Small Engine 6.5 Tilting 5

[paskee]

Hi Guys.. I need advice.

I have purchase a Briggs and Stratton Vanguard 6.5HP Horizontal Engine (w/ splash lubrication system / motorsports rod dipper design).. I want to tilt it to power a small boat's propeller... the manufacturer does not recommend it ( but I've seen similar small engines being tilted in operation...

what angle from horizontal do you think I can get away with w/o causing engine failure/long term maintenance issues?


It will be operated daily, 10-12 hrs

 

[MikeHalloran]

Do you think we know better than Briggs & Stratton?

Do you think B&S will warrant the engine if _we_ say it's okay to run it in positions they don't support?



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

And how could we possibly know without studying the oil control system in this engine.

Regards
Pat
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[malbeare]

maybe you could overcome any oil starvation by overfilling it a bit.

A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare

http://www.sixstroke.com

 

[BigClive]

Why the first two aggressive replies? It semms a very valid question to me.

 

[MikeHalloran]

It is a very valid question. ... to ask of Briggs & Stratton.
... already done, with a negative answer.

Note that the OP is asking for some assurance of trouble- free long term operation, while pushing a boat for 10..12 hours a day. Pushing a boat is hard duty for any engine; doing it all day is much harder.

I am aware of only one common application for air cooled engines in marine service; what you might call 'longtails':

http://boghogmudmotors.com/features/

You will notice that this particular apparatus includes a u-joint between the motor and the shaft, angled a bit so the motor can sit level while the shaft angles down toward the water. Maybe they listened to B&S.

Longtails are common enough that there may be engines adapted specifically for them; apparently B&S has chosen to not serve that market.
Such an engine, to survive with a simplified shaft arrangement, would need an oiling system capable of running at a tilt, and possibly also a thrust bearing (that I doubt is present on a generic B&S) to react the propeller thrust.



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

I stick by my answer.

No where near enough information has been provided to risk contemplating modifications or especially to risk going directly against advice already given by the manufacturer.

It is a blatantly stupid question asked by someone who would know better if he was any sort of even amateur engineer. I mean, RTFM is pretty basic, but then to ignore it and ask for advice that directly contradicts it, give me a break.

If an answer where to be considered good drawings of the existing oiling system are very obviously required. Even then. 10 hours at high load with a splash feed.

But your correct Clive. I should have just red flagged it without comment.

Regards
Pat
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[BrianGar]

Here is my ''guess''

I have two B+S engines here, a horizontal and a vertical. Both look similar externally. Id buy both kinds if I was you, pull apart, study, and then try 'merge' design considerations taken into account on both at time of design to run at whatever angle you have in mind.

Obvious design considerations would probably be :

Oil level,
Splash fork style/comparisons,
Oil return from head considering 6.5hp is OHV,
Carb leveling when tilted,
And last, the oil drains from bearings,

Taking into account, that the 'similar' Honda 5.5hp runs OHV and comes in horizontal, and vertical layout, and that the Carting guys convert them all the time by :

making a different splash fork,
turn carb 90deg,
and lastly fill and file new bearing oil drain holes

: I think addressing any problems 'yourself' should be easy for any angle you want to run it at. But, you will have to strip and figure it out using 'your' head.

Asking here is daft as Pat mentioned, because we cannot know what is going on inside it when you consider the points I listed.

I would re-ask the same question on a carting forum, or perhaps forestry/farming website as they are a popular engine, and run in a lot of self built machines.

Be aware as mentioned, of any trust issues that the crank may see from prop.


Brian,

 

[dicer]

Brian has a good idea. And like others here have said, what ever you do with it, is your own design. It is an experiment, no one can say its going to last as long as you want it to. The BS vertical shaft engines usually have a little extra splash wheel that helps toss oil up into the crankshaft etc. You may get away good using something like that. Your likely going to have some power derating from the extra windage of the possible windage from partial crankshaft immersion in the oil saying nothing about the extra oil control load on rings seals etc. You need to figure out which side is best for tipping it, to limit the windage.

 

[hydroman247]

Why not use the engine vertically and get hold of the leg and gearbox of an old outboard engine with a submersed 90 degree gearbox?

 

[paskee]

Thank you for those of you who gave suggestions and their insights to the seemingly "stupid" question. They will give me a sense of the risk / return I am seeking.

