New Hard Point Exponential Handle design

[Larry Renger]

As mentioned (often) I am a fan of exponential control handles. There was valid criticism in another thread that my current design has too much "overhang" and that makes the controls need a heavy hand. This limits the usefulness to rather light models. 

Challenge accepted!  See the attached .pdf for my new low overhang version. The goal is to have the spacing hit maximum slightly wider than you would normally space the lines and slightly less when at neutral.

Now, before finalizing the design, I need some input from the assembled multitude! What is the range of handle line spacing in common use? Please tell me what you guys actually use. 

Thanks!

[Gerald Arana]

Interesting idea Larry. Let us know how it works out for you.

Tight lines, Jerry

[Andrew Tinsley]

Hello Larry,
My line width is usually around the 4 inch mark, but then I am not a very good pilot!
I think it seems to be a very neat idea. One that is obvious once you have seen the drawings! I am not quite sure why you have gone to the U shaped swivel pieces, maybe a thick oblong would do the job? Now tell me where I am going wrong! Oh yes, it allows a much wider line spacing if necessary! The idea is just great!

Andrew.

[Tim Wescott]

I've gone as low as 2", but (A) I tend to use less spacing at the handle than most people, and (B) the plane had problems that I since corrected.  I certainly go down to 3" regularly.

[Steve Helmick]

Typically, I try to get to 3" plus. It looks like this handle is just a bit too wide for my current planes.  Would love to try this handle; the sooner the better! I assume the "U" fittings would be stout enough for a 45 lb pull test? Titanium?  Steve

[Brent Williams]

Garolite, G10, FR4, are good materials that are readily available.
McMaster Carr has them in suitable thicknesses. 
It will kill saw blades.  Use a fresh drill bit.

[Larry Renger]

Typically, I try to get to 3" plus. It looks like this handle is just a bit too wide for my current planes.  Would love to try this handle; the sooner the better! I assume the "U" fittings would be stout enough for a 45 lb pull test? Titanium?  Steve

I think that 3/32" steel will do nicely!

The handle can be bigger or smaller, which is why I need to know the typical range used by a wide range of pilots. It would not be hard to have larger and smaller versions since it is just a matter of putting the correct file into the laser cutter. The links stay the same.

[Steve Helmick]

Are you trying to beat the hot rock handle? 

That's been done a couple of decades ago, with Ted Fancher's hardpoint design. It is a kit, so you can make it fit your hand either like a Hot Rock, or whatever you like, whichever comes first. Plus, it discards of the cables and their potential for breaking at a bad time...ask Howard! But if you like the Hot Rock and disregard something that's MUCH better, go right ahead.  Steve

[Larry Renger]

  (except I can't find a decent 1.5 square battery.) quote

I remember seeing a fake battery that took 4 D cells inside. Would be way better than the original, but look right. Don' remember where, sorry.

[bill bischoff]

  (except I can't find a decent 1.5 square battery.) 
Tower Hobbies HCAP0700 $5.99

[George Albo]

Yes, I am locked into old school.  Vintage.  Why have a vintage plane with a modern engine, carbon fiber bell crank, a scientifically designed handle and modern engineered prop?   I have to decided to be a complete vintage flyer, with all items being era correct.  (except I can't find a decent 1.5 square battery.)  I do have the white Top Flite and wood props that are date correct, though. 

Seriously,  I am glad a equipment advantage is being sought.  I have seen people use what I got and fly 10x better than me, so at this time I know the improvement needs to be me, not equipment. 

It looks nice.  I hope it works out.

Here. See if this site has what you need. http://www.radiolaguy.com/Batteries/Vintage_Batteries.htm     Make color copy and epoxy to existing battery. I'll be making an EverReady 1.5 volt linemans battery. Collecting materials to make including knurled brass line connector. Will post pictures when done.   Have fun.  George Albo

[david beazley]

Here's an old thread. I made a couple.
http://stunthanger.com/smf/open-forum/replica-dry-cell-battery/msg386461/#msg386461

[Larry Renger]

Come on guys, I need all the input on average, actual use line widths I can get. I would really like to only do this once! 

I think these handles could work well for many people, but if I get the spacing wrong, it is a waste of time and effort! 

Work with me here. 

[BillP]

I fly large and small hot rocks and the 4" small is my preferred go to handle...but would like to try 3 to 3.5".

bp

[Howard Rush]

What are those squares on the side of the handle?

