Why we don't see pattern planes for gas?
09-30-2009 | 06:34 PM
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From: Houston,
TX
Why we don't see pattern planes for gas?
Hello
I always wanted to know why we dont see any large pattern planes the fly with gasoline engines. I know that a 50cc would be to big to comply with rules but it would certanly make a great plane for practice and people that do not compete. A 30cc should come under 2m and 5kg and would keep operating costs low. I know the ys 170 is a great engine but it is expensive and at $25-30 for a gallon of fuel the operating costs increase dramatically compare to gasoline.
Happy Landings
I always wanted to know why we dont see any large pattern planes the fly with gasoline engines. I know that a 50cc would be to big to comply with rules but it would certanly make a great plane for practice and people that do not compete. A 30cc should come under 2m and 5kg and would keep operating costs low. I know the ys 170 is a great engine but it is expensive and at $25-30 for a gallon of fuel the operating costs increase dramatically compare to gasoline.
Happy Landings
09-30-2009 | 06:47 PM
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From: Adelaide, AUSTRALIA
RE: Why we don't see pattern planes for gas?
I have read about gas engines used in Pattern and I think there is a few issues at the moment . .
1/ current 30cc gas engines have nowhere near enough power for competitive Pattern
2/ a lack of available headers (and perhaps pipes?)
3/ a lack of available soft mounts (which would be desirable in a composite airframe)
4/ a lack of test data and set-ups to copy
Most of the gas engines I have heard about are the ZDZ40F3A . . and I think physical size and weight is an issue with them. . . oh . . and I believe the vibration on the airframe is a little savage?? . .
Cheers, JB
1/ current 30cc gas engines have nowhere near enough power for competitive Pattern
2/ a lack of available headers (and perhaps pipes?)
3/ a lack of available soft mounts (which would be desirable in a composite airframe)
4/ a lack of test data and set-ups to copy
Most of the gas engines I have heard about are the ZDZ40F3A . . and I think physical size and weight is an issue with them. . . oh . . and I believe the vibration on the airframe is a little savage?? . .
Cheers, JB
09-30-2009 | 07:11 PM
#3
RE: Why we don't see pattern planes for gas?
3-4 years ago I put together the Abbra with a 40 cc ZDZ engine. I put together the same model using OS-160, YS-160 and Hacker C-50 since that time. Here is what I found:
1. Gas version was over 11 lbs about 4-5 oz. ES Carbon pipe with custom made soft mount. Initially the engine was hard mounted. The model was almost lost due to flutter in one aileron. The soft mount fixed the problem but added some more weight making practically impossible to get it under 11 lb. The OS model was a little below 10 lbs. The YS-160 was a little over 10 lbs and the electric is ~10.7 lbs.
2. Power. I could not do the Master schedule using the gas engine in the same way I was able to do with all other models. It was very difficult to make the upper radius due to lack of power (or additional weight). The gas engine could very well work for lower levels but I don't think is very practical for Master and F3A.
In conclusion, I tried and found that a gas engine is not feasible for pattern (higher classes). However, lower classes probably could do it but the additional work to find equipment could be a problem. I don't have anything against gas power. If fact I fly IMAC plane using 100 cc and I really like it.
Vicente "Vince" Bortone
1. Gas version was over 11 lbs about 4-5 oz. ES Carbon pipe with custom made soft mount. Initially the engine was hard mounted. The model was almost lost due to flutter in one aileron. The soft mount fixed the problem but added some more weight making practically impossible to get it under 11 lb. The OS model was a little below 10 lbs. The YS-160 was a little over 10 lbs and the electric is ~10.7 lbs.
2. Power. I could not do the Master schedule using the gas engine in the same way I was able to do with all other models. It was very difficult to make the upper radius due to lack of power (or additional weight). The gas engine could very well work for lower levels but I don't think is very practical for Master and F3A.
