How much thrust?
Moderator: Mike Everman
Re: How much thrust?
Hi Mark, thanks you have given me loads of ideas, you have given me lots of info it would have taken me lots of time to learn for myself, for someone new to the subject this kind of thing is invaluable, its much appreciated and I will keep you informed of my progress.
Re: How much thrust?
I was looking at the Atom jet ports and they are 7mm. The Tigerjet ports are .256ths which translates very close to 6.5mm making only a half millimeter difference. The Dynajet ports are drilled to .343ths and then reamed to .357-360ths or somewhere inbetween 9mm and 9.1mm if I read this chart correctly.
http://mdmetric.com/tech/cvtcht.htm
Don Laird sent me his Dyna-jet schematic that he drew up and the reeds are .006ths, C-1095 Blue Tempered Spring Steel, the same thickness as the Tigerjet. So conceivably, if you wanted to break all the rules, you might get away with .006ths reeds and see how they do. I think one time I asked Earl Bailey about thicker reeds and he said that .006ths just works best overall and maybe mentioning something about it being harder to start with thicker reeds.
Since the Dynajet ports use a ~9mm hole and the Atom a 7mm, you have some margin of safety for the reed not deforming over the hole on impact with .006ths, since that is what thickness my Bailey jet and Dynajet came supplied with. I have in the past made some impressive indentations in my homemade reeds using larger holes when my prototypes backfired or barked and then no more action.
The Dynajet and Bailey jet reeds are interchangable but there is also a modified speed version where the ports are widened/bored out slightly and the reeds are referred to a bigfoot reeds. Occasionally, you will see them for sale on eBay. The petals do look bigger. I also recall I think in talking to Earl that the retainer can be modified to let the reeds swing open more than the standard retainer. But for this trade for more speed, the reeds do not last as long. But I suppose that is to be expected, giving them more play to slap back and forth.
In my Bailey jet manual it says a mixture of 20% nitromethane and 80% methanol has produced a measured thrust of 5 pounds 11 ounces. I remember Earl telling me his Bailey jet will really bark if you use some nitro.
One funny part about flying the Bailey jet in the manual is that it's not recommended for one person to start the engine. It goes on to talk about the Model T spark coil being the best spark generating device.
"It makes a mean 14,000 + volt spark, using a motorcycle-sized six volt battery. Regardless of what spark system you choose, it should be used with a button that actuates it only when pressed. This will help to prevent accidentally leaving the spark switched on and zapping your helpers! The helpers will lose their enthusiasm if this happens." ha
These Team Helmond guys don't use a spark plug, but rather an apparatus that they stick up the tail into the combustion chamber to start the engine. It's kind of like a spark plug though with a long reach. I guess you could make one simple enough if you didn't want to go with a spark plug. The poorer Dynajet fliers in some really old literature I have just lit the tail end with a constantly running torch and puffed in starting air with a tire pump, typically how you would start a Dynajet anyway. Again, short quick pumps/bursts of air often work better than a constant stream, letting the reeds ramp up, letting them sense the feedback better perhaps.
http://www.youtube.com/watch?v=68MRkGxhvRE
http://pulsejet.amtjets.com/index1.html
http://www.youtube.com/watch?v=JrbP2C7Hg5w
http://mdmetric.com/tech/cvtcht.htm
Don Laird sent me his Dyna-jet schematic that he drew up and the reeds are .006ths, C-1095 Blue Tempered Spring Steel, the same thickness as the Tigerjet. So conceivably, if you wanted to break all the rules, you might get away with .006ths reeds and see how they do. I think one time I asked Earl Bailey about thicker reeds and he said that .006ths just works best overall and maybe mentioning something about it being harder to start with thicker reeds.
Since the Dynajet ports use a ~9mm hole and the Atom a 7mm, you have some margin of safety for the reed not deforming over the hole on impact with .006ths, since that is what thickness my Bailey jet and Dynajet came supplied with. I have in the past made some impressive indentations in my homemade reeds using larger holes when my prototypes backfired or barked and then no more action.
