4Lw Measuring Revs

[Chris Pink]

Two part question really;

 

1. How do I measure the revs on a 4LW (how can I fit a rev counter?)

 

2. My engine, whether in or out of gear reaches a point (at unknown revs see 1.) when it vibrates so much it is unusable. Is it possible to rev the engine on an ordinary throttle past where it should go? Should it not be governed so it can't go past this point? It has a 24" propellor of unknown pitch on a 14 ton boat so could it be seriously underpropped?

 

 

 

I realise that I may not have put this in such a way that enables a diagnosis but questions to help arrive at one gratefully received.

 

thanks.

Edited July 26, 2013 by Chris Pink

[Timleech]

The original way to fit a rev counter was via a little adapter gear which bolts to the end of the camshaft, in place of the little round cover plate (usually part hidden by the flywheel housing).

Much easier now to use an electronic tacho driven from the alternator, but finding one with a low enough rev range is not easy.

 

The engine should be controlled by the governor such that it won't go past the decreed maximum revs. This might be 1700 rpm if it's an ex-vehicle engine, most marine engines would be governed to 1500 rpm or less.

 

Tim

[Chris Pink]

If that's the case what could be causing horrendous vibration (out of gear) at higher revs?

 

It was my understanding that I shouldn't be able to over-rev it.

 

If I did use a tacho from the alternator is there any calibration - presumably thats the alternator rpm and I'd have to calculate to get engine rpm?

[ditchcrawler]

I just bought one of these http://www.ebay.co.uk/itm/140938342840?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

[BEngo]

Two part question really;

 

1. How do I measure the revs on a 4LW (how can I fit a rev counter?)

 

2. My engine, whether in or out of gear reaches a point (at unknown revs see 1.) when it vibrates so much it is unusable. Is it possible to rev the engine on an ordinary throttle past where it should go? Should it not be governed so it can't go past this point? It has a 24" propellor of unknown pitch on a 14 ton boat so could it be seriously underpropped?

 

 

 

I realise that I may not have put this in such a way that enables a diagnosis but questions to help arrive at one gratefully received.

 

thanks.

There was a factory fit cable-driven rev counter. You may find one! You may even find the engine bits and a long enough cable. (Oink Oink, flap flap )

 

 

One way to measure the revs may be if you have an alternator with a W terminal. Then all you need is a suitable rev counter, and a hand-held tachometer to do the calibration. VDO, vetus and others do them. The W terminal provides a variable frequency signal to the gauge which then turns that into a needle movement. The hardest part will probably be getting a gauge bit that has the right full scale deflection for your engine speed and the alternator gearing.

 

Another approach it to use a cheapo bicycle computer- Alan Fincher or possibly RLWP (I think) has posted the detail on how, but in essence you put a tiny magnet somewhere convenient on a rotating part, position the detector so it can see the magnet, tell the computer the 'right' wheel size and 1 mph = 1 rpm. Maybe a general Google on "bicycle computer rev counter" would help. Apparently the posher computers display 'cadence', which is pedal rpm to the lycra clad, directly.

 

Depends what you want the revs for- if it's only concerned with investigation for the second question then a hand-held tacho would be enough. They come up second hand quite often at reasonable prices.

 

 

The vibration problem sounds like maybe a mounting issue- any 4 cylinder in-line piston engine will vibrate because there are bits going up and down. This will be made worse if one or more cylinders are not working properly- Does it run evenly with all cylinders firing? If not fix that first. Try slackening the sprayer-to-pump connection on each cylinder in turn. ( Diesel will leak out so have a rag handy) If slackening one connection has no effect then that cylinder is not doing much.

 

If the natural frequency of the engine and its mounting system coincides with a natural vibration that occurs at an engine speed the engine will leap about enthusiastically. Since it does it out of gear it's not a torsional vibration problem, or anything to do with the propeller,or shaft. Have a look at the engine mountings all the way from the feet to the hull. Are they all properly secure, in good order and tight? If you can, try and do this examination with the engine running at a speed just as the vibration is starting to build up.

