Tony's EZ: Long nose

[tonyslongez]

here are the drawings that where supposed to go with my last post

 

Tony

[tonyslongez]

Here is the final for the nosegear trunion the bearing on top of the trunion is a bronze bearing or you can use needle bearings.

 

The bottom view you can see the other bronze bushing that is pressed into the top of the trunion this bearing will support the top of our steering rod

 

The fork is moved to the side for clarity

 

Also the trunion has the Jack whilhemson preloaded bearings fitted into it so keep those if you do this mod

[tonyslongez]

Here is the trunion with needle bearings. I will still have to press in a bronze bushing in the center of the trunion for the steering rod

 

This setup will require a little more machining as I'll have to countersink the steal bearing washer but it may add some longevity.

 

Tony

[tonyslongez]

oops getting tired its 3:30am time to go to bed here are the pics

[tonyslongez]

Here is the complete nose gear assembly.

 

I could use needle bearings down by the fork but dirt and grime will be an issue. I'll stick with the standard brass or bronze bushings.

 

That's it.!!!!!!!!

 

The whole assembly will be raked back a few degrees (A little math there) so that most of the load will go into the whilhemson lift, it has a spring built into it that will provide considerable dampning. I'm not sure what the weight is going to be but I'm hoping to be lighter than the stock nosegear assembly, at the worst it MAY be a pound or two heavier

 

Any questions????

 

No Yes Maybe

[Marc Zeitlin]

I could use needle bearings down by the fork but dirt and grime will be an issue.

The whole assembly will be raked back a few degrees (A little math there) so that most of the load will go into the whilhemson lift, it has a spring built into it that will provide considerable dampning. I'm not sure what the weight is going to be but I'm hoping to be lighter than the stock nosegear assembly, at the worst it MAY be a pound or two heavier

 

Any questions????

1) The wheel itself already used tapered roller bearings, and they take at least as much of a beating as the rotating bearings you're looking at. Dirt and Grime is not an issue if you use sealed bearings. Why would this be a special case?

 

2) A backward rake angle will destabilize the system. You need rake and trail (See any motorcycle fork geometry) for stability. You used to have a "L.E./COZY" style casting to hold the nose gear - you've gone away from that , so you've lost any trail you might have had. Take a look at any straight gear nosewheel - they're angled forward (wheel steering axis contacts the ground AHEAD of the tire contact patch - NOT behind it). Why did you change from what probably could have been a stable system to an unstable one?

 

3) Springs do not provide "damping" - damping is an ABSORBTION of energy, not a transmission of it from one form (kinetic) to another (potential). There is no damping mechanism in the Wilhelmson gear (I know, I have one).

 

4) You have no "shimmy damper" that I can see. With a very small diameter rod providing the steering force from the top to the bottom of the strut, you have a system that is very torsionally compliant. Without shimmy dampening right at the wheel, with high compliance (low stiffness), and especially with an unstable geometry, you will be susceptible to vicious shimmy in this system.

 

5) Assuming that you're using a 3D solid modeler, you should be able to calculate the weight of the system easily, by assigning materials to each part and asking for material properties. Are you not using a modeler that can calculate weights automatically?

 

6) In your original design, you were using a steering tiller - what happened to that idea that made you switch to using the rudder pedals?

 

7) What will happen if you partially extend the gear 1/2 way (to move the plane around with no weight in it on the ground), the wheel goes off to one side, and then you attempt to fully extend the gear without straightening the wheel? Will the engagement mechanism engage with a 90 degree wheel angle? Can you rotate the wheel 90 degrees sideways when the engagement mechanism isn't engaged to facilitate ground movement?

 

8) With the gear fully extended and the engagement mechanism engaged, you state that you have a 43 degree rotation angle capability. This will increase the turning radius from the stock 98" to about 135 - 140". Not a real big deal, but not as tight as before. You understand that you are giving up some ground handling capability here, right?

 

9) The dual gas springs (or equivalent) that you plan to use between the rudder pedals and the steering mechanism introduce another point of compliance into an already very compliant system. This greatly complicates the vibration modes of the system, as well as substantially lowering the vibration frequencies of the system (and increasing the possible amplitude of vibration).

