Kelvins - my thinking develops...

[smileypete]

I'm almost inclined to try ploughing my own furrow here. Stacks of steel stiffening of the hull in the engine room but the engine actually mounted on timbers. Especially as we have decided to use a lorry propshaft with U/Js for ecomomy as opposed to a new stern tube and solid propshaft all accurately aligned. I think a solid propshaft actually has enough flexibility to take up all the movement I'd expect in a timber fishing boat hull anyway.

 

Have a look inside a washing machine to see how it's done: Add mass, THEN isolate.

 

Try a google for 'concrete inertia block'.

 

cheers,

Pete.

Edited June 13, 2010 by smileypete

[BEngo]

Right, I've read the installation instructions on Mike Skyner's site. Is this what you are referring to?

 

Yes

 

 

I'm not sure if you are suggesting softwood bearers which are capping timbers resting lengthwise on steels below, or really BIG transverse softwood bearers supported at each end only. The latter seems intuitively to offer more shock absorption capability to me. I am also having difficulty resolving the apparent need to align the engine when a rigid propshaft is used to within x thousandths of an inch and the engine is sitting on bendy timber bearers as recommended by Kelvin above. Fat chance of alignment remaining correct.

 

 

Really big (at least 4x4) on transverse steel bearers all the way across. The engine would be bolted to the wood only and the wood separately boleted to the steelwork. My J2 was the first Kelvin installed by Phil Trotter's team- according to Phil at the time, and that is how it was done. In a wooden boat everything moves in a seaway so on average it is aligned most of the time! If you read the alignment instructions from Bergius they refer to some basic carpentry tools- a straightedge and a pencil to mark the shaft coupling. These will not get you into thous territory, but might do a thin 64th. I have thought of massive timber bearers supported only outboard of the engine, as a sort of shock absorbing arrangement, but that might go into a vertical bounce at some critical engine speed. [

 

I'm almost inclined to try ploughing my own furrow here. Stacks of steel stiffening of the hull in the engine room but the engine actually mounted on timbers. Especially as we have decided to use a lorry propshaft with U/Js for ecomomy as opposed to a new stern tube and solid propshaft all accurately aligned. I think a solid propshaft actually has enough flexibility to take up all the movement I'd expect in a timber fishing boat hull anyway.

 

 

 

Yes, I like this thinking. with a propshaft you don't want accurate alignment so that the UJ's actually have some movement and will last longer..

 

However, given a solid shaft plus timber mountings in a fishing boat means the weight of one end of a solid shaft is resting on the bearings of the gearbox tailshaft anyway, why bother with a plumber block at the forward end of a (lighter) cardan shaft propshaft in a narrowboat anyway? The side-thrust generated at the gearbox end generated by the prop thrust acting on the offset in the propshaft offsets the weight of the propshaft anyway. (Did that make sense?)

 

I would not bother with a front plummer block though I'm not sure how a side thrust might offset the vertical weight load- or are you referring to a vertical offset as well as or instead of a lateral one?

I like the way you think BEngo, but the reinforcing you describe seems inadequate by the standards of the other 'names' in the busness. Have you installed any K series Kelvins on timber bearers in modern fabricated hulls? How did they work out?

 

My J2 sits in a modern fabricated hull, and is thoroughly well reinforced in to the hull. It was built to my design by Phil Trotter, at Saul, over 20 years ago. The fuel tanks surround the bearers, so stiffeness is a given. I would have suggested a simialr arrangement but assume you already have a fuel tank and would like to keep the cost to change down. I think if you put channel section bearers right across the boat, gusset them fore and aft vertically below the engine and gusset them into the sides then you will have enough stiffness. The wooden bearers will take out some of the 'thump'- how the boat will behave depends on where the engine is, how stiff the rest of the hull is (usually pretty good in all directions for a standard tin slug, but pretty poorlongitudinally and torsionally for an open motor) and where any other major weights are in relation to the engine. This is either complicated computer programme country or suck it and see. The millenium ( wobbly) bridge was another example of this, but the computer output wasn't right ( probaly because it was fed wrong assumptions).

 

At the end of the day you have to go with what you feel comfortable with. If you are near Aylesbury you are welcome to have a look at my set up.

 

Regards N

[robkg]

Hi Mike,

 

I have a K2 fitted in a modern 70' shell. The engine was bolted to transverse steel bearers with no wood in sight, by the shell builder. I have fitted a horizontal stay bar as Kelvin envisaged, which runs from the intended location about halfway up one of the cylinders to a reinforcing plate welded to the side of the hull. At tickover the boat rocks very slightly with each fire of the engine but not obtrusively so and when cruising there is no issue at all.