The Dynajet and Bailey jet reeds are interchangable but there is also a modified speed version where the ports are widened/bored out slightly and the reeds are referred to a bigfoot reeds. Occasionally, you will see them for sale on eBay. The petals do look bigger. I also recall I think in talking to Earl that the retainer can be modified to let the reeds swing open more than the standard retainer. But for this trade for more speed, the reeds do not last as long. But I suppose that is to be expected, giving them more play to slap back and forth.
In my Bailey jet manual it says a mixture of 20% nitromethane and 80% methanol has produced a measured thrust of 5 pounds 11 ounces. I remember Earl telling me his Bailey jet will really bark if you use some nitro.
One funny part about flying the Bailey jet in the manual is that it's not recommended for one person to start the engine. It goes on to talk about the Model T spark coil being the best spark generating device.
"It makes a mean 14,000 + volt spark, using a motorcycle-sized six volt battery. Regardless of what spark system you choose, it should be used with a button that actuates it only when pressed. This will help to prevent accidentally leaving the spark switched on and zapping your helpers! The helpers will lose their enthusiasm if this happens." ha
These Team Helmond guys don't use a spark plug, but rather an apparatus that they stick up the tail into the combustion chamber to start the engine. It's kind of like a spark plug though with a long reach. I guess you could make one simple enough if you didn't want to go with a spark plug. The poorer Dynajet fliers in some really old literature I have just lit the tail end with a constantly running torch and puffed in starting air with a tire pump, typically how you would start a Dynajet anyway. Again, short quick pumps/bursts of air often work better than a constant stream, letting the reeds ramp up, letting them sense the feedback better perhaps.
http://www.youtube.com/watch?v=68MRkGxhvRE
http://pulsejet.amtjets.com/index1.html
http://www.youtube.com/watch?v=JrbP2C7Hg5w
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Re: How much thrust?
Hi Mark, I have been thinking the same thing and I have made a valve array that is 7 thou thick I will try it and compare to an 8 thou valve, I have noticed quite a bit of fuel dripping back out the intake and I am sure its because the valve is to stiff, I have finnished making my buzz coil with the help of my sparky friend and it works beautifully but it has an on/off switch only so will have to be careful, my methanol finally turned up so today "friday 5th" I shall be having some fun and learning as I go, will post some pics and vid if all goes well, cheers Phil.
Re: How much thrust?
Hi Phil,
Is you buzz coil kind of like a Model T coil with points? Since I usually work alone my Model T coil just has an on/off switch. The funny thing about loud noises and such is that it can make you forget the coil is still on. I've zapped myself a few times and it's enlivening. One thing about coils whether they are large or small, exotic or simple, is that you don't want to make the gap too large accidentally, say when you remove the spark plug clip or such while it's still running. The voltage will arc internally in the coil and eventually short out which then ends the life of the ignition system. One time I did this but fortunately I had my Model T coil clamped on the underside of a metal sawhorse where the proximity to a ground was close by; it made a neat arcing sound to the sawhorse. Some people put a safety feature on their buzz boxes so that there is a default gap that can come into play if need be.
I have a couple of small stungun coil/spark gap units that will arc 2 inches with a really poppy spark. Yet the one I have been toying with will now only go about an inch, anymore and it won't jump the gap but you can hear something going on inside. And with a 6 volt battery you can run them for much longer than a short burst like most stunguns, making as much ozone as you care to breathe, and they have a high duty cycle if run at a slightly lower voltage. But since I stressed the one unit by widening the gap beyond the two inch distance, the little guy has been weakened.
Here's the ignition system I use most of the time, a wooden box buzz coil and wall transformer instead of a battery. The thing has run for many hours over the years and just in case it ever gives out, I have another in a black plastic case, but the same parts essentially, just a different look.
And I have this hefty looking device and it too comes with a warning not to extend the pointy brass tips beyond 2 inches lest you damage the unit.
Good luck with your testing, if nothing else you'll probably hear a few good backfirings and bangs. That's always a good teaser for things to come. What's your bottle of methanol say on the label? The kind I buy is for removing water from gasoline in a car tank. Methanol will absorb water out of the air so keep it capped tightly when not in use. If methanol has some water in it, it will be far less perky. If you have very pure methanol and a piece of clean, bright magnesium, this alcohol will eat up/react with magnesium releasing hydrogen gas, just like an alka seltzer in water. I did that once with a magnesium fire starter. But I also buy methanol from a racing business, in 5 gallon quantities. That's really the way to go for it is far cheaper like that over here.
