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.

[Chris.Marshall]

Hi All,

Jut another 'thought experiment'....

I'm not building a leopard (T1 on the go) but I was looking at a challenger 2 project, pretty much a 'thought project' only, but did spend some time thinking about track links. I had a potential idea to make the link pieces in steel by pressing..... The idea was to produce a round thick wall tube that when pressed into a die would produce the ' 8 ' shaped link. The initial tube would be turned and drilled / bored to the correct dimensions so that when pressed the size would be correct. The pieces would be parted off so that the width of the link was correct and only pressing one link at a time would reduce the required press force to acceptable for a basic fly-press. The die would be machined to the outer profile of the link piece with the bottom half as a 'cup' and the top moving piece sliding down into it, the main thing being to stop the link piece 'spreading' outwards and flattening during the forming. If the link did flatten a bit then potentially pins could be used. Finally after forming, a little jig to re-ream the pin holes to size.

Just my thought on how I would make these out of a stronger material.

All the best,

Chris.

[Martin Usher]

Hi Chris, it's always good to think of different ways to produce components, in large or small quantities.
reading your thoughts I personally think it would be a long expensive process, mainly in sourcing a bar to drill and bore as opposed to sourcing extruded tube at correct O/D - I/D and wall dimensions, that's not to discount the idea.
making said swage/punch block to suit, single link or multiple link production.

talking to suppliers regarding this track link connector, fabrication - plasma cutting etc. most are not interested of course, small numbers are a cost loss and not profitable, even doing me a favour.
Even running my own on a wire EDM I am looking at other options to produce, there's always improvement to be found, just keep looking.

Martin.

[Chris.Marshall]

Agreed Martin.

It's not a simple component to produce to the right spec in high quantities. I did find a standard solid drawn tube that looked 'near enough' to produce the pressed link piece, but the finished dimensions of the part would probably be just that bit different from the current design in terms of track and sprocket pitch. Not hugely off, but just a little that it would need adjusted by producing different sprockets, pitch / diameter. In full size, modern 'live track' is actually quite sophisticated where vehicles are running at very much higher speeds than the past. BUT, a fascinating subject all of it's own....

Chris.

[Martin Donnison]

Just sharing my view on this topic. I agree if your to heavy handed with the wrench you will strip the threads.

I simply used high strength loctite then fitted the screw.
I have had no issues with any of the track links. Left one link unglued for removing the track in the future.

The end of the two rods don’t need to move they just need to stay there all the hinging is done in the length of the track link.

Thanks Martin.

[Steve McEvoy]

After a few runs with my Leo I have had a few links walking out. All screws as tight as I could physically get them and I was still able to pull some off by hand although they seemed tight. I have now bought some glue specifically for metal to metal. undone the screw and slid the connector off about 2/3 of the way applied glue to the connector and slid it back in then tightened the screw. On one connector especially loose I applied the glue and pushed the connector back in place without tightening the screw. After 20 seconds I couldn't even prise the connector off, so locked the screw and all seems good. will update when I have had a few runs. As for stripping the threads I think it's easier to round out the head of the screw which seems to be made of some sort of cheese!! Only one I stripped was when I didn't realise that some of the screws in the 6mm pack were actually 5 mm all the 6 mm screws lock up fine. The glue is called Naymaer metal glue . Thanks to Adrians help I now have working light switchable from the controller and also working indicators! he also set it up so I have high speed and slow speed, I found high speed from initial settings just too fast to be controllable so low speed set to 50% high speed set to 75% and it now drives lovelly.

[Steve McEvoy]

Quick update on my build. Think the metal glue seems to be doing the job on the track connectors. Thanks again to Adrian I now have working indicators and they look great. Bit too chilly for me in the garage at the moment, after chemo I now suffer with pain in my hands when it's cold so it may be a little while before I get back to it. (Don't think the wife will let me centrally heat the garage !) On another note after a few runs on the road I have found 4 track pads missing which on the road you can find them but if it happened in a field pretty sure it would be a lost cause. Not sure what bonding process was used but it does seem a bit suspect. Managed to find 3 of the pads so I am trying to see if Locktite 480 will work to reglue them on, or if anyone has a better suggestion for a better adhesive, any advice would be most welcome.
Regards
Steve

[Steve McEvoy]

Well I have finally got all the track pin ends glues and screwed at last. Had a session driving on tarmac yesterday and happy to say they have all stayed in place. The problem persists with the rubber pads coming off, not sure what glue was used to bond the rubber to the metal backing plate but it's certainly not up to the job, there is no evidence of any glue on either the metal plate or rubber pad. While it is not so much of a problem driving it around the house because I can find the pads, but when driving the tank at shows you would have pretty much no chance of finding the pad so would have to replace the whole part. While there are spares supplied going at the rate that I have lost them they will soon run out. Hopefully I will be able to buy the rubber block on it's own. In the greater scheme of things this is not a major issue just annoying. I have re bonded the ones that had detached with Locktite 480 and they are holding fine. Must say this has been a fantastic kit to build.