are more expensive than I imagine.

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    Hi Moonlight Machine:
    I can't claim to be an expert on either process but I have both in my shop and I use them both a lot.

    I would be very hesitant to try this...if you are making just one gear set, you have no margin for error, no margin for testing, and you're planning a joining process you cannot fully evaluate except by destructive testing or a failure.

    The wire cutting is no great problem...you have to find a way to fixture them accurately enough to get the runout within acceptable limits (it's harder than it sounds on a wire), but beyond that, chopping out the core of the gear is straightforward for any competent wire shop.
    However, planning to re-use those hubs is a total non starter...you need a start hole, and you need to make skim passes to get the new bore in the gear properly cylindrical.
    Also, you can't just use fine wire to cut something like this...the finest commercially available wire EDM machines use 0.02mm wire (0.0008") and there are severe thickness restrictions on what you can cut with a wire that skinny. (think more like 0.1" rather than 1")
    Realistically you're looking at standard 0.01" wire which leaves a kerf of 0.0135" when you rough with it, so your slop in the set when you reassemble them is 0.027" best case with 0.010" wire

    Moving on to the welding...yes electron beam welding can make a full penetration butt weld in surprisingly thick material, (several inches) but it's not an easy or inexpensive task to make this happen, and to have assurance it actually DID happen on your final weld.

    In addition, many metals can be welded, but not all make strong welds, and the alloying elements that promote good hardening tend to make for crappier welding as a general rule, so if the gears are made from an alloy that falls into this category, you do not know how tough the weld is until you destructively test it but you can presume it's probably not very good.

    Laser welding something like this is a non-starter...if you put enough energy into it to get decent penetration, you will have ruined enough of the heat treat in the weld zone to have broad areas of HAZ, so you'll have two rings of relatively weak weld and HAZ that have to take all that torque in shear.
    newtonsapple offers a theoretically good workaround in post #5 where he advocates ovalizing the bore and new hub, in the hope it will be able to transmit higher torque without failure, but the risk is this will simply burst the gear if the welds fail by camming the lobed hub inside the lobed bore when the welds let go.
    If that were the approach then I would prefer to see a splined connection.

    If a failure occurs during racing with one of these gears, my suspicion is that a lot will be wrecked, not just the outcome of the race.
    So after all the cost and effort to make a bodge like this would you really trust putting 500 odd ponies through it at a gazillion RPM and having it sitting in the transmission tunnel right next to your leg?
    That's the million dollar question.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

    Edit: I misread newtonsapple's post a bit.
    He actually DID advocate a splined connection but lobed rather than sharp cornered, which makes sense from a stress riser point of view.
    I stand corrected, but I'd still be afraid of splitting the gear if the welds fail unless the spline lobes are large enough to transmit the full torque by themselves without the welds

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    Quote Originally Posted by implmex View Post
    Hi Moonlight Machine:
    newtonsapple offers a theoretically good workaround in post #5 where he advocates ovalizing the bore and new hub, in the hope it will be able to transmit higher torque without failure, but the risk is this will simply burst the gear if the welds fail by camming the lobed hub inside the lobed bore when the welds let go.
    If that were the approach then I would prefer to see a splined connection.
    I said lobed, but I was thinking lobed spline, something like a torx drive profile.

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    Hi newtonsapple:
    Yep, you're right and I realized my error just before you posted, so I saw your response just as I finished and posted my edit.
    Of all the recommendations so far, yours seems to me the most likely to have a chance at success.
    I'd still be wincing every time I fired up the car though!

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    Like the spline drive idea, very clever
    Mark

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    Moonlight,

    The detail that complicates welding is that 300M has a carbon content. The weld fusion zone will be at the full hardness that the 40 carbon content can provide. Brittle failure would be the risk. Some pre and post heat strategy would be required to slow the cooling rate and reduce hardness to an acceptable level. This would have to be local to the weld as not to compromise the hardness of the balance of the part. If welding was your only option then a few set-up parts would be machined, same material and geometry, to do process development on. There are a number of shops that would be happy to help. The spline idea is sounding like a little less complicated and better way to go.

    You would be hard pressed to find a vehicle on the road today with a transmission that doesn’t have at least a few laser/electron beam welds in it. All being highly stressed precision joints like yours. The difference is how many you have to make.

    Ike

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    I have never heard of wire EDM welding...new one on me....

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    Hi Ike:
    You wrote:
    "You would be hard pressed to find a vehicle on the road today with a transmission that doesn’t have at least a few laser/electron beam welds in it. All being highly stressed precision joints like yours. The difference is how many you have to make."

    Your comment is spot on...especially the bit about where you imply how many tests you have to make in order to tune the process enough to have confidence in it and how many parts you have to make to justify the cost of doing the tests

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining.

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    Quote Originally Posted by RJT View Post
    Can you keep things concentric enough doing this? What about balance? Is this a common practice?
    Concentricity will depend on the accuracy of the wire, balance as well. Never been done as far as I know.

