Bonner Smog Hog - 60 years later
05-24-2016, 05:39 PM
#27
Servos for this project. As far as I know, these represent Bonner's 2nd generation servo design. The first servos were called the "mailbox" servo, hopefully for not having to send them in for repair, but because the top of the case was curved like a mailbox. However this was what he sold in 1956 to about 1959. Each servo is about 2" wide, 3" long, and about 1 1/2" tall. There were other servo manufacturers of reed servos, but Bonner seemed to outlast them all in the number of years he made these things. They were replaced by the Duramite which also needed relays, until the Transmite which eliminated the heavy relays with about a half dozen transistors. No wonder people were surprised when the Bonner proportional came out. The guy that designed the servo amplifier for Bonner went on to design the Logictrol line of radios. Memory don't fail me now.
05-25-2016, 10:33 AM
#29
Bonner made all sorts of control horns, keepers, clevises and assorted hinges and hardware items for R/C. Rocket City Specialties, and later DuBro took over where he left off.
About Phil Krafts Ugly Stick: Phil was a great imitator, and he learned quite well by observing the best. Zel Ritchie flew every Space Control system prior to shipping it out. He built a test plane with a box fuselage made from 1/4" balsa, shoulder wing, it was called "the Stick" and was not very pretty. It was designed so you could quickly change out the airborne electronics, and he made several of them for testing his radios. Phil saw it and took the idea one step further by having Jensen kit and build them. This was because Phil needed planes to test his first proportional radios in.
The tube radios of the day typically did not run hot because of the low voltage filaments. Most of the tubes used 1.5 volts, or 3 volt filaments, and only the final output tube (3A5) drew any appreciable power. Total dissipation was typically under a couple watts. The filaments glowed so dimly, you had to take the radio into a completely dark room to see them glowing.
Howard Bonner was just a half semester and one final exam away from getting his mechanical engineering degree at USC when he quit school to fill an order for 300 actuators from Vernon McNabb, the owner of Citizen-Ship. He set up his garage at his Tilden St home in Santa Monica as a small manufacturing facility and hired several people to build the actuators. Eventually Howard got into making small detailed injection molded parts to simplify the manufacturing of his escapements, and later, his servos. Bonner became well known for his ability to accurately mold details, like gears, into small plastic parts. At the time, this was a new phenomena, and so he received a lot of orders from the aerospace companies for specially made plastic parts.
And yes, Bob Elliot did design the Transmite servo amplifier for Bonner in 1959. Howard purchased the basic design of what was to become the Digimite 8 from Gordon Larson, and Frank Kagele, who were both working at Babcock at the time (1960). He showed Bob Elliot the schematics and asked him to look it over and do any revisions or additions he though would be needed to improve, and simplify the design. In the mean time, he retained Larson and Kagele to continue developing the design. Well, is it no big surprise that within a month of seeing this revolutionary design, that Bob Elliot ended his relationship with Bonner and released his first EK Logictrol radios almost about the same time that the Digimite came out? Industrial espionage, spearheaded by non other than Bob Elliot in this case.
Monokote was replaced by Super Monokote, which did not get loose when it got hot in the sun.
About Phil Krafts Ugly Stick: Phil was a great imitator, and he learned quite well by observing the best. Zel Ritchie flew every Space Control system prior to shipping it out. He built a test plane with a box fuselage made from 1/4" balsa, shoulder wing, it was called "the Stick" and was not very pretty. It was designed so you could quickly change out the airborne electronics, and he made several of them for testing his radios. Phil saw it and took the idea one step further by having Jensen kit and build them. This was because Phil needed planes to test his first proportional radios in.
The tube radios of the day typically did not run hot because of the low voltage filaments. Most of the tubes used 1.5 volts, or 3 volt filaments, and only the final output tube (3A5) drew any appreciable power. Total dissipation was typically under a couple watts. The filaments glowed so dimly, you had to take the radio into a completely dark room to see them glowing.
Howard Bonner was just a half semester and one final exam away from getting his mechanical engineering degree at USC when he quit school to fill an order for 300 actuators from Vernon McNabb, the owner of Citizen-Ship. He set up his garage at his Tilden St home in Santa Monica as a small manufacturing facility and hired several people to build the actuators. Eventually Howard got into making small detailed injection molded parts to simplify the manufacturing of his escapements, and later, his servos. Bonner became well known for his ability to accurately mold details, like gears, into small plastic parts. At the time, this was a new phenomena, and so he received a lot of orders from the aerospace companies for specially made plastic parts.
And yes, Bob Elliot did design the Transmite servo amplifier for Bonner in 1959. Howard purchased the basic design of what was to become the Digimite 8 from Gordon Larson, and Frank Kagele, who were both working at Babcock at the time (1960). He showed Bob Elliot the schematics and asked him to look it over and do any revisions or additions he though would be needed to improve, and simplify the design. In the mean time, he retained Larson and Kagele to continue developing the design. Well, is it no big surprise that within a month of seeing this revolutionary design, that Bob Elliot ended his relationship with Bonner and released his first EK Logictrol radios almost about the same time that the Digimite came out? Industrial espionage, spearheaded by non other than Bob Elliot in this case.