 

10) I don't see any modifications to react the huge side loads that will be developed when steering at high speeds - since it's not possible for the system to ONLY castor (the gas springs are always engaged), there is the possibility that with the wheel off center, or in a crabbed landing, there will be LARGE forces that will be reacted into the gear strut and the NG-30's. How will your system deal with these loads, that a standard system never sees?

 

There might have been more, but I can't recall off the top of my head. Thanks for the opportunity to review your design - it's very interesting.

[tonyslongez]

Marc thanks for your reply

 

 

1) The wheel itself already used tapered roller bearings, and they take at least as much of a beating as the rotating bearings you're looking at. Dirt and Grime is not an issue if you use sealed bearings. Why would this be a special case?

The needlle bearings I was referring to, where for the area between the top of the fork and the strut not the wheel. Sorry for the confusion.

 

2) A backward rake angle will destabilize the system. You need rake and trail (See any motorcycle fork geometry) for stability. You used to have a "L.E./COZY" style casting to hold the nose gear - you've gone away from that , so you've lost any trail you might have had. Take a look at any straight gear nosewheel - they're angled forward (wheel steering axis contacts the ground AHEAD of the tire contact patch - NOT behind it). Why did you change from what probably could have been a stable system to an unstable one?

Marc, not sure why it matters what style of casting is holding the nose gear? How does it know what is holding the nose gear (what part of the nose gear are you referring to)? I thought that if I kept the rake back slightly mimmicking the stock strut I could keep it stable by putting the wheel in some kind of trail but if I'm wrong I'll move it forward a bit no problem.

 

3) Springs do not provide "damping" - damping is an ABSORBTION of energy, not a transmission of it from one form (kinetic) to another (potential). There is no damping mechanism in the Wilhelmson gear (I know, I have one).

I agree there is no dampning in the Wilhemson lift, but there is a spring and I believe I have a solution for the damping issue.

 

4) You have no "shimmy damper" that I can see. With a very small diameter rod providing the steering force from the top to the bottom of the strut, you have a system that is very torsionally compliant. Without shimmy dampening right at the wheel, with high compliance (low stiffness), and especially with an unstable geometry, you will be susceptible to vicious shimmy in this system.

 

The rod is actually .500 thick but could be as much as .750 4130 tube. I can add a shimmy damper at the wheel fork. No problem I'll draw it in tonight.

 

) Assuming that you're using a 3D solid modeler, you should be able to calculate the weight of the system easily, by assigning materials to each part and asking for material properties. Are you not using a modeler that can calculate weights automatically?

Yes I believe that I have that ability in Rhino and I might be able to in CAD jsut haven't taken the time to find out where it is in the program haven't needed to until now.

 

6) In your original design, you were using a steering tiller - what happened to that idea that made you switch to using the rudder pedals?

Well someone mentioned not wanting to have to take their hands off of the throttle or stick to steer so I just used the gas strut idea. I can still use the steering tiller, it's a simple system to incorporate.

 

7) What will happen if you partially extend the gear 1/2 way (to move the plane around with no weight in it on the ground), the wheel goes off to one side, and then you attempt to fully extend the gear without straightening the wheel? Will the engagement mechanism engage with a 90 degree wheel angle? Can you rotate the wheel 90 degrees sideways when the engagement mechanism isn't engaged to facilitate ground movement?

 

That's a good one Marc. O.k, 1/2 way the wheel goes off to one side, YES

once the steering fork has cleared NG30 you will be able to move the wheel. The steering fork will only goes as far as the stops I'll try to demonstrate that in a drawing for you, it's hard to explain what I mean without a pic (I'm at work)

but yes I do believe you will be able to that with no problem but it won't be 90deg obviously because it isn't castering or at least this design isn't. I can always go back to the spring steering which will do just what you are asking.

 

 

 

8) With the gear fully extended and the engagement mechanism engaged, you state that you have a 43 degree rotation angle capability. This will increase the turning radius from the stock 98" to about 135 - 140". Not a real big deal, but not as tight as before. You understand that you are giving up some ground handling capability here, right?