Is you buzz coil kind of like a Model T coil with points? Since I usually work alone my Model T coil just has an on/off switch. The funny thing about loud noises and such is that it can make you forget the coil is still on. I've zapped myself a few times and it's enlivening. One thing about coils whether they are large or small, exotic or simple, is that you don't want to make the gap too large accidentally, say when you remove the spark plug clip or such while it's still running. The voltage will arc internally in the coil and eventually short out which then ends the life of the ignition system. One time I did this but fortunately I had my Model T coil clamped on the underside of a metal sawhorse where the proximity to a ground was close by; it made a neat arcing sound to the sawhorse. Some people put a safety feature on their buzz boxes so that there is a default gap that can come into play if need be.
I have a couple of small stungun coil/spark gap units that will arc 2 inches with a really poppy spark. Yet the one I have been toying with will now only go about an inch, anymore and it won't jump the gap but you can hear something going on inside. And with a 6 volt battery you can run them for much longer than a short burst like most stunguns, making as much ozone as you care to breathe, and they have a high duty cycle if run at a slightly lower voltage. But since I stressed the one unit by widening the gap beyond the two inch distance, the little guy has been weakened.
Here's the ignition system I use most of the time, a wooden box buzz coil and wall transformer instead of a battery. The thing has run for many hours over the years and just in case it ever gives out, I have another in a black plastic case, but the same parts essentially, just a different look.
And I have this hefty looking device and it too comes with a warning not to extend the pointy brass tips beyond 2 inches lest you damage the unit.
Good luck with your testing, if nothing else you'll probably hear a few good backfirings and bangs. That's always a good teaser for things to come. What's your bottle of methanol say on the label? The kind I buy is for removing water from gasoline in a car tank. Methanol will absorb water out of the air so keep it capped tightly when not in use. If methanol has some water in it, it will be far less perky. If you have very pure methanol and a piece of clean, bright magnesium, this alcohol will eat up/react with magnesium releasing hydrogen gas, just like an alka seltzer in water. I did that once with a magnesium fire starter. But I also buy methanol from a racing business, in 5 gallon quantities. That's really the way to go for it is far cheaper like that over here.
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Re: How much thrust?
One thing I thought about when my first Tigerjet reed broke, a whole petal just broke off at the base after a few times of running. So I put the replacement reed on and found it was extremely difficult to blow into the front of the engine, the valves were so stiff. So I took the head off the engine and pushed a stick of some sort into the throat and caused the reeds to flex up. I did this for all ten reeds. It's also a good way to check to see if your reeds are perfectly aligned, looking at them from several angles as they lay back down over the ports, if one edge is getting more overlap than the opposite. Seems I read somewhere that you could lift them with your fingernail too. 006ths seems somewhat thick for the Tigerjet but who knows. There is an alignment hole on the Bailey jet and the Dynajet but oddly the Bailey jet you want the little hole right next to the edge of the reed and the Dynajet you want the tiny alignment hole/mark centered between two reeds.
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Re: How much thrust?
Hi Guys for the atom jet I wouldnt even think about running a 8 thou reed valve. 6 thou would be thick enough and I would even think about 5thou.. All these materials are readily available. Just need a quick check online and you will find them.
All my valves I made for the standard dyna/baily/jetbill engines were 6thou the bigfoot valves were 6thou and the tigrejet 6thou. The tiny afm500 needs 4thou.
8Thou is used for the really hot fuels IE: 50% Nitro 50% Propylene oxide or the bigger engines like the zannin etc
Hope this helps
Robert Bolton
PS: When setting up the valve on the head you need to make sure it seals perfectly.......... 2 minutes is not enough sometimes it can take 30 minutes to get the fastjets sorted...
All my valves I made for the standard dyna/baily/jetbill engines were 6thou the bigfoot valves were 6thou and the tigrejet 6thou. The tiny afm500 needs 4thou.
8Thou is used for the really hot fuels IE: 50% Nitro 50% Propylene oxide or the bigger engines like the zannin etc
Hope this helps
Robert Bolton
PS: When setting up the valve on the head you need to make sure it seals perfectly.......... 2 minutes is not enough sometimes it can take 30 minutes to get the fastjets sorted...
