Moving water....

[kiwiSteve]

Hi...having a few problems working out how to split the saltwater out line so 1/2 the water can be sent through the reduction box and the other sent to the exhaust header... the reduction box outlet can also be directed through the exhaust header and out to sea... I dont think it matters what direction the water travels through the reduction for cooling. I'v upgraded to a 3/4" WS37 fynspray so there should be heaps of water flow, (maybe (?))

 

Edited January 30 by kiwiSteve
photo update

[Tony Brooks]

You seem to have a non-standard setup, usually the raw water circuit is all in series. Typically, raw water inlet > reduction box > water pump > heat exchanger core > XXX > exhaust injection.

 

XXX - In all the systems I have seen, the outlet of the heat exchanger goes through the exhaust manifold, but yours looks different.

 

However, doing it as above has joints in the suction side of the raw water system, so I used to pipe it sea inlet > pump > rest of the system in series > exhaust.

 

I think that your exhaust manifold is cooled by the coolant with the circuit is parallel with the engine, I think that might encourage overheating at high speeds and powers. If the manifold is a light alloy casting, this might be an anti-corrosion measure. If it works, then don't try to fix it.

 

If you want to split the flow then I think you need a couple of full flow valves so you can balance the flow although if the pump is large enough you might not need any valves.

 

 

Edited to add: on our 2.2s we used 3/4" pipe for the raw water circuits and your engine is over 3 litres, so I would not go smaller than 3/4 pipe.

Edited January 30 by Tony Brooks

[kiwiSteve]

Thanks Tony that helps a lot....

[kiwiSteve]

 

Edited January 30 by kiwiSteve

[Tony Brooks]

I think that should do, although I am a little uneasy about the need to split the flow for what I suspect is a sea or river boat, where prolonged high speed running is probably more common than on UK inland waterways. The engine will be safe, so suck it and see if the reduction bx gets really hot in use.

[GUMPY]

Just plumb them in series like everyone else does.

It's done that way for a reason 🤔

[kiwiSteve]

12 hours ago, GUMPY said:

Just plumb them in series like everyone else does.

It's done that way for a reason 🤔

The sea water side is on 3/4" for the best flow to the heat exchanger, wouldn't dragging water through a 1/2" pipe 1.2meters away from the pump slow the flow considerably... The engine is on a closed circuit including the manifold so the heat exchanger will need a good fast flow of cooling water to cope. ?? the problem is its a new build so nothing has been tried or tested, theres definitely going to be a few adjustments as we go for sure...

12 hours ago, Tony Brooks said:

I am a little uneasy about the need to split the flow for what I suspect is a sea or river boat, where prolonged high speed running is probably more common than on UK inland waterways. The engine will be safe, so suck it and see if the reduction bx gets really hot in use.

we are only splitting the flow out of the cold water exit of the heat exchanger and that normally just goes out the exhaust to sea, I am just looking at a way to send cold sea water through the reduction and out to sea via a 1/2" pipe to the header pipe connection.. The idea to split it is so there's enough water flow to cool the exhaust gases and allow the heat exchanger the water flow volume it will need to cool the closed circuit system I am using  

Edited January 31 by kiwiSteve

[kiwiSteve]

Edited January 31 by kiwiSteve

[Tony Brooks]

42 minutes ago, kiwiSteve said:

 

That is how all such systems I have seen have been done. As you want to do something different, I can't really comment because I have no experience of it. It is a suck it and see situation. For a while, you just need to keep an eye on the engine temperature and reductio box temperature. The engine should be easy from it's own temperature gage, the reduction box less so, AND I have no idea about its maximum operating temperature.

 

I really can't add anything to what I have already said, I suggest you consult a local engineer because local practice may differ.

 

[GUMPY]

2 hours ago, kiwiSteve said:

Yes 

The reduction box needs cold water whereas the engine can cope with the slightly raised temperature.

Are you sure the pipes on the reduction box are for water and are not oil pipes to be fitted to a heat exchanger like this?

 

 

 

That is a really a hybrid install that uses a skin tank as well, it was later converted to full HE cooling

Edited January 31 by GUMPY

[Tony Brooks]

42 minutes ago, GUMPY said:

Yes 

The gearbox needs cold water whereas the engine can cope with the slightly raised temperature.

Are you sure the pipes on the gearbox are for water and are not oil pipes to be fitted to a heat exchanger like this?

 

 

 

 

That is a really a hybrid install that uses a skin tank as well, it was later converted to full HE cooling

 

The OP's boat does NOT need gearbox cooling because it is a mechanical box, but it is provided with rudimentary cooling for the REDUCTION box. As a 3.x litre engine is not very likely to be for use on a canal, plus the OP's location we guess it is a sea boat that may run at high powers and speed for long periods, so I would be reluctant to compromise the reduction box cooling.

 

The reduction box is bolted to the gearbox, but is a separate item.

[GUMPY]

10 minutes ago, Tony Brooks said:

 

The OP's boat does NOT need gearbox cooling because it is a mechanical box, but it is provided with rudimentary cooling for the REDUCTION box. As a 3.x litre engine is not very likely to be for use on a canal, plus the OP's location we guess it is a sea boat that may run at high powers and speed for long periods, so I would be reluctant to compromise the reduction box cooling.

