counter rotating engines for a twin
02-18-2004, 07:42 PM
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counter rotating engines for a twin
Building a twin poses unique challenges. Notably the concern over control when, or if, one engine quits at the wrong time like on climb out while pouring on the coals. To minimize these effects, often counter-rotating engines are employed. Some even add outhrust to the engines to add to the effect.
Getting one of the engines to run in reverse is the trick. Reeds are no problem, they'll run in either direction. A crankported engine can be run in reverse if you have a reverse crankshaft. As far as I could ever find out, no one but Cox makes reverse crankshafts in 1/2A so the solution for me was to install one of these into a VA MK1 .049. To be sure that the conventionally rotating engine had the same characteristics as the reverse engine, a stock Cox crank was installed into another VA. Both engines employ a Wasp throttle, primarily because there's enough meat in the throttle body to install an adjustable airbleed. And the price is right at 15 dollars. The throttle levers are spring loaded to take up the slop in the cable set up that will be used. This ensures that throttle activation for both engines will be precisely matched. The VAs have rear exhaust and this lends itself to neat, custom made mufflers exiting straight back.
Interestingly, the reverse engine throttles a bit better than the conventional. Both are quite reliable though, doing 16K on a 6 X 3 black Tornado. Yes, one of these is a tractor type. Idle is 5K with solid transition. The power is a little light because these are well run engines. However, they'll be replacing a single .074 so I anticipate performance to be on par. Still, I'll be making up new anodized pistons with a better fit for more power.
Yes, the black anodized plug is on the reverse engine.
Getting one of the engines to run in reverse is the trick. Reeds are no problem, they'll run in either direction. A crankported engine can be run in reverse if you have a reverse crankshaft. As far as I could ever find out, no one but Cox makes reverse crankshafts in 1/2A so the solution for me was to install one of these into a VA MK1 .049. To be sure that the conventionally rotating engine had the same characteristics as the reverse engine, a stock Cox crank was installed into another VA. Both engines employ a Wasp throttle, primarily because there's enough meat in the throttle body to install an adjustable airbleed. And the price is right at 15 dollars. The throttle levers are spring loaded to take up the slop in the cable set up that will be used. This ensures that throttle activation for both engines will be precisely matched. The VAs have rear exhaust and this lends itself to neat, custom made mufflers exiting straight back.
Interestingly, the reverse engine throttles a bit better than the conventional. Both are quite reliable though, doing 16K on a 6 X 3 black Tornado. Yes, one of these is a tractor type. Idle is 5K with solid transition. The power is a little light because these are well run engines. However, they'll be replacing a single .074 so I anticipate performance to be on par. Still, I'll be making up new anodized pistons with a better fit for more power.
Yes, the black anodized plug is on the reverse engine.
02-18-2004, 11:25 PM
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RE: counter rotating engines for a twin
Wow, cool stuff Andy. Looks like there's a new digital camera in the Woitowicz household. Great pictures! So the VA crank is very close to the Cox? Small world!
02-18-2004, 11:54 PM
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RE: counter rotating engines for a twin
Yes, about the camera. Lots of fun learning digital photography. Amazing stuff.
Yes, the Cox crank is a tad bigger than the VA MK1 crank so it's just a matter of boring out the crankcase to suit. Unfortunately the Norvel crank is larger,,, I would have preferred two matched Norvels. Bushing it is not an option because the bushing would be way too thin.
Yes, the Cox crank is a tad bigger than the VA MK1 crank so it's just a matter of boring out the crankcase to suit. Unfortunately the Norvel crank is larger,,, I would have preferred two matched Norvels. Bushing it is not an option because the bushing would be way too thin.
02-19-2004, 07:47 PM
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RE: counter rotating engines for a twin
Andy
I'm intrested in that set up for a tilt rotor design that I just haven't proceeded with because of the counter rotating problem.
Where do I find those VA engines. I'm not familiar with them. Do the carbs come with them or are they sold seperate? Where do I find the reverse Cox crank? How much weight would you think they both could lift vertically? What other prep needs to be done?
ZZ
I'm intrested in that set up for a tilt rotor design that I just haven't proceeded with because of the counter rotating problem.
