Track link connector mod

[Martin Usher]

So at a loss over the weekend, wife is in Glasgow so a week or two on my own.
not sure how well you guys got on with the Aluminum connector links, i blew through a bunch trying to get the right torque on the bolt.
stripped out so many i had to open up and thread oversize, lock in insert and re-thread 3mm through with an extra 1mm of thread.

so the weekend was a little shop time and draw up the connector and run it out of 4145.
set up the wire for a simple op center profile break and rethread for outer profile 1 op and done.
I think it looks good, added a little more to the "web" area for thread, 1/4 turn more from engage and solid clamping, nothing moves, perfik...

now have to look at the next 327
not sure about cost effectiveness but nothing ventured

too heavy handed with the originals i guess.
Martin.

[Aaron Cheng]

Hi Martin,

As mentioned in my build log, I managed to sidestep that particular problem entirely by relying on cross pins to prevent the track pins from walking out, although I imagine the amount of work involved would be more trouble that it is worth for a vast majority of the other builders out there. I can torque the M3 screws with only a little bit of force to prevent them from loosening, and it also happens to clamp the cross pins a bit as well; I guess the ~0.05mm gap closes up pretty easily with aluminum, and that gap will only become tighter with coatings and paint.

If I were to assemble the tracks without any cross pins, I think the most practical way would be to loctite the track pins into the supplied connectors, and have only one connector made of wire-cut steel so you can break the track apart for maintenance. the M3 screws would only be for cosmetic purposes on the aluminum connectors, and you should be able to get a satisfactory torque spec on the steel connector to prevent the track pins from walking out on you.

As for how cost effective it would be, cutting a full set of steel track connectors on a wire EDM sounds almost prohibitively expensive, although probably still ahead of some of the other fabrication options available (CNC, stamping/forging, 3D printing etc.). Although I can understand why the team at Armortek went with (what I believe to be) extruded aluminum and would probably come to the same conclusion from a cost/benefit analysis, the relatively thin section for the threads at the bottom of the end connector was something I was worried about since the first preview we saw of the track assembly. It was stated in the build manual that the pins should be held in with loctite, so I imagine that to be the reason why we don't get that many threads.

On another note, there was a case where I ended up stripping threads in an aluminum part, albeit only partially, thankfully. In the bogie housings (CV0201) I torqued up one of the two M6x12 cap screws in the top before torquing the 25mm long screw from the side, and ended up taking around one full thread from the aluminum housing before realizing it. I was under the impression that the cup point of the screw would dig into the steel of the torsion bar end, but forgot how easy it was to strip aluminum threads! I think I may end up spot drilling the 2 anti-rotation screws in the end, and let the cone on the screw do the majority of the retention work.

-Aaron

[Martin Usher]

Hi Aaron, very in depth post, I had followed your build on the track-link mods, very thought out and engineered.
I had toyed with another option of knurling the ends of the track-pins to bite/cut into the Aluminum connectors but still was left with the soft material, I believe you are correct in assuming it is extruded tubing, already a malleable material, I did not see any signs of post treatment.

making these out of 4145 has given me the confidence of retaining the link pins alignment with the addition of the center split clamp I modified earlier, I am convinced I only need to manufacture the outside connectors and not both sides of the track link, the additional clamping forces should stop any yawing of the link walking off an end connector, time will tell I'm sure.

As to cost effective, the first two came off the machine in 12 minutes, I'm working on cut parameters for the wire for higher feed/speed where tolerance allows, lets be fair only the 4 mm holes need to the best fit and the wire accuracies over this thickness will not be an issue, i can allow fluctuation over the outer profile and inner clearance slot of which has a larger upset to match the original part.
from plate its approx less than 5 minutes to pop 100 holes for the wire, if i can get the connector wired out inside 10 minutes I'm happy, another minute or so for drilling and tapping, worth it for me.

I do have an advantage of having 6 wire machine tools at my disposal here in my shop, i sneak it in under R&D once set up i leave running and go have coffee.
still toying with the knurled idea as well, we will see.

regards,
Martin.