Helicycle Hatchery

I had to fabricate a pitch gauge. Templates were provided which I traced to a piece of maple. I rasped and filed till it was a close fit. The most important is to get the chord of the airfoil right on the center both the leading and trailing edge.

This gauge will be used to accurately set my pitch links so that each blade has the same positive and negative pitch.

Stan
 

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yeah, Stan, I tend to agree with your analysis. The blades will always try to return to flat pitch, so the weights are set to oppose that moment of force.
Propellers, also can require chinese weights. The Carter Copter prop uses them and there is some info on this page:
http://www.cartercopters.com/propeller_system.html
 
Heres is something I find VERY interesting. Actual measurement of pitch change as the delta hinge is flapped.

The first picture shows the delta hinge incorporated into this tail rotor like many helicopters have. Why is this so interesting to me?

Just like the main rotor, the tail rotor has a flapping hinge.

The top of the tailrotor is moving as fast as the bottom of the rotor of course...but it has the forward airspeed subtracted from its rotational speed whereas the bottom of the tail rotor has the forward airspeed added to it.

This causes the blade to flap. This is all fine except the delta hinge reduces the amount of flapping substantially by reducing pitch to the bottom advancing half of the disc, and adding pitch to the retreating top half of the disc. This reduced range of flapping made possible by the delta hinge allows the tail rotor to be built closer to the gearbox. Also...the front edge of the rotor doesnt have much clearance to the frame.


However, you can see the hinge flaps at an angle instead of perpendicular to the axle. As the blade flaps out away from the tailboom , this hinge automatically increases pitch to that blade...and likewise the opposite blade is flapping in and pitch is being pulled out from it.

This is all fine and good except I like to see actualy measurements of this action. The 2nd picture shows the pitch angle block with my angle gauge sitting on it ready to give me some numbers.

The 3rd picture shows the blade flapped towards the tail boom and the angle reading is 1 degree.

The last picture shows the blade flapped out away from the tail boom and its reading 7 degrees.

So the delta hinge is varying the pitch of each blade 6 degrees as it goes through its full allowed range of flapping. I measured this flapping at around 6 inches total movement at the tips.....so without this delta hinge joint...that tail rotor blade would be flapping substantially more than a 6 inch arc.

I find this very interesting.


Stan
 

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So how many people would find it all too much, and give up you think? It just shows why helicopters are so expensive. They have to be complicated and acurate to work. You are an inspiration to us all.
 
I'd try to hire Stan to "help". I believe he is the type of guy that when his is finished, he would let you bring your kit to his shop & help you with your build.

That is if he's not out flying !

Of course , you might have to help carry some stairs out from time to time.

Stan's stairshop & Helicycle assistance. Make your arrangements NOW !

Let me know if this needs to be deleted......some might believe this "ad" .
 
Perfect will do

Perfect will do

Years ago I had the privelege of learning residential framing from a guy here in Utah. His business moto was simple, "Perfect will do"

I think this is Stan's moto also..."Stairs (and helicycles) with a twist, perfect will do!"

I don't think you will find a flaw in the craftmanship of anything Stan does...genious, artist, perfectionist, teacher, mentor and I would add gentlemen.

Stan might consider this excessive and unnecessary praise, but the fact of the matter is that it is all true!

Stan, keep up the perfection, you are an inspiration to us all.

Stay safe.
 
Tonight I drilled a bunch of allen head bolts for the safety wire. Part of the conforming to the 51% rule! I safety wired the tail rotor bolts as I wont be taking it apart again for a long time.

The slider collar was drilled on the corners for safety wire also. These wires wont be installed until later. After all this is prepped...the tail rotor gearbox, driveshaft, and transmission all comes out for painting. The top fuel tank has to be installed before I reinstall the transmission.

Chipping away one hour at a time!


Stan
 

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Not all goes according to Hoyle.....I was drilling some 45 degree safety wire holes...when my 1/16 inch bit broke off.:eek:

It had just started to exit when it broke...I thought I was being careful. I could not get to it without taking the tail rotor off...and sliding this off the shaft.

I ended grounding a small nail down to a 1/16 inch...ground the end flat and punched it back through.


Stan
 

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I HATE when that happens !
 
OK, I am not happy with some previously completed work. My hood bearing is supposed to be shimmed till its exactly square with the rotor shaft, which I posted pictures of earlier..with the feeler gauge checking so as its within 0.005 inches. I had mine within 0.002 inches. It was checked off and done correctly...but everytime I walk by...the big gap that had to be shimmed catches my eye everytime. Its ONLY cosmetic...but hey...I dont like it.

Also...study the rubber seal on the top of this bearing. The lip of this seal JUST, And I mean JUST sits on the turned section where its suppose to seal the grease from flinging out. It cant be seen in the picture or by eye...but if you take your fingernail and lift the seal...you can just see the turned section its riding on. If I fit this hood bearing lower...the seal of that bearing will come down with it and all will look better.

The rotor shaft has a built-in tilt of 1.5 to 2 degrees. This is part of the reason for the gap to be shimmed. Like I said...its only cosmetic, but I want to improve this.


