Unauthorized V-drive modification

[PeteW]

See if you can spot the modification done by a previous owner to this RV-10.



The folks at Walter Machine company sort of had a cow when they saw it. In fact they deemed my boat unseaworthy as this modification was not authorized by the engineers at Walter Machine Co.

Personally I think this modification was quite clever, well executed and necessary as it prevent the drive train from self destructing in the first 30 seconds of operation. FYI this mod has several hundred hours on it and it runs smoothly. I did not realize what was done until I looked at the picture of Dales V-drive.

FYI you should know that there is second universal at the other end of the drive shaft and the drive shaft down angle is 20 degrees. Way beyond the 15 degrees of the standard V-drive.

Pete   old hull#6

[Jim Cozy]

pete- has the boat been repowered ? sounds like serious engine mis-alignment. there is a universal joint inside the v-drive where the shaft enters to allow for slight mis-alignment of the shaft and the external one at the tranny end to allow slight engine mis-alignment. yours sounds seriously off. where has all the oil come from? I don't doubt that you setup runs smoothly, but it raises many questions that concern me. Jim

[PeteW]

Yes there would be an impossible amount of misalignment without the second u-joint because the angle of the drive shaft from the gearbox to the v-drive is excessive > 20 degrees. The amount of misalignment is 3 degrees with the standard v drive which is 15 degrees.  This misalignment is due to the repower with a Westebeke W58 (69HP) truck motor which is is tall and long compared to a 4.108.  But with this modification the external u-joint establishes the angle of the drive shaft. It runs smooth as silk.   Pete

[PeteW]

OK it looks like you guys flunked the "know your V-drives" exam as nobody could pick out the exact nature of this modification which has Gustave Walter turning over in his grave. But here is the answer that I was hoping at least Dale would have spotted.



So unlike a standard V-drive, this V-drive has a rigid input shaft. It's no longer self aligning which makes that external u-joint absolutely necessary.

I am seriously looking for advice here. As I see it I have 3 options.

1. I could rebuild the v-drive and if the modification looks sound from a mechanical engineering point of view I will leave it and the automotive drive shaft in there. This means I can re-gear with a series 71 velvet drive total cost about $950 for the v-drive kit and the refurbished gearbox. But I will be shunned over at  at Walter Machine where I suspect there is a sign hanging on the wall that says "Das V-drive ist nitch fer gerfingerpoking by der dumbkopfs".

2. I can try to get the drive shaft to lineup by going to a 20 degree angle housing and buy a new rigid adjustable shaft from Walter. This option will still allow for velvet direct drive gearbox. the shaft from Walter and the new angle housing will run and additional $2400 putting this repair at over $3k.

3. I can rebuilt with the 15 degree angle housing, get a new drive shaft and buy a new velvet Drive Liberty series 5000A 1:1 gearbox for $3100. This transmission has offset and a down angle meaning the W58 motor can be raised up level till the output flange is with 3 degrees of the v-drive shaft. At this point the repair to get my v-drive back to Walter Machine specs will have cost $6500. Best solution IMO but naturally the most expensive.

Pete Weisskopf   365Ketch old hull #6

[Dale Tanski]

Pete,

I indeed saw the "different" driveline arrangement.  I beg to differ with the good old boys down at Walter, your boat should not be deemed unseaworthy from the standpoint of the secondary U-joint arrangement, rather the unloved condition of the bilge area and the abandon condition of the mechanical equipment contained with in. 

As an unemployed mechanical engineer, I do not see an problem with the current design of the driveline.  What makes a driveshaft an automotive driveshaft anyway?  Had the owner of that particular drive shaft had the decency to apply a coat of say... John Deere green paint to that shaft, one might conclude it was a "farm" or "agricultural" driveshaft. 

But seriously, I have always had a slight issue with the stock P365 arrangement having only one U-Joint. It is damn rare to find a driveshaft without two U-joints, because with the use of a single joint even the slightest angular misalignment can cause the output shaft to rotate at a variable speed inducing vibration and wear.  One can argue that the alignment between the transmission output and the V-drive input is aligned, can be aligned and will stay aligned.  But that is not true even sitting in the slip.