Monokote was replaced by Super Monokote, which did not get loose when it got hot in the sun.
Last edited by jaymen; 05-25-2016 at 11:03 AM.
05-25-2016, 08:18 PM
#30
Bob Elliot (the E in EK) may have seen the circuit drawings for the Larson/Kagele design, but it would appear that he chose a different pulse scheme (no double pulse), and his servo amplifier was also different. EK went on to several firsts in the industry, perhaps the most significant being the three wire servo along with the two wire battery around 1968. The other was the first dual conversion receiver. Neither was totally groundbreaking, bridged motor drivers and dual conversion techniques were well known among electrical engineers, but getting it in a useable form for modelers took some effort.
A lot of circuits got shared, they were even published at events like the DCRC annual symposium. It was pretty evident that Howard Bonner wanted a feedback proportional system, starting with Al Doig's Ulti multi analog system that Howard designed the stick for and made parts for the servos from the servo I showed in post 27. To fit the electronics into the servo, it was made and inch longer (that would be 4" long, yikes!). Was this the first three proportional, one positional radio? I know that another guy around 1957 built a two channel feedback proportional in 1957. A lot of guys, a lot of experiments. Would Space Control even got off the ground if Mathes didn't build a functional receiver? While he was working for them, he was also designing the DM reed set that Spreng used to win the Nat's twice. This design became the Dean's reed system. Sadly these questions should have been asked 50 years ago.
I've always said that it was a short distance from reed designs to analog proportional systems. Replace a switch with a pot and you have a variable tone. Throw away the reed bank and replace with a frequency discriminator and you have a control voltage. The servo drive could not be simpler. But as they designers soon found, Intermodulation distortion was a b..itch as they added channels. So time sharing of tones were used by some, but then you start thinking that just pulses might be easier.
Good tips on the tube technology. By the time I took the electrical engineering courses, tubes were a footnote in history for 99% of designers. I spend my time on analog instrumentation, CMOS, and RF. How that got me into military airborne Radar I will never understand. Probing a 30 KV TWT power supply is nothing I ever one to do again. But one thing leads to another, and a long stint at a communications lab and short one at a weapons plant finally put me into semiconductor capital equipment. Possibly the most fun you could possibly have in an R&D environment.
A lot of circuits got shared, they were even published at events like the DCRC annual symposium. It was pretty evident that Howard Bonner wanted a feedback proportional system, starting with Al Doig's Ulti multi analog system that Howard designed the stick for and made parts for the servos from the servo I showed in post 27. To fit the electronics into the servo, it was made and inch longer (that would be 4" long, yikes!). Was this the first three proportional, one positional radio? I know that another guy around 1957 built a two channel feedback proportional in 1957. A lot of guys, a lot of experiments. Would Space Control even got off the ground if Mathes didn't build a functional receiver? While he was working for them, he was also designing the DM reed set that Spreng used to win the Nat's twice. This design became the Dean's reed system. Sadly these questions should have been asked 50 years ago.
I've always said that it was a short distance from reed designs to analog proportional systems. Replace a switch with a pot and you have a variable tone. Throw away the reed bank and replace with a frequency discriminator and you have a control voltage. The servo drive could not be simpler. But as they designers soon found, Intermodulation distortion was a b..itch as they added channels. So time sharing of tones were used by some, but then you start thinking that just pulses might be easier.
Good tips on the tube technology. By the time I took the electrical engineering courses, tubes were a footnote in history for 99% of designers. I spend my time on analog instrumentation, CMOS, and RF. How that got me into military airborne Radar I will never understand. Probing a 30 KV TWT power supply is nothing I ever one to do again. But one thing leads to another, and a long stint at a communications lab and short one at a weapons plant finally put me into semiconductor capital equipment. Possibly the most fun you could possibly have in an R&D environment.
Last edited by HighPlains; 05-25-2016 at 10:26 PM.
05-27-2016, 09:45 AM
#31
Yeah, Mathes was one of the ramrods without which, we would not have seen such rapid activity and development here in Southern California. The JPL connection via Jerry Pullen also is a large denominator, as they had the missile guidance technology, but it was too big and heavy for models. Pulse, reeds, and analog proportional guidance systems were well known and used by the military for drones, and weapons guidance.
Have you ever seen a KD2R5 Shelduck's radio system? It was made by Radioplane/Northrup. The company was started by Reginald Denny.
Interestingly, Hershel related that he was having trouble with the Space Controls solid state super-het receiver, it lacked good range. Mathes put a super-regen, tube type front end on it, and that resulted in the first successful test flight of the SC system. They were able to return to the transistorized super-het receiver design after developing transistor gain and leakage test fixtures to grade and select good transistors.
When I was in the USARMY, out ATC equipment was a blend of three technologies: Tube, Solid State, and Hybrid (tube and solid state). Some of the equipment used SMT, micro-chips, and frequency synthesis, while some of it was older and all tube, but fixed site and dedicated, so we had to maintain it. Our Wilcox NDB dated from the 1940s, and was one of the most reliable Navaids at Libby AAF.