Re: Atom Jet with applied EVG
Hi Mark/everyone, some good news and some bad news, the bad first, my ignition coils keep burning out I have used two so far, I dont know why I will have to see my mate and have a redesign they last only about four minutes. The good news is my jet is running lovely now on methanol, using the information given to me by Mark I guesstimated the cross hole in the flowjector at 1mm instead of .5mm, the metering/ supply hole is now 1.5mm instead of 1mm, and I Also made the starting air hole 1.5mm instead of 1mm to give more puff and help open up the stiff reed petals,the engine now starts very easily with just a couple of bursts of air and either a spark or a flame at the tail, when I was using petrol the reeds were getting to hot in just 20 seconds running they had lost temper, but now with methanol I have run for a total of 5 minutes and the reeds are like new still, they are standard 0.008" reeds, I will now do some thrust testing with different thicknesses of reed and varying flowjector hole sizes and see what works best. Here is a video of the engine running, enjoy. Phil.
Last edited by woody500 on Sun Feb 07, 2010 11:09 am, edited 1 time in total.
Re: How much thrust?
Congrats Phil,
Looks like you've harnessed the power of the Atom. I liked the sound of it, especially at the end where you can hear an echo as things fall silent. Isn't it funny how much sound a little thing like that can make. People who haven't seen a pulsejet start up are the most fun to have around, to see their expression. Get some spectators. ha
The Atom jet had a nice color too. Good presentation.
Looks like you've harnessed the power of the Atom. I liked the sound of it, especially at the end where you can hear an echo as things fall silent. Isn't it funny how much sound a little thing like that can make. People who haven't seen a pulsejet start up are the most fun to have around, to see their expression. Get some spectators. ha
The Atom jet had a nice color too. Good presentation.
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Re: How much thrust?
Phil,
If you want more variables to play with, you might make some retainers with more or less play. My very first pulsejet was a 2 inch diameter combustion chamber using a jumbo .015ths reed over the center of a large washer which spanned the width of the combustion chamber. It was a one reed valve made of soft aluminum flashing, about the size and shape of a half dollar. Then I had a smaller, thin bent washer to act as the retainer. The retainer kept the aluminum flashing from bending past the point of no return. It had one screw off to one edge of the thick washer holding the retainer and reed in place. I drilled a hole in the reed and the two washers and that was my valve ensemble, the three parts stacked on top of each other and then bolted/sandwiched down. ha
The jet ran loudly for over one minute before the flex/snap back gave out. I let it have just enough play to swing open without destroying the springiness.
When I blew into the front of it with my mouth, that reed would really honk.
With reed thicknesses I think everything is going to be a trade-off with responsiveness, valve life, thrust, and all this contigent on the valve retainer limits and fuel used, and how the reeds lay over the ports, spring loaded or just barely resting over them. Some literature I have talks about that, actually having the reed just barely resting over the port. And the speed with which the pulsejet travels, the flame front pushed back from the reeds at higher speeds. Imagine the myriad of engineers and man hours that have been devoted to all kinds of reed design. Each with their own philosophy and little tricks, little interesting details discovered along the way. Tharratt got over 24 hours at full thrust on some reeds he made, each had a rubber laminate between the multiple reeds, some single runs lasting 7 hours straight. By using thin reeds stacked, he preserved the responsiveness over a single thicker reed the article said.
What's your ignition system look like, it doesn't sound like it has a very long duty cycle. ha
In closing, I think your Atom jet is a real winner, every part smooth and pleasing to the eye, quite a talented job. Maybe the spark plug could have a smaller signature, but that's a quick fix. Do you have the plane for it now?
If you want more variables to play with, you might make some retainers with more or less play. My very first pulsejet was a 2 inch diameter combustion chamber using a jumbo .015ths reed over the center of a large washer which spanned the width of the combustion chamber. It was a one reed valve made of soft aluminum flashing, about the size and shape of a half dollar. Then I had a smaller, thin bent washer to act as the retainer. The retainer kept the aluminum flashing from bending past the point of no return. It had one screw off to one edge of the thick washer holding the retainer and reed in place. I drilled a hole in the reed and the two washers and that was my valve ensemble, the three parts stacked on top of each other and then bolted/sandwiched down. ha
The jet ran loudly for over one minute before the flex/snap back gave out. I let it have just enough play to swing open without destroying the springiness.
