I think I should add a few more thoughts to give a more complete picture of how the Cyclo-crane should be used, in case someone that can do something about them happens along here. I first want to correct my earlier statement about the neutrally buoyant Cyclo-crane pulling its load by the nose. I realized that it should be by the tail, because when it would be pulling the “mother” aerostat along, it should be in the most aerodyamic direction. I also want to correct something I mentioned on the side about propellers blowing through the center of an aerostat. I realized that they do not in fact do that on any currect design.
Next, I want to mention the idea that with 4 neutrally buoyant Cyclo-cranes, and with the aerostat ballasted to neutral buoyancy, and with the whole thing being remotely controlled, it would be preferred to keep the whole apparatus constantly airborne. The minimal fuel costs required to overcome minor variations in buoyancy and to adjust position should be more than offset for by the freedom from docking or storage costs. I was hired by Bob Phillips to design the load handling and mooring-docking systems for the DARPA research project. I left AeroLift about the time that the DARPA report was being wrapped up and at the time that the demonstrator was being prepared for the unsuccessful test flight, I was working for USLTA, during which time I participated in the ground handling crew. Ground handling an airship, and getting into and out of a mooring set-up or a hangar, are pretty challenging areas for airships, and they are compounded for each different location one has to bring the ship to. Here we have a concept ship that theoretically never has to land except for maintenance.
If I had the means to work on this, I would immediately buy the “2-ton” demonstrator and find a place to put it back together. Then I would hire about 11 engineers (3 structural, 3 aerodynamic, 2 electrical, 2 computer, hardware and software, and a specialist in hydraulics), a couple aircraft mechanics, 2 fabric specialists, a couple men with experience with lighter than air gas, and 5 or 6 handymen with rigging experience. The engineers would start first, figuring out how to beef it up with whatever structural modifications and power are needed to generate 5 tons of thrust with its propellers, as well as how to control all of the surfaces. Once the configurations were figured out and built and successfully tested, the engineers would use that experience to design from a blank sheet a new, more efficient model of similar capacity. I would continue this process until I had 5 working Cyclo-cranes with 5-ton thrust, including the original. Once they were made, they would be kept flying whenever they could not be safely moored or tethered. They would be constantly working, lifting loads, or just used for publicity demonstrations.
At that point, I would design and order a special aerostat to be made with 20 tons of lifting capacity. There would be the flexible hybrid 40-ton heavy lift airship we all have been waiting for, which would consume less power than a 20 ton helicopter would consume. From this point, the next step would be to try one with double the capacity, etc. If our estimates were close on the DARPA project, and the 20-ton model was feasible, and 50 tons of thrust could be generated by a beefed up the blades, then there is the possibility of a 400 ton model.
Well, I can hope that someone actually does this. There are people who have the needed funds, which I imagine could be in the $10 to $20 million range for that first 40-ton ship, for 5 to 10 years of work needed. There is no doubt in my mind that the Cyclo-crane can be made to work to at least the 5-ton level, with computer controlled dynamics and properly placed actuators. The first demonstrator worked to a point even with its fairly INefficiently designed structure and poor control system.
I think all of us who worked on the Cyclo-crane had a sense that that beautiful flying machine has to be good for something, yet several expressed the idea that something seemed wrong with the primary lifting being done by the stalk-tip wings. At the same time, the Piasecki failure, as well as the failures of the Macon rigid ship, illustrated the huge problems associated with huge airship structures, fighting against weight constraints, yet needing more strength and rigidity. Free-flying, somewhat stubby propeller/airships pulling axially on an aerostat offer a solution that could very well get us past those barriers.
As you know the Aerocrane, which doesn’t have the problem with the bending moment, came before the Cyclocrane and the later configuration solved the “second order effect” control problem. Without winglets on the ends of the blades lateral movement of the Aerocrane was accomplished by tilting the rotor disk, like a helicopter. In Aerocranes designed for lighter loads the force to move the vehicle laterally couldn’t be generated quickly enough to overcome gusts. Aerocranes built for heavier loads, 100 tons or more, could generate enough force, quickly enough, to work, at least that was what I thought. Here’s a link to an early illustration of a very large Aerocrane doing its thing: https://www.robcrimmins.com/wp-content/uploads/2013/10/Aerocrane-illustration-of-boat-transport.jpg
When we assembled the 2 ton Cyclocrane the ballonet was the most difficult aspect. Hundreds of fittings and pieces of hardware, sixty-eight 1/16″ cables routed through scores of pulleys, winches and chains, ropes, knots and acres of fabric all had to be just right. It was maddening at times and until it was finished I hated it. But ultimately, to my amazement, it worked, and during the flights we made, it was reliable. Your concerns about the problems associated with that aspect of a rotating aerostat are valid but maybe not insurmountable.
First, although you didn’t mention it, I want to clarify that my comment about the inefficient frame in no way is a negative comment about the work of your dad, Don Doolittle, and everyone else involved. They/you did an amazingly good job, especially given the constraints you all worked under. I probably would have chosen to make it the same way, if I were putting it together in my yard. However, when you are designing to sustain a bending moment, the weight of the structure should be outboard as far as possible. The tubes running through the middle tend to put weight where it is not so effective. And that is precisely what makes me enthusiastic. It worked to a good point, even with those disadvantages.
I am aware of the tremendous challenge of getting a ballonet in a rotating craft. Even though it wasn’t my job, I got involved a little in tossing around ideas for the DARPA model’s ballonet. Again, I think you all did an excellent job making that Cyclo-crane work. I would take a try at an axial piston design for the ballonet, but if that didn’t pan out, your dad had a design that worked. I don’t think that any of the problems are insurmountable. It is just a question of which way is the best, and how strong it can get.