I carried out the rest of the engine installation myself. The propshaft arrangement is as follows:

The 2" shaft runs through a conventional stern tube then through a splittable, plummer block phospher bronze bush (about 1' away from the stern tube)which provides the shaft with two points of support. The rest of the distance (approx. 12') is an agricultural PTO shaft made for me by an agricultural supplier. It consists of a flanged U.J. at each end with a single piece of "Lemon Tube" in between. I had a second length of the smaller section of tube inside this for extra rigidity. These shafts are intended for conveying hundreds of horsepower at 540 rpm in very arduous conditions, and have the added advantage of being much lighter than lorry driveshafts.

Also this arrangement allowed the engine to be installed horizontally at the right height and allowed sufficient clearance for the back cabin door to open over the top of the guarded shaft without having to have the suspended floor too high

 

The reason I did not go for an accurately aligned rigid drive, was that the shell builder did not think it was possible to weld in the stern tube boss with sufficient precision to line up with the gearbox output shaft some 12 ' further forward, and I tend to agree with him. Also I have heard comments about shell movements due to road transport, thermal effects etc. upsetting this alignment which has the potential of causing significant problems.

 

The arrangement that I have got works very well with no apparent snags to date.

 

Apologies if my description is not very clear.

 

Rob

 

P.S. I am not convinced of the argument that U.J.s are not able to take thrust, as the needle roller bearings are required to take high turning forces when operating and the thrust forces are acting in exactly the same way. (But maybe this is an discussion for a seperate thread)

 

P.P.S. Now I think about it, I am not entirely convinced that wooden bearers would make any appreciable difference to vibration, as assuming the section of wood used is sufficiently robust and durable enough to support the engine, I can't see it having any real give in it anyway.

[MtB]

Hi BEngo,

 

Thanks for your reply

 

Really big (at least 4x4) on transverse steel bearers all the way across. The engine would be bolted to the wood only and the wood separately boleted to the steelwork. My J2 was the first Kelvin installed by Phil Trotter's team- according to Phil at the time, and that is how it was done. In a wooden boat everything moves in a seaway so on average it is aligned most of the time! If you read the alignment instructions from Bergius they refer to some basic carpentry tools- a straightedge and a pencil to mark the shaft coupling. These will not get you into thous territory, but might do a thin 64th. I have thought of massive timber bearers supported only outboard of the engine, as a sort of shock absorbing arrangement, but that might go into a vertical bounce at some critical engine speed.

 

Interesting that Phill Trotter installed your Kelvin on timber bearers. If I understood him correctly during our recent phone conversation he is now of the view that timber bearers are bad news, metal to metal is essential.

 

My idea about mounting the engine on timbers supported at each end was an attempt to copy the 'washing machine' method of isolation mentioned by smileypete but as you point out, the engine/timber system will have a resonant frequency which will be hard to predict. If it falls inside the engine speed range I'll be in trouble. A washing machine has telescopic dampers to deal with that problem but I don't think dampers big enough to cope with a 1.2 ton engine will be easy to specify, or install right first time, so that idea is definitely OUT.

 

I would not bother with a front plummer block though I'm not sure how a side thrust might offset the vertical weight load- or are you referring to a vertical offset as well as or instead of a lateral one?

 

Yes sorry, I didn't mean 'side thrust', I should have said 'offset thrust' which in this case is vertical. The force acting perpendicularly on the axis of the propeller and output shafts created when end thrust is applied to the cardan shaft bridging the offset in their alignment. The vertical thrust at the gearbox end will be vertical and will therefore offset the weight of the propshaft on the tailshaft bearing. I think the tailshaft bearing is designed to support the weight of the forward end of a solid propshaft anyway so I agree, we won't need a forward plumber block. In addition, Kelvin don't suggest using plumber blocks in their installation instructions or diagrams from which I infer the tailshaft bearings are designed to take the weight. You touched on this in your '"Shaft droop" thread back in 2008: http://www.canalworld.net/forums/index.php...38&hl=droop A plumber block or bearing to protect the stern tube WILL be needed however, as the offset force is combining with the weight of the propshaft at that end.

