Pulse Drive applications and installations

[rustnrot]

HallJ, I am summarizing since I need some data for my own Pulse Drive surface drive project...while I realize none of your data may be pertinent to my project, surface drive data is virtually non-existant so I will take anything I can get....

your engine, tree fity, 364 hp at 5800 rpm
gear reduction, 1.56
prop pitch 20" 3 blade Rolla non-cleaver
prop diameter?
does prop allow 5800 rpm to be reached at WOT?
approx boat weight?

thanks.

[Boatless]

OMG:confused: There is no data that will transfer from an Arneson to a PSI.

Schoell made his own set of problems and I hope that you do not let the PSI give you a bad cogitation of a surface drive.

The PSI will need a totally different propeller as it has a different shaft than any other drive out there.

Does your PSI have a single rudder or twin?

If it has twins, it will difficult to steer to the right as the rudders block the water

[rustnrot]

I realize the shaft is different for the Pulse Drive to fit proprietary propeller hubs, but pitch is pitch and diameter is diameter. Also it would not be hard to change the shaft to any splinage or taper you would want to fit a competitor propeller to.

Regarding the rudders, I have ridden in Harry's 21? foot boat and it appears to steer just fine with the twin rudders.....the same unit I have.

Anyway, I will certainly find out as I am using the Pulse Drive in my Chris Craft XK18.

It sounds like you have some experience with the Pulse Drive, if so let's hear it.

[Boatless]

I realize the shaft is different for the Pulse Drive to fit proprietary propeller hubs, but pitch is pitch and diameter is diameter. Also it would not be hard to change the shaft to any splinage or taper you would want to fit a competitor propeller to.
Regarding the rudders, I have ridden in Harry's 21? foot boat and it appears to steer just fine with the twin rudders.....the same unit I have.
Anyway, I will certainly find out as I am using the Pulse Drive in my Chris Craft XK18.
It sounds like you have some experience with the Pulse Drive, if so let's hear it.

The PSI drive has had many problems. While they are at the surface, one surface drive is not another.

Harry puts them on boats he designs and while they might work on a bottom he designed around them or vice versa, they do not work on much of anything else.

Best of luck..

[rustnrot]

The PSI drive has had many problems. While they are at the surface, one surface drive is not another.
Harry puts them on boats he designs and while they might work on a bottom he designed around them or vice versa, they do not work on much of anything else.
Best of luck..

Ok, how about listing at least two problems it has and one example of it not working in a partcular hull. I'd love to have even more examples but so far all I am hearing is empty rhetoric.

[Boatless]

Ok, how about listing at least two problems it has and one example of it not working in a partcular hull. I'd love to have even more examples but so far all I am hearing is empty rhetoric.

1. It has a 10 degree down angle which will push your bow over and the boat will want to bow steer

2. You have to source your propellers from Harry Shoell, who by the way is not a propeller designer nor manufacturer. So Guess what your are going to get?

3. The unit thrurst the universal joint in the assembly. Universal joints are not designed to accept thrust. Life span?

4. Your engine will have to be mated to a gearbox internally, which will eat HP, limit your RPM, rob you of engine room space. What that really means in LAYMAN terms is your CG will be farther forward than it will be with an Alpha or Bravo. Hint, more bow steering problems.

5. Weight:, the unit is larger and havier than the Alpha/Bravo/OMC/Volvo that was on the boat.

6. They have not worked suffessfully on anything that Harry Schoell did not design the bottom around, and then it was subject.


But, you spent your $$ and I am sure you will be happy.

Don't shoot the messanger, the thruth can hurt sometimes.

Maybe you should list your reasons for wanting to use the PSI over the I/O?

[VetteLT193]

1. It has a 10 degree down angle which will push your bow over and the boat will want to bow steer
2. You have to source your propellers from Harry Shoell, who by the way is not a propeller designer nor manufacturer. So Guess what your are going to get?
3. The unit thrurst the universal joint in the assembly. Universal joints are not designed to accept thrust. Life span?
4. Your engine will have to be mated to a gearbox internally, which will eat HP, limit your RPM, rob you of engine room space. What that really means in LAYMAN terms is your CG will be farther forward than it will be with an Alpha or Bravo. Hint, more bow steering problems.
5. Weight:, the unit is larger and havier than the Alpha/Bravo/OMC/Volvo that was on the boat.
6. They have not worked suffessfully on anything that Harry Schoell did not design the bottom around, and then it was subject.
But, you spent your $$ and I am sure you will be happy.
Don't shoot the messanger, the thruth can hurt sometimes.
Maybe you should list your reasons for wanting to use the PSI over the I/O?

