BarnFind Bensen

Joined
Jun 18, 2019
Messages
13
Location
Baraboo, WI
Joined up here to try do learn more about Bensen Gyros. I found one that's been sitting in a barn for 10 years. The owner passed away and his widow would like to get rid of it. I did some searching to see what a fair price might be, but I'm thinking I'd be better off avoiding it all together.

It's got the Mac 4318 engine, which seems to be the least reliable option for a powerplant. That appears to be the biggest downfall. Everything else looks complete and in good shape. It's got a pre-rotor and hand operated rotor brake. Hydraulic disc brakes on the main gear, seat tank (not sure on size) and there is no N-Number, so I'm assuming the previous owner flew it as an ultralight.

I am a fixed wing private pilot, but have no experience with full scale gyros. I had a hard enough time finding a tail dragger instructor - no idea if there are any gyro instructors in central WI. I'd obviously need some seat time in a two place gyro to even consider flying this one.

So, I guess my questions are - is there anything specific I need to look at that would be a deal breaker to buy this? I see a lot of people are in the market for blades on this site - is that something that need to be replaced periodically? Would sitting in a barn for 10 years mean the blades are untrustworthy?

Would I be better off parting it out - rather than going through it and making it airworthy?

Any idea on what a good price would be?

Am I better off to just walk away?!

I'll see if I can post pics up shortly.
 

Chris Burgess

GYRO-CFI
Joined
Oct 30, 2004
Messages
777
Location
Winter Garden FL 34787
Aircraft
Many makes and models, prefer open frame, Sold my SnoBird Tandem
Total Flight Time
3400+
Pictures would help a lot. Metal factory rotors? 10 years inside a climate-controlled space not bad, but salt water near by out in the open is a definite deal breaker in my book.
 
Joined
Jun 18, 2019
Messages
13
Location
Baraboo, WI
This is the best I can do for now. I've got other pics on my phone - but they're too large for this site. And, since they're in apple's stupid HEIC format, I can't convert them to JPG from here. I'll try and get some more posted tonight.
one.png

one.png
 
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DaveJaksha

Member
Joined
Feb 14, 2016
Messages
178
Location
Tucson
Aircraft
Sportcopter Vortex
Total Flight Time
100
Gravityisnotmyfriend,

If you are using an iPhone and share an HEIC image with a non-iOS user or a social media site, the image may automatically be converted to JPEG so that it is compatible with the target platform. If you do not want this behavior, or if you would like to continue and use JPEG for saving images rather than HEIF in iOS, open the "Settings" app in iOS, select Camera → Formats → Most Compatible, and choose Most Compatible. Files will then be saved as JPEG, instead of HEIC.

Cheers,

Dave
 
Joined
Jun 18, 2019
Messages
13
Location
Baraboo, WI
Gravityisnotmyfriend,

If you are using an iPhone and share an HEIC image with a non-iOS user or a social media site, the image may automatically be converted to JPEG so that it is compatible with the target platform. If you do not want this behavior, or if you would like to continue and use JPEG for saving images rather than HEIF in iOS, open the "Settings" app in iOS, select Camera → Formats → Most Compatible, and choose Most Compatible. Files will then be saved as JPEG, instead of HEIC.

Cheers,

Dave
Thanks. I'm new to this iphone world and am learning as I go. I've got the format switched - which will help me going forward. But, won't do much for the pics I have. I should be able to convert them to a format I can reduce in size from my home computer tonight.
 

DaveJaksha

Member
Joined
Feb 14, 2016
Messages
178
Location
Tucson
Aircraft
Sportcopter Vortex
Total Flight Time
100
You might find the useful.

iMazing HEIC Converter is a free utility (available for both Windows and Mac) that can batch-convert HEIC photos to JPEG or PNG format

Cheers,

Dave
 

Doug Riley

Platinum Member
Joined
Jan 11, 2004
Messages
6,335
The up-down (or fore-aft) pivot at the aft end of the joystick assembly is non-standard and a bit suspect. Is that U-strap some sort of a blacksmith job?

Regardless of brand, crankcase-scavenged 2-stroke engines use ball, roller and needle bearings because there's no pressure oil feed. These bearings are made of high-carbon steel that rusts easily. A complete teardown and rebuild of the engine is a must. Individual gyro fliers developed various preventive measures to reduce the chance of some of the more common failures associated with the McCulloch. These failure modes included piston seizures, exploding props, carb float failures, crank breakage, wrist pin failure, fuel pump failure and weak magnetos. A good Mac doctor will know about the fixes.

Even after these fixes, an unmuffled Mac like this one is incredibly loud. The racket is penetrating, and is all out of proportion to the size of the aircraft. Muffler designs are out there.

Change the rotor head bearing. They aren't expensive.

Disassemble the frame completely and check for galvanic corrosion. Salt can be a catalyst, but so can acids (including rainwater and -- yup -- animal pee; ask me about the airport owner's dog vs. my gyro). This type of corrosion is an electro-chemical reaction between bare steel (including stainless) and unprotected aluminum. There are some superficial signs of it in some of the photos. New AN hardware, with intact plating, helps ward off corrosion of this sort.