Where do I find those VA engines. I'm not familiar with them. Do the carbs come with them or are they sold seperate? Where do I find the reverse Cox crank? How much weight would you think they both could lift vertically? What other prep needs to be done?
ZZ
02-19-2004, 09:03 PM
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RE: counter rotating engines for a twin
Zoom,
A tilt rotor design. What a great idea. Yes, you will certainly need counter-rotating engines. Unfortunately, the VA MK1 has long ago gone out of production. It's hard to get new parts, like pistons and that's why I can't get as much power out of these as I normally could. Also, they never did come with carbs. I had to adapt Wasp .061 carbs to suit.
The reverse Cox cranks came directly from Cox some years ago. They may still have them. Unfortunately, the VA or any 1/2A engine tends NOT to be a heavy lifter. Not so much Cox but the Russian engines are definitely set up to turn fast on small props.
May I suggest that for your tilt rotor design, that you should consider a larger machine using larger engines. The only reverse crank that I'm aware of (and there certainly must be others) is the one once offered by K&B for their Veco .19. This was a non schneurle engine that used a steel sleeve and cast iron piston. It had ball bearings though and it actually was a real contender in the power to weight department compared to today's ABC engines. K&B has been absorbed by RJL/Mecoa and they're still selling K&B engines. They just may have these engines and the reverse crank for your project. One point is that they had a throttle that worked well enough but I was able to improve performance in that department to a large degree by installing the K&B Sportster .28 throttle. Along with that, I installed the muffler from the .28 and this gave me a very quiet, powerful engine that had very good throttling with very good power to weight.
Still, for your project, a glow motor of any stripe or size isn't a heavy lifter. Glow likes to turn fast with light torque. Perhaps you might consider diesel. Diesel engines, by their nature, deliver a lot of torque at low rpms and that sounds ideal for your tilt rotor. As well, diesels tolerate higher temps and even with open exhaust, are less noisy than glow. Throttling though, is an issue with diesels, many having poor transition and poor linearity but I've discovered that this isn't inherent to diesel operation, just to some of the older designs like PAW. I have a number of diesel conversions, (in small engines) that throttle extremely well. Perhaps there's a modern diesel engine out there that offers a reverse crank. I'm thinking MVVS or Irvine. If this sounds like it might work, a good source of diesels is www.carlsonengineimports.com . Call Ed Carlson, he knows his diesels. Starting diesels can also be an issue depending on a number of factors but I've found that a fuel formula that has much more ether than the usual 33%, like 50%, makes starting and handling much easier,,, at least for the small engines.
If there's anything at all I can do to help in this endeavor, please let me know.
A tilt rotor design. What a great idea. Yes, you will certainly need counter-rotating engines. Unfortunately, the VA MK1 has long ago gone out of production. It's hard to get new parts, like pistons and that's why I can't get as much power out of these as I normally could. Also, they never did come with carbs. I had to adapt Wasp .061 carbs to suit.
The reverse Cox cranks came directly from Cox some years ago. They may still have them. Unfortunately, the VA or any 1/2A engine tends NOT to be a heavy lifter. Not so much Cox but the Russian engines are definitely set up to turn fast on small props.
May I suggest that for your tilt rotor design, that you should consider a larger machine using larger engines. The only reverse crank that I'm aware of (and there certainly must be others) is the one once offered by K&B for their Veco .19. This was a non schneurle engine that used a steel sleeve and cast iron piston. It had ball bearings though and it actually was a real contender in the power to weight department compared to today's ABC engines. K&B has been absorbed by RJL/Mecoa and they're still selling K&B engines. They just may have these engines and the reverse crank for your project. One point is that they had a throttle that worked well enough but I was able to improve performance in that department to a large degree by installing the K&B Sportster .28 throttle. Along with that, I installed the muffler from the .28 and this gave me a very quiet, powerful engine that had very good throttling with very good power to weight.
