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Post by chriso on Nov 11, 2012 17:45:05 GMT
How about a turbine (connected to the drive-shaft) driving an hydraulic fluid around a cyclic flow-path? When in normal use the fluid would be free-flowing but under braking it's flow-path restricted. The clutch could also be by hydraulic connection between the engine shaft and the drive shaft. Small turbines spin way too fast for wooden bearings to handle, and the precise blades are probably not something the crew could manufacture in a week.
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Post by chriso on Nov 11, 2012 20:39:16 GMT
Trak, wouldn't igniting the fuel through compression scorch the cylinder? Or you have a cooling idea to deal with it? Misted water will keep things cool, but it will also prevent auto-ignition. As well as raise the pressure faster, of course.
*edit*
I looked at your post again and have a few questions. So are you going to do a combined injected water system, or a power and cooling stroke type of thing? And why go the Bipolar route rather then something more traditional? Finally, how are you going to keep your spark plug lit during the cooling stroke?
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Post by memeengine on Nov 11, 2012 22:27:07 GMT
Now as to this picture; it’s a 2 stroke with multiple ports 4 intakes and 4 exhausts. the exhaust ports are ¾” and the intake ports ½” that should help with air flow thru the cylinder during the exhaust stroke. The directly opposed pistons on this should give great compression due to the long stroke length... This BIPOLAR design should prevent blowing a cylinder head off of it and the long vacuum stroke should help remove exhaust gases, draw in more cool air and help to keep it running cooler. OK photo not as good as hoped Orange is the piston cylinder; Brown the pistons; Blue is the air intake ports, and yellow the exhaust ports So, just to ensure that I've interpreted your design correctly, you have two pistons working in opposition in the same cylinder? If so, how are you connecting the two pistons to the driveshaft? Or are you using two driveshafts? How are you going to control the piston timing to ensure that they are both at the same point in the cycle? Thinking in more general terms, is it going to be possible to machine the wood to the required tolerances for a two-stroke engine? If I understand the earlier two-stroke model correctly, then the piston acts to seal off the fuel and exhaust ports during the cycle. It would seem to me that would require very tight fitting components to work correctly. Another question would be how would you hold the engine parts together? In conventional metal engines, the major components are bolted together. This allows the engine components to be manufactured separately and then connected around each other at assembly. For example, the piston's cranks are bolted into place around the crankshaft. I suspect that wooden bolts, while possible to make in theory, would not give the strength needed and would be difficult to make small enough to be practical. Gluing the engine together might work but it would make maintenance and adjustments problematic during the prototyping & testing stages.
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Post by trakmec on Nov 12, 2012 7:49:51 GMT
Chris O: “wouldn't igniting the fuel through compression scorch the cylinder?”
Yes. Pressure temperature ignition may scorch the cylinder walls, but I plan on using heavy weight oil to reduce that problem.
Water is a consideration if need to keep things operational. After talking to a fellow mechanic I think the way to cool this and prevent its rapid self destruction is a liberal use of lubricating oil. The oil will burn off during combustion but as long as you’ve got more to replace what you’ve already consumed it will continue to lubricate and reduce the wear on the piston and the cylinders heat. That’s what oils supposed to do right? Except in this engine we won’t worry about it leaking, or burning it. If water was injected it would be at the end of the power stroke, and aimed towards the piston head.
“And why go the Bipolar route rather then something more traditional?”
The BIPOLAR design was to work around the cylinder head pressure issues that I was seeing with a compression ignition. If the detonation pressure was too great it would just move the pistons apart rapidly reducing the internal pressure instead of splitting or shifting a wooden cylinder head. It also made the block much easier to build.
“How are you going to keep your spark plug lit during the cooling stroke?”
The spark is still problematic. The plan is that the ember would be used from a cold start, and once going the engine operation would sustain itself. I hoped by wedging the ignition material whatever it ended up being into the end of that rod it would be somewhat protected from the water vapor, if water injection was needed. That and having a large enough volume compressed that the temperature would be more than sufficient to ignite the fuel and keep the “ember” burning as a backup if needed. Of course there’s a really good chance that the rod will burn up and clog the engine. I am open to suggestions on this part.
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Post by freegan on Nov 12, 2012 8:01:02 GMT
If your lubricant oil is injected with the fuel, would you get compression induced detonation (a la Diesel engine)?
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Post by trakmec on Nov 12, 2012 8:15:33 GMT
memeengine: “So, just to ensure that I've interpreted your design correctly, you have two pistons working in opposition in the same cylinder?”
Yes that’s it; please see my reply to Chris O as to why.
“How are you connecting the two pistons to the driveshaft?”
Originally I was working on the whole wooden cart concept, with each piston rod going to a drive axle on either end of the cart. Currently as just an engine it will be thru two fly wheels on both ends, and a drive belt or chain connecting them, that should maintain the timing, and allow you to take power off of the belt to move whatever the vehicle ends up being. At this point I think it should be a boat! If that’s within the limits of this “myth”.
