Jump to content
Strawberry Orange Banana Lime Leaf Slate Sky Blueberry Grape Watermelon Chocolate Marble
Strawberry Orange Banana Lime Leaf Slate Sky Blueberry Grape Watermelon Chocolate Marble
ste_b

Flywheel Advice

Featured Posts

I've recently purchased my second boat. It's a bit of a project. ?

 

The battery isn't charging at the moment, regardless of the speed that I run the engine (Lister SR2).

 

My surveyor was the first to suggest the flywheel on my engine isn't big enough for the ratio required to run the alternator fast enough to generate power.

 

Could anyone give me any advice on this? Would replacing the flywheel with a larger one be feasible enough? It seems to me like the frame and the throttle control might be in the way of fitting a larger flywheel.

 

Thanks.

20200102_114653_HDR.jpg

Share this post


Link to post
Share on other sites

That's a pulley, not the flywheel, and a problem common on this engine. Loads has been written on here about it in infinite detail. Use the search box (top right of every page) to search for and find lots of discussion about this precise problem.

 

 

Share this post


Link to post
Share on other sites
15 minutes ago, ste_b said:

The battery isn't charging at the moment, regardless of the speed that I run the engine (Lister SR2).

 

 

On reflection, this isn't because the pulley is too small, your battery should still be charging, just not at a high enough rate. As it isn't charging at all, you say, this tells us there is also an electrical fault. 

 

 

Your surveyor has led you up the garden path!!

 

 

  • Greenie 1

Share this post


Link to post
Share on other sites

That  alternator drive pulley is on the camshaft, ''normal on those engines'' and revolves at exactly half the speed of the crankshaft so pretty slow and may not excite the alternator even if revved right up. You need a larger diameter pulley on there to speed up the alternator,  10'' and 12'' diameter taperlock pulleys are available. Also you might have a tiny 1.2 watt pea bulb in the charge warning light. If this is upgraded to say, 2.2w it should excite the alternator to charge at lower revs. In fact up to 6w but you'd probably need another bulb hold coz they're bigger.

   Also the bigger pulley would need to be fitted further out and around the other way to dodge the engine mounting bar. The alternators mountings will need to be modified to match too, re bracketed and with the use of spacers ect.

Edited by bizzard

Share this post


Link to post
Share on other sites
57 minutes ago, Mike the Boilerman said:

That's a pulley, not the flywheel, and a problem common on this engine. Loads has been written on here about it in infinite detail. Use the search box (top right of every page) to search for and find lots of discussion about this precise problem.

 

 

I realise that I've been searching for the wrong word, which hasn't helped. Engines aren't really my area of knowledge. Thanks.

Edited by ste_b

Share this post


Link to post
Share on other sites
3 minutes ago, ste_b said:

I realise that I've been searching for the wrong word, which hasn't helped. Engines aren't really my area of knowledge.

I've just edited my post above.

Share this post


Link to post
Share on other sites

If you don't want to go to these lengths, try the bigger wattage warning light bulb which should excite the alternator to charge at reasonable engine revs. But the charge rate from the alternator will be quite low due to the low rpm, but this miht suit you if your electrics are basic with nor big heavy draws on the battery.  Mind you the alternator might be faulty or its wiring.

Share this post


Link to post
Share on other sites

Looks like the same size pulley as mine. I do have to rev up a bit to kick off the alternator, had no idea changing the bulb size might do it. 

Is it possible to explain nontechnically why it would work? 

Share this post


Link to post
Share on other sites
2 minutes ago, bizzard said:

If you don't want to go to these lengths, try the bigger wattage warning light bulb which should excite the alternator to charge at reasonable engine revs. But the charge rate from the alternator will be quite low due to the low rpm, but this miht suit you if your electrics are basic with nor big heavy draws on the battery.  Mind you the alternator might be faulty or its wiring.

Thanks so much. That's all very useful. I think that will help me get somewhere.

