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Balancing a coin on your Gardner.


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Any engine is going to have very little vibration if its rigidly bolted to 20 tons of boat. I suppose I should say almost any any engine as big old single cylinder Bollinder (or Kelvin) is a bit different. Vertical forcing is dictated by piston mass and engine plus boat mass so the idea that engines from some manufacturers are extra smooth is a bit of a myth.  I suspect the Lister had heavier pistons than the Gardner so my theoretical explanation has just fallen flat on its face ?t. Suspect the Lister had a heavier block though. Did you compare at similar engine speeds?

 

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

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13 minutes ago, mark99 said:

2lw .... can put a pound coin on its edge on rocker cover and it does not move. With engine running obvs. Little party trick for gongoozlers.

It even works with a Beta JD3 ?

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26 minutes ago, Man 'o Kent said:

A threepenny bit is the denomination of choice on a Moto Rumi. :rolleyes:

Surely you can only expect a theepenny bit to stand up on a British engine ?

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I think it all relies on the correct fitting of the engine. Until recently, I had a Gardner 2L2 & a pound coin balanced on the rocker covers would remain perfectly still throughout the entire Rev range, but the boat I had prior to this was fitted with a Kelvin J2 & you wouldn’t have balanced a can of coke on that. I know they were different engines, but one was fitted well, the other wasn’t. 

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13 hours ago, dmr said:

Surely you can only expect a theepenny bit to stand up on a British engine ?

I seem to remember that the Vincent Comet was described as the "vibrationless single" but I never got around to trying a thrupenny bit on mine

The italians don't do a 12 sided coin as far as I know so it's Hobson's choice!

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24 minutes ago, Man 'o Kent said:

I seem to remember that the Vincent Comet was described as the "vibrationless single" but I never got around to trying a thrupenny bit on mine

The italians don't do a 12 sided coin as far as I know so it's Hobson's choice!

Ill have to investigate that, its not easy to make a vibration free single. I watched an old boat with a Bolinder go past and I could see the entire back of the boat bobbing up and down. Ive also driven a boat with a Kelvin K1 and you can just see the boat rock with the torque reaction to the engine firing.

 

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

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Do the bearers have an effect? Our engine (2LW) is bolted down on (or perhaps through) solid oak bearers, which the builder (Mel Davis) told us would reduce vibration compared with an engine bolted directly to metal. It looks very firm when running, though I have not yet tried balancing a coin on it.

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I could certainly do this on my K2 Kelvin.  Mind you, it had some pretty substantial steelwork supporting it.   

It was bolted directly onto the steel bearers.

 

Somewhere I've got a video but I can't for the life of me find it!

 

wfbc4.jpg.f24cded22c4e662bbd5ff4bc5f5e54d2.jpg

Edited by koukouvagia
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4 hours ago, Athy said:

Do the bearers have an effect? Our engine (2LW) is bolted down on (or perhaps through) solid oak bearers, which the builder (Mel Davis) told us would reduce vibration compared with an engine bolted directly to metal. It looks very firm when running, though I have not yet tried balancing a coin on it.

My educated guess is that if done properly timber bearers might reduce some of the higher frequency vibration but are unlikely to improve the low frequency stuff, and its likely the low frequency stuff that makes the 50p/pound/thrupence fall over.

 

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

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On 17/08/2020 at 11:01, Athy said:

Do the bearers have an effect? Our engine (2LW) is bolted down on (or perhaps through) solid oak bearers, which the builder (Mel Davis) told us would reduce vibration compared with an engine bolted directly to metal. It looks very firm when running, though I have not yet tried balancing a coin on it.

Mine also has solid oak bearers and runs smoothly.  It is worth checking that all of the bolts are still tight of course.  Initally one of my injectors was not 100% but after getting all three reconditioned smoothness returned.

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On 17/08/2020 at 10:49, dmr said:

Ill have to investigate that, its not easy to make a vibration free single. I watched an old boat with a Bolinder go past and I could see the entire back of the boat bobbing up and down. Ive also driven a boat with a Kelvin K1 and you can just see the boat rock with the torque reaction to the engine firing.

 

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

Stand on the back of an unconverted wooden boat with a bolinder and at certain speeds you can see torsional waves running down the length of the boat!

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9 minutes ago, David Mack said:

Stand on the back of an unconverted wooden boat with a bolinder and at certain speeds you can see torsional waves running down the length of the boat!

I bet. In engineer speak an unconverted boat is an "open channel" which is famed for torsional weakness, though a closed box like modern narrowboats is not much better. We have the stove, most furniture, the bathroom/holding tank and bed/underbed storage all on the same side of the boat. Trim is restored by having the engine offset to the other side with the battery bank behind it. I do wonder how much static twist this has put into the shell.

 

...............Dave 

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