steel inserts for knuckle-c hub screws?

[terrible]

I'm sick of my $50-$60 knuckles loosing threads if a screw happens to back out. If they would make the interface between the two a pin, like the yeti, you wouldn't have a threaded fastener doing so much work.

Are there any one-off companies out there making knuckles and c-hubs that use a pin or even a threaded steel insert inside the aluminum C?

And I've done the thread lock in the past, cleaned screws and glued, double checked every run, did it all.

Thanks for any info!

[mikemcE]

Not aware of any, but I suspect you’re overtightening.
I was a bench technician for years on fine instruments and optics. We had torque drivers for assembly into castings and aluminum. Steel screws into aluminum tend to bottom and then tear threads, loctite can’t solve that.
I’ve never seen any RC car guys use them


Hang up and Drive

[TheLetterJ]

The Vanquish F9 portals are the only axle that I recall seeing that uses a threaded insert, might at least help visualize the idea: https://www.vanquishproducts.com/cur...ed/?fullSite=1

It is possible to install a Helicoil (or other) type thread insert in your c hubs yourself, there's several different types that are available in m3x.5

You might even be able to tap to M4 and use a shoulder bolt in place of the screw/bushing setup?

[terrible]

I've looked into the helicoil and may go that route.

I spoke with our top welder at work and he may be able to fill the threaded hole and I could re-tap but would take some fancy jig work to make sure I get the angle right.

I know 100% I'm not over tightening as well. I'm a previous optical lab tech turned electrician turned instrument tech and I'm aware of the lack of holding capacity for these small screws especially when used in such a high load environment. It's just too much of a load when using large 2.2 tires (PB rock beast) and jumping.

[mikemcE]

2.2 and rock beasts jumping, that’s just a bit of stress.
I’ve used helicoils, pita!
Welding and retapping will always work. Keep us in the loop!


Hang up and Drive

[gottorque]

I had the same issue. In my experience when tightening down the bottom knuckle screws, they just slightly bind onto the knuckle. Locktite them and let it cure, run it and after a bit of running you have those screws backing out or lost entirely.

My fix is to get new brass bushings and be sure to run an M3 washer on that lower knuckle screw. You want that clamping force to be on the bushing, not the knuckle. Once you do that. pull the tires and steering linkage off and cycle the steering. You should feel no binding with all 4 knuckles screws snugged up. Let the loctite crew and you should be good as long as the threads in the c hub are not damaged. After a few hard runs I will check torque on those 4 screws with two fingers, just to verify they have not moved.

[terrible]

Your setup reads like some one was looking over my shoulder. I've bought the brass bushings from a vendor on here and they did help for a year or so but after that the c just gives up.

What's the life span people are getting out of c hubs when used 1-2 times a week for a few hours? Am I expecting too much out of such a stressed part?

Originally Posted by gottorque

I had the same issue. In my experience when tightening down the bottom knuckle screws, they just slightly bind onto the knuckle. Locktite them and let it cure, run it and after a bit of running you have those screws backing out or lost entirely.

My fix is to get new brass bushings and be sure to run an M3 washer on that lower knuckle screw. You want that clamping force to be on the bushing, not the knuckle. Once you do that. pull the tires and steering linkage off and cycle the steering. You should feel no binding with all 4 knuckles screws snugged up. Let the loctite crew and you should be good as long as the threads in the c hub are not damaged. After a few hard runs I will check torque on those 4 screws with two fingers, just to verify they have not moved.

[TheLetterJ]

I've been running my Wraith 3-4 times a week for a couple years now, still on the same set of VP scale (clamping) c-hubs. I originally built the car as a go-fast sand car on 2.8 wheels and 4s so it's no stranger to big air time at the dunes. Now that it's set up as a crawler with 2.2"s and a 2290 servo, weighing in at 8lbs6oz rtr, it wears parts out much faster. I've wallered out just one VP knuckle bushing in that time, and replaced the wheel/knuckle bearings a couple times, but had no other issues in the c-hub/knuckle department, doing nothing more than cleaning male/female threads with contact cleaner, a dab of blue loctite, and setting my calibrated elbow to gutentight... my son's truck with Yota2 axles on the other hand, can't seem to keep the knuckle bolts tight for more than a couple battery packs.

I think having play in the surrounding parts must be responsible for just enough shock load to break the thread lock loose and slowly work the bolts loose?

You can be sure that when my c-hub threads finally throw in the towel, I'll be looking to repair them, not replace, so I am interested to see what solution ends up working for you.