Stainless

rcflier

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Hi Doug et al.

Denmark (all of Continental Europe, even) is metric.
So the 1/8" stainless plates - can they be 3 mm instead?

Cheers
Erik
 

Doug Riley

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Close enough, in my opinion.

Even better: use chromoly steel instead of stainless. Stainless reacts chemically with aluminum and is actually a poor choice of material for hardware to be attached to aluminum frame members. Stainless also is miserable stuff to cut and drill. Just prime and paint the plain steel.
 

rcflier

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Thank you for answering. Upon final assemby the aluminum would be coated with paint or something else.
But it's now possible to buy grade 5 Titanium - wouldn't that be best?

Cheers
Erik
 

C. Beaty

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Don’t be so harsh on pot and pan grade stainless steel (type 304). It is a highly ductile material, making it ideal for deep drawn shapes such as kitchen sinks and coffee pots. Its strength to weight ratio isn’t very high as compared to aircraft steels such as 4130 but that’s not important in hobycopters where the most important attribute is appearance. It’s pretty!
 

rcflier

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Hi Chuck - thanks for chiming in.

My problem is, (unspecified) SS is what the drawing calls for. So unless I have a very good reason, that's what I have to use (304 or old name 18/8).
But 1/8" is hard to get in Europe - and maybe the nut on the AN cluster plate bolt thread bottoms out if I use 3 mm?
There are so many hard-to-decide items on the Gyrobee list, that I'll make a new build manual if I ever get there.
I have to find a seat, before I can make the seat support angles. And I have to decide on material, thickness and availibility of
the cluster plates before I can get anywhere at all. And why not extend the cluster plates a bit forward to attach the bearing
block of whatever walking beam joystick I can build? That could be neat.

I could buy the lot off Starbee - but I'd much rather build (mostly) from scratch. Then it's MY build.

Cheers
Erik
 

C. Beaty

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Erik, 3mm sounds close enough to me. The difference between 0.125” and 3mm is 0.175mm. I can’t imagine the Gyrobee plans calling out SS cluster plates, I’ve never seen the plans but the specification must have been for 0.125” aluminum.
 

rcflier

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Hi Chuck.
The plans do indeed call for 1/8" stainless.
And since there is a cluster plate on both sides, it's .35 mm total.
I wonder if that'll make the nuts bottom out the threads...?
Anyway, I think I may be able to buy some 1/8 in the UK.

Cheers
Erik
 

eddie

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Its like Doug said,stainless is miserable to work with it galls when drilling or cutting,the best choice would be 4130 chromoly.
 

Boots

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I have stainless plates that attach at the mast to keel on my gyrobee . A good drill bit run slow will cut it just fine . But if you are going to stray from the plans and use larger plates 1/8 6061 t6 sheet may be ok 😀
This works well for drilling hard material
image.jpeg
 

gyromike

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rcflier;n1127469 said:
Hi Chuck.
The plans do indeed call for 1/8" stainless.
And since there is a cluster plate on both sides, it's .35 mm total.
I wonder if that'll make the nuts bottom out the threads...?
Anyway, I think I may be able to buy some 1/8 in the UK.

Cheers
Erik
That's only 0.015" less than 1/8" plate. Just use an extra washer.
AN washers come in various thicknesses, and if I remember correctly, acceptable practice allows up to 3 washers.
 

C. Beaty

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It’s all starting to come together for me; the Gyrobee was Ralph Taggart’s adaptation of Martin Hollomann’s Bumblebee, an adaptation of a Bensen B-8. Bensen used 1/8” inch aluminum cluster plates; no point in making the cluster plates stronger than the 1/8” wall aluminum airframe tubing. Anyhow, as others have stated, 3mm plates should be OK, just use an extra washer if the bolt threads bottom out.
 

curtisscholl

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I am very glad this subject came up. I too have decided on the GyroBee and all I can find at OnlineMetals in 304 stainless is the .120 rather than the .125. That said, looking at the specs between 304 and 6061-T6 aluminum, I find that the yield for 304 is 31000 PSI vs. the 37500 psi for T6. So, Aluminum cluster plates would be fine in my book. But that is my decision, based on the numbers and the experiences of other people that have done this before like Chuck Beaty, Gyrocopter Sensei.
 

rcflier

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Yes, I am very tempted to trust the very knowledgeable and experienced people here.
But I reckon the shock plate has to be stainless for purposes of wear?
I suppose Taggart is still alive, so I could ask him why.

