Beta JD3 tug engines

[dmr]

Well in my experience modern buzzy engines certainly create vibration but my K1 doesn't. Unless you count two thumps a second (a frequency of 2Hz) 'vibration'.

 

On the other hand the thump from each firing stroke certainly makes the galley cupboard doors and the cutlery in the drawer rattle a bit...

 

That's an interesting one. However the twice per second thumps will also contain some higher frequencies so it will be felt as vibration.

Vibration is really just a cyclic movement and so does not have a lower frequency limit and hence even a K1 will vibrate.

A similar interesting situation exists with the sound of most slow revving engines (not yours). At lower speeds the exhaust note is percieved as a series of thumps, but at higher speeds it becomes a low frequency tone or note.

 

..............Dave

.

[dmr]

Not a whole range of frequencies really. There's mostly primary and secondary vibration (r and 2r), maybe rocking couple (depending on the engine configuration. The other vibration arising from eg gear meshing frequencies, camshafts, is normally (engine in good condition) of much lower energy.

 

We are talking (mostly) about 3 cylinder engines here and these will produce a few frequencies.

There will be the fundamental firing frequency of 1.5E (E=rotational frequency) plus a few harmonics of this 3E 4.5E etc.

There is also an out of balance at 1E (once per rev).

I strongly suspect (am almost certain) that much of the vibration n the cabin is these frequencies exciting the various resonances of the boat structure. A narrowboat is a long square box which can be surprisingly weak, especially in torsion..

 

It looks like the various K&A stoppages will prevent us moving much this winter so I might entertain myself by measuring some of these things, It will be just like been back at work!

 

............Dave

[nicknorman]

We are talking (mostly) about 3 cylinder engines here and these will produce a few frequencies.

There will be the fundamental firing frequency of 1.5E (E=rotational frequency) plus a few harmonics of this 3E 4.5E etc.

There is also an out of balance at 1E (once per rev).

I strongly suspect (am almost certain) that much of the vibration n the cabin is these frequencies exciting the various resonances of the boat structure. A narrowboat is a long square box which can be surprisingly weak, especially in torsion..

............Dave

If you're going to get all technical, may I suggest a bit of homework on the inherent balance or otherwise of various piston engine configurations. A 120 deg triple is in perfect primary and secondary balance (presuming the pistons etc are the same mass) so there is no net vibration in the vertical or lateral axes. However there is a rocking couple at 1r (which may or may not be corrected by a balancer shaft). Additionally, especially if the boat is in gear, there is of course torque oscillation at your 1.5r - the amplitude of which will depend on the engine's load. I can't see any source of 3 or 4.5r vibration unless the torque from each cylinder is not the same.

 

https://en.m.wikipedia.org/wiki/Engine_balance

Edited October 30, 2015 by nicknorman

[dmr]

If you're going to get all technical, may I suggest a bit of homework on the inherent balance or otherwise of various piston engine configurations. A 120 deg triple is in perfect primary and secondary balance (presuming the pistons etc are the same mass) so there is no net vibration in the vertical or lateral axes. However there is a rocking couple at 1r (which may or may not be corrected by a balancer shaft). Additionally, especially if the boat is in gear, there is of course torque oscillation at your 1.5r - the amplitude of which will depend on the engine's load. I can't see any source of 3 or 4.5r vibration unless the torque from each cylinder is not the same.

 

Don't really need to do my homework here, this is one of the things I used to do for a living (and still do sometimes).

I am not totally familiar with your terminology as I would regard any spurious forcing as an out of balance regardless of whether it is a force or couple. The I3, as you say, produces a 1E couple and its a pitch though usually an out of balance pulley is fitted to turn half of this into a yaw (JD3 does this).

The 1.5E is the torque reaction (2E on your I4) This has both an inertia and a combustion component. The inertia part s speed dependant, the combustion part is load dependant, and there is some cancellation that (obviously) is speed and load dependant.

This torque reaction is very non-sinusoidal, especially the combustion part, and so based on the usual Fourier stuff will produce a harmonic series hence the 3 and 4.5 etc.