In conclusion, I tried and found that a gas engine is not feasible for pattern (higher classes). However, lower classes probably could do it but the additional work to find equipment could be a problem. I don't have anything against gas power. If fact I fly IMAC plane using 100 cc and I really like it.
Vicente "Vince" Bortone
09-30-2009 | 07:13 PM
#4
RE: Why we don't see pattern planes for gas?
The "best" powerplant for pattern is the one that makes the most power for the least weight. For IC engines, they will make more power with alcohol than gasoline.
Regards,
Dave
Regards,
Dave
10-01-2009 | 01:43 AM
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From: High Point,
NC
RE: Why we don't see pattern planes for gas?
Enjoy this discussion so I can learn. The IMAC guys use gas but not the F3A guys, ok. Here is a Pattern Plane on Yahoo Japan Auctions with a Saito FG-36.
Chuck
Chuck
10-01-2009 | 02:13 AM
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From: Silverdale,
WA
RE: Why we don't see pattern planes for gas?
Two new engines may shift this paradigm.
The Syssa SAP-180HP is now shipping, is made in CT, weighs around 40 oz including muffler/ignition, and the numbers appear to beat a YS 1.40 and is just about equal to an OS 1.60. It is setup in-line, with a rear-mounted carb. It is quiet at 91 dBa too. $429, rtf. Beautiful engine! http://www.syssaaircraft.com/cart/pc...&idcategory=11
The other is the DL-30. 38 oz RTF, looks pretty impressive on an APC 18x8W prop (8900 rpm). Unfortunately is has a funny side-mounted carb that would make mounting difficult (reed valve crank case side induction). Made in China. $319 shipped. http://www.valleyviewrc.com/DLE-30cc%20gas%20engine.htm
I would be interested to see what they will do with a "pattern" prop like the 18.1x12 used on some larger engines. These numbers are using the included mufflers, of course we could expect a power increase and drop in the noise using a large pipe like the ES Composites. Also with gas we could get away with using a 7 oz fuel tank instead of the larger nitro tanks, so some savings in weight could be had.
The Syssa SAP-180HP is now shipping, is made in CT, weighs around 40 oz including muffler/ignition, and the numbers appear to beat a YS 1.40 and is just about equal to an OS 1.60. It is setup in-line, with a rear-mounted carb. It is quiet at 91 dBa too. $429, rtf. Beautiful engine! http://www.syssaaircraft.com/cart/pc...&idcategory=11
The other is the DL-30. 38 oz RTF, looks pretty impressive on an APC 18x8W prop (8900 rpm). Unfortunately is has a funny side-mounted carb that would make mounting difficult (reed valve crank case side induction). Made in China. $319 shipped. http://www.valleyviewrc.com/DLE-30cc%20gas%20engine.htm
I would be interested to see what they will do with a "pattern" prop like the 18.1x12 used on some larger engines. These numbers are using the included mufflers, of course we could expect a power increase and drop in the noise using a large pipe like the ES Composites. Also with gas we could get away with using a 7 oz fuel tank instead of the larger nitro tanks, so some savings in weight could be had.
10-01-2009 | 02:50 AM
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From: Oulu, FINLAND
RE: Why we don't see pattern planes for gas?
I have been flying MVVS 26 + pipe in a 2x2 stunt for a while and I am also looking for a little more punch.
DL30 seems to have around 3hp without pipe so not much more power without pipe(MSS with pipe has a bit more actually). Side carb is big no no.
Syssa seems to be nice rear carb, rear exhaust engine, but there are so few user reports that I will wait for those.
Generally all these engines need a pipe and modern pattern planes don't come with pipe tunnels anymore. They are designed for short Hatori headers and that's it.
I hope YS announces 200 CDI gasser soon
DL30 seems to have around 3hp without pipe so not much more power without pipe(MSS with pipe has a bit more actually). Side carb is big no no.
Syssa seems to be nice rear carb, rear exhaust engine, but there are so few user reports that I will wait for those.
