Speed wheel and compression advice

[chilligibbon]

Hi, I have an annoying little problem with my speedwheel, jp2 engine, at tick over and just above it stays in position fine but turn up the revs to cruising speed and the wheel vibrates back round to almost tick over again. I can't see any obvious places to tighten to stop this. Any ideas gratefully received.

 

On a slightly different note, compression valves in or out when cruising canals? The previous owner said he never touched the valves and left them screwed in, what are the pro's and cons?

 

Thanks

 

Chris

[RLWP]

On the first, the common solution is to hang a weight on the handwheel with a hook

 

On the second, out for running, in for starting. Does it make a significant difference, probably not. But if you don't use them, why bother having a JP2 - a Beta would be less fuss

 

Richard

[Timleech]

On the first, the common solution is to hang a weight on the handwheel with a hook

 

On the second, out for running, in for starting. Does it make a significant difference, probably not. But if you don't use them, why bother having a JP2 - a Beta would be less fuss

 

Richard

 

Major reason for running on high compression on light loads (chugging along muddy ditches) is that the exhaust will usually be less smoky than on low.

 

Tim

[frangar]

I run with them out even on shallow canals....less stress on engine I reckon....don't notice that the exhaust is any more smokey than running on high. Just screw them out when it's running.

 

If they have never been used they might be a bit carboned up....be prepared for some bits to come out of exhaust...they may take a bit of running to seat properly in the low position too.

 

Cheers

 

Gareth

[chilligibbon]

On the first, the common solution is to hang a weight on the handwheel with a hook

 

On the second, out for running, in for starting. Does it make a significant difference, probably not. But if you don't use them, why bother having a JP2 - a Beta would be less fuss

 

Richard

Like the idea of the weight on a hook, will certainly be trying that, thanks Richard.

 

So far, regarding the compression valves jury is still out. Guess it's a case of trying it and seeing what feels best.

[RLWP]

Opinions differ...

 

The JP4 I am familiar with smokes less on low. Tim will be familiar with many more engines than me

 

If the valves haven't been used in years, they'll probably leak if you try to use them because of a build up of carbon

 

Y'know, my BMC 1.8 is a lovely engine...

 

Richard

[johnthebridge]

Like the idea of the weight on a hook, will certainly be trying that, thanks Richard.

 

So far, regarding the compression valves jury is still out. Guess it's a case of trying it and seeing what feels best.

I had this problem with a Kelvin gearwheel. I just screwed a brass cuphook in the cabin roof, adjacent to the wheel, and hung a short length of small diameter brass chain from it. My wheel had a small finger extension on it which I simply hooked the chain round at the appropriate point to stop it unwinding. Never failed and easy to release should an emergency stop be required. No finger extension? Just thread the chain through the spokes of the wheel and loop both ends back over the hook.

[chilligibbon]

I know the compression screws were used when the boat was surveyed before I bought it in October so hopefully no leakage when I try them when I get back to the boat.

 

Will let you know, and will try both options when out on our first cruise at Easter and see which suits best.

[by'eck]

Opinions differ...

 

The JP4 I am familiar with smokes less on low. Tim will be familiar with many more engines than me

 

If the valves haven't been used in years, they'll probably leak if you try to use them because of a build up of carbon

 

Y'know, my BMC 1.8 is a lovely engine...

 

Richard

 

Very surprised at that statement since the combustion temperatures will be lower on low comp = poorer fuel burn unless the engine is running hard.

 

Most find it the other way around for this very reason. Mine smokes noticeably after idling in river locks when running on low comp, until it warms back up.

[RLWP]

All based on highly scientific methods . I.e. Hanging over the side

 

Richard

[madcat]

Boris remember JP engined locomotives running underground in Hodbarrow Iron Ore mines, I will ask him for details and post on here if I remember.

 

I'm pretty certain he said they were run on high compression all the time but I will check . He's asleep just now and not to be disturbed as he will go straight into grumpy old git mode if woken .

[CaptAWOL]

I have a bow shackle of about 2" to hang on the handle of the speed wheel easily enough to remove and hold whilst operating the wheel

 

As for compression valves mine out for running on the JP2 as it loads up to about 800 rpm of 1000 rpm max, many JP3's leave them in due to lack of load and the carbon build up which can result in the valves not seating in and causing starting problem's

[1-Cylinder Wonder]

Run on high compression always. On canals in a pleasure boat you will never load the engine up enough to merit running on low. Running on low will encourage carbon build up round the valves (inlet/outlet not just high low) and can cause damage long term. Running on high doesn't reduce your boating or vintage prowess.

 

John

[frangar]

Run on high compression always. On canals in a pleasure boat you will never load the engine up enough to merit running on low. Running on low will encourage carbon build up round the valves (inlet/outlet not just high low) and can cause damage long term. Running on high doesn't reduce your boating or vintage prowess.