 

 

The maximum engine speed should limited by the governor and the fuel pump. This speed will be slightly higher out of gear than in gear ( provided you are not over propped) but should be pretty close the engine's design rpm. Unless someone has fitted the wrong sized elements to the fuel pumps, or buggered about with the rack position, then the governor settings and springs would be your first port of call- if the engine is overspeeding.

 

Propcalc is the best bet to assess if the prop you have is well suited to the engine. Such things as desired speed, draught, shape(block coefficient), beam, waterline length all affect the answer. It's free but you'll need to Google for it.

 

Hope that helps.

 

N

[Mike Tee]

I just bought one of these http://www.ebay.co.uk/itm/140938342840?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

So did I, and they work fine.

 

If you want a slow revving one to run off the alternator try these http://www.russellnewbery.com/

They do have a rather attractive logo on them which suits my boat - you may have to apply a small sticker! I suggested this to someone else on this forum a while back, and I believe they got one and were happy.

They are not listed on the website, but were for sale through the RN Register - small annual fee and a colour magazine every now and then which you could leave in your engine room for visitors to peruse.

[Timleech]

There was a factory fit cable-driven rev counter. You may find one! You may even find the engine bits and a long enough cable. (Oink Oink, flap flap )

 

 

One way to measure the revs may be if you have an alternator with a W terminal. Then all you need is a suitable rev counter, and a hand-held tachometer to do the calibration. VDO, vetus and others do them. The W terminal provides a variable frequency signal to the gauge which then turns that into a needle movement. The hardest part will probably be getting a gauge bit that has the right full scale deflection for your engine speed and the alternator gearing.

 

Another approach it to use a cheapo bicycle computer- Alan Fincher or possibly RLWP (I think) has posted the detail on how, but in essence you put a tiny magnet somewhere convenient on a rotating part, position the detector so it can see the magnet, tell the computer the 'right' wheel size and 1 mph = 1 rpm. Maybe a general Google on "bicycle computer rev counter" would help. Apparently the posher computers display 'cadence', which is pedal rpm to the lycra clad, directly.

 

Depends what you want the revs for- if it's only concerned with investigation for the second question then a hand-held tacho would be enough. They come up second hand quite often at reasonable prices.

 

 

The vibration problem sounds like maybe a mounting issue- any 4 cylinder in-line piston engine will vibrate because there are bits going up and down. This will be made worse if one or more cylinders are not working properly- Does it run evenly with all cylinders firing? If not fix that first. Try slackening the sprayer-to-pump connection on each cylinder in turn. ( Diesel will leak out so have a rag handy) If slackening one connection has no effect then that cylinder is not doing much.

 

If the natural frequency of the engine and its mounting system coincides with a natural vibration that occurs at an engine speed the engine will leap about enthusiastically. Since it does it out of gear it's not a torsional vibration problem, or anything to do with the propeller,or shaft. Have a look at the engine mountings all the way from the feet to the hull. Are they all properly secure, in good order and tight? If you can, try and do this examination with the engine running at a speed just as the vibration is starting to build up.

 

 

The maximum engine speed should limited by the governor and the fuel pump. This speed will be slightly higher out of gear than in gear ( provided you are not over propped) but should be pretty close the engine's design rpm. Unless someone has fitted the wrong sized elements to the fuel pumps, or buggered about with the rack position, then the governor settings and springs would be your first port of call- if the engine is overspeeding.

 

Propcalc is the best bet to assess if the prop you have is well suited to the engine. Such things as desired speed, draught, shape(block coefficient), beam, waterline length all affect the answer. It's free but you'll need to Google for it.

 

Hope that helps.

 

N

 

An original tacho drive unit came up on ebay a few months ago,I seem to remember it went for about 50 quid, & that's just the starting point!