Generally all these engines need a pipe and modern pattern planes don't come with pipe tunnels anymore. They are designed for short Hatori headers and that's it.
I hope YS announces 200 CDI gasser soon
10-01-2009 | 07:01 AM
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From: Perth, AUSTRALIA
RE: Why we don't see pattern planes for gas?
I too have been flying with the mvvs 26 on pipe, and while it's quite powerful, I'd say it's as good as a poorly set up 140 rx.
What we really need to see is a modern schneulre ported, rear ROTOR (not reed) rear exhaust 30-35cc Petrol engine, that's LIGHT LIGHT LIGHT! possible? Oh my word yes.
Economically viable, well that's the toughy.
What we really need to see is a modern schneulre ported, rear ROTOR (not reed) rear exhaust 30-35cc Petrol engine, that's LIGHT LIGHT LIGHT! possible? Oh my word yes.
Economically viable, well that's the toughy.
10-01-2009 | 08:03 AM
#9
RE: Why we don't see pattern planes for gas?
Dave,
Probably the reason is explained in this web site:
http://www.smokemup.com/tech/fuels.php
They compare the gasoline, methanol and nitromethane. Probably the information gives a good reasons why we use nitro in glow fuels. The table 1 gives the total energy that could be delivered by IC engine for each fuel. Clearly gasoline is the lowest one and probably this is a good explanation why it does not work well in small displacement IC engines. Her the numbers from table I:
Total Thermal Energy delivered in IC engine (BTU)
Gasoline 53,176
Methanol 67,545
Nitromethane 125,412
Vicente "Vince" Bortone
Probably the reason is explained in this web site:
http://www.smokemup.com/tech/fuels.php
They compare the gasoline, methanol and nitromethane. Probably the information gives a good reasons why we use nitro in glow fuels. The table 1 gives the total energy that could be delivered by IC engine for each fuel. Clearly gasoline is the lowest one and probably this is a good explanation why it does not work well in small displacement IC engines. Her the numbers from table I:
Total Thermal Energy delivered in IC engine (BTU)
Gasoline 53,176
Methanol 67,545
Nitromethane 125,412
Vicente "Vince" Bortone
10-01-2009 | 08:35 AM
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From: Tomball,
TX
RE: Why we don't see pattern planes for gas?
Here is a link to an interesting and quite successful gas pattern plane project:
http://www.rcuniverse.com/forum/m_85...tm.htm#8573705
Richard
http://www.rcuniverse.com/forum/m_85...tm.htm#8573705
Richard
10-01-2009 | 08:48 AM
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RE: Why we don't see pattern planes for gas?
ORIGINAL: Kema
I hope YS announces 200 CDI gasser soon
I hope YS announces 200 CDI gasser soon
10-01-2009 | 08:57 AM
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RE: Why we don't see pattern planes for gas?
I think they've about maxed the bore out on these motors. The next size up will likely have to have a larger physical case and cylinder.
10-01-2009 | 09:23 AM
#13
RE: Why we don't see pattern planes for gas?
Vince,
Thanks for posting BTU numbers. Bottom line is that no matter how light and efficient a gasoline engine is, more power is still available by running alcohol (especially when nitro is added). The benefits generally realized by spark ignition gasoline engines vs glow alcohol engines is the ability to more accurately control the combustion - spark can be adjusted to be at the optimal time at any RPM, and will occur more accurately and consistently - this lends to better fuel economy/efficiency. This is exactly why glow engines converted to gas don't make as much power, and why glow engines converted to spark ignition (ie, YS 170 CDI) make more power.
Regards,
Dave
Thanks for posting BTU numbers. Bottom line is that no matter how light and efficient a gasoline engine is, more power is still available by running alcohol (especially when nitro is added). The benefits generally realized by spark ignition gasoline engines vs glow alcohol engines is the ability to more accurately control the combustion - spark can be adjusted to be at the optimal time at any RPM, and will occur more accurately and consistently - this lends to better fuel economy/efficiency. This is exactly why glow engines converted to gas don't make as much power, and why glow engines converted to spark ignition (ie, YS 170 CDI) make more power.
