Bensen, Brock, Wallis. Differences?

Coda

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I know Wallis was inspired by the early Bensens, but I'm wondering if his machines really were much different functionally, and if so, what did he change and why? I have the same question about the Brock machines - what did he improve?

So, is there really anything better than a B8M (staying within the confines of the 'Bensen type' gyro)?
 

phantom

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Bensens were simple and a bit crude with the boat tank and seat and tail system, a brock was a refined Bensen , the tail were different , it had a seat tank and control system that had some differences,The Wallis machine while being simple by aircraft standard was far more complex but unlike the Bensen and Brock were never intended to be built in your garage, I have built Bensen/ Brock type and also copies of Wallis type machines with the help of a few hand drawn sketches that ken Wallis sent me of the more difficult parts and it takes a lot more work and time to build one.
Norm
 

SandL

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Wallis bits

Wallis bits

Bensens were simple and a bit crude with the boat tank and seat and tail system, a brock was a refined Bensen , the tail were different , it had a seat tank and control system that had some differences,The Wallis machine while being simple by aircraft standard was far more complex but unlike the Bensen and Brock were never intended to be built in your garage, I have built Bensen/ Brock type and also copies of Wallis type machines with the help of a few hand drawn sketches that ken Wallis sent me of the more difficult parts and it takes a lot more work and time to build one.
Norm
some wallis gyros had pre rotators hidden beind a sheet of metal, I have hear he used the sturmey archer (spelling ?) bike gearing can you fill us in a bit more on that , I also understand he had several patents on gyro design elements, can you let us know what he came up with thanks ,
 

phantom

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I'm not familiar with the gears that you mentioned but his system didn't he's a bindix drive like most , when you moved the lever the gears were engaged in at the head followed by the friction wheel contacting the drum on the engine, his objections to a bindix drive was if something caused the wheel and the drum to contact in flight at full power it would activate the prerotator in flight, with his system this couldn't happen, his prerotators were able to spin his blades to a very high rpm so if it ever engaged in flight there would be considerable torque to deal with, his control system was a very simple pump handle type, he had trim springs down on the bottom to keep the head clean and simple, the teeter used bearings which was unheard of at the time.
I give him credit for giving me enough advice to keep me from killing myself early on and jerry Barnett gave me the recipe to make a machine so stable that being student pilot and test pilot at the same time was not dangerous.
Norm.
 

Coda

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Interesting conversation guys, keep it up.

Notes: I had Sturmey Archer gears on my Raleigh bikes when I was a kid. Bindix => Bendix? Aka Bendix-King? (which is a subsidiary of the company that I work for).
 

Kevin_Richey

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Norm: What was Jerry Barnett's "secret recipe" to keep it safe while being a student & test pilot a the same time?

I heard some time ago that Ken Wallis used the standard bicycle three-speed gearing that the old English Racer bicycles had for his pre-rotators...
 

phantom

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Jerries advice was very simple , what ever size the vertical fin and rudder was, make two more at least the same size and bolt them on in the horizontal position as far back as possible.
Norm
 

dinoa

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Wallis head
 

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Doug Riley

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Ken Brock came up with a slew of weight-saving refinements to the Bensen B-8M. These brought his KB-2 Mac-powered gyros well under the Part 103 (ultralight vehicle) weight limit. Ken lightened everything from the tow boom to the rudder pedals to the wheels and stub axles, besides (famously) the fuel tank.

The Rotax 532-powered KB-3 was less successful. Using a long-propped Rotax gear-drive engine on a Bensen frame misaligns the CG and prop thrustline. This, in turn, creates a machine ready to PPO unless a powerful horizontal stabilizer (H-stab) is added. The KB-3 as Ken designed it had NO H-stab at all.

The Bensen-Brock rigid axles are fine if you fly off smooth runways and have learned how to "kiss it on" (which you should!). The rigid-axle frame takes a pounding on rough takeoff surfaces, though. A cushioned landing gear is helpful in that case.

Wallis's wood rotors seem to have had some special qualities, as did Bensen's original woodies. Per Chuck Beaty's analysis, these blades had a semi-constant-speed feature, thanks to excess reflex at the trailing edge and a torsionally limber structure. I'm not convinced it's worth dealing with fragile wood blades just to re-gain this "advantage," though.
 

Coda

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Great info Doug, thanks! I read somewhere else that (paraphrased) "Bensens were inherently stable and safe machines, and once modified versions with more powerful engines appeared the accident rate skyrocketed, and the gyro's reputation was irreversibly damaged."
Reading your post, it sounds like the KB3 was responsible, at least in part?
 

phantom

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The problem was not caused by a more powerful engine, it was caused by a larger prop which moved the thrust line above the vertical centre of gravity, on some machines the problem was often made worse by a low seat and an inverted engine. Large props are great but only if you design the machine around it.
Norm
 

SMOF

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Bindix => Bendix? Aka Bendix-King?

The Bendix on a starter is the gear and one-way clutch unit. This rides on the motor output shaft, then engages the starter ring. When the ring starts moving faster than the motor is turning, the clutch releases, allowing the gear to spin with the ring, and preventing the gear from binding while it's being disengaged.
 

Doug Riley

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What Phantom said!

Bensen's machines were not nearly as stable or safe as Bensen could very easily have made them. Given that Bensen marketed the B-8M gyro as something of a consumer product, along with that went a duty, IMHO, to make them more beginner-friendly -- but Igor refused to do so. We're still living with both that attitude and the "widowmaker" reputation it has earned our aircraft.

That said, the advent of the redrive with long prop made things worse. The redrive is a torque multiplier, worsening the torque-over problem. The long prop with Bensen's seat location creates a large CG-thrustline discrepancy, worsening the PPO problem unless a powerful H-stab is added.

The KB-3 is no more to blame than any other gyro of its era. It's typical of the gyro designs released in the early years of redrive engines, especially the Rotax and Subaru. First-generation Air Commands and RAF-2000's, as well as the KB-3, were afflicted.

It took a couple decades, much prodding, a whole lot of nasty bluster and B.S., to get gyro builders to address the issues. In fact, the battle isn't over yet, though things much better than they were.
 

phantom

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I always thought it was interesting that the two people that gave me advice when I was getting started in gyros had completely different ideas to make a safe machine and both built machines that had good safety records, ken Wallis told me that unless I was building a high speed machine there was no need for a horizontal stabilizer but it was very important to have the vertical c of g and the thrust line with in one half inch of each other. Jerry Barnett told me that vertical c of g was not important but don't even attempt to fly without a large horizontal stabilizer , his machines used aircraft engines which is much better than the belt redrives that were used on engines with the engine down lower than the prop shaft, I was very lucky that my first engine after a Mac was a v four evinrude which by design the only way to sensibly put a redrive on it is prop down below the crank so I got it right by accident and when I tried something different I didn't like the way it flew so I went back to what I liked, quite possibly the only reason that I'm still here, that and always testing new stuff over soft deep snow.
Norm
 
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