 

With a Gardner you don't need to do the injector union slackening bit - just hold or latch down the priming handles on the fuel pump, one at a time, and see whether they all have a similar effect.

 

Tim

[Split Pin]

Fitting a mechanical drive tacho might not be an easy answer even if you can find all the proper bits, the right angle gearbox drive which fits onto the back end of the block takes its drive from a slot in the end of

 

the camshaft,this slot may not be there, which would mean removing the camshaft to machine it,

 

It would seem that Gardner supplied engine built to each purpose, engines destined for vehicles probably had the machined camshaft others did not.

 

Electric tacho here http://www.farmtronics.com/proddetail.php?prod=E04200&cat=115 deep pocket needed

 

also herehttp://isspro.mybigcommerce.com/r85205/ sensors also on this site

 

Assuming your fuel pump has not been seriously messed with then you can get an idea as to the max rpm set by looking at the amount of movement that is available on the throttle cam,

 

Most of it 1700rpm

2/3rds 1500rpm

1/2 or less 1300rpm or lower

 

 

Depending on who calibrated the pump it may be the first part or the last part of the cam if set for less than the whole length, they were done this way to stop people simply repositioning the max rev stop

 

I think it unlikely that you are overreving the engine, generally they get smoother as speed increases, one past the resonant point to which BEngo refers.

 

Is yours fitted on Anti Vibration mounts? if so this may well be the problem,pretty well all the ones around are solid mounted from 2cyl upto 5cyl. not seen anyone with a 6cyl in a norrowboat yet!

 

No doubt that there is one out there somwhere.

 

Steve

Edited July 26, 2013 by Split Pin

[Split Pin]

So did I, and they work fine.

 

If you want a slow revving one to run off the alternator try these http://www.russellnewbery.com/

They do have a rather attractive logo on them which suits my boat - you may have to apply a small sticker! I suggested this to someone else on this forum a while back, and I believe they got one and were happy.

They are not listed on the website, but were for sale through the RN Register - small annual fee and a colour magazine every now and then which you could leave in your engine room for visitors to peruse.

 

The RN ones are I believe sourced from accross the pond at a substantial price. (At least that what someone told me)

 

Steve

[Timleech]

Fitting a mechanical drive tacho might not be an easy answer even if you can find all the proper bits, the right angle gearbox drive which fits onto the back end of the block takes its drive from a slot in the end of

 

the camshaft,this slot may not be there, which would mean removing the camshaft to machine it,

 

It would seem that Gardner supplied engine built to each purpose, engines destined for vehicles probably had the machined camshaft others did not.

 

Electric tacho here http://www.farmtronics.com/proddetail.php?prod=E04200&cat=115 deep pocket needed

 

also herehttp://isspro.mybigcommerce.com/r85205/ sensors also on this site

 

Assuming your fuel pump has not been seriously messed with then you can get an idea as to the max rpm set by looking at the amount of movement that is available on the throttle cam,

 

Most of it 1700rpm

2/3rds 1500rpm

1/2 or less 1300rpm or lower

 

 

Depending on who calibrated the pump it may be the first part or the last part of the cam if set for less than the whole length, they were done this way to stop people simply repositioning the max rev stop

 

I think it unlikely that you are overreving the engine, generally they get smoother as speed increases, one past the resonant point to which BEngo refers.

 

Is yours fitted on Anti Vibration mounts? if so this may well be the problem,pretty well all the ones around are solid mounted from 2cyl upto 5cyl. not seen anyone with a 6cyl in a norrowboat yet!

 

No doubt that there is one out there somwhere.

 

Steve

 

Yes there is one, near here. Silly really.

Edit - There's also the 'Fred II' which has been mentioned in this forum which I believe has a 6LX, even sillier though I believe it was intended for rivers as much as canals. Not a conventional narrowboat, though the hull is narrowboat form.

