1962 Seacraft

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bootlegger
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Joined: 09 Mar 2009, 20:18

Re: 1962 Seacraft

Postby bootlegger » 10 Mar 2014, 08:40

Woodray i know you are a competent mechanic and i know your right about the angle of the engine and the crank splashing in the oil. Speedboating is hard on engines at the best of times. The problem is this set up is the worst solution of a marine problem. Back in the day only the rich guys had dry sumping. This setup was for the majority of hulls and generally it does the job.
Ive always thought about harmonics graham. I have lunched a few engines in my hydro atomic.
The engine sits level in the hull with a single uni joint bolted to the back of the crank. There is a spline on the other end of the uni into the zdrive box which is angled to the prop shaft.
All the failures have been big end bearings on tye second journal.
Ive had several different engines holden and chev. Im dry sumped now. All died the same way.
Ive been told on a chev 5800rpm is to be avoided. Over or under they are safe from harmonics.
If my problem is in my drive line what could I change to fix it? Bolt the gearbox directly to the block and get rid of the uni?

Damo
Posts: 177
Joined: 01 Nov 2012, 11:01

Re: 1962 Seacraft

Postby Damo » 10 Mar 2014, 10:51

No worries Craig, probably the best solution to your issue, I am also tossing up running an accumulator as added backup as I still have reservations about keeping my pickup in oil and I would rather not lunch a new motor to find out. Good Luck mate!

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bootlegger
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Re: 1962 Seacraft

Postby bootlegger » 10 Mar 2014, 17:45

There is a guy on ozboatracers forum. He has an accumulator for sale for $200.

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rumbles
Posts: 48
Joined: 29 Nov 2013, 12:59

Re: 1962 Seacraft

Postby rumbles » 10 Mar 2014, 18:54

I am glad this oil issue has been raised, and have a few questions for the more learned..
I have a 308 mid mount dog clutch ( driving from the front)
my oil pressure reduces as the motor heats up, and I was suspicious of foaming.
I cant see the sump at the moment as the motor is out and away being fiddled with, but I will check when I get it back in a couple of days. as I recall it has had the bottom of the original sump cut out and a deeper flat bottom tank the full size of the whole sump grafted on. it is a little deeper at the rear and quite a bit deeper at the front as the bottom is flat and parallel with the bottom of the boat ( in other words as big as you could possibly make it). the oil pickup is at the front but I will return to that in a moment.
my questions are: how much oil do you really need? and at any given moment when the engine is running, how much oil is "in circuit"
it would appear to me that if clearance was available surely a pickup at the rear would be better than at the front given the angle of the boat under acceleration and at low cruising speeds.
how far under the surface of whatever oil is not in circuit would the pickup need to be to stop it sucking air?
the reason I am asking is in an effort to keep the crank out of the oil during operation ( not necessarily when the motor is at rest obviously as the oil is drained back into the sump)
you have no doubt figured out that I am not a mechanic, and apologise for what may be the silliest question of the month :)

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WoodRay
Posts: 531
Joined: 12 Feb 2014, 15:19

Re: 1962 Seacraft

Postby WoodRay » 10 Mar 2014, 19:07

bootlegger wrote:Woodray i know you are a competent mechanic and i know your right about the angle of the engine and the crank splashing in the oil. Speedboating is hard on engines at the best of times. The problem is this set up is the worst solution of a marine problem. Back in the day only the rich guys had dry sumping. This setup was for the majority of hulls and generally it does the job.
Ive always thought about harmonics graham. I have lunched a few engines in my hydro atomic.
The engine sits level in the hull with a single uni joint bolted to the back of the crank. There is a spline on the other end of the uni into the zdrive box which is angled to the prop shaft.
All the failures have been big end bearings on tye second journal.
Ive had several different engines holden and chev. Im dry sumped now. All died the same way.
Ive been told on a chev 5800rpm is to be avoided. Over or under they are safe from harmonics.
If my problem is in my drive line what could I change to fix it? Bolt the gearbox directly to the block and get rid of the uni?