Much the same apples to the noise produced from the intake and exhaust.

As an entertaining aside I do try to monitor my blood pressure and the machine usually gives a high value when the engine is running. I reckon it is packing up the low frequency pulsations from the intake.always .(or mayby a running JD3 rases blood pressure!)

[RLWP]

C'mon Nick - he's thrown Fourier at you now - you'll need a good comeback for that

 

Try a Laplace transform or a Heaviside Step Function

 

On the other hand, engines throw out all sorts of couples and harmonics, and a boat is essentially a thin walled tin box full of air. Setting off resonances is inevitable

 

Richard

 

DMR - greenie for reminding me of stuff I forgot years ago

[nicknorman]

Don't really need to do my homework here, this is one of the things I used to do for a living (and still do sometimes).

I am not totally familiar with your terminology as I would regard any spurious forcing as an out of balance regardless of whether it is a force or couple. The I3, as you say, produces a 1E couple and its a pitch though usually an out of balance pulley is fitted to turn half of this into a yaw (JD3 does this).

The 1.5E is the torque reaction (2E on your I4) This has both an inertia and a combustion component. The inertia part s speed dependant, the combustion part is load dependant, and there is some cancellation that (obviously) is speed and load dependant.

This torque reaction is very non-sinusoidal, especially the combustion part, and so based on the usual Fourier stuff will produce a harmonic series hence the 3 and 4.5 etc.

Much the same apples to the noise produced from the intake and exhaust.

As an entertaining aside I do try to monitor my blood pressure and the machine usually gives a high value when the engine is running. I reckon it is packing up the low frequency pulsations from the intake.always .(or mayby a running JD3 rases blood pressure!)

 

It's getting late so just a quick response for now, the terminology is what I learned at uni in 1975 (we did mech engineering along with civil in the 1st year of my electronic engineering degree) and I note that the same terminology is used in the wiki article, so I think it is standard. I don't see how the subject can be discussed without distinguishing between the various vibration modes (vertical/ lateral vs rocking couple vs torque).

 

The torque oscillations are primarily 1.5r but yes as you say, not totally sinusoidal and therefore containing harmonics, however I would have thought the energy at the harmonics would be pretty low especially at low engine power.

[nicknorman]

Blimey, Jeff was force feeding me gin and tonic last night, it's all a blur.

 

Anyway, the point is that a simple conceptual model of a source of excitation (the engine) and a structure with various resonant modes (the hull) surely doesn't explain the observations. One would expect the source of excitation to be on or near an antinode whereas in fact it seems it is on or near a node, with the saloon being on or near an antinode. This is what I was originally trying to explain. An better ideas?

[OldGoat]

I don't know whether you guys recall me saying early on that I'm not fussed if the JD3 is a bit clattery? Well, I AM fussed. I might just be able to feel calm if there were 2 doors shut between me and it, but how can I say to any visitors staying over "Just have a lie in whilst I get underway in the morning."? Or what's the chances of me ever taking a photo of any wildlife whilst cruising?

 

AND I never got to do the coin check cause I just put my hand on the cylinder head in prep and decided my precious 2p coin I'd got ready was going to disappear amongst the engine ina matter of seconds . I also didn't want to look a mug.

 

As Dave (dmr) will have done, I used the coin instead in the pub and found the visit worthwhile cause I got chatting to an old stager who said I should consider Gardners. Providing I stick to the routine simple maintenance required he said the engine should last & last with very little problems (Now where did I read that earlier, Dave?)

 

So, I know I've discarded a couple of boats on my internet search because they had Gardners and I'm now just going to have to find them again.

 

PS Why do I bother going out for entertainment when all I need to do is log on to the Canalworld forum? Made me splutter eating my dinner, cuthound, with the Araldite reference.....

 

 

Perhaps I shouldn't rise to the above but -

 

If you want near silent boating - then your only real practical - affordable - source of propulsion is via a cocooned and freshwater-heat exchanger cooled engine.

