New Hard Point Exponential Handle design

[Steve Helmick]

Yes, neutral is neutral

The answer I was looking for was more like "Yes, the Derek Moran-style clips will fit onto the aluminum Expo-doodads just fine."

Pretty sure that the stainless steel bits of the TED Handle are laser cut and tumble polished, as are the plywood and balsa parts.
Well, except the wooden bits aren't tumble polished.

FWIW, in a similar sort of small angle rotation (circle towhooks in F1A's), where a lot of guys were using spacers and bushings
and such, I just tapped mine (3/16" total thickness 6061T6) for the 4-40 pivot screw and let it ride on the threads...more
surface area, no special screws, no spacers, no bushings, and no problems.  A bit of dry molylube or graphite, and you're golden.   
Loads were about the same, considering that the load is carried with two for CL, and one for F1A.  Steve   

[Larry Renger]

Quote: "The answer I was looking for was more like "Yes, the Derek Moran-style clips will fit onto the aluminum Expo-doodads just fine."" Yup, they are what I use all the time. 

[Larry Renger]

Today at the Valley Circle Burners Fun Fly, Ray Firkins was courageous enough to fly my Ringmaster and then his own, beautiful Primary Force electric with my latest handle incarnation. 

He was well pleased and gave me some valuable input. I have revised the design to deal with his concerns, and so I plan to build the Mk 3 version tomorrow. Hopefully, it just gets better the more people who fly it.

So far so good!   

[Howard Rush]

What's the change, and have you pull tested the last one?

[Larry Renger]

No, I haven't pull tested it. I doubt anything reasonable is going to pull 4X40 bolts at right angles through 1/2" of birch plywood. Nor are the 3/32" links likely to fail. But I guess I should just to say I did.

The changes are that I lowered the hand position about 3/16" to even it out. Although the design was perfectly symmetrical, it worked out to feel biased to the upside. The second change is a modification to the geometry to reduce the effective linkage length 1/4" to lessen the exponential effect a bit. The previous change was to move the pivot points together about 1/2" as the handle was too sensitive for me.

.pdf attached

Using only my scroll saw and drill press, it takes about 4 hours to make the handle. Of course with laser cut wood and waterjet metal parts, it would take WAY less time.    But first, it needs more testing and fine tuning.  I love it as is and it is only getting better.

[Howard Rush]

Did you pull test the plastic one?  I worry about the hole spacing, given the way the printer makes reinforced holes.

[Larry Renger]

OK I'll put the plastic one back together and pull it. Will 50 pounds do? I have reused the original set of links in the Mark 2, but it is easy enough to reinstall them in your plastic version for a test.

Mark 3 is assembled, shaped, sanded and ready for finish tomorrow. I want this one to be really nice, so it may take a couple of days to apply a finish. Links are the hard part and took a few hours to saw out, finish file to accurate shape, chamfer all the edges and do the bushings. But once done, it should last forever. (Unlike the planes it controlls) 

Haven't quite got the knack of shaping eyelets properly, this set is a mess, but it will work.

I have an eyelet set tool, but it is metric. Where can I get a domestic size set? Or metric eyelets?

[Larry Renger]

OK, the plastic version you sent was set up in the outermost holes, which should be the weakest. 50 lb of steel workout weights. Easier on the handle than me, I think. Anyway, even bouncing the weights up and down a bit, absolutely no indication of failure.

 

[Larry Renger]

Just flew the Mk 2 hande on my RSM P-51, and it was way too much. I'll have to see if it can be desensitized some more, or does that model just require the older style handle? Too much line spacing or too much expo? We will have to see.

I guess it will require a Mk 4 to see if a Mk 4 version will be the fix.  

[phil c]

Coming to this late I can see why Jim Hoffman said the difference if feel was slight.  Going by the drawing when you give up by rotating your wrist the up line stays on its forward stop and the bottom line moves back.  Most people seem to have a wrist joint that is about 3-4in. back from the line attach points.  So using your wrist for control, or playing with your outer fingers for fine tuning, the actual overhang on the up line doesn't change much if at all.  The down line gets a slightly longer lever arm but still has the same tension on it(determined by the balance of the control forces) so there is slightly more pull on the down line than usual.

All the force to move the controls comes through the up line(for an inside maneuver).  The down line is just along for the ride.  To really increase the control movement when the handle is tilted the upper control arm would have to move away from the center of the handle.  This handle appears to change the feel by effectively reducing the difference felt in the hand during a manuever by slightly increasing the pressure felt by the hand by increasing the lever arm for the less loaded line.  The less loaded line moves away from the axis between the wrist and the center of the handle.

It should certainly change the feel of a plane.  Some people might like it, some not.  Anybody who uses their whole arm, or elbow probably won't feel any difference.

[Larry Renger]

I am not quite getting at what you are saying. The line spacing increases on the latest version by 1/2" compared to reducing by about 1/4" with a fixed handle. Surely that increases control sensitivity at full deflection?

Yes the overhang effect is affected by the wrist to eyelet distance, but that is not what this quest is all about.

My goal with this concept is to smooth out level flight, provide smooth round maneuvers and finally have major kick for the corners. Frankly, my latest version may have gone too far. I have sent one to Jim Hoffman for his expert opinion.

Breathlessly awaiting flight testing!

Thinking about it, if the handle spacing is greater than the bellcrank width, you already get a bit of increased sensitivity with deflection. So maybe I am beating a dead horse?