 

The reduction box is bolted to the gearbox, but is a separate item.

 

Semantics!

Gear box / reduction box doesn't matter cooling  principle is the same. 

i.e. removing heat by using cold water.

 

Edited January 31 by GUMPY

[kiwiSteve]

1 hour ago, Tony Brooks said:

 

That is how all such systems I have seen have been done. As you want to do something different, I can't really comment because I have no experience of it. It is a suck it and see situation. For a while, you just need to keep an eye on the engine temperature and reductio box temperature. The engine should be easy from it's own temperature gage, the reduction box less so, AND I have no idea about its maximum operating temperature.

 

I really can't add anything to what I have already said, I suggest you consult a local engineer because local practice may differ.

 

I think most of you guys are using hydraulic gearboxes, this is just a reduction box on the end of a factory BMC Commodore manual reversing gearbox with a 2:1 reduction

 

[Tony Brooks]

10 minutes ago, kiwiSteve said:

I think most of you guys are using hydraulic gearboxes, this is just a reduction box on the end of a factory BMC Commodore manual reversing gearbox with a 2:1 reduction

 

 

We operated a number of your type of gearbox coupled to BMC 2.2 diesels on the hire fleet in the very late 60s and early 70s, so please don't quote my reply with this sort of comment. It would probably be a valid comment if you had quoted Gumpy. I know exactly what is inside that gearbox and the reduction box.

[David Mack]

So is there a water jacket within the reduction box casing?

And why does the reduction box need cooling if the gearbox does not?

Edited January 31 by David Mack

[Tony Brooks]

28 minutes ago, David Mack said:

So is there a water jacket within the reduction box casing?

And why does the reduction box need cooling if the gearbox does not?

 

It is not a water jacket, it is a bow of copper pipe immersed in the oil and below the gears - hence my earlier description of it being "rudimentary".

 

I have no idea why BMC/Parsons thought it needed oil cooling and I very much doubt it does for typical UK canal use, but the oil capacity is not that great and several hours at high speed whilst at sea may well boil the oil due to the constant churning.

 

To add, when in ahead a big drum with the reverse gears inside it plus the input and output shaft rotate as one big mass, so there is probably not much oil churning. When in reverse the gears do spin and if one insisted on running for hours at high sped in astern it would need cooling and would probably wear out because of poor lubrication. In neutral there is very little load, so far less heating effect.

More info that may be useful to the OP, but off-topic.

 

The big drum containing the reverse gear and ahead clutch is held together with a number of long bolts. These bolts seem to eventually snap. From new hey are fitted with the bolt head closest to the engine and the nuts closest to the back of the gearbox. If a bolt snaps and start to work out the head can jamb on the crude oil pump mounted on the gearbox front plate so you have to take the box off to extract that bolt.

 

We found that the boxes worked perfectly well with one snapped bolt so we reversed all of those on the hire fleet so the broken bolt end and nut drops into the bottom of the box, well away from danger, and it is usually possible to take the rest of the bolt out via the rectangular cover. This saved taking the gearbox off at the time, so probably pls point when at sea.

Edited January 31 by Tony Brooks

[kiwiSteve]

7 hours ago, Tony Brooks said:

 

 It would probably be a valid comment if you had quoted Gumpy. I know exactly what is inside that gearbox and the reduction box.

I'm sure you do, thats why I came here hoping you could help and I thought I was quoting "grumpy" i just did it wrongly, my apologies 

[magnetman]

If cooling is critical might it be worth having a small sea cock and an electric Jabsco pump to shove water through the reduction gear and dispose of it overboard via a skin fitting? 

 

I imagine full power use is more likely to happen in open clean water so one could choose whether or not to use the coolant circuit. Presumably there is battery charging via alternator so the power requirements would be dealt with. 

 

On one of my Boats which is a twin screw custom made steel trawler yot the gearboxes (handed pair of PRM Deltas) are cooled by small dedicated keel cooler boxes on the hull sides unrelated to the engine coolant circuits which are on the bottom of the hull. 

 

I do think it is worth considering separating the two circuits if the intention is to use high engine power output settings for a sustained time. 

 

My Boat was made to survive the nuclear wars which is a bit ridiculous but there we are such is life. 

 

Edited January 31 by magnetman
typo

[kiwiSteve]

I use forums as a way of learning as I go, Ive been in the boating scene all my life, Ive fished them for a living used them as transportation, depended on them and love them dearly...

 

a simple statement like

 

"We operated a number of your type of gearbox coupled to BMC 2.2 diesels on the hire fleet in the very late 60s and early 70s, I know exactly what is inside that gearbox and the reduction box. 

it is a bow of copper pipe immersed in the oil and below the gears - hence my earlier description of it being "rudimentary".

 

and...

 

I have no idea why BMC/Parsons thought it needed oil cooling and I very much doubt it does for typical UK canal use, but the oil capacity is not that great and several hours at high speed whilst at sea may well boil the oil due to the constant churning.