Regards,
Dave
ORIGINAL: vbortone
Dave,
Probably the reason is explained in this web site:
http://www.smokemup.com/tech/fuels.php
They compare the gasoline, methanol and nitromethane. Probably the information gives a good reasons why we use nitro in glow fuels. The table 1 gives the total energy that could be delivered by IC engine for each fuel. Clearly gasoline is the lowest one and probably this is a good explanation why it does not work well in small displacement IC engines. Her the numbers from table I:
Total Thermal Energy delivered in IC engine (BTU)
Gasoline 53,176
Methanol 67,545
Nitromethane 125,412
Vicente ''Vince'' Bortone
Dave,
Probably the reason is explained in this web site:
http://www.smokemup.com/tech/fuels.php
They compare the gasoline, methanol and nitromethane. Probably the information gives a good reasons why we use nitro in glow fuels. The table 1 gives the total energy that could be delivered by IC engine for each fuel. Clearly gasoline is the lowest one and probably this is a good explanation why it does not work well in small displacement IC engines. Her the numbers from table I:
Total Thermal Energy delivered in IC engine (BTU)
Gasoline 53,176
Methanol 67,545
Nitromethane 125,412
Vicente ''Vince'' Bortone
10-01-2009 | 09:41 AM
#14
RE: Why we don't see pattern planes for gas?
Dave,
There is something that I cannot explain. The practical limit for glow engines is probably around 2 cu.in. Over that displacement the glow engines are not reliable. In contrast, when gasoline engines are over ~85 cc they start to shine vs. glow engine. I have been flying a DA - 100 in the last 3-4 years. This engine has more than 500 flights and still running great. There is something in the combustion process when glow engines are too big (or carburetion) that I cannot explain. That is probably why the glow engines over 2 cu.in. are not popular (besides the cost of fuel). Probably someone expert in combustion could explain.
Regards,
Vicente "Vince" Bortone
There is something that I cannot explain. The practical limit for glow engines is probably around 2 cu.in. Over that displacement the glow engines are not reliable. In contrast, when gasoline engines are over ~85 cc they start to shine vs. glow engine. I have been flying a DA - 100 in the last 3-4 years. This engine has more than 500 flights and still running great. There is something in the combustion process when glow engines are too big (or carburetion) that I cannot explain. That is probably why the glow engines over 2 cu.in. are not popular (besides the cost of fuel). Probably someone expert in combustion could explain.
Regards,
Vicente "Vince" Bortone
10-01-2009 | 09:44 AM
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RE: Why we don't see pattern planes for gas?
I would love to see a 35% or 40% pattern plane. I know that it wouldn't be legal for pattern or IMAC, but how cool would it be to see like a 126 inch x 126 inch 150CC Integral! I know it will never happen and it is probably a little off topic but I think that would be great 
10-01-2009 | 11:49 AM
#17
RE: Why we don't see pattern planes for gas?
It is interesting to see that a glow engine using 20% fuel is 1.48 (148%) more powerful than a gas engine under equivalent conditions assuming that BTU information is correct. I think the numbers makes sense base on the experience I had flying the same model with all options.
VB
VB
10-01-2009 | 01:31 PM
#18
RE: Why we don't see pattern planes for gas?
ORIGINAL: AAbdu
I would love to see a 35% or 40% pattern plane. I know that it wouldn't be legal for pattern or IMAC, but how cool would it be to see like a 126 inch x 126 inch 150CC Integral! I know it will never happen and it is probably a little off topic but I think that would be great
I would love to see a 35% or 40% pattern plane. I know that it wouldn't be legal for pattern or IMAC, but how cool would it be to see like a 126 inch x 126 inch 150CC Integral! I know it will never happen and it is probably a little off topic but I think that would be great
10-01-2009 | 01:57 PM
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From: Silverdale,
WA
RE: Why we don't see pattern planes for gas?