While I am suggesting operating the Cyclo-crane in Aerocrane mode, as Reggie used to frequently call it, I like the Cyclo-crane’s elongated profile compared to the disk shaped Aerocrane. It allows the propeller to pull on the load at a smaller angle, and it is much more aerodynamic in travelling mode or as a tug craft. I think that most of the time, transporting weights would best be done with the main aerostat neutrally buoyant as well, either with a payload or water ballast, and the Cyclo-crane pulling horizontally in the corkscrew-into-straight-flight mode that your dad envisioned.
You are right about the bigger sized craft being able to take wind gusts better, and furthermore, a neutrally buoyant Cyclo-crane would be even better able to take side gusts that a 50% lift model, because the envelope would be smaller if it only had to support the weight of the craft.
Something I keep forgetting to mention is that even when a neutrally buoyant Cyclo-crane lifts its payload with pure aerodynamic power, it is still theoretically more efficient than a helicopter, because a helicopter typically acts over a much smaller thrust disk of air, and because the helicopter has to support its own weight plus that of the payload.
When I mentioned that an ideal structure to take bending would have the members as far outboard as possible, I was uncomfortably aware that such a structure could make the aerostat quite hard to install and inflate. Somehow you would have to put the fabric into place over the outside of that structure, and then it would be full of air. Getting the air out and the helium in without substantial mixing would be a big task, to say the least. I imagine that was what Don Doolittle was thinking also when he designed the structure based on stalks coming out of the middle of a center tube. You need space to inflate from and deflate to. I also imagine that the structural engineers on the DARPA project hadn’t figured that out either. There was no room to deflate any aerostat that was assembled on that design, with all of the members filling up the entire helium space in the interest of structural efficiency. I never discussed this with the others. I can only guess that they were planning to do a whopper of a purifying job to scavenge out the non-helium components.
Anyway, as I meditated on that difficulty, I remembered to “think outside the envelope”. I think the answer is to to put the structure on the outside of the envelope. That (1) gets the structural members where you want them, as far outboard as possible, (2) gets the structural members where out into the air you can access them for inspection and maintenance without breathing apparatus, and (3) it makes the installation of the aerostat much easier. You don’t even need to seal around the stalks. I also think it would be ultimately easier to assemble the frame. It could be built alone, without the aerostat, which could be added to the inside of the inside structure as a last step after getting all of the controls and engines working. One of the ideal goals might be to have a model small enough that the ship could lift its own weight with aerodynamics alone, a safety feature in case the aerostat deflated in flight.
I think the only drawback would be the air resistance of the members whirling through the air. But, if that turned out to be a significant problem, here is one more thought: With the structure confined to a shell around the outer contour, an aerostat envelope could be assembled around it with seals for the stalks, as before. However, the filling would be done with a dummy envelope inserted inside, and inflated until it pressed out agains the outer envelope. Then, when the outer envelope was secured, the inner dummy envelope would be taken out.
Without all of that structural weight in the middle, the structural weight would be pretty much optimized, and since it seemed like the DARPA project 20 ton model was feasible with a less efficient structure with a lot in the middle, that would mean that the Cyclo-crane concept (with aerodynamic forces being 50% of net aerostatic lift) could extend beyond 20 tons lift capacity before the scale problem caught up with it. With my idea of using the Cyclo-crane as a neutrally buoyant propeller, the expansion would be feasible up to the next level, which I won’t venture to guess about now. In summary, the scale problem (with the weight increasing by the 4/3 power of the volume/buoyant lift) is not a fatal flaw. The huge lifts dreamed of by those who funded the Cyclo-crane with money and effort are still feasible, to a great extent by the Cyclo-crane as originally envisioned, and further to the hundreds of tons lifting with the neutrally buoyant Cyclo-cranes and a mother aerostat.
I think my hands ran faster than my brain there. It should be (with aerodynamic forces lifting 50% of the payload and being equal to the net aerostatic lift).
I now realize that moving all of the members to the outside on a ship that size would encounter buckling/wrinkling problems, and that the way it was done with the spine down the middle was the best structural way to build it. This is to recognize my error and to again congratulate all of you on an excellent job. And, I want to repeat my assertion that the demonstrator project was the “Wright Flyer” stage. There is an urgent need for this heavy lift craft, but it is waiting or those with faith in their hearts and not dollar signs in their eyes.
I was part of the DARPA ’87 software development team. What Tomas Gray states is a revelation to me (!) and explains much.
A more current application question: Are you looking into development of a Cyclo-Crane like Hybrid Drone? From my “software” world-view, it seems like it would be a craft that combines a much better loiter time then any current Drone, with good mobility.
If you real-world types do come-up with a Lighter Then Air Drone Hybrid, I want one.
The first 2-ton Cyclocrane, the one that was torn from the mast by the storm on “Black Friday”, used slip rings to transfer all the commands and data between the rotating and non-rotating systems. The slip rings assembly, which was in the forward cab on the 8” diameter aluminum tube that ran through the cab to the nose of the ship, was heavy. It also wasn’t one-hundred per cent reliable. The Cyclocrane that finally flew in 1984 used radio telemetry rather than slip rings and “brushes” to carry the signals back and forth between the rotating and non-rotating systems and components. That change made “drop outs” during flight less of a problem and freed up a lot of helium for the payload. It also made it possible to fly the Cyclocrane remotely. Dad emphasized that feature from then on, although we never called the Cyclocrane a drone.
