bensen cheek plates/hangtest

[drleon]

anyone out there that can tell me what grade of alum the cheek plates should be?
what is the correct procedure for the hang test with a seat tank?]
i have altered the engine, can the cheek plates be changed to keep the cog correct, or do i ad weight to the front

[gyromike]

Leon,

6061-T6 is the grade of aluminum that you need.

The hang test is the same with a seat tank, or with the outboard tank.

And yes, you change the cheek plates to get it to hang correctly instead of adding weight.

[drleon]

Would 6082/t6 Be Suitable
No-one In South Africa Stocks 6061/t6 That's Thick Enough?
Does Anyone Know If 6082/t6 Would Be Suitable To Make A Longer Hub?
I Have The Standard Bensen Aluminium Blades And Want To Increase The Total Diameter
In Th Long Run Will Go For Dragon Wings
Will They Fir On My Rotor Head Or Do I Need A New One?

[Bob]

A Haing test should be done with 1/2 tank of fuel and you with all your gear on in the seat .
...
the same should be done for the ballance test so you can find the cog or com....
as far as the cheek plates go I don't know what 6082/t6 is so I can't help ya there...
Most head cheekplates are made with 1/8" thick 6061/t6 plate though..
( that i know of anyway ) I made the cheekplates out of 3/16" alum plate because I thought the 1/8" seamed kind'a thin to be holding all that weight ! ... but thats just me too ! <grin>
....
the way I figure it ... when in doubt go with the next size in thickness available and you should be fine .
....
The first thing I did when I got my gyro was to start modifying it ...
and later i wish I hadn't !!!!! it threw off my com by a long way ...
even doing what was logical and lowering the engine !!!! I later had to re do that and drop the keel to finally get the thrust line offset to a tollarable level ...from 14" down to 5" or 6" as it is now ...
.....
increaseing the Rotor diamator can be done with a longer hub bar .
infact its probly the easiest and cheepest way to go , though some folk don't like long hub bars .
the folks at KBM ( Ken Brock Manifactureing ) handle alot of parts for benson type machines you might check them out .
www.Kenbrockmfg.com I think is the URL

Also I bought the 1"x3"x4' 6061/t6 Alum I needed for my hub bar from these folks ! www.Onlinemetals.com best prices I've seen too !


hope that helps

Bob......

[scottessex]

I don't know about 6082, you might have to look it up and see what you can find out. 6063 is about 1/2 the strength of 6061, so make sure.

2024T-3 is stronger than 6061T-6 if you can find it it would be a suitable alternative, but paint it, as the 2000 series aluminum is more subseptable to corrosion.

[drleon]

i have made a set of cheekplates from 3.5mm, i think 1/8, 4130 aircraft grade, certified stainless steel
6061t6 not available in south africa
anyone's thoughts?
i found a piece of certifies 7075-t6 which the sycamore gyro's use
i want to use it for my hub bar, same dimension as the 3ft bar
will it be ok?

[Doug Riley]

I guess only the gyro senior citizens recall that Bensen specified 5052-H32 for the head plates on the B-8 -- at least in the version of the plans that I bought in 1969. This material is much softer and weaker than 6061-T6, but it does hold a nice shine. Bensen's choice indicates to me that any alloy with characteristics close to 6061-T6 is appropriate.

6061-T6 has a tensile yield strength of about 35,000 psi. This means that a 2" wide strip of 1/8" 6061-T6 sheet, with two 1/4" bolt holes drilled in a line across the direction of load, will permanently deform in tension under a load of about 6500 lb. The actual number will be lower because of the stress-magnifying effect near the holes but, OTOH, there are two head plates, not one.

Extremely thick, rigid head plates (such as those of steel) put more twisting load into the mast tube when prerotating. I don't mind seeing the plates take their share.