A new Hornet Started in MN

[IGoTooFar]

Well, I have made some progress on my new Hornet, Denis has done a wonderfull job with making most of the parts, I have been researching and ordering pretty much everything else. It is a great team effort, and I think I have the easier job. :peace:

Here a a bunch of pic's of my progress. (all bolts are temporary)

[IGoTooFar]

More Pic's

[jany77]

looks good what rotor are you planing to use

[ultracruiser41]

Need to shock mount the engine.

Possibly a temporary set up in the photo?

[IGoTooFar]

looks good what rotor are you planing to use

I have a set of 23' DW's on the way.

[Earthboundmisft]

Dig those tapered rod end spacers...

[IGoTooFar]

Dig those tapered rod end spacers...

Yeah, that was all Denis, those are very cool.

[MattPearson]

Looks very nice!
My .02.. I hope that you are going to flip that redrive down. It doesn't make since to go to the effort of a drop keel and then raise the thrustline.
I'm very concerned about those holes drilled in the mast above the engine mount. There should NEVER be holes drilled in the mast above the engine mount, and even there it's better to clamp around the mast, and then maybe put one bolt right thru the center at the neutral part of the material.

[Passin' Thru]

Looks very nice!
My .02.. I hope that you are going to flip that redrive down. It doesn't make since to go to the effort of a drop keel and then raise the thrustline.
Those were my thoughts exaactly, - but the craftmanship is so nice, I just hated to say anything! :eek::sorry:

[MattPearson]

I hereby give permission to anyone that has a safety concern about my aircraft to risk hurting my gigantic ego, by questioning me! :peace:

[IGoTooFar]

Need to shock mount the engine.

Possibly a temporary set up in the photo?

Yep, I just sat the engine there for the pic, my Jerry Shocks are going to be delivered Tuesday.

[IGoTooFar]

Looks very nice!
My .02.. I hope that you are going to flip that redrive down. It doesn't make since to go to the effort of a drop keel and then raise the thrustline.
I'm very concerned about those holes drilled in the mast above the engine mount. There should NEVER be holes drilled in the mast above the engine mount, and even there it's better to clamp around the mast, and then maybe put one bolt right thru the center at the neutral part of the material.

Yeah, the engine is, as it was delivered. Now on to the holes in the Mast.

The only holes in the mast are for the Folding Mast, Control Rods and the Head Check plates. These are all exactly as called for in the plans.

Tell me more about your thoughts/concerns.

[robo_nipsy]

Matt, Passin',
Thanks for the input. Any tips are much appreciated!

As Brent mentioned, this is what the plans called for...However (and no disrespect to Don as I think he has done a wonderful job putting this design together) we do realize that this is a design that several builders are working on, yet there are very few that have seen air under their tires and therefore, the design is yet very far from being "proven".

Now, while I have had MANY years of working with all sorts of metals and machine design, and have seen first hand and do have a good gut feel as to what works and what doesn't, We admit, that Brent and I are new to the gyro world and and we ask, plead, beg, that anyone on this board that has more experience than us (aka EVERYBODY) will chime in if they see something that we are doing that doesn't look right to them!!!

I would just like to further discuss some thoughts on the attachment point concept a bit further...

Don's plans call out for the drilling in the upper mast, but he uses these acetal (Delrin) insert blocks at the attachment points to carry the "crush" load of the bolts. (Insert Detail .jpg).
I have machined these to approx .001" under the ID measurement of the mast tube. I waited till I had the mast material in house before making these parts to assure and exact fit with the extrusion. This will assure that there is almost 0 deflection or displacement of the mast material when the bolts are tightened. Also, you will see that on the insert, the holes are place 1/2" from the end....On the attachment plate, the holes are 3/8" in. This isn't much, but it will will give a slight "feathered" transition from the rigid sandwiched connection point to the rest of the mast tube to as to reduce the focus of stresses.
This sandwiched assembly seems to me to reduce a lot of the negative aspects of the drilled mast. (Not a moot point, but greatly reduced). The material directly around these drilled holes will see very little (if any) fatigue.

I drew up a little alternate arrangement as you mentioned Matt, but doesn't this arrangement have it's own concerns?
Also attached is a optional seat brace. I just placed this one above the original for illustration. The original is on bottom the new proposed is on top.
I made the mast transparent blue...You can see the insert block inside.
With Matt's suggestion (which MANY designs use) isn't virtually all the clamping force directed onto the mast tube corners which I have colored red? (not including the optional green bolt you mentioned) All the clamping force relies on the rigidity of the plates. If the plates bend of fatigue at the red lines, the the amount of clamping force is reduced.

