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Advice on repairing a shattered hollow shaft

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  • #16
    Thanks for all your replies.

    It sounds like the consensus is that a repair won't work, and I think that's probably the case. That's the way my heart has been leading. However, since it's scrap anyway I think I'm going to try the sleeve repair idea and see what happens. It's only used off-road (I switched from a UTV because this is heated and air conditioned) so whatever happens doesn't really matter much - which spells a great opportunity for experimenting!

    I hadn't thought about the clearances for silver solder - minimum recommended for full strength is 0.0015" from what I've read, so less than that would probably be impossible or present other problems. Sleeving seems the best of a bunch of bad options.

    I'd love to be able to make the part but I don't have access to cylindrical grinder to grind the bearing surfaces, or a shaper or an appropriate broach to do the internal splining.

    As for getting uses, I've been looking for around 3 months now and parts for these are rarer then hen's teeth. Most sold were manual transmissions, ATs were pretty uncommon. Add to that the fact that it's an early eCVT with exotic/unusual equipment (it uses a magnetic clutch, for instance, instead of a torque converter) and most owners in North America seem to have dumped them and converted to manuals. All of the mini truck parts places I called said they just dumped them when they came in and/or haven't seen an eCVT in a long time. Add to that the fact that I live in a remote location and shipping for a whole transmission, if I found one, would be crazy expensive, and most scrapyards won't pull a pump in my experience. I do have a call out on a minitruck forum, though, to see if someone has one sitting around, so there may be an option there. Barring that if I do have to get a new transmission I might just look at getting a manual and related parts to convert it over.

    The frustrating thing for me is that there's so little stress on this part. Before removing it I uses a drill to manually drive the shaft while the pump was still in the vehicle and I was able to get the required pressure (around 350psi) at idle input speed (~800RPM) and significantly higher at 3000RPM (highest speed I could spin it) without a problem, even though an endoscopic inspection showed it was already broken and the pieces were just sitting there engaging the shaft.


    As for JB Weld, I've heat-cured @ 200C JB Weld and it gets significantly stronger than even a 3-5 days curing. I'm assuming it just speeds the curing up and doesn't significantly change the chemistry, ie. that it would get that hard on it's own eventually. But even then, it's nothing like a weld. It does help with cast epoxy parts, though.

    I have seen some commercial epoxies with tensile over 12000PSI (JBWeld, and most metal-infused epoxies, seem to be around 4000PSI), though I have no experience with them. I have no experience with that stuff so I was hoping the yield/shear strength was high enough that it might work.

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    • #17
      As you say you've got precious little to lose at this point. It's also a bit of any eye opener to read that you were able to drive the pump with the hand drill despite the spline already being at least partially shattered. That suggests a rather like torque felt back through the drill and into your hands. Based on that a combination of supportive sleeve and silver solder might just be enough. The sleeve would provide added surface area for more strength of the silver solder and it'll aid in withstanding the pressure trying to burst the shards apart.

      Since the sleeve will likely need to be pretty thin be sure to start with a good quality alloy steel that will retain much of it's added tensile strength even after heating to near red heat temperature. and if the outside of the spline was originally fitted into a bearing perhaps see if you can find a different bearing with the same OD but a bigger ID with suitable ratings.

      You'll also want to use a more gentle sort of heat that brings everything up to the flow temperature of the solder without any hotter spots. If you do it right the final temperature will be at most a very dull reddish heat that is only visible in almost dark conditions. If you don't have any way to contain the heat in this manner it may be time to at least make up a soup can "forge" to aid in holding the heat in the part and aid in avoiding hot spots. Check out You Tube for "soup can forge".

      I would not stop looking for a spare transmission either. If you like the transmission and would like to avoid switching to the more common manual box and clutch you really should shop for a spare to use "in case" or as parts. Offroading is tough on any vehicle even if it's a gentle sort of slow and careful use. So holing the case on a rock or stump or just blowing out some other part under load is always a risk.
      Chilliwack BC, Canada

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      • #18
        1.Silver solder or tig weld, send it away to get heat treated and centerless ground.
        2.Replace existing transmission with manual.
        3.Inquire for parts sources from Japan, there are several I'm sure that would be willing to do a search of their local parts sources and ship to you. Even if you have to buy a sub-assembly rather than the one component it may be feasable.
        4.Scrap existing drivetrain and re-power. I think I remember seeing several 4 cyl. Japanes MC engine conversions, probably not a weekend project though.
        Home, down in the valley behind the Red Angus
        Bad Decisions Make Good Stories​

        Location: British Columbia

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        • #19
          Originally posted by JoeBean View Post
          ...it's a complicated part and the section that's OK contains multiple precision ground bearing surfaces that I can't replicate in my shop.
          Chuck it, part off the broken end, lathe down a flange to make a silver-solderable (or weldable) end. Might even be able to bore under that first bearing surface and then go for a press-fit. Then, make just the broken side. That end will probably involve making a custom broach, but seeing as you conveniently have said spline in sections to study, it shouldn't be that hard. Also, making that end as a section would be a lot easier than the whole part at once.

