LU technicals?

[Techno]

I started a different thread because I thought of a way to make an LU and possibly do this as a business when my job goes Kapoot. SO the start of the research....

Does the nose matter whether its shaped like a bullet or is it better to be sharp verticaly seen from the front?

Does having the nose project out from the vertical portion of the case have any advantages or is the ratio the only important thing hear?
What aspect ratio am I shooting for?

Smallest set of gears possible-which leads to smallest diameter leading to how small can the bearings be?
Smallest gears both as the standard system and a multiple shaft system.

What would be an ideal gear ratio and the 2nd ratio? lower or higher. This might be 2 speed. Although that would be the 2nd phase- replacing the midsection.

Any use of having the exhaust go through the prop? Or just dump it out above? Can the bearing carrier be eliminated if no exhaust?

Would oil pumped bearings/ gears offer any advantage?

Where would a nice place for an oil fill be located?

Would a SS unit be better than an aluminum one? I'm thinking the skeg could be made much stronger, possibly welded if broken and should be able to be bent/beat on like a prop for torque tuning. Being stronger might be thinner so lessen the weight problem.
What kind of stress does it need to take? I would stick it in a press and break it off for testing, among other things.

Low water intakes- where is the best location? At the leading edge of the skeg? Its base near the torpedo? Nose? Where?

Anti-ventilation plate- is it needed? Should it be a bolted on part for prop diameter customisation and other reasons?

[Dave S]

TTT:D Lets hear it from the PROs:confused:

[crazy horse]

The Mercriuiser #6 drive is a dry sump system with a small oil pump in the front of the bullit that pumps oil up to the spur gears and then back down to the shaft. I think they get $35000.00 each:rolleyes: I have a cutaway of it around here someplace , If ya want me to post it let me know I'll start digging though magazines. I've always wanted to set up a lubrication system with a small pump for speedmaster gearcases.

[msm]

I'd like to see that post. I've always wondered what a cutaway of the dry-sump six-drive would look like. Back in a late '80's Powerboat Magazine they had a cutaway picture of the five drive that I wish I would have saved.

[Techno]

DRY sump? I'm still wondering if it even needs to be pressure lubed.
Can't hurt but trying to keep it simple.

Don't dry sumps suck HP?

[Markus]

A stainless steel skeg is definitely a good thing. There is a reason why we all run stainless steel props. Didn't Allison patent mounting the skeg on the side of the bullet rather than on the bottom, by the way?

As to the shape of the bullet, it seems like Bob's nose cone on a non-racing lower unit is the reference point. I would start from there.

[crazy horse]

I'll dig it up and get it scanned . I really don't think you would have to have pressure lube , I thought if you could run lines to both the drain and the vent on a ssm then run it to a small tank and set up a small oil pump and filter like they use to lube the powerhead. If your just moving the oil around then if the pump failed your gearcase would still live though it. The fill screw is just below the cav. plate on a ssm so I think the feed line for the case would get pounded pretty good. If you could setup a standard gearcase with oil lines above the cav. plate you could have a small tank that would hold xtra oil. I'm still working on setting up a lube system for my cases , Right now all I have is a Mercruiser reserve tank on my XS but I havn't given up on one with a pump yet:D . This is a shot of my reserve setup on my inline.

[time warp]

The number 6 drives use 2 vertical shafts and have pinions on both of them so that the gears can be smaller and still be strong enough, if you could put the transmission(forward and reverse)in the tower housing you could run 2 vertical shafts down into your lower, that way you could make the bullet smaller.

Yes the dry sump pump robs horse power but having the gears spinning submerged in oil robs much more, Wiesmann was the first to dry sump the #6's there is probably more info at
http://www.weismann.net/
The dry sumps are both faster and more dependable.

Good luck on your gearcases.
Caleb

[Techno]

I'm not working on a standard LU. I'm making my own from scratch. Or thats the idea. I can do whatever is needed since its at the design level right now. If there was an oil pump it would be driven right off the prop shaft probably. In the nose.

Still thinking the place to get the cooling water is in the skeg. Imagine jacking up till the prop loses bite rather than cooling? More for an area that doesn't disturb the flow of water to the prop though. Not sure thats the place.

[time warp]

I understood that you are starting with a clean sheet of paper(block of aluminum?) here's a quote from Wiesmanns site
"Our Drysump Drives have both a scavenge and pressure pump inside the drive, and oil is pumped through the transom to a sump tank stored and de-airiated in the boat. Oil is then pumped back into the drive
and sprayed into all bearings and gear sets"
Are you going to make them shiftable or will they be in gear all the time?
I think water pickups on the hull would be the way to go, especially if your tranny was in the tower housing, your water pump could be on top of the tranny(might have a problem getting it to prime though?)and you wouldn't have any water flowing thru the drive.

Caleb

[Markus]

I agree with that. A transom-mounted water pick-up takes care of the problem of losing water pressure before losing prop bite.

[crazy horse]

Here's that cutaway of a dry sump #6.

[crazy horse]

This is the other photo that was with the write up . Looks like fun:D .

[Techno]

Actually that helped out more than I thought.
The gears deal will probably be a 2nd generation thing. Try and do the LU first with an add on above it. Whether it takes the place of the mid or slips into don't know.

Having the pickups on the LU seems to make it a more bolt on application, less pain.

I'm thinking it will have to shift since not everyone is going to have electric drives like me. ;)

[msm]

I always liked the looks of that drive and now I know more about the internals. Thanks again. :)