Two universeal joints between warford and driveshaft????

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Model T Ford Forum: Forum 2012: Two universeal joints between warford and driveshaft????
Top of pagePrevious messageNext messageBottom of page Link to this message  By Kevin Crouch on Friday, November 02, 2012 - 05:16 pm:

Ever heard of anyone putting two universal joints back to back?? I have a 1926 TT wrecker that I built and when I bought it, it had 2 universal joints between the driveshaft and warford. I haven't run it that way as I am putting it all back together but it seems like that would be a lot of vibration maybe, I've never heard of anyone doing that before. Any ideas???


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Friday, November 02, 2012 - 10:57 pm:

Never heard of it used in a T but it's one way to have a makeshift CV (Constant Velocity) joint. U-joints change speed. The greater the angle, the greater the change in speed during each revolution. Modern vehicles with a drive shaft use two u-joints for this reason. The angle of the second u-joint should be opposing near the angle of the first to compensate for the speed change.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Friday, November 02, 2012 - 11:10 pm:

Or the drive shaft was cut too short. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Friday, November 02, 2012 - 11:20 pm:

Is there a critical angle beyond which speed change becomes a problem?

There appears to be a con rod length to stroke ratio that's important, too, for critical angle. Note the A crank is 1/4" longer stroke than T, and the rods are longer, IIRC.

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Friday, November 02, 2012 - 11:29 pm:

I'm sure there is but I don't know what it might be off hand. Any angle will change the output side speed and this translates to anything from vibration on the low end to bucking on the high end.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Saturday, November 03, 2012 - 12:29 am:

Ralphie and Ken,

There is a max angle for a single unit joint. Doubles phased right cancel one another out and run smooth.

On the single. Not a linear plug-n-play but based on the interaction of about 5 physical factors. I'm sure that Ford did not want a derate factor going thru the joint since it was so weenie to begin with so that tightens it up a bit even further on maximum allowable angle.

My gut is telling me think in the area of 5-7 degrees max. as the cross over point of all the variables on something the size of a T in terms of load/torque/RPM. No calcs done, just the gut.

I might also think that just under 10 degrees is where that cyclic whip Ken mentions becomes unbearable for the system all by itself.

Yeah, I know what that implies and I'm not ready to go there yet. Gut is one thing, hard numbers may say another. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By William Rowles on Saturday, November 03, 2012 - 04:02 am:

It has been a long time since I studied this topic in mechanical engineering school, but I remember the input and output shafts must be axially parallel and the cross internal to each joint must be oriented properly with respect to each other, to have no output shaft rotational acceleration with two u-joints on a shaft. Maybe at the speed of a TT vehicle and the other vibrations present, the u-joint oscillations are not important for small shaft alignment angles.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Saturday, November 03, 2012 - 01:37 pm:

I think "speed" would be the wrong term but it was late. In reality, both ends turn at the same RPM--One revolution in and one revolution out. What changes is the velocity of the output side with each revolution. It's not constant on a U-joint unless it's in axial alignment. The velocity will go up and down with each revolution if it's not aligned.

That's why we now have CV joints. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Saturday, November 03, 2012 - 03:52 pm:

Logical question: would a CV joint be better in a T?


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