 

My J2 sits in a modern fabricated hull, and is thoroughly well reinforced in to the hull. It was built to my design by Phil Trotter, at Saul, over 20 years ago. The fuel tanks surround the bearers, so stiffeness is a given. I would have suggested a simialr arrangement but assume you already have a fuel tank and would like to keep the cost to change down. I think if you put channel section bearers right across the boat, gusset them fore and aft vertically below the engine and gusset them into the sides then you will have enough stiffness. The wooden bearers will take out some of the 'thump'- how the boat will behave depends on where the engine is, how stiff the rest of the hull is (usually pretty good in all directions for a standard tin slug, but pretty poorlongitudinally and torsionally for an open motor) and where any other major weights are in relation to the engine. This is either complicated computer programme country or suck it and see. The millenium ( wobbly) bridge was another example of this, but the computer output wasn't right ( probaly because it was fed wrong assumptions).

 

At the end of the day you have to go with what you feel comfortable with. If you are near Aylesbury you are welcome to have a look at my set up.

 

Regards N

 

Now the rattly K2 installation we saw had bearers the full with of the hull as you describe, and I reckon they were bending because I could see the heads on the engine jerking sideways by a couple of millimetres on each cylinder fire, even at tickover, and the hull was just wobbling like a jelly in response. So I think we'll need something more than that. The most stable K2 installation I've seen (in Koukouvagia's 'Owl') has IIRC short transverse bearers welded between 12" high longtidudinal plates, or webs, running the full length of the engine room, which are in turn braced to the sides of the hull with multiple transverse web plates also 12" high, and welded into steel bulkheads front and rear of the engine room. The results in the engine appearing to be installed low in the boat in a 'well-like' arrangement, but it the effect is actually due to the floors being unusually high. This also seems similar to Stuart Garners description of the K1 installation in his boat 'Catkin'. I like this arrangement and will discuss it in more detail with Dave who will be fitting this for us.

 

And thanks for the offer, yes please, I'd very much like to see your set-up! I'll pm you when I have time, will be a week or so yet.

 

Cheers, Mike

 

Editted to change the lurid green text to ease MoominPapa's eyeballs. (It was hurting mine too!)

Edited June 15, 2010 by Mike the Boilerman

[MoominPapa]

Mike,

 

Please could you choose a different font/colour for quotes? The neon-green bold is making my eyeballs explode.

 

MP.

 

Sorry, looking back I see that the green came from BEngo. Same complaint, different target.

Edited June 15, 2010 by MoominPapa

[MtB]

Apologies if my description is not very clear.

 

Hi Rob, your description is perfectly clear and understood, thanks! Never heard of 'lemon tube' until now. Vry interesting.

 

P.S. I am not convinced of the argument that U.J.s are not able to take thrust, as the needle roller bearings are required to take high turning forces when operating and the thrust forces are acting in exactly the same way. (But maybe this is an discussion for a seperate thread)

 

P.P.S. Now I think about it, I am not entirely convinced that wooden bearers would make any appreciable difference to vibration, as assuming the section of wood used is sufficiently robust and durable enough to support the engine, I can't see it having any real give in it anyway.

 

I've been thinking similarly about UJs. The needle can't tell which way they are being pushed. I wonder if the problem is the central crucifix shattering if subjected to shock, like when one's prop starts moving a mixture of rocks and water as I've found can happen when the bottom gets too near the top... But further, I seem to remember one of my early Triumph Sptifires having rear suspension configured such that the two half-shafts (each with two UJs) doubling in function as radius arms. Major end thrust there, and designed in by the car manufacturer.

 

I think wooden bearers have the capability to reduce the highest frequency components of the shock on each firing stroke. Lower frequency energy will go straight through. The main benefit will be the reduction of the risk of metal fatigue in my opinion, so possibly well worth having. Not sure how many boats sink through metal fatigue. None I suspect, but I'm suprised it isn't more of a problem when whacking great diesels are put in farbricated shells.

 

Cheers, Mike

[WotEver]

...I seem to remember one of my early Triumph Sptifires having rear suspension configured such that the two half-shafts (each with two UJs) doubling in function as radius arms. Major end thrust there, and designed in by the car manufacturer.

I seem to recall that Jag rear subframes (as fitted to the XJS among others) were the same, weren't they? Inboard discs for the handbrake, and shafts as you describe.

 

Tony

[BEngo]

Mike,

 

Please could you choose a different font/colour for quotes? The neon-green bold is making my eyeballs explode.

 

MP.

 

Sorry, looking back I see that the green came from BEngo. Same complaint, different target.