[Larry Renger]

Those are cut out areas to reduce the handle weight.

[Carl Cisneros]

Larry

as drawn,the handle would suite me to a treat. I have 3 planes that use the 3 1/2" spacing and 2 with
the 4" spacing to fly and feel comfortable with.

I like the idea of being able to adjust the width using the bolt locations.
The only thing I wouldlike to see would be some way to actually do minor line length adjustments especially from switching
from one plane to another. ( I know, we all should have a dedicated hanlde per plane. )

Also, one other thing yours has that the others do no have (from what I have seen as least) is the hole for the
wrist lanyard. Excellent thought.

Carl

[Larry Renger]

If you have adjustable line length built into the handle, you end up with some angular bias that changes the rate of inside to outside maneuvers. 

This handle is designed to be used exactly at right angles to the lines.

I finished making the links and am awaiting the laser cut wood parts. 

[Allan Perret]

3.25" at neutral with the links in center holes.

[Curare]

Larry, considering you've been fiddling with expo handles for the little stuff for a while, maybe you can tell us of the difference in feel?

I'd be expecting there'd be a resounding clank come through the handle on eights (inside to outside)?

[Larry Renger]

I have "Essential Familial Tremor", that is, my hands are very shakey, especially when I try to do something precise.  As such, the exponential handle helps me fly smoothly at level and round maneuvers while giving the kick needed to do square corners. This is especially important with responsive models such as we fly in 1cc (1/2A metric size).

I have never noticed any "clank", nor has anyone else who has tried the handles.  Jim Hoffman recently borrowed one of mine, and promptly ordered one for himself. Perhaps he will comment?

[Jim Hoffman]

I borrowed an Expo handle from Larry in March and did some trials on a very good flying Ringmaster.  I found a subtle but interesting change in the feel of square maneuvers.  I also measured the Expo handle and found it had overhang 1 inch greater than my normal handles.  This added overhang will increase the control loads one feels at the handle and would likely not be happy for me on a larger stunter.   This is what prompted Larry to create the “lower overhand” design he shared at the first post on this thread. 

I put together my own handle and have attached some photos.  This is an earlier generation handle than the “low overhang” Expo Larry shared in this post. 

Notice how the handle operates; as you come off neutral, one link rotates outwardly to oppose the reduced spacing that occurs during handle deflection.  I hope to do some flight trails this week on both the Ringmaster (26 oz.) and a slight larger OTS Galloping Comedian (35 oz.).   I have a 45 oz. Nobler (Aerotiger 36) that is a candidate for trials later.

Allow me to say that I set up my models with a more sensitive control feel than most, also at this time any change in feel is subtle.  There is no “clank” I notice

I really do commend Larry for his fine and creative engineering on both the handle I have and the low overhang version posted.

Jim Hoffman

[Howard Rush]

Has anybody calculated the kinematics of a control handle?  I think it might give some insight into what "overhang" does.  One could then go on to see what Larry's handle does.   

[Larry Renger]

Ooooh, a big word!

What exactly do you have in mind to calculate? The rate of line width vs deflection compared to a regular handle would not be that hard, or do you have in mind the relative torque required for a given line spacing?

Either one could be done.

But frankly, Scarlett, I don't give a 

So if you want to know, go for it and tell the rest of us. I know you can do it! 

[Howard Rush]

What?  You go to all the bother of having a handle 3D printed and you don't know what it does? 

[Steve Helmick]

I saw Howard's 3D printed "Hot Rock-ish" at last NW Skyraider's meeting. We all knew what it did...it did weigh a lot. Light handles count, which I'm afraid may also be a problem with Larry's new handle design. I don't mind my 60 gram TED handles, but might not like heavier than that.  Steve

[Jim Hoffman]

I flew the Expo Handle on the Ringmaster yesterday.  Any difference in feel between it and a traditional handle is subtle and may or may not be noticeable to the pilot.  The Ringmaster flew well and was very comfortable in the round and square maneuvers.

I tried watching the handle actuate during maneuvers.  I do not recommend that anybody try this.  I had my pal join me in the circle and observe the links move.  They definitely moved as designed in both the round and square maneuvers.  I was not sure my handle motion was enough to actuate during the round maneuvers, but observation showed that they certainly do move in the rounds.

Sorry I cannot say WOW, WHAT A DIFFERENCE, but it was positive and I will continue testing on other planes as time permits.