 

Just remembered, there was an intermediate tacho system which used a little impulse generator on the end of the camshaft, driving an electric display. I've got one of those, but the display casing is completely rotted away. Also needs the slot in the end of the camshaft.

 

Tim

 

The RN ones are I believe sourced from accross the pond at a substantial price. (At least that what someone told me)

 

Steve

 

There is a VDO unit with reasonable full scale (2500rpm, I think), but not easy to find.

Edited July 26, 2013 by Timleech

[Mike Tee]

The RN tacho is around £170 which I think is not bad, considering it was one of the few I could find that covered the low rev range required.

 

Don't know how to do a link within this forum, but look under 'Vintage Eng Forum' - 'Lister' - started on Jan 9th 2013 titled 'Tacho for Lister JP'.

 

They may well be manufactured overseas, but the RN place at Hilmorton import them and hold them as stock - at least they did earlier in the year!

[GUMPY]

The simplest way is to get a tiny tach no calibration and they work

Its digital mind not analogue but will do the job easily.

 

http://www.tinytachuk.com

[mark99]

The simplest way is to get a tiny tach no calibration and they work

Its digital mind not analogue but will do the job easily.

 

http://www.tinytachuk.com

Whats the principle they work on Loddon?

 

Assume they pick up a pulse/echo of fuel?

[GUMPY]

Whats the principle they work on Loddon?

 

Assume they pick up a pulse/echo of fuel?

Transducer on the injector pipe each time the fuel pump fires a pulse the pipe expands and sends a pulse to the unit.

They work exceptionally well just not very traditional.

[The Pipe]

You could also use one of these.

http://www.tinytachuk.com/

 

And while I was searching for Loddon popped it in.

Edited July 28, 2013 by Jim Evans

[Chris Pink]

I think it unlikely that you are overreving the engine, generally they get smoother as speed increases, one past the resonant point to which BEngo refers.

 

Is yours fitted on Anti Vibration mounts? if so this may well be the problem,pretty well all the ones around are solid mounted from 2cyl upto 5cyl. not seen anyone with a 6cyl in a norrowboat yet!

 

No doubt that there is one out there somwhere.

 

Steve

 

These are the mounts. They are all in good condition but they are all on pads of 1/2" rubber. The top piece of material in the front mount pic and the only piece in the rear mount.

 

Could this be the problem? The good news is the shaft is a cardon shaft so it would be (relatively) easy to remove the rubber pads. The beds are fairly substantial C-section, would it be an idea to turn this into box? or put a wedgy bit of wood in the open part of the 'C'?

 

 

Edited July 28, 2013 by Chris Pink

[johnthebridge]

Chris-

ASAP supplies do a 0-3000rpm Faria tacho, driven off the alternator. Dependant on which particular one you want, they're about £60-70. I use one on our boat which has a Volvo Penta running at around 1700rpm max. It works well and has an hour meter on it. I've always found ASAP very helpful and reasonably priced. Usual disclaimers.

[Chris Pink]

How do calibrate it alternator to engine speed?

 

The little digital box mentioned above is £72 (inc) so around the same price and seems easier to set up.

 

I don't know whether I need a tacho to solve my problem, from what Split Pin says it's probably not an over-revving problem.

[johnthebridge]

How do calibrate it alternator to engine speed?

 

The little digital box mentioned above is £72 (inc) so around the same price and seems easier to set up.

 

I don't know whether I need a tacho to solve my problem, from what Split Pin says it's probably not an over-revving problem.

[/

quote]

 

They come with calibrating instructions, and it's quite easy to make the adjustments. I agree that it's not likely to be over-revving with a 4lw. Maybe more a mounting problem? Loose flywheel bolts? Dunno without being there I'm afraid. Sorry.

[GUMPY]

I've been delving in my memory bank and when I first got my JP3 it did a similar thing, after much toing and froing and many miles of cruising a second crack appeared in the engine beds. I couldn't see the first one as it was behind the oil tank.

