Drive Shaft Angle Question

[rogeroadster]

I posted a question similar to this on the early V-8 forum but thought I'd test the waters over here thinking I will get a somewhat different answer.

My generic question concerns a Model A with a closed driveline. Given that the rear end angles up toward the trans at about 3 to 5 degrees, where is that angle established? Is the angle built into the crossmember or is it built into the spring hangers? Some other means?

[Tom Wesenberg]

The crossmember design, arc of the spring, and spring hangers all play a part in the angle.

[MikeK]

Keep in mind the engine centerline is NOT horizontally parallel with the frame. In an "A" the engine sits on the motor mounts with the rear end & tranny down 3 degrees. Now add in all the factors Tom mentioned. Because of this the universal joint between the rear of the trans and the torque tube has almost no angular difference when the car is sitting on the ground with the stock spring heights.

[rogeroadster]

Originally Posted by MikeK

Keep in mind the engine centerline is NOT horizontally parallel with the frame. In an "A" the engine sits on the motor mounts with the rear end & tranny down 3 degrees. Now add in all the factors Tom mentioned. Because of this the universal joint between the rear of the trans and the torque tube has almost no angular difference when the car is sitting on the ground with the stock spring heights.

I believe that, relative to the top of the frame rails, the torque tube angles up 3 degrees to the trans. Is this angle just compensated for by the spring shackles
or the spring flex or the crossmember or as stated earlier all of the above? In other words it is not really designed in anywhere but compensated for by all the components?

[MikeK]

Originally Posted by rogeroadster

I believe that, relative to the top of the frame rails, the torque tube angles up 3 degrees to the trans. Is this angle just compensated for by the spring shackles
or the spring flex or the crossmember or as stated earlier all of the above? In other words it is not really designed in anywhere but compensated for by all the components?

It is a near zero transition at the universal joint at the front of the torque tube by overall Ford engineering design. Not a single component.. Changing any of the factors Tom mentioned, as well as changing the motor mounts, will change the universal joint angle. Adding a quick-change differential will also affect the angle.

Is there something you are trying to do or (gasp!) modify?

[Mike V. Florida]

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Modify, modify did someone say modify?

[1931 flamingo]

Tire size (big n littles) will also affect angle. As MikeK asks, what are we modifying??
Paul in CT

Mike V.: Neat program ! ! For the uninformed, what is it??

[Ron in Quincy]

I believe if everything is correct it should form a straight line from the front of the crankshaft to the end of the drive shaft housing.

Ron

[rogeroadster]

Originally Posted by MikeK

Is there something you are trying to do or (gasp!) modify?

Yes, you have revealed my underlying motive. It is a modification and I have already posted this question on the HAMB. I was just looking for any additional info I could get. I just want to know what keeps the shackles from binding if the spring is perpendicular to the frame but the rear end (torque tube, pinion angle, etc.) angles up 5 degrees?

[rogeroadster]

Originally Posted by 1931 flamingo

Tire size (big n littles) will also affect angle. As MikeK asks, what are we modifying??
Paul in CT

Mike V.: Neat program ! ! For the uninformed, what is it??

OK, here it is: Its a narrowed, stepped and stretched Model A frame under a full fendered '26 Model T roadster with a model B engine, a T-5 trans and a 37 Ford rear end. But I understand that people get offended by such actions so I try to keep it on the down low... not that I'm ashamed or anything.

[Tom Wesenberg]

Originally Posted by rogeroadster

Yes, you have revealed my underlying motive. It is a modification and I have already posted this question on the HAMB. I was just looking for any additional info I could get. I just want to know what keeps the shackles from binding if the spring is perpendicular to the frame but the rear end (torque tube, pinion angle, etc.) angles up 5 degrees?

Have you checked the angle of the bushing on the rear axle tubes?

As long as it's parallel with the spring eye it should move a couple inches without binding because the radius of the swing is so great (U-joint to differential distance).

[1931 flamingo]

rogeroadster: I'm going to assume (I know) that with the T5 you're converting the '37 rearend to open drive?? If so, you're going to be installing/making new rear radius rods to locate rearend?? The normal 3-7* angle of the u/joint/driveshaft ought to be OK with this combination. I wouldn't worry about what you're worried about unless you're talking an extreme difference between T5 output and the rearend. JMO FWIW
Paul in CT

[rogeroadster]

Originally Posted by 1931 flamingo

rogeroadster: I'm going to assume (I know) that with the T5 you're converting the '37 rearend to open drive?? If so, you're going to be installing/making new rear radius rods to locate rearend?? The normal 3-7* angle of the u/joint/driveshaft ought to be OK with this combination. I wouldn't worry about what you're worried about unless you're talking an extreme difference between T5 output and the rearend. JMO FWIW
Paul in CT

You are correct on all accounts. Most people feel that I'm overthinking this so I guess I'm just going to press on and see how it looks when it is on the ground.

[john in illinois]

The u- joints on an open shaft are supposed to run at a small angle on each end.You set this up with the angle of the spring perches. Ther are some good posts on HAMB if you do a search.

John

[Kirby1374]

With an open driveline you can adjust the angle of the ujoint at the rear by rotating the housing on the spring mount before welding them up. On a closed driveline the only way to change the angle would be to lower or increase rear ride height or monkey with the engine mounts.