By rights the driveshaft of a P365 should have been designed with a second U-joint as you have, with the two U-Joints set 90 degrees out of phase from each other. This double joint arrangement would have minimized any misalignment induced vibration, with each joints changing angular velocity canceling out the other.  In short as one U-joint geometry induces a bit of wobble (vibration) the opposite U-joint absorbs it.  In the design of a P365 driveline unless the alignment from gear box to V-drive is dead on perfect, the transmission and V-drive are forced to absorb the induced rotational variations caused by the single universal joint as it changes physical orientation.

So, I would say your installation is much better in minimizing alignment induced vibration than the stock version.  Both fortunately have logged thousands of hours without failure.  I will say this, the angle of the transmission output shaft should be as close to the same angle as the input shaft of the V-drive and in your installation this is not the case.  This opens a whole new ball of wax but in your case it works, so what is the big deal.  I would like to see a containment guard installed on the V-Drive end of the shaft.  If the forward U-Joint parts company for what ever reason in the stock arrangement, the rigid end down by the V-drive will help minimize driveshaft whip until the shaft stops rotating.  If the rear U-joint fails however on a 2 joint set up, that spinning shaft will become the biggest weed whacker you can imagine.

On a car that has rear wheel drive, if the rear joint fails, the shaft falls on to the roadway due to a splined slip shaft at the transmission end designed to absorb changes in length caused by the rear axle moving up and down.  If the front fails however that bad boy can make a hell of a racket and do some serious damage before all motion stops because it is contained by the rear joint.  If you installed a short section of tubing over the V-drive end of the and secured it to the structure of the boat, that would eliminate/minimize the possibility of the free spinning driveshaft from punching a hole in your hull or removing your galley and nav station effortlessly. Pray you are not in the head motoring at 2100rpm's under autopilot control when the shaft breaks loose with no way to get to the engine controls. 

All in all I like your arrangement as is, especially if the input shaft and output shaft were at the same angle which you address in your second proposal.  Reality being what it is, I (substitute the word practical) would go the $950 route. That being said, there is no knowing how the velvet drive will handle any induces vibration from your built in 5 degree misalignment from the first 100 revolutions to the 1,000,000th revolution.  I suspect the Velvet drive is bulletproof enough it will not be an issue.  I would then take the remaining allotted funds and paint the bilge and powder coat all the associated mechanical equipment housed within.

And you thought I missed the 2nd joint...

Dale

[PeteW]

Dale,

Didn't think for a minute that you would not fully comprehend the situation with my drive train. In fact your answer resulted in setting off a light bulb that I would never have wrapped my brain around otherwise.

A quick read of universal joint design on Wikipedia confirms everything you said and helped me to understand the Achilles heel of the Walter designed drive train. Based on what I now understand, I am going to have to concur that the drive train that I have is in a way superior to the stock setup.

I now understand that a single universal joint will produce a variation in angular velocity that increases exponentially (Euler's identity)  as the shaft angle increases and that this variation in velocity produces vibration in a drive train as the propeller actually speeds up and slows down for every 1/2 revolution (pi radian).

Next consider that the dual universal joints ( a double cardan) inside the angle housing of the Walter V-drive, which are connected by a common yoke, is in fact a type of constant velocity joint where the variation in angular velocities cancel (90 degrees out of phase) and thus remain constant.

This leaves the standard walter V-drive with an odd u-joint at the output of the gearbox. This now explains the significance of getting the gearbox flange perpendicular to the drive shaft. (angle to zero) Otherwise you induce vibration.  Difficult because there are no degrees of freedom.

The double cardan in my drive train will cancel the vibration of misalignment provided that the  flange at the v-drive is parallel with the flange at the gearbox regardless of the offset to each other. In this way the angular velocities variation peak is identical for both universal joints and able to cancel to zero.  

So if I go with the 5000A Velvet Drive and increase the 8 degree down angle by tilting the motor only 7 degrees I can be parallel with the V drive which is 15 degrees. Currently the motor is siting at 20 degrees and all the oil collecting over cylinder #4 has resulted in low compression for that piston.

The picture I submitted is a before picture that was taken when I surveyed this boat a few years back and shows what you get when you buy an abandoned boat at an auction. Since then the bilge has been cleaned, painted and a new Grocko bronze strainer installed. The drive train will be yanked next week.