Hi, Chris. I don’t remember you but we must have been together in that Aerolift office. If you remember, Bob Phillips suddenly left, right after we figured out the scaling limitation. Now I know why that was such a blow to him. He didn’t want to burst our “balloon” by telling us the bad news, I figure. My son is a software engineer and he has the same interest as you in computer controlled drones. I think for a small scale camera carrying drone, a simple blimp with four simple propellers along the side would be the best approach. The Cyclo-crane approach would only be valuable in big sizes, too complicated for the small drone applications. However, as a demonstration of concept a small model would be interesting.
Hello Mr. Crimmins,
You write about Dale Hoke. It he was engaged in introduction a spider balloon logging? How he now?
Please, inform.
I long time prosecute a subjects of operation balloon logging in Russia.
Dale left the Cyclocrane program in 1982 and I haven’t heard of him since. It would be interesting to hear about his work with you. Check out the comments here occasionally. Dale might visit.
I watched a balloon logging operation in western Oregon in the early 1980’s and research by the U.S. military into using the same system to carry containers from ship to shore was one of the programs behind the invention of the Aerocrane.
Very successful photos pictures! It is seldom possible to see on a photo process balloon logging. Thanks!
Dale Hoke, was the owner of company Aerial Crane Systems. He carried out tests balloon crane ” system a spider ” from radio a remote control system. It was in the beginning 1992. I had correspondence with him 8-10 years ago, but then he has sharply ceased to answer letters.
My response to your email requesting reports and other information on balloon logging is duplicated here for others who may be interested:
The pictures I added to my site after reading your post are the only ones I have of aerial logging with skyline systems.
When we built the Cyclocrane we received help in multiple ways from a local logging company, Churchill Logging, and the owner, George Churchill, took us to the site in the pictures. I knew the operation existed and I read reports on it but I don’t have any of them. I know a bit about the balloon because I worked with the company that made it. Aerostar International of Sioux Falls South Dakota made the 600,000 cubic foot, onion shaped balloon. They also made the envelopes for the A50 and A60 Lightships manufactured by American Blimp while I was their production manager. The logging balloon was of fairly conventional construction except that it was extremely strong. The urethane coated, polyester fabric was heavy, over 20 oz / yard. When I saw it in operation it was clear to me why. The dynamics of the operation were amazing. They would pull the balloon down and then release it allowing tremendous momentum to build to yank huge loads free of snags. The balloon would visibly deform as it reached the end of its ascent and the logs were torn free. The manned airships I worked on and the kite balloons have rigging and hardware of the type found on other kinds of aircraft and yachts. The hardware and cables on the logging balloon were what you find on cranes and heavy equipment, huge shackles and pins and thick cable. As I recall the running cables were 3/4″. It was heavy stuff.
FERIC, the Forest Engineering Research Institute of Canada might be a source of information on balloon logging. They are a private consortium of logging companies and others. They changed their name a few years ago and became FPInnovations, which stands for Forest Products Innovations. Their web site is http://www.fpinnovations.ca/Pages/home.aspx If there has been any balloon logging in North America in the recent past they would know about it.
After sleeping on this, I had some additional thoughts, for what they are worth. I said that my preferred concept would be a Piasecki type system, but there is the huge challenge of getting a good enough structure to hold those propellers, as the Piasecki disaster showed. All of the other hybrid heavy lift concepts I have seen out there have these incorporated propellers on board with many of them mounted inboard and blowing through the center to minimize those structural challenges. However, the Cyclo-Crane is a huge propeller that does not have to be supported. Looking at the Cyclo-Crane as a kind of tugboat instead of the main ship, it could be used to provide the lift for the larger aerostat with only a tether line instead of a rigid structure. In this mode, the Cyclo-Crane would be required to be at or near neutral buoyancy, since it would have to pull down as well as pull up, depending on whether the mother ship were loaded or empty. Thus, this weight problem the Cyclo-Crane concept seemed to contain basically disappears. When we were thinking of the Cyclo-Crane as a self-contained lifting system, it was a battle of structural engineering to maintain that margin between weight and aerostatic lift. A small percent in loss of the buoyant lift would devastate its lifting capacity. From the tugboat perspective, the Cyclo-Crane would just need enough buoyant lift to offset the weight of its structure, and a little discrepancy either way would not be crucial.
With this design concept, for example, four Cyclo-Cranes with a main propeller thrust capacity of 30 tons would be constructed. I do not remember what the aerodynamic engineers said the DARPA concept ship’s main propellers would generate. I recall it was quite a bit more than that. An aerostat with 120 tons of aerostatic lift would be constructed with a tether on each corner integrated with the load lifting structure. These would be picked up by the Cyclo-Cranes by the nose end only. When the ship is empty, the Cyclo-Cranes would turn themselves down in Aero-Crane mode, nose up, and hold the ship down. As load is added, they would fly themselves around to nose down, above the aerostat, and add lift. There we have a 240 ton lifting capacity ship.
As I thought of this, I recalled something Lars Radestam told us once when we were lamenting the difficulty with structural weight. We were limiting the rotational speed to be able to get an aerodynamic lift commensurate with the aerostatic lift. He asked why we didn’t just get that ship spinning faster, maybe making the wing stalks shorter and just get proportionally more lift from aerodynamics. If the ship is made neutrally buoyant, the whole question of how fast to rotate the Cyclo-Crane and how much lift it should generate aerodynamically becomes a bigger open question.
I am beginning to think that the Cyclo-Crane has an amazing future ahead.