It is interesting to see that a glow engine using 20% fuel is 1.48 (148%) more powerful than a gas engine under equivalent conditions assuming that BTU information is correct
This stands to reason. The chemical breakdown of the fuel into CO2 and H2O is what releases the energy. Gasoline has more chemical bonds to break down per molecule, thus releasing significantly more energy per complete combustion cycle. FWIW diesel fuel has significantly more power per unit mass than gasoline due to the even longer carbon chains.
As always, the balancing act is in burning the sufficient amount of gas to make the amount of power we need. Of course this requires a somewhat larger engine because we need to pump more air in the same amount of time. After this we have many other considerations including port timing, compression ratios, induction method (preferably a rotary drum as mentioned by Renegade above).
Here is the problem. None of the gasoline engines on the market really maximize the power available to them. On the nitro side the new YS 1.70cdi may be the (current) pinnacle of efficiency, having both supercharged induction and electronic ignition to control the start of combustion. The YS engine becomes more fuel efficient with the EI. This proves (to me) that there is quite a bit of efficiency to be gained with a few improvements.
LCHeliover built a Pentathlon and now a Black Magic and converted his piped OS 1.60 to gasoline. He noted a similar RPM value as on the nitro version (around 7850 on an APC 18.1x10) but it now has an extremely reliable idle and the EI should completely eliminate deadsticks. He notes the power isn't quite up to the YS 1.70 levels however.
I have to wonder how an OS 2.10AX (theoretical engine, wishful thinking!) would work converted to gasoline/EI. The 1.60FX seems to work sufficiently, especially on the smaller/lighter/streamlined older planes. For instance the OS 1.60 would be a gross excess of power on my 11 year old Zimpro Viper 2m, but would be barely enough for a new Black Magic V3 or other large, draggy, modern pattern plane.
I am not confident we could easily convert a 4-stroke engine to gasoline the way the OS 2-stroke engine can be converted without running into preignition issues, and we know the YS diaphragms and gaskets won't play nicely with petroleum-based compounds.
I have to admit the thought of burning 15 gallons of gas at $3.75 (including oil, etc) vice burning the 22 or so gallons at ~$27/gallon for 30% heli fuel for the same number of flights is HIGHLY interesting. Who wouldn't want to save $500+ dollars on the fuel bill in a season?
10-01-2009 | 02:05 PM
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From: Silverdale,
WA
RE: Why we don't see pattern planes for gas?
RE: "Old School" pattern planes blown up for gas engines - I don't have a link right here, but somewhere on Youtube there is a video of a ~90-100" ws Tiporare on a gas engine. I think it used a Zenoah G62 engine, and seemed to fly very well. As I recall the video was filmed back in the early 90's sometime. That would be fun!
10-01-2009 | 02:10 PM
#21
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RE: Why we don't see pattern planes for gas?
I actually worked on a UAV project a few years ago in which we took a YS 1.60DZ, converted it to gas by changing all the o-rings and such and then running it on ignition (C&H). The engine would run, but was certainly not very powerful. It took a lot of playing to get the timing correct. The biggest problem we had was cooling. We had to run quite a bit of oil to keep the engine even semi cool, and it would still regularly overheat. Eventually we abandoned the idea and ran Evolution 35's instead. Was neat to play with though.
As for the Pentathalon that George Miller had with the OS 1.60 converted to gas. The performance was OK. The Pentathalon is not a very draggy airframe to start with, and it was adequate for Advanced. I don't think it would've been a competitive setup in Masters or FAI, but was a very nice proof of concept. Had a very distinctive sound in the air as well. He did have a few deadsticks however, but the idea did work, but was certainly not a competitive setup by todays standards.