“Thinking in more general terms, is it going to be possible to machine the wood to the required tolerances for a two-stroke engine? If I understand the earlier two-stroke model correctly, then the piston acts to seal off the fuel and exhaust ports during the cycle. It would seem to me that would require very tight fitting components to work correctly.”
Yes, and no, This is not going to be efficient, but by using heavy weight lubricating oil and planning on it burning off you should be able to handle the loose tolerance you’d get from the wood. Remember that fire pistons work pretty well to maintain pressure and create heat and their made of wood. “How would you hold the engine parts together?”
Cyber’s earlier post led me to believe that adhesives or hardware are acceptable for this construction. I think several long bolts thru key points of the block should work very well to hold it together. As well as allow for disassembly to fine tune as needed
“I suspect that wooden bolts, while possible to make in theory, would not give the strength needed and would be difficult to make small enough to be practical.”
Two plans here, A) if allowed, steel bolts and nuts. B) 1” wooden dowels with wedges, the pistons and the rods are very long and the angle to the flywheel is a slight as I can make it to keep the stress along the grain to a minimum. As it will be compression cross grain on the pins they should hold.
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Post by trakmec on Nov 12, 2012 8:39:49 GMT
Freegan: Normally yes, but the oil will be gravity fed to the cylinder at the bottom of the stroke (actually the outside). Not injected at the same time as the fuel. This with the expected loose tolerances should coat the piston and the walls rather liberally. The heavy coating should make the oil less susceptible to pre ignition then if it were injected as a spray. As for detonation it may require some tweeking with the fuel quantity, and the injected water in order to adjust the cylinder temp. Hopefully the oils ignition temperature will be much higher than the chosen fuel. I’ll have to look at Cyber’s chart to see what the best choices are.
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Post by silverdragon on Nov 12, 2012 9:02:04 GMT
I have considered that, I was thinking Exhaust brake anyway, but engine braking only goes so far, I was thinking the final brake from 1st to stop speeds, 10mph to zero, you cant exactly engine brake THAT part?... without stalling?.... I still suspect that wooden disk brakes would not function repeatedly, but a clutch mechanism that would connect to a paddle wheel in an enclosed cylinder filled with Oil would provide ample braking efficiency, as suggested (sort of) by Freegan....
I was then considering that this could also be linked to a "KERS", Kinetic Energy Recovery System, as in what the F1 cars use, and perhaps be utilised as a power source to give initial zero-to-something acceleration?.... That would be an excellent "Engine brake" system that could harness what would otherwise be lost power?..
But, saying that, We need a system that just works in case of sudden Twonka, ... KERS is all well and good, but that would be a slow system in emergency, we need that tyre-shredding ABS controlled emergency stop for... well.... emergency?...
As I was considering making the Brake system PART of the engine anyway, it was relevant?...
If not, I think I have enough ideas now on the subject to construct "something" viable, so am happy to leave this for future discussion when the power plant has been *theoretically* put to bed?....
I thank you all for indulging with this slight tangent to the discussion... sometimes my mind works at a tangent to reality anyway, but there is the "spark of genius" that often gets surprising results?....
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Post by silverdragon on Nov 12, 2012 9:11:22 GMT
Back ON subject, there are some very exotic "Heavy" woods that can stand a good scorching without too much damage....?... Can we think along the lines of ALLOWING a carbon build up on the cylinder walls to possibly protect the wood of the cylinder block?...
I mean, we all think "It has to be clean" when we look at engine parts...
How about we allow a little dirt as Protection?...
As far as I know, Carbon, Graphite even, can be used as an excellent lubricant and protection for Chains on chain drives, so, think with me here and see what we can get, how about a graphite coating on cylinder walls?...
Graphite is after all Fossilised wood, so we aint wandering too far from Wood construct?....
Or is this too far out the box?
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Post by chriso on Nov 13, 2012 0:52:23 GMT
Don't most oils burn above the 350 mark that wood starts to be damaged at? Maybe one of those exotic woods could handle it?
Silver, Interesting idea with graphite, but their is a problem. I have used the stuff, and although great, any liquid renders it useless. However, if we are allowed graphite, their might be some other stuff that we can do. Graphite can stand up to around 4000 F, and is porous. Could it be used to shield the cylinder walls from the heat somehow? The stuff is fragile, after all it is the main component of pencil lead, but nonetheless able to stand VERY high temperatures.
On a similar vein, I bet we could use solid chunks of graphite where joints are and take care of those lubrication issues that way. If you can keep liquids away from them, should work okay. Though, two stroke might give you trouble with that.
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Post by trakmec on Nov 13, 2012 1:07:38 GMT
Silverdragon: I did some checking on the graphite and was lead towards molybendeum grease, what do you think about using that? It should handle the heat ok. Be easy to obtain and simple to apply.
