Determining Driveline Angles

[ScotI]

Originally Posted by Vegas69

Scott, if you can achieve 3 degrees of driveline angle and say 2.5 degrees of pinion with a driveshaft less than 1 degree sloping up, your working angles would be between 3-4 degrees. Under acceleration and suspension compression, your angles would get larger. You could simulate that without springs and shocks. Raising the tailshaft another degree would probably get you in the money(2-3 degrees equal and opposite). Really depends on if you want to do surgery. If I was still in build stage, I'd have cut mine for small equal and opposites. Do you have a carrier bearing mid shaft? That could complicate things here. I'm so used to everyone having 1st gens around here.

The alternative is what I've done in my car. Lower the pinion angle below level to run the smallest working angles on both end of the shaft(2.5-3). That puts the working angle on the same side of the drivshaft as Greg said. Small angles but not canceling. My driveline angle is 4 degrees(Stock). My driveshaft would rise 2-3 degrees. That makes for 6-7 degrees with equal and opposite angles which is way to much for high speed.

Yes, this is where I'm currently at. 3° @ drivetrain, .9° incline slope to the pinion, & 2.4° range down @ the pinion. I didn't think to remeasure as it cycled through the travel so my next trip to work on it I'm going to measure the numbers @ 2" travel compression (to simulate normal driving compression) & @ maxed compression (on the bumpstops).

Thanks to all that have contributed toward a solution & for sharing their knowledge/experiences.

[Vegas69]

When you say down on the pinion do you mean \ or /(Looking from the drivers side of the car) We mean \ or same plane as the driveline.

[ScotI]

Originally Posted by Vegas69

When you say down on the pinion do you mean \ or /(Looking from the drivers side of the car) We mean \ or same plane as the driveline.

The pinion is pointing down toward the front of the chassis (below level) or -2.4°. If the pinion is raised to the point that it is above level (+3°), the d.shaft would be @ an even greater incline slope (higher in the rear than it is in the front) from the trans to the pinion.

[Vegas69]

In that situation you would add the front working angle and subtract the rear. So you have -3.9 front and -1.3 rear.

Front: \/ Opposite planes
Rear:// Same plane

If it was me, I'd raise the trans or the ride height.

[ScotI]

Originally Posted by Vegas69

If it was me, I'd raise the trans or the ride height.

The alternative is what I've done in my car. Lower the pinion angle below level to run the smallest working angles on both end of the shaft(2.5-3). That puts the working angle on the same side of the drivshaft as Greg said. Small angles but not canceling. My driveline angle is 4 degrees(Stock). My driveshaft would rise 2-3 degrees.

So you had a similar issue? What did you change on your set-up if you started w/4° @ the drivetrain & 2-3° rising slope on the shaft? These numbers are close to what I was starting with (4.2° down, 1.6° d.shaft rise, & 4.5° down @ pinion)....

[Vegas69]

You have to play with your own set up. You should be able to use washers or similar to mock it up and find the sweet spot.

My guess is another 1-1.5 degrees down get's you close to equal - numbers.

With the pinion moving 1.5 you should end up with approx. .2 up driveshaft angle.


That would give you -3.2 front and -3.7 rear.

Moving the pinion 1 degree shoud give you approx. .45 up driveshaft angle.

That will net you around -3.45 front and -2.95 rear.

[ScotI]

Originally Posted by Vegas69

You have to play with your own set up. You should be able to use washers or similar to mock it up and find the sweet spot.
My guess is another 1-1.5 degrees down get's you close to equal - numbers.

With the pinion moving 1.5 you should end up with approx. .2 up driveshaft angle.


That would give you -3.2 front and -3.7 rear.

Moving the pinion 1 degree shoud give you approx. .45 up driveshaft angle.

That will net you around -3.45 front and -2.95 rear.

I understand this.... was just curious what someone that went through a similar experience started & wound-up with.

[High Miler]

Originally Posted by The WidowMaker

ive never heard it explained like that before. the program i used to set up my driveline lists that combo as a perfectly acceptable arrangement.

It is a perfectly good mathematical solution and it is sometimes used in the real world.

Keep in mind that someone wrote that program and they got their information from a collection of formulae. These formulae were developed to explain, mathematically, what goes on in an ideal, distraction free environment such as outer space. It is impossible to quantify all of the real world variables and interactions of the components affecting the drive shaft.

Every text I have listing and describing the use of these formulae contains some version of this quotation from Rockwell: "The engineer must use trial and experience as a guide".

Always design some adjustability into your drive train set up. You may not need it but if you do you will be able to tune the set up without reaching for the cutting torch.

Greg

[ScotI]

I sincerely hope this is not really aggravating everyone ..... & I apologize to those that easily see/understand the info here. I'm just trying to understand the 'whys'. We played around w/it again today. My buddy even came out to read & interpet the reference material from this thread from his perspective. I/we understand the optimum: 3.0° dn @ the drivetrain, a level d.shaft, & 3.0° up @ the pinion. Equal 'working' angles on opposite sides of the d.shaft canceling each other out.

The one question that we continued bumping up against because of our lack of subject knowledge (& that would be good to know in a situation such as this) is what are the options if that perfect set-up can't be achieved? Since several options exist when it comes to moving things, which option is the lesser of 2 evils? Is A) the incline slope of the d.shaft from the trans to the pinion w/equal & opposite angles better or worse from a physics perspective vs. B) equal angles on the same side of a d.shaft that's level or @ a slight (.1-.5) decline from the trans to the pinion?

I played around w/some settings & raised the front end an additional .500". I then checked the pinion angle as is (2.0° range pointing down toward the front of the chassis). Knowing the pinion angle, I raised the drivetrain until I achieved a similar angle (2.4° pointing down toward the rear of the chassis). This arrangement got the d.shaft just about level but the angles are on the same side of the d.shaft. I checked the pinion angle @ max drop in this configuration (just to know what it was) & it was @ 3.5°.

Greg, I'm going to try & give you guys a call tomorrow.

[Vegas69]

Driveline angles seem simple but they are confusing as hell!



Sounds like you have two scenarios:

Equal and opposite(Guessing at 2 degrees of upward driveshaft slope)

Driveline 2.4+2=-4.4 working angle at ride height

Pinion 2.0+2=+4.0

Unconventional

Driveline 2.4+or-0=-2.4

Pinion 2.0+or-0=-2.0

It's late and I'm tired, I'm assuming leaf springs?

I'd try one and if it doesn't work, change it to the other. Go by Greg's recommendation.