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    Quote Originally Posted by implmex View Post
    Hi Moonlight Machine:
    I can't claim to be an expert on either process but I have both in my shop and I use them both a lot.

    I would be very hesitant to try this...if you are making just one gear set, you have no margin for error, no margin for testing, and you're planning a joining process you cannot fully evaluate except by destructive testing or a failure.

    The wire cutting is no great problem...you have to find a way to fixture them accurately enough to get the runout within acceptable limits (it's harder than it sounds on a wire), but beyond that, chopping out the core of the gear is straightforward for any competent wire shop.
    However, planning to re-use those hubs is a total non starter...you need a start hole, and you need to make skim passes to get the new bore in the gear properly cylindrical.
    Also, you can't just use fine wire to cut something like this...the finest commercially available wire EDM machines use 0.02mm wire (0.0008") and there are severe thickness restrictions on what you can cut with a wire that skinny. (think more like 0.1" rather than 1")
    Realistically you're looking at standard 0.01" wire which leaves a kerf of 0.0135" when you rough with it, so your slop in the set when you reassemble them is 0.027" best case with 0.010" wire

    Moving on to the welding...yes electron beam welding can make a full penetration butt weld in surprisingly thick material, (several inches) but it's not an easy or inexpensive task to make this happen, and to have assurance it actually DID happen on your final weld.

    In addition, many metals can be welded, but not all make strong welds, and the alloying elements that promote good hardening tend to make for crappier welding as a general rule, so if the gears are made from an alloy that falls into this category, you do not know how tough the weld is until you destructively test it but you can presume it's probably not very good.

    Laser welding something like this is a non-starter...if you put enough energy into it to get decent penetration, you will have ruined enough of the heat treat in the weld zone to have broad areas of HAZ, so you'll have two rings of relatively weak weld and HAZ that have to take all that torque in shear.
    newtonsapple offers a theoretically good workaround in post #5 where he advocates ovalizing the bore and new hub, in the hope it will be able to transmit higher torque without failure, but the risk is this will simply burst the gear if the welds fail by camming the lobed hub inside the lobed bore when the welds let go.
    If that were the approach then I would prefer to see a splined connection.

    If a failure occurs during racing with one of these gears, my suspicion is that a lot will be wrecked, not just the outcome of the race.
    So after all the cost and effort to make a bodge like this would you really trust putting 500 odd ponies through it at a gazillion RPM and having it sitting in the transmission tunnel right next to your leg?
    That's the million dollar question.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

    Edit: I misread newtonsapple's post a bit.
    He actually DID advocate a splined connection but lobed rather than sharp cornered, which makes sense from a stress riser point of view.
    I stand corrected, but I'd still be afraid of splitting the gear if the welds fail unless the spline lobes are large enough to transmit the full torque by themselves without the welds
    So I like the EDM spline Idea. Big wire is ok as well, I can make a fixture to hold the gear and hub for welding. With a .027 gap can you electron beam weld the part?
    This car has the gearbox between the rear wheels so nothing to impale the driver. This car's racing in anger days were over 20 years ago, This is a rich guy's toy and will be used in vintage "racing". This gear runs at crank shaft speed, back in the day that was 15,800rpm and 980hp so at half speed and horse power we will be giving it a try. If you don't mind pm me your cell number and I will text you some photos of the gears.

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    Quote Originally Posted by digger doug View Post
    I have never heard of wire EDM welding...new one on me....
    Read the title, it says nothing about EDM welding.

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    Quote Originally Posted by moonlight machine View Post
    Read the title, it says nothing about EDM welding.
    Re-read your own title you fooking Hick:
    " Any wire EDM and Laser or electron beam welding experts on line?"

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    Quote Originally Posted by digger doug View Post
    Re-read your own title you fooking Hick:
    " Any wire EDM and Laser or electron beam welding experts on line?"
    All others that replied were able to figure out that it was 2 questions in one title. I guess you are a bit slow......

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    OK so this isn’t going to be cheap to do right?
    So why not just make a complete new gear?
    Not cheap either.
    I suspect the mating splined rout has the best probability of working.

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    Quote Originally Posted by 72bwhite View Post
    OK so this isn’t going to be cheap to do right?
    So why not just make a compleatt new gear?
    Not cheap either.
    I suspect the mating splined rout has the best probability of working.
    A new gear is an option, a set of 2 gears will as a wag be about 5K, not at all a deal breaker but the problem is the people that do this sort of gear are flat out making gears for F1, IndyCar and the like. If I ordered now I would be lucky to get them before August or September. These are not coming off the Browning inventory list. Target date for completing this project is June 1st.

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    Quote Originally Posted by implmex View Post
    you have no margin for error, no margin for testing, and you're planning a joining process you cannot fully evaluate except by destructive testing or a failure.
    I think Marcus nailed it right here, too many variables to hit it right the first time, at least with any reasonable probability.


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