oil circulation or just pressure?
oil circulation or just pressure?
(OP)
Im building billet two cylinder engine for half scale dragster.It is built from plain alluminium block.Im wondering if I really need conventional oil pump? Im not sure how much benefit we have from oil circulation in dragrace engine.Isnt just enough to keep oil lines under pressure while running? It is pushrod engine, runs a minute maximum.Im wondering if I pressurise little oil tank and give a constant pressure thru engine lines to my gauge, would it any unexpected problems occur or not?
Thanks for input.
Andrius
Thanks for input.
Andrius





RE: oil circulation or just pressure?
No, it'll just give expected problems.
Cheers
Greg Locock
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RE: oil circulation or just pressure?
Its just one minute hard run...Ok, I could do say quarter galon circulation per minute - it still wouldnt require pump.Would it make sense You think?
Thanks
Andrius
RE: oil circulation or just pressure?
I think it will be difficult to accurately predict oil flow as it with change a lot with temperature and with clearance changes from differential expansion of components.
If I was racing you, I would delay as long as possible during staging.
Regards
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RE: oil circulation or just pressure?
RE: oil circulation or just pressure?
Once through systems were common on radial aircraft engines, although I think they were pumped.
It seems that the weight and complexity would be more than for a conventional pump. The reduction in parasitic power use from the pump might or might not make up for the added weight.
Since it is clear that you are going to try this anyway, despite any advice to the contrary from folks with some significant automotive experience, good luck. Let us know how it works out.
RE: oil circulation or just pressure?
RE: oil circulation or just pressure?
You can do the sums under presumed conditions, but without I would think you would need a large safety factor to cover variables already listed. This is only based on supposition as I do not have data on this.
Another point to consider is that oil pumps vary delivery with engine speed. Your system would be constant flow, or at best 2 step for idle and loaded conditions. This I expect will make a large supply of oil and pressure source necessary.
If you do get delayed while oil is flowing, you may very well run out and do serious damage. Some motor cycles use a chain driven small pump. These should be really easy to adapt.
Regards
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RE: oil circulation or just pressure?
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RE: oil circulation or just pressure?
Lawnmower engines and simple tractor engines do not have oil pumps. They rely entirely on oil-splash lubrication from a "flinger" extending down from the connecting rod. I do not know how they prevent the main and con-rod bearings from blowing up. But, those are very low-performance engines, and they are not designed for long life. (I believe lawnmower engines are designed for a life of around 100 hours running time. In a car with average driving, that's only around 6000 km.)
If the bottom-end of the engine uses entirely rolling-element bearings, you can get away with a lot of things that you couldn't do with a plain-bearing bottom end. This type of design is common in 2-stroke engines, but there are also a lot of scooter and small motorcycle engines that have rolling-element bottom ends. One thing to think about is that the crankshaft has to be a pressed-together design, because there's no other way to put the connecting rod (with its rolling-element bearing ...) onto the crankpin.
If your bearings are designed for pressure lubrication, you COULD store up the oil in a pressure vessel and discharge that into the oil lines, but why? If you got stuck spending longer than usual staging before the race, you're in trouble. The volume and weight of the pressure vessel may be significant, and the oil you pump through the bottom end has to go somewhere.
Personally, for a two-banger, I'd either go with an oil pump, or use a rolling-element bottom end and splash lubrication. Don't forget about the cam-follower lubrication, and how you're going to lubricate the piston pin.
RE: oil circulation or just pressure?
RE: oil circulation or just pressure?
http://en.wikipedia.org/wiki/Gnome_Rotary
http://www.keveney.com/gnome.html
Induction was through the crankcase, intake valve was on the piston & exhaust was on the top of the cylinder. Lubrication was total-loss with castor oil.
RE: oil circulation or just pressure?
In an In-line engine the pistons are all in line with each other when viewed from the end of the crank.
In a "V" engine, the pistons are arranged in a V shape when viewed from the end of the crank.
In an opposed or flat engine, the pistons are opposed to each other when viewed in line from the end of the crank.
There are actually "W" engines, in which the pistons are arranged in the shape of a "W" when viewed in line from the end of the crank.
In a radial engine, the pistons are radially arranged, when viewed in line from the end of the crank.
Wikipedia's page notwithstanding, the fact that the entire crankcase of the Gnome rotates about a fixed crank does not alter the radialosity of the engine.
A rotary engine does not use reciprocating pistons. Examples would be the Wankle or a scroll expander.
RE: oil circulation or just pressure?
In early aircraft engines Rotary and Radial are 2 different configurations.
http://en.wikipedia.org/wiki/Rotary_engine
While most Rotary Engines had their cylinders arranged 'radially' they are not generally referred to as ‘radial’ engines.
Rotary in this context is not the same rotary as Wankel.
I'm afraid you're mistaken on this one.
KENAT, probably the least qualified checker you'll ever meet...
RE: oil circulation or just pressure?
And some AC engines used ball mains if memory serves, and I don't consider 2300 rpm very high.
Since your talking minumal lube, you would need an antifriction bearing. But you said you don't want them?
Then you better find some good grease. How high do you think the torque will be? Maybe 150 lb ft at the most?
RE: oil circulation or just pressure?
Ball bearings are great for outer crank bearings but not always for rods. Many large bore 4-stoke single motorcycle engines use needle bearings on the big end of the rod and they hold up well under some extreme conditions.
Large bore 2-strokes use the same thing and they don't spend most of their time at high RPM.
This is a rod for the Honda XR650 single.
RE: oil circulation or just pressure?
RE: oil circulation or just pressure?
RE: oil circulation or just pressure?
http://ww
RE: oil circulation or just pressure?
Animal engine - 8 HP @ 5000 rpm, 6500 rpm max -
"Die cast performance rod with rod cap dipper"
RE: oil circulation or just pressure?
Windage-by-design, intuitively, would hurt power more than a proper oil pump would draw, though. I wonder how such a test could be run...