 

tells me more than I have been able to pick up anywhere so I thank you for that anyway Tony

 

my problem was the wrong way in which I asked the question.. I should have asked if anyone could tell me why I need water cooling to my reduction box on my factory BMC gearbox

17 minutes ago, magnetman said:

If cooling is critical might it be worth having a small sea cock and an electric Jabsco pump to shove water through the reduction gear and dispose of it overboard via a skin fitting? 

 

I imagine full power use is more likely to happen in open clean water so one could choose whether or not to use the coolant circuit. Presumably there is battery charging via alternator so the power requirements would be dealt with. 

 

On one of my Boats which is a twin screw custom made steel trawler yot the gearboxes (handed pair of PRM Deltas) are cooled by small dedicated keel cooler boxes on the hull sides unrelated to the engine coolant circuits which are on the bottom of the hull. 

 

I do think it is worth considering separating the two circuits if the intention is to use high engine power output settings for a sustained time. 

 

My Boat was made to survive the nuclear wars which is a bit ridiculous but there we are such is life. 

 

I thought of this also... my mate has jacked up a pully on the drive shaft which drives a wee pump when the shaft turns whilst in gear

 

My engine has just been reconditioned so will only be running at 1200 rpm for the first 50hrs anyway and only ever cruses at 1800 rpm on a long day, the book says it can run for shorter periods up to 2100 rpm but we are never in that much hurry. Half the funs getting there...

Edited January 31 by kiwiSteve

[Tony Brooks]

14 minutes ago, kiwiSteve said:

I'm sure you do, thats why I came here hoping you could help and I thought I was quoting "grumpy" i just did it wrongly, my apologies 

 

Apology more than accepted, it is all too easy to make that sort of cock-up.

 

Personally, i think that you can safely ignore the electric pump idea. I am not sure the writer knows what you actually have.

 

Having looked up the impeller dimensions I think it will have far more output than the pump fitted on our 2.2, so doing what you suggest will probably work, I just can't be sure, but a good long sea trial at high power should prove it one way or another.

 

I would urge you to take the cover off the top of the gearbox and look at the back of the drum where the toggle levers are. I hope you just see a ring of bolt heads, but if you see nuts then think about reversing the blots and check hem for wear caused by the ahead clutch plates.

 

 

 

[kiwiSteve]

anyway... I'm going to try it like this for a spell, so will see how I get on and let you guys that care know

 

thanks for your help

 

 

[magnetman]

39 minutes ago, Tony Brooks said:

 

 

Personally, i think that you can safely ignore the electric pump idea. I am not sure the writer knows what you actually have.

 

 

I do know exactly what the OP has but I can understand why you think I don't. 

 

For some reason the manufacturer has decided that the reduction box needs liquid cooling. Maybe it doesn't but depending on usage it seems to me that having a system which allows cold water to flow through it might be worthy of consideration. 

 

i would have an electric pump rather than belt. 

Reason: If the engine is being run under high loading the belt is more at risk. If you lose the belt you have no engine. If the pump(s) are operated from the battery you get some extra time before the engine overheats and becomes unusable. 

 

This also requires DC engine coolant circulation pumps and it depends on what you are doing as to whether putting a new belt on is easy at the time. 

[Tony Brooks]

7 minutes ago, magnetman said:

I do know exactly what the OP has but I can understand why you think I don't. 

 

For some reason the manufacturer has decided that the reduction box needs liquid cooling. Maybe it doesn't but depending on usage it seems to me that having a system which allows cold water to flow through it might be worthy of consideration. 

 

i would have an electric pump rather than belt. 

Reason: If the engine is being run under high loading the belt is more at risk. If you lose the belt you have no engine. If the pump(s) are operated from the battery you get some extra time before the engine overheats and becomes unusable. 

 

This also requires DC engine coolant circulation pumps and it depends on what you are doing as to whether putting a new belt on is easy at the time. 

 

At present the pump being used is the same one that is used for engine cooling, If that failed the engine would overheat before any damage was done to the reduction box. The exhaust note would alert the OP to the failure, then, if he was worried about it, a temperature switch on the exhaust header would warn him, and finally the engine temperature gauge/buzzer. In my view, and it is a personal view, your idea adds more complication and potential failure points.

[GUMPY]

1 hour ago, kiwiSteve said:

anyway... I'm going to try it like this for a spell, so will see how I get on and let you guys that care know

 

thanks for your help

 

 

How will warm water and it will be warm effectively cool the reduction box?

 

[kiwiSteve]

2 hours ago, GUMPY said:

How will warm water and it will be warm effectively cool the reduction box?

 

Good question...yeah i thought about this to and I am under the impression that moving water is very effective at absorbing heat as it goes past and we are only trying to cool the drive not chill it below working temperature... Im working on the idea that even warm water will be moving fast enough to draw any excess heat leaving the reduction hot enough to get rid of any condensation that builds up inside and to keep the viscosity at the correct level for best operation, warm but not hot but also not to cold

 

I guess I will find out whether it will cool enough as we go, I can add a device to attain this information to keep an eye on things anyway

 

 

Edited January 31 by kiwiSteve