4LW heartbeat

[jenevers]

When tootling along the canal I listen to the heartbeat of my 4LW.

There is a distinct DUM DUM DUM DUM beat.

For each beat I think I'm right in saying that the crank actually rotates 4 times.

So if I count the number of beats in 6 seconds then multiply by 10 it gives me the RPM.

Is this correct?

I don't have a tachometer ( never really seen the need on a canalboat!)

[Paul G2]

When tootling along the canal I listen to the heartbeat of my 4LW.

There is a distinct DUM DUM DUM DUM beat.

For each beat I think I'm right in saying that the crank actually rotates 4 times.

So if I count the number of beats in 6 seconds then multiply by 10 it gives me the RPM.

Is this correct?

I don't have a tachometer ( never really seen the need on a canalboat!)

No. According to your criteria you need to multiply by 10 then by 4 to get the RPM.

[john6767]

If you don't want to fit a tachometer, then you could always get one of these and calibrate your ears.

[jenevers]

No. According to your criteria you need to multiply by 10 then by 4 to get the RPM.

Hmm.......in other words multiply by 40??????????? How do you come to that conclusion?

[MtB]

On a four stroke four cylinder engine each 'beat' (i.e. firing stroke) represents half a revolution of the crankshaft (I think!)

 

So divide the 'bangs per second' by two to get revs per second. Or multiply by 30 to get revs per minute.

 

 

MtB

[koukouvagia]

On a Kelvin K2 I count how many ker-chunks there are in half a minute and double the number. Usually the answer is about 250 rpm when cruising at normal speed and about 100 rpm when idling.

I have been known to ratchet the speed up to a dizzying 500rpm on the river Severn.

[jenevers]

On a four stroke four cylinder engine each 'beat' (i.e. firing stroke) represents half a revolution of the crankshaft (I think!)

 

So divide the 'bangs per second' by two to get revs per second. Or multiply by 30 to get revs per minute.

 

 

MtB

Ahh! But i get 11 "DUMs" every 6 seconds at idle. that's 110 every minute. I know my idle speed is 440 RPM so a DUM must equal 4 RPM. I should have mentioned that for each DUM there's a" ticky-ticky" which is 4 valve "ticks".............. Dums , ticks, beats, bangs.....it's all very confusing!

[LEO]

Ahh! But i get 11 "DUMs" every 6 seconds at idle. that's 110 every minute. I know my idle speed is 440 RPM so a DUM must equal 4 RPM. I should have mentioned that for each DUM there's a" ticky-ticky" which is 4 valve "ticks".............. Dums , ticks, beats, bangs.....it's all very confusing!

 

Hi,

 

How do you know it's 440rpm?...............

 

L (2LW - so a third less Dums?).

[mark99]

suck, squeeze, bang, blow is a 4 stroke cycle.

 

each cycle above is 1/2 crank revolution so is that not two crank revs per bang?

[Athy]

This must be the anorackiest thread which has ever run on CWF, real beard-stroking territory.

 

Now, how do I work out how fast my 2LW is running?

Edited March 5, 2014 by Athy

[mark99]

This must be the anorackiest thread which has ever run on CWF, real beard-stroking territory.

 

Now, how do I work out how fast my 2LW is running?

 

Divide the sucks by the blows and add the squeeze. Then bang your head!

[Proper Job]

This must be the anorackiest thread which has ever run on CWF, real beard-stroking territory.

 

Now, how do I work out how fast my 2LW is running?

Try working it out for a V4 Honda

 

http://youtu.be/MwEbwKBic6w

 

No wonder they fit a tacho

 

[mark99]

http://www.youtube.com/watch?v=OGj8OneMjek

 

Two revs per bang as above.

[billh]

When tootling along the canal I listen to the heartbeat of my 4LW.

There is a distinct DUM DUM DUM DUM beat.

For each beat I think I'm right in saying that the crank actually rotates 4 times.