Dave I have re read my earlier reply and I have to apologise as it looks to read that I'm having a crack at you. I know I can come across blunt and direct, too many years in the Army and as well being a grumpy old fart these days. I struggle to communicate this way and like most I'd rather do it face to face, as well as being hands on working rather than spending time on computers chasing info. All this is no excuse though. Once again I apologise and I'd like to thank you for taking the time respond to my queries on this post and many others I have on other forums. Your help is greatly appreciated as is with others. Thanks again.

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WoodRay
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Re: 1962 Seacraft

Postby WoodRay » 10 Mar 2014, 19:31

Wildwoody1 wrote:The adjustment to the thrust setup is done via the flanges ability to slide forward and backward on the snout of the crank within the drive housing. If there is not sufficient movement the the harmonic vibrations are transmitted in the end of the crank which in turn forces the oil out of the bearing space. The problem is most often caused by attaching the flange to the crank with too short a bolt or packing the bolt with washers to achieve a tight fit. Some drives overcome this by fitting a slip yoke in the drive line attached to universal joints.
It does not matter what you do to a sump if the thrust adjustments are not correct the oil will be squeezed out and failure will occur. It also does not matter which end of a crank the drive is taken from the end results are the same , predictable and expensive.

Wildwoody1


Graham thanks for the info. I'm keen to understand more about harmonics from the prop. I struggling to understand what end float and subsequent harmonic influence the prop would have on the crank or more to the point how it would. I can see how the lack of harmonic balancer and the added length/weight of drive shaft on the snout of the crank could upset natural torsional vibrations in the crank, but cannot see how adjustment of the thrust would have any effect other than controlling crank end float and main bearing thrust wear. As torsional vibration is relative to twisting forces applied to the crank, how does end float effect it? The two main vibrations in a crank are Torsional Vibration (Natural Frequency) and Harmonic (sine wave) Torque Curves. The natural frequency is more related to the twisting applied to the crank and its length with the weight of a flywheel at one end and the ability of the crank to "spring'' back. Harmonic torque curves are related to cylinder firing pulses applied to the crank and their frequency. Again I can see how the weight/length of the drive shaft and prop would affect these but I'm unsure how end float does. Re oil being squeezed out could you elaborate on this and how/where it happens? Do you mean the thrust bearing assembly at the timing gear end or the main bearing thrusts? Thanks for your time and patience on this one. Cheers.

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WoodRay
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Joined: 12 Feb 2014, 15:19

Re: 1962 Seacraft

Postby WoodRay » 10 Mar 2014, 19:34

Damo wrote:No worries Craig, probably the best solution to your issue, I am also tossing up running an accumulator as added backup as I still have reservations about keeping my pickup in oil and I would rather not lunch a new motor to find out. Good Luck mate!


The accumulator sounds like a great idea. We run them on our fire pumps at work as pre start lube for turbo's (solenoid controlled dump) and another for cool down lube for turbo's after hot shutdowns (no rundown timers).

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WoodRay
Posts: 531
Joined: 12 Feb 2014, 15:19

Re: 1962 Seacraft

Postby WoodRay » 10 Mar 2014, 19:45

rumbles wrote:I am glad this oil issue has been raised, and have a few questions for the more learned..
I have a 308 mid mount dog clutch ( driving from the front)
my oil pressure reduces as the motor heats up, and I was suspicious of foaming.
I cant see the sump at the moment as the motor is out and away being fiddled with, but I will check when I get it back in a couple of days. as I recall it has had the bottom of the original sump cut out and a deeper flat bottom tank the full size of the whole sump grafted on. it is a little deeper at the rear and quite a bit deeper at the front as the bottom is flat and parallel with the bottom of the boat ( in other words as big as you could possibly make it). the oil pickup is at the front but I will return to that in a moment.
my questions are: how much oil do you really need? and at any given moment when the engine is running, how much oil is "in circuit"
it would appear to me that if clearance was available surely a pickup at the rear would be better than at the front given the angle of the boat under acceleration and at low cruising speeds.
how far under the surface of whatever oil is not in circuit would the pickup need to be to stop it sucking air?
the reason I am asking is in an effort to keep the crank out of the oil during operation ( not necessarily when the motor is at rest obviously as the oil is drained back into the sump)
you have no doubt figured out that I am not a mechanic, and apologise for what may be the silliest question of the month :)