FWIW both handles in the photo weight 1.8 oz  (51 Grams)

Jim Hoffman

[Larry Renger]

There are major lightening holes inside the handle and it is hollow in front of the grip. 

[Howard Rush]

I took the CAD drawing and got the following:
for δhandle < -30.71 degrees, a_up = 2.48", c_up = 1.23", a_down = 1.63", c_down = 1.43"
for -30.71 degrees < δhandle < -4.79 degrees , a_up = 1.75", c_up = 0, a_down = 1.63", c_down = 1.43"
for |δhandle| < 4.79 degrees, a = 1.75, c = 0
for  4.79 degrees < δhandle < 30.71 degrees , a_up = 1.63", c_up = 1.43", a_down = 1.75", c_down = 0
for 30.71 degrees < δhandle, a_up = 1.63", c_up = 1.43", a_down = 2.48", c_down = 1.23"

See the other handle thread for definitions and pictures.  Here's the plot.  Did I do that right?

Edit: No, I obviously didn't do it right.  I fixed the plot.  I should have also noted that the conventional handle to which I'm comparing Larry's has the lines 3.5" apart (a_up = a_down = 1.75")

[Curare]

Howard, you've shown us a pretty interesting graph for force. How about ciphering what kind of  control surface deflection/handle angle we would expect.

For those of us who can't math.

[Howard Rush]

Howard, you've shown us a pretty interesting graph for force. How about ciphering what kind of  control surface deflection/handle angle we would expect.

Good point.  That's more pertinent to this exponential handle discussion.  I'll see if I can.

[Target]

Looking at the picture of the two handles, I'd say that the expo handle can be made a bit narrower between the grip and the front pivot area, if someone wanted to make their own, and didn't have fat fingers.

[Perry Rose]

What design features eliminate binding ,slop and friction at the pivot points?

[Larry Renger]

It is wonderful to have a fairy (his wife would argue that!) godfather! A wonderful surprise arrived in my mailbox. Howard Rush took my basic 2-D drawings, converted them to 3-D and 3-D printed out my handle design! 

I am blown away at the speed that he could do that and that he was interested enough to do it! My undying gratitude to him. It is perfect, and probably better and lighter than the plywood parts I intended to use. 

Anyway, the handle was finished within the hour of the main unit arriving, and it weighs under 1.5 ounces. I plan to fly it next week, ASAP! All I had to do is enlarge the holes on one side to fit 4-40 bolts and chamfer the holes for the flat head screws, then tap the other side for the screws. The slow part was adding the safety thong! And he did have a hole for that in the design.

Here it ready to go!

[Larry Renger]

What design features eliminate binding ,slop and friction at the pivot points?

Those problems just haven't happened. On both the old design and the new one, the links are bushed by brass tubing over the steel bolts. The side loads seem not to be a problem, so I have no reports of binding, and there is no "slop" in the system. Friction has not been reported either, though you could take some measures to eliminate that if you really want to. Grease is good.

[john e. holliday]

Larry,  how much pull will the 3D handle take?  Also can he do this within reasonable cost with extra holes for line spacing?

[Larry Renger]

The handle should take anything you can give it once the links are made of steel. The set in the photos is 3/32' thick Aluminum and I can't visualize them failing either. The old handles used 1/16" Aluminum and none have failed.

Line spacing is achieved by moving the links to the next pivot holes out. This isn't like any other handle where you can just drill more holes.

[Larry Renger]

I finally got a flight in on the new handle. I flew my Ringmaster with the Ceramic L&J Fox .35. Up till now it seemed heavy and sluggish. 

Wow, what a difference the reduced overhang makes! 

You guys were right on the button on that being an issue with larger models. 

The model's control inputs are now light as a feather, and with the increased exponential of the new design, corners are sharp as can be! It is still smooth at neutral, as I expected.

I'm in love!!! 

[Steve Helmick]

We had a NW Skyraider's meeting only last Tuesday. Howard had nothing for Show & Tell. Maybe he will have one of these at the Judging Clinic tomorrow? He swears that his new "Poland" Impact will be in attendance.    Steve

[Larry Renger]

I have offered to make him a set of the links, pressure him to accept and make a handle for you guys to play with! 

[Steve Helmick]

I have offered to make him a set of the links, pressure him to accept and make a handle for you guys to play with! 