Thank you for commenting on this very important point. It’s something that we didn’t address in detail as we built and flew the two ton model although we believed that Cyclocranes joined end to end was a configuration that would go a long way toward handling the bending moment for fifty or even one-hundred ton machines. If we were wrong about that I’m glad to be set straight. When making comparisons to existing technology Dad would cite Sikorsky Skycranes whose maximum payload is ten to twelve tons which was generally considered the limit for heavy lift with rotor disks. Our next step was to be a sixteen ton machine for which there was a significant market even if we couldn’t fly for much longer, which we could, and for 1/4 the hourly cost as the similarly rated helicopter, which still doesn’t exist. Jack Erickson, whose company came to own the S64 type certificate, agreed. He was a major investor in the Cyclocrane. His employee, Dale Hoke, who I should have mentioned in the video for his dedication and contribution, was with us full time in the months before the crash in 1982.
Putting the video together, collecting the pictures and posting it all has been a goal for a while. Finding so little about the Cyclocrane on the Internet was a shame and since I had so much material and knowledge of the project and the ability to make it available I was neglecting an obligation by not following through. Now you, Reggie, Lars and others have what I have and can reminisce with me. If you have pictures send them and I’ll add them to the image galleries but if not please accept my sincere thanks for your detailed post as well as your efforts on the project.
No, I have no photos except some cut out from articles. I was living in Portland working for Hyster when the Cyclo-Crane was flying and dealing with a bunch of other issues, so I wasn’t aware of it until I moved back to Tillamook in 1986.
I think that your dad was right really on the payload capacity of helicopter versus airship, but I guess that probably the DoD people were figuring, “Hey, two helicopters could do that and what’s a little extra operating cost? What we really want is to be able to do a lot more than ever has been done before.”
Rob, thanks for putting together this web site about the Cyclo-Crane. I was employed on the team for the DARPA research project in 1987 for the larger Cyclo-Crane that was to carry 20 tons. I was hired to design the load handling apparatus and the mooring/docking systems. I worked with Reg Maas and Lars Radestam, and I knew a few others that appear in your video. I actually attended high school in Tillamook with David Churchill. It was a fascinating project. The concept was obviously workable, but during the year or so I worked on the project, a flaw in the concept was discovered that really doomed it for the purposes that the department of defense funded it for. Being a spinning airship. the load has to be carried from the ends. This means that the body of the airship has to withstand a large bending moment. It has been a long time and I would have to recalculate the details, but one day Bob Phillips, who was the engineering manager at the time, came up and said that a competitor had pointed out that the bigger the Cyclo-Crane was built, the heavier it got per volume. He asked me if that was true, since Aero-Lift leaders had been claiming that if a small one worked, the bigger one would lift even more, a normal relationship for airships in general. I did some quick estimates based on engineering structural calculations and told him that the competitor was right: The Cyclo-Crane will become less lift-efficient as it gets bigger, which means that there will be an upper limit to the workable size of the Cyclo-Crane. As I worked with the structural engineers who were doing the frame design, it seemed like the model we were working on was still in the feasible range. They were doing everything possible to design a frame that would be much more weight efficient than the demonstrator. I was excited by the challenge that we really could get a 20 ton lifting machine in the air, even though it appeared that this would be about the biggest Cyclo-Crane possible. What I did not know then, that I discovered much later on the internet is that the DoD was not interested in a 20 ton model, since that range is feasible with helicopters, but in a hybrid airship that would lift over 200 tons, even up to 500 tons. That is impossible for the Cyclo-Crane concept. We used to discuss the fact that the blue blades had more potential lifting force than the red lifting blades and we discussed turning the Cyclo-Crane vertical in the Aerocrane mode to get some serious lift in calm air. I toyed with the idea of getting two Cyclo-cranes together to do some really useful lifting, perhaps turning in opposite directions by a kind of chain drive instead of the airplane motor drive. That would be a real structural challenge to achieve, and 200 tons is still out of reach for two Cyclo-Cranes, although perhaps theoretically possible with the pure Aerocrane. One of the things that got me excited about the Cyclo-Crane concept is that because of the need to handle the large bending moment, the Cyclo-Crane structure has to be super strong compared to any other airship built, and as I and Larry Maxwell consulted together about the mooring concepts, I estimated that the 20 ton model could take a 60 MPH side wind. Well, in an ideal world, I think that the Cyclo-Crane would have a part in lifting in the 20 to 50 ton lifting range with the ability to flip into the Aero-crane mode and get powerful and efficient aerodynamic lift with those huge propellers, much beyond half of the payload. The great strength and ability to withstand wind forces would give it a great advantage in a number of situations. It would be a valuable addition to our technological tool kit. However, it would be a great challenge requiring large investment, and I doubt that there is any source of investment available at this point in our history. The problems with fatigue and vibration in a rotating airship get scary. We never did get a comfortable concept for the ballonet. I think they could be resolved, but especially after seeing the video of the failure of the Piasecki craft, this makes me tremble and want to have a large testing budget available before wanting to undertake such a project. In many respects, the Piasecki concept of a stationary aerostat is the safer approach. If I were to undertake a design project of a hybrid heavy lift ship today, the first concept I would go for is the stationary aerostat with four large propellers around the sides using the cross-stalk wings like your dad put on the Cyclo-Crane for sideways and forwards propulsion. Basically, that means Aero-Crane/Cyclo-Crane type aerodynamics instead of vibrating helicopters on a Piasecki type arrangement. I think that would work well and I think a proof of concept could be done in the 60 foot length. That would indeed have a scaling advantage, and could achieve the dream of a 500 ton lift model. Anyway, it was a great trip down memory lane to see your video and my heart goes out to you and your mother for the disappointment that you went through. In an ideal world, your dad’s visionary ideas and diligent persistence should have been met with success.