Undoubtedly, Elliot saw the Digicon, whose release predated the Digimite and Logictrol. It used the PPM format we still use today, so everyone adopted it. The fact that it used half the transistors was huge, because transistors back then were quite expensive. To deal with that, RC manufacturers would buy ungraded, and untested transistors in bulk from semiconductor manufacturers at a huge discount, and then sort through them and grade them accordingly. This was the only way they could reduce the costs significantly enough to get below the $400 retail price for a full house system. The thinking of that era was the more parts, the more possibility of failure, plus reducing parts count reduced costs as well.
The Mathes/Spreng team designed R/C systems for Orbit, Deans, Kraft, Micro-Avionics, Omni, Cannon(digicon II) and RS Systems, plus many more. Their influence was very significant, and on the level of the Good brothers as far as affecting the R/C hobby.
Have you ever seen a KD2R5 Shelduck's radio system? It was made by Radioplane/Northrup. The company was started by Reginald Denny.
Interestingly, Hershel related that he was having trouble with the Space Controls solid state super-het receiver, it lacked good range. Mathes put a super-regen, tube type front end on it, and that resulted in the first successful test flight of the SC system. They were able to return to the transistorized super-het receiver design after developing transistor gain and leakage test fixtures to grade and select good transistors.
When I was in the USARMY, out ATC equipment was a blend of three technologies: Tube, Solid State, and Hybrid (tube and solid state). Some of the equipment used SMT, micro-chips, and frequency synthesis, while some of it was older and all tube, but fixed site and dedicated, so we had to maintain it. Our Wilcox NDB dated from the 1940s, and was one of the most reliable Navaids at Libby AAF.
Undoubtedly, Elliot saw the Digicon, whose release predated the Digimite and Logictrol. It used the PPM format we still use today, so everyone adopted it. The fact that it used half the transistors was huge, because transistors back then were quite expensive. To deal with that, RC manufacturers would buy ungraded, and untested transistors in bulk from semiconductor manufacturers at a huge discount, and then sort through them and grade them accordingly. This was the only way they could reduce the costs significantly enough to get below the $400 retail price for a full house system. The thinking of that era was the more parts, the more possibility of failure, plus reducing parts count reduced costs as well.
The Mathes/Spreng team designed R/C systems for Orbit, Deans, Kraft, Micro-Avionics, Omni, Cannon(digicon II) and RS Systems, plus many more. Their influence was very significant, and on the level of the Good brothers as far as affecting the R/C hobby.
05-27-2016, 10:39 AM
#33
I have stored a lot of material for this project over the years, include the original MAN magazine with the Smog Hog article. But I don't organize too well, so it remains mia. But from the Outerzone site, I discovered that the magazine plan sheet was on RC Groups, and it displays at a much higher resolution.
http://www.rcgroups.com/forums/showa...3&d=1293050302
From this I was able to see that Howard used the BRAMCO throttle. He used this with a Fox .35 and an 11/6 prop, most likely a TopFlite based on it's blade shape. Here are pictures of a NIB BRAMCO throttle. About the only similarity to a modern carb is an arm rotates a barrel. The needle valve rotates with the barrel, so it twists the fuel line as it changes position. There is no low speed mixture, which is why the Internet was really invented - to advise beginners and needle twisters how to set the idle. Maybe the twisting of the fuel line served to restrict fuel flow at idle, which suggests a real evil genius at work. But the instructions mention that a notch could be filed in the rotating barrel to lean the idle.
http://www.rcgroups.com/forums/showa...3&d=1293050302
From this I was able to see that Howard used the BRAMCO throttle. He used this with a Fox .35 and an 11/6 prop, most likely a TopFlite based on it's blade shape. Here are pictures of a NIB BRAMCO throttle. About the only similarity to a modern carb is an arm rotates a barrel. The needle valve rotates with the barrel, so it twists the fuel line as it changes position. There is no low speed mixture, which is why the Internet was really invented - to advise beginners and needle twisters how to set the idle. Maybe the twisting of the fuel line served to restrict fuel flow at idle, which suggests a real evil genius at work. But the instructions mention that a notch could be filed in the rotating barrel to lean the idle.
05-27-2016, 10:51 AM
#34
Jay, when I was in school I worked part time for Chris Machin, maker of Rev-Up props. Before he did props full time he worked for a couple of companies in Dallas, one was Curtis Mathes which made TV's, and the other was Texas Instruments where he helped develop the machines that put transistor in a hermetically sealed can. That's why it pains me to use a TopFright prop.
I should note that Curtis Mathes was a large corporation, while Don Mathes was a talented Engineer, and probably not related.
I should note that Curtis Mathes was a large corporation, while Don Mathes was a talented Engineer, and probably not related.
