Double Cardan pinion angle

[Fowler]

A while back we talked a little about pinion angle.
I have been studying everything I can find.
I have come to the point sooner than I thought where I need to know what pinion angle to set and what drive shaft to order.
The pic below show how it is setup right now (but I do not actually have the shaft or joints)
I can change the angle of the diff down some if needed but I cant change the height of the transmission
I would like to shorten the distance down form 15" if possible but I want to keep the angle down under 20 degrees (the lower the better)
I talked to a tech at Tom Woods drive shafts, he suggested I use a double Cardan joint
He also suggested I keep the drive shaft angle under 20 degrees

Its been a very long time since I was in scool and I do not remember how to figure out these angles

I'm sure someone out there knows this better than me and can figure out the drive shaft angle given the info below

Can someone help me with the math?


I just realized from the pic it looks like the drive shaft is at 7 degrees but the pic is misleading. You have to go by the #s not the picture

 

[Fowler]

I think I have been thinking about this wrong.
If my pinion angle is 7 degrees the drive shaft must be 7 degrees and where the shaft intersects with the transmission yoke dictates how far apart the transmission is from the diff

is that correct?

 

[Fowler]

I think I have been thinking about this wrong.
If my pinion angle is 7 degrees the drive shaft must be 7 degrees and where the shaft intersects with the transmission yoke dictates how far apart the transmission is from the diff

is that correct?

if I am correct in my last statement than it is the distance form the Transmision yoke to the diff yoke I am trying to figure out
I assume the smaller pinion angle would result in a longer distance

or maybe I am just totaly screwed up and dont know what I am talking about.

 

[Mykneesbehurtin]

Trying to figure this in my head i come up with length between pinion and trans as 24.4 but dont quote me on this.

 

[Mykneesbehurtin]

If you keep the 15.00 length with the 3.00 drop your angle will be 11.3 degrees.

 

[Lee H. Mann]

I don't know if this even answers your particular question.

You want both the pinion and transmission output to be parallel during full suspension travel #1 & #2.
If the angles vary between suspension compression and decompression it will cause a vibration #3 & #4.

While example #1 is perfect, the u-joints will stay static and won't rotate (work or travel) like they are designed to do.
Example #2 is about 3 degrees and that is good.

To make the proper length driveshaft install transmission yoke into transmission and use the u-joint centers on both the trans yoke and pinion yoke to measure distance between them while compressing and decompressing the suspension.
I would guess the shorter distance is when fully the suspension is fully compressed. This is normally the case when trans output is higher than the pinion.

In order not to jam the yoke into the back of the transmission when hitting bumps or simply accelerating you need to make the drive shaft 1/2" shorter at it's closest point.

Your drawing is like #3 picture for pinion angle.
Ideally you want a 1/2 degree minimum drive shaft angle to get the u-joints to actually rotate.

 

[Fowler]

View attachment 43009

I don't know if this even answers your particular question.

You want both the pinion and transmission output to be parallel during full suspension travel #1 & #2.
If the angles vary between suspension compression and decompression it will cause a vibration #3 & #4.

While example #1 is perfect, the u-joints will stay static and won't rotate (work or travel) like they are designed to do.
Example #2 is about 3 degrees and that is good.

To make the proper length driveshaft install transmission yoke into transmission and use the u-joint centers on both the trans yoke and pinion yoke to measure distance between them while compressing and decompressing the suspension.
I would guess the shorter distance is when fully the suspension is fully compressed. This is normally the case when trans output is higher than the pinion.

In order not to jam the yoke into the back of the transmission when hitting bumps or simply accelerating you need to make the drive shaft 1/2" shorter at it's closest point.

Your drawing is like #3 picture for pinion angle.
Ideally you want a 1/2 degree minimum drive shaft angle to get the u-joints to actually rotate.

I am planning to use a double cardan joint/shaft

this is setup differently than a normal single cardan joint (singal u joint at each end)

The double cardan has to u joints at 1 end and 1 at the other end to compassionate for the angle difference

From what I have read you can even get a multiple cardan drive shafts these have 2 u joints at each end

 

[Fowler]

Trying to figure this in my head i come up with length between pinion and trans as 24.4 but dont quote me on this.

I drew it up to scale on a piece of poster board and got the same

If I move the pinion up to 10 degrees I get about 13 1/4 (do you get the same)

 

[CrystalPistol]

A while back we talked a little about pinion angle.
I have been studying everything I can find.
I have come to the point sooner than I thought where I need to know what pinion angle to set and what drive shaft to order.
The pic below show how it is setup right now (but I do not actually have the shaft or joints)
I can change the angle of the diff down some if needed but I cant change the height of the transmission
I would like to shorten the distance down form 15" if possible but I want to keep the angle down under 20 degrees (the lower the better)
I talked to a tech at Tom Woods drive shafts, he suggested I use a double Cardan joint
He also suggested I keep the drive shaft angle under 20 degrees

Its been a very long time since I was in scool and I do not remember how to figure out these angles

I'm sure someone out there knows this better than me and can figure out the drive shaft angle given the info below

Can someone help me with the math?


I just realized from the pic it looks like the drive shaft is at 7 degrees but the pic is misleading. You have to go by the #s not the picture
View attachment 43007

Not sure what the question is ... but in that drawing with 7 degree angle, each half of that front U-joint will see 3.5 degree change. The joints are properly phased already, the short distance between the two halves is much like just a short drive shaft.
The rear most single U-joint in that picture looks to be straight.

 

[Fowler]

Fyi

 

[Mykneesbehurtin]

I drew it up to scale on a piece of poster board and got the same

If I move the pinion up to 10 degrees I get about 13 1/4 (do you get the same)

Ok if you still want 3.0 inches of drop with a 10 degree angle i get 17.3 on the hypotenuse side of the angle.

 

[Mykneesbehurtin]

Just google finding right triangle,then pick Cleaves Books right triangle calculator.This has a nice pic that shows all angle info along with a calculation chart,good luck.

 

[Fowler]

Ok if you still want 3.0 inches of drop with a 10 degree angle i get 17.3 on the hypotenuse side of the angle.

Thanks for doing the math for me.

I am drawing it out to scale and may be off some

This is how I figured

I measured the center of the axle out to the face of the yoke. It came out to 11 1/2 inches. (approximately)

I drew a line from the center at 7 and 10 degrees.
I made a x at 11 1/2 inches on each line
I made a 0 degree line 3 inches above the 7 degree x

so

If I rotate the pinion angle up to 10 degrees that moves the x up about 5/8 of an inch
that leave me 2 3/8 inches drop from the transmission yoke to the diff yoke.

I then measured from the intersection point at the 0 degree line down to the x on the 10 degree line

My measurement actually came out to 13 1/8

I think I mis-calculated somewhere

 

[Fowler]

Just google finding right triangle,then pick Cleaves Books right triangle calculator.This has a nice pic that shows all angle info along with a calculation chart,good luck.

http://www.cleavebooks.co.uk/scol/calrtri.htm

 

[Fowler]

using the calculator you hooked me up with I think I will go with a 10 degree pinion (with the double cardan)




something like this

 

[Mykneesbehurtin]

Make sure you show us pics along the way.