When I blew into the front of it with my mouth, that reed would really honk.
With reed thicknesses I think everything is going to be a trade-off with responsiveness, valve life, thrust, and all this contigent on the valve retainer limits and fuel used, and how the reeds lay over the ports, spring loaded or just barely resting over them. Some literature I have talks about that, actually having the reed just barely resting over the port. And the speed with which the pulsejet travels, the flame front pushed back from the reeds at higher speeds. Imagine the myriad of engineers and man hours that have been devoted to all kinds of reed design. Each with their own philosophy and little tricks, little interesting details discovered along the way. Tharratt got over 24 hours at full thrust on some reeds he made, each had a rubber laminate between the multiple reeds, some single runs lasting 7 hours straight. By using thin reeds stacked, he preserved the responsiveness over a single thicker reed the article said.
What's your ignition system look like, it doesn't sound like it has a very long duty cycle. ha
In closing, I think your Atom jet is a real winner, every part smooth and pleasing to the eye, quite a talented job. Maybe the spark plug could have a smaller signature, but that's a quick fix. Do you have the plane for it now?
Last edited by Mark on Sun Feb 07, 2010 5:48 pm, edited 1 time in total.
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Re: How much thrust?
Phil,
Here's a few tidbits from an article entitled "The Propulsive Duct" by C.E. Tharratt, 1965.
"The valve shown in FIG.24a was designed to withstand 25 hr. at full thrust., this included several continuous runs of 7 hr. duration; the reed life increases substantially with reduced thrust levels."
"Fig 24a shows an exploded view of a typical reed valve consisting of spacers, reeds, and seats, held together by tie bolts and end plates. The reeds can clearly be seen to consist of a rubber reed sandwiched between two metal reeds per set. The composite construction being necessary to give added stiffness whilst retaining as closely as possible, the response characteristics of a single metal reed."
"The frequency of operation of the reed is determinded by the combustion frequency, however its amplitude of opening is dependent upon its dynamic response characteristics, which is a function of the combustion frequency nf and the natural frequency of the reed n."
"Ideally, the reed should have a natural frequency n as high as possible so that in practice its motion would approximate to a square wave, thus allowing the reed to snap open and shut. Unfortunately the pressure available to open the valve under these conditions is too low to give a reasonable deflection, therefore the number of reeds must be increased in order to achieve the desired through-put area."
"To reduce the load required to open the valve to a minimum the reed length must be tuned to resonate with the combustion frequency, ie nf/n "arrow" 1, see FIG. 21. In practice the reed stress levels set a practical limit to the permissible reed amplitude. In addition it was shown earlier that the combustion frequency changes slightly as the thrust varies, therefore, using a .008-in. thick reed of 100-110 ton stainless or carbon steel a reasonable working ratio is nf/n~0.8."
" ... math formulas ... unless the value of Um is chosen carefully the duct may not be capable of passing air and therefore devlivering thrust under static conditions. Obviously some means of automatically varying reed stiffness , and thereby compensating for the effect of U2, is desirable, but this adds complication and detracts from the basic simplicity of the duct."
"One method of increasing reed stiffness is to pre-form the reeds to a slight curvature, this has the effect of pre-loading the reed on to its seat and the reed will not open until this pre-load is overcome. It is important, of course, to ensure that the reeds have identical pre-loading otherwise uniform opening will not occur. Another method, which has found wider favour, is to incorporate double or even triple reeds. Utilizing the fact that the reed stiffness increases in proportion to the number of reeds while the dynamic response characteristic varies only slightly from that of a single reed."
On varying thrust ...
"Fig 35 shows a typical annular venturi of an engine which could not be stalled however fast the fuel flow was varied, whether the duct was at one instant merrily bubbling at 6 lb. thrust or, at the next instant, delivering its maximum thrust of 100 lb. At none of the intermediate thrust settings was it possible to smell aldehydes or peroxides and the combustion was extremely uniform."
Here's a few tidbits from an article entitled "The Propulsive Duct" by C.E. Tharratt, 1965.
"The valve shown in FIG.24a was designed to withstand 25 hr. at full thrust., this included several continuous runs of 7 hr. duration; the reed life increases substantially with reduced thrust levels."