Share this post


Link to post
Share on other sites

I wired an extra pea bulb and holder in parallel as my SR2 wasn't kicking the alternator in.

Job jobbed!

Share this post


Link to post
Share on other sites
5 minutes ago, Arthur Marshall said:

Looks like the same size pulley as mine. I do have to rev up a bit to kick off the alternator, had no idea changing the bulb size might do it. 

Is it possible to explain nontechnically why it would work? 

If your not having to rev up too much you might already have a bulb in it bigger than about 1.6w. The bit of extra resistance does it, to kick in the DC charge earlier.

Share this post


Link to post
Share on other sites
14 minutes ago, zenataomm said:

I wired an extra pea bulb and holder in parallel as my SR2 wasn't kicking the alternator in.

Job jobbed!

Yes, that or adding a resistor. Buts its easier to do that or upgrade the bulb. Showmans steam traction engines with the huge belt driven dynamo on the front to run the the lighting and a ride have a big exciter to start the current flow.

Edited by bizzard

Share this post


Link to post
Share on other sites

Now I have no way of knowing what the exact sizes of these pullies are but by measuring off the screen I come up with a step-up ratio of 2.4:1 and when it comes down to it it is the ratio that matters for any given engine speed.

 

If as stated in an earlier post the drive is taken off the camshaft then with the engine running at say 1,000 rpm the camshaft will be running at 500 rpm and the alternator at 1,200 rpm. 1,200 rpm is low for an ordinary alternator, most would seem to be designed for nearer 10,000 rpm which means the output will be low even if everything else is working perfectly.

 

Even if it were possible to increase the camshaft pulley from my measured 60 "units" to 70 and reduce the alternator pully from 25 to 20 then at 500 rpm the alternator will still be only doing 1,750 rpm, still not exactly F1 revolutions!

 

There is one possibility involving a bit of engineering which is to introduce a countershaft with a large and small pulley attached to the roughly triangular plate between the two existing pullies. By this means it should be possible to at least double the alternator's speed thus making a useful increase in the alternator's output.

Share this post


Link to post
Share on other sites
1 minute ago, Man 'o Kent said:

There is one possibility involving a bit of engineering which is to introduce a countershaft with a large and small pulley attached to the roughly triangular plate between the two existing pullies. By this means it should be possible to at least double the alternator's speed thus making a useful increase in the alternator's output.

 

Yes I was wondering about something along these lines too. But we a still barking up the wrong tree. The OP says there is "NO" charge, not "NOT ENOUGH" charge, no matter how fast the engine runs, so there must be a proper electrical failure somewhere.

Share this post


Link to post
Share on other sites
10 hours ago, Mike the Boilerman said:

 

Yes I was wondering about something along these lines too. But we a still barking up the wrong tree. The OP says there is "NO" charge, not "NOT ENOUGH" charge, no matter how fast the engine runs, so there must be a proper electrical failure somewhere.

I understand what we are saying to be ...

There won't be any charge because there isn't enough of a resistance to start the charge flow, hence the advice to change the ignition bulb for one with a bigger wattage.  Or in my case I wired in another in parallel.

Share this post


Link to post
Share on other sites
6 minutes ago, zenataomm said:

I understand what we are saying to be ...

There won't be any charge because there isn't enough of a resistance to start the charge flow, hence the advice to change the ignition bulb for one with a bigger wattage.  Or in my case I wired in another in parallel.

 

On the other hand, looking at the obvious age of the installation, I think it is safe to assume it used to work properly at some point back in the mists of time. I doubt the installation got that old by never ever working from the get go.

 

There are three possible faults at play here:

 

1) The alternator NEVER excites due to excitation current too low. This is the one most peeps here seem to think is the case. I'm inclined to disagree as it obviously used to work.

2) The alternator excites but the charging is poor. This is the fault caused by a pulley too small and run by the half speed cam. This does not fit the symptom described by the OP.

3) Something has broken, e.g. a wire or the charge indicator bulb. I think we should focus on this.