Thanks again for your instruction.  I learned something today.  Pete Weisskopf

[Dale Tanski]

Ditto's on what ever you said about Euler's Pi there Pete. You are way more into this than I ever thought about. Aren't you a sparky type engineer?

You are correct in your assumptions regarding constant velocity joints or dual universals and vibration self correction, but I am not sure anyone has actually created a "real" constant velocity joint realistically speaking.  Whatever the case, two is indeed better than one and you sir have a pair.  The key of course is parallel input and output shafts and if you can correct your alignment issues with the purchase of a 5000 Velvet drive that would be a plus.  If you could flatten your engine eliminating an oil issue all the better. 

Except for the oil issue I am still all about the $950 price tag but must admit if you are going to go, go big.  Are there any good used or rebuilt 5000A's out there?  A good used box for a good used boat? 

It is good to hear your bilge is now a respectable place to hang out but we will all need a current picture to clear your name.  I am also glad you are on the way to solving your dilemma but the price tag still has me uneasy.  Don't forget the breakaway guard in this rebuild of yours. Remember, safety is no accident.

Dale

[PeteW]

I'm envisioning a plywood bulkhead with  hole that the shaft can run though. It can drop an inch and spin in there.

But I am also sensing greater lateral torsional forces on the bearing housing for the now rigid input lay shaft to the V-drive. These forces will cause the V-drive to twist in its mounts which are on a moment arm 10" long. So I see the need for a pair of struts going to the hull port and starboard from the nose of the V-drive to transmit these forces to the hull directly.

Finding a used 5000a velvet drive that's 1:1 seems unlikely. The 71C may be too larger to clear my hull so it may not even be an option for me. But I still have a perfectly functional Paragon that if it ever fails in foreign port will have no known replacement. An I have yet to see a clutch kit for an SA0.

A sailor to the arctic circle described his preparation as having tools and parts on board to repair anything that could fail on his ship. A friend of mine did the Baha Haha  and burnt out his Hurth in Cabo. No spares, no tools and no mechanical skills. 3 weeks at the mercy of the local mechanics. No position I ever want to be in.

Pete

[PeteW]

Pulled the v-drive, shaft and Paragon. Nothing looked good. Unauthorized modification to v-drive was bogus. Bearings were seized and the drive shaft was spun. Walter Machine was right about that.  Paragon spline was 1/2 shredded. Damper plate can be used as a rattle. RV-10 has 10 degrees of backlash. Will need to blueprint the gears to see how bad the wear is. It's probably scrap. May put an RV-26 in there. The W58 torque has torn this drive train up pretty badly. Its going to get expensive. Plan 3 is looking like the only way to go.

Pete

[Jim S]

Out of curiosity, why was a 58hp engine installed?  It does seem to be overpowering almost by a factor of 2.

[PeteW]

Jim,
I don't know were you sail but can tell you that west coast sailing when going north is an uphill climb considering the unfavorable wind and current all year round. So when talking about engines and drive trains it is critical to use only the 100% duty cycle or continuous ratings.  Also for continuous motor cruising a lower rpm in the 1500 to 2000 rpm is desirable. No one wants to be going flat out 24 hours a day under motor. You are going to break something.

The Westerbeke 4-107 continuous rating at 1500 rpm is 17 hp  and 25 Hp at 2000 RPM. Motoring against wind and current I would consider this to be a little anemic. By comparison the W58 comes in at 30 hp at 1500 rpm and 38 HP at 2000 rpm continuous.  Most 107/108 owners think they have a 40 hp motor. Mechanics know its a stretch to even call it a 30 hp engine.

Essentially the W58 continuous HP ratings are similar to the 4-107's 1 hour rating with 20% margin or additional HP that I use to spin a slightly more aggressive prop at a lower rpm.

Can't say how or why that engine ended up in my boat but its been a very popular motor that's still in use today in pickup trucks, fork lifts  and welders all over the world.

Pete

[Dale Tanski]

Pete,

Seeing as the transmission, V-drive and driveshaft are spent, how about this.  Mount a hydraulic pump directly to your engine bell housing and a hydraulic motor direct coupled under the floor boards on your prop shaft.  You can probably mount the hyd. motor to your existing V-drive mounts. You could even flatten out the engine as much as space will allow to eliminate your engine oil problem because hoses bend any way you want.  You could even spin the direction of the engine 180 degrees so it would be easier to service the drive belts, water pump end.