Do you have any sources for your information?

#5 for example, is hard numbers. can you provide the hard numbers? seems to me it would be lighter than a bravo drive. (much less complex)

#4 also makes no sense to me. There are no bends/angles on the pulse setup like in a typical stern drive, so the HP losses should be less, not more.

#2 and #3 look like pure speculation, do you have any hard facts?

#6 is something I've never heard nor read, do you have any hard facts?

#1 also makes no sense to me: it's surface piercing, so if the bow gets pushed that 'far over' the prop would come out of the water entirely. Any hard facts, links, etc.?

[rustnrot]

1. It has a 10 degree down angle which will push your bow over and the boat will want to bow steer
2. You have to source your propellers from Harry Shoell, who by the way is not a propeller designer nor manufacturer. So Guess what your are going to get?
3. The unit thrurst the universal joint in the assembly. Universal joints are not designed to accept thrust. Life span?
4. Your engine will have to be mated to a gearbox internally, which will eat HP, limit your RPM, rob you of engine room space. What that really means in LAYMAN terms is your CG will be farther forward than it will be with an Alpha or Bravo. Hint, more bow steering problems.
5. Weight:, the unit is larger and havier than the Alpha/Bravo/OMC/Volvo that was on the boat.
6. They have not worked suffessfully on anything that Harry Schoell did not design the bottom around, and then it was subject.
But, you spent your $$ and I am sure you will be happy.
Don't shoot the messanger, the thruth can hurt sometimes.
Maybe you should list your reasons for wanting to use the PSI over the I/O?

Time for some Facts:

1. The prop shaft is at a 2-3 degree angle, the transmission uses an eight degree down angle as it is gear reduction type. The engine actually tilts slightly forward to compensate. The prop angle is trimmable about +- 3 degrees.

2. The shaft as received is machined to fit only props spec'd by Harry (hub difference), however changing the shaft or remachining it to accept a competitor's prop would not be difficult. If shaft replacement is desired, it is simply an approximate 3 foot long 1.25" stainless shaft, blunt with key on one end and your choice on the other. (I find it interesting that this is the only "fact" you got correct -- after I had already mentioned above in an earlier post).

3. I too was concerned about this. If you think and calculate you will find that the axial loading of the u-joint is an order of magnitude less than the radial loading. Whether loaded axially along the shaft or radially around the joint, the needles in the u-joint see the same type of force, i.e. pressing the needles against the u-joint spindles. Furthermore, the u-joint in Harry's boat is 10 years or more old and is still going strong.

4. The engine is connected to a gear reduction transmission. I bet it is a least as efficient (and certainly more compact) than a combination 1:1 velvet drive with separate gear reduction inside the Arneson unit, for example. Or as VetteLT193 suggests, at least as efficient as an out-drive. My engine (aluminum Toyota 300 hp 6000 rpm now sits nearly 1 FOOT REARWARD of the original 454 that powered a JET drive pump. And the engine is not rpm limited by the transmission. Hurth now supplies these transmissions with high-speed pumps to take at least 6500 rpms, and according to ZF, they have reports of an electric boat manufacturer running them near 9000 rpm.

5. I have never owned an out-drive boat in my life, this one included. The Chris Craft XK18 was manufactured originally as a jet drive. As far as weight, the pulse drive unit I am using is about 120 lbs. Add to that the 85 pounds or so for the transmission and you have over 200 lbs. of drive. Compare this to an outdrive yourself as I have never owned one.

6. I can provide a specific example of where this worked on a non-Harry hull, the pulse drive was installed on a Kenner center console and performed fine. I can provide references. So far you have not provided one specific example of where this drive has failed to perform on a specific hull...and don't forget to supply references.

7. I'll add a concern to your list--I'm surprised you didn't mention it. Since this is a u-joint and not a constant-velocity joint, the tips of the propeller will change as it rotates, higher u-joint angles resulting in more speed change. However, with a plus-minus 3 degree tilt, the speed change is negligible and furthermore since the prop operates in a fluid, I could not detect any problems in the operation of the boat.