April 23rd, 2014
17 comments
I think I should add a few more thoughts to give a more complete picture of how the Cyclo-crane should be used, in case someone that can do something about them happens along here. I first want to correct my earlier statement about the neutrally buoyant Cyclo-crane pulling its load by the nose. I realized that it should be by the tail, because when it would be pulling the “mother” aerostat along, it should be in the most aerodyamic direction. I also want to correct something I mentioned on the side about propellers blowing through the center of an aerostat. I realized that they do not in fact do that on any currect design.
Next, I want to mention the idea that with 4 neutrally buoyant Cyclo-cranes, and with the aerostat ballasted to neutral buoyancy, and with the whole thing being remotely controlled, it would be preferred to keep the whole apparatus constantly airborne. The minimal fuel costs required to overcome minor variations in buoyancy and to adjust position should be more than offset for by the freedom from docking or storage costs. I was hired by Bob Phillips to design the load handling and mooring-docking systems for the DARPA research project. I left AeroLift about the time that the DARPA report was being wrapped up and at the time that the demonstrator was being prepared for the unsuccessful test flight, I was working for USLTA, during which time I participated in the ground handling crew. Ground handling an airship, and getting into and out of a mooring set-up or a hangar, are pretty challenging areas for airships, and they are compounded for each different location one has to bring the ship to. Here we have a concept ship that theoretically never has to land except for maintenance.
If I had the means to work on this, I would immediately buy the “2-ton” demonstrator and find a place to put it back together. Then I would hire about 11 engineers (3 structural, 3 aerodynamic, 2 electrical, 2 computer, hardware and software, and a specialist in hydraulics), a couple aircraft mechanics, 2 fabric specialists, a couple men with experience with lighter than air gas, and 5 or 6 handymen with rigging experience. The engineers would start first, figuring out how to beef it up with whatever structural modifications and power are needed to generate 5 tons of thrust with its propellers, as well as how to control all of the surfaces. Once the configurations were figured out and built and successfully tested, the engineers would use that experience to design from a blank sheet a new, more efficient model of similar capacity. I would continue this process until I had 5 working Cyclo-cranes with 5-ton thrust, including the original. Once they were made, they would be kept flying whenever they could not be safely moored or tethered. They would be constantly working, lifting loads, or just used for publicity demonstrations.
At that point, I would design and order a special aerostat to be made with 20 tons of lifting capacity. There would be the flexible hybrid 40-ton heavy lift airship we all have been waiting for, which would consume less power than a 20 ton helicopter would consume. From this point, the next step would be to try one with double the capacity, etc. If our estimates were close on the DARPA project, and the 20-ton model was feasible, and 50 tons of thrust could be generated by a beefed up the blades, then there is the possibility of a 400 ton model.
Well, I can hope that someone actually does this. There are people who have the needed funds, which I imagine could be in the $10 to $20 million range for that first 40-ton ship, for 5 to 10 years of work needed. There is no doubt in my mind that the Cyclo-crane can be made to work to at least the 5-ton level, with computer controlled dynamics and properly placed actuators. The first demonstrator worked to a point even with its fairly INefficiently designed structure and poor control system.
I think all of us who worked on the Cyclo-crane had a sense that that beautiful flying machine has to be good for something, yet several expressed the idea that something seemed wrong with the primary lifting being done by the stalk-tip wings. At the same time, the Piasecki failure, as well as the failures of the Macon rigid ship, illustrated the huge problems associated with huge airship structures, fighting against weight constraints, yet needing more strength and rigidity. Free-flying, somewhat stubby propeller/airships pulling axially on an aerostat offer a solution that could very well get us past those barriers.
As you know the Aerocrane, which doesn’t have the problem with the bending moment, came before the Cyclocrane and the later configuration solved the “second order effect” control problem. Without winglets on the ends of the blades lateral movement of the Aerocrane was accomplished by tilting the rotor disk, like a helicopter. In Aerocranes designed for lighter loads the force to move the vehicle laterally couldn’t be generated quickly enough to overcome gusts. Aerocranes built for heavier loads, 100 tons or more, could generate enough force, quickly enough, to work, at least that was what I thought. Here’s a link to an early illustration of a very large Aerocrane doing its thing: https://www.robcrimmins.com/wp-content/uploads/2013/10/Aerocrane-illustration-of-boat-transport.jpg
When we assembled the 2 ton Cyclocrane the ballonet was the most difficult aspect. Hundreds of fittings and pieces of hardware, sixty-eight 1/16″ cables routed through scores of pulleys, winches and chains, ropes, knots and acres of fabric all had to be just right. It was maddening at times and until it was finished I hated it. But ultimately, to my amazement, it worked, and during the flights we made, it was reliable. Your concerns about the problems associated with that aspect of a rotating aerostat are valid but maybe not insurmountable.
First, although you didn’t mention it, I want to clarify that my comment about the inefficient frame in no way is a negative comment about the work of your dad, Don Doolittle, and everyone else involved. They/you did an amazingly good job, especially given the constraints you all worked under. I probably would have chosen to make it the same way, if I were putting it together in my yard. However, when you are designing to sustain a bending moment, the weight of the structure should be outboard as far as possible. The tubes running through the middle tend to put weight where it is not so effective. And that is precisely what makes me enthusiastic. It worked to a good point, even with those disadvantages.
I am aware of the tremendous challenge of getting a ballonet in a rotating craft. Even though it wasn’t my job, I got involved a little in tossing around ideas for the DARPA model’s ballonet. Again, I think you all did an excellent job making that Cyclo-crane work. I would take a try at an axial piston design for the ballonet, but if that didn’t pan out, your dad had a design that worked. I don’t think that any of the problems are insurmountable. It is just a question of which way is the best, and how strong it can get.
