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Post by chriso on Nov 4, 2012 21:44:51 GMT
Well, under those conditions, I think a hot bulb engine would definitely be the best possible solution. Rocks are everywhere. For start-up, I suspect an auxiliary port holding a burning ember of some sort would be necessary. In fact, this is how some early hot bulb engines started. I got temps of around 800 degrees for burning embers off a google search. And as that is well above the 500 some autoignition point of gasoline, you could roll up a piece of paper tightly and stick it in for you starting source. Heck, if your not allowed rocks you could run the thing this way! On cooling, engine block coolant channels probably would not work. Wood just transfers heat too slow. You would need something slightly more active. I would suggest that a extra cycle, a "cooling cycle," be added to the system that inserts water and allows evaporation to remove heat. Any cooling whatsoever in the bulb cavity would, unfortunately, severely impact engine performance, and so that segment should be designed to be easy to make and just replaced periodically, unless someone has some insight into how to cool one without affecting performance. On the subject of the expansion of wet wood, wouldn't the expansion not make the cylinder smaller, but make it bigger in this case? And cyber, check out hot bulb engine on Wikipedia. Think it really would be worth looking into as a viable engine, because you don't need a fancy fuel pump and you don't need electronic ignition. More clarification please, with this “green engine” and the allowance of electronics and such are we allowing any and all kinds of wood construction such as laminates, and plywood? Or is it to be a big machined block of hard wood? *Note to self, when replying make sure it is the 'reply' button you press and not the 'edit post' one...* Good question. My thinking is to treat this as if you are in the middle of nowhere with a car that lacks an engine (yet for some strange reason you do have fuel lying around...maybe gas bottles for a camping stove. You have something or someone you need to move as quickly as possible to another location - say an injured friend, or the plans for the latest superweapon you need to give to the Rebels so they can send a farm-boy out to destroy it* You have tools and plenty of wood but nothing else to work with. In this situation could you fashion an engine out of wood? Or rather what would it take to make a working engine out of wood? (*OK, so I left 'believable' three exits back...just go with it  ) |
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Post by trakmec on Nov 4, 2012 22:03:13 GMT
MASSIVE suspension of disbeleif my Liege, but as you will
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Post by chriso on Nov 4, 2012 23:15:54 GMT
well, let me rephrase then. The whole idea is silly, but if you really could not tolerate electronic ignition, that would be (In my opinion) the way to go.
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Post by silverdragon on Nov 5, 2012 7:13:33 GMT
"Flash" of inspiration.....
Ok, this is "Out there", but worth some think time please....
Do all cylinders in an ICE engine HAVE to be in one close proximity block?....
Could you separate them with a long enough crank shaft to allow each cylinder to be immersed in a bath of water to help cooling........
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Post by freegan on Nov 5, 2012 8:13:10 GMT
you could roll up a piece of paper tightly and stick it in for you starting source. What's wrong with a stick of charcoal? |
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Post by chriso on Nov 5, 2012 10:40:31 GMT
Nothing. That should work fine. Did you mention it and I missed it?
I just chose paper because it seemed easier to light.
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Post by freegan on Nov 5, 2012 12:17:27 GMT
Did you mention it and I missed it? Not at all. I just thought that it would be a little more in keeping with the wood theme ... from a purist point of view. |
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Post by trakmec on Nov 5, 2012 14:56:19 GMT
Chris O: Sorry bout that! The suspension of disbelief comment was for Cyber’s comment not yours but as it posted after yours it may have appeared a bit snarky.
As to the “hot rock” glow plug I think charcoal, or coal would be best, and agree that an exhaust cooling and cleaning stroke might be useful although it might add some complexity.
I was thinking of something like this setup for the more primitive all wood engine. Basically this would be a two stroke for simplicity.
Use to large pieces of hardwood say at least 12” in diameter and 2’ long with a 3” to 4” hole bored 1’ down the center of the long axis. That would be the cylinder.
The piston and piston rod would connect directly to the drive wheel; think sort of like a steam locomotive crank. Place one piston cylinder on each side of the drive wheel(s). The cylinder head of this set up would be connected to the vehicle in such a way as to allow it to move up and down a few degrees and keep the cylinder bore, piston rod, and wheel crank all lined up. Thus making the wheel and axle act as a crank shaft would in a normal engine.