8. Since I am replacing a jet drive with the pulse drive and not an outdrive, I will leave those comparisons with those that have the experience with that conversion. While you may be correct, Boatless, that this project may fail, the truth never hurts me (nor would I imagine "thruth" hurt me either as you say), what does bother me however, is generalized statements with no references and in some statements you have made, completely untrue. I also can tell you that if this project fails I will not mope around and be unhappy about it. I will have furthered my knowledge of the subject and that is the main reason for doing this project.

[justleft]

Humm, both sides are saying "show me the facts" but neither has provided
any references.....

[pmreed]

I think we can depend on Tom's physical description of the drive parts since he's got one in hand. That's a good enough reference for me. As to the performance issues, Tom's hanging it all out by actually building the darn thing!! If it works, we'll all know; if it doesn't, we'll know that too. Kudos to him for that.
My guess...with a little finetuning it'll work just fine:).

Phil

[rustnrot]

Hopefully, I will have it done by March 2008. My goal is to have it at the www.classicraceboatassoc.com in Tavares, FL show. This past year (2007) the event was a week prior to the Mt. Dora Antique Boat Show, I am not sure about next years dates, but it is within a week or two of Dora, check the website to be sure.

This is a new "club" and new venue and was alot of fun this past year. My only participation was dry-land display of the Gar Wood speedster replica I built (the one with the Mazda rotary engine...alot of naysayers on that project also).

Since then, Classic Raceboat Association has added a "general runabout" (or something like that) category that is eligible for basically any "cool" boat. Donzi's are absolutely eligible. What it amounts to is running your boat in exhibition-style racing around their course on Lake Dora. You must have a kill switch, lifejacket with leg straps (Lifeline brand not necessary), and a shaft collar. I think also a helmet.

I had more fun at this show with all the vintage race boats, (flatties, hydros, outboards) than I did at the Mt. Dora show. So much fun I may not hang around for the Mt. Dora show this next year like I did in '07.

[MOP]

Tom I was glad you hung around Dora or we may not have run into each other for another 2-3 years, good luck with the project they are work/fun!

Phil

[gcarter]

Surface drives have been around for at least 80 years and they will always work. Some are more successful than others though.
As far as I can tell surface drives were invented by Albert Hickman in the mid '20's as part of his whole "Sea Sled" package. In that instance the two propellor shafts protruded through the transom just above the waterline in the outboard, deep, sections of the Sea Sled. Their position was completely unmovable. It used outboard rudders that were almost useless going forward and worse than useless in reverse.
It was a clear breakthrough when Arneson developed his design. It seemed to solve all the problems associated with them.
I can think of at least four drives currently in production, but there's probably a lot more.
1) Arneson
2) Pulse drive
3) Buzzi's drive that has been very successful racing in Europe.
4) The drive on the Donzi currently wiping up in Europe. It has a very looooong high aspect ratio rudder located on centerline. I don't think either of the European drives have much, if any movement and are very specialized.
I believe, as I've already stated, that they'll all work, however some, like the Arneson, are much more useful in all around boating than some of the drives developed for more specialized applications. If I were in the market for one, I would like one that had a good selection of props, that would maneuver as much like an outdrive as possible, and that had a good selection of used parts available.

[gcarter]

Concerns about U-joint loading shouldn't be an issue. Hasn't Corvette used the half shafts as active suspension components for years?

[BigGrizzly]

Tom I am with you. If everyone was scared of failing Donzi would never have been built. People told me "you can't close cooling a supercharged motor and you can't close cool a 698 HP engine" So I did it anyway, it worked fine. I also run my engine with a thermostat and have 9.5 compression before the blower. How many people do this? Now everyone is doing it. I looked very hard at the pulse drive years ago and I felt is was a good idea and well done. Yes Harry is not a prop designer, but he isn't stupid either. Do you think Hydromotive designed their props on a clean sheet of paper ? I think not. Don't let any body discourage you! As for facts, there aren't any until you complete the project. Question " how many pulse drives have failed for those reasons listed above? Frankly I will be waiting for your project completion. I will trade you a ride in mine Criterion or Corsican for a ride in yours. The world needs dreamers and risk takers. Years ago people said Honda couldn't compete in the auto industry. Look what has happened.
there is nothing to it but to do it!