Russian Alfa Class

[rwtdiver]

I'm with Nick on that. And put a universal at the shaft-WTC make-up point. Give that Poor WTC motor seal-bearing a break!

David

David,

As you can see by the photo, there is already a universal joint from the motor to shaft just before it penetrates the end cap!



Do still think it needs another universal joint on the end of the shaft on the outside just after it leaves the end cap?

Rob
"Firemen can stand the heat"

[He Who Shall Not Be Named]

Yes................

[rwtdiver]

Yes................

OK! It will be done. Going from a 4mm shaft to a 1/8" will be interesting.

Rob
"Firemen can stand the heat"

NOTE: Found 4mm to 3mm Universal joints stainless steel on amazon
https://www.amazon.com/Universal-Cou.../dp/B0782T3M68

Will need to reem out the 3mm slightly to get to 1/8"! Piece a cake!

[trout]

Will need to reem out the 3mm slightly to get to 1/8"! Piece a cake!

Or taper the shaft end to 3mm.

[rwtdiver]

Or taper the shaft end to 3mm.

Thanks Tom,

Another good idea!

Rob
"Firemen can stand the heat"

[rwtdiver]

The shaft from the motor to the shaft from the prop, is dead center! using a universal joint to hook them up would be perfect. So why use a dog bone along with a universal joint? The only reason I see is ease of installation only! Why add addition sloppy connections to an already perfect in-line installation with the just universal joint?

Rob
"Firemen can stand the heat"

[He Who Shall Not Be Named]

The shaft from the motor to the shaft from the prop, is dead center! using a universal joint to hook them up would be perfect. So why use a dog bone along with a universal joint? The only reason I see is ease of installation only! Why add addition sloppy connections to an already perfect in-line installation with the just universal joint?

Rob
"Firemen can stand the heat"

Because that 'perfect' alignment you observe as it sits at the room temperature you assembled it at -- without any torque or other loads on the running gear bearings -- will surely get out of alignment when the temperature changes, and the varying degrees of physical distortion the entire structure will undergo because of that; coupled with the twisting and bending the structure will undergo in the dynamic environment of it pulling and pushing, and bending, and twisting its way through an incompressible fluid WILL put that drive shaft out of alignment with the motor shaft.

Everything to one degree or another is elastic. And the characteristic of that elasticity is a function of its physical properties, temperature and loads presented. We don't have the smarts to predict those distortions, but we have the devices to mitigate the ill effects of those distortions on our machinery.

That's why the added 'sloppiness' of yet another universal in the drivetrain.

David

[CC Clarke]

Ditto to that. As an engineer, before we "qualify" a new product before release, it is stress-tested beyond the predicted max loads expected, while operating at high and low temperature extremes and humidity levels. Once X number of units pass qual, the design is officially locked for production, No changes are allowed afterwards without re-qualifying the revision, and that is exceeding rare due to the time and expense involved.

At this level, a little slop is an ounce of prevention.

[rwtdiver]

Because that 'perfect' alignment you observe as it sits at the room temperature you assembled it at -- without any torque or other loads on the running gear bearings -- will surely get out of alignment when the temperature changes, and the varying degrees of physical distortion the entire structure will undergo because of that; coupled with the twisting and bending the structure will undergo in the dynamic environment of it pulling and pushing, and bending, and twisting its way through an incompressible fluid WILL put that drive shaft out of alignment with the motor shaft.

Everything to one degree or another is elastic. And the characteristic of that elasticity is a function of its physical properties, temperature and loads presented. We don't have the smarts to predict those distortions, but we have the devices to mitigate the ill effects of those distortions on our machinery.

That's why the added 'sloppiness' of yet another universal in the drivetrain.

David

CC, and David,

Thank you both for the great input! I now certainly understand what you both are saying.

So, Bottom line is to add the Universal Joint AND a Dog Bone! Correct?

Rob
"firemen can stand the heat"

[RCSubGuy]

My typical driveline setup sees the interface between the drive shaft and motor shaft taking the form of a dogbone connector. That offers some efficient "slop" to take into account slight misalignments. Makes installing the cylinder a snap. I steer clear of intermediate shafts that are basically elongated dogbones. Seems a lot of subs I get in have that setup. Spring for the universal if your shaft is not aligned with the motor shaft. Saves a lot of headache during cylinder installation.

Bob

[He Who Shall Not Be Named]

CC, and David,

Thank you both for the great input! I now certainly understand what you both are saying.

So, Bottom line is to add the Universal Joint AND a Dog Bone! Correct?

Rob
"firemen can stand the heat"

The Dog-Bone universal is a proprietary design. It is but one form of universal joint. There are many others. Typically a complete dog-bone assembly is the dog-bone itself and the coupler(s) it mates to.

Like this:

[rwtdiver]

The Dog-Bone universal is a proprietary design. It is but one form of universal joint. There are many others. Typically a complete dog-bone assembly is the dog-bone itself and the coupler(s) it mates to.

Like this:

David,

I totally understand the Dog Bone hook up! But I am getting mixed input as to what my original question was.



This to me is a UNIVERSA JOINT! This to me is a DOGBONE JOINT!

My question was: Do I install both a UNIVERSAL JOINT and a DOGBONE JOINT in combination together? Or just the DOGBONE JOINT as your photos show? As I stated before, I do not see the need for both!?

I am sorry if I am missing something, but I am getting mixed input!!

Rob
"Firemen can stand the heat"

[He Who Shall Not Be Named]

David,

I totally understand the Dog Bone hook up! But I am getting mixed input as to what my original question was.



This to me is a UNIVERSA JOINT! This to me is a DOGBONE JOINT!

My question was: Do I install both a UNIVERSAL JOINT and a DOGBONE JOINT in combination together? Or just the DOGBONE JOINT as your photos show? As I stated before, I do not see the need for both!?

I am sorry if I am missing something, but I am getting mixed input!!

Rob
"Firemen can stand the heat"

One or the other. Not both.

David

[rwtdiver]

One or the other. Not both.

David

OK! Thank you!

Rob
"Firemen can stand the heat"

[rwtdiver]

I finished up the supports for the main drive shaft.



I am going to finish up the stern section by adding some addition fiber glass to the stern joint and the additional support.



Rob
"Firemen can stand the heat"