Last edited by HighPlains; 05-27-2016 at 11:16 AM. Reason: clarification
05-27-2016, 11:04 AM
#35
I had also mentioned the dual needle valve engine control system with a S/N escapement. Bonner sold these, either as a complete unit, or without the escapement. A number of engine makers cast into their engines two flat spots on either side of their venturi so the second needle valve could be easily installed. On of the benefits of this vented fuel line scheme was the fact if you held down the control button for a short period of time, the engine would quickly suck the fuel line dry and kill the engine so you could land. The Smog Hog provided a demarcation between the complex design for the more invested modeler and the simpler sport design that was significantly more affordable. I should mention that the escapement operates the loop of wire and moves the vent pad from the left to the right depending which needle you want working. Each vent it connected to the fuel lines with a "T" connection. When the control is held down, the escapement holds the pad away from both vents.
Last edited by HighPlains; 05-27-2016 at 11:09 AM.
05-27-2016, 05:04 PM
#37
Yes, I believe it is as shown on that article. There is some differences between the two magazine plans and also the Veco plans. It could perhaps trace subtle improvements, or be that the drafter for each magazine used what they thought important. Certainly when a design was kitted, changes to parts are made to facilitate die cutting requirements.
05-27-2016, 10:29 PM
#38
I think the article's first paragraph explains it: The Aeromodeller magazine guys showed it that way at their own discretion.
Thanks for posting this stuff, it never ceases to amaze me. And by the way, I started R/C only 10 years later and by then had even reliable reeds R/C with servos and proper throttle for engine-on landings (but no tailwheel brake and no paved runway). Interesting that such a big model like the Smog Hog has been flown with .19 engines; it was still the same with me 10 years later (and my trainer model had the 2415 airfoil as well) but seems no longer imaginable today.
Thanks for posting this stuff, it never ceases to amaze me. And by the way, I started R/C only 10 years later and by then had even reliable reeds R/C with servos and proper throttle for engine-on landings (but no tailwheel brake and no paved runway). Interesting that such a big model like the Smog Hog has been flown with .19 engines; it was still the same with me 10 years later (and my trainer model had the 2415 airfoil as well) but seems no longer imaginable today.
05-29-2016, 07:07 AM
#39
My Feedback: (2)
Yes, I believe it is as shown on that article. There is some differences between the two magazine plans and also the Veco plans. It could perhaps trace subtle improvements, or be that the drafter for each magazine used what they thought important. Certainly when a design was kitted, changes to parts are made to facilitate die cutting requirements.
Back in the 50's I thought I tried about every motor control gadget out there but I don't remember this one. I plan to travel through Colby, Ks. June 15 on my way to Hutchinson. I should be in Colby for lunch at the plaza just south side of I-70. Will the Smog Hog be built by then? I never had a Smog Hog, I flew a Livewire Cruiser at that time with Marcy 6Ch radio. Next I built a Kraft Triple Simul reed system.
05-29-2016, 11:14 AM
#40
UStik - It is very underpowered by today's standards especially with a .19 sized engine. But that was for single channel use, where it should have weighed under four pounds. With a Fox .35 and a 11x6 prop, it would have been no powerhouse either. The peak hp on a Fox of that era was only 0.45, and when operated with a 11x6 prop, the rpm drops down to about 8,000 which also drops power down to about 0.36 hp. However when it unloads in the air, rpm should climb to around 9,000 and a power of roughly 0.4 hp. These numbers are based on an engine review done by Peter Chinn. The hp numbers would help if one should wish to push holes through wires to spin a propeller.
In electrical devices, electrons do not move very much, but the holes they leave behind sure do.
This also allows me to estimate the speed of the Smog Hog at around 45 mph in level flight. The 2415 airfoil is a very good choice for this design (or any sport model). The Hog with a 12" wing chord would be operating at a Reynolds number in the 400,000 range at flight speed. It also performs well at a RN of 100,000, so landings at 10-12 mph would have been possible, and likely considering the 14 oz wing loading. The zero lift angle on a 2415 is about -2.5 degrees, so with the 2 degrees positive incidence the model would have to fly about 6 degrees nose high when inverted to fly level.
In electrical devices, electrons do not move very much, but the holes they leave behind sure do.
This also allows me to estimate the speed of the Smog Hog at around 45 mph in level flight. The 2415 airfoil is a very good choice for this design (or any sport model). The Hog with a 12" wing chord would be operating at a Reynolds number in the 400,000 range at flight speed. It also performs well at a RN of 100,000, so landings at 10-12 mph would have been possible, and likely considering the 14 oz wing loading. The zero lift angle on a 2415 is about -2.5 degrees, so with the 2 degrees positive incidence the model would have to fly about 6 degrees nose high when inverted to fly level.
05-29-2016, 12:45 PM
#41
HighPlains, I don't quite understand the electron holes thing, I'm a mechanical engineer. 
We used to sneer at electronics as electro-comics, but I do have some understanding of aero-dramatics.
Anyway, I'd guess the Hog's speed to be about 30 mph, and a 1960s .19 would pull it gracefully with a 9x4 prop (Peter Chinn test). It would even fly inverted, of course nose high. A .35 would make the Hog a real Class II aerobat, maybe at 45 mph. I might be tempted to simulate it.
We used to sneer at electronics as electro-comics, but I do have some understanding of aero-dramatics.Anyway, I'd guess the Hog's speed to be about 30 mph, and a 1960s .19 would pull it gracefully with a 9x4 prop (Peter Chinn test). It would even fly inverted, of course nose high. A .35 would make the Hog a real Class II aerobat, maybe at 45 mph. I might be tempted to simulate it.
