A-ARM BUSHINGS

[Rottster]

Patiently waiting for Scorched pins and front retainer to arrive....

@Big Kid, just a thought.... Having supports at the front and rear of the A-Arm wouldn't prevent it from bending in the middle, correct? Wouldn't having a full length insert be more rigid through forces on any stress plane?

 

[Big Kid]

All the forces of a long bearing surface when axially loaded are on the extreme ends & where the wear & load will be greatest.
So a slightly closer fitting sleeve bearing/s ONLY on the extreme ends is all that is required.
By having the Virgin pin bore between the installed end sleeves basically floats and does not impart any or minimal rotational drag.
* Also being the insert sleeves offer zero mechanical structure strength to the A-arm installed within, where as a full length sleeve removes much more material of the A-arms structure at the pivot pin end .... Doing so would make a weaker A-arm in general & that is not something we really want to be doing

* Now here is a couple pictures that can show this well ... AND NOTE: this is a failure from striking an Oak Tree while traveling at a pretty good clip ... no different than a full size automobile the Tree Wins every time !!!

 

[Rottster]

All the forces of a long bearing surface when axially loaded are on the extreme ends & where the wear will be greatest.
So a slightly closer fitting sleeve bearing/s ONLY on the extreme ends is all that is required.
By having the Virgin pin bore between the installed end sleeves basically floats and does not impart any or minimal rotational drag.
* Also being the insert sleeves offer zero mechanical structure strength to the A-arm installed within, where as a full length sleeve removes much more material of the A-arms structure at the pivot pin end .... Doing so would make a weaker A-arm in general & that is not something we really want to be doing

* Now here is a couple pictures that can show this well ... AND NOTE: this is a failure from striking an Oak Tree while traveling at a pretty good clip ... no different than a full size automobile the Tree Wins every time !!!

View attachment 357510

View attachment 357511

View attachment 357512

Agreed to a point, but you're thinking front/rear loads and Brother, been there, lol. I ran my first Big Rock into a Granite block @ 50 mph and I was assessing damage for a few days. Doing some easy kinetec force calculations, it was about 570 ft. Lbs.... The same as 10mm round out of a 5" barrel but the load spread out over the entire rig of course. The whole scenario really gave me respect for the damage one of these out of the box RC cars can do.. BUT, when I said "Any Plane of Force", I truly meant it. I think I bent those lower control arm pins on a wicked cartwheel which would be a major lateral force. Not up down, not front rear, but lateral. The pin is bowed in the middle in which a wicked strong opposing end bearing has very little strength. Now, if that force is distributed equally along the entire pivoted length, it should prevent bowing. This also why straight six engines can't handle the HP that a V8 can, at least without additional main bearing caps. Also, look where it popped, not at the ends but the middle.

 

[Big Kid]

The Insert sleeve bearings just snug up the ends against the pin reducing axial motion. The bore between inserts is OEM spec diameter & in the situation your speaking of would have similar pin damage if the direction of the impact forces were similar ... IMO

In my case of the break, the buggy ( Typhon ) entire weight / mass was on the left Front wheel / a-arm upon impact with said tree. A very similar situation might be if jumping said buggy and landing on the front end upon 1 wheel only w/o any defection angle ... YUP broken parts !!!

 

[Rottster]

The Insert sleeve bearings just snug up the ends against the pin reducing axial motion. The bore between inserts is OEM spec diameter & in the situation your speaking of would have similar pin damage if the direction of the impact forces were similar ... IMO

In my case of the break, the buggy ( Typhon ) entire weight / mass was on the left Front wheel / a-arm upon impact with said tree. A very similar situation might be if jumping said buggy and landing on the front end upon 1 wheel only w/o any defection angle ... YUP broken parts !!!

Ok, I'm terrible at explaining stuff sometimes... Imagine a compressive force on a bar that's supported on either end. The middle is going to bend regardless of the rigidity of the ends, it's the weakest point. The best defense is a tube "column" that's larger than the bar, not a stronger attachment point. This is why motorcycle axles have gone from 22m solid to hollow 40mm tubes. The strength of a round is on the outside diameter, the inner does very little.

For example, take a toilet paper tube of let's say 1/16" wall thickness that's about 3" in diameter. RIGIDLY attach that to a platform and keep adding weight. Now let's take that same wall thick @ 1/2" diameter and keep adding weight. It'll fail right in the middle. The same goes for any force at any plane on the same columns including torsion.

 

[Rottster]

So my new pins (just arrma stock stuff) and the Scorched Hinge Pin Holder arrived... New pins slide right in with a touch of resistance, maybe a pound or less. rather than use my typical 3m dry lube, I'll fall back on my go to Lucas extreme duty gun lube.

 

[Big Kid]

So my new pins (just arrma stock stuff) and the Scorched Hinge Pin Holder arrived... New pins slide right in with a touch of resistance, maybe a pound or less. rather than use my typical 3m dry lube, I'll fall back on my go to Lucas extreme duty gun lube. View attachment 359176

Krytech WAX lube ... No dust attraction perhaps ?

 

[Rottster]

Krytech WAX lube ... No dust attraction perhaps ?

@Big Kid, I was thinking (at my detriment possibly) that there's no space for dust to collect now that the tolerance is literally easy thumb pressure. Very much like a bolt or slide on well fitted firearm. Time will tell of course! The 3M 08897 I use on exposed parts has been performing in a exceptional manner so far.

@Big Kid I was hoping that someone offered a titanium lower A Arm pin solution, but I'll test it as it is. I could break an anvil with feather so...

@Big Kid, actually, a well tempered 5160 spring steel lower pin would be ideal in my mind.

 

[rgfast]

I like seeing others trying this mod, I look forward to seeing how the stainless works long term. When I first started throwing idea's around in my head it had nothing to do with making the arms stronger but to rid them of the slop that they all have. I can't see where spreading the load across the whole arm doesn't strengthen them to some degree, but hey I don't have an engineering stamp behind my name either LOL. All in all there is always five ways to get to the same spot this is the route I took and hope it helps others find success in the hobby that we share here together.

 

[Rottster]

I like seeing others trying this mod, I look forward to seeing how the stainless works long term. When I first started throwing idea's around in my head it had nothing to do with making the arms stronger but to rid them of the slop that they all have. I can't see where spreading the load across the whole arm doesn't strengthen them to some degree, but hey I don't have an engineering stamp behind my name either LOL. All in all there is always five ways to get to the same spot this is the route I took and hope it helps others find success in the hobby that we share here together.

Well, we're going to find out! I just finished off the right arm and the difference in slop seems amazing at this point..... But I really need to get both done and start from there in regards to longevity. Some days I feel like I'm the worlds crash test dummy, maybe this time, I can make it work without pain.

 

[Rottster]

Slop is essentially gone. I have no more excuses for crashing , lol.

 

[Rottster]

OK, I'm yanking on this thing hard enough to take 2 hands....