Good question Jerry I am not too sure why they allow the different pipes but I know from reading some old speed times that their was a huge difference in some of the dynajet pipes. I guess earl is a ready source of sport jets at a good price and quality that they let his little mods go through and most of the dynajets when set right go just as well.
On the raven head I will do a bit of reading when I get home from work and see when charlie did most of his work on it. I am not sure but I think Hoyt died well before charlie did all his serious development.
Robert Bolton
jet flight
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noclassmac1972
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larry cottrill
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re: jet flight
noclassmac -
Since you actually fly this stuff in competition, why don't you find out for us what the officials would think about valvless jet engine entries, specifically, how they would handle the issue of the combined areas of tailpipe and rear-facing intakes? Has this ever been brought up before with the AMA? Do you think they would or should set up a different class for valveless powered types?
Another question: What is the current official status of jet-powered scale?
Sorry I am so ignorant, but I have never flown anything in competition, and haven't subscribed to a good modeling magazine in years. I sort of need to get back in the groove ...
L Cottrill
Since you actually fly this stuff in competition, why don't you find out for us what the officials would think about valvless jet engine entries, specifically, how they would handle the issue of the combined areas of tailpipe and rear-facing intakes? Has this ever been brought up before with the AMA? Do you think they would or should set up a different class for valveless powered types?
Another question: What is the current official status of jet-powered scale?
Sorry I am so ignorant, but I have never flown anything in competition, and haven't subscribed to a good modeling magazine in years. I sort of need to get back in the groove ...
L Cottrill
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dynajetjerry
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re: jet flight
Larry,
Insofar as I have heard, valveless pulsejets for AMA contests seem to be a "non-issue." Many such jets use propane as thier fuel, at least for starting, and the associated massive tank greatly reduces their usefulness. (It is possible this situation will change.) Further, valveless types usually have such low specific thrusts (lbs. thrust/lbs. fuel/hr.,) that, within the 1.25 sq. inch tailpipe limit, they would not be competitive with valved engines. As with 4-stroke versus 2-stroke piston engines, perhaps the contest commitee could be persuaded to permit a larger area for valveless types that compete directly with the others, but I suspect a rear facing intake would be considered as part of the exhaust area. With input from valveless afficiandos, the committee would be obliged to waive the 80% methanol/20% propylene oxide fuel requirement.
Generally, I believe pulsejets are permitted in C/L scale competition, only. It is possible the 1.25 in. tailpipe area limit is not applicable, in part because multiple pulsejets MAY be allowed.
During my past conversations with AMA officials, it was made clear to me that SIGs (special interest groups,) must make suggestions through appropriate channels to appropriate individuals and groups, if they hope to expand competition categories. On the other hand, I will not be surprised if outside pressure on the AMA forces that organization to outlaw all noisy engines, especially pulsejets.
Many years ago, I was annoyed by the informal but persuasive opinions of several AMA officials that my pulsejet engine efforts would not be allowed in competition. They opined that, on the other hand, I was free to pursue my efforts outside AMA circles. I feel I did not NEED their permission for that! We can do almost anything we wish if that organization is not involved.
Does this information help anyone?
Jerry
Insofar as I have heard, valveless pulsejets for AMA contests seem to be a "non-issue." Many such jets use propane as thier fuel, at least for starting, and the associated massive tank greatly reduces their usefulness. (It is possible this situation will change.) Further, valveless types usually have such low specific thrusts (lbs. thrust/lbs. fuel/hr.,) that, within the 1.25 sq. inch tailpipe limit, they would not be competitive with valved engines. As with 4-stroke versus 2-stroke piston engines, perhaps the contest commitee could be persuaded to permit a larger area for valveless types that compete directly with the others, but I suspect a rear facing intake would be considered as part of the exhaust area. With input from valveless afficiandos, the committee would be obliged to waive the 80% methanol/20% propylene oxide fuel requirement.
Generally, I believe pulsejets are permitted in C/L scale competition, only. It is possible the 1.25 in. tailpipe area limit is not applicable, in part because multiple pulsejets MAY be allowed.
During my past conversations with AMA officials, it was made clear to me that SIGs (special interest groups,) must make suggestions through appropriate channels to appropriate individuals and groups, if they hope to expand competition categories. On the other hand, I will not be surprised if outside pressure on the AMA forces that organization to outlaw all noisy engines, especially pulsejets.
Many years ago, I was annoyed by the informal but persuasive opinions of several AMA officials that my pulsejet engine efforts would not be allowed in competition. They opined that, on the other hand, I was free to pursue my efforts outside AMA circles. I feel I did not NEED their permission for that! We can do almost anything we wish if that organization is not involved.
