Odd setup... Sometimes not so odd

[Lou_tribal]

Hello fellows!
In some post earlier this year I posted a picture of my setup (well my boat setup) from tranny to stern tube showing two universal joints (a.k.a. cardan) and some were pretty surprised by this. I got some comments that this was an unusual setup and that I should remove all of this and redo it properly and got the same from people at my marina (to be clear I am not saying it was an offense to me).
As I like to understand why things are what they are I did some searching and find out that even unusual it is a setup found in some fishing boat.
Here is a screenshot from a book of boat mechanic:


My setup is shown on the top left.
Still learning everyday about my boat, even during winter.

Cheers!

L

 

[C lectric]

Uncommon but not oddball. Most engine crankshaft centrelines are in line with the shaft but not all are built in that manner. Those saying it should all be changed , I will bet, are not aware that the engine crankshaft, shaft and prop centre lines are not inline.

If the crankshaft centreline were changed to be in line the engine would have to be raised an unsatisfactory amount.

 

[DavidM]

If the crankshaft centreline were changed to be in line the engine would have to be raised an unsatisfactory amount.

Or use a downangle transmission. That is the most common solution to the problem of engine placement and alignment with the prop shaft.

As the article's diagrams note, you should never use u-joints to transmit thrust. They are not designed to do that and will fail quickly if done that way.

Lou's boat has a thrust bearing aft of the u-joints so they don't take thrust. I wouldn't change it.

David

 

[Lou_tribal]

Benefit of this setup that were mentioned were that perfect engine and shaft alignment was not needed anymore and that engine can be mounted on softer engine mount that would allow for better vibration absorption and noise reduction.
There was also a setup that I found funny with only one u joint that was allowing to retract the propeller. It was used by fishermen in Nov Scotia to ground their boat without damaging the prop.

L

 

[RT Firefly]

Greetings,
Mr. L_t. As Mr. dj noted, your set up is quite acceptable. It's been working well for how many years? Leave it alone. If it's not broken, don't fix it until it IS broken...

 

[Lou_tribal]

Greetings,
Mr. L_t. As Mr. dj noted, your set up is quite acceptable. It's been working well for how many years? Leave it alone. If it's not broken, don't fix it until it IS broken...

Indeed my dear Mr RTF and like you mentioned in your previous posts as well as this last one if it was done working fine for 20 years and more I won't change it for sure

L

 

[rochepoint]

I believe that is like the setup Mark has in his Coot.

 

[Nomad Willy]

Lou you may want to check the splines on the U joints. Most of the pitching of the engine will be felt as fore and aft movement that will be allowed by the splines incorpotated in the U joints. Kinda like lubricating an intermediate bearing. You must have a zerk fitting on the outside of the barrel to keep the splines lubed.

But perhaps I missed something and that’s not the case??

 

[Lou_tribal]

Lou you may want to check the splines on the U joints. Most of the pitching of the engine will be felt as fore and aft movement that will be allowed by the splines incorpotated in the U joints. Kinda like lubricating an intermediate bearing. You must have a zerk fitting on the outside of the barrel to keep the splines lubed.

But perhaps I missed something and that’s not the case??

Indeed I have 2 grease fittings per U joint, one at each spline end. So no you did not miss anything [emoji3]

L

 

[chriscritchett]

Unusual perhaps, but quite nice when properly set up. Basically the same as the Aquadrives in many ‘hi-dollar’ boats, just using U-joints instead of CV joints. Also how things are set up on any good-size sportfish or motor yacht with a remote-mounted V-drive gearbox.

Hopefully there are guards around everything to keep your tie out of it while underway, and contain the pieces should anything fail.

 

[Nomad Willy]

critchett and Lou,
I put an AD in my other boat some time ago. I talked extensively w the dealer and they explained that for one kind of motion the CV joint was necessary and I think it was other than the thrust. I understood it at the time but soon after I couldn’t put it together mentally. Also at the time I had already bought the AD so I don’t think they were just trying to sell me. Sure wish I could remember. I was going to do just as you did but I didn’t want the installation to drag on and on. How long and how many hours has yours been on the U joints? RT talks of 20 years but I don’t know where he got that .. I probably just missed it.

As to smoothness how is it? Smooth like magic, considerably smoother, a bit smoother or not much change? My AD was noticeably smoother but not much. There’s so many variables regarding smoothness. If an AD like installation dosn’t address a specific problem there’s not much gain.

 

[AusCan]

Hey Lou - I have no idea why anyone would suggest changing your drive line. It looks well thought out to me. No stress on your gearbox, easy to align, what's not to like about it.

Mine has no CV joints or thrust bearing; just a short straight shaft with a polyeurethane flex coupling and a 8 degree down-angle gearbox. Its not in your book, but probably wouldn't be recommended.