I also included a picture of the folding mast section. This used the same insert configuration, but with a rather stout polyurethane insert around the main pivot point. This uses the same through bolting arrangement.
And to be honest, there is NO WAY that I would go up in a machine that only had the mast secured to the rest of the machine with a saddle clamp arrangement! (I don't trust simple friction that much!) ;)

And then of course, the top is drilled for the rotor head cheek plates like all designs that I have seen use......

Is it just the center section of the upper mast the area of concern for you guys??? Because of the flexing and fatigue that could be focused in this area around such features?

I hope to get a lot of replies...(Both positive and negative)

Let us have it!

Thanks

Denis

[RotoPlane]

And to be honest, there is NO WAY that I would go up in a machine that only had the mast secured to the rest of the machine with a saddle clamp arrangement! (I don't trust simple friction that much!)

Nor do I trust friction in this case, or with any clamping arangement. In detail #3, the "optional" centered bolt should not and would not be optional on my machine and would include a tube spacer....the other four outside clamping bolts then are okay.

[Minnesota_Mike]

I do not share the concern about holes being drilled in the mast ON THIS DESIGN near the Engine mount.
Holes are drilled in masts...and they need to be there to attach the Gimbal Head and like wise the keel. To many holes and the poor placement of them IS THE PROBLEM to avoid.
The origin of those concerns was on the single 2 x 2 swept back Bensen mast designs...upon severe blade impacts- the torsional forces traveling through the mast tended to twist the mast. The twisting forces acted greatly upon the first main weak point in the mast where the holes were located at...the top of the seat mount. The twisting would nearly sheer the mast at that point. I read about several accidents wherein this situation ended in bad injuries. This lead to the dual 1 x 2 redundant design to be implemented. The mast needs SOME flexibility to it, but too stiff is as big a problem as too flexible. The swept back (9 degree) design favored on Bensens' allows for the mast to remain in tension pulling down perpendicular to the rotors, unlike this design that pulls it backwards slightly, hence the need for that diagonal brace to ease the rearward pulling forces on the mast.
To mount that brace- a "sandwich" solution (bolts around the mast) WITH THE BLOCK FRICTION FIT INSIDE I'd think is more preferable than any drilled holes going through that block.
Drilling holes would only introduce a point of weakness high on the mast defeating the redundant support design seen here (which looks good at distributing forces and loads).
This is especially true since this Airframe design calls for a SINGLE 2 x 2 mast in the plans.
I, myself would have preferred a redundant 1 x 2 design...just more metal for safety sake.
But that would have probably pushed the over all weight to high for this original design to qualify as "Ultra Light".

I think your BOTH gonna have a great machine here when finished.
I would NOT drill holes for that top support...a "Sandwich" fit is better. You'd be surprised how tight that will hold in regrads to any possible "Slip".
If the Airframe needs it, you'll want slip right there. Besides, if that much rearward force is acting on the mast FORCING slip, some give there will help dampen those forces, instead of isolating them to weak points due to drilled holes.

Just my two cents.

M-M

[Dirtydog]

robo_nipsy :
That was a point I just looked at and said too! To many hole and to close together.
What is above that piece?

[Resasi]

My son's decision was to retain the one piece mast from the earlier design as he didn't like the idea of the two piece.

This however is braced quite high. We may find we have too stiff a mast.

You're right about not too many having flown. Be good to get some in the air and find out more about how they perform.

Roy Freeberg, whose hanger we fortunately share has one of these flying examples. He is delighted with it.

Greg Spicola who has a lot more flying experience has flown this particular machine and might, if he sees this thread, give us a comment or two on how it flies.

[Dean_Dolph]

I don't know if I need to include my usual disclaimer here so won't! But, this thread is timely in that it coincided with Mentone and the incident that happened there.

If you get a chance to see after incident pix of the early Air Command that was involved, you will see that the mast snapped right at the hole in the mast right above the pilots shoulders. I don't know if that hole was part of the original design or not but it is not unusual to find a hole in that area from builders who haven't witnessed this type of mast failure. It has nothing to do with fatigue as such but is a safety issue during a roll over or other incident that imposes great forces on the mast.

This is a well known weakness and design fault and consequently the 'clamp on' is favored over mast drilling. I've never heard of a clamp slipping but then I'm not privy to everything that goes wrong.

[Resasi]

Dean a timely reminder.

If it had not been for such a warning on the forum we may well have been tempted to put bolts through the mast for the seat belt mountings.

All sorts of advice on this forum has been invaluable for many aspects of the build process.