Yes, but like I said as well, I can get more throw with different bellcrank ratios

 

9) The dual gas springs (or equivalent) that you plan to use between the rudder pedals and the steering mechanism introduce another point of compliance into an already very compliant system. This greatly complicates the vibration modes of the system, as well as substantially lowering the vibration frequencies of the system (and increasing the possible amplitude of vibration).

O.k. well lets take care of that with the shimmy damper

 

10) I don't see any modifications to react the huge side loads that will be developed when steering at high speeds - since it's not possible for the system to ONLY castor (the gas springs are always engaged), there is the possibility that with the wheel off center, or in a crabbed landing, there will be LARGE forces that will be reacted into the gear strut and the NG-30's. How will your system deal with these loads, that a standard system never sees?

 

Well there is no doubt more to consider in the overal design of the NG-30 if I stay with this and not use the other design with more of a steerable caster. I have no doubt there will be more fine tunning to make it more user friendly but I have demonstrated that it is in fact possible the main thing in my design was to eliminate the steering scissors normally associated with SNG's. I also have another design for damping that is intersting I'll post it tonight and I would appreciate more feedback on that as well Marc.

 

Tony

[Marc Zeitlin]

The needlle bearings I was referring to, where for the area between the top of the fork and the strut not the wheel. Sorry for the confusion.

I realize that - I was just saying that if it is OK to use tapered rollers in the wheel axle, then it should be OK to use them in your assembly as well, since they're no more likely to get exposed to dirt/grime there than at the axle.

 

Marc, not sure why it matters what style of casting is holding the nose gear? How does it know what is holding the nose gear (what part of the nose gear are you referring to)?

It's not a question of the "style" of casting, it's a question of the geometry of the steering axis vs. the wheel axle position. On a motorcycle (or car, for that matter), if you look at the steering axis (or the kingpin angle on the car), it's ALWAYS tilted backward, meaning that the TOP of the rotation axis if further to the rear than the bottom of the rotation axis. Also, where that axis hits the ground MUST be in front of the center of the contact patch of the tire.

 

Since you have removed the "trail" in the casting (you've put the axle directly in line with the steering axis), if you put a negative rake angle on the system, to mimic the angle of the stock gear strut, you will end up with the steering axis hitting the ground BEHIND the center of the tire contact patch. This is unstable. It's like trying to drive your car backwards at 90 mph - any tiny perturbation, and you're off in the weeds with a hard-over wheel, especially since you won't have "hard" steering connection - just the gas-springs.

 

I thought that if I kept the rake back slightly mimmicking the stock strut I could keep it stable by putting the wheel in some kind of trail but if I'm wrong I'll move it forward a bit no problem.

If you put trail back in, that will help by getting the contact patch behind the point where the steering axis hits the ground, but you still don't want the steering axis angle to be negative (bottom further aft than the top). For stability reasons, the steering axis should be tilted back at the top, as described above for motorcycles, cars, and steerable nose gear on aircraft.

 

Yes I believe that I have that ability in Rhino and I might be able to in CAD jsut haven't taken the time to find out where it is in the program haven't needed to until now.

Yes, Rhino has the ability to do volume calcs, and knowing the density, you get weight.

[tonyslongez]

New wheel fork.

[JLKnolla]

Tony,

 

Attached is a clean PDF top and side view based on your long-nose mod. PM me with e-mail Addy for a DXF.

 

Let me know if you need anything else.

 

John

Super-EZ -Clean.pdf

[tonyslongez]

JL

 

Thanks alot buddy looks great.

 

That nose is perfect. (At least for me anyway)

 

 

Thanks

Tony

[Waiter]

The line art looks good,

 

HOWEVER, before you commit to foam and glass, double check the geometry when the plane is parked on its nose. It appears that it will park right on the nose tip.

 

Waiter

[JLKnolla]

Waiter has a good point reminding everone this is line art based on a tracing of the original EZ 3-view and is most certainly not in its' current form "engineering quality".

 

That said, the contact patch is about 6" aft of the nose tip.

[Witch Dr.]

Marc.

 

I have been following this thread and reading your posts with great interest. With that said I have one question. Did they teach you at MIT how to solve problems or merely identify them. I have watched you take every part of this nose gear and rip it to shreds in engineering speak. Yet you have offered very little in the way of advice to help solve the problems you have so readily found. Obviously you have a great deal of knowledge but you seem to be very stingy with help .

