Need some help interpreting. Here are the parameters I’m going off of from spicerparts.com. The first set of calculations is for my vertical drive angles, and the second set of calculations is for my horizontal drive angles (Ford with an offset rear axle). Also, can someone explain rule #2? So if I’m understanding correctly, in the vertical calculations attachment, my 2 calculated operating angles are within spec, but the driving member and driven member are not within a ½ degree, hence violating rule #1 above? In this case I would need to put wedges in the back to tilt the pinion up to be within ½ degree of the output shaft? Because the output shaft is 3.5 degrees down. The second set of calculations (horizontal offset) violates rule #1 right? What about #2? Otherwise the two calculated operating angles are correct (within the recommended 3 degrees)?
Assuming your transmission is 3.5 degrees down, your pinion should be 3.5 degrees up. Rule number two allows for .5 difference so you can be at 3 degrees up or 4 degrees up. I hope this helps
I am thinking the op was after angle of driveshaft and allowable rpm... With 3.5 Down on trans, 3.5 up on rear end... Your driveshaft u joints see 3.5 depending on ride height etc.. that is the thing not taken into consideration. Driveshaft angle comes into play more than people realize. Anything under 6 degrees per end is allowable in my school of thought.. Or eliminate ujoints and put cv joint at trans and ujoint only at rear axle.
You lost me at the word math,but in practice most cars of the 50-70"s have a offset pinion.The Ford Explorer is about 2 inches,and guys run them in 55 Chevys.If you are narrowing a rear housing you can center the pinion.My 9 inch has a centered "center" for looks with a 1 inch pinion offset.Well within operating range for a ujoint.
Sounds like a complicated way of expressing things? I see it that rule #1 says there has to be an angle of sorts on the uj - ie it specifies the lower end of the scale. So if you have an angle you can call rule #1 covered. Chris
You do realise in your vertical calcs that the front operating angle of 2.5 is derived from an engine up 3.5 and driveshaft up 1, giving an angle of 2.5. Engine up and driveshaft up? Chris
If I understand your calculations, it appears the operating angle of the front u-joint is 2.5 degrees and the rear u-joint is 2.3 degrees. If that's correct then the difference is 0.2 degrees which is perfectly acceptable. You should also realize that these are static measurements. Once you accelerate or decelerate the nose of the pinion will move up or down changing the angle. The shorter the drive shaft the more the angle changes. In heavy truck the shaft between the diffs could give vibration on decel only or accel only because of the angle change. Even when correct they didn't fall in the 1/2 degree recommendation. FYI, the 1/2 degree minimum is so that the u-joint bearing will rotate slightly to keep from brinelling the the cross.
Comments - Rule 1 is really applicable to a situation where the driver and driven equipment are fixed in relation to each other; e.g., a car with independent rear suspension (chassis mounted differential), or a motor driving an industrial pump. In a car with a sprung solid rear axle, there are so many relative movements of the axle, due to passenger load, fuel load, acceleration and braking torque, road undulations, etc., that sufficient misalignment will be provided 99% of the time. Many rear ends have an offset pinion, e.g., Ford 9" has a 15/16" offset*. Some cars have the engine offset the same amount, to minimize UJ operating angle. If the driveline were perfectly aligned in profile (side) view, with a 40" driveshaft and 1" offset, each UJ would have an operating angle of about 1.43 degrees. (Note that this alone would satisfy Rule 1.) If there were also an operating angle in the profile view. the two are additive as vectors. Don't worry about the math, but the true operating angle, assuming an equal 1.43 degree angle also in the vertical, would be about 2.02". If you have a full tank of gas and a chubby wife, and you hit a speed bump, taking up an extra two inches of suspension travel, the vertical UJ angles would increase by about 2.86 degrees, giving abob- true combined operating angle of 4.52 degrees. (Or may decrease it, depending on the static layout.) Is this excessive? I don't pretend to be more knowledgable or conservative as Spicer, but I note the following regarding the E-Type Jaguar rear axles, which have the same Cardan/Hooke type UJs, on approx. 13" shaft length. An assumed 2" upward wheel movement would subject the inner UJ to an 8.9 degree rotation; a bit less on the outer, due to wheel camber change. * (Note that "offset" is not the difference in axle length, but one-half of that. Many people get confused on this.) I don't follow your calculation for horizontal angles. Typically, even with pinion offset, the centerline of of the transmission and pinion are parallel, in plan view. Therefore the UJ angle at the front and rear are of equal magnitude, and do not contribute to the difference in operating angle referred to in Rule 2. You have not provided the offset or drive shaft length, so I can't confirm the angles you have determined. Bear in mind that, as discussed above, the horizontal and vertical angles must be combined (as vectors) before comparing to individual UJ acceptable operating angles. Obviously, the shorter the driveshaft, the more pronounced angular offsets become. These are further aggravated by axle housing rotation under acceleration/braking, if such rotation is not well controlled, e.g., if axle is located only by soft, parallel leaf springs.
As an example, longer equals shallower arc, shorter is deeper, exaggerated diagram however it gives you an idea. Whilst on topic consider the slipyoke and how much of it is exposed, it requires sufficient travel to allow for driveshaft movement during the suspension cycles, acceleration and deceleration remembering that it moves in and out of the transmission extension housing.
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