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magnumb

Drive Line Angle

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Oh yes.  

I learned (from TC) that if it's not properly lined up, your Bruiser would go like 100% throttle, 60% throttle, 100%, 60%, 100%, 60%, at every turn of the drive shaft.  Even though it is at full throttle.  

 

nwf5TaL.png

Sometimes you see parts like below...

But it's badly made.  Both ends must be "mirror images" of each other.  

If these parts pull apart (some may not), you might be able to put it back at the correct angle.  Sometimes, teeth don't line up perfectly, but like 15 degrees off or something.  That depends on how many teeth/splines there are; 3 teeth can be turned at every 60 degrees, 4 teeth would be every 90 degrees, 5 teeth would be every 72 degrees, 6 teeth would be every 60 degrees...  

Even at the wrong orientation, the top one doesn't line up.  Even if you could turn it 90 degrees the both ends still won't line up. (you can't turn 90 degrees. With 6 teeth/splines, this will only go 60, 120, 180, etc)  The bottom one is still off, but better than the top one, but still can't make it right.  So this manufacturer didn't pay any attention to the "Phasing."  

Below parts will create vibrations.  

  XTF9Jsw.jpg

RC Car Action explains below. 

texqPTq.jpg

Throw CVAs in this equation, it gets more complicated.  Sometimes simple dog bones work better.   

 

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1 hour ago, magnumb said:

I've noticed some of my kits do not have optimal drive line angles as displayed below.

Which kits are in question?  I've noticed on the CR01 it can matter as the shaft angle is too steep. If you pick it up and allow for full suspension droop and gun the throttle, the whole model shakes badly. Overall, I'd say its less crucial on scale models. On full size cars, I aim for roughly equal transmission output yoke to pinion +/- 3 degrees unless I'm setting up for drag racing, in which case I sometimes angle the pinion downward a bit with angled shims on leaf spring cars. Full size cars should never have the driveshaft set up with no angle like the first "prefect-inline" drawing in @Juggular's post. Automotive U-joints contain needle bearings and some angle is required to allow the needles to process (rotate within their cups). Even a fixed rear diff IRS cars like the Corvette have a little bit of angle built in. This isn't a consideration in RC.

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I've read somewhere that beyond 3 degrees, it would wear out faster.  But most RC cars have far greater angle than 3.  Big trucks too.  After all, that's why they need universals.  

Then again, many 1:1 have double cardan joints.  Two are built into one joint, so double cardan automatically takes care of the phasing at each end, but both ends must have double cardan, otherwise, one side that is not double cardan will have phasing issues and the other end won't cancel the effect.  But, for RC cars, this would add too much weight and expense.  (there are expensive 3rd party parts)

5kEb6cV.jpg

I wonder below is what @Saito2 is talking about?  It's kinda cool looking! (I wonder if I have a bearing fetish...)

DJM4V0N.jpg

 

 

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Related image

 

What I was referring to is the "ring" of needle bearings pictured above between the thrust washers and multi-lip seal. They ride inside the 4 bearing cups on the trunnion surface of the cross. Without any angle, the needles just sit there and eventually wear out. They need to process.

The nifty pic @Juggular has is of a spherical roller bearing which IIRC allows some degree of angular misalignment.

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I see!  Some of those pins would just be pressed flat if the drive shaft is perfectly aligned! 

But if there is an angle, they would have to roll back and forth.  

(Frankly, I didn't even know 1:1 had these rolling pin bearings. But it makes perfect sense--in hindsight) 

Clever stuff.  Thank you clearing that up.  

 

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