Hi Rumbles, oil pressure will drop as it gets hotter but is it within in spec for your engine set up? Also how hot is the oil getting? You may need to check oil temperature and whether you need some oil cooling mods. Do you have any pictures of the sump internals? I'd be concerned with oil surge if it holds heaps of oil without decent baffles/trap doors etc. I'd have to agree with having a rear pick up as the boat would spend more time under acceleration and slightly nose up although you'd have to consider forward surge when backing of the gas.

screwit
Posts: 1016
Joined: 09 Apr 2010, 21:29
Location: Stratford vic

Re: 1962 Seacraft

Postby screwit » 10 Mar 2014, 20:21

You guy out there that are going through this oil problem , cooling with water pipe though the sump will help the oil pressure when running warm , cars have the air to do this , If you do not dry sump- do not make the sump wider like in hot cars to keep the oil lower in the sump .
This will only stave the engine when banking and end in tears.
Ross

The Spook
Posts: 198
Joined: 20 Jun 2009, 15:49

Re: 1962 Seacraft

Postby The Spook » 11 Mar 2014, 11:40

Bootlegger

I was just reading your post regarding the number of engines that you have lunched in Atomic.

You're right that there are two ways to set up your drive train, one is with the engine connected to the gearbox via a plate and mounting spacers, with the gearbox mounted on the rear of the plate. Then to have the spline drive of the gearbox captive inside an equivalent spline drive specifically made to mount on the end of the crankshaft. This system sets up the engine and gearbox as a single unit with the complete unit at the same angle as the prop-shaft. Graham Howard does a very good example of this system. The second is to mount the engine and gearbox separately and use a universal/jack-shaft setup.

The system that Graham uses is very good, however it requires very exact machining to ensure that the two splines do not have any run-out in them. When I ran that system in my old hydro it had a small run-out and it caused a minor vibration and wear which I was never able to figure out until after I had sold it. It turns out the eccentricity was in the piece of spline that we used to make the crankshaft drive unit with, the spline in the piece of spline drive was not central to the outside diameter of the material. When we discovered this the solution was pretty simple and it means setting up and machining the O/D of the piece of spline drive so that it is concentric with the spline, then making your crankshaft drive unit. I might add that Graham did not make the setup on my old hydro and I am not inferring in any way that Graham was in any way responsible for its eccentricity.

The second method is to use a universal style shaft or jack-shaft, which is what I have used in my new hydro. The information that I was able to get during the setup in my new "The Spook" was that when you use a universal style jack-shaft you need to use two universals in the shaft. Apparently one doesn't allow for any misalignment of the gearbox input shaft and engine, this stress is then transferred into the engine. In your case you would probably need to build a new setup with two universals back to back, which allows the uni's to work out any misalignment. The shaft in my new hydro is 173mm long from center to center of the two universals, the prop-shaft angle is 6.75 degrees and the engine angle in the boat is 3.5 degrees with approximately half of the angle difference taken up in each uni. Even with a jack-shaft setup you may need to re position the engine in relation to the gearbox to get the universals to work correctly.

The other issue is that the engine should be at about the same angle sitting in the boat as it would in a car. This apparently helps with oil flow to the rear of the sump as well as coolant flow through the cylinder heads. In some V8 engines sitting the engine flat can cause air spaces inside the heads, which in turn can cause hot spots in the engine. I use a wet sump with a ten liter capacity and I have the engine sitting in the boat in the same direction as it would in a car ie the front of the engine points to the front of the boat. This means that the engine sits a bit higher in the boat, unfortunately, but it works.

Spook


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