 

Witch Dr.

[Chairboy]

Marc.

 

I have been following this thread and reading your posts with great interest. With that said I have one question. Did they teach you at MIT how to solve problems or merely identify them. I have watched you take every part of this nose gear and rip it to shreds in engineering speak. Yet you have offered very little in the way of advice to help solve the problems you have so readily found. Obviously you have a great deal of knowledge but you seem to be very stingy with help .

 

Witch Dr.

Witch Dr, this type of stuff needs the most critical questions ever. When the design is solid, even the meannest critic won't be able to say anything!.

 

I look forward to seeing Tony's tests, and best of luck to him!

 

(edit, misread the poster id, changed)

[tonyslongez]

witch Dr.

Chairboy

 

Thanks for the support. I will have the final pieces back from the waterjet cutter this week, once fully assembled I will post actuall pictures of the install and hopefully a small video clip of the gear in action.

[Marc Zeitlin]

....Did they teach you at MIT how to solve problems or merely identify them.

Neither. They taught me how to learn and the basics of engineering. Vince, I was going to write: "did you study 'Personnel Management' because you were incapable of learning a profession that required actual talent?", but I decided that insulting you back would be lowering myself to your level, so I didn't. You wanna start this conversation over again, without the insults? Or at least in private, if you'd like to insult me? My email address is at the bottom of every post I make - feel free to use it to communicate with me directly.

 

I have watched you take every part of this nose gear and rip it to shreds in engineering speak.

No, actually, "rip it to shreds" is layman's speak. In engineering speak, I performed a design review and gave critical feedback. Engineers do this all the time in design reviews - that's what the design reviews are for.

 

Or was your English structure poor, and did you mean: "You used engineering speak to rip it to shreds"? In which case, I would respond that given that Tony is performing engineering to design his gear, and since he will need to use engineering tools to determine the quality/validity of his design, engineering speak would be the appropriate language in which to provide the feedback.

 

When a design has serious defects that will lead to safety issues, "rip it to shreds" is the appropriate path. Or would you rather that I said "hey, go for it - maybe it'll work!"?

 

Yet you have offered very little in the way of advice to help solve the problems you have so readily found. Obviously you have a great deal of knowledge but you seem to be very stingy with help.

What makes you think that just because I can recognize an issue, I can come up with a solution for it quickly enough to make it worth my time and effort to do so?

 

You have been watching my responses on this forum for all of 3 months - that's approximately 2.2% of the time that I've been involved with canard aircraft (11.5 years, for the mathematically challenged). If you were a member of the COZY mailing list, the canard-aviators mailing list, or this forum for more than just 3 months, you'd have seen that I've solved many issues for people and assisted them greatly. I am currently assisting one forum member with a major design change that he's implementing (and due to the amount of time involved, he's paying for it, too).

 

Tony asked for feedback and comments - I gave them. Hopefully he'll be able to use them to refine his design and make it work well.

 

If you don't understand the concept of an engineering design review, Vince, maybe you should refrain from commenting.

[Witch Dr.]

Marc

 

LOL:) :) :)

 

Now I know what it's like to poke a badger with a realy short stick.

[tonyslongez]

Marc

 

Did you see the last rendering on this post? Was that what you where reffering to for the rake and trail? I haven't finished the rendering for the damping but you are either going to laugh or think it is a good idea. I'm going to hang it out there anyway. I'm a glutton for punishment.

Also I don't think that I/you /we, will be able to retract the nose gear half way as I intended to do earlier in the rendering. I think it will compromise the NG30. I've seen a few guys with small dollys under the nose to move the plane around in the hanger. I think I'm willing to give that up for steering. But I may be able to simplify the other design to work but for now this looks like the most practical retrofit. I want to be able to just retrofit this into any long Ez or Varie. without alot of fuss. I have to see if Pazmany has the side load formulas. I'll try come up with a way to use the existing NG30 to handle those loads without alot of added weight, give me a day or two to get the drawing together.

 

Tony

[Marc Zeitlin]

Did you see the last rendering on this post? Was that what you where reffering to for the rake and trail?