This hood bearing has no vertical load, so any material removal doesnt hurt it.

I scribe wood all the time to fit...so why not aluminum?

The pictures show the gap....shows the scribing operation, and then the line I want to remove the aluminum to. I am using my dremel tool to go almost half way around to remove the unwanted material.

I am going out to finish this operation today....and I will post pictures of this hood bearing plate fitting much closer....still needing I am sure a thin shim here and there...but not a stack of two regular washers worth on the high side and touching on the opposite side.

STAY TUNED and judge for yourself how this turns out. UH oh,,,I better not screw this up!


Stan
 

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Wouldn't it be more accurate if you mount it in a milling machine?. Also apply grease to the inside , [where the spring is] of a seal before fitting.
 
Stan, you could have just slipped an O-ring down aroung that gap and it would have looked good. they make all types so you could get one that would be chemical/weather proof and it would last a long time. or if you have a lathe you could have made an aluminum sleeve.
 
earthbnd- My "milling" machine is pictured here...a 14 inch cutoff saw, and a file. It worked and the unsightly gap is gone. I am very satisfied with the results! Hey, I dont own a milling machine and have said I am not a machinist anyway. Of course a milling machine set up correctly could have done this perfectly, but look real close ...the before shot in picture #3 and the after shot in picture #4. Like Frank Sinatras lyric in his song..."I did it my way". ha

Gyro- An O-ring would have raised the lip of the seal completely off the machined part where it has to ride on. The only way was to either scribe and grind the hood bearing bracket like I did....or.......take a hammer and a hard block of wood and beat down the flat part of the hood bracket. I didnt like the sound of that even though it would have lowered the bearing and oil seal where I wanted it to go.
Look at the last two pictures. The next to the last is before I scribed, ground, scribed and ground again.....notice the lip on the oil seal is not showing any of the machining where the lip should be running on.

The last picture is completed...you can see the tapered base fits the hood plate much nicer....no gaps that were two washers thick....the hood bearing is within 0.002 again....and also...look at the top lip in this last picuture...clearly an 1/8 of machining above the lip now. I could not stand that gap in the third picture even though it was just cosmetic.

I like it and can move on to my next adjustments.


Stan
 

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Attention to detail or....

Attention to detail or....

Stan,

Now that is either attention to detail or obsesive compulsive disorder:lol::lol:

Either way, it is very cool.:first:

Then again another way say obsesive compulsive is anal retentive!:D

After your "hospital visit" this past few days, maybe the doctor increased your rate of anal rententivism!!!:drum:

Keep it up and stay safe.
 
Stan, I did not mean to sandwich the o-ring but rather just slip in on and let it ride on the outside. with that gap you had on 1/3 of the flange would have grabbed in that area of the o-ring and not rode up.

Anyway you got it fixed and looks good.
 
Gyro- I see what you mean now. That would have been a solution. Thanks. Stan
 
Part of building this helicopter is trying to understand the mechanisms that make it fly. I have a techy question about the delta hinge. I enjoyed learning how this hinge reduces the amount the tail rotor has to flap,,and thus allows it to be closer to the frame. Totally have that clear in my head and this makes for good coffeshop discussion. However...I want to dig deeper into the math part of it.

The first picture shows the delta hinge. It has a 20 degree offset which you can see in the picture.

The 2nd picture is showing the angle gauge reading 7 degrees when the blade is flapped to the stop one way...and the 3rd picture shows it flapped to the other extreme...and reads 1 degree. So, that is an angle change for the pitch at 6 degrees.

I measured the high flap to low flap at the tip of the 42 inch diameter tail rotor at 6 inches. Taking the radius as 21 inches...I divided 6 by 21 and and toik the tangent of that to come up with 15.94 degrees of flapping.

Now.....my question. With this 20 degree offset angle....I am wanting to have my math coincide with the "roughly" 6 degrees of pitch change I measured with my gauge shown in the last two pictures.


If the delta hinge were 0 degrees...then any amount of flapping would not change the pitch. If the delta hinge were 90 degrees...then the amount of flapping would change the pitch the same amount.

The value for sine is 0 at 0 degrees and 1 and 90 degrees.

I took the sine of this delta hinge angle of 20 degrees which is 0.34202 and multiplied that times the 15.94 degree max flapping that my blade was measured at and came up with 5.45 degrees. For the accuracy of my measuring equipment....I feel I have the right formulae.

So, if I multiply the sine of the angle of the delta hinge times the flapping angle...am I correct is saying that this is the formulae for telling me the pitch change of the rotor blade? I strongly believe it is...but I am not a math wiz, so if someone such as Chuck can come on here and confirm or correct me...I would very much appreciate it!


Stan
 

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Close, Stan, but no cigar.

I think you might agree that should the delta-3 angle be 45º, the flap-pitch coupling is 1:1; that is, one degree of flap = one degree of pitch.

So, it’s the tangent of the delta-3 angle. For small angles, tangents and sins are nearly the same, making your pitch gage measurements come out pretty close.

The tangent of 20º is 0.364 and the sine is 0.342. Close enough for government work.
 

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