05-29-2016, 01:26 PM
#42
Sid, I think that I can break away from the farm on the 15th for a lunch with you at the Oasis on the Plains. I'll pm you my cell number.
As far as having the Hog together by then. I am known for slow building. But maybe I will have it framed up by then.
I had been somewhat puzzled by the motor control, but when I read again the original article and found that the escapement rubber was wound from under the fuselage bottom through a small plug. This means that the escapement was mounted vertically This moved the BRAMCO throttle with three positions, though the mid throttle position could only be held briefly because the other controls would have been unavailable. Anyway, it makes sense now.
It would appear that when Howard Bonner won the 1956 Nat's, the CG 5 channel radio was obsolete, or about to be, as the eight channel reed sets came out that fall and winter. The other significant development was simultaneous control of two channels, which would be one control from the left side with one from the right of the xmitter. This requires two tone generators and a few more parts. Another gain block at the very least. As it was, some tubes were actually two tubes built into one which did help shrinking circuits. But transistors were about to change everything.
As far as having the Hog together by then. I am known for slow building. But maybe I will have it framed up by then.
I had been somewhat puzzled by the motor control, but when I read again the original article and found that the escapement rubber was wound from under the fuselage bottom through a small plug. This means that the escapement was mounted vertically This moved the BRAMCO throttle with three positions, though the mid throttle position could only be held briefly because the other controls would have been unavailable. Anyway, it makes sense now.
It would appear that when Howard Bonner won the 1956 Nat's, the CG 5 channel radio was obsolete, or about to be, as the eight channel reed sets came out that fall and winter. The other significant development was simultaneous control of two channels, which would be one control from the left side with one from the right of the xmitter. This requires two tone generators and a few more parts. Another gain block at the very least. As it was, some tubes were actually two tubes built into one which did help shrinking circuits. But transistors were about to change everything.
05-29-2016, 01:41 PM
#43
Peter Chinn kind of indicated that a Fox .35 was about the same power as a good .19 engine, but he attributed that to the fact that they were designed to run that way.
Electrons are in heavy supply around an atom, the number depend on the molecular weight and the shell they occupy. So it is pretty much totally random when a particular electron moves from one atom to the next. But when they do move, they leave behind the hole. The holes move through in the opposite direction that the electrons drift. As in any description of physics, this is a gross oversimplification. Just look up hole flow theory.
Electrons are in heavy supply around an atom, the number depend on the molecular weight and the shell they occupy. So it is pretty much totally random when a particular electron moves from one atom to the next. But when they do move, they leave behind the hole. The holes move through in the opposite direction that the electrons drift. As in any description of physics, this is a gross oversimplification. Just look up hole flow theory.
05-29-2016, 06:26 PM
#44
My Feedback: (2)
Sid, I think that I can break away from the farm on the 15th for a lunch with you at the Oasis on the Plains. I'll pm you my cell number.
As far as having the Hog together by then. I am known for slow building. But maybe I will have it framed up by then.
I had been somewhat puzzled by the motor control, but when I read again the original article and found that the escapement rubber was wound from under the fuselage bottom through a small plug. This means that the escapement was mounted vertically This moved the BRAMCO throttle with three positions, though the mid throttle position could only be held briefly because the other controls would have been unavailable. Anyway, it makes sense now.
It would appear that when Howard Bonner won the 1956 Nat's, the CG 5 channel radio was obsolete, or about to be, as the eight channel reed sets came out that fall and winter. The other significant development was simultaneous control of two channels, which would be one control from the left side with one from the right of the xmitter. This requires two tone generators and a few more parts. Another gain block at the very least. As it was, some tubes were actually two tubes built into one which did help shrinking circuits. But transistors were about to change everything.
As far as having the Hog together by then. I am known for slow building. But maybe I will have it framed up by then.
I had been somewhat puzzled by the motor control, but when I read again the original article and found that the escapement rubber was wound from under the fuselage bottom through a small plug. This means that the escapement was mounted vertically This moved the BRAMCO throttle with three positions, though the mid throttle position could only be held briefly because the other controls would have been unavailable. Anyway, it makes sense now.
It would appear that when Howard Bonner won the 1956 Nat's, the CG 5 channel radio was obsolete, or about to be, as the eight channel reed sets came out that fall and winter. The other significant development was simultaneous control of two channels, which would be one control from the left side with one from the right of the xmitter. This requires two tone generators and a few more parts. Another gain block at the very least. As it was, some tubes were actually two tubes built into one which did help shrinking circuits. But transistors were about to change everything.
I would enjoy lunch very much if it works out. I will check for PM and work out the details.
Sid
05-30-2016, 02:08 AM
#45
Thanks for the hint! Couldn't that electron hole analogy also apply to the bubbles in the fuel lines when the Bonner Motor Control Unit is used?