 

Even that won't be silent, there will be the splash of the exhaust and the ripple of the water as you glide along.

 

You ought to try a journey on a boat with a 'proper' engine Gardner, early Lister, RN, and others. All have a particular beat, particular rhythm - all have one thing in common and that is their rhythms are all on a human scale. SO a clonkety - clonk clonk is like a slow canter; quite restful.

 

If you want total silence - then boating is not for you. Even rowing or sailing has some noise attached.

[dmr]

Blimey, Jeff was force feeding me gin and tonic last night, it's all a blur.

 

Anyway, the point is that a simple conceptual model of a source of excitation (the engine) and a structure with various resonant modes (the hull) surely doesn't explain the observations. One would expect the source of excitation to be on or near an antinode whereas in fact it seems it is on or near a node, with the saloon being on or near an antinode. This is what I was originally trying to explain. An better ideas?

 

I will do some measurements over the winter.

If we both manage to do the 2016 BCN challenge then we could have a good technical debate over a few pints of beer.

Nodes, antinodes and especially modes could be a factor, but I suspect it might be simpler. We probably mostly perceive vibration as the noise produced by vibrating things, and there is far more potential for this in the saloon: the plates in the cupboard and the pans on the stove are the bad ones, plus its quieter than the engine room so these things get noticed more.

The bad one is when the perspex in the side hatch starts to shake.

 

...........Dave

[dmr]

 

 

Perhaps I shouldn't rise to the above but -

 

If you want near silent boating - then your only real practical - affordable - source of propulsion is via a cocooned and freshwater-heat exchanger cooled engine.

 

Even that won't be silent, there will be the splash of the exhaust and the ripple of the water as you glide along.

 

You ought to try a journey on a boat with a 'proper' engine Gardner, early Lister, RN, and others. All have a particular beat, particular rhythm - all have one thing in common and that is their rhythms are all on a human scale. SO a clonkety - clonk clonk is like a slow canter; quite restful.

 

If you want total silence - then boating is not for you. Even rowing or sailing has some noise attached.

 

If I wanted silence I'd get a house in the countryside (and buy a gun to shoot the birds).

The whole point of a slow revving engine is that it makes the boat throb rather nicely.

On a good day at the right speed the JD3 can do this, but sometimes and at the wrong speed everything rattles horribly.

As engineers we just have to understand this stuff so that we can make the world perfect!!!!!

 

I would love a Gardner but for now the JD3 will have to do. We do well over 1000 hours a year and just had a lovely full power thrash up a bit of the Thames,It copes with this very well and its actually not a bad engine.

 

...........Dave

[OldGoat]

 

If I wanted silence I'd get a house in the countryside (and buy a gun to shoot the birds).

.....

 

.Dave

 

Apart from the gun issue (above) you must be daft -

Owls shouting all night (and you can't see them to shoot...

Cows Farting

Badgers thumping - 'clunk' over my drain covers in the middle of the night

Blurry Nightingales singing all night

Tractors driving along 'my' lane at anti social hours

Chinooks flying at well below their allowed ceiling at any time

Deer eating The Management's roses

No services

Crap Internet speeds

 

(Oh, well we do get milk deliveries and the postie collects mail as well as delivers)

 

Nay lad, stay well away........

[anniedesigner]

 

 

Perhaps I shouldn't rise to the above but -

 

If you want near silent boating - then your only real practical - affordable - source of propulsion is via a cocooned and freshwater-heat exchanger cooled engine.

 

Even that won't be silent, there will be the splash of the exhaust and the ripple of the water as you glide along.

 

You ought to try a journey on a boat with a 'proper' engine Gardner, early Lister, RN, and others. All have a particular beat, particular rhythm - all have one thing in common and that is their rhythms are all on a human scale. SO a clonkety - clonk clonk is like a slow canter; quite restful.

 

If you want total silence - then boating is not for you. Even rowing or sailing has some noise attached.

