Announcement

Collapse
No announcement yet.

Welding steering rack pinion? heat treatment and cracking?

Collapse
X
Collapse
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Welding steering rack pinion? heat treatment and cracking?

    Thinking about properly depowering the MX5 power steering rack, which involves welding up the torsion bar system in the pinion:



    A la this thread: https://motoiq.com/project-miatabusa...eering-rack/2/

    While im not so worried about the actual welding, im a little concerned as to whether this will introduce some nice big heat stress points to later fracture. Or am I just overthinking the stresses involved on that part?

    Wondering whether it might be worth silicone bronze brazing them together, to try and keep the heat down.

    Internet welding experts?
    Chris
    ------
    The new nugget
    I never saw a wild thing sorry for itself. A small bird will drop frozen dead from a bough without ever having felt sorry for itself. - D.H.Lawrence

    #2
    I've done it a few times.

    The play in the pinion even without welding is minimal, so, were a weld to fail, it'd hardly be noticeable if at all. You certainly aren't going to be compromising it anywhere near enough (with the heat of the weld) for it to fail to a point where it is worse than it was before the welding.
    Nonetheless, I've never heard of anyone having them fail on the MX-5/miata.

    Time Attack Turbo Build Thread // BEAVISMotorsport.com // YouTube.com/bbeavis

    Comment


      #3
      Bad ju-ju about the weld right on the notch. Perfect joint for brazing. I'd probably go that option
      Mit freundlichen Gre

      Originally posted by Keith Duckworth
      "I think that in a racing engine, the closer it is to disintegrating, in general the better its performance will be "

      Comment


        #4
        I wouldn't weld it like that - (all around) given the failure mode (aka a small amount of slack) vs introducing a heat affected ring around the entire shaft.. - i mean, you are talking about a situation where you have crashed/guttered heavilly before it's going to be a problem - but even so.. a couple of well penetrated stitches would probably be safer or even a mechanical means of removing the slack - keyway or something..

        If it was me - I'd probably weld that slot & then put a stitch on the other side of the shaft too, getting it clean is going to be a cunt though.
        This is a post i wrote by mistake, which is nice...

        Comment


          #5
          Silicon Bronze would work fine but I very much doubt that welding with regular ER70S6 or S2 would be a big deal. You're more worried about the bearing area than anything, so whatever works. I'd use some heat fence to limit the heat affected zone unless you are a gun with the heat control.

          Comment


            #6
            How much stress do you think you are going to put in it? Even in rotating shafts you can put in something like 80 mPa and it is ok for infinite life.
            3D scanning
            3D modelling
            Structural certification
            3 and 5 axis milling

            Comment


              #7
              How much leverage can you apply to a shaft with a ~175mm lever arm and 2 hands held out in front of you?
              Pretty sure you could get away with just packing the splines full of devcon.
              "Where can we get hold of a Vincent Black Shadow?" "Whats that?" "A fantastic bike," I said. "The new model is something like two thousand cubic inches, developing two hundred brake-horsepower at four thousand revolutions per minute on a magnesium frame with two styrofoam seats and a total curb weight of exactly two hundred pounds."

              Comment


                #8
                Originally posted by Gammaboy View Post
                How much leverage can you apply to a shaft with a ~175mm lever arm and 2 hands held out in front of you?
                Pretty sure you could get away with just packing the splines full of devcon.
                How much force is counteractively applied to the rack in the opposite direction though. According to the old Caroll Smith stuff, the shock loads into the pinion are quite high.
                Chris
                ------
                The new nugget
                I never saw a wild thing sorry for itself. A small bird will drop frozen dead from a bough without ever having felt sorry for itself. - D.H.Lawrence

                Comment


                  #9
                  You still need to hold the forces with the wheel on the other end?
                  3D scanning
                  3D modelling
                  Structural certification
                  3 and 5 axis milling

                  Comment


                    #10
                    Have a look at the size of the key/keyway or splines used on steering wheels - there's not a huge amount of shear capacity there in the cast alloy steering wheel hubs. Compare that to the strength of a weld on a 1" diameter steel shaft?
                    I agree though - a full circumference weld is probably not the way to do it - 2 or 3 short stitches should be enough without putting too much heat in.
                    "Where can we get hold of a Vincent Black Shadow?" "Whats that?" "A fantastic bike," I said. "The new model is something like two thousand cubic inches, developing two hundred brake-horsepower at four thousand revolutions per minute on a magnesium frame with two styrofoam seats and a total curb weight of exactly two hundred pounds."

                    Comment


                      #11
                      Originally posted by PLAYA View Post
                      You still need to hold the forces with the wheel on the other end?
                      More that any slight movement in the pinion will act like an impact wrench. Plus the wonderful nature of heat treatment fractures.

                      Originally posted by Gammaboy View Post
                      Have a look at the size of the key/keyway or splines used on steering wheels - there's not a huge amount of shear capacity there in the cast alloy steering wheel hubs. Compare that to the strength of a weld on a 1" diameter steel shaft?
                      I agree though - a full circumference weld is probably not the way to do it - 2 or 3 short stitches should be enough without putting too much heat in.
                      Plenty of evidence of shear failures of boss kits. No way im going to weld one though.

                      still thinking it might be worth silicone bronzing it instead, or even silver solder to wick down into the cavity, with then a layer of silicone bronze ontop.
                      Chris
                      ------
                      The new nugget
                      I never saw a wild thing sorry for itself. A small bird will drop frozen dead from a bough without ever having felt sorry for itself. - D.H.Lawrence

                      Comment


                        #12
                        Originally posted by Gammaboy View Post
                        Pretty sure you could get away with just packing the splines full of devcon.
                        When I manualised my rack, this is pretty much what I did. I wasn't keen on welding it either.
                        I removed all the PS valving, made up some steel shims to lock up the two shafts, then filled it all with JB-Weld to keep it all in place.
                        6yrs later, it's all still good.

                        The advantage of doing it this way too, is if it does fail, I wont have a steering failure.
                        Where as if welding caused cracking of the shaft, you could end up with disconnected steering.

                        Comment


                          #13
                          Originally posted by Gammaboy View Post
                          Pretty sure you could get away with just packing the splines full of devcon.
                          My first thought was JB Weld but devcon will do !!

                          Don't mention the adBlocker !!

                          Comment


                            #14
                            Road car steering columns are generally tested at 100Nm for maximum input torque. It takes a LOT of effort to wind in 100Nm of torque to a steering wheel, most people can't even get close to this. This represents worse case loads when you have a wheel up against a gutter and you yank on the wheel.

                            Is this for a track/race car? Steering columns in F1 cars for example are designed for much lower loads, typically 40Nm peaks.
                            "What in the gay caped fuck is that?" by Shonky

                            Comment

                            Working...
                            X