Cheers
Erik
 

Brian Jackson

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There is also stainless used for the main gear strut brackets. I envision some serious shock loads applied there, though I admit it's tempting to use a thicker wall T6 AL channel. Besides lack of availability of odd sizes, is there a reason stainless is used for these parts?
 

C. Beaty

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curtisscholl;n1127532 said:
I am very glad this subject came up. I too have decided on the GyroBee and all I can find at OnlineMetals in 304 stainless is the .120 rather than the .125. That said, looking at the specs between 304 and 6061-T6 aluminum, I find that the yield for 304 is 31000 PSI vs. the 37500 psi for T6. So, Aluminum cluster plates would be fine in my book. But that is my decision, based on the numbers and the experiences of other people that have done this before like Chuck Beaty, Gyrocopter Sensei.
The yield strength of SS 304 is low because it’s intended for deep drawn shapes where it can be easily formed into complex shapes without tearing or breaking. That’s known as ductility.
It would never be used as a structural material for serious aircraft designs but it’s fine for hobbycopters where strength to weight ratio is not important.
 

rcflier

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So the reason behind choosing it over other materials could be, that when overloaded it deforms - but doesn't break?
And an open frame gyro is inspected regularly.

Cheers
Erik
 

Doug Riley

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I doubt there were any deep reasons for using SS on the Gyrobee. It's rust-resistant as long as it is exposed to oxygen. If cut off from oxygen, it will rust. It provokes serious "wasting" corrosion in aluminum that it contacts if not insulated from the aluminum by plastic, paint or other non-conductive coating.

Interestingly, my edition of the Bensen plans called out 1/8" 5052-H32 for the cluster plates (and rotor head cheek plates). And that's what came in the kit. This stuff takes and holds a better shine than 6061-T6, but is far more ductile and not nearly as strong. Bensen had us bend some parts out of the 1/8" plate, and I imagine that he used this softer material to reduce the chance of cracking at the bends.

The Gyrobee cluster plates are strips only 2" wide, mounted with 3/16" bolts. Bensen's, OTOH, are large triangular plates, with far-spaced 1/4" bolts. I'm sure that's why Hollmann and Taggart went to steel.

Again, I see no need for the steel to be stainless, and a couple good reasons for it NOT to be.
 

C. Beaty

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Someone recently told me that he was considering building a gyro from electrical conduit, commonly known as EMT (electrical metallic tubing).

I was horrified, knowing that EMT is designed for easy forming with simple hand tools, so told him that after a hard landing, he’d have instant spaghetti.

However, I looked up the physical properties of EMT and to my surprise, its properties are nearly identical to type 304 stainless steel, the material used for fabrication of most Eurotub airframes, the Magni being an exception.

The yield strength of 304 SS = 31,200 psi; the yield strength of EMT = 35,000 psi.

The downside of EMT is that it’s nasty stuff to weld; with welding heat, the zinc coating vaporizes and creates some noxious fumes. And of course, it’s not as pretty as SS.
 

Doug Riley

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...and the yield strength of 6061-T6 alloy is also in the 35,000 PSI neighborhood -- but steel weighs 2.5 times as much as aluminum. It just doesn't make a lot of sense to build an aircraft frame out of 35,000- KPSI steel.

Once you trade up to 4130, with a yield around 70,000 PSI, it starts to make SOME sense. It's still heavier for a given strength than 6061-T6, but you may be able to earn back that weight penalty because: (1) thin-wall steel tubing welded into trusses can be more precisely deployed, putting just enough metal in each spot to do the job (6061-T6 extrusions are clunkier) and (2) welding is a lighter form of joint-making than bolting (the bolts themselves are heavy, and the wall section must be heavy to carry the high point loads created by bolts and holes).

By the time you account for the issues of stress relief and corrosion protection of steel, though, it's roughly a toss-up between 4130 truss and Bensen's bolt-n-go construction, for what we do in small gyros.

In any event, I don't "get" the welded 304 deal at all. It appears to combine some of the unappealing aspects of both types of construction.
 

C. Beaty

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With consumer products, Doug, appearance and perception are paramount.

I expect oxcarts would sell better if equipped with tail fins and high speed hubcaps
 
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