Sort of - you added trail by moving the axle (and hence the tire contact patch) behind the point where the steering axis intersects the ground, but your "rake" angle is still zero, since the steering axis is vertical. That's not necessarily a bad thing - there are many parameters that intereract here - some aircraft have essentially vertical nose gear struts (and hence steering axes). However, you were talking about angling the strut rearward, like the standard L.E. strut - this would give a NEGATIVE rake angle and steering axis, and that's NOT a good thing.

[tonyslongez]

O.k

 

Here we go

 

What you are looking at is the damping portion of my gear the shock is from FOX Racing. These shocks are very small and are fully adjustable, they are used primarilly on pocket bikes they will not bottom out, (at least if your 200+lbs and jump the thing about 3ft in the air it won't bottom out.) You can get these from FOX Racing, custom fit to your needs. The drawing of the shock is scale. What I'm trying to accomplish is to keep everything within NG30, if I can keep the shock position where it is that will be easy to accomplish.

 

The needle bearings (RED) will allow the steering fork to rotate easily under the loads of damping. I drew the shock tower a little high so the shoulder under the needle bearings won't necessarily be there. The steering rod moves up and down inside the steering fork (Gold). I can steer at all times because the rod has a portion of its radius milled flat, this flat spot is just slightly longer than the travel of the shock which in this case is about (2") that length can be adjusted if I need more travel.

 

The wheel fork is attached to a larger diameter bar 1.25in dia than the steering rod itself this larger bar is supported with 2 oilite bearings top and bottom for about 4in total. that bar will translate the impact loads into the steering rod which in turn will be dampend out by the shock. the strut is attached to the top of the lower bar assembly. about (3in")

 

I'm sure this won't be the final design the trunion isn't very machine friendly.

 

Tony

[tonyslongez]

The other shock tower that I have planned will hold the steering fork in place and not allow it to move upward during damping. Obviously that is not possible with this particular shock tower. I'll try and have that finallized this week.

 

Tony

[tonyslongez]

I think this will be close to the final design for damping. I decided to keep the spacer that is sitting over the steering fork it is housing the needle bearings and an oilite bushing. I have some more work to do on the steering fork obviously but that is easy to fix. All of this will fit inside the NG30. I really want it to be retrofit. Now how do I solve for the side load issues? Marc if your watching do you have any idea what type of loads are on the NG30's now? Can I solve for the extra loads with a few well placed halfround bulkheads or implement Carbon/Kevlar onto the new NG30, What if I made them out of 1/4in birch with a carbon layup?

 

 

 

(you can't say I don't use my imagination)

[Marc Zeitlin]

.... Now how do I solve for the side load issues? Marc if your watching do you have any idea what type of loads are on the NG30's now?

Side loads on the wheel will produce a twisting of the NG-30's. One side will try to go up, and the other will try to go down. In NORMAL use, where the nose gear castors, the side loads, and hence twisting of the NG-30's, is extremely low. With the shimmy damper set to provide a maximum side force of approximately 4 lb (what the COZY plans call for) and a gear strut moment arm of about 2.5 ft., the maximum torque that could be applied to the NG-30 torque box is about 10 ft-lb. Since the NG-30's are about 4" apart, you'll have a force of about 30 lb vertically up on one side, and 30 lb. vertically down on the other. Not much.

 

The only times that I've heard of NG-30's breaking (and the only time MINE broke) is during extraordinary circumstances, like taxiing through a pothole or landing with one brake locked (my situation). These put enormous fixed loads on the gear/NG-30's that they weren't designed to withstand.

 

Now, with fixed steering (especially touching down at 120 mph with the nose gear cocked 45 degrees to one side, as would be the case in a hard crosswind landing while using maximum rudder), a coefficient of friction of the tire on the ground of 0.8, and a couple hundred lb. of weight on the nose gear, with a "G" load of 2 in a hard nose slapdown, we come up with nose wheel side forces on the order of 225 lb., or about 60 times as high as the normal maximum loads.

 

All rough orders of magnitude, but I think you can see my concern.