For now let’s give the piston an 8” stroke so at that distance from the internal end of the cylinder head drill both the exhaust ports into the wood, and the feed for your water coolant.
Now I am inclined to inject water every few strokes but not entirely sure how to do it. What do you think of this so far?
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Post by chriso on Nov 5, 2012 18:11:53 GMT
No problem. It did appear a bit snarky, but don't worry: these things happen on a message board, and I certainty don't hold it against you.
I don't know about allowing the cylinder itself to move, as that would by necessity mean the feed-pipes would have to flex, a tricky process for wooden pipes. I would recommend just going the traditional route instead.
I have been drawing inspiration heavily from old tractors, and have been thinking along the lines you are talking about. What I was thinking of is something with approximately the dimensions you are talking about, that was 6 stroke (yes, six) and drove a flywheel, rather than a wheel, to allow smoother operation, and to allow you to hook it up to whatever gearbox this thing has. The extra two strokes after each cycle would be for the cooling cycle, and would cool down the cylinder walls from the water flashing to steam. I don't think inserting water every few strokes is a good idea, as that requires some sort of mechanical counter, and adds complexity, when you could just do it each time and reduce the water introduced. The Two stroke cycle you suggested, if you could modify it with a coolant stroke, would probably be a better idea, however you will still need at least one valve or port that closes to shut off the bulb cavity during the cooling stroke, or you risk damping your heat source and putting out your charcoal.
As for actually getting the water where it is needed, I think that a "duel carburetor" system, in which a valve keeps the water section closed most of the time but at one point opens it and closes the fuel section, should work fairly well. But, as I said earlier, really don't know enough about engines to say for sure.
So, I agree with the dimensions, and the two-stroke cycle, but think having the cooling stroke as part of the cycle itself is a better idea than doing it every few strokes, and believe that moving the piston around during the stroke will cause excessive fatigue in the feed lines.
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Post by Cybermortis on Nov 6, 2012 17:04:44 GMT
Before we go too far I think we need to recap, in order to turn the original idea into something that could be tested on the show.
This needs to be something that can be filmed and tested in 7-10 days - the exact amount of time given for filming varies depending on who you ask. The higher figure seems to come from Jamie, but I'm guessing that as a producers Adam and Jamie have less time per day for filming than the build team. Related to this is that they don't want to effectively turn the show over to experts, but have the cast directly involved in all stages of testing and building where possible*.
Both of these factors mean that any engine design can't be too complex or require too much technical knowledge. It also means that we have to boil the idea down to the barest parts, so they don't waste time trying to test or build things they don't need to.
Although this was called 'Wooden Car' I think we should eliminate the car as a whole and just concentrate on the engine. I'm going to say that just about everything on a car could be made from wood alone, if you have the time and skills to design and build those things correctly - meaning that, say, making a working breaking system would be a matter of trial and error rather than a questionable prospect**. So lets deal purely with the engine without considering other aspects.
There are two basic ways to go here. One is to assume that the engine you are replacing has seized up. But you can scavenge some of the smaller electrical parts from it. Basically you are trying to make a conventional ICE engine using wood. (As I recall someone on Discovery asked if you could make a piston from wood, so this is a variation/continuation of this).
The second way would be to assume that most or all of the electrical is badly damaged, forcing you to try and create the entire engine out of wood alone.
Both of these have merits I think, and could be tested in small scale to see which is the more practical way to go for a 'full sized' engine. They could try building small scale versions of all types and put them in a small RC car to see how they fare.
The fuel tank and fuel lines should, I think, remain as they would be for a normal engine - in other words those parts of the system remain as they were. If nothing else safety has to be considered, and conventional fuel tanks and lines are a known quantity where as tanks/lines made from wood could prove dangerous.
To keep the testing as quick and simple as possible I think the simplest thing to do is get an old Go-Cart and simply remove the original engine and replace it with their own design. This should give something large enough to make for good TV, while not so large it would take too long to build.
(*Having said that, this would be an opportunity to get Jessie Combs back on the show if they feel they do need an expert to be more closely involved.)
(**They could always cut the idea into parts, trying to make wooden brakes and/or wooden gears ect in later episodes. If they do manage to make a wooden engine then they could later put all the parts together to make the 'Wooden Car'. So in essence this would be three possible ideas in one.)