Roger, that! It would be very interesting to have one to pass around and try out. It should be possible to just remove the clips from a TED Handle and plug the lines and clips onto a LARRY Expo Handle, no? Maybe not what one would want to do the weekend before a contest, but otherwise, sure...perhaps use an older model, for sure. Maybe we could get PW to try one out on one of his B-17 stunters?      Steve

[Jim Hoffman]

This week I had an opportunity to take enough flights on the Expo handle to come to two conclusions for myself:

1)   I prefer the Expo on the light weight Ringmaster due to what I perceive as benefits in the vertical eight.  To do a rule book vertical 8, keep the shape, intersection AND keep the apex of the top loop over my head, the increased gain during the top loop is beneficial.  I will likely keep an Expo handle paired with this airplane.

2)   The Expo handle is not an advantage on a ship that is lift challenged.  I tried the Expo handle on my OTS Galloping Comedian.  This airplane has a very thin wing and can be easily stalled.  It flies well but requires significant finesse to fly a quality appearing pattern.  I’ve seen this design flown very fast (4.0 second laps) to compensate for the thin wing, I fly at 5.0 sec/lap.  I quickly noticed that the Expos handle caused me to over control and stall in a few spots in the OTS pattern.  Not a good combination.

Hope this real world testing is helpful.
Jim Hoffman

[Larry Renger]

"Reality trump theory every time!" Old Confucius saying.

[Doug Moon]

It is wonderful to have a fairy (his wife would argue that!) godfather! A wonderful surprise arrived in my mailbox. Howard Rush took my basic 2-D drawings, converted them to 3-D and 3-D printed out my handle design! 

I am blown away at the speed that he could do that and that he was interested enough to do it! My undying gratitude to him. It is perfect, and probably better and lighter than the plywood parts I intended to use. 

Anyway, the handle was finished within the hour of the main unit arriving, and it weighs under 1.5 ounces. I plan to fly it next week, ASAP! All I had to do is enlarge the holes on one side to fit 4-40 bolts and chamfer the holes for the flat head screws, then tap the other side for the screws. The slow part was adding the safety thong! And he did have a hole for that in the design.

Here it ready to go!

Wow that is really cool!  Way to go Howard!!

[Jason Greer]

Howard is awesome. A few months ago I asked him how he liked the Logarithmic flap horn he was using. A few days later, I had a package waiting for me when I got home from work. It contained a few of the critical pieces required to make the horn. I was blown away by his generosity to go out of his way to do that. THANK YOU!!  If I'm able to make it to the Nats this year, ice cream is on me at Dairy Queen!

[Larry Renger]

Roger, that! It would be very interesting to have one to pass around and try out. It should be possible to just remove the clips from a TED Handle and plug the lines and clips onto a LARRY Expo Handle, no? Maybe not what one would want to do the weekend before a contest, but otherwise, sure...perhaps use an older model, for sure. Maybe we could get PW to try one out on one of his B-17 stunters?      Steve

Yes, neutral is neutral

[Larry Renger]

For me, the minimum spacing of the handle is still a bit wide, so I adjusted the design for 1/2" less minimum spacing. With a laser cutter, Eric should be easily able to make whatever range of spacing's are desireable.

The real hangup is how to get the links produced in an economical manner. Water jet has been suggested, and steel cuts as easily as Aluminum with that process. Anyone with a short run source at liveable prices? Or another inexpensive process? How much might stamping press tooling cost?

How are the Fancher handle metal parts made? 

It would be great if this concept could be tried out by a variety of modelers without breaking the bank.

Of course the dedicated experimenter can make the whole thing by hand with a jewelers saw, coping saw and hand drill, but let's get real. 

[Howard Rush]

"Reality trump theory...

You realize that this combination of words will get this thread zillilons of Google hits.

[proparc]

You realize that this combination of words will get this thread zillilons of Google hits.

Reality Trump Theory Hillary Deadpool.

[Mark Knoepfle]

It would be great if this concept could be tried out by a variety of modelers without breaking the bank.

Step one would be to get Mr. Rush to share his stl file or files. Printing is cheap depending on where you go. I have kilos of PLA, ABS and nylon waiting to be turned into useful things. I might even be talked into printing a small run. What did you (Mr. Rush) print the handle with? Looks like 50% honeycomb infill, 2-3 layers top and bottom with 3 perimeters as a guess. I can't tell the material without having the part in my hand (and some acetone nearby). 

The metal parts can be done pretty cheaply if you buy a hundred sets at a time. I have a friend that sells pancake dies. He has them laser cut and the cutter supplies the steel. I will talk with him this weekend.

Mark

[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?