"Fig 24a shows an exploded view of a typical reed valve consisting of spacers, reeds, and seats, held together by tie bolts and end plates. The reeds can clearly be seen to consist of a rubber reed sandwiched between two metal reeds per set. The composite construction being necessary to give added stiffness whilst retaining as closely as possible, the response characteristics of a single metal reed."
"The frequency of operation of the reed is determinded by the combustion frequency, however its amplitude of opening is dependent upon its dynamic response characteristics, which is a function of the combustion frequency nf and the natural frequency of the reed n."
"Ideally, the reed should have a natural frequency n as high as possible so that in practice its motion would approximate to a square wave, thus allowing the reed to snap open and shut. Unfortunately the pressure available to open the valve under these conditions is too low to give a reasonable deflection, therefore the number of reeds must be increased in order to achieve the desired through-put area."
"To reduce the load required to open the valve to a minimum the reed length must be tuned to resonate with the combustion frequency, ie nf/n "arrow" 1, see FIG. 21. In practice the reed stress levels set a practical limit to the permissible reed amplitude. In addition it was shown earlier that the combustion frequency changes slightly as the thrust varies, therefore, using a .008-in. thick reed of 100-110 ton stainless or carbon steel a reasonable working ratio is nf/n~0.8."
" ... math formulas ... unless the value of Um is chosen carefully the duct may not be capable of passing air and therefore devlivering thrust under static conditions. Obviously some means of automatically varying reed stiffness , and thereby compensating for the effect of U2, is desirable, but this adds complication and detracts from the basic simplicity of the duct."
"One method of increasing reed stiffness is to pre-form the reeds to a slight curvature, this has the effect of pre-loading the reed on to its seat and the reed will not open until this pre-load is overcome. It is important, of course, to ensure that the reeds have identical pre-loading otherwise uniform opening will not occur. Another method, which has found wider favour, is to incorporate double or even triple reeds. Utilizing the fact that the reed stiffness increases in proportion to the number of reeds while the dynamic response characteristic varies only slightly from that of a single reed."
On varying thrust ...
"Fig 35 shows a typical annular venturi of an engine which could not be stalled however fast the fuel flow was varied, whether the duct was at one instant merrily bubbling at 6 lb. thrust or, at the next instant, delivering its maximum thrust of 100 lb. At none of the intermediate thrust settings was it possible to smell aldehydes or peroxides and the combustion was extremely uniform."
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Re: How much thrust?
Hi Mark/everyone, my buzz coil is basically just a 12v battery an 8 pin relay a couple of capaciters and an ignition coil from a car I dont know anything about electrics so will have to get my mate to sort it out, the spark plug will be changed for a smaller one, I think even a small one ruins the nice flowing lines of any pulsejet engine but it is a nessesity so thats that, I dont have the plane to mount the engine on yet but when I am motivated to do something witch I am then it wont take long to build, thanks for posting all the info you have Mark its all very interesting, your right there must have been thousands of hours of research gone into just the reeds let alone the rest of the engine. Here are some vids for you the first is the tailpipe using methanol and the second is using propanol, the propanol is producing lots more power, this is with a 7thou reed, I have not got any thrust figures yet for lack of a decent thrust rig. Phil. Harnessed the power of the atom, very good Mark, funny.
Re: How much thrust?
It seemed like the methanol was running at a slightly higher pitch that the isopropyl. Maybe it was just me. Are you using the same "metering jet" size and cross hole for both runs? If so, the methanol may be running a little lean. Methanol has a stoichiometric air fuel ratio of 6.42:1 and ethanol 9:1. Gasoline 14.7:1. Isopropyl is going to have a ratio way "higher" than methanol and closer to gasoline.
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Re: How much thrust?
Regarding the amount of time that has gone into reed designs makes me recall the history of the Dynajet. Some may have supposed that after getting a look at the V-1 late in WWII, the inventors designed the prototype Dyna-Jet , petal valve and all.
But from a newsletter by Al Doyle - "Not so, says engine hobbyists J. BIshop of Hicksville, New York. According to Mr. Bishop the petal valve was invented by his friend John Le Valley, employed by the Ingersoll-Rand Corporation: who was living in Painted Post, New York at the time. We looked up U.S. Patent #1,634,949, and sure enough, there was the petal valve on a drawing dated July 5, 1927."