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Post by freegan on Nov 13, 2012 1:16:45 GMT
Silverdragon: I did some checking on the graphite and was lead towards molybendeum grease, what do you think about using that? It should handle the heat ok. Be easy to obtain and simple to apply. And very damned slippery. The molybdenum molecule resembles a nano-scale ball-bearing. Excellent lubricant but we may need to persuade the purists that it has a place in an all-wooden engine.
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Post by silverdragon on Nov 14, 2012 7:17:06 GMT
...It was the lead in leaded Petrol?... ok, I know the stuff is NOW considered Poison.... but hows about, as this think is a thought process at the moment, we go with that idea, and use the Petrol to carry the graphite into the combustion chamber to replace any that gets worn off by combustion?.... If we do get to produce this vehicle, its not as if we will be doing the entire length of route 66 anyway?...
As for the lubricant, anything that works that well has got to be used...
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Post by alabastersandman on Nov 19, 2012 8:42:15 GMT
Why couldn't water cooling be used? From my understanding, White Oak has closed cells and will hold water just fine. I'm toying with the idea of making my bathroom counter and sink from White Oak, just cause. The flow could be convection fed. I haven't come up with an idea for a radiator yet but I'm sure something could be figured out.
What about plant based oils for lubrication? Linseed oil for example? If they could be kept from igniting they should work pretty good.
Leather would make a good substitute for piston rings, but how about wrapping the piston in leather? This would act as not only a seal, but also to prevent splitting as well as keep the piston at a more stable moisture level, which in turn would prevent excessive expansion and contraction.
Other materials such as rubber (for hoses, seals, etc.) could certainly be used without deviating too much from being made of wood, as rubber is derived from a tree.
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Post by silverdragon on Nov 19, 2012 8:54:07 GMT
White oak, good wood, but there are many other "Iron wood" type woods that are much more resistant... and harder wearing.... ?
My Dad used to work and swear at something called American Hornbeam, according to him, it was evolved to test is saw blades and blunt his chisel's...
I learnt a lot of "Blue" words when I was young when he worked with that stuff....
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Post by chriso on Nov 19, 2012 10:32:23 GMT
Why couldn't water cooling be used? From my understanding, White Oak has closed cells and will hold water just fine. I'm toying with the idea of making my bathroom counter and sink from White Oak, just cause. The flow could be convection fed. I haven't come up with an idea for a radiator yet but I'm sure something could be figured out. What about plant based oils for lubrication? Linseed oil for example? If they could be kept from igniting they should work pretty good. Leather would make a good substitute for piston rings, but how about wrapping the piston in leather? This would act as not only a seal, but also to prevent splitting as well as keep the piston at a more stable moisture level, which in turn would prevent excessive expansion and contraction. Other materials such as rubber (for hoses, seals, etc.) could certainly be used without deviating too much from being made of wood, as rubber is derived from a tree. The reason normal water cooling could not be used is wood doesn't transfer heat very fast. The metal of an engine block is very good at getting the heat that occurs at the cylinder wall to the coolant. Wood on the other hand, is about 50x worse at moving heat. So although water in the cylinder might be able to take the heat off the cylinder walls, water flowing through the engine block would not pick up enough of the heat to keep the cylinder walls from being burnt to a crisp. Thus the abandonment of the traditional coolant design (mostly) and the discussion about in-cylinder cooling. Unless you have some insight?
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Post by chriso on Nov 19, 2012 10:38:39 GMT
Silver, that sounds promising. I believe in general hardwoods ignite higher, and transfer heat quicker, so that would be a good thing to look at.
And I realised I never responded to the lube comments. I agree that if it doesn't foul up (which contrary to what I believed it looks like in this case it doesn't) then graphite would make a great dry lubricant, especially for some of those tiny places that you would otherwise have to pump oil to.
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Post by silverdragon on Nov 19, 2012 10:45:34 GMT
Coolant of the Cylinder.... I have a "crazy" idea, can we have a think on this. Forget conventional....
How about a SIX stroke engine?.... (You may need to think more cylinders to accommodate this...)
You will need a new crankshaft and timing system, of course, and perhaps a re-think on exhaust port openings?...
Use high pressure water spray injection into the cylinder between ignition strokes to cool the cylinder walls?....
The Exhaust may have to go through a scavenger to recover moisture.
Is this in any way viable?...
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Post by chriso on Nov 19, 2012 19:03:24 GMT
Coolant of the Cylinder.... I have a "crazy" idea, can we have a think on this. Forget conventional.... How about a SIX stroke engine?.... (You may need to think more cylinders to accommodate this...) You will need a new crankshaft and timing system, of course, and perhaps a re-think on exhaust port openings?... Use high pressure water spray injection into the cylinder between ignition strokes to cool the cylinder walls?.... The Exhaust may have to go through a scavenger to recover moisture. Is this in any way viable?... Its already been done with a traditional engine, and we discussed such a cycle earlier. Main reason I think injecting water during the main cycle would be better is that the resulting steam would give more power. But, certainty would provide cooling.
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Post by chriso on Nov 20, 2012 3:12:44 GMT
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