 

[Keysdisease]

As others have pointed out, your driveline is a couple of steps above the typical thrust taking direct drive system found on most boats in the size range of our boats.
Many consider the "thrust bearing" drive line (similar to the mentioned Aqua Drive) to be the second quietest of the yacht drive line configurations, the quietest being an oil bathed shaft system which is quite complex. One step below your installation would be a remote gear taking the thrust the way your thrust bearing does, and the gear would be connected to the engine with a cardan shaft. The noisiest driveline is the simple direct coupled drive line you see most often.
As mentioned, alignment is not an issue, everything aft of the thrust bearing will always stay in alignment because its fixed, and everything forward is connected with U joints. The engine can be mounted on non thrust taking mounts which will reduce vibration into the vessel. Thrust bearings are very robust and reliable, and wear on any cutlass bearings or shaft seals is significantly reduced due to the fixed alignment.
Peeps telling you to change anything just don't understand how it works, this isn't a bandaide fix because of engine placement, but a well designed driveline for a quiet yacht.

 

[Lou_tribal]

critchett and Lou,
I put an AD in my other boat some time ago. I talked extensively w the dealer and they explained that for one kind of motion the CV joint was necessary and I think it was other than the thrust. I understood it at the time but soon after I couldn’t put it together mentally. Also at the time I had already bought the AD so I don’t think they were just trying to sell me. Sure wish I could remember. I was going to do just as you did but I didn’t want the installation to drag on and on. How long and how many hours has yours been on the U joints? RT talks of 20 years but I don’t know where he got that .. I probably just missed it.

As to smoothness how is it? Smooth like magic, considerably smoother, a bit smoother or not much change? My AD was noticeably smoother but not much. There’s so many variables regarding smoothness. If an AD like installation dosn’t address a specific problem there’s not much gain.

My boat has been built in 1994 and U joints are from that time so 24 years old and with around 1600 hours on them.
Cannot say it is smoother or not as I have no reference to compare to.

L

 

[Lou_tribal]

Hey Lou - I have no idea why anyone would suggest changing your drive line. It looks well thought out to me. No stress on your gearbox, easy to align, what's not to like about it.

Mine has no CV joints or thrust bearing; just a short straight shaft with a polyeurethane flex coupling and a 8 degree down-angle gearbox. Its not in your book, but probably wouldn't be recommended.

The picture I posted is showing only setup with U joints, there are others section and schema about setup like yours.
Another thing mentioned is that the setup with U joints is not recommended for powerful engines (like above 350hp) because of the stress put on the U joints. In my case the engine is 75 to 100 hp.

L

 

[FF]

IF you remove or replace the U joints be sure to index them so the new units go back in the same relationship.

 

[jleonard]

IF you remove or replace the U joints be sure to index them so the new units go back in the same relationship.

In engineering terms this is called "phasing" referring to the relative angles of each u joint. The more angle that you have at each u joint the more important phasing becomes. As the shaft rotates the u joint axis force changes in a sine wave. The greater the angle the greater the peaks.
Perfect phasing (when possible) allows those forces to cancel out as the shaft rotates.
I dealt with this for 30 plus years working for a company that designed and manufactured automotive steering intermediate shafts (the "driveline" between the steering column and the rack& pinion). We used to use 10% as a max goal meaning that if the change in torque was more than that in a revolution then a discerning driver would notice.

 

[Island Cessna]

I have a 1967 Willard 36 Sedan with Perkins 4-236 that has a Cardan Shaft. It appears that it was a custom installation from new. The thrust bearing and the shaft seal are contained in a bronze housing mounted on the inner end of the stern tube, bolted to a bulkhead. The shaft seal is 4 rubber lip seals facing outward, and the thrust bearing is a tandem standard ball bearing. There is grease in the bearing cavity, and excess grease goes out under the lip seals into the stern tube. A small pump meters raw water from the heat exchanger discharge into a cavity behind the shaft seals providing cooling to the two cutless bearings.

The engine appears to be in the standard orientation, aligned approximately with the shaft. The difference is that it sits on 4 very large, soft Lord mounts, allowing it to move quite freely and absorbing the engine vibration. No thrust is transmitted to the engine.

I was very leery of this setup when I bought the boat but after one season of use, carefully monitoring bearing temperature and vibration, I have become more comfortable. I give the stern bearing/seal unit a few shots of grease before each day’s run.

There is virtually no vibration in the boat at any speed.

I have a drawing of the seal/thrust bearing assembly dated 1966, made by Friden Inc of San Leandro, CA, with the customer shown as Franz Kaiser, who I believe was the first owner of the boat, hence my belief that it was a custom install from original build.

Has anyone seen a setup like this, and if so have you any comments? Better still, has anyone had any experience with this particular Willard?

Bill

 

[Nomad Willy]

IC,
Looks like the engine needs to be in gear for the pump to work. What’s it pump?

 

[Island Cessna]

IC,
Looks like the engine needs to be in gear for the pump to work. What’s it pump?

It is the metering pump supplying water flow to the cutless bearings in the stern tube. Operating only in gear is appropriate.