So if I count the number of beats in 6 seconds then multiply by 10 it gives me the RPM.

Is this correct?

I don't have a tachometer ( never really seen the need on a canalboat!)

If you don't see a need for a tacho on the boat, why concern yourself with trying to count dums, ticks and bangs? Surely the fact that the engine runs satisfyingly slow with a nice sound is enough? The actual RPMs aren't important. Our engine idles at something under 200 and is flat out at 700 and it isn't a Kelvin K (or a Bolinger)

[Nightwatch]

I feel I am detached from this thread.

 

When cruising our engine revs at something like 1100 revs.

 

Martyn

[Proper Job]

I feel I am detached from this thread.

 

When cruising our engine revs at something like 1100 revs.

 

Martyn

As do most peoples

[Nightwatch]

But I would prefer a dum,dum,de dum type of engine.

 

Martyn

[Athy]

Divide the sucks by the blows and add the squeeze. Then bang your head!

Ah, a scientist! Thanks for the formula.

 

(Wanders off, stroking beard in a puzzled manner).

[Proper Job]

But I would prefer a dum,dum,de dum type of engine.

 

Martyn

You have got one

 

.............. they just happen a lot closer together

[jenevers]

If you don't see a need for a tacho on the boat, why concern yourself with trying to count dums, ticks and bangs? Surely the fact that the engine runs satisfyingly slow with a nice sound is enough? The actual RPMs aren't important. Our engine idles at something under 200 and is flat out at 700 and it isn't a Kelvin K (or a Bolinger)

Because it's something to do to keep the brain active and it's an interesting exercise.

[Nightwatch]

You have got one

 

.............. they just happen a lot closer together

How good of you to say that. Makes me feel better and included! A little!

 

I NEED money!!!

 

Anyone got any spare?

[MtB]

suck, squeeze, bang, blow is a 4 stroke cycle.

 

each cycle above is 1/2 crank revolution so is that not two crank revs per bang?

 

One MAJOR factor missing from your formula:

 

...PER CYLINDER

 

 

So yes, two crank revs per bang on a single cylinder engine (like my K1 for example).

 

But when there are FOUR cylinders turning that crank, your second comment should read:

 

"each cycle above is 1/2 crank revolution so is that not two crank revs per four bangs?"

 

 

I'll get my anorak.....

 

 

MtB

P.S. If I'm right, this supports my earlier assertion that on the OP's 4LW, each bang represents half a crank revolution.

[mark99]

 

One MAJOR factor missing from your formula:

 

...PER CYLINDER

 

 

So yes, two crank revs per bang on a single cylinder engine (like my K1 for example).

 

But when there are FOUR cylinders turning that crank, your second comment should read:

 

"each cycle above is 1/2 crank revolution so is that not two crank revs per four bangs?"

 

 

I'll get my anorak.....

 

 

MtB

P.S. If I'm right, this supports my earlier assertion that on the OP's 4LW, each bang represents half a crank revolution.

 

 

Another complication would be firing order - a 4 cylinder may fire two at once. Some petrol ones do iirc. (big bang engines) albeit rare.

Edited March 5, 2014 by mark99

[MtB]

 

 

Another complication would be firing order - a 4 cylinder may fire two at once. Some petrol ones do iirc.

 

 

But surely not on the 4LW we are discussing...

 

 

Even so, I've never heard of this. Are you sure you're not thinking of the alternative crankshaft format for a two cylinder IC engine where the pistons rise and fall in unison, in order to give a regular firing pattern?

 

If not, I'd be very interested to hear which four cylinder petrol engines have two cylinders firing together!

 

 

MtB

[mark99]

I remember a few odd ones on motorbikes - when I used to subscribe to their mags, but they were specialist.

 

ETA link.

 

 

http://en.wikipedia.org/wiki/Big-bang_firing_order

 

The firing order on racing bikes was experimented with to try to get better tyre grip - I'm not sure but electronic traction control probably took over.

Edited March 5, 2014 by mark99