To change prop direction you just shift a spool valve driven off of your existing transmission shift linkage.  You could set the pressure relief so it would save everything if you wrapped a lobster pot.  For the most part you would pick the optimum engine RPM for fuel burn and adjust the hydraulic flow to set boat speed.

Agriculture hydraulics would be easy to get your hand on, rugged and reasonably priced.  High speed rotating hydraulic drives are every where on today's agricultural equipment.  Used stuff should be everywhere.  If you went with standard stuff, components would be available anywhere in the world.  I am willing to bet that finding a hydraulic agriculture tech in Timbuktu would be much easier than a marine mechanic.  You would need a heat exchanger to control the oil temperature but cooling capacity is unlimited on a boat.  You could actually install an air over oil heat exchanger in the cooling loop remotely (hoses again) and heat the boat.  Return oil pressure would be next to nothing so those exchangers (one per cabin perhaps) would not be expensive.  Maintenance would be minimized to changing a hydraulic filter. I would use hydraulic tubing everywhere and a short section of hose for vibration isolation and movement requirements. Tubing is actually cheaper.

Just think, once you have the hydraulic drive set up you could always tap into it for a hydraulic windlass. You could be charging your batteries while pulling up the hook.  Or.. think about the dingy davits you could have retrieving with the touch of a button. 

I know this is over the rim of the box, but if you think it through it may even be a cheaper alternative with many advantages. I would be more than willing to do/help with the engineering and drawings on this one if you decide it is something you want to do. There is probably less design work and fewer custom parts than the track you are heading down with the velvet drive set up.  I actually can not think of a single downside on this.  Can anybody else? 

Dale

[SVJourney]

Hmmm... Intriguing idea.  Are you thinking a variable displacement pump?  Would he need an unloader valve to start the engine or operate in neutral?  I would think that there would have to be some method of de-linking the engine from the pump.

The splining of the pump to engine would need some custom machining, as would the mount plate. 

Wayne

[S/V Deo Volente]

I saw this tried once, but in this particular case it didn't work well. I really felt sorry for the guy. I don't know the specs, other than it was about a 33 foot center console with a Perkins 4-108. He ended up hanging an outboard on it after traveling from Thunder Bay Ontario to the Soo. I toured the boat before he left and never heard exactly what his problem was. I only heard from his friends that he couldn't get enough power to go more than 3 knots. I don't know if it just wasn't engineered well or what, but he spent a lot of time and money before he gave up on it.

[Dale Tanski]

A variable displacement pump is one way of doing it.  An unloader valve would not be necessary as the displacement could be adjusted to zero output. 

The use of a standard pump and a relief valve will accomplish the same results.  Just as with any hydraulically controlled unit they can be easily started because the pump displacement is wastegated back to the oil reservoir.

The good news is if everyone stopped doing because of someone else's failure, nothing would exist.  A hydraulic drive would need to be designed correctly to work correctly.  Because hydraulic pumps are positive displacement and hydraulic oil can not be compressed, the exact outcome can be calculated for every amount of work energy inputed. 

I am sure if we worked the calculations on the 33 footer mentioned we could determine the exact cause of the limiting hull speed factor.  The laws of physics can not be negotiated unless you are the government and then all bets are off.  They seem to think just because they say a car will need to achieve 50 mpg and make it a law, it will be so.  Again except for the government, you can't get something for nothing and every frictional loss and energy conversion loss can be identified, calculated and compensated for.

If we look at lawn cutting equipment over the past 15 years as an example, very few were hydraulically driven.  Most all applications were belts and gears.  Today the vehicle and the blades are hydraulically driven and the operation of the overall machine is superior to anything from the past.

How many boats were propelled by electric power 10 years ago? Today that has become more and more common place.  Even SeaRay has an electric boat and Correct Craft a top end builder of ski boats, has an all electric ski boat. There have been production sailboats powered by hydraulic drives in the past. One is the F & C 44. Here the Perkins 4-107 was mounted in line with the keel and also across the keel just like a front wheel drive automobile saving tons of space.

Dale