          It would not be as strong as new, but you won't have to deal with the bearing surfaces and the new bit won't really need to be hardened either... might actually be a bit tougher, when you go to reinstall it with the hammer

          David...
          http://fixerdave.blogspot.com/

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          • #20
            Originally posted by Willy View Post
            ....
            2.Replace existing transmission with manual.
            ....
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^ THIS

            Assuming it was ever offered in manual, of course.
            CNC machines only go through the motions

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            • #21
              It would be helpful if you could draw a 3-D model of the part, which may show a way to machine it. Since it seems to be operating at low torque, it might be possible to make a casting mold from the original part, temporarily epoxied or soldered (or even crazy-glued) together. If the broach for the internal splines is the main issue, perhaps you can use the mating shaft as part of a mold, and use Babbit metal or castable epoxy or other material for the splines.

              I think it would be an interesting project even if it didn't work (or last very long).

              I tried blowing up the image for better detail, but resolution is not good:



              It looks like you could make just the broken piece and then attach it to the remains of the larger part that is not damaged. I think you could make a tubular piece and then cast the broach by using the mating shaft, or a copy.
              Last edited by PStechPaul; 11-09-2016, 06:46 PM. Reason: image
              http://pauleschoen.com/pix/PM08_P76_P54.png
              Paul , P S Technology, Inc. and MrTibbs
              USA Maryland 21030

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              • #22
                Do you know what the difference is between that shaft and a more easily available one?
                May be easier to modify a more easily sourced one to fit than to rebuild that one. If it's the drive gear(?) or pump can they be modified or swapped out the newer style?

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                • #23
                  You can't fix that!! As mentioned previously, find something close to that and modify it to make it work.---Brian
                  Brian Rupnow
                  Design engineer
                  Barrie, Ontario, Canada

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                  • #24
                    If you could make the end with the splines, you could possibly cut off the broken end of the part and weld/silver solder on a new 'end', so you retain the original bearing/seal surfaces...

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                    • #25
                      In an earlier post I presented four options, but as I lay in bed last night a fifth one came to mind.
                      This may be a bit out of the box, but what about the possibility of using an external oil pump?

                      I am not familiar with the operational parameters of the CVT transmission as it pertains to your particular application but it sounds as though you are.
                      Is the pump used solely for the purpose of lubrication, or does it play a dual role of lubrication and the actuation of servos?
                      In any event is it possible to use an external belt or electric driven pump to fulfill the purpose that the pump now serves? A small external PS pump comes to mind.
                      You may have to carefully think out the oil flow in regards to pressure and return flows of the oil. Drilling and tapping into existing oil passages to gain access and installing plugs is almost guaranteed.

                      I have seen the use of external oil pumps adapted to fully automatic transmissions and engines in the past and if system pressure, flow, and the route of return oil are properly adhered to it is not an impossible goal. I realize a lot depends on each application as to the feasibility of this option. Just don't bin that CVT just yet.
                      Home, down in the valley behind the Red Angus
                      Bad Decisions Make Good Stories​

                      Location: British Columbia

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                      • #26
                        Are all Subaru transmissions of this era CVT ?

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                        • #27
                          In a word no.
                          According to the OP in post #16, most were manuals with very few automatics. Apparently the type of eCVT in this particular car were quite rare.
                          Also the vehicle that the OP references to is usually only sold in the domestic Japanese market. Kind of cute little van or truck.

                          Unfortunately the OP does not login here very often so we may very well not hear from him about this issue again.
                          It would have been informative as to how this problem was or wasn't solved.
                          Home, down in the valley behind the Red Angus
                          Bad Decisions Make Good Stories​

                          Location: British Columbia

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                          • #28
                            Such a small vehicle may be ideal for an EV conversion. With a somewhat oversize motor (especially series-wound DC) you might get by without a transmission.
                            http://pauleschoen.com/pix/PM08_P76_P54.png
                            Paul , P S Technology, Inc. and MrTibbs
                            USA Maryland 21030

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