Question For The Bensen Pros

FRANK'S

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I have a Bensen B8M
with a continental 65 that is about 175lbs
if I wanted to install a new set up that has a total weight of 220lbs
with 140hp would my double mass Bensen take this setup weight?

and if it does how do I go about changing the dry and wet weight of this?
would I need new rotors? or just a extension bar would do the trick.

Info on new engine.

140 hp @ 2600 rpm
135 lbs Torque @ 2300 rpm
will be setup fuel injection with rev limiter to not go over 3000 rpm
 

JPAnderson

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My two bits. It's no longer a Bensen. Continental A65 is well over double the vibrating mass of the McCulloch. You're far over the designers gross weight limits. It's a totally new design when you make those many changes.
 

Alan_Cheatham

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Your numbers seem off:

140 hp @ 2600 rpm = 282.8 ft/lbs of torque

135 ft/lbs torque @ 2300 rpm = 59.12 hp


Assuming direct drive figure 283 ft/lbs torque at the prop, over double what your original figures indicated.

.
 

dabkb2

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It does not sound like it will weigh much more than a VW motor. You might need to change the check plates to get the stick right. I have heard of a 65 on a Bensen and it was good
 

JPAnderson

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If memory serves me the VW is about 160lbs, Continental C-85 185lbs without starter or alternator, A-65 maybe 10 less, Lycoming O-235 215 without starter or alternator. Mac is south of 100lbs. That airframe was designed for a gross <600lbs.

Maybe I'm a little conservative but my goal is saving weight not adding and sticking to the plans. The unsprung beam axle on the Bensen seems a little weak for the weights you suggest.

Wasn't the Barnett designed for a Continental or Lycoming? I'm surprised there's never been more Experimental Gyros designed from the start for a O-200 or O-320. They are great motors.
 
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JPAnderson

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I bought a Mac powered Bensen back in December at an auction. The airframe ended up being junk. Elongated holes by the bushel, non-aircraft hardware, steel wheels, Steel nose wheel, 6061-T6 replaced with with soft aluminum angle.

The only thing useable were the blades, hubs, rotor head, joystick. Motors will work as rebuildable cores. The rest went in the recycle bin.

I started building a new airframe using KB-2 plans I bought in 1981.
 

phantom

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That machine flew real well with the A 65 when I saw it flown by Agust Carlow.
I would fly it the way it is for a while and start working on another one if I wanted something different, I would replace the blades, I have a set that is the same age that are starting to delaminate so you need to check them carefully.
Norm.
 

JPAnderson

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I have about 150 hours behind an A-65 and 575 in front of a C-85. I fixed a lot of pesky oil leaks but they never let me down. The Stromberg carb is a nice simple carb that works really well.

I have a dismantled A-65 that needs the crank ground. I don't think I'd like it on Bensen airframe but I'd like it on a Gyro. I'd build it up as a A-80, balance it nice, electronic ignition and overturn it to about 2800rpm or even a bit more. It'd be a cruiser.

I might have to look for some Barnett plans someday. I like this video. This is a bit North of us but we have similar terrain.

https://www.youtube.com/watch?v=tUMG8Z4fxXs&t=9s

John
 
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FRANK'S

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Your numbers seem off:

140 hp @ 2600 rpm = 282.8 ft/lbs of torque

135 ft/lbs torque @ 2300 rpm = 59.12 hp


Assuming direct drive figure 283 ft/lbs torque at the prop, over double what your original figures indicated.

.

custom built push rod race engine numbers are estimations. but very close
 

FRANK'S

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That machine flew real well with the A 65 when I saw it flown by Agust Carlow.
I would fly it the way it is for a while and start working on another one if I wanted something different, I would replace the blades, I have a set that is the same age that are starting to delaminate so you need to check them carefully.
Norm.


thanks for the warning with the blades.

I would love to fly that A65 but starting it scares my shoulders and my elbows and tendinitis. if it had a starter I would fly the A65.
 

FRANK'S

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I have about 150 hours behind an A-65 and 575 in front of a C-85. I fixed a lot of pesky oil leaks but they never let me down. The Stromberg carb is a nice simple carb that works really well.

I have a dismantled A-65 that needs the crank ground. I don't think I'd like it on Bensen airframe but I'd like it on a Gyro. I'd build it up as a A-80, balance it nice, electronic ignition and overturn it to about 2800rpm or even a bit more. It'd be a cruiser.

I might have to look for some Barnett plans someday. I like this video. This is a bit North of us but we have similar terrain.

https://www.youtube.com/watch?v=tUMG8Z4fxXs&t=9s

John

Having a proper starter on my A65 would be awasome.
 

FRANK'S

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Your numbers seem off:

140 hp @ 2600 rpm = 282.8 ft/lbs of torque

135 ft/lbs torque @ 2300 rpm = 59.12 hp


Assuming direct drive figure 283 ft/lbs torque at the prop, over double what your original figures indicated.

.

4 cylinder push rod engine

stock specs;

HP 100hp 2600 rpm
Torque 135lbs at 2300 rpm


more info
engine is 2.5 liter now .30in over with high torque racing cam
smaller c.c. 240psi compression


OK I found my info I was wrong on RPM for HP numbers.

CFI fuel injection
Horsepower 100 HP @ 4100 rpm
Torque 135lb-ft @ 2100 rpm

MPFI
Horsepower 100 HP @ 4400 rpm
Torque 135lb-ft @ 2600 rpm

so my RPM for HP was wrong.
 
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Gyro28866

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Post #7:
6061-T6 replaced with with soft aluminum angle.

Are you saying that you replaced the 6061-T6 components, with a different grade of aluminum?
 

JPAnderson

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Are you saying that you replaced the 6061-T6 components, with a different grade of aluminum?

NO. It was on the airframe when I bought it at auction as well as having a bunch of non-AN hardware. I threw it all in the scrap pile and I'm starting over.
 
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