As to the engine, the .35 is much more powerful than a .19 in any case. I didn't calculate it, just assumed numbers to show a point: 0.4 hp at 9000 rpm gives 0.2 hp propulsion power if the prop's efficiency is 50%. 0.45 hp at 12000 rpm with a smaller/lower-pitch prop would be only 0.18 hp propulsion power at 30% prop efficiency. Interesting is that the 11x6 was THE prop for pattern from the mid 50s to the mid 60s when the .35 was THE engine at first, then the .45 and then the .60. The bigger the displacement the bigger the rpm flown at. Wing loading and speed increased accordingly.
I think I found the Peter Chinn test here or here, but maybe with the Bonner Motor Control Unit they used another Fox .35 variant, here. It was prepared for the second needle valve assembly, as you wrote above.
For the speed estimate, I would subtract 20% (not 10%) from the 50 mph pitch speed, giving only 40 mph, what is well enough considering the low 14 oz/sqin wing loading. Ed Kazmirski even throttled the .45 on his 18 oz/sqin Taurus. Interesting is that both MAN and Aeromodeller show a 32-34% MAC balance point, which is quite forward and "fast", but MAN 2 degrees and Aeromodeller (quoting R. E. Bowen) 3 degrees wing incidence (and decalage).
As to the engine, the .35 is much more powerful than a .19 in any case. I didn't calculate it, just assumed numbers to show a point: 0.4 hp at 9000 rpm gives 0.2 hp propulsion power if the prop's efficiency is 50%. 0.45 hp at 12000 rpm with a smaller/lower-pitch prop would be only 0.18 hp propulsion power at 30% prop efficiency. Interesting is that the 11x6 was THE prop for pattern from the mid 50s to the mid 60s when the .35 was THE engine at first, then the .45 and then the .60. The bigger the displacement the bigger the rpm flown at. Wing loading and speed increased accordingly.
I think I found the Peter Chinn test here or here, but maybe with the Bonner Motor Control Unit they used another Fox .35 variant, here. It was prepared for the second needle valve assembly, as you wrote above.
For the speed estimate, I would subtract 20% (not 10%) from the 50 mph pitch speed, giving only 40 mph, what is well enough considering the low 14 oz/sqin wing loading. Ed Kazmirski even throttled the .45 on his 18 oz/sqin Taurus. Interesting is that both MAN and Aeromodeller show a 32-34% MAC balance point, which is quite forward and "fast", but MAN 2 degrees and Aeromodeller (quoting R. E. Bowen) 3 degrees wing incidence (and decalage).
Last edited by UStik; 05-30-2016 at 02:36 AM.
05-30-2016, 07:18 AM
#46
I quit getting bubbles in the fuel line when I switched to opaque fuel tubing.
I think the old Fox .35 had more torque than the .19 size, but power is a function of RPM too. We move an airplane by expanding a very small mass of hot air moving fast to move a much larger mass of air at a much slower speed. When we do this we are accelerating air from one side of the prop to the other. As such, the cross section of the air has to reduce in diameter as it moves past the plane of the prop. As this mass of air moves down the fuselage, it has to expand with the loss of pressure/momentum.
I don't know what the efficiency of model propellers is, full size trend around 85%. Many people think that efficiency means slippage, but they are different things. When prop makers assign pitch numbers to props, especially the old wood props, they are basing the pitch on the flat surface of the backside of the blade, generally at about 75% of the blade length way from the hub. However the zero lift angle of that type of airfoil is usually 2 to 4 degrees higher than the measured angle. Further complicating measurements is that only very poorly designed props are a true helical pitch down the blade. Then the amount of engine unload was difficult to measure. You could do it with an audio tach if you also knew the airspeed on a calm day and a strong familiarity with equations on Doppler shift.
Unfortunately each engine and airframe combination would require a specifically designed prop. After a decade of searching for that prop for a Formula One pylon racing model, we got pretty close but kept looking. Sport models are not so demanding, though a few points will maximize results. Too many tend to over prop, usually based on material included with the engine. They may have a different agenda than the operator. To suggest large props make an engine sound more powerful to the potential buyer, or they are trying to meet noise levels. Either way, less power than what they rate it at. Since we know that engines tend to unload about 1500 with a typical model, prop so the peak ground rpm is 2,000 or so below the rpm that peak power is made. Then test fly a range of props that run there. I may have 5 or 6 hundred props, so that is no problem for me, but I wince when I see the wrong prop on people's models. Quite often I would have a better prop with me, so a quick change would open their eyes.
I had not noticed the decalage difference between the two magazines. Perhaps the 3 degree would work better with a single channel and a .19 engine. With too much you might end up with a climb stall dive over and over and with a limited control system that might get rather sporting.
It's time to start cutting some wood.
I think the old Fox .35 had more torque than the .19 size, but power is a function of RPM too. We move an airplane by expanding a very small mass of hot air moving fast to move a much larger mass of air at a much slower speed. When we do this we are accelerating air from one side of the prop to the other. As such, the cross section of the air has to reduce in diameter as it moves past the plane of the prop. As this mass of air moves down the fuselage, it has to expand with the loss of pressure/momentum.