 

 

 

 

  • Greenie 1

Share this post


Link to post
Share on other sites
6 minutes ago, Mike the Boilerman said:

 

On the other hand, looking at the obvious age of the installation, I think it is safe to assume it used to work properly at some point back in the mists of time. I doubt the installation got that old by never ever working from the get go.

 

There are three possible faults at play here:

 

1) The alternator NEVER excites due to excitation current too low. This is the one most peeps here seem to think is the case. I'm inclined to disagree as it obviously used to work.

2) The alternator excites but the charging is poor. This is the fault caused by a pulley too small and run by the half speed cam. This does not fit the symptom described by the OP.

3) Something has broken, e.g. a wire or the charge indicator bulb. I think we should focus on this.

 

 

 

 

Fair comment.

I guess I'm reacting to a couple of things: -

a) Always look at the easiest and cheapest first, which I think you're also suggesting.

b) I've twice experienced exactly this with the same type of engine and alternator. Everything worked fine for years and then suddenly more resistance was required.  I've been happy simply because it was working again without thinking any deeper.

 

I guess I just accepted one of the elves had got lazy or escaped.

Share this post


Link to post
Share on other sites
19 minutes ago, zenataomm said:

Everything worked fine for years and then suddenly more resistance was required.

 

Surely less resistance is needed to increase the excitation current, given the voltage is nominally constant?

 

A bigger/higher power bulb has lower resistance, so more current, so earlier excitation, innit.

 

 

Share this post


Link to post
Share on other sites
15 minutes ago, Mike the Boilerman said:

 

Surely less resistance is needed to increase the excitation current, given the voltage is nominally constant?

 

A bigger/higher power bulb has lower resistance, so more current, so earlier excitation, innit.

 

 

Correct Mike. I could not understand what zenataomm was talking about. Its more current that may be needed to excite the alternator, nt more resistance.

 

It would not surprise me if the alternator brushes are not worn away. That woudl be indicative of having no warning lamp running or stationary.

Share this post


Link to post
Share on other sites
4 minutes ago, Tony Brooks said:

That woudl be indicative of having no warning lamp running or stationary.

 

Yes I was wondering why no-one has asked this yet too!

 

Dear OP, does the charging warning light

 

1) Illuminate before the engine starts, then go out after revving it up? Or

2) Stay alight all the time? Or 

3) Never illuminate?

 

 

Share this post


Link to post
Share on other sites

However its an old boat so the electrics may well have been bodged on bodge so it may not even have a warning lamp. Feeding the D+ direct from the battery might explain flat batteries and a non-charging alternator.  It might use a rising oil pressure switch so a faulty switch woudl prevent charging (I am not saying anything here is true or correct practice).

Share this post


Link to post
Share on other sites

Leaving aside all the other points I would go along with Boater Sam regarding the size of the alternator pulley.  I've got a smaller one than the one in the photo on my A127 alternator. Got it from a motor factors years ago.

 

Frank

Share this post


Link to post
Share on other sites
1 hour ago, Tony Brooks said:

Correct Mike. I could not understand what zenataomm was talking about. Its more current that may be needed to excite the alternator, nt more resistance.

 

It would not surprise me if the alternator brushes are not worn away. That woudl be indicative of having no warning lamp running or stationary.

Don't worry I didn't understand what I was on about either.

Share this post


Link to post
Share on other sites

To excite an alternator. A brief explanation if anyone is interested.

 

No permanent magnets in an alternator so it will not generate unless the armature is magnetised by passing a DC current through it. That current come from the ignition through the warning lamp to the brushes (via the D+ connection) running on the slip rings on the armature. Once excited and spinning it will self generate a DC voltage and retain magnetism. That is why the warning lamp goes out, it has now got +12v on both connections so no current passes.  

The Stator now generates 3 phase AC current. Rectified by a diode array and we have our 12v charging current

So if its slow to generate, passing a bit more current into the D+ terminal will increase its excitation.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.