Also, perhaps it is not stupid:

1. Economics, is reason one. Engines are cheap, fuel not: The best engine from B&S is the Vanguard ( warranty is 3 yrs), cost around $300. The fuel cost yearly at 12 hours daily, 1.5 liters/hr), about $8,500. If I can tilit the engine, and therefore power my propeller directly, I will avoid 5-15% transmission losses (from a pulley-belt system, a CV joint or a gear box), at say 10%, that's $850 (enough to raplace the engine 2.8x / yearly)

2. Secondly, its been done before:
a. IRRI, the International Rice Reasearch Institute, developed about 2 decades ago, an axial flow pump, which is directly coupled to tilted 5, 8 and 10 Hp engines (no brand in particular). From their drawings, I can see that the tilt is between 30-45 degrees.
b. The pump IRRI developed according to them was an improvement of similar pumps prevalently used in Asia (with tilting of engines. In Thailand, it was called the long tail pump... IRRI says its the one mechine that doubled their rice production due to the improvement in irigation.

c, Small boats in Asia are powered by small (5Hp) engines, tilted!

Lastly, for what it is worth:
1. Try to keep the forums "friendly", its great to share.. both questions and answers !
2. On manufacturers' recommendations: "Malathion" was recommended as a pesticide, disabling babies worldwide while Polio Vacination was initially discouraged ... at times just keep an open mind.

cheers..P

 

[patprimmer]

You are correct. I apologise for being rude and will now give you the answer you want and I now realise you truly deserve.

Manufacturers are always irresponsible in their recommendations. TAKE NO NOTICE OF THEM. They are only trying to milk you for extra money on a higher spec engine.

Based entirely on the information you provided, I can confidently say there is no need to worry about the oil control system design, it simply splashes oil. What could be simpler. No matter what angle you run it at some oil must end up splashing around I guess.

Same deal for the thrust. The main bearings are designed to carry the full power of the engine, so don't worry about it. Mike is just a boring old fart who is negative about everything. His years of experience with installation of engines in boats means nothing. I would just blow him off.

Just bolt it in and run it, no worries mate.

Regards
Pat
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[BrianGar]

Pat, I smiled reading your above post!

Not wanting to sound rude, or 'well off' - far from it, but at 300dollars per engine what have you got to lose? At that money they are 'almost disposable' should the 'r+d' prove difficult.

You have to ask yourself, 'is anyone going to die if it stalls' if the answer is no, then I dont see a big deal with 'you' trying a few things. If you wanted to run a tilted Cat engine for use with a hospital generator then that would be very different.

On another note, the durability of these small engines is not to be sneezed at. I once ran a briggs coupled to a generator for around 6hrs at full load with hardly any oil inside - it had drained out during transport. The engine didn't seize. I happened to check it 6hrs in for oil, and to my amazement, the little oil that was left had turned into what looked like mercury. I topped it up, and its still going strong since 11yrs later.

Extremely bad engine practice, but they are tough little units indeed.

@hydroman, Ill post a picture shortly that will make you smile, I run a similar cobbled together backup engine beside my 'mostly reliable' factory built mercury speedboat engine. Ive only used it 3 times when the mercury failed, but boys it beats rowing.

Brian,

 

[BrianGar]

Backup engine, 3hp honda mated to a 2 stroke shaft. Its not pretty, and you have to leave it down a certain way, but it always starts!

A final word paskee, this is a professional engineering forum, where professionals ask questions, and receive professional answers.
In light of this, your question has come across as a little amateurish which doesn't go down too well as this is not that sort of place. But, because its nearly Christmas, Pat just 'might' let this one run,

Other forums that your question may receive a better response could possibly be, madmodders, practical machinist, or a good search through google info.

Brian,

 

[ivymike]

If you wanted to run a tilted Cat engine for use with a hospital generator then that would be very different.

...for a number of reasons, including (1) Cat offers genset engines that are capable of running w/significant tilt and (2) they can tell you how much tilt is acceptable and what will go wrong if you exceed it which (3) is made possible because they're getting a lot more than $400/ea.

 

[BrianGar]

Well in that case, tilt it past what they recommend so, you get what I meant.....people could die if it failed and so on,

 

[patprimmer]

I think the Cat will have a reasonably deep sump and an oil pump.

The splash feed I think is more critical to oil level as it can't really pick up from the bottom of a deep sump, but once again that's a guess.

I really expected this thread to disappear, especially seeing the amateur quality of the OP and my curt/sarcastic reply 17/12. I have red flagged my post and requested the entire thread be looked at.

Regards
Pat
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[MiketheEngineer]

How about keeping it roughly level and use a universal on the shaft??

 

[paskee]

HI Mike,

The universal joint might just do it. A manufacturer (Lovejoy) specified it for up to 15 degrees. Do you (or any one) have an idea how much losses (power in %) a universal joint will consume? Belts and pulleys, according to manufacturers lose about 5-7%.

 

[patprimmer]

Universal joints won't handle much thrust I think.

As Mike Halloran stated, propellers generate thrust. It's kinda basic to how they work and is one of the main issues in "marinising" an engine.

Regards
Pat
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