The seat tank appears to be an Air Command type, said to contain only 5 gallons, for compliance with Part 103.

While she has a horizontal stabilizer of sorts (which is good), it's pretty small.

I'd chuck any hoses and other rubber parts.

Be very suspicious of a wooden prop that has sat in a barn, especially when stored in the vertical position. The moisture all gravitates to the low blade.
 
Joined
Jun 18, 2019
Messages
13
Location
Baraboo, WI
Lots of good stuff. Thanks for the response.

The up-down (or fore-aft) pivot at the aft end of the joystick assembly is non-standard and a bit suspect. Is that U-strap some sort of a blacksmith job?
No idea. I'll look at it closer next time I get a chance. Didn't look like a cobble job in person, but I didn't look too closely.

Regardless of brand, crankcase-scavenged 2-stroke engines use ball, roller and needle bearings because there's no pressure oil feed. These bearings are made of high-carbon steel that rusts easily. A complete teardown and rebuild of the engine is a must. Individual gyro fliers developed various preventive measures to reduce the chance of some of the more common failures associated with the McCulloch. These failure modes included piston seizures, exploding props, carb float failures, crank breakage, wrist pin failure, fuel pump failure and weak magnetos. A good Mac doctor will know about the fixes.

Even after these fixes, an unmuffled Mac like this one is incredibly loud. The racket is penetrating, and is all out of proportion to the size of the aircraft. Muffler designs are out there.
I've restored several vintage snowmobiles that have been sitting. A complete tear down, and rebuild would definitely be the plan. I'm not sure what the Mac's use as crank seals - but those are a point of failure that can lead to lean running and complete engine seizure. Assuming they are replaceable, that is definitely in the plans.

As for the muffler? Yeah, I noticed that this engine is missing those! I was surprised to see open exhuast ports under those sheet metal boxes. I imagine it'd be quite loud!

Change the rotor head bearing. They aren't expensive.
Good to know. I had planned on removing and inspecting that bearing - if they are readily available, I'd just replace it with a new one.

Disassemble the frame completely and check for galvanic corrosion. Salt can be a catalyst, but so can acids (including rainwater and -- yup -- animal pee; ask me about the airport owner's dog vs. my gyro). This type of corrosion is an electro-chemical reaction between bare steel (including stainless) and unprotected aluminum. There are some superficial signs of it in some of the photos. New AN hardware, with intact plating, helps ward off corrosion of this sort.

The seat tank appears to be an Air Command type, said to contain only 5 gallons, for compliance with Part 103.

While she has a horizontal stabilizer of sorts (which is good), it's pretty small.

I'd chuck any hoses and other rubber parts.

Be very suspicious of a wooden prop that has sat in a barn, especially when stored in the vertical position. The moisture all gravitates to the low blade.
As a former Aerospace Engineer for Gulfstream (the airplane company - not the campers!) I am all too familiar with galvanic corrosion. I hadn't considered a complete frame disassembly - but it looks like it'd be pretty straightforward. I guess I need to look at this as a long term project if I want it to be airworthy and then decide if I want to buy it with that in mind.

Also good point on the wooden prop. I knew that you always stored a wooden prop horizontally for moisture concerns. I was also taught that you should always store aluminum props vertically. There's no issues with moisture imbalance - you're just less likely to bump your head on the prop that way!
 
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Gyro28866

David McCutchen
Joined
May 8, 2009
Messages
1,881
Location
Dickson, Tn. USA
Aircraft
Benson B7m & B8m, Dominator II; Kolb Mark III Classic
Total Flight Time
750 combined FW & Gyro
4318-A is the data tag for a 72 hp version. You should be able to look within the cooling towers and see inside an exhaust port. A 72 hp jug has 3 cross members, (the 90 hp version has 1 in the middle)
The propeller should be 50 to 52 inches long and pitched at 26*. That will give you about 4000 rpm. Which should provide about 275 # of thrust. Not a homesick angle but enough (depending upon your weight and the DA) to get you in the air.
The picture looks like a TPI (Tennessee Propellor Inc.) prop. If so, it will be stamped.
The engine mount IS NOT a standard Mac mount. I would be very concerned about the aluminum cracking from the vibration.
Appears to be Bensen blades and Bensen head with a Dick Wunderlich prerotor attached.
Appears to be a Bensen B-8 frame without the rock guard and a modified vertical stab and rudder with a horizontal component stab added.
Just as a wild guess, the cheek plates for the rotor head appear to have an offset for about 175 - 200 pound pilot. A hang test is a must, and possible adjustments made for your weight.
The oil/gas bottle in the frontal area is to prime the rear jugs to help start the engine.
I will know when you do, I will hear it here in Tennessee. She will be loud. Hearing protection is a MUST; or you will go deaf like me.
R & D in Texas has all the parts for the engine. And sometimes a lucky hit on Ebay.
So, what is it worth? Loaded question with many variables. In flight worthy condition and flying - 4-5 grand. Like she is - Maybe $1000, because she is a pile of parts for a build: ie; rotor, rotor head, prerotor, wheels, tire, seat tank
 