Still, for your project, a glow motor of any stripe or size isn't a heavy lifter. Glow likes to turn fast with light torque. Perhaps you might consider diesel. Diesel engines, by their nature, deliver a lot of torque at low rpms and that sounds ideal for your tilt rotor. As well, diesels tolerate higher temps and even with open exhaust, are less noisy than glow. Throttling though, is an issue with diesels, many having poor transition and poor linearity but I've discovered that this isn't inherent to diesel operation, just to some of the older designs like PAW. I have a number of diesel conversions, (in small engines) that throttle extremely well. Perhaps there's a modern diesel engine out there that offers a reverse crank. I'm thinking MVVS or Irvine. If this sounds like it might work, a good source of diesels is www.carlsonengineimports.com . Call Ed Carlson, he knows his diesels. Starting diesels can also be an issue depending on a number of factors but I've found that a fuel formula that has much more ether than the usual 33%, like 50%, makes starting and handling much easier,,, at least for the small engines.
If there's anything at all I can do to help in this endeavor, please let me know.
02-19-2004, 10:49 PM
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RE: counter rotating engines for a twin
Andy:
Looks like you did it again. Nics.
Zoomie:
Not long ago I got two new reverse cranks for the K&B 40 (model 4011) from RJL, so they are available. And if you send the engines to Clarence Lee he'll make them scream for you.
If RJL/MECoA/K&B can't supply them, NIB K&B 40s can be had from eBay, generally around $50 each. But the cranks will have to come from RJL.
Bill.
Looks like you did it again. Nics.
Zoomie:
Not long ago I got two new reverse cranks for the K&B 40 (model 4011) from RJL, so they are available. And if you send the engines to Clarence Lee he'll make them scream for you.
If RJL/MECoA/K&B can't supply them, NIB K&B 40s can be had from eBay, generally around $50 each. But the cranks will have to come from RJL.
Bill.
02-19-2004, 10:54 PM
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RE: counter rotating engines for a twin
Bill,
Many thanks. And yes, .40s would make a tilt rotor project even more doable. Say, I wonder if diesel heads are available for the K&B?
Many thanks. And yes, .40s would make a tilt rotor project even more doable. Say, I wonder if diesel heads are available for the K&B?
02-19-2004, 11:27 PM
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RE: counter rotating engines for a twin
Well Andy, I must say, you just burst my bubble! [
] LOL.
I want to build it small.
Another idea I had was to use a Helicopter parts. At the time ( I been kicking this tilt rotor idea around for a while) there was no small heli stuff and heli heads were mucho dinaro! But now, with all these tiny nitro heli's I could look into some parts. I would still have to set up a counter rotating system though.
How's your knowledge with the Norvel .074 on heli's? Any problems with them over heating and the likes? Do they have a special head? I guess you would need a cooling fan.
ZZ
] LOL.I want to build it small.
Another idea I had was to use a Helicopter parts. At the time ( I been kicking this tilt rotor idea around for a while) there was no small heli stuff and heli heads were mucho dinaro! But now, with all these tiny nitro heli's I could look into some parts. I would still have to set up a counter rotating system though.
How's your knowledge with the Norvel .074 on heli's? Any problems with them over heating and the likes? Do they have a special head? I guess you would need a cooling fan.
ZZ
02-19-2004, 11:47 PM
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RE: counter rotating engines for a twin
Zoom,
Sorry 'bout that. [] Me too, I prefer small. [sm=thumbup.gif]
LiteMachines uses the Norvel .074. They use a special muffler/throttle set up that works very well. Alternately, you could use a stock Norvel with conventional throttle. The stock Norvel .074 throttles extremely well despite not having a means to adjust the low speed mixture. Plus, you can get heat sink heads for the stock engine from LiteMachines. The heat sink heads do not require fans of any kind.
Hope that helps.
Sorry 'bout that. [
] Me too, I prefer small. [sm=thumbup.gif]LiteMachines uses the Norvel .074. They use a special muffler/throttle set up that works very well. Alternately, you could use a stock Norvel with conventional throttle. The stock Norvel .074 throttles extremely well despite not having a means to adjust the low speed mixture. Plus, you can get heat sink heads for the stock engine from LiteMachines. The heat sink heads do not require fans of any kind.
Hope that helps.