 

Hi OldGoat. You misunderstand me. It's not a quiet/silent boat I am after, but an engine that won't rattle in my ears whenever I switch it on. A 'proper' engine is music to my ears and I could quite happily fall asleep to it. Now, having said all that, it may be that I just wasn't ready to hear how much noisier an engine is inside a boat rather than 'under & outside'. For this reason, I think I should give the JD3 the benefit of the doubt and not exclude it in my boat hunting. I may even go back and have another look at the boat I saw on Friday, but I don't think that it is the one for me irrespective of the engine sound.

[OldGoat]

 

Hi OldGoat. You misunderstand me. It's not a quiet/silent boat I am after, but an engine that won't rattle in my ears whenever I switch it on. A 'proper' engine is music to my ears and I could quite happily fall asleep to it. Now, having said all that, it may be that I just wasn't ready to hear how much noisier an engine is inside a boat rather than 'under & outside'. For this reason, I think I should give the JD3 the benefit of the doubt and not exclude it in my boat hunting. I may even go back and have another look at the boat I saw on Friday, but I don't think that it is the one for me irrespective of the engine sound.

 

That's good sense - so to my mind (if I may make so bold) - you're back on course. I would have loved to have a proper engine - but decided that usable cabin space was more important at the time, so keeping an open mind on your needs.

 

Subject to comments from those who have one, a traditional engine -

• Can have an irritating vibration at tickover
• Until you push it towards its maximum speed, the sound volume will remain (pretty well) constant. A modern engine will get progressively louder.
• It's difficult (and why would you want), to insulate the cabin from the lower frequency sounds of the engine. A small engine tucked away at the rear can be made almost silent without a huge amount of expense. Being well away from the cabin also helps.
• Generating power to charge the batteries is more of a challenge with a trad, especially if your lifestyle tends towards comforts such as oil central heating, fridge freezers and washing machines.

IIRC you first started looking at big engines because of the perceived difficulties of routine maintenance - these are easily solved for modern kit and improved even more for trads. Not insuperable for either.

 

Can you live with the space required and cabin layouts for a trad - to my mind this means a shorter rear deck, followed by a day cabin (with reduced headroom), then the engine bay. Forward of that is the living space - kitchen, saloon, bathroom, bedroom in whatever order you decide. All eminently workable for folks - but for you??

 

So please don't think of the motive power in isolation - think of the whole package.

[Athy]

 

 

 

 

• Generating power to charge the batteries is more of a challenge with a trad, especially if your lifestyle tends towards comforts such as oil central heating, fridge freezers and washing machines.

 

Eh? Where did you get that idea from? Our Gardner drives an alternator which powers up a starter battery and two leisure batteries, which in turn power the electrics. What's the difficulty?

[RLWP]

Eh? Where did you get that idea from? Our Gardner drives an alternator which powers up a starter battery and two leisure batteries, which in turn power the electrics. What's the difficulty?

 

Something has got lost somewhere. These 'difficult' vintage engines were designed to go in boats, water pumps, lorries, generators, grain dryers and a whole bunch of applications. All were operated by very low skilled people and consequently designed to be maintenance tolerant and tamper proof.

 

Your engine is doing pretty much what it was designed for and with an owner with the appropriate skills

 

Richard

[Athy]

 

Something has got lost somewhere. These 'difficult' vintage engines were designed to go in boats, water pumps, lorries, generators, grain dryers and a whole bunch of applications. All were operated by very low skilled people and consequently designed to be maintenance tolerant and tamper proof.

 

Your engine is doing pretty much what it was designed for and with an owner with the appropriate skills

 

Richard

File under "compliments, backhanded". But yes, pretty much. It was about two years before I found out where you put the oil in, as it never uses any! (I knew that because I actually had found out where to check the oil).

[RLWP]

Yes - you're probably over qualified, truth be told

 

Richard

[OldGoat]

Eh? Where did you get that idea from? Our Gardner drives an alternator which powers up a starter battery and two leisure batteries, which in turn power the electrics. What's the difficulty?

 

There have been threads on here about the challenges of getting sufficient 'gearing' from slow speed engines to get high output from modern alternators.