 

 

But bright colours are just so canal....and Kelvins were a strange shade of green. ( Actually I would have used RED, but I thought it might be a bit too antagonistic a shade).

 

N

[MoominPapa]

But bright colours are just so canal....and Kelvins were a strange shade of green. ( Actually I would have used RED, but I thought it might be a bit too antagonistic a shade).

 

N

 

As any fule kno, the only shade of green worth having is mid brunswick green

 

MP.

[MtB]

As any fule kno, the only shade of green worth having is mid brunswick green

 

MP.

 

Well I changed the text colour to Kelvin Green actually, or so I thought!

 

Or is that the same?

[NB Alnwick]

As any fule kno, the only shade of green worth having is mid brunswick green

 

MP.

 

Isn't that the colour that was generally preferred on the old Gas Works Railway for all their little tank engines?

[RLWP]

'tis true.

 

British Racing Green, now, there's a colour

 

Richard

 

 

[NB Alnwick]

'tis true.

 

British Racing Green, now, there's a colour

 

Richard

 

 

 

Richard,

 

You didn't tell me you had one of those in the garage . . .

[RLWP]

If only.

 

<sigh>

 

Richard

[Pluto]

'tis true.

 

British Racing Green, now, there's a colour

 

Richard

 

 

British Racing Green is actually any green you want as the exact shade is not specified. Some ERAs used a very light green in the 1930s, and it was still British Racing Green. Bentley, of course, was a railway engineer, so his cars do tend to over-engineering and excessive weight. The Blower Bentleys were also over stressed and never that reliable. Ahh, they don't make em like that anymore.

[RLWP]

British Racing Green is actually any green you want as the exact shade is not specified. Some ERAs used a very light green in the 1930s, and it was still British Racing Green. Bentley, of course, was a railway engineer, so his cars do tend to over-engineering and excessive weight. The Blower Bentleys were also over stressed and never that reliable. Ahh, they don't make em like that anymore.

 

I know, it's a wonder with all that over engineering and weight he ever managed to make anything light:

 

 

Bentley BR2

 

Richard

[MtB]

I know, it's a wonder with all that over engineering and weight he ever managed to make anything light:

 

 

Bentley BR2

 

Richard

 

 

Thanks Richard. I want one of THOSE in my boat now instead of the K1 :-) What size prop would one put on it? I'm guessing an airscrew about 60" x 30" would be in the right ballpark....

 

But seriously, to update the board, decisions have been made. Both the boat and the engine have now been delivered to Dave at Hilmorton and work begins on Monday :-D

 

First job is to cut a soft patch in the roof and lift out the BD3. Dick Goble has agreed to give us his guidance on a consultancy basis so once the BD3 is out we will all have a meeting to discuss and design the new steelwork to be installed. Dave will then install the steelwork in his dry dock and physically fit the engine. Further decisions have been made to stick with the J transmission and have conventional trad-style controls.

 

The hydraulic drive idea was dropped because I'm concerned about the viability of a hydraulic system on such a low speed engine and having seen one, it just didn't seem 'right' to do that to a Kelvin. We abandoned the idea of a PRM on a gravestone hidden under the floor to get Teleflex controls and avoid converting the propshaft to fully floating because PRM don't seem to have a 1:1 forward/reverse in their product range, the low engine speed again seems to be a problem with a hydraulically operated transmission anyway, and PRMs cost a bucketload of money too.

 

So The J transmission will be used with a floating propshaft comprising a plumber blocks by the stern tube and the transmission output shaft, and a new cardan shaft joining the whole thing together. This also lets us fit the engine three or four inches off-centre to allow a bit more passage width to walk past the 31¼" diameter flywheel. Batteries will be moved from port side to under the floor on the starboard side to help offset the resulting list.

 

In order to avoid the rather clumsy and very long Renolds chain most Kelvin installations seem to have hanging in the middle of the engine room connecting the forward/reverse sprocket to the steerer's gear control shaft, Dave will install a layshaft under the floor so the long chain connection can descend against the BMC bulkhead out of the way. The layshaft will them connect with a second Renolds chain emerging from the underfloor space to connect to the forward/reverse sprocket on the transmission. MUCH tidier. Could also be done using two pairs of crownwheels and pinions.

 

I'll post again as the work progresses!

 

Cheers, Mike

 

P.S. Had a pleasant afternoon at Braunston today. Was rather expecting to see a variety of interesting engines but it seemed to be wall-to-wall Listers! Can't help feeling I was missing something....