I imagine the flower petal valve philosophy had been looked over to a great extent, and there's not much left for a major improvement there. With today's computers I'm sure you could discover a greater understanding about the reeds and all, but if you are looking for a goldmine from the micro-examination of every last detail, I doubt there are many more big nuggets to find. But knowledge like that is nice to know, you can apply it to other ideas. Imagine all the science behind reeds of every kind: musical instruments, engine valves, bird and animal calls, exotic medical lung flute devices, and on and on. I once took apart one of those compressed "air" air horns for boating and such. The reed is as big and round as a silver dollar. It's sitting on my desk right next to me. The reed is only .003ths thick, yet it really cranks out the sound. Kind of like a pulsejet in that respect. ha
Here's some pictures I took of the John Le Valley air compressor design and the Dyna-Jet like prototype valves literature/patent I got in the mail from Don Laird. Click to enlarge the pics. Maybe the flower petal valve with retainer was invented even earlier, who knows.
Note on the three pages of the Dyna-Jet prototype patent, it was first filed on Feb. 25, 1946.
But from a newsletter by Al Doyle - "Not so, says engine hobbyists J. BIshop of Hicksville, New York. According to Mr. Bishop the petal valve was invented by his friend John Le Valley, employed by the Ingersoll-Rand Corporation: who was living in Painted Post, New York at the time. We looked up U.S. Patent #1,634,949, and sure enough, there was the petal valve on a drawing dated July 5, 1927."
I imagine the flower petal valve philosophy had been looked over to a great extent, and there's not much left for a major improvement there. With today's computers I'm sure you could discover a greater understanding about the reeds and all, but if you are looking for a goldmine from the micro-examination of every last detail, I doubt there are many more big nuggets to find. But knowledge like that is nice to know, you can apply it to other ideas. Imagine all the science behind reeds of every kind: musical instruments, engine valves, bird and animal calls, exotic medical lung flute devices, and on and on. I once took apart one of those compressed "air" air horns for boating and such. The reed is as big and round as a silver dollar. It's sitting on my desk right next to me. The reed is only .003ths thick, yet it really cranks out the sound. Kind of like a pulsejet in that respect. ha
Here's some pictures I took of the John Le Valley air compressor design and the Dyna-Jet like prototype valves literature/patent I got in the mail from Don Laird. Click to enlarge the pics. Maybe the flower petal valve with retainer was invented even earlier, who knows.
Note on the three pages of the Dyna-Jet prototype patent, it was first filed on Feb. 25, 1946.
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Re: How much thrust?
I tried to find the exact air fuel ratio for isoproply alcohol but I couldn't. I did find some other tidbits though that might provide some useful information.
Methanol has a formula of CH3OH - Ethanol C2H5OH - Isopropyl C3H7OH.
Specific gravity for these alcohols, say a cubic meter would weigh 790 kg or rather just .79 that of water, water being 1000 kg. There is so little variation in weight per volume that they all round up or down to a specific gravity of .79, it's just the way the marbles pack. I remember an experiment where you pour so many liters of methanol and so many of water together and you get less than the expected volume, the molecules fit together that way. Platinum has a speicific gravity of 21.5 and roasted coffee beans .43. ha
http://www.reade.com/Particle_Briefings/spec_gra2.html
The molecular weight of Methanol is 32.04 Ethanol 46.07 Isopropyl 60.1
Note the progression goes up roughly 14 points from methanol to ethanol and from ethanol to isopropyl. Note too that ethanol has an extra CH2 of mass over methanol, and isopropyl too has an extra carbon and 2 hydrogens more than ethanol.
The air fuel ratio for methanol is ~6.4 pounds of air for every pound of methanol, ethanol goes up another ~2.5 points to 9 pounds of air to one of ethanol, and isopropyl I couldn't find an answer.