While I am suggesting operating the Cyclo-crane in Aerocrane mode, as Reggie used to frequently call it, I like the Cyclo-crane’s elongated profile compared to the disk shaped Aerocrane. It allows the propeller to pull on the load at a smaller angle, and it is much more aerodynamic in travelling mode or as a tug craft. I think that most of the time, transporting weights would best be done with the main aerostat neutrally buoyant as well, either with a payload or water ballast, and the Cyclo-crane pulling horizontally in the corkscrew-into-straight-flight mode that your dad envisioned.
You are right about the bigger sized craft being able to take wind gusts better, and furthermore, a neutrally buoyant Cyclo-crane would be even better able to take side gusts that a 50% lift model, because the envelope would be smaller if it only had to support the weight of the craft.
Something I keep forgetting to mention is that even when a neutrally buoyant Cyclo-crane lifts its payload with pure aerodynamic power, it is still theoretically more efficient than a helicopter, because a helicopter typically acts over a much smaller thrust disk of air, and because the helicopter has to support its own weight plus that of the payload.
When I mentioned that an ideal structure to take bending would have the members as far outboard as possible, I was uncomfortably aware that such a structure could make the aerostat quite hard to install and inflate. Somehow you would have to put the fabric into place over the outside of that structure, and then it would be full of air. Getting the air out and the helium in without substantial mixing would be a big task, to say the least. I imagine that was what Don Doolittle was thinking also when he designed the structure based on stalks coming out of the middle of a center tube. You need space to inflate from and deflate to. I also imagine that the structural engineers on the DARPA project hadn’t figured that out either. There was no room to deflate any aerostat that was assembled on that design, with all of the members filling up the entire helium space in the interest of structural efficiency. I never discussed this with the others. I can only guess that they were planning to do a whopper of a purifying job to scavenge out the non-helium components.
Anyway, as I meditated on that difficulty, I remembered to “think outside the envelope”. I think the answer is to to put the structure on the outside of the envelope. That (1) gets the structural members where you want them, as far outboard as possible, (2) gets the structural members where out into the air you can access them for inspection and maintenance without breathing apparatus, and (3) it makes the installation of the aerostat much easier. You don’t even need to seal around the stalks. I also think it would be ultimately easier to assemble the frame. It could be built alone, without the aerostat, which could be added to the inside of the inside structure as a last step after getting all of the controls and engines working. One of the ideal goals might be to have a model small enough that the ship could lift its own weight with aerodynamics alone, a safety feature in case the aerostat deflated in flight.
I think the only drawback would be the air resistance of the members whirling through the air. But, if that turned out to be a significant problem, here is one more thought: With the structure confined to a shell around the outer contour, an aerostat envelope could be assembled around it with seals for the stalks, as before. However, the filling would be done with a dummy envelope inserted inside, and inflated until it pressed out agains the outer envelope. Then, when the outer envelope was secured, the inner dummy envelope would be taken out.
Without all of that structural weight in the middle, the structural weight would be pretty much optimized, and since it seemed like the DARPA project 20 ton model was feasible with a less efficient structure with a lot in the middle, that would mean that the Cyclo-crane concept (with aerodynamic forces being 50% of net aerostatic lift) could extend beyond 20 tons lift capacity before the scale problem caught up with it. With my idea of using the Cyclo-crane as a neutrally buoyant propeller, the expansion would be feasible up to the next level, which I won’t venture to guess about now. In summary, the scale problem (with the weight increasing by the 4/3 power of the volume/buoyant lift) is not a fatal flaw. The huge lifts dreamed of by those who funded the Cyclo-crane with money and effort are still feasible, to a great extent by the Cyclo-crane as originally envisioned, and further to the hundreds of tons lifting with the neutrally buoyant Cyclo-cranes and a mother aerostat.
I think my hands ran faster than my brain there. It should be (with aerodynamic forces lifting 50% of the payload and being equal to the net aerostatic lift).
I now realize that moving all of the members to the outside on a ship that size would encounter buckling/wrinkling problems, and that the way it was done with the spine down the middle was the best structural way to build it. This is to recognize my error and to again congratulate all of you on an excellent job. And, I want to repeat my assertion that the demonstrator project was the “Wright Flyer” stage. There is an urgent need for this heavy lift craft, but it is waiting or those with faith in their hearts and not dollar signs in their eyes.
I was part of the DARPA ’87 software development team. What Tomas Gray states is a revelation to me (!) and explains much.
A more current application question: Are you looking into development of a Cyclo-Crane like Hybrid Drone? From my “software” world-view, it seems like it would be a craft that combines a much better loiter time then any current Drone, with good mobility.
If you real-world types do come-up with a Lighter Then Air Drone Hybrid, I want one.
Good luck and thanks for posting this info.
The first 2-ton Cyclocrane, the one that was torn from the mast by the storm on “Black Friday”, used slip rings to transfer all the commands and data between the rotating and non-rotating systems. The slip rings assembly, which was in the forward cab on the 8” diameter aluminum tube that ran through the cab to the nose of the ship, was heavy. It also wasn’t one-hundred per cent reliable. The Cyclocrane that finally flew in 1984 used radio telemetry rather than slip rings and “brushes” to carry the signals back and forth between the rotating and non-rotating systems and components. That change made “drop outs” during flight less of a problem and freed up a lot of helium for the payload. It also made it possible to fly the Cyclocrane remotely. Dad emphasized that feature from then on, although we never called the Cyclocrane a drone.
