Need some suggestion about the universal joint

[Tonaka]

Hi

I'm designing the drive train system. I have some idea to reduce the sprung weight by connecting the shaft direct to the wheel hub without universal joint (only one universal joint is left on the LSD side within a shaft). Is it good? if the wheels are not freely to swing (within a few degree).

I need some suggestion about this idea please....

Thanks

[Tonaka]

Hi

I'm designing the drive train system. I have some idea to reduce the sprung weight by connecting the shaft direct to the wheel hub without universal joint (only one universal joint is left on the LSD side within a shaft). Is it good? if the wheels are not freely to swing (within a few degree).

I need some suggestion about this idea please....

Thanks

[oz_olly]

While you're at it you could also get rid of your rear springs and let the drive shaft act as the spring.

Also do you know the concept of Mohr's circle? If you have a drive shaft at max shear stress due to torsion and you put a bending force on it the drive shaft is going to fail very quickly unless you make it way heavier than the weight of the universal joints you are planning to leave at the shops. It will then be a really stiff spring so you may as well use a spool because your rear roll stiffness will be so high that you will definitely be lifting the inside rear wheel.

So in short yeah you should try it, you might get a write up in Race Car Engineering.

Cheers

[Diablo_niterider]

"you might get a write up in Race Car Engineering"

[oz_olly]

Thinking about this a little bit, the only way I think you could actually do this would be to use swing arm/axle suspension and ensure the centre of rotation on the universal joint was coincident with the centre of rotation of the swing arm.

Are you planning on copying the most innovative suspension of the last 40 years?

[Tonaka]

I just think about that the moves in a few degree.
Just wana know that is there any happen if the universal join is left only one for each side??

Thanks for many suggestions

[oz_olly]

In that case think about your drive shaft as a built in cantilevered beam. If the displacement at the tip is delta=PL^3/EI you can work out how much force will be required to move your drive shaft 'a few degrees'. The force is going to be really high and put a large bending stress on your drive shaft unless you have the configuration I explained above.

How about explaining why you are trying to skimp on two universal joints.

[exFSAE]

Sacrificing design integrity in search of weight savings... see it too often with this series.

In retrospect, if I had added 5 pounds of unsprung mass (oh noes!!!1) to my design a few years ago.. by a more robust design.. that car would have driven a hell of a lot better.

[Pico]

I agree. Too many times we try to find "ingenious" ways to reduce weight by a ridiculously small amount by throwing proper design out the door. As an iterative process you start with a conventional design (everything has been tried in over 100yrs) then try improving it. Drivetrain usually runs out of weight to remove quite quickly from my experience