Thoughts?
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Post by chriso on Nov 6, 2012 18:35:23 GMT
Before we go too far I think we need to recap, in order to turn the original idea into something that could be tested on the show. This needs to be something that can be filmed and tested in 7-10 days - the exact amount of time given for filming varies depending on who you ask. The higher figure seems to come from Jamie, but I'm guessing that as a producers Adam and Jamie have less time per day for filming than the build team. Related to this is that they don't want to effectively turn the show over to experts, but have the cast directly involved in all stages of testing and building where possible*. Both of these factors mean that any engine design can't be too complex or require too much technical knowledge. It also means that we have to boil the idea down to the barest parts, so they don't waste time trying to test or build things they don't need to. Although this was called 'Wooden Car' I think we should eliminate the car as a whole and just concentrate on the engine. I'm going to say that just about everything on a car could be made from wood alone, if you have the time and skills to design and build those things correctly - meaning that, say, making a working breaking system would be a matter of trial and error rather than a questionable prospect**. So lets deal purely with the engine without considering other aspects. There are two basic ways to go here. One is to assume that the engine you are replacing has seized up. But you can scavenge some of the smaller electrical parts from it. Basically you are trying to make a conventional ICE engine using wood. (As I recall someone on Discovery asked if you could make a piston from wood, so this is a variation/continuation of this). The second way would be to assume that most or all of the electrical is badly damaged, forcing you to try and create the entire engine out of wood alone. Both of these have merits I think, and could be tested in small scale to see which is the more practical way to go for a 'full sized' engine. They could try building small scale versions of all types and put them in a small RC car to see how they fare. The fuel tank and fuel lines should, I think, remain as they would be for a normal engine - in other words those parts of the system remain as they were. If nothing else safety has to be considered, and conventional fuel tanks and lines are a known quantity where as tanks/lines made from wood could prove dangerous. To keep the testing as quick and simple as possible I think the simplest thing to do is get an old Go-Cart and simply remove the original engine and replace it with their own design. This should give something large enough to make for good TV, while not so large it would take too long to build. (*Having said that, this would be an opportunity to get Jessie Combs back on the show if they feel they do need an expert to be more closely involved.) (**They could always cut the idea into parts, trying to make wooden brakes and/or wooden gears ect in later episodes. If they do manage to make a wooden engine then they could later put all the parts together to make the 'Wooden Car'. So in essence this would be three possible ideas in one.) Thoughts? I don't see a go-cart as a very good idea myself. Go carts have tiny, fast revolving engines, which would be the exact opposite of any condition in which I would want to be running a wooden engine . The pressure and temperature would likely blow the thing apart in the first few minutes. I think a better idea (and what I have always envisioned this would be used for) would be something like powering a tractor, or another slow vehicle, so you can keep the speed lower and have the room to build a much bigger engine to keep the pressure down. A wooden engine with high RPM would likely quickly tear itself apart, not to mention all the cooling trouble due to the increased surface area relative to volume. Honestly, though, I have never imagined this could possibly be a drop-in replacement for a conventional engine, because of how much more massive the cylinder walls will have to be to keep the thing from flying apart. Any vehicle would probably require drastic modifications to fit such an engine in its engine compartment. But, thinking about it, their may be a way to do a somewhat drop in solution. Most tractors have something known as a "PTO" or "Power Take Off" shaft which is connected to their drive train and allows devices the tractor is pulling to get rotational power for various uses. It might be possible to re-engineer it so that a PTO accepts the power, rather than gives it out, allowing you to attach the engine their. This further allows you to tow the engine behind the tractor, eliminating most size concerns and, in my opinion, giving it the best chance of succeeding. I do, however, agree with using conventional fuel pumps and such instead of making a pump and pipes out of wood. If you can make a wooden piston, you can make the reed valves to turn it into a pump, and thus it would just save time, and make things safer, not invalidate the concept. Since you are pushing the idea of a Go-Kart engine, how would you design it so that it would be lubricated, cooled, safe, and move while still fitting into the spot for the old Go-Kart engine? This needs to be able to sustain the Go-Kart for around *7 hours, otherwise it would of been faster to just walk in the week you spent making this. Think it could be done? *20 miles per day walking, 40-60 mph for Go-Kart with original engine, going for ambitious 20 with wood, 7 days making the thing. 140/20= 7 hours. |
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Post by Cybermortis on Nov 6, 2012 19:22:53 GMT
I was thinking of a Go-Cart because of low weight, low cost and because it would require a smaller engine. (And a smaller engine makes it more likely they could build a 'spare' or possibly build more than one type of engine - If they find that they have two possible engine designs that might work in larger scale, then there is the possibility of them that they could race the two designs side by side).