Hi, Chris. I don’t remember you but we must have been together in that Aerolift office. If you remember, Bob Phillips suddenly left, right after we figured out the scaling limitation. Now I know why that was such a blow to him. He didn’t want to burst our “balloon” by telling us the bad news, I figure. My son is a software engineer and he has the same interest as you in computer controlled drones. I think for a small scale camera carrying drone, a simple blimp with four simple propellers along the side would be the best approach. The Cyclo-crane approach would only be valuable in big sizes, too complicated for the small drone applications. However, as a demonstration of concept a small model would be interesting.
Hello Mr. Crimmins,
You write about Dale Hoke. It he was engaged in introduction a spider balloon logging? How he now?
Please, inform.
I long time prosecute a subjects of operation balloon logging in Russia.
Dale left the Cyclocrane program in 1982 and I haven’t heard of him since. It would be interesting to hear about his work with you. Check out the comments here occasionally. Dale might visit.
I watched a balloon logging operation in western Oregon in the early 1980’s and research by the U.S. military into using the same system to carry containers from ship to shore was one of the programs behind the invention of the Aerocrane.
Your comment prompted me to post the pictures I took at the site in Oregon. They’re now at http://robcrimmins.com/2014/01/12/balloon-logging/
Very successful photos pictures! It is seldom possible to see on a photo process balloon logging. Thanks!
Dale Hoke, was the owner of company Aerial Crane Systems. He carried out tests balloon crane ” system a spider ” from radio a remote control system. It was in the beginning 1992. I had correspondence with him 8-10 years ago, but then he has sharply ceased to answer letters.
My response to your email requesting reports and other information on balloon logging is duplicated here for others who may be interested:
The pictures I added to my site after reading your post are the only ones I have of aerial logging with skyline systems.
When we built the Cyclocrane we received help in multiple ways from a local logging company, Churchill Logging, and the owner, George Churchill, took us to the site in the pictures. I knew the operation existed and I read reports on it but I don’t have any of them. I know a bit about the balloon because I worked with the company that made it. Aerostar International of Sioux Falls South Dakota made the 600,000 cubic foot, onion shaped balloon. They also made the envelopes for the A50 and A60 Lightships manufactured by American Blimp while I was their production manager. The logging balloon was of fairly conventional construction except that it was extremely strong. The urethane coated, polyester fabric was heavy, over 20 oz / yard. When I saw it in operation it was clear to me why. The dynamics of the operation were amazing. They would pull the balloon down and then release it allowing tremendous momentum to build to yank huge loads free of snags. The balloon would visibly deform as it reached the end of its ascent and the logs were torn free. The manned airships I worked on and the kite balloons have rigging and hardware of the type found on other kinds of aircraft and yachts. The hardware and cables on the logging balloon were what you find on cranes and heavy equipment, huge shackles and pins and thick cable. As I recall the running cables were 3/4″. It was heavy stuff.
FERIC, the Forest Engineering Research Institute of Canada might be a source of information on balloon logging. They are a private consortium of logging companies and others. They changed their name a few years ago and became FPInnovations, which stands for Forest Products Innovations. Their web site is http://www.fpinnovations.ca/Pages/home.aspx If there has been any balloon logging in North America in the recent past they would know about it.
After sleeping on this, I had some additional thoughts, for what they are worth. I said that my preferred concept would be a Piasecki type system, but there is the huge challenge of getting a good enough structure to hold those propellers, as the Piasecki disaster showed. All of the other hybrid heavy lift concepts I have seen out there have these incorporated propellers on board with many of them mounted inboard and blowing through the center to minimize those structural challenges. However, the Cyclo-Crane is a huge propeller that does not have to be supported. Looking at the Cyclo-Crane as a kind of tugboat instead of the main ship, it could be used to provide the lift for the larger aerostat with only a tether line instead of a rigid structure. In this mode, the Cyclo-Crane would be required to be at or near neutral buoyancy, since it would have to pull down as well as pull up, depending on whether the mother ship were loaded or empty. Thus, this weight problem the Cyclo-Crane concept seemed to contain basically disappears. When we were thinking of the Cyclo-Crane as a self-contained lifting system, it was a battle of structural engineering to maintain that margin between weight and aerostatic lift. A small percent in loss of the buoyant lift would devastate its lifting capacity. From the tugboat perspective, the Cyclo-Crane would just need enough buoyant lift to offset the weight of its structure, and a little discrepancy either way would not be crucial.
With this design concept, for example, four Cyclo-Cranes with a main propeller thrust capacity of 30 tons would be constructed. I do not remember what the aerodynamic engineers said the DARPA concept ship’s main propellers would generate. I recall it was quite a bit more than that. An aerostat with 120 tons of aerostatic lift would be constructed with a tether on each corner integrated with the load lifting structure. These would be picked up by the Cyclo-Cranes by the nose end only. When the ship is empty, the Cyclo-Cranes would turn themselves down in Aero-Crane mode, nose up, and hold the ship down. As load is added, they would fly themselves around to nose down, above the aerostat, and add lift. There we have a 240 ton lifting capacity ship.
As I thought of this, I recalled something Lars Radestam told us once when we were lamenting the difficulty with structural weight. We were limiting the rotational speed to be able to get an aerodynamic lift commensurate with the aerostatic lift. He asked why we didn’t just get that ship spinning faster, maybe making the wing stalks shorter and just get proportionally more lift from aerodynamics. If the ship is made neutrally buoyant, the whole question of how fast to rotate the Cyclo-Crane and how much lift it should generate aerodynamically becomes a bigger open question.
I am beginning to think that the Cyclo-Crane has an amazing future ahead.