Arch
As for the Pentathalon that George Miller had with the OS 1.60 converted to gas. The performance was OK. The Pentathalon is not a very draggy airframe to start with, and it was adequate for Advanced. I don't think it would've been a competitive setup in Masters or FAI, but was a very nice proof of concept. Had a very distinctive sound in the air as well. He did have a few deadsticks however, but the idea did work, but was certainly not a competitive setup by todays standards.
Arch
10-01-2009 | 02:41 PM
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From: Silverdale,
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RE: Why we don't see pattern planes for gas?
Sorry to post again in here, but I have a question and an observation.
What are the reasons we are interested in using a gasoline engine?
I can think of two major reasons: 1) the obvious price differential between gas and glow fuel, and 2) the reliability gained by fully controlling the ignition point using the electronic ignition.
Here is a possible alternative: E85. This is a fuel made of 85% ethanol and 15% gasoline. It happens to be available locally for the 'Beautiful People" here in Seattle, the land of fruits and nuts, to "Save the environment" in their flex fuel SUV's and pat their egos. Go figure...
Anyway, I can get it for around $2.40/gallon last time I checked. Being ethanol, it is a higher octane fuel and thus more resistant to detonation than gasoline, but with the higher flow rates should produce more power on a specific engine than gasoline would. It would also provide a significant amount of cooling as the ethanol absorbs a great amount of heat to vaporize (not as much as methanol, but more than gas by a long shot).
Cheap ignition units are easily available now. The RC EXL ignition with a 1/4-32 spark plug can be had for ~$85 or so and is a copy of the excellent CH Ignitions Synchro Spark. It retards the timing at lower RPM so the idle is smoother and starting is easy (NO kickbacks!).
Again the biggest problem of converting a glow engine to gas is the bushed connecting rod. It sure would be nice if somebody made a conn rod with a pair of roller bearings for some of these engines...Of course that would be fairly expensive.
Now if only OS would make a solid, LIGHT, durable 2.0 cu in 2-stroke! That would likely match or beat a YS 1.60dz.
What are the reasons we are interested in using a gasoline engine?
I can think of two major reasons: 1) the obvious price differential between gas and glow fuel, and 2) the reliability gained by fully controlling the ignition point using the electronic ignition.
Here is a possible alternative: E85. This is a fuel made of 85% ethanol and 15% gasoline. It happens to be available locally for the 'Beautiful People" here in Seattle, the land of fruits and nuts, to "Save the environment" in their flex fuel SUV's and pat their egos. Go figure...
Anyway, I can get it for around $2.40/gallon last time I checked. Being ethanol, it is a higher octane fuel and thus more resistant to detonation than gasoline, but with the higher flow rates should produce more power on a specific engine than gasoline would. It would also provide a significant amount of cooling as the ethanol absorbs a great amount of heat to vaporize (not as much as methanol, but more than gas by a long shot).
Cheap ignition units are easily available now. The RC EXL ignition with a 1/4-32 spark plug can be had for ~$85 or so and is a copy of the excellent CH Ignitions Synchro Spark. It retards the timing at lower RPM so the idle is smoother and starting is easy (NO kickbacks!).
Again the biggest problem of converting a glow engine to gas is the bushed connecting rod. It sure would be nice if somebody made a conn rod with a pair of roller bearings for some of these engines...Of course that would be fairly expensive.
Now if only OS would make a solid, LIGHT, durable 2.0 cu in 2-stroke! That would likely match or beat a YS 1.60dz.
10-01-2009 | 02:45 PM
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From: Houston,
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RE: Why we don't see pattern planes for gas?