I don't know what the efficiency of model propellers is, full size trend around 85%. Many people think that efficiency means slippage, but they are different things. When prop makers assign pitch numbers to props, especially the old wood props, they are basing the pitch on the flat surface of the backside of the blade, generally at about 75% of the blade length way from the hub. However the zero lift angle of that type of airfoil is usually 2 to 4 degrees higher than the measured angle. Further complicating measurements is that only very poorly designed props are a true helical pitch down the blade. Then the amount of engine unload was difficult to measure. You could do it with an audio tach if you also knew the airspeed on a calm day and a strong familiarity with equations on Doppler shift.
Unfortunately each engine and airframe combination would require a specifically designed prop. After a decade of searching for that prop for a Formula One pylon racing model, we got pretty close but kept looking. Sport models are not so demanding, though a few points will maximize results. Too many tend to over prop, usually based on material included with the engine. They may have a different agenda than the operator. To suggest large props make an engine sound more powerful to the potential buyer, or they are trying to meet noise levels. Either way, less power than what they rate it at. Since we know that engines tend to unload about 1500 with a typical model, prop so the peak ground rpm is 2,000 or so below the rpm that peak power is made. Then test fly a range of props that run there. I may have 5 or 6 hundred props, so that is no problem for me, but I wince when I see the wrong prop on people's models. Quite often I would have a better prop with me, so a quick change would open their eyes.
I had not noticed the decalage difference between the two magazines. Perhaps the 3 degree would work better with a single channel and a .19 engine. With too much you might end up with a climb stall dive over and over and with a limited control system that might get rather sporting.
It's time to start cutting some wood.
Last edited by HighPlains; 05-30-2016 at 08:01 AM. Reason: Spelln'
05-30-2016, 10:14 AM
#47
I thought the Motor Control lets air into one of the fuel lines what might cause bubbles (due to surface tension) instead of completely replacing the fuel.
As to the propeller, I know a rule of thumb recommending 20% "slack" as an assumption. That neglects the real load on the propeller as well as its real (aerodynamic as opposed to geometric) pitch and pitch distribution over the radius. Just a rule of thumb, therefore pitch speed of a 11x6 at 9000 rpm is 50 mph, minus 20% is 40 mph.
50% and 30% were just assumptions from my experience in calculating model propellers. My best props are all low-rpm for electric drives of slow-flying models. I found 70% a typical peak value which might be even optimistic. Above all, it's reached at a certain speed and decreases rapidly with more or less speed. Attached example is a APC 17x12E prop, which is rather good (the medium-blue line). You see, it's easy to lose much efficiency if the prop is not the right one. My idea was that you'd need a smaller and lower-pitch prop to let the Fox .35 rev up to its full 0.45 hp power. Such a prop would be noticeably less efficient than the 11x6, because smaller diameter (as you remarked) gives less efficiency, but smaller pitch as well (like a smaller gear on a car). And the 11x7 may be not as efficient as an E-prop because the glow props are generally too fast turning and thus too small.
By the way, for racing props, you may have a look at Martin Hepperle's website, who is expert in that. (Disregard if you know it.)
Now to the Hog. I have it in the simulator (with a dummy appearance) and there's the conundrum I suspected. Of course 3° decalage (geometric) let it fly slowly and a .19 with a 9x4 is well enough. It's a good trainer model, well damped and honest, easy to fly. A .35 with a 11x6 together with 2° decalage makes it lively and pattern-able. But, independent of the motor/prop combination, dependent only on decalage, it flies even slower than I thought. Level flight is at 25 mph. At full power it does what you mentioned, a climb stall dive.
I used Blaine Beron-Rawdon's Plane Geometry spreadsheets to calculate the stability data. The two pictures are from these spreadsheets and show a wire-frame model of the Hog and a plan view with the centers of lift of wing and stab, the neutral point (red) and the C/G (green) as shown in the plans (at 33% and giving 8.4% static stability margin). This calculation says 3° aerodynamic decalage makes for 26 mph level flight speed, 2° aero decalage for 50 mph. These calculations are usually quite reliable, but I had to employ several educated guesses (airfoil pitching moment, ...) so there's an error margin.
Of course the simulator gives the same results because I used the same values. But if only 2.5° aero decalage is set, level flight speed is 31 mph, what I had expected. Climb is just right, glide with same speed as level. That seems just about perfect. By the way, I set 1° right thrust (the Aeromedeller plan shows a bit left offset instead) and no down thrust, which would change the game.
So only now it's really a conundrum at least for me, and I'm very curious what the real Smog Hog will do. There's nothing better than reality, simulation just can't replace it completely. All the best for your project!
As to the propeller, I know a rule of thumb recommending 20% "slack" as an assumption. That neglects the real load on the propeller as well as its real (aerodynamic as opposed to geometric) pitch and pitch distribution over the radius. Just a rule of thumb, therefore pitch speed of a 11x6 at 9000 rpm is 50 mph, minus 20% is 40 mph.