Does this information help anyone?
Jerry
re: jet flight
With all the talk and benefits of a valveless engine, I always have this thought in the back of my mind. That is, when you have a valved engine close the gates, it captures the pressure without all the porous sponginess of a valveless engine. When the gate closes, the "hammer effect" compresses/confines the mass more.
Tharratt has gotten over 25 hours at full thrust out of layered valves with neoprene rubber laminated inbetween the reeds, some runs lasting over 7 hours, that's a long time to wait for results, or rather a long time to be cranking out that much noise.
Mark
Tharratt has gotten over 25 hours at full thrust out of layered valves with neoprene rubber laminated inbetween the reeds, some runs lasting over 7 hours, that's a long time to wait for results, or rather a long time to be cranking out that much noise.
Mark
Last edited by Mark on Tue Aug 23, 2005 3:51 pm, edited 1 time in total.
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noclassmac1972
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re: jet flight
well I am not too sure about the AMA situation as I fly in New Zealand but I am in contact with a few fliers.
I checked some of my speed times and Charlie Davis flew a Hoyt raven head but modified it. changing the cowl shape which is meant to increase speed this was copied by earl bailey to create the awesome warrior under Charlies direction.
On the valveless engines I cant see their being a problem as long as they meet the weight and maximum tailpipe dia dimensions. And are able to run on the fuel 80% methanol and 20% Propylene Oxide. I personally dont think they would be that quick but it would be fun to play around with and make some noise..
Cheers
Robert Bolton
I checked some of my speed times and Charlie Davis flew a Hoyt raven head but modified it. changing the cowl shape which is meant to increase speed this was copied by earl bailey to create the awesome warrior under Charlies direction.
On the valveless engines I cant see their being a problem as long as they meet the weight and maximum tailpipe dia dimensions. And are able to run on the fuel 80% methanol and 20% Propylene Oxide. I personally dont think they would be that quick but it would be fun to play around with and make some noise..
Cheers
Robert Bolton
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noclassmac1972
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Re: jet flight
Its been a long time since I posted anything on here. Certaining been having some fun with my pulsejet models. Have been to the US national champs twice and had lots of fun and learned lots. I have a youtube channel now with lots of control line flights on there so feel free to have a look around
Regards
Robert Bolton ( noclassmac1972)
Regards
Robert Bolton ( noclassmac1972)
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dynajetjerry
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Re: jet flight
neoclassmac1972 (Bob Bolton.)
Hi, Bob.You mentioned attending the US Nationals to which I also often go. I live 65 miles from Muncie. If you are here for the Nats this year, make yourself known and maybe we can visit. I may even bring along my pj from the first ever Dyna-Fog Generator and try to fire it up. (Its free length is about 6.5 feet but is uses a valve head assembly that is almost identical to that of a Dyna-Jet. It cycles at 115 cps. Tell me about "tuning" the valve to the tailpipe.)
Hi, Bob.You mentioned attending the US Nationals to which I also often go. I live 65 miles from Muncie. If you are here for the Nats this year, make yourself known and maybe we can visit. I may even bring along my pj from the first ever Dyna-Fog Generator and try to fire it up. (Its free length is about 6.5 feet but is uses a valve head assembly that is almost identical to that of a Dyna-Jet. It cycles at 115 cps. Tell me about "tuning" the valve to the tailpipe.)
Louder is always better.
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noclassmac1972
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Re: jet flight
Hi Jerry I would love to come back to Muncie one day. Last time I was there I managed to win the fastjet title in 2010 being the only non American to do so.. It's going to be all down to finance if I ever make it back.. But if you didn't know Andrew Robinson managed to break his fastjet record here in nz a few weeks back.. I managed to start the engine up straight away and Andrew hung on for a great flight..
http://m.youtube.com/watch?feature=plcp&v=0FiyvtniGbs
Enjoy
Robert Bolton
http://m.youtube.com/watch?feature=plcp&v=0FiyvtniGbs
Enjoy
Robert Bolton
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dynajetjerry
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noclassmac1972
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Re: jet flight
218 mph. Which is a huge jump from his 212mph old record
Robert
Robert
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noclassmac1972
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Re: jet flight
It's been 8 years since I last came to this forum. I am still interested in the planes and make ready to fly models for control line speed for people. Since 2010 have made over 100 kitsets and ready to fly fast/sport pulsejet models for all around the world. It's amazing how one's little interests can make a difference to people. Regards Robert Bolton