ORIGINAL: BTerry
No this is completely backwards - although in practice the nitro engine produces more power, as per your experience . Gasoline has a much higher SPECIFIC thermal energy (BTU/lb of fuel) than the other mixtures when based on the volume of the fuel itself. Nitromethane and methanol produce more power SOLELY BECAUSE they burn so much more of it. Gasoline has more than TWICE the amount of energy per unit as methanol, but produces 20% more ''work'' in the engine by burning 2.5 times the amount of fuel. In the example above the 355 SBC burns 2.89 lbs of gas to produce 53,176 BTU while the combustion of 7.11 lbs of methanol produces 67,545 BTU and nitromethane burns 25.8 lbs to generate 125,412 BTU. By corrolary, we could expect to burn 3.5 lbs of gas to generate 67,545 BTU of the methanol and 6.89 lbs of gas to generate the 125,412 BTU of the nitromethane example.
This stands to reason. The chemical breakdown of the fuel into CO2 and H2O is what releases the energy. Gasoline has more chemical bonds to break down per molecule, thus releasing significantly more energy per complete combustion cycle. FWIW diesel fuel has significantly more power per unit mass than gasoline due to the even longer carbon chains.
As always, the balancing act is in burning the sufficient amount of gas to make the amount of power we need. Of course this requires a somewhat larger engine because we need to pump more air in the same amount of time. After this we have many other considerations including port timing, compression ratios, induction method (preferably a rotary drum as mentioned by Renegade above).
Here is the problem. None of the gasoline engines on the market really maximize the power available to them. On the nitro side the new YS 1.70cdi may be the (current) pinnacle of efficiency, having both supercharged induction and electronic ignition to control the start of combustion. The YS engine becomes more fuel efficient with the EI. This proves (to me) that there is quite a bit of efficiency to be gained with a few improvements.
LCHeliover built a Pentathlon and now a Black Magic and converted his piped OS 1.60 to gasoline. He noted a similar RPM value as on the nitro version (around 7850 on an APC 18.1x10) but it now has an extremely reliable idle and the EI should completely eliminate deadsticks. He notes the power isn't quite up to the YS 1.70 levels however.
I have to wonder how an OS 2.10AX (theoretical engine, wishful thinking!) would work converted to gasoline/EI. The 1.60FX seems to work sufficiently, especially on the smaller/lighter/streamlined older planes. For instance the OS 1.60 would be a gross excess of power on my 11 year old Zimpro Viper 2m, but would be barely enough for a new Black Magic V3 or other large, draggy, modern pattern plane.
I am not confident we could easily convert a 4-stroke engine to gasoline the way the OS 2-stroke engine can be converted without running into preignition issues, and we know the YS diaphragms and gaskets won't play nicely with petroleum-based compounds.
I have to admit the thought of burning 15 gallons of gas at $3.75 (including oil, etc) vice burning the 22 or so gallons at ~$27/gallon for 30% heli fuel for the same number of flights is HIGHLY interesting. Who wouldn't want to save $500+ dollars on the fuel bill in a season?
It is interesting to see that a glow engine using 20% fuel is 1.48 (148%) more powerful than a gas engine under equivalent conditions assuming that BTU information is correct
This stands to reason. The chemical breakdown of the fuel into CO2 and H2O is what releases the energy. Gasoline has more chemical bonds to break down per molecule, thus releasing significantly more energy per complete combustion cycle. FWIW diesel fuel has significantly more power per unit mass than gasoline due to the even longer carbon chains.
As always, the balancing act is in burning the sufficient amount of gas to make the amount of power we need. Of course this requires a somewhat larger engine because we need to pump more air in the same amount of time. After this we have many other considerations including port timing, compression ratios, induction method (preferably a rotary drum as mentioned by Renegade above).
Here is the problem. None of the gasoline engines on the market really maximize the power available to them. On the nitro side the new YS 1.70cdi may be the (current) pinnacle of efficiency, having both supercharged induction and electronic ignition to control the start of combustion. The YS engine becomes more fuel efficient with the EI. This proves (to me) that there is quite a bit of efficiency to be gained with a few improvements.
LCHeliover built a Pentathlon and now a Black Magic and converted his piped OS 1.60 to gasoline. He noted a similar RPM value as on the nitro version (around 7850 on an APC 18.1x10) but it now has an extremely reliable idle and the EI should completely eliminate deadsticks. He notes the power isn't quite up to the YS 1.70 levels however.