 

Can I solve for the extra loads with a few well placed halfround bulkheads or implement Carbon/Kevlar onto the new NG30, What if I made them out of 1/4in birch with a carbon layup?

strengthening and/or stiffening the NG-30's certainly can't hurt, but if you look a the pics on my web page:

 

http://www.cozybuilders.org/2004_Western_Trip/2004_Western_Trip_day_06.htm

 

You can see that there are a number of things going on. First of all, you want to raise the "level" portion of the NG-30's so that there's more "meat" vertically. Second, you want to eliminate the "corner", where you can see the tear began - any sharp corner is a stress concentration - this should be a large radius. Third, you can see that a large part of the NG-30 structure ripped out of the nose and tore out a part of F-22 - strengthening the NG-30's will only guarantee more damage to the rest of the structure when they rip out intact.

 

Extra ring bulkheads MAY help, as would spreading the NG-30's much farther apart and using a wider pivot structure - you want to attempt to transfer the loads into the nose further out. You'd probably have to increase the strength of the internal nose floor and walls to take the loads, as well.

 

(you can't say I don't use my imagination)

Nope - can't say that.

[tonyslongez]

Marc

 

The only times that I've heard of NG-30's breaking (and the only time MINE broke) is during extraordinary circumstances, like taxiing through a pothole or landing with one brake locked (my situation). These put enormous fixed loads on the gear/NG-30's that they weren't designed to withstand.

That is unfortunate that happened to your Cozy. Since I started building this Long Ez I thought the NG30 was a weak link in the nose. This won't make you feel any better but I saw the same thing happen to a guy in a Long Ez at Sun N Fun a couple of years ago do the exact same thing only he hit a pothole. Don't we think that NG30 should be able to with stand more trauma than taxing thru a pothole? I mean not a pothole that is going swallow your airplane but one that is moderate in size. I'm all for building lite but NG30 IMO should be birch not foam. I think your out come would've been less severe.

I've laid up some birch carbon pieces before and that stuff is harder than my head:D I understand that it's suppose to yield to prevent further damage but my problem with that thinking is no matter when or how it fails it does substantial damage. I can't imagine I could make NG30 so strong that the entire nose and floor would fail before it did. But I can imagine making it strong enough to handle a moderate pothole or in your case a stuck breeak

 

Now, with fixed steering (especially touching down at 120 mph with the nose gear cocked 45 degrees to one side, as would be the case in a hard crosswind landing while using maximum rudder), a coefficient of friction of the tire on the ground of 0.8, and a couple hundred lb. of weight on the nose gear, with a "G" load of 2 in a hard nose slapdown, we come up with nose wheel side forces on the order of 225 lb., or about 60 times as high as the normal maximum loads.

 

O.K. but look what happens if we slap the nose down with our current system it is going to shimmy violently and has shown in the past, at least for the Longs, to break the caster. If we have a bad landing the nose gear is going to break period. I mean look at the thing it's so flimsy, (Lite) yes, but flimsy at best. I think it could absolutely stand to be beefed up a little. I don't want to add 50lbs of glass and carbon but maybe 2.5lbs could be strategically placed in and around the area to handle some off roading at Oshkosh. How about if I just layup the whole nose in carbon (in and out) then I would have to rip off half of the fuselage in order for it to fail and if that happens we can call it a CRASH:D .

 

You can see that there are a number of things going on. First of all, you want to raise the "level" portion of the NG-30's so that there's more "meat" vertically. Second, you want to eliminate the "corner", where you can see the tear began - any sharp corner is a stress concentration - this should be a large radius. Third, you can see that a large part of the NG-30 structure ripped out of the nose and tore out a part of F-22 - strengthening the NG-30's will only guarantee more damage to the rest of the structure when they rip out intact.

 

Extra ring bulkheads MAY help, as would spreading the NG-30's much farther apart and using a wider pivot structure - you want to attempt to transfer the loads into the nose further out. You'd probably have to increase the strength of the internal nose floor and walls to take the loads, as well.

I can do all of that.

 

 

The other thing is, if I land with max rudder input and the side load is say 225lbs or so. The wheel is going to snap forward because the gas struts are only about 10lbs of preasure they can't hold the wheel in that position but they are strong enough to steer the wheel. Does that make sense:rolleyes:

 

BTW Marc that was a very helpful post thanks.

 

Tony