Joined
Jun 18, 2019
Messages
13
Location
Baraboo, WI
4318-A is the data tag for a 72 hp version. You should be able to look within the cooling towers and see inside an exhaust port. A 72 hp jug has 3 cross members, (the 90 hp version has 1 in the middle)
The propeller should be 50 to 52 inches long and pitched at 26*. That will give you about 4000 rpm. Which should provide about 275 # of thrust. Not a homesick angle but enough (depending upon your weight and the DA) to get you in the air.
The picture looks like a TPI (Tennessee Propellor Inc.) prop. If so, it will be stamped.
The engine mount IS NOT a standard Mac mount. I would be very concerned about the aluminum cracking from the vibration.
Appears to be Bensen blades and Bensen head with a Dick Wunderlich prerotor attached.
Appears to be a Bensen B-8 frame without the rock guard and a modified vertical stab and rudder with a horizontal component stab added.
Just as a wild guess, the cheek plates for the rotor head appear to have an offset for about 175 - 200 pound pilot. A hang test is a must, and possible adjustments made for your weight.
The oil/gas bottle in the frontal area is to prime the rear jugs to help start the engine.
I will know when you do, I will hear it here in Tennessee. She will be loud. Hearing protection is a MUST; or you will go deaf like me.
R & D in Texas has all the parts for the engine. And sometimes a lucky hit on Ebay.
So, what is it worth? Loaded question with many variables. In flight worthy condition and flying - 4-5 grand. Like she is - Maybe $1000, because she is a pile of parts for a build: ie; rotor, rotor head, prerotor, wheels, tire, seat tank
Thanks for the reply.

I didn't look close at the exhaust ports or the prop. Next time I see the craft will probably be over the 4th of July weekend - and that's only if I decide to make an offer on it. Still on the fence there.

Hang test? I was wondering how you'd check weight an balance on one of these. And was also wondering how you'd adjust it. Makes sense to change out cheek plates to move the rotor to balance the CG.

Yup, the bottle is a primer. Looks like a dishsoap container. The gas in that smells terrible. But, the gas in the tank still smells like gas. Of course I'd drain and flush it, but it doesn't smell like it's turned to tarnish and fouled the inside of the tank.

So, I've seen these engines with exhaust pipes and mufflers - but they are coming off the bottoms of the cylinders. Are there symmetrical piston ports? Can you rotate the pistons to put the exhaust ports on the bottom? Or do you rotate the whole engine and move the carb? I'm sure I could figure it out if I had the engine in front of me - just curious if anyone knew.
 
Joined
Jun 18, 2019
Messages
13
Location
Baraboo, WI
@Gyro28866 , I see you have a Kolb Mark III. Part of my interest in gyros in general stems from my Dad and his brothers (my uncles) experimenting with ultralights back in the 60's. My uncles built a Bensen glider in their apartment while they were in the Army stationed in PA. I don't know how - but they met up with a guy that had an interest in aviation. He had a boat, so when they finished their Gyro, he would pull them behind it on a lake.

That guy? Homer Kolb, the founder of Kolb Aviation. He remained good friends with my uncles and my dad and we'd always talk to him at Oshksosh during the EAA show.

They tried to fly that gyro with 4, 5hp 2 stroke engines. I guess it worked, but the power was marginal at best. A little after the 1 min mark, there's video of it being towed. Followed by some powered flight. Sorry about the quality - it's all they had back then!

 
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Doug Riley

Platinum Member
Joined
Jan 11, 2004
Messages
6,335
Hey, it flew, apparently even out of ground effect. They may have needed a couple more 5 hp. 2-strokes. Bensen built a gyro prototype with six of them; he called it the "Copter Cart."

Bensen's later model gyro, the B-80, did feature an all-aluminum "Erector set" engine mount, although the classic B-8M and Brock gyros used welded steel carriers, braced with aluminum angle. The engine mount in the pictures is similar, but not identical, to Bensen's B-80 mount.

I don't know about that "store-boughten" joystick pitch pivot. The pivot takes a surprising amount of punishment, not so much in cruising flight as in trailering, and in ground operations that involve rotor flapping, rough runways, or both. When joystick pivots fail, it makes for a very bad day.
 
Joined
Jun 18, 2019
Messages
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Location
Baraboo, WI
If you watch to the end of the video, they also built an ultralight and put the same 4 engines on it. Apparently they weren't exactly reliable - and they would rarely return from a flight with all 4 engines still running. Not a big deal for the ultralight, but the gyro needed all four at pretty much WOT to fly.

I don't think I'll be fixing the pivot bearings - or anything else for that matter. It's looking like a project that I just don't have time for right now.
 
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