Something like a tractor could be problematic, first because of the cost of buying one. Second because even stripped down it will weight a great deal which means that even if the engine works it may not have enough power to move the vehicle. Last of all transporting and storing a tractor would be a nightmare.
Go-Carts would be light, small enough that they can store them in the shop without trouble and just as importantly they'd be able to stick them in the back of a truck for transport to a test location.
Problems with Go-Carts using engines with high RPM are probably not a problem at all. The build would be to show and test the concept, not attempt to duplicate the performance of a Go-Cart. So altering the gearing and wheels if/as needed wouldn't be a problem or 'against' the idea as a whole.
Endurance wise, it would probably be better to pick a shorter 'ideal' running time than 7 hours - which would mean they'd have a VERY long day, and if anything went wrong during filming on location they could end up spending two or three days trying to run this one test, which I don't think is practical from the production point of view especially when it can take them an hour or more to set the cameras up.
Let's set a figure of an hour, on the basis that if the engine can run this long without problems then getting better endurance is simply a matter of fine-tuning the design and build. This should given them a long enough test-time, plus enough leeway that they can consider other tests or even tinkering with the engine or replacing it (if they have a spare) as they see fit.
I think, btw, that I've figured out how to test the engine safely for all concerned.
The idea would be to have a metal rail bolted to the floor, creating a circular track. (Which they could set up indoors in a large enough area, to avoid SF's weather and any delays that can cause for filming.) The engine could be turned on, and the 'cart' run by remote around the track. This would be perfect I think, certainly for the endurance testing since they could simply sit back and let the thing keep running. It also gives a high degree of safety, since even if the RC system fails (which has been known to happen on the show) the cart isn't going anywhere - probably a rather major consideration when one possible situation involves a burning cart trundling off into the distance.
If they find that one or more designs work, they could always remove the cart from the rails and test it elsewhere...or even set up a second rail to create the one of the worlds largest slot-car racing tracks to compare performance...Now that would be cool.
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Post by chriso on Nov 6, 2012 20:20:36 GMT
I was thinking of a Go-Cart because of low weight, low cost and because it would require a smaller engine. (And a smaller engine makes it more likely they could build a 'spare' or possibly build more than one type of engine - If they find that they have two possible engine designs that might work in larger scale, then there is the possibility of them that they could race the two designs side by side). Something like a tractor could be problematic, first because of the cost of buying one. Second because even stripped down it will weight a great deal which means that even if the engine works it may not have enough power to move the vehicle. Last of all transporting and storing a tractor would be a nightmare. Go-Carts would be light, small enough that they can store them in the shop without trouble and just as importantly they'd be able to stick them in the back of a truck for transport to a test location. Problems with Go-Carts using engines with high RPM are probably not a problem at all. The build would be to show and test the concept, not attempt to duplicate the performance of a Go-Cart. So altering the gearing and wheels if/as needed wouldn't be a problem or 'against' the idea as a whole. Endurance wise, it would probably be better to pick a shorter 'ideal' running time than 7 hours - which would mean they'd have a VERY long day, and if anything went wrong during filming on location they could end up spending two or three days trying to run this one test, which I don't think is practical from the production point of view especially when it can take them an hour or more to set the cameras up. Let's set a figure of an hour, on the basis that if the engine can run this long without problems then getting better endurance is simply a matter of fine-tuning the design and build. This should given them a long enough test-time, plus enough leeway that they can consider other tests or even tinkering with the engine or replacing it (if they have a spare) as they see fit. I think, btw, that I've figured out how to test the engine safely for all concerned. The idea would be to have a metal rail bolted to the floor, creating a circular track. (Which they could set up indoors in a large enough area, to avoid SF's weather and any delays that can cause for filming.) The engine could be turned on, and the 'cart' run by remote around the track. This would be perfect I think, certainly for the endurance testing since they could simply sit back and let the thing keep running. It also gives a high degree of safety, since even if the RC system fails (which has been known to happen on the show) the cart isn't going anywhere - probably a rather major consideration