Reducing the volume of an engine

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trade4us2, Nov 9, 6:26am
Let's say that I have an engine with four cylinders that no longer needs to supply much power, and I want it to just idle, to save fuel.
What are the options? Use one cylinder, reduce the diameter of the cylinder, or reduce the stroke?
The last two options would be very very difficult. It has a nice heavy flywheel!

bill-robinson, Nov 9, 6:31am
you got it, reduce bore or stroke or combination of both

tony9, Nov 9, 6:33am
Get a smaller or more suitable engine.

bwg11, Nov 9, 6:38am
Why not just remove 2 or 3 pistons and rods, along with the appropriate push rods. You will need to attend to the crankshaft oil-ways at the removed big-ends.

skiff1, Nov 9, 6:51am
use a gear box, and let it lug?

trade4us2, Nov 9, 7:09am
Actually this is a serious problem that needs an answer.
I like the idea of using just one piston and removing three rods.
Stroke is 1200mm, each cylinder is 320 litres.
Its speed is 15 rpm. I don't suppose it will matter if it's a bit off balance.

tony9, Nov 9, 7:20am
If you remove 3 rods you will need to block the oil holes in the big end journals. Also balance will be way out as the crankshaft balance will expect 4 con rods.

brigette6, Nov 9, 7:24am
What type of engine is 1280 litres? must be a ship or something?

tony9, Nov 9, 7:28am
Suggest you contact Sulzer direct.

tintop, Nov 9, 7:38am
lol !

trade4us2, Nov 9, 7:38am
Just a big pump that doesn't pump anything now.

tintop, Nov 9, 7:41am
At the other end of the size scale, MG removed rods and pistons on one of their record breaking cars to get below 750 cc.

tintop, Nov 9, 7:44am
To my mind the easiest path is to go to a single cylinder, plug oilways, bolt on counterweights to the non piston crank pins.

How many main bearings ?

tweake, Nov 9, 7:46am
i assume engine that size is diesel. so you would also have fueling system to contend with.
also i would assume its only going to be running just for show (as it no longer pumps anything). theres the question of how safe it would be to those viewing it and wouldn't they want to see it running in its normal state ? balance issues are bad enough with small engines, i would hate to see what balance issues are like with it missing a few pistons of that size.

trade4us2, Nov 9, 7:50am
The flywheel is over 16 tonnes. Do you think counterweights would be needed?

tintop, Nov 9, 7:59am
:) At 15 rpm, that's 4 seconds to go round once!, one firing stroke every 8 seconds. Going to be very impressive.

At that sort of speed I don't think balance will be a big issue.

But how many main bearings ?

trade4us2, Nov 9, 8:10am
I don't know anything about the bearings. It looks very scary to me!
https://www.youtube.com/watch?v=-odmLQxRlmM

tintop, Nov 9, 8:20am
A steam engine ?

apollo11, Nov 9, 8:26am
Could you hook up an electric motor to give the appearance of functionality? Failing that, could you find a use for the output, ie driving a large generator and selling the power? Or use the power generated to heat water or something? It's kinda cool, It would be a shame to molest it.

trade4us2, Nov 9, 8:30am
There used to be an electric motor driving it. It runs on coal, but it's a full time job shovelling in the coal, and it doesn't need all that pressure now that it's not pumping the entire water supply for Auckland.
How about we have a solar panel on the roof to drive the electric motor? That would not generate any CO2 and would save the planet a tiny bit!

gamefisher, Nov 9, 8:32am
Just fuel one cylinder and bypass the rest.

tintop, Nov 9, 8:41am
Run on compressed air ?

It would be more efficient that raising steam in a boiler.

trade4us2, Nov 9, 8:45am
They could use a steam engine to compress the air! Brilliant!

tintop, Nov 9, 8:59am
No - Use a portable diesel powered air compressor.

And youmay need at least two of the cylinders, one on each side otherwise with a single you will have a dead spot at each end of the piston stroke and may not be able to restart if the pump happens to stop at that point on closedown. ( Depending on the configuration of the various connecting rods and crank pins.

Thats why steam loco crank pins are offset by 90/270 degrees on two cylinder engines.

gpg58, Nov 9, 9:07am
+1

and open valves on other 3 if clearance to pistons is ok. Probably be better to run on 2 cylinders though.