Thank you for commenting on this very important point. It’s something that we didn’t address in detail as we built and flew the two ton model although we believed that Cyclocranes joined end to end was a configuration that would go a long way toward handling the bending moment for fifty or even one-hundred ton machines. If we were wrong about that I’m glad to be set straight. When making comparisons to existing technology Dad would cite Sikorsky Skycranes whose maximum payload is ten to twelve tons which was generally considered the limit for heavy lift with rotor disks. Our next step was to be a sixteen ton machine for which there was a significant market even if we couldn’t fly for much longer, which we could, and for 1/4 the hourly cost as the similarly rated helicopter, which still doesn’t exist. Jack Erickson, whose company came to own the S64 type certificate, agreed. He was a major investor in the Cyclocrane. His employee, Dale Hoke, who I should have mentioned in the video for his dedication and contribution, was with us full time in the months before the crash in 1982.
Putting the video together, collecting the pictures and posting it all has been a goal for a while. Finding so little about the Cyclocrane on the Internet was a shame and since I had so much material and knowledge of the project and the ability to make it available I was neglecting an obligation by not following through. Now you, Reggie, Lars and others have what I have and can reminisce with me. If you have pictures send them and I’ll add them to the image galleries but if not please accept my sincere thanks for your detailed post as well as your efforts on the project.
No, I have no photos except some cut out from articles. I was living in Portland working for Hyster when the Cyclo-Crane was flying and dealing with a bunch of other issues, so I wasn’t aware of it until I moved back to Tillamook in 1986.
I think that your dad was right really on the payload capacity of helicopter versus airship, but I guess that probably the DoD people were figuring, “Hey, two helicopters could do that and what’s a little extra operating cost? What we really want is to be able to do a lot more than ever has been done before.”
Rob, thanks for putting together this web site about the Cyclo-Crane. I was employed on the team for the DARPA research project in 1987 for the larger Cyclo-Crane that was to carry 20 tons. I was hired to design the load handling apparatus and the mooring/docking systems. I worked with Reg Maas and Lars Radestam, and I knew a few others that appear in your video. I actually attended high school in Tillamook with David Churchill. It was a fascinating project. The concept was obviously workable, but during the year or so I worked on the project, a flaw in the concept was discovered that really doomed it for the purposes that the department of defense funded it for. Being a spinning airship. the load has to be carried from the ends. This means that the body of the airship has to withstand a large bending moment. It has been a long time and I would have to recalculate the details, but one day Bob Phillips, who was the engineering manager at the time, came up and said that a competitor had pointed out that the bigger the Cyclo-Crane was built, the heavier it got per volume. He asked me if that was true, since Aero-Lift leaders had been claiming that if a small one worked, the bigger one would lift even more, a normal relationship for airships in general. I did some quick estimates based on engineering structural calculations and told him that the competitor was right: The Cyclo-Crane will become less lift-efficient as it gets bigger, which means that there will be an upper limit to the workable size of the Cyclo-Crane. As I worked with the structural engineers who were doing the frame design, it seemed like the model we were working on was still in the feasible range. They were doing everything possible to design a frame that would be much more weight efficient than the demonstrator. I was excited by the challenge that we really could get a 20 ton lifting machine in the air, even though it appeared that this would be about the biggest Cyclo-Crane possible. What I did not know then, that I discovered much later on the internet is that the DoD was not interested in a 20 ton model, since that range is feasible with helicopters, but in a hybrid airship that would lift over 200 tons, even up to 500 tons. That is impossible for the Cyclo-Crane concept. We used to discuss the fact that the blue blades had more potential lifting force than the red lifting blades and we discussed turning the Cyclo-Crane vertical in the Aerocrane mode to get some serious lift in calm air. I toyed with the idea of getting two Cyclo-cranes together to do some really useful lifting, perhaps turning in opposite directions by a kind of chain drive instead of the airplane motor drive. That would be a real structural challenge to achieve, and 200 tons is still out of reach for two Cyclo-Cranes, although perhaps theoretically possible with the pure Aerocrane. One of the things that got me excited about the Cyclo-Crane concept is that because of the need to handle the large bending moment, the Cyclo-Crane structure has to be super strong compared to any other airship built, and as I and Larry Maxwell consulted together about the mooring concepts, I estimated that the 20 ton model could take a 60 MPH side wind. Well, in an ideal world, I think that the Cyclo-Crane would have a part in lifting in the 20 to 50 ton lifting range with the ability to flip into the Aero-crane mode and get powerful and efficient aerodynamic lift with those huge propellers, much beyond half of the payload. The great strength and ability to withstand wind forces would give it a great advantage in a number of situations. It would be a valuable addition to our technological tool kit. However, it would be a great challenge requiring large investment, and I doubt that there is any source of investment available at this point in our history. The problems with fatigue and vibration in a rotating airship get scary. We never did get a comfortable concept for the ballonet. I think they could be resolved, but especially after seeing the video of the failure of the Piasecki craft, this makes me tremble and want to have a large testing budget available before wanting to undertake such a project. In many respects, the Piasecki concept of a stationary aerostat is the safer approach. If I were to undertake a design project of a hybrid heavy lift ship today, the first concept I would go for is the stationary aerostat with four large propellers around the sides using the cross-stalk wings like your dad put on the Cyclo-Crane for sideways and forwards propulsion. Basically, that means Aero-Crane/Cyclo-Crane type aerodynamics instead of vibrating helicopters on a Piasecki type arrangement. I think that would work well and I think a proof of concept could be done in the 60 foot length. That would indeed have a scaling advantage, and could achieve the dream of a 500 ton lift model. Anyway, it was a great trip down memory lane to see your video and my heart goes out to you and your mother for the disappointment that you went through. In an ideal world, your dad’s visionary ideas and diligent persistence should have been met with success.
Leave a comment