50% and 30% were just assumptions from my experience in calculating model propellers. My best props are all low-rpm for electric drives of slow-flying models. I found 70% a typical peak value which might be even optimistic. Above all, it's reached at a certain speed and decreases rapidly with more or less speed. Attached example is a APC 17x12E prop, which is rather good (the medium-blue line). You see, it's easy to lose much efficiency if the prop is not the right one. My idea was that you'd need a smaller and lower-pitch prop to let the Fox .35 rev up to its full 0.45 hp power. Such a prop would be noticeably less efficient than the 11x6, because smaller diameter (as you remarked) gives less efficiency, but smaller pitch as well (like a smaller gear on a car). And the 11x7 may be not as efficient as an E-prop because the glow props are generally too fast turning and thus too small.
By the way, for racing props, you may have a look at Martin Hepperle's website, who is expert in that. (Disregard if you know it.)
Now to the Hog. I have it in the simulator (with a dummy appearance) and there's the conundrum I suspected. Of course 3° decalage (geometric) let it fly slowly and a .19 with a 9x4 is well enough. It's a good trainer model, well damped and honest, easy to fly. A .35 with a 11x6 together with 2° decalage makes it lively and pattern-able. But, independent of the motor/prop combination, dependent only on decalage, it flies even slower than I thought. Level flight is at 25 mph. At full power it does what you mentioned, a climb stall dive.
I used Blaine Beron-Rawdon's Plane Geometry spreadsheets to calculate the stability data. The two pictures are from these spreadsheets and show a wire-frame model of the Hog and a plan view with the centers of lift of wing and stab, the neutral point (red) and the C/G (green) as shown in the plans (at 33% and giving 8.4% static stability margin). This calculation says 3° aerodynamic decalage makes for 26 mph level flight speed, 2° aero decalage for 50 mph. These calculations are usually quite reliable, but I had to employ several educated guesses (airfoil pitching moment, ...) so there's an error margin.
Of course the simulator gives the same results because I used the same values. But if only 2.5° aero decalage is set, level flight speed is 31 mph, what I had expected. Climb is just right, glide with same speed as level. That seems just about perfect. By the way, I set 1° right thrust (the Aeromedeller plan shows a bit left offset instead) and no down thrust, which would change the game.
So only now it's really a conundrum at least for me, and I'm very curious what the real Smog Hog will do. There's nothing better than reality, simulation just can't replace it completely. All the best for your project!
Last edited by UStik; 05-30-2016 at 10:19 AM.
05-30-2016, 01:06 PM
#48
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There is a guy in the UK building units that use modern rf TX modules and standard receivers and servos that simulate the behavior of a reed set. http://www.singlechannel.co.uk/
Here is the test flight of a 6 ch reed simulator.
https://youtu.be/38vrO1fxlJQ If I was building a replica Smog Hog I would go with one of his units.
Here is the test flight of a 6 ch reed simulator.
https://youtu.be/38vrO1fxlJQ If I was building a replica Smog Hog I would go with one of his units.
05-31-2016, 05:45 AM
#49
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I just got my single channel and 12 channel reed modules from Phil last week.
It was $66 dollars including postage from England.
If you want a module I suggest you order it right away,
mine took about 3 months which was no problem for me.
He makes them in batches because he very busy with a business he owns.
If you to his website and go to Archives, the first two documents explain the S/C and reed modules and how to set them up.
Jon
It was $66 dollars including postage from England.
If you want a module I suggest you order it right away,
mine took about 3 months which was no problem for me.
He makes them in batches because he very busy with a business he owns.
If you to his website and go to Archives, the first two documents explain the S/C and reed modules and how to set them up.
Jon
Last edited by F106A; 05-31-2016 at 07:48 AM.
05-31-2016, 07:30 AM
#50
UStik - I'd say that we are pretty close on our performance assumptions. The high static margins indicates that left to it's own devices, the design would tend to self recover nicely and want to fly at one speed, depending on the decalage. Pretty much like any modern RC trainer, or for that matter most general aviation aircraft where you set the power then trim for level flight. An airplane enters either the slow oscillation phugoid where we consider an airplane in trim or the much more violent climb/stall/dive of being out of trim. Most modelers are completely unaware of the phugoid oscillation, since they are unlikely ever to fly either the time or distance to see the effect. What it does teach us however is the sensitivity to a change by a fraction of a degree of decalage.
I've seen Hepperle's site over 20 years ago. It is mostly out dated material, though the section on racing in high wind conditions is quite good. I think his material is more theory than practice with his primary interest being airfoils. But he totally missed the effects of the introduction of high aspect wings had on the sport as well as many other things. Minimizing inducted drag is paramount when you are pulling 30 to 40 g's in a turn and 30% of the race course is in that mode of flight.
As to the reed simulator equipment, it's nice equipment. But it is incongruent with the goals I stated in the first paragraph of the first post.
I've seen Hepperle's site over 20 years ago. It is mostly out dated material, though the section on racing in high wind conditions is quite good. I think his material is more theory than practice with his primary interest being airfoils. But he totally missed the effects of the introduction of high aspect wings had on the sport as well as many other things. Minimizing inducted drag is paramount when you are pulling 30 to 40 g's in a turn and 30% of the race course is in that mode of flight.
As to the reed simulator equipment, it's nice equipment. But it is incongruent with the goals I stated in the first paragraph of the first post.