Big Rock Almost got a full 4S rear driveshaft into my 3S but failed at the finish line

[chilly81]

I wanted to get a full 4S driveshaft into my 3s without doing a major 4S upgrade with the big arms etc. Thought I had it figured out and I was darn close. 6S Infraction hubs are very similarly sized (w/r to mount points) to the 3s rear hubs surprisingly. But they are slightly longer axially and house different diameter bearings - all which works well for the 4S driveshafts.

(Jennys prices) So for $18 for two sets (4) of Infraction rear hubs (incl. fronts and bearings for spare), $10 for a set of (4) 4S hexes, and $47 for (4) 4S CVD's, you could do the rear end of two cars. $40 each - cheaper than a set of the crap Arrma HD driveshafts by themselves, and you'd have way more beef on the outboard end.

The problem that I didn't foresee is that the collar of the 4S CVD is larger diameter than the 3s stuff. So once it's all bolted up, to be able to get it to 0deg camber, that big collar interferes with the a-arm body. You'd have to grind out a pretty significant chunk of the arm for clearance. Everything else worked.

Also, should mention it would not be good for the short arm/granite style because you'd have to cut the sliders down so far. Would be OK with the typhon ones though (still have to cut them but end up as long or longer than the arrma HD cvds).

Here's what it looked like below. So bummed... thought I had something I'd be happy with. That white thing is a spacer to step down the bearing size from the 6s hub.

I know about the 3s+4s cvd approach people have been using but I don't want to put that much $ into my 3s rigs at this point, especially when the end result is going to be a hex extender on the skinny version of the axle. It's not a coincidence most of the people who have broken the HD cvd axle stubs were using hex extenders - more leverage, bending vs. shear on crap pot metal axles is not good.

Anyway..... Maybe I will try with a spare set of arms to grind a bug chunk out of them just to see how it goes.

 

[Tex Koder]

I wanted to get a full 4S driveshaft into my 3s without doing a major 4S upgrade with the big arms etc. Thought I had it figured out and I was darn close. 6S Infraction hubs are very similarly sized (w/r to mount points) to the 3s rear hubs surprisingly. But they are slightly longer axially and house different diameter bearings - all which works well for the 4S driveshafts.

(Jennys prices) So for $18 for two sets (4) of Infraction rear hubs (incl. fronts and bearings for spare), $10 for a set of (4) 4S hexes, and $47 for (4) 4S CVD's, you could do the rear end of two cars. $40 each - cheaper than a set of the crap Arrma HD driveshafts by themselves, and you'd have way more beef on the outboard end.

The problem that I didn't foresee is that the collar of the 4S CVD is larger diameter than the 3s stuff. So once it's all bolted up, to be able to get it to 0deg camber, that big collar interferes with the a-arm body. You'd have to grind out a pretty significant chunk of the arm for clearance. Everything else worked.

Also, should mention it would not be good for the short arm/granite style because you'd have to cut the sliders down so far. Would be OK with the typhon ones though (still have to cut them but end up as long or longer than the arrma HD cvds).

Here's what it looked like below. So bummed... thought I had something I'd be happy with. That white thing is a spacer to step down the bearing size from the 6s hub.

I know about the 3s+4s cvd approach people have been using but I don't want to put that much $ into my 3s rigs at this point, especially when the end result is going to be a hex extender on the skinny version of the axle. It's not a coincidence most of the people who have broken the HD cvd axle stubs were using hex extenders - more leverage, bending vs. shear on crap pot metal axles is not good.

Anyway..... Maybe I will try with a spare set of arms to grind a bug chunk out of them just to see how it goes.
View attachment 278495

So close..!

What is that white collar made of?

Would having a narrower collar help fix the problem??

 

[chilly81]

Here's a few more pics... who knows, maybe it will spark some other ideas someone can think of a workaround. The assembled pic shows the camber with that plastic collar in contact with the a-arm. Would have to grind to get it more vertical, then of course more to have some running clearance. Also, this is a granite with the short arms - probably would hold tbh, compared to the other OEM options it's still strong. But long arms = better in this case.

So close..!

What is that white collar made of?

Would having a narrower collar help fix the problem??

That white collar is actually a 18x21x4 bushing that steps down the 21mm hole so I can use the 15x18x4 bearing that the 4S shafts want. Someone actually found a 15x21x4 bearing for me in another thread that would avoid needing that, but I had already ordered parts, and the right size bearings are only from Europe.

My terminology isn't great lol - the interference isn't that collar.... it's the big plastic collar inboard on the stub axle. You can get a better idea on the first of my latest pics - you can see that I can't bend the hub in any further because that big diameter black collar is contacting the arm underneath.

 

[Tex Koder]

Here's a few more pics... who knows, maybe it will spark some other ideas someone can think of a workaround. The assembled pic shows the camber with that plastic collar in contact with the a-arm. Would have to grind to get it more vertical, then of course more to have some running clearance. Also, this is a granite with the short arms - probably would hold tbh, compared to the other OEM options it's still strong. But long arms = better in this case.

View attachment 278518View attachment 278519View attachment 278520View attachment 278521View attachment 278522


That white collar is actually a 18x21x4 bushing that steps down the 21mm hole so I can use the 15x18x4 bearing that the 4S shafts want. Someone actually found a 15x21x4 bearing for me in another thread that would avoid needing that, but I had already ordered parts, and the right size bearings are only from Europe.

My terminology isn't great lol - the interference isn't that collar.... it's the big plastic collar inboard on the stub axle. You can get a better idea on the first of my latest pics - you can see that I can't bend the hub in any further because that big diameter black collar is contacting the arm underneath.