Ended up having the engine out and the whole beds rebuilt with gussets across the c section, cured the vibration.

Looking at one of your pics I would prefer to see more support under the leg.

 

J

[RLWP]

This picture:

 

 

If you removed the rubber pad, the red leg would foul the mounting plate on the bearers. In fact, I wonder if it does that anyway when the engine is moving

 

Richard

[BEngo]

These are the mounts. They are all in good condition but they are all on pads of 1/2" rubber. The top piece of material in the front mount pic and the only piece in the rear mount.

 

Could this be the problem? The good news is the shaft is a cardon shaft so it would be (relatively) easy to remove the rubber pads. The beds are fairly substantial C-section, would it be an idea to turn this into box? or put a wedgy bit of wood in the open part of the 'C'?

That set up is effectively the engine mounted on tuning forks! In the top picture the C section is not really wide enough - it should be as wide as the piece of rubber. The bolt doesn't show in the bottom one but I suspect that may be the same. The mounting bolts also look as though they are smaller than the hole in the foot so are more easily stretched than the biggest possible ones, and the nuts have a smaller bearing area. This is important because friction between the nuts/bolts and the mountings is one of the ways any vibration is damped out and the nut/bolt/foot combination contributes to the overall stiffness of the engine and mountings.

 

 

If it's been bouncing for a while then I would also not be surprised to find cracks elsewhere, similar to Loddons' description.

 

I would like to see the biggest possible mounting bolts, with washers, some vertical gussets in the C section beneath the mountings, the horizontal steel plate fully welded to the C section and I'd probably replace the rubber with some decent hardwood which will absorb the thump. If not a steel-to-steel mounting would be OK, provided it's tight. Looking at the top pic I think that just lowering the engine will result in contact between the engine mounting web (red diagonal thingy) and the steel add-on That would not be a good idea.

 

As a test try some really tight fitting wooden blocks, with the grain running vertically, wedged in either side of the bolts and see if that makes any improvement. I'd also put some big (repair) washers under the nuts on the mounting bolts and bowse them up as tight as possible.

 

What does the underside of the mounting arrangement look like? If that's also a small bolt in a big hole with no washer there is another opportunity for lost damping.

 

N

Edited July 29, 2013 by BEngo

[Chris Pink]

Well the studding is a fair fit for the hole, 5/8" but i wlll get proper bolts rather than studding. Lose the rubber (substitute with a hardwood packing piece?) and make a welded gusset for the C-section (which is 8mm - strikes me as quite flimsy for that weight of engine. )

 

The engine mount (red piece) won't foul the mounting plate. you can't see from the picture but it stops just short of the mount itself.

[BEngo]

If the current studding is 5/8 and the hole is 5/8 then its fine to fit a 5/8 bolt. I think you are in France?? If so M16 might be easier to get and should fit. It looked to me as though the hole was larger. Sorry. More of a bolt will have the full diameter than studding, which is only the thread core diameter all along. Add the largest diameter 5/8 (M16) washers you can find top and bottom.

 

I still think that if you just remove the rubber then the engine will go down so the red bit is touching the steel insert. I could be wrong- I've been wrong once already to day! However, if you put a 1/2 or even 3/4 piece of hardwood in there the engine won't drop anyway. They tell me that good oak is grown in France so that would do.

 

An 8mm or 10mm gusset either side of the bolts would be excellent. Doesn't look like easy access to weld them in though.

 

N

Edited July 29, 2013 by BEngo

[Chris Pink]

It's not great access but possible. Your post is the plan for the front ones, i've still got a bit of digging to get at the back pair.

 

The steel insert wouldn't foul the mounting on its top face but may foul it to the side (it finishes just forward of the mounting), there's not much clearance but, yes, a nice bit of French oak is the plan.

 

16mm is 5 thou larger so I reckon it will fit (and be a lot cheaper).