Drive shaft angle with IRS?

[Bungi]

Greetings,

Finally starting to fab my Locost, I have a question about driveshaft angle? In the hot rod world, the common rule is to tilt the engine down about 3 degrees and the differential up the same, to keep vibration down, and some in depth engineering stuff about velocity of the u-joints... My question is when using an IRS with the differential mounted "solid" do you still have to tilt the motor down and the diff up? My layout has a 1" change in elevation from the trans to the diff, and a driveshaft length of 19", will it matter if I mount both the motor and diff horizontal?

Thanks
Bungi

[davew]

As long as the output angle and input angles are PARALLEL, [ not tilted at each other] you will be good with a 1" change.

[Miatav8,MstrASE,A&P,F]

With a sprung/moving axle, in general, the pinion should slope down compared to the trans output shaft and they should be parallel with matching angles at each joint. The goal is to have the same operating angle at each joint to cancel each other out and for everything to be straight under full power with traction. The actual best angles depend on the rear suspension geometry and loading.

With an irs with an essentially rigid pinion mount, everything should be between straight or up to a 1/2 degree off (at each joint and the same at each joint. Your diff is likely to be offset a 1/2 inch to one side already if you center the diff housing, so line the shafts up as best you can. Use a digital gauge and a scissor protractor if you want to check lateral angles.

I didn't calculate the actual joint angles with a 19 inch shaft at one inch offset but they need be minimized within reason.

Where is your build log?

[Miatav8,MstrASE,A&P,F]

Yeah, that's what I though.