Now for an enthusiast such as your goodself, wrapping a belt around a flywheel and keeping it in place may not be a challenge. Couple that with less frugal power demands of today's users and lack of mechanical ability, makes me say that 'there's a consideration'

 

You may recall the thread earlier this year about an SR3 (OK not that sort of traditional engine or installation) - who couldn't get a reasonable amount of power output .

 

So I felt it was a caveat worth mentioning.

[Athy]

 

 

So I felt it was a caveat worth mentioning.

Yes, you are correct, it was, just as I felt that it was worth mentioning that I'd had no problems getting my engine to make electricity, so not every engine will suffer from such a problem.

 

Come to think of it, the Rigas Dizelis in our last boat powered our alternator perfectly well. Our first boat, which had a Petter, did have a problem: lights would fade towards the end of the evening, we had to switch the fridge off at night. But that boat had only one leisure battery; as newcomers to boat ownership back then (late 1990s) we did not realise that some boats had more.

[RLWP]

 

There have been threads on here about the challenges of getting sufficient 'gearing' from slow speed engines to get high output from modern alternators.

Now for an enthusiast such as your goodself, wrapping a belt around a flywheel and keeping it in place may not be a challenge. Couple that with less frugal power demands of today's users and lack of mechanical ability, makes me say that 'there's a consideration'

 

You may recall the thread earlier this year about an SR3 (OK not that sort of traditional engine or installation) - who couldn't get a reasonable amount of power output .

 

So I felt it was a caveat worth mentioning.

 

One of the features of the SR and similar engines (LR, ST, SL, HSR, etc.), none if which are considered 'vintage', is that the drive for the alternator is taken from the camshaft i.e. at half engine speed. On top of that, as built, they were designed to run a simple generator to recharge the starter battery.

 

It's dead easy to fit a larger pulley to drive a higher output alternator for modern living

 

And none of this is relevant to engines in engine rooms - you very rarely find such engines in such luxurious accommodation

 

Richard

[Paul C]

 

If I wanted silence I'd get a house in the countryside (and buy a gun to shoot the birds).

 

Have you heard the noise a forage harvester makes when its chopping/conditioning silage?

 

Not to mention, the daily milk tanker runs (probably in the night time), the weekly slurry spreading, the occasional farm development/building works, the twice daily herding the cows up and down your road, the relief milker arriving at 5am opening and closing gates, etc etc

 

The countryside is alive - literally - with things going on. One of those is narrowboat engines.

[Athy]

 

 

 

The countryside is alive - literally - with things going on.

What's more, some of those agricultural noises will probably sound rather like a JD3, as it is a marinised John Deere tractor engine.

[ditchcrawler]

 

There have been threads on here about the challenges of getting sufficient 'gearing' from slow speed engines to get high output from modern alternators.

Now for an enthusiast such as your goodself, wrapping a belt around a flywheel and keeping it in place may not be a challenge. Couple that with less frugal power demands of today's users and lack of mechanical ability, makes me say that 'there's a consideration'

 

You may recall the thread earlier this year about an SR3 (OK not that sort of traditional engine or installation) - who couldn't get a reasonable amount of power output .

 

So I felt it was a caveat worth mentioning.

I fitted a larger pulley to the front of our BD3 to get better charging. Its in the engine room and I had the space. It only drives the domestic alternator so sits in front of the water pump pulley etc. so lots of room.

[Loafer]

I fitted a larger pulley to the front of our BD3 to get better charging. Its in the engine room and I had the space. It only drives the domestic alternator so sits in front of the water pump pulley etc. so lots of room.

Blimey dc, the pulley on our BD3 is massive. How on earth did you fit a bigger one? Ours is about 13" diameter driving two belts and two alternators. Is yours not the same?

[ditchcrawler]

Blimey dc, the pulley on our BD3 is massive. How on earth did you fit a bigger one? Ours is about 13" diameter driving two belts and two alternators. Is yours not the same?

Yes, I think the original when I bought it was about 7"