when one possible situation involves a burning cart trundling off into the distance. If they find that one or more designs work, they could always remove the cart from the rails and test it elsewhere...or even set up a second rail to create the one of the worlds largest slot-car racing tracks to compare performance...Now that would be cool. Okay, I can buy using gearing to keep the engine at speeds it can handle (though if you are doing the entire car out wood, it might be another story... wooden gearing tends to wear out). And agree if it can go for an hour, it is probably a doable design. However, I still am not sure that a engine that small can keep the pressure in the cylinder within a range it can handle while still providing useful forward movement. The primary reason I think big pistons are essential is to keep the pressure down. Assuming the engine is made out of a solid block of wood. But on that note, I have had an idea... An unfortunate fact about this engine is that the way we are talking about making it, no matter how its build, their will be a direction that goes with the grain, and that direction will be able to handle far less pressure than the rest of the design. I propose that our builder has a lot of wood-glue and a bunch of paper lying around. Paper, believe it or not, has a grain too, and more importantly you can apply that grain in whatever direction you want. If you were to mill your cylinder out from the ends, aka with the grain, it would tend to want to split along the sides, lengthwise. However, by re-enforcing it by placing many layers of paper along its side, I bet you could increase the pressure it could handle drastically, improving the engine, and more importantly making smaller engines more easily achievable. Their are a few problems with this. One, you can no longer externally cool the thing (or risk the wood glue denigrating), and two, your not going to be able to properly re-enforce it if you are manufacturing an engine block, meaning you will have to somehow get individual cylinders secured to a frame (more wood-glue?). Regardless, I suspect that if you could figure out the cooling and mounting, this design would make a vastly superior engine And cyber. I pulled that endurance figure out from your scenario of being stranded with the car's electrical system and a ton of wood. Also, what are your thoughts on cooling? It will obviously be a very important issue. |
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Post by freegan on Nov 6, 2012 23:26:08 GMT
The 'grain problem' might be solved by milling the chamber along the central axis of a section of the trunk of the donor tree.
If multiple chambers are required, the milled trunk sections could be inserted into a retaining block constructed from a larger tree trunk.
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Post by chriso on Nov 7, 2012 0:16:13 GMT
How would that help, freegan? Is it suppose to be stronger in that location? Or are you thinking about just using a massive piece to compensate? right now the discussion is on something you can put in a go-kart, so a massive piece probably would not be an option.
Or am I misunderstanding your statement?
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Post by trakmec on Nov 7, 2012 0:35:39 GMT
freegan may be on to something, Correct me if I'm wrong but your suggesting a cylinder that has the gain going lengthwise, which is then inserted 90 degrees cross grain into another, larger piece of wood? The larger piece essentially looking like the engine block of a large air cooled diesel with the piston cylinders stuck into it?
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Post by trakmec on Nov 7, 2012 0:40:14 GMT
Of course if it's just a wooden engine, why not use laminates to solve the gain stress issue? Drill the cylinder out with the grain of a useable sized block of wood, lathe that piece down to a 1"-2" wall thickness then take a bunch of plywood blocks, glue and press them together and drill a hole big enough to fit your cylinder into, sort of like a sleeved cylinder diesel?
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Post by chriso on Nov 7, 2012 1:48:18 GMT
Oh, I get it now. Freegan, your right that probably would work. And plywood better still!
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Post by freegan on Nov 7, 2012 6:04:02 GMT
Oh, I get it now. Freegan, your right that probably would work. And plywood better still! I think your proposal of using plywood is the better option provided that the binding adhesives are of vegetable origin to satisfy the purists. While my idea of inserts with vertical grain may have merit insofar as piston/chamber surface wear could be minimized, encasement in a single block would only give two directions of grain where at least three would be required for structural strength. Plywood would also offer the option of choosing each layer of ply/resin for its material characteristics to optimize the heat/friction/durability of the chamber surface and the outer layers for heat transfer/cooling. |
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Post by trakmec on Nov 7, 2012 14:37:33 GMT
OK, I have a concept in mind but not too computer literate. Does anyone know how I might go about putting a google sketch image up here instead of trying to explain in detail?
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