Here is a formula to calculate air fuel ratios, but I never was any good at math. And I don't know anything about electricity other than it's sneaky. ha
http://www.brighthub.com/engineering/me ... 15235.aspx
2 C3H7OH + 9 O2 = 6 CO2 + 8 H2O or said another way C3H7OH + 4.5 O2 reacts to form 3CO2 + 4 H2O
C2H5OH + 3 O2 =Heat=> 2 CO2 + 3 H2O
2CH3OH + 3O2 -> 2CO2 + 4H2O or CH30H + 1.502 -> CO2 + 2H20
Lastly, the explosive limits for isopropyl alcohol are from 2% - 12.7%, for ethanol the spread gets wider - from 3.3% to 19%, and the least fussy of the three, methanol has a lower explosive limit of 6% and an upper explosive limit of 36%.
PS
I did find this but it just seems too far off to be correct. Maybe they meant 12.4?
4.11 Stoichometric Air to Fuel Ratio: 21.4
(calc.)
http://zenstoves.net/CHRIS/IPA.pdf
PSS
http://en.wikipedia.org/wiki/Heat_of_combustion
Methanol has a formula of CH3OH - Ethanol C2H5OH - Isopropyl C3H7OH.
Specific gravity for these alcohols, say a cubic meter would weigh 790 kg or rather just .79 that of water, water being 1000 kg. There is so little variation in weight per volume that they all round up or down to a specific gravity of .79, it's just the way the marbles pack. I remember an experiment where you pour so many liters of methanol and so many of water together and you get less than the expected volume, the molecules fit together that way. Platinum has a speicific gravity of 21.5 and roasted coffee beans .43. ha
http://www.reade.com/Particle_Briefings/spec_gra2.html
The molecular weight of Methanol is 32.04 Ethanol 46.07 Isopropyl 60.1
Note the progression goes up roughly 14 points from methanol to ethanol and from ethanol to isopropyl. Note too that ethanol has an extra CH2 of mass over methanol, and isopropyl too has an extra carbon and 2 hydrogens more than ethanol.
The air fuel ratio for methanol is ~6.4 pounds of air for every pound of methanol, ethanol goes up another ~2.5 points to 9 pounds of air to one of ethanol, and isopropyl I couldn't find an answer.
Here is a formula to calculate air fuel ratios, but I never was any good at math. And I don't know anything about electricity other than it's sneaky. ha
http://www.brighthub.com/engineering/me ... 15235.aspx
2 C3H7OH + 9 O2 = 6 CO2 + 8 H2O or said another way C3H7OH + 4.5 O2 reacts to form 3CO2 + 4 H2O
C2H5OH + 3 O2 =Heat=> 2 CO2 + 3 H2O
2CH3OH + 3O2 -> 2CO2 + 4H2O or CH30H + 1.502 -> CO2 + 2H20
Lastly, the explosive limits for isopropyl alcohol are from 2% - 12.7%, for ethanol the spread gets wider - from 3.3% to 19%, and the least fussy of the three, methanol has a lower explosive limit of 6% and an upper explosive limit of 36%.
PS
I did find this but it just seems too far off to be correct. Maybe they meant 12.4?
4.11 Stoichometric Air to Fuel Ratio: 21.4
(calc.)
http://zenstoves.net/CHRIS/IPA.pdf
PSS
http://en.wikipedia.org/wiki/Heat_of_combustion
Presentation is Everything
Re: How much thrust?
Hi Mark/everyone, thanks for all the interesting and useful information Mark I was surprised about the petal valve being patented in 1927 I had assumed exactly what you said about the dyna jet being designed after the war and the v1. I now have my ignition working reliably and with a nice big fat spark, it lights up methanol almost instantly, I have been doing some testing but not as much as I would have liked there is just not enough hours in a day, my best thrust figure so far is 2.86lbs this is with methanol a 6 thou reed and a flowjector with 1.6mm metering hole and 1mm cross hole, I tried a flowjector with a 1.3mm cross hole and 1.6mm metering hole, the thrust figure was slightly less and the engine ran roughly, I am going to make a standard petrol size flowjector(.5 cross hole 1mm metering hole) and try petrol again now I have more experience running the engine, I am a bit dissapointed with the thrust figure so far although after weighing my friends airplane the same one I shall build I have worked out that I will have roughly a 1:1 power to weight ratio even with only 2.86lbs thrust. Any ideas or suggestions on what to do to increase thrust gratefully recieved. There is some film of the plane I will build on youtube just type in "kens mini wizz" the plane will need a few mods but it should be ok.