 

John

Well having always used my changeover valves and run on low on canals since I brought the boat over 20 years ago I can safely say when we have had to remove the heads (due to a dropped liner and an a "Vintage specialist" who forgot to use a torque wrench!) that there has been no excess carbon around the valves at all. What damage do you think it can cause? As I see it running on low puts less stress on the crank & bearings. It also means the engine will won't have stuck changeover valves when you do come to need them.

 

Cheers

 

Gareth

[Proper Job]

I run Ocelots JP3 on high compression on canals as it's very lightly loaded.

 

Low compression when running in deep water (rivers) and high engine loads.

 

As far as a creeping speed wheel, I hang a windlass from it. It saves leaving it on the roof to be swept off by low hanging trees etc

[RLWP]

I was discussing your dangling windlass the other day

 

Richard

[Proper Job]

I was discussing your dangling windlass the other day

 

Richard

 

[chilligibbon]

Hi all,

 

While the debate on the compression valves seems as if it will roll on forever, I'm pleased to say the windlass on the speed wheel works a treat and I am now looking forward to an Easter cruise without a block of wood jammed in to hold it in place!

 

Thanks again for all the tips

 

Chris

[RLWP]

The best solutions are always simple

 

Richard

[Proper Job]

The best solutions are always simple

 

Richard

 

I resemble that remark

 

[MtB]

Ok I have one of those basic questions that I've never seen addressed on CWF.

 

Why does the JP need high and low compression settings when other diesel engines don't?

 

Thanks.

 

MtB

[Proper Job]

High compression makes for easy starting and clean combustion on low loads

 

Low compression reduces the bearing loads etc when running at high speeds and high loads

 

IIRC the difference is 16:1 and 20:1

 

I can vouch for the combustion as Ocelots JP will start to smoke a bit when on low comp and low load. Low compression running a high river speeds does feel smoother with less vibration.

 

............... anyway, J & K series kelvins have low and high comp'. Although you use it the other way round

[by'eck]

Ok I have one of those basic questions that I've never seen addressed on CWF.

 

Why does the JP need high and low compression settings when other diesel engines don't?

 

Thanks.

 

MtB

 

The JP series designed in the late 1920's were Lister's first diesel engines, slightly preceeding even the basic CS (cold start) industrial series. Their design offered many challenges given the need to handle the much higher bearing loads the necessary high compression ratio dictated. They based the design on their proven L series petrol engines but took the bore down to 4.5 inches. To further reduce bottom end loads they designed an overhead valve head (their first) with an extra combustion area that could be shut off with a valve to provide enough compression for reliable cold starting, but then opened once running to reduce bearing loads. This system provided compression ratio's of 19:1 and 15:1 respectively. Remember at the time of the design they were venturing into unknown territory so had no other designs to guide them although many others were developing cold start four stroke diesels at the same time. Since this system worked admirably though they seem to have stuck with it, even including on the much later Freedom (FR) series, albeit with neat over-centre levers to perform the changeover. Imagine having to do that on a six by twisting knobs

 

 

Several decades after the first JP when the higher revving JK series were introduced it was found that reliable starting and running could be achieved with a fixed compression ratio of 17.5:1. The holes in the head where the change over valves would have sat were blanked off with a screw in insert.

Edited April 17, 2014 by by'eck

[Timleech]

 

The JP series designed in the late 1920's were Lister's first diesel engines, slightly preceeding even the basic CS (cold start) industrial series. Their design offered many challenges given the need to handle the much higher bearing loads the necessary high compression ratio dictated. They based the design on their proven L series petrol engines but took the bore down to 4.5 inches. To further reduce bottom end loads they designed an overhead valve head (their first) with an extra combustion area that could be shut off with a valve to provide enough compression for reliable cold starting, but then opened once running to reduce bearing loads. This system provided compression ratio's of 19:1 and 15:1 respectively. Remember at the time of the design they were venturing into unknown territory so had no other designs to guide them although many others were developing cold start four stroke diesels at the same time. Since this system worked admirably though they seem to have stuck with it, even including on the much later Freedom (FR) series.

 

Several decades after the first JP when the higher revving JK series were introduced it was found that reliable starting and running could be achieved with a fixed compression ratio of 17.5:1. The holes in the head where the change over valves would have sat were blanked off with a screw in insert.

 

Not forgetting that hand start was the norm for engines of this size, really until after WWII I suppose, the dual compression arrangement made that eminently practical.

Other makers used other dodges, commonest being starting wicks and oil cups for introducing a measured amount of oil to the intakes. The oil had the same effect of temporarily raising the compression ratio, though in this case only until the engine fired a few times. Listers used the same dodge in some of their later. smaller engines.

For some engines, impromptu methods were often used such as holding flaming rags over the air intake. Gardners had a system for increasing the inlet valve tappet clearance when starting, this also slightly raises the effective compression ratio.

By the time the JK came out, electric start had become the norm.

 

Tim

[MtB]

Thank you for the explanations. Much appreciated!

 

MtB