So instead of butchering/trimming the CVD collar to achieve more clearance and to get 0° camber.. Wouldn't it be easier to have those suspension arms with more gap around that area to allow for the larger collar?
Or design in a 'kink' to give more space to avoid hitting the collar??

 

[chilly81]

So instead of butchering/trimming the CVD collar to achieve more clearance and to get 0° camber.. Wouldn't it be easier to have those suspension arms with more gap around that area to allow for the larger collar?

Yeah you can't trim the outer diameter because it's a pin retaining ring etc. I shaved that tiny bit in those pics just to get the stub axle to stick out about 1mm further so I could get the hex pins in. That part worked great

I think you're right - if there were an arm configuration with more gap on that end it might work. I did look at RPM arms (pictures, not in hand) and it looks like it still probably won't make it. But not certain.

 

[Tex Koder]

Yeah you can't trim the outer diameter because it's a pin retaining ring etc. I shaved that tiny bit in those pics just to get the stub axle to stick out about 1mm further so I could get the hex pins in. That part worked great

So what did you use for the white collar/adapter for the bearings?
If you didn't use that.. would you be able to get your 1mm further reach??

I think you're right - if there were an arm configuration with more gap on that end it might work. I did look at RPM arms (pictures, not in hand) and it looks like it still probably won't make it. But not certain.

So just need to design a 3D arm that has the gappage needed to allow for it... no?

 

[chilly81]

So what did you use for the white collar/adapter for the bearings?
If you didn't use that.. would you be able to get your 1mm further reach??

No that wouldn't affect it. The white collar is just to make a smaller diameter. I skipped a pic where I cut it - that's probably what makes it confusing now that I look at it again lol. I pushed it into the oversize bore, then cut it off flush. Then the bearing I wanted fit nice.

So just need to design a 3D arm that has the gappage needed to allow for it... no?

That's the spirit! I think it definitely is time for me to figure out 3d printing. idk if I'd trust a the strength for an arm, but I don't know much about it. I friend of mine even has one he said I can borrow indefinitely. I could definitely at least printed that spacer instead of paying $8 shipping for a $3 bushing from McMaster Carr.

 

[dure16]

Can you just trim the arm down so it doesn't collide?

 

[chilly81]

Can you just trim the arm down so it doesn't collide?

It feels like I'm going to have to grind a lot out. But I think I'll at least give it a try - arms are cheap. It's not interfering any of the pivot material that would really weaken and let the pin tear out easier at least. It's the material in the middle like Tex was thinking.

 

[Tex Koder]

It feels like I'm going to have to grind a lot out. But I think I'll at least give it a try - arms are cheap. It's not interfering any of the pivot material that would really weaken and let the pin tear out easier at least. It's the material in the middle like Tex was thinking.

Give me a few hours..
I'll draft up a modified arm to see if we're close to making that bad boy work like it should.

 

[dure16]

Arms can be tricky to print with the inherent weaknesses of FDM printing. Layer lines adhesion and hinge pin holes don’t like each other.

Printing the arm on its side can help but comes with its own challenges.

 

[kspitters]

I totally recommend a 3d printer! I got my Creality Ender 3 S1 today, and I’m in love already.

 

[Tex Koder]

Arms can be tricky to print with the inherent weaknesses of FDM printing. Layer lines adhesion and hinge pin holes don’t like each other.

Printing the arm on its side can help but comes with its own challenges.

.

 

[Johnny b]

I totally recommend a 3d printer! I got my Creality Ender 3 S1 today, and I’m in love already.

View attachment 278569

That's very cool! Can you make a rc ramp with a printer? I'm serious...I don't know anything about them.

 

[chilly81]

Give me a few hours..
I'll draft up a modified arm to see if we're close to making that bad boy work like it should.

Ok here's a couple close ups, I tried grinding away what I could. It's getting pretty thin in that area and still needs more removed. It can get to 0 camber, but it still touching - so needs more for running clearance. Feels like I have to remove that material in the area entirely, and then it would just leave the ends of the "H" really unsupported just sticking out there without the cross bracing. The angle is looking a bit steep too now that I see it in that shot - at full shock extension - with the short granite arms at least.

I totally recommend a 3d printer! I got my Creality Ender 3 S1 today, and I’m in love already.

View attachment 278569

You should put a MMX8 in that.

 

[Tex Koder]

Ok here's a couple close ups, I tried grinding away what I could. It's getting pretty thin in that area and still needs more removed. It can get to 0 camber, but it still touching - so needs more for running clearance. Feels like I have to remove that material in the area entirely, and then it would just leave the ends of the "H" really unsupported just sticking out there without the cross bracing. The angle is looking a bit steep too now that I see it in that shot - at full shock extension - with the short granite arms at least.

View attachment 278572

View attachment 278571

You should put a MMX8 in that.

No worries..
You'll see.





**************

I totally recommend a 3d printer! I got my Creality Ender 3 S1 today, and I’m in love already.

View attachment 278569

Where (Who sunk) my Battleship Benchy??

 

[kspitters]

That's very cool! Can you make a rc ramp with a printer? I'm serious...I don't know anything about them.

Haha! My printer isn’t big enough, unless I want a bunch of parts. It definitely is possible if you print it in smaller parts and mount them together. It would take a lot of filament… the ideas are beginning already…

Where (Who sunk) my Battleship Benchy??

Mines gonna sink itself I had a mishap… check out my thread in the 3d printing section if you’d like to see, I sorta need some help

 

[Tex Koder]

Just spitballing here..

Rough Draft
ver 0.1e

(Top Perspective View)

Shaved 6mm Down from top surface of arm
(Top View)

(Bottom View)

Cross members extended below lower surface to maintain Suspension Arm integrity/re-enforcement.

I'm utilizing/modifying the great work by Kent Holthaus (aka Raven31783)
https://www.thingiverse.com/thing:3534283