I have to wonder how an OS 2.10AX (theoretical engine, wishful thinking!) would work converted to gasoline/EI. The 1.60FX seems to work sufficiently, especially on the smaller/lighter/streamlined older planes. For instance the OS 1.60 would be a gross excess of power on my 11 year old Zimpro Viper 2m, but would be barely enough for a new Black Magic V3 or other large, draggy, modern pattern plane.
I am not confident we could easily convert a 4-stroke engine to gasoline the way the OS 2-stroke engine can be converted without running into preignition issues, and we know the YS diaphragms and gaskets won't play nicely with petroleum-based compounds.
I have to admit the thought of burning 15 gallons of gas at $3.75 (including oil, etc) vice burning the 22 or so gallons at ~$27/gallon for 30% heli fuel for the same number of flights is HIGHLY interesting. Who wouldn't want to save $500+ dollars on the fuel bill in a season?
Gasoline has a higher BTU that either methanol or nitromethane. methanol produces more power simply because it is using almost 3 times the amount of fuel. All you need to get more power from a gas engine is to increase the amount of oxygen used. This could be easily accomplished by increasing the size of the combustion chamber, an OS 2.10 AX should be able to accomplish this. Also I believe manufacturers have not maxed out the bore of engines, i.e. evolution just came out with a .60 nx with the same size as a standard .40 that is 150% more displacement for the same aluminum block.
an evolution 40nt has a stroke of .77 in and a bore of .81in
the new evo 60nx has a stroke of .85 in and a bore of .95 in
10-01-2009 | 03:49 PM
#24
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From: Tomball,
TX
RE: Why we don't see pattern planes for gas?
ORIGINAL: rcpattern
The Pentathalon is not a very draggy airframe to start with, and it was adequate for Advanced. I don't think it would've been a competitive setup in Masters or FAI, but was a very nice proof of concept. Had a very distinctive sound in the air as well. He did have a few deadsticks however, but the idea did work, but was certainly not a competitive setup by todays standards.
Arch
The Pentathalon is not a very draggy airframe to start with, and it was adequate for Advanced. I don't think it would've been a competitive setup in Masters or FAI, but was a very nice proof of concept. Had a very distinctive sound in the air as well. He did have a few deadsticks however, but the idea did work, but was certainly not a competitive setup by todays standards.
Arch
]The Pentathlon is draggier than you think. Just because it does have the bloated fuselage of some of it's contemporaries, does not mean it does not have a nice drag profile. The Pentathlon derives it's parasitic drag from the flying surface design. I hope to see more of the OS160 Gas model this weekend and hopefullly we can get someone to fly it through the FAI P sequence to see what kind of muscle the OS160 can really muster.
Richard
10-01-2009 | 05:27 PM
#25
RE: Why we don't see pattern planes for gas?
Bterry,
Please read this web page for the very simple and interesting conclusion:
http://www.smokemup.com/tech/fuels.php
One number is BTU/lb and I agree gasoline has higher number. However, the IC engine can convert to power a fraction of those BTU because of the oxygen already available in the fuel. Check the chemical formulas of each fuel. Gasoline does not have any oxygen. It is practically impossible to provide all the oxygen by aspirating air into the engine and this explain why gasoline has the lowest BTU rate production (power) when used in IC engine.
Vicente "Vince" Bortone
Please read this web page for the very simple and interesting conclusion:
http://www.smokemup.com/tech/fuels.php
One number is BTU/lb and I agree gasoline has higher number. However, the IC engine can convert to power a fraction of those BTU because of the oxygen already available in the fuel. Check the chemical formulas of each fuel. Gasoline does not have any oxygen. It is practically impossible to provide all the oxygen by aspirating air into the engine and this explain why gasoline has the